With a bit of Wintery weather moving in this week it was time to put some thought into the next steps for the LE mod. I disassembled the 2 408 ribs and the subskin from the LE and deburred the new holes. Then I used the file to remove a bit more material from the flanges on the modified 408 rib. THis is necessary not only for the clearance of the shop head of the rivet that goes into the last hole on both flanges, but also needs to clear the dimples that will get created in the subskin and the outer LE skin.
I also measured and marked the center lines on both rear rib flange extensions to check for rivet edge distance clearance. Only one rivet hole will drilled in each of these pieces, but before I do that I need to attach each one to the rib web (6 AN470 rivets each). Before I can do THAT I need to prime that entire rib. So it looks like some priming will be in order once the temps climb back up to above 55 degrees.
In the mean time I started drawing up the plans for making the necessary cuts to the subskin. I needed to use the 12 inch x 36.5 inch piece of .032 aluminum so I could make the correct bend to achieve the contour of the leading edge curve. However, since the subskin is basically nothing more than a mounting platform for the outer skin section that will slip over it, I don;t need to keep all of that metal on the subskin.
The big question now is how far to trim the subskin metal on both sides. I am currently evaluating exactly where I need to make the critical cuts in the subskin, and I pretty much have to get this right the first time. There is a lot to consider here, including stress points along the curvature of the leading edge, how many screw attach points and nut plates to use, and where each of them should be located. If I screw that up then I will get to start all over again, and may very likely also need to order a brand new LE skin and ribs, due to the potential to oversize the holes in the outer skin by having to re-drill through them several more times.
So needless to say I need to thoroughly think this through and very clearly understand exactly where to trim the metal on the top and bottom sides of the subskin, prior to trimming any of it away. As usual, pics showing how I am doing this will be more clear than describing it. The best way to describe it is that this is a bit of a multi-layered jigsaw puzzle, with an oddly shaped curve in the middle, where the inner and outer layers need to be trimmed very precisely, and the pieces are on the top and also on the bottom. Its a bit more complicated than your garden variety square access panel in a piece of flat aluminum, but the concepts are still the same.
KPR.
Thursday, April 27, 2017
Sunday, April 23, 2017
Counter sunk the Pitot Tube Mast and Checked out the LE from the Inside
Since I received the AN507 6R4 screws from ACS, I decided it was time to do the deed and countersink the mounting holes in the mast to accept the new screws. I had an opportunity to practice this a bit before going to town on the real thing by using the half inch of mast material that I cut off as described in my earlier posts. Some of my pics turned out really blurry so I won't show the close ups.
To countersink the mast mounting holes I did NOT use a microstop countersink tool, as this is next to impossible to use since you are countersinking a hole on a curved surface. Other builder sites have reported that it is almost impossible to get a totally good countersink on these mounting holes because of the curved surface of the mast.
So I did everything by hand by using 2 different deburring tools. I started by using my single flute deburring bit in my electric drill. I made sure that the deburring bit was angled in the same direction that the original hole was drilled, and that the bit was as square to the hole as I could get it. Once the countersink was started and I could not go any deeper with this tool, I switched to my larger 3 flute deburring tool that has a larger countersink bit on it.I removed a little material at a time, maybe only 3 light turns each time, as I got closer to the final depth for each screw. The last thing I wanted to do is make the countersink too large for the screw head. After countersinking each hole I would remount the new pitot tube into the mast and tighten down each screw to check the depth, and then carve out some more metal if necessary and do it all over again.
Practicing on the scrap piece of the mast helped, because that allowed me to get a feel for what it would take to get the right depth for each screw. Here are some pics of the tools used and the new screws think I have some more work to do on one of the forward holes, but the rest of them seem pretty good to me.
Next is the work on the LE. I removed all clecos attaching the LE skin to the Wing Spar flange, and then I removed all clecos attaching the rear LE rib flanges to the wing spar web. Note to self, remember to apply all these clecos from the rear (bottom) of the wing spar web, and NOT through the top or front of the web. When I attached the LE to the modified W408 rib it was already attached to the wing spar and I had mounted the clecos on the top or front side of the wing spar web. The goal for this removal was to remove the entire LE assembly from the wing spar, leaving ALL ribs and the subskin clecoed in place so I could inspect the new holes and clearance on the edge of the rib flange.
To do that I was faced with trying to figure out a way to remove 3 clecoes attaching the 408 rib from the wing spar web. I really had no other choice other than to remove the clecoes holding the LE skin to the 408 ribs again, but that would mean starting all over again, so I got creative and figured how to get my hand inside the lightening holes of both 408 ribs with the cleco pliers in hand, and then working the pliers with one hand by reversing the pliers to face the clecos, and feeling my way around in the blind until I new I had attached the pliers to each cleco. The clecoes are hidden from view so all of this has to be done by feel. I managed to get each one undone, but I really do not want to do that again. SO next time all LE attach clecoes will be inserted into the ribs from the rear (bottom) of the wing spar web.
With the fully assembled LE finally off the wing, I was able to check my handy work. Here are the pics of the top and bottom rib flanges where I had to trim away some of the rib flange to allow clearance for the shop head of the rivet that will go into the closest hole (where the cleco end is currently. At a galce it looks like the shop head of the rivet will clear the flange, but I need to make sure it will clear AND not rub against it, so I think I have just a bit more filing to do, but its real close:
This next pic is a bit bright due to my flash from the camera, but it does show some detail of the inside of the LE area that I have been working on:
You are looking at a close up of the bottom rib to LE skin flange with the LE laying on its side. You can see the area where I trimmed the rib flange for the clearance for the original rivet hole that will go through the outer skin and the sub skin only. (Last cleco on the right). The next cleco to the left is the new rivet hole that I drilled that will attach the outside LE skin, subskin, and rib flange (3 layers of metal). I can also see that I have at least the required 2xD edge distance, or in this case 1/4 of an inch from all sides of the flange (rear, outside edge, and inside bend radius).
The rib flange is sitting on top of the extended subskin, and the outer LE skin is sitting under the subskin.So with a little more filing I think I will have sufficient clearance for the shop head of that right-most rivet hole that normally would have gone through the final hole in the W709 rib, but since I am not using that rib any longer this is the change that I had to make.
After I get this clearance issue done I can start prepping the ribs and outside skin for primer, and then I have to rivet the rear rib flange additions to the web of the modified 408 rib (The six holes at the top of the above pic, plus the ones for the other side of the rib). Then I get to make even more critical measurements on the subskin so I can start trimming that up to its final form. Hopefully the pics provide a bit more clarity to my explanations about what I doing here. Getting there......
KPR.
To countersink the mast mounting holes I did NOT use a microstop countersink tool, as this is next to impossible to use since you are countersinking a hole on a curved surface. Other builder sites have reported that it is almost impossible to get a totally good countersink on these mounting holes because of the curved surface of the mast.
So I did everything by hand by using 2 different deburring tools. I started by using my single flute deburring bit in my electric drill. I made sure that the deburring bit was angled in the same direction that the original hole was drilled, and that the bit was as square to the hole as I could get it. Once the countersink was started and I could not go any deeper with this tool, I switched to my larger 3 flute deburring tool that has a larger countersink bit on it.I removed a little material at a time, maybe only 3 light turns each time, as I got closer to the final depth for each screw. The last thing I wanted to do is make the countersink too large for the screw head. After countersinking each hole I would remount the new pitot tube into the mast and tighten down each screw to check the depth, and then carve out some more metal if necessary and do it all over again.
Practicing on the scrap piece of the mast helped, because that allowed me to get a feel for what it would take to get the right depth for each screw. Here are some pics of the tools used and the new screws think I have some more work to do on one of the forward holes, but the rest of them seem pretty good to me.
Next is the work on the LE. I removed all clecos attaching the LE skin to the Wing Spar flange, and then I removed all clecos attaching the rear LE rib flanges to the wing spar web. Note to self, remember to apply all these clecos from the rear (bottom) of the wing spar web, and NOT through the top or front of the web. When I attached the LE to the modified W408 rib it was already attached to the wing spar and I had mounted the clecos on the top or front side of the wing spar web. The goal for this removal was to remove the entire LE assembly from the wing spar, leaving ALL ribs and the subskin clecoed in place so I could inspect the new holes and clearance on the edge of the rib flange.
To do that I was faced with trying to figure out a way to remove 3 clecoes attaching the 408 rib from the wing spar web. I really had no other choice other than to remove the clecoes holding the LE skin to the 408 ribs again, but that would mean starting all over again, so I got creative and figured how to get my hand inside the lightening holes of both 408 ribs with the cleco pliers in hand, and then working the pliers with one hand by reversing the pliers to face the clecos, and feeling my way around in the blind until I new I had attached the pliers to each cleco. The clecoes are hidden from view so all of this has to be done by feel. I managed to get each one undone, but I really do not want to do that again. SO next time all LE attach clecoes will be inserted into the ribs from the rear (bottom) of the wing spar web.
With the fully assembled LE finally off the wing, I was able to check my handy work. Here are the pics of the top and bottom rib flanges where I had to trim away some of the rib flange to allow clearance for the shop head of the rivet that will go into the closest hole (where the cleco end is currently. At a galce it looks like the shop head of the rivet will clear the flange, but I need to make sure it will clear AND not rub against it, so I think I have just a bit more filing to do, but its real close:
This next pic is a bit bright due to my flash from the camera, but it does show some detail of the inside of the LE area that I have been working on:
You are looking at a close up of the bottom rib to LE skin flange with the LE laying on its side. You can see the area where I trimmed the rib flange for the clearance for the original rivet hole that will go through the outer skin and the sub skin only. (Last cleco on the right). The next cleco to the left is the new rivet hole that I drilled that will attach the outside LE skin, subskin, and rib flange (3 layers of metal). I can also see that I have at least the required 2xD edge distance, or in this case 1/4 of an inch from all sides of the flange (rear, outside edge, and inside bend radius).
The rib flange is sitting on top of the extended subskin, and the outer LE skin is sitting under the subskin.So with a little more filing I think I will have sufficient clearance for the shop head of that right-most rivet hole that normally would have gone through the final hole in the W709 rib, but since I am not using that rib any longer this is the change that I had to make.
After I get this clearance issue done I can start prepping the ribs and outside skin for primer, and then I have to rivet the rear rib flange additions to the web of the modified 408 rib (The six holes at the top of the above pic, plus the ones for the other side of the rib). Then I get to make even more critical measurements on the subskin so I can start trimming that up to its final form. Hopefully the pics provide a bit more clarity to my explanations about what I doing here. Getting there......
KPR.
Received my order from ACS
Got my composite practice kit, AN 507 6R4 flush head screws for the pitot mast, and a few other sorted items. The one thing that I did not get yet, and I should ave paid more attention to the in stock/out of stock messages when I placed my order, is the Bob Archer Nav antenna. At my last check they indicated that it should be available by April 28. In the mean time I am preparing another order from Vans, and working on my order for the QB RV-8 fuselage.
I'm also waiting for a phone call from the trailer service place where I take my trailer to get ready for the annual trek to Airventure, which will be here before you know it. I had some water system issues to take care of and a couple of other things. At least the trailer brakes seem to be working - a major miracle as far as I am concerned, given the large number of infesting rabbits that have inundated my area for the past couple of years now. As soon as they get a hint of any wiring that has soy-based insulation, then they will chew it to bits. never thought I would say this, but I sure wish the foxes would reappear for a little while to get rid of these rabbits!
Anywhooo, back to the build. KPR.
I'm also waiting for a phone call from the trailer service place where I take my trailer to get ready for the annual trek to Airventure, which will be here before you know it. I had some water system issues to take care of and a couple of other things. At least the trailer brakes seem to be working - a major miracle as far as I am concerned, given the large number of infesting rabbits that have inundated my area for the past couple of years now. As soon as they get a hint of any wiring that has soy-based insulation, then they will chew it to bits. never thought I would say this, but I sure wish the foxes would reappear for a little while to get rid of these rabbits!
Anywhooo, back to the build. KPR.
Cleaning and Adjusting Shop Tools
Let this post serve as a reminder for those that are building to take some time every so often to refurbish, reset, realign, re-tighten, replace, repair, reassemble, or recondition all of the various tools you are using during the build. Especially if they have been sitting idle for long periods of time.
Spent the past couple of days cleaning, adjusting, and reconditioning various shop tools in preparation for upcoming build tasks. After being a bit surprised by the blade drift of my band saw when I trimmed down my pitot tube mast a few posts ago, I pulled out my instruction manual for my Ridgid BS14002 14 inch band saw and starting checking all the numerous adjustment points. I was a bit shocked to find that my blade tension, tracking, and guide settings were way off, loose, or just not correct. I have no idea how it got this way. I also realized it needed a good cleaning. I also think I need to replace the rubber tires that fit around each wheel with some urethane ones, since the rubber ones (stock) are starting to crack, and there are some reviews that indicate that the vibration associated with this particular saw can be solved by several modifications, including new urethane wheel tires.
I then set out to change the 80 grit sanding belt and corresponding sanding disk with new ones that I had purchased from Ace Hardware a long time ago.Theses are made with aluminum oxide. which, as I have posted long ago, is about the only type of sand paper that you want to use with aluminum to avoid corrosion. The sander also needed a thorough cleaning. The instructions to my sander said that to replace the disc you peel off the old one (had to use a paint scraper for that.) Then you have to "remove" the old glue residue, but they don't tell you how to do that. So I started with a razor blade, and that did not work well. Then I switched to mineral spirits, which softened the glue up a little but did nothing to remove it. Then I went to Acetone - same result. Then I remembered that I had to some goo gunk or something like that in a small squeeze can. So I tied that. This softened up the glue a bit more but also did not remove it very well.
Then I went back to the razor blade. The glue starting coming off, but not without a lot of effort by me. I finally got all the glue removed from the disc, and applied to new one - 80 grit just as before. I also have heavier and lighter grades in case those are ever needed - probably for some fiberglass work I am expecting.
After all that, my thumb and finger tips are tingling and won't stop - sure hope that goes away soon. That was just a little too much work to get rid of some glue. In hindsight maybe I should have stuck with the paint scraper. Trying to do this on a rotating and moving piece of metal is also not the safest thing in the world. Very easy to slip and really do some damage. Oh well, I guess its just the way of things.
The last item I worked on was my pneumatic paint shaker that I got from Harbor Freight a long time ago. I cleaned off the dirt and cobwebs and disassembled the oiler that came with it. Then I replaced all the teflon tape on the various fittings for the oiler, and reassembled them on the shaker. I then had to try to locate my instruction manual because I could not remember how much air pressure it was designed to use. I finally found it with the manuals for the two spray guns that I use - still sitting on my work bench.
I needed to verify that the shaker still works, because as I reported in my previous post, the next steps for my LE work include priming all of the LE ribs and skins, etc, prior to riveting them together. My Akzo Nobel Epoxy primer has been sitting in my garage for the past 3 years through the hot and cold. The primer was already at the end of its service life when I bought from ACS long ago (a sore subject with me to this day, but one without much of an alternative). The last time I used it was for the main wing ribs and rear wing spars. I opened up the can that contains the pigment, and noted that the liquid portion was sitting on the top, and all the pigment was separated and sitting on the bottom of the can. The hardener/catalyst in the other gallon can also appeared to be viable, and smelled just as bad as I remember it.
Anyway, since it has sat unused for so long I am not even sure that it is still viable, but I am willing to test it, since this stuff costs $200.00 a pop. If it still works to my satisfaction I will use it to prime the LE ribs and skins.
The shaker requires 50-70 psi to operate. So I put the can with the pigment in the shaker and starter 'er up. After about 4.5 minutes I checked the contents, and although there were alot of air bubbles, it seemed to mix the pigment OK. SO the next step it to try it out on some metal and see what happens.
Spent the past couple of days cleaning, adjusting, and reconditioning various shop tools in preparation for upcoming build tasks. After being a bit surprised by the blade drift of my band saw when I trimmed down my pitot tube mast a few posts ago, I pulled out my instruction manual for my Ridgid BS14002 14 inch band saw and starting checking all the numerous adjustment points. I was a bit shocked to find that my blade tension, tracking, and guide settings were way off, loose, or just not correct. I have no idea how it got this way. I also realized it needed a good cleaning. I also think I need to replace the rubber tires that fit around each wheel with some urethane ones, since the rubber ones (stock) are starting to crack, and there are some reviews that indicate that the vibration associated with this particular saw can be solved by several modifications, including new urethane wheel tires.
I then set out to change the 80 grit sanding belt and corresponding sanding disk with new ones that I had purchased from Ace Hardware a long time ago.Theses are made with aluminum oxide. which, as I have posted long ago, is about the only type of sand paper that you want to use with aluminum to avoid corrosion. The sander also needed a thorough cleaning. The instructions to my sander said that to replace the disc you peel off the old one (had to use a paint scraper for that.) Then you have to "remove" the old glue residue, but they don't tell you how to do that. So I started with a razor blade, and that did not work well. Then I switched to mineral spirits, which softened the glue up a little but did nothing to remove it. Then I went to Acetone - same result. Then I remembered that I had to some goo gunk or something like that in a small squeeze can. So I tied that. This softened up the glue a bit more but also did not remove it very well.
Then I went back to the razor blade. The glue starting coming off, but not without a lot of effort by me. I finally got all the glue removed from the disc, and applied to new one - 80 grit just as before. I also have heavier and lighter grades in case those are ever needed - probably for some fiberglass work I am expecting.
After all that, my thumb and finger tips are tingling and won't stop - sure hope that goes away soon. That was just a little too much work to get rid of some glue. In hindsight maybe I should have stuck with the paint scraper. Trying to do this on a rotating and moving piece of metal is also not the safest thing in the world. Very easy to slip and really do some damage. Oh well, I guess its just the way of things.
The last item I worked on was my pneumatic paint shaker that I got from Harbor Freight a long time ago. I cleaned off the dirt and cobwebs and disassembled the oiler that came with it. Then I replaced all the teflon tape on the various fittings for the oiler, and reassembled them on the shaker. I then had to try to locate my instruction manual because I could not remember how much air pressure it was designed to use. I finally found it with the manuals for the two spray guns that I use - still sitting on my work bench.
I needed to verify that the shaker still works, because as I reported in my previous post, the next steps for my LE work include priming all of the LE ribs and skins, etc, prior to riveting them together. My Akzo Nobel Epoxy primer has been sitting in my garage for the past 3 years through the hot and cold. The primer was already at the end of its service life when I bought from ACS long ago (a sore subject with me to this day, but one without much of an alternative). The last time I used it was for the main wing ribs and rear wing spars. I opened up the can that contains the pigment, and noted that the liquid portion was sitting on the top, and all the pigment was separated and sitting on the bottom of the can. The hardener/catalyst in the other gallon can also appeared to be viable, and smelled just as bad as I remember it.
Anyway, since it has sat unused for so long I am not even sure that it is still viable, but I am willing to test it, since this stuff costs $200.00 a pop. If it still works to my satisfaction I will use it to prime the LE ribs and skins.
The shaker requires 50-70 psi to operate. So I put the can with the pigment in the shaker and starter 'er up. After about 4.5 minutes I checked the contents, and although there were alot of air bubbles, it seemed to mix the pigment OK. SO the next step it to try it out on some metal and see what happens.
Thursday, April 20, 2017
New holes drilled in the LE skin and supplies coming from ACS
As a birthday present for myself I ordered a bunch of stuff from Aircraft Spruce the other day. Among the items is a composite practice kit and some bags of cabosil, flox, and micro, so I can start working on some fiberglass stuff. I also ordered a Bob Archer nav antenna for the left wing tip (Model 1), and some 1/4 inch long countersunk head cadmium plated 6/32 screws for the pitot tube/mast assembly. (Used to be tagged as AN 507, now has some mil spec number associated with it). I had some AN507 6R6 (3/8 inch) screws, but I think those are the ones needed for the electric trim mounting/service plate in the elevator, so I left them alone.
In the past couple of days I managed to mount and re-secure the left wing LE assembly to the Left wing spar. Before I could drill the new holes in the LE skin, the subskin, and the 408 rib, I needed to make sure that the entire LE assembly was attached just as it would be riveted to the wing, to ensure that the new holes end up in the correct location on the subskin and the 408 rib flange. Getting that beast secured onto the wing spar was no easy task. Lots of holes to line up and cleco in place, and needed to apply some added "pressure" here and there to get the holes to line up.
Then I did the deed. Marked each location with my hole punch and drilled two new #40 holes in the LE skin. Exciting stuff-not, I know, but much needed progress for me.
Each holes seemed to line up with the others OK - but the only time I will know for certain is when I actually rivet everything together. I seem to have this strange problem with keeping things in a straight line, even after I have measured and marked everything correctly. Must be a perception thing with my lovely progressive lense glasses. Anyway, the above pics are the top side adn bottom side holes.
Here is a pic with the LE all clecoed in place. Not shown are the clecoes attaching the rear rib flanges to the wing spar web. I started with those and then attached the LE skin to the wing spar flanges, after positioning the subskin in place and getting that all lined up with the LE rib flanges and the skin. What fun that was for the 12th time.Once its all together it looks pretty good.
I put clecoes in each of the new holes and felt for proper clearance with my fingers inside the "tunnel." Feels like I did everything right, and that the holes are in the right place in all 3 pieces of metal. Since the flanges all face away from the opening, I had to reach inside around the rib web and feel where the edges of the rib flange and the cleco were located. Not that this mattered much, since I knoew I had to remove the whole Le assembly anyway, but I wanted some sort of "immediate" confirmation that I had done this correctly.
Next steps
Leave all ribs, subskin, and LE skin attachements in place
Remove the clecoes holding the LE onto the wing spar
Remove the entire LE assembly, this time with the subskin still attached
Check all hole clearances visually, including the clearance for the shop head of the last hole (where I trimmed the 408 rib flange.
Disassemble the two 408 ribs and debur the new holes in all parts.
Trim any additional rib flange material as needed to ensure that the shop head of the rivet in that last hole will clear it.
Prep the modified 408 rib for primer and prime it.
Rivet on the two rear rib flange extensions to the modified 408 rib. (I could not do this long ago because I needed to prime the rib first - yet another reason why I stopped where I did.)
Re-attach the entire LE assembly to the wing spar (AGAIN!!)
Drill two more holes, this time match drilling the holes in each rear rib flange
Remove the entire LE assembly (AGAIN!)
Debur the two new rear rib flange holes
Disassemble the entire LE, prep and prime all LE parts, EXCEPT the subskin.
Determine precise measurements and locations for the subskin. A lot of the subskin material will be removed since it will not be needed. Only the portion that wraps around the LE and serves as the mounting flange for the modified outer LE skin needs to remain "as is." The rest gets cut away, leaving only about 1.5 inches over the top and bottom rib flanges of both 408 ribs.
Trim the subskin, prep and prime
Rivet the LE assembly together
Do the same madness for the right wing, starting with bending/forming the subskin for that side.
Wash, rinse repeat for the right wing.
Move on to the fuel tanks.
Till next time, KPR.
In the past couple of days I managed to mount and re-secure the left wing LE assembly to the Left wing spar. Before I could drill the new holes in the LE skin, the subskin, and the 408 rib, I needed to make sure that the entire LE assembly was attached just as it would be riveted to the wing, to ensure that the new holes end up in the correct location on the subskin and the 408 rib flange. Getting that beast secured onto the wing spar was no easy task. Lots of holes to line up and cleco in place, and needed to apply some added "pressure" here and there to get the holes to line up.
Then I did the deed. Marked each location with my hole punch and drilled two new #40 holes in the LE skin. Exciting stuff-not, I know, but much needed progress for me.
Each holes seemed to line up with the others OK - but the only time I will know for certain is when I actually rivet everything together. I seem to have this strange problem with keeping things in a straight line, even after I have measured and marked everything correctly. Must be a perception thing with my lovely progressive lense glasses. Anyway, the above pics are the top side adn bottom side holes.
Here is a pic with the LE all clecoed in place. Not shown are the clecoes attaching the rear rib flanges to the wing spar web. I started with those and then attached the LE skin to the wing spar flanges, after positioning the subskin in place and getting that all lined up with the LE rib flanges and the skin. What fun that was for the 12th time.Once its all together it looks pretty good.
I put clecoes in each of the new holes and felt for proper clearance with my fingers inside the "tunnel." Feels like I did everything right, and that the holes are in the right place in all 3 pieces of metal. Since the flanges all face away from the opening, I had to reach inside around the rib web and feel where the edges of the rib flange and the cleco were located. Not that this mattered much, since I knoew I had to remove the whole Le assembly anyway, but I wanted some sort of "immediate" confirmation that I had done this correctly.
Next steps
Leave all ribs, subskin, and LE skin attachements in place
Remove the clecoes holding the LE onto the wing spar
Remove the entire LE assembly, this time with the subskin still attached
Check all hole clearances visually, including the clearance for the shop head of the last hole (where I trimmed the 408 rib flange.
Disassemble the two 408 ribs and debur the new holes in all parts.
Trim any additional rib flange material as needed to ensure that the shop head of the rivet in that last hole will clear it.
Prep the modified 408 rib for primer and prime it.
Rivet on the two rear rib flange extensions to the modified 408 rib. (I could not do this long ago because I needed to prime the rib first - yet another reason why I stopped where I did.)
Re-attach the entire LE assembly to the wing spar (AGAIN!!)
Drill two more holes, this time match drilling the holes in each rear rib flange
Remove the entire LE assembly (AGAIN!)
Debur the two new rear rib flange holes
Disassemble the entire LE, prep and prime all LE parts, EXCEPT the subskin.
Determine precise measurements and locations for the subskin. A lot of the subskin material will be removed since it will not be needed. Only the portion that wraps around the LE and serves as the mounting flange for the modified outer LE skin needs to remain "as is." The rest gets cut away, leaving only about 1.5 inches over the top and bottom rib flanges of both 408 ribs.
Trim the subskin, prep and prime
Rivet the LE assembly together
Do the same madness for the right wing, starting with bending/forming the subskin for that side.
Wash, rinse repeat for the right wing.
Move on to the fuel tanks.
Till next time, KPR.
Friday, April 14, 2017
Carefully trimmed the end of the 408 rib flanges
Tonight I felt brave enough to perform what I call "metal surgery" on the 408 rib flanges. I call it surgery because in essence that is exactly what it is. There are times in this build where you have to apply caution, finesse, and ultimate control over your tools and clamping/securing methods in order to achieve a desired outcome.
I needed to perform precision cutting with my Dremel tool cutoff wheel and be very careful not to let it slip and cut things that should not be cut. After the use of my cutoff wheel, some sandpaper, and a small 1 inch round scotch brite wheel in an electric drill, I think I was successful. From the pics I still need to smooth and shape one of the flanges a bit more, but the other side looks pretty good. Also, in hindsight, I think I may have to remove a bit more material on the flange closest to the rib web, as I remembered that to clear the shop head I need to provide clearance all around the old drill hole. I don't think I accounted for the space closest to the rib web in my measurements. At any rate, enough material was removed from the flange for the hole for the new rivet to be drilled, so I will start there and adjust as necessary.
Here are the top and bottom flanges after the surgery:
I needed to perform precision cutting with my Dremel tool cutoff wheel and be very careful not to let it slip and cut things that should not be cut. After the use of my cutoff wheel, some sandpaper, and a small 1 inch round scotch brite wheel in an electric drill, I think I was successful. From the pics I still need to smooth and shape one of the flanges a bit more, but the other side looks pretty good. Also, in hindsight, I think I may have to remove a bit more material on the flange closest to the rib web, as I remembered that to clear the shop head I need to provide clearance all around the old drill hole. I don't think I accounted for the space closest to the rib web in my measurements. At any rate, enough material was removed from the flange for the hole for the new rivet to be drilled, so I will start there and adjust as necessary.
Here are the top and bottom flanges after the surgery:
the procedure was to use the cutoff wheel to carefully remove only the metal marked off by the cut lines shown in previous posts, then use the scotch brite attachments in the drill to smooth up the cut areas, and then finish smoothing the radiused areas where the old drill holes used to be. I used 220 aluminum oxide sand paper. This is the more expensive stuff, and the ONLY sand paper that you ever want to use on aluminum. DO NOT use regular home-grade sand paper, as the silica in that product can cause corrosion of aluminum. The correct paper can be found at auto stores.
Next up, drilling the new rivet holes in the LE skin. Admittedly this whole thing is a real pain in the butt (and thus the reason why I stopped where I did almost 2 years ago). Had I not decided to do this mod I would have been done with my wings by now. Anywho, no pain, no gain as they say. In the end it will be worth it. Problem is, I have to repeat the entire wing rib mod for the right wing when I get done with this one.
I have been monitoring the stats on my blog for a while now, and I hope that I helping a few other builders out there with various things b providing a bit more detail than you might find on other builder sites. Thanks for visiting.
Thursday, April 13, 2017
Finally working with metal again
The tasks at hand as elaborated on in my previous post are to
Trim the ends of the top and bottom 408-1-L rib flanges to allow clearance for the shop head of the rivet that will fill that last pre-drilled rib hole in the skin
Drill the new rivet holes in the top and bottom of the LE skin a little further up from the above-referenced holes
Assemble the LE on the wing (fully clecoed) and match drill the new holes through the top and bottom flanges of the 408 rib.
Well, after thinking about this for the hundredth time, I realized that I might need to allow some additional room for the shop head of the rivet, and then I also realized that I will probably be drilling and riveting through my "sub skin" since it will be riding on top of both inboard rib flanges. SO those final holes in the skin will actually be attaching the Le skin to the subskin, but not to a rib flange. SO they won't just be hole-filling rivets after all.
The math for the clearance allowance for the shop head of the AN426AD3 3/32 flush rivets is 1.5 x the diameter of the rivet shaft. So if the rivet is 3/32 inches wide, 1.5 x that diameter is 4.5/32nds, or just over 1/8th of an inch. ( I hate using decimal values to the thousandth measurement, so I do it this way. To each their own.) To make sure the rib flange will clear the shop head of that rivet, I needed to adjust the location of the hole in the skin by about another 1/16th of an inch.
This is why you think about this stuff a million times, then you measure more than twice, and then you drill or cut as needed, and hope you did steps one and two correctly for you got to step 3.
Here is the first pics showing the new cutline raised about 1/16th of an inch on the rib flanges
Trim the ends of the top and bottom 408-1-L rib flanges to allow clearance for the shop head of the rivet that will fill that last pre-drilled rib hole in the skin
Drill the new rivet holes in the top and bottom of the LE skin a little further up from the above-referenced holes
Assemble the LE on the wing (fully clecoed) and match drill the new holes through the top and bottom flanges of the 408 rib.
Well, after thinking about this for the hundredth time, I realized that I might need to allow some additional room for the shop head of the rivet, and then I also realized that I will probably be drilling and riveting through my "sub skin" since it will be riding on top of both inboard rib flanges. SO those final holes in the skin will actually be attaching the Le skin to the subskin, but not to a rib flange. SO they won't just be hole-filling rivets after all.
The math for the clearance allowance for the shop head of the AN426AD3 3/32 flush rivets is 1.5 x the diameter of the rivet shaft. So if the rivet is 3/32 inches wide, 1.5 x that diameter is 4.5/32nds, or just over 1/8th of an inch. ( I hate using decimal values to the thousandth measurement, so I do it this way. To each their own.) To make sure the rib flange will clear the shop head of that rivet, I needed to adjust the location of the hole in the skin by about another 1/16th of an inch.
This is why you think about this stuff a million times, then you measure more than twice, and then you drill or cut as needed, and hope you did steps one and two correctly for you got to step 3.
Here is the first pics showing the new cutline raised about 1/16th of an inch on the rib flanges
The other thing that I realized is that by raising the cut line of the flanges, I also needed to raise the radius hole that will provide a smooth transition between the small portion of the rib flange that I am not cutting and the new "end" of the rib flange after I finish trimming them up. So I used my tapered round needle file to slowly move the hole up to the new corner of the flange to provide the radius for the corner that was originally going to be established by the original rivet hole.
This next pic came out dark but clearly shows the change to the hole that provides the radius for the flange as applied by the file:
I'll remove the rib from the wing spar and then use my Dremel cutoff wheel to carefully trim off the metal from both rib flanges. Once that is done there will be enough clearance for the shop head of the rivet so that it does not rub or interfere with the rib flange.
Next we move on to the LE skins and remarking for the new rivet hole location about 1/16th inch higher than the previous one. Then I had to figure out how I was going to drill the holes in the LE skin without having it mounted to the wing spar. I don't have very good luck with curved surfaces (See my posts when I tried to rivet the left skin for the HS. First rivet was OK. Second rivet was disaster. Without it installed on the wing the open skin is quite flimsy. I cant put the rib in there because the rib does not get drilled until the LE is attached solidly to the wing.
SO I came up with a solution by setting it upright on my table and using a couple of wood blocks on the inside and outside of the skin to keep it from moving. Since the skin is curved and not quite flat, I also put some shims in front of the inner wood block so that the skin has some support and the drill bit has something to bite into on the back side without distorting the skin too much. Notice the new drill hole mark about 1/16th inch higher than the previous one, to compensate for the additional rib flange material that I have to remove.
And finally the set of needle files that I have been using for various precision metal trimming chores
Then it got late so I decided to wait till tomorrow to do the trimming and drilling, preferably when there is still some light outside.
till next time, KPR
Wednesday, April 12, 2017
The perils of doing a LE mod - continued
I measured and marked some holes for the left wing leading edge. the hole spacing for the W-408-1-L leading edge is different from those on the W709 rib that normally goes in the location that I am having to modify by using the different rib. This, combined with the fact that the rib-to-skin flanges on the top and bottom of the 408 rib are slightly shorter than the ones on the W709 rib, has created a situation where there is not enough material on the rib flange to locate the top and bottom rib flange holes that are closest to the wing spar flange.
Therefore my solution is to move the hole up about 1/4 inch so there is enough rib flange material to attach a rivet. This is where the top side final rivet hole ended up when I match drilled using the LE skin:
Therefore my solution is to move the hole up about 1/4 inch so there is enough rib flange material to attach a rivet. This is where the top side final rivet hole ended up when I match drilled using the LE skin:
As you can see the last hole is right on the bottom of the flange = no good for riveting. This is the result of having to use a rib with a shorter flange and trying to match drill the existing holes in the LE skin, which were originally spaced for the W-709 rib, and not this one. Here is the hole in about the same place on the bottom of the flange:
The "minimum-effort" solution to this problem involves removing the material around the last hole on both flanges. I then measured for a new hole about a 1/4 inch above the top of the old hole that will be removed. I then applied the same measurements to the top and bottom of the LE skin as shown in the next series of pics.
The above pic shows the distance for the original W408 rib's rivet holes on the inboard edge of the LE skin. The hole on the left is the rivet hole that attaches the skin to the top wing spar flange (not the rib flange). The next hole to the right is about 1.5 inches from the center of the wing spar flange hole, and the rest of the holes are spaced about 1 inch apart until you get to the bottom of the rib, where the last two bottom holes will be 1.5 inches apart again.
This next pic is the measurement of the hole pattern in the LE skin for the original W709 rib. I am using these same holes for the new rib as much as possible to avoid having to drill new holes in the skin. These holes are spaced a little further apart because this rib does not have to provide support for the fuel tank support like the other inboard rib does.
All of these holes appear to be about 1.25 inches apart, including the wing spar attach hole to the first rib flange hole. Basically the new rivet hole will be drilled about 1.4 inch above the top of the first rib flange hole. Then I plan to fill the hole shown in the pic (first flange hole to the right of the wing spar attach hole) with a small rivet just to close the hole. It will not be attached to anything.
The next pic is the marks on the rib flanges for the new holes:
The line on the top of the hole will be the cut line to remove the bottom hole from the flange. I need to maintain 1/4 inch edge distance from the end of the flange. This is where the second line was drawn. I will predrill the new holes in the wing skin, then match drill the new holes through the skin with the entire Leading edge assembly clecoed and attached to the wing spar.
The flash from my camera washed out the lines a bit, but you get the idea. These are the new holes in the LE skin top and bottom that will be drilled (where the sharpee lines cross). I did not want to drill them tonight as I am tired, and I definitely do not want to screw any of this up, So I will drill the new holes in the skin and remove the ends of each 408 rib to skin flange tomorrow.
Until next time......KPR
Monday, April 10, 2017
Been busy preparing for more metal work
For the past week and a half I have been "re-acquainting" myself with my build. I've been dong lots of research on various things, and I am getting ready to place an order with Vans and Aircraft Spruce for a variety of things. Other than getting my pitot mast resized and re-drilled, I have been:
- Researching and reviewing my SafeAir pitot/static line kit, and reading about all kinds of static source issues and solutions for various installations. I'm trying to figure out if I am going to use the supplied static ports from the SafeAir kit, or get the ones from Cleaveland Tools.
- Reviewing instructions for my SafeAir Bung kit for the fuel tanks, and my access panel kit for the leading edge. These are the line connecton ports on the outboard side of each tank that will allow me to connect supplemental fuel tanks after I complete the build
- Deciding if I am going to install the stall warning kit from Vans in the left wing. Right now I think the answer is no, as I will be using an AOA indicator with both visual and aural indications. I'm still conflicted by this a bit, since the AOA is a purely electronic solution, and susceptible to failures, and the stall warning vane is electro-mechanical.
- Deciding the location of my pitot mast on the wing and designing a backing plate for it
- Removed the leading edge from left wing to expose my modified LE rib, right where I left it almost 2 years ago. Lots of flange riveting to do yet.
- Finally determined what to do about the rib flanges that attach to the skin. My custom built rib does not have the same rivet pattern on the very last hole that attaches the skin to the LE rib closest to the wing spar, and then to the wing spar flange. Instead of making a flange extension using a dongle technique, (see my old posts on this) I just need to trim the last part of the rib flange off to remove the drill hole on the very end of the flange, and measure and drill a new hole in the wing skin and the rib flange, followed by one more additional rivet in the skin and wing spar. Basically I will create new rivet holes that match the hole pattern for that rib in its stock position on the inboard side of the LE. I know I know, pics of all this will be easier to understand. Stay tuned.
- Reviewed my landing, position, and strobe light assembly and wiring instructions. Posted to VAF to get pics of the inside of the wing tips with the same light and antenna setup that I am planning for my bird.
- Reviewed lots of VAF posts about antenna placement and wiring. I mean LOTS!
- Gonna order the composite practice kit from Aircraft Spruce, and some hinges and other assorted metal from Vans. Time to get the hands dirty.
- Starting to put together my list for a quickbuild RV-8 fuselage kit. That's gonna come in a really big box!
- Starting to measure out the cuts that I will need to make in my sub-skin mod so I can put that in its final form so I can finally prime and mount the left wing LE.
- I need to recheck and correct for twist in the wing frames. Spot checks show that things are mainly level, but I think they need to be tweaked a bit. I may need some help with that.
Wednesday, April 5, 2017
Pitot Mast trimmed and new screw holes measured, drilled and tapped
I'll add some pics tomorrow. After getting some feedback from VAF folks and from Vans, I determined that I could trim about .5 inches from the SafeAir Pitot mast to remove the old screw holes and re-drill new screw holes to mount my replacement heated pitot tube from Dynon. Took about 2 hours total to gather and setup the needed tools, cut off the portion of the mast, file it smooth and flat, measure the screw hole locations, and drill and tap the new screw holes.
Tools used were my band saw, my disk sander, a hand-held flat file, my scotch brite wheel, metal straight edge/ruler, hole punch, ultra fine blue Sharpee, my cordless drill, electrical tape, 3 in one oil, the following drill bits: #51, #36, and 9/64ths, a 6-32 tap with small handle, my table vise, 3 blocks of wood, a small level, and my old pitot tube. Who would have thought that so many tools would be needed just to drill and tap a few screw holes!
Thanks to my friend and fellow RV-8 builder Steve Riffe, who is about to finish building and take his first flight in his new airplane, I used his procedure from his kit log to mark, drill, and tap the new screw holes, and all went pretty well.
This time there was no drill press involved. I marked line around the mast that would ensure that the old screw holes would be completely removed. I had to dust the cobwebs off my band saw and set it up for the cut by using a small 2x4 piece of wood to set the odd-shaped pitot mast with its mounting flange onto so that I could run the wood and the mast through the saw. The cut was raw and somewhat jagged, and would require some file-finishing, leveling, and smoothing before it would be ready for the new screw holes and the new pitot tube.
I tried to use my disk sanding wheel on my electric sander but it was so clogged with old wood dust that this was not very effective. The end result was a smoother edge on the newly cut mast, but it was not very straight. Out came the hand-held flat file. I used the level and eyeballs to check for flatness of the newly cut edges, noted the high and low spots, and started slowly running the file over both sides of the top of the mast. I managed to get it very flat and square again, but also know that I had file marks that I would need to get rid of, so over to the scotch brite wheel I went. I was able to polish the file marks out to remove any potential stress risers on the end of the mast. I then used the old pitot tube to trial fit it into the mast. this was easier than using the new pitot tube because it no longer has the long tubes and electrical wiring in the way, since all this had to be removed as part of the pitot replacement procedure from Dynon. Never thought I would be using it again, but it came in handy for trial fitting the pitot into the newly cut mast.
Here is a pic that does not show all of the tools I used, but close:
Once I was satisfied, I replaced the old pitot tube with the new one, verified the fit, and taped it in place on the mast. Then I measured the same 11/32 inches at the base of the pitot tube mounting flange and re-verified the marked lines for the proper location of the 4 holes. I put tape on the end of all drill bits so that only 1/4 inch of the bit was exposed so as not to drill too deeply and damage the tubing internally. I then used the hole punch to set starter holes in the mast for the drill bit. I sandwiched the tube and mast assembly between two small pieces of wood and secured the assembly in my table vise, being careful not to apply too much pressure to avoid damaging the pitot tube. All you need is enough to hold the assembly so you can drill the 4 mounting holes.
I started with the #51 drill bit to drill pilot holes into the pitot tube. Wow, say that 5 times real fast! Here is a TIP: When drilling, the metal extensions inside the pitot tube that provide the material for the screw threads extend inward only so far. If you have drilled what you believe to be 1/4 inches into the pitot tube and the drill bit has not broken through this material, keep drilling just a bit more until you feel the bit go completely through. Be careful not to go too far. Doing this ensures that the tap will be able to properly set the threads in the hole. When I did this the first time long ago I don't think I drilled one of the holes all the way through, and my tap then stripped several threads as I tried to force the tap to go in further when it had no more room to do so.
I did all the drilling by hand using my cordless drill, going slowly and ensuring that the bit was as level as I could make it, and that it also followed the contour the curvature of the pitot mast assembly. this is NOT a very easy thing to do because the front and back ends of the tube and mast are shaped like a big fat wing for obvious reasons. So the curvature is different from front to back. If you align the drill bit with the metal extensions in the top of the tube you will be fine.
After the 4 pilot holes were drilled I switched to the #36 drill bit and re-drilled the holes again. Once this was done the holes in the pitot tube were ready for the 6-32 tap. I did all that by hand as well, and even took the tube out of the table vise and held it in one hand while tapping with the other. I used 3 in 1 oil to lube the tab, and made sure I applied the tap a little at a time and then backed it out, cleaned up the sludge, and the tapped it a little bit more. I did this until I felt the tap free up, which is a sign that all the threads in the material have been formed properly.
The most concerning part of this process, which I have reported on in my earlier posts when I tried this the first time, was tapping the two forward screw holes. The tap has to extend rather far into the inside of the pitot tube to properly tap both forward holes, and the tip of the tap comes very close to the internal metal air lines that provide the airflow to your instruments. I am still concerned that the tap may have scored the front part of the front tubing, but I did not feel it hitting anything, so perhaps I am OK here. The tap is tapered on the front, so maybe that also helped prevent any compromise of the forward tub as well. All I know is that the tap comes really close to this tube by the time you have properly cut the threads on those forward holes, so be careful.
With all four holes successfully tapped, I final drilled the mast holes using the 9/64ths drill bit to make a clearance hole for the 6-32 x 1/4 inch long screws. I successfully screwed in all four screws and verified that they all tighten up as expected. YAY! no stripped threads this time! Then I removed the screws and place the pitot tube back into the mast and screwed them together again to ensure proper hole alignment through the mast and to re-seat the threads in the new holes. I am goin g to order specifically sized counter sunk screws from Aircraft Spruce and will counter sink the holes in the mast once I have those screws in hand. Right now I am using the stainless steel pan head screws that I had to trim down because they only come in 3/8 inch sizes and are too long. These add a small amount of drag as the screw heads stick out into the slip stream. I will now use the flush head screws now that I know this part of this tedious process is behind me.
The finished product, on a mast that is about a half inch shorter now:
The location of the screw holes also came out much more symmetrical than my first attempt. Its still not quite perfect but is much better than the last time. The inlet hole of the pitot tube ends up being 6 inches from the bottom of the wing - exactly where I expected it would be. I'm glad to get this small step completed, and hope I never have to do it again! I still have the tubes to trim, and tubing flanges and NPT hardware to set up, as well as mounting the tube to the wing, but that will be done later, after other wing assembly steps have been completed.
Tools used were my band saw, my disk sander, a hand-held flat file, my scotch brite wheel, metal straight edge/ruler, hole punch, ultra fine blue Sharpee, my cordless drill, electrical tape, 3 in one oil, the following drill bits: #51, #36, and 9/64ths, a 6-32 tap with small handle, my table vise, 3 blocks of wood, a small level, and my old pitot tube. Who would have thought that so many tools would be needed just to drill and tap a few screw holes!
Thanks to my friend and fellow RV-8 builder Steve Riffe, who is about to finish building and take his first flight in his new airplane, I used his procedure from his kit log to mark, drill, and tap the new screw holes, and all went pretty well.
This time there was no drill press involved. I marked line around the mast that would ensure that the old screw holes would be completely removed. I had to dust the cobwebs off my band saw and set it up for the cut by using a small 2x4 piece of wood to set the odd-shaped pitot mast with its mounting flange onto so that I could run the wood and the mast through the saw. The cut was raw and somewhat jagged, and would require some file-finishing, leveling, and smoothing before it would be ready for the new screw holes and the new pitot tube.
I tried to use my disk sanding wheel on my electric sander but it was so clogged with old wood dust that this was not very effective. The end result was a smoother edge on the newly cut mast, but it was not very straight. Out came the hand-held flat file. I used the level and eyeballs to check for flatness of the newly cut edges, noted the high and low spots, and started slowly running the file over both sides of the top of the mast. I managed to get it very flat and square again, but also know that I had file marks that I would need to get rid of, so over to the scotch brite wheel I went. I was able to polish the file marks out to remove any potential stress risers on the end of the mast. I then used the old pitot tube to trial fit it into the mast. this was easier than using the new pitot tube because it no longer has the long tubes and electrical wiring in the way, since all this had to be removed as part of the pitot replacement procedure from Dynon. Never thought I would be using it again, but it came in handy for trial fitting the pitot into the newly cut mast.
Here is a pic that does not show all of the tools I used, but close:
Once I was satisfied, I replaced the old pitot tube with the new one, verified the fit, and taped it in place on the mast. Then I measured the same 11/32 inches at the base of the pitot tube mounting flange and re-verified the marked lines for the proper location of the 4 holes. I put tape on the end of all drill bits so that only 1/4 inch of the bit was exposed so as not to drill too deeply and damage the tubing internally. I then used the hole punch to set starter holes in the mast for the drill bit. I sandwiched the tube and mast assembly between two small pieces of wood and secured the assembly in my table vise, being careful not to apply too much pressure to avoid damaging the pitot tube. All you need is enough to hold the assembly so you can drill the 4 mounting holes.
I started with the #51 drill bit to drill pilot holes into the pitot tube. Wow, say that 5 times real fast! Here is a TIP: When drilling, the metal extensions inside the pitot tube that provide the material for the screw threads extend inward only so far. If you have drilled what you believe to be 1/4 inches into the pitot tube and the drill bit has not broken through this material, keep drilling just a bit more until you feel the bit go completely through. Be careful not to go too far. Doing this ensures that the tap will be able to properly set the threads in the hole. When I did this the first time long ago I don't think I drilled one of the holes all the way through, and my tap then stripped several threads as I tried to force the tap to go in further when it had no more room to do so.
I did all the drilling by hand using my cordless drill, going slowly and ensuring that the bit was as level as I could make it, and that it also followed the contour the curvature of the pitot mast assembly. this is NOT a very easy thing to do because the front and back ends of the tube and mast are shaped like a big fat wing for obvious reasons. So the curvature is different from front to back. If you align the drill bit with the metal extensions in the top of the tube you will be fine.
After the 4 pilot holes were drilled I switched to the #36 drill bit and re-drilled the holes again. Once this was done the holes in the pitot tube were ready for the 6-32 tap. I did all that by hand as well, and even took the tube out of the table vise and held it in one hand while tapping with the other. I used 3 in 1 oil to lube the tab, and made sure I applied the tap a little at a time and then backed it out, cleaned up the sludge, and the tapped it a little bit more. I did this until I felt the tap free up, which is a sign that all the threads in the material have been formed properly.
The most concerning part of this process, which I have reported on in my earlier posts when I tried this the first time, was tapping the two forward screw holes. The tap has to extend rather far into the inside of the pitot tube to properly tap both forward holes, and the tip of the tap comes very close to the internal metal air lines that provide the airflow to your instruments. I am still concerned that the tap may have scored the front part of the front tubing, but I did not feel it hitting anything, so perhaps I am OK here. The tap is tapered on the front, so maybe that also helped prevent any compromise of the forward tub as well. All I know is that the tap comes really close to this tube by the time you have properly cut the threads on those forward holes, so be careful.
With all four holes successfully tapped, I final drilled the mast holes using the 9/64ths drill bit to make a clearance hole for the 6-32 x 1/4 inch long screws. I successfully screwed in all four screws and verified that they all tighten up as expected. YAY! no stripped threads this time! Then I removed the screws and place the pitot tube back into the mast and screwed them together again to ensure proper hole alignment through the mast and to re-seat the threads in the new holes. I am goin g to order specifically sized counter sunk screws from Aircraft Spruce and will counter sink the holes in the mast once I have those screws in hand. Right now I am using the stainless steel pan head screws that I had to trim down because they only come in 3/8 inch sizes and are too long. These add a small amount of drag as the screw heads stick out into the slip stream. I will now use the flush head screws now that I know this part of this tedious process is behind me.
The finished product, on a mast that is about a half inch shorter now:
The location of the screw holes also came out much more symmetrical than my first attempt. Its still not quite perfect but is much better than the last time. The inlet hole of the pitot tube ends up being 6 inches from the bottom of the wing - exactly where I expected it would be. I'm glad to get this small step completed, and hope I never have to do it again! I still have the tubes to trim, and tubing flanges and NPT hardware to set up, as well as mounting the tube to the wing, but that will be done later, after other wing assembly steps have been completed.
Monday, April 3, 2017
Remounting my replacement Dynon Heated Pitot tube
A very long time ago Dynon had some issues with their heated Pitot Tube probes where ice or water blockages were causing erroneous airspeed indications. Since Dynon's attitude reference is based on airspeed, this caused a number of different problems with their EFIS and autopilot systems. From some of the accounts that I read many of them were what I refer to as just short of loss of control types of events with the autopilot. This is not something I wanted to experience if flying IFR, or any other time for that matter.
They apparently found an issue with the location of their drain holes on the bottom of the tube, and after doing some robust testing came out with a redesigned pitot tube. I have not seen many flight reports since the new tubes were sent out to existing customers, but the ones that I have seen seem to indicate that the former problems have been resolved.
That said, I received my replacement Pitot tube a long time, and it has been sitting idle ever since. IN the past 2 weeks I have ben reviewing my blog posts and re-organizing my shop and getting re-acquainted with some parts that I had ordered for a variety of things. Among these are the bung kit for my future auxiliary fuel tanks, leading edge access hatch kit, LED landing, position, and nav lights from AeroLED, and the replacement heated pitot tube from Dynon.
If you search for the words Pitot Tube you will find a handful of previous posts where I performed the initial mounting of the tube to its mast. This did not go well for me the first time, and I plan to make sure it goes much better this time. The main reason for this is that the pitot mast that extends down from the bottom of the wing skin to provide clearance between the wing and the tube is a very expensive part that I do not wish to replace if possible. I messed up the mounting holes the first time and so I want to trim the pitot mast just a bit so I can redrill new holes.
I submitted a post to VAF to ask if there are any issues with trimming the mast below its original size. Airflow around the tube is a concern, as this is what is used to provide airspeed information in the cockpit. Click here to see the VAF post. If I can trim the mast down a bit I can redrill new holes and hopefully be done with that once and for all.
I've also got an order to aircraft spruce and Vans to make - time to start getting building supplies again. I am going to start with the pitot tube as a way to begin with a "small" project and then work my way back into the leading edge and fuel tank mess that I left almost 2 years ago. I need to make a decision about the fuel tank skin that messed up with a deep scratch made by a cleco while trying to force it into the skin and rib - not fun, and expensive if I need to replace the skin.
Like I have said before, I know exactly where I left off. it ain't pretty but I just need to tackle one problem at a time and move on. That is how you build an airplane one day.
They apparently found an issue with the location of their drain holes on the bottom of the tube, and after doing some robust testing came out with a redesigned pitot tube. I have not seen many flight reports since the new tubes were sent out to existing customers, but the ones that I have seen seem to indicate that the former problems have been resolved.
That said, I received my replacement Pitot tube a long time, and it has been sitting idle ever since. IN the past 2 weeks I have ben reviewing my blog posts and re-organizing my shop and getting re-acquainted with some parts that I had ordered for a variety of things. Among these are the bung kit for my future auxiliary fuel tanks, leading edge access hatch kit, LED landing, position, and nav lights from AeroLED, and the replacement heated pitot tube from Dynon.
If you search for the words Pitot Tube you will find a handful of previous posts where I performed the initial mounting of the tube to its mast. This did not go well for me the first time, and I plan to make sure it goes much better this time. The main reason for this is that the pitot mast that extends down from the bottom of the wing skin to provide clearance between the wing and the tube is a very expensive part that I do not wish to replace if possible. I messed up the mounting holes the first time and so I want to trim the pitot mast just a bit so I can redrill new holes.
I submitted a post to VAF to ask if there are any issues with trimming the mast below its original size. Airflow around the tube is a concern, as this is what is used to provide airspeed information in the cockpit. Click here to see the VAF post. If I can trim the mast down a bit I can redrill new holes and hopefully be done with that once and for all.
I've also got an order to aircraft spruce and Vans to make - time to start getting building supplies again. I am going to start with the pitot tube as a way to begin with a "small" project and then work my way back into the leading edge and fuel tank mess that I left almost 2 years ago. I need to make a decision about the fuel tank skin that messed up with a deep scratch made by a cleco while trying to force it into the skin and rib - not fun, and expensive if I need to replace the skin.
Like I have said before, I know exactly where I left off. it ain't pretty but I just need to tackle one problem at a time and move on. That is how you build an airplane one day.
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