Hurry up and finish this plane so that I can be somewhere else that is warmer and less windy than here in Denver in the months of January and February. This month has just been the absolute pits. High winds, cold temps, illnesses, work crap - just the pits. So long February 2018 - don't come back any time soon!
As a result of all that I have not been able to do much on the plane until last night. I was finally able to do the file folder straight edge trick and confirmed that my suspicions were correct. This time the lines matched up almost perfectly - much much better than before.The real culprit does appear to be the measurements I took from the forward most rivet holes for each rib flange, which are about 1/16th of an inch offset from the rest of the rib flange rivet holes, due to the reasons I stated in the previous post. This caused my cut line measurement to be off by that same amount, resulting in lines that did not "connect" on either side of the LE skin very well.
By NOT applying ANY measurements from these forward-most rivet holes, and only using measurements from the other holes that are in alignment with each other, the connecting lines around the front of the LE skin all seemed to line up as expected this time. Glad that that mess is over. Now I am just waiting for some warmer weather so I can get back to the "real" work. Now that the cut lines are drawn again, I can mark and match drill #40 holes for the added rivet lines that will secure the skin edges near the cut line, as well as #30 screw holes for the nut plates that will provide the attach points for the modular LE part. Then back to fabricating more parts for the inboard fuel tank rib.....
Wednesday, February 28, 2018
Sunday, February 11, 2018
Small Amount of work done on the Leading Edge
Life and weather getting in the way again. After enduring a snow storm yesterday, the weather finally warmed up enough to get out and do something on the airplane. Unfortunately that "something" was pretty minor. I finally decided to redraw the lines on my LE for the rivet line, cut line, and nut plate line.
In a prior post when I did this the first time, I noted that when I performed my trick to extend the cut line from one side of the Le to the other using a file folder as a flexible straight edge, I was not happy with how the lines were close, but not quite lining up with each other correctly. SO I vowed to correct this problem at a later time. Well, that time was now. At that time I commented that I had made my marks by referencing both sides of my best guess as to a centerline based on the centers of the rivet holes on both sides of the skin. I reasoned that I might not have accurately measured the lines on the top and bottom of the skin, and that may have been the reason the lines were slightly off when I tried to join them together with the file folder trick. So I surmized that the next time I would use measurements from a single reference point - that being the inboard edge of the LE skin. ALL measurements for both sides of the skin would be taken using the inboard edge of the wing skin as the reference point.
I had to take some isopropyl alcohol to remove the previous permament Sharpee lines. Works great for removing the so-called "permanent" marker. After that was done I set out to recreate the lines using the inboard edge of the LE skin this time. I started with the bottom side of the LE. I removed the necessary clecoes ad then suddenly realized why my line measurements s might have been slightly off. The very first rivet holes closest to the Actual LE of the airplane are in a very slightly different location than the line of the remaining rivet holes. this is because this very first hole goes through a single tab flange in the forward-most part of the rib. This tab is not as wide as the rest of the main part of the rib flange because this nose area of the rib is gradually reduced as it forms the very tip of the rib, and then it begins to widen again as it wraps around the the other side of the rib. I believe that this occurs as a result of the rib forming process at the factory, where slots are cut into the rib flange area BEFORE the flanges are bent, and they must also be cut at an angle to each other to avoid interfering with each other as the flanges are bent around the semi-circular form of the curve of the LE. Each successive rib flange TAB gets a little smaller than the previous one, until the curve is completed and the flanges can resume a more normal, flatter shape.
As a result of this reduction in flange surface area, the rivet hole of that very first hole ends up being about 1/16th of an inch offset from the other rivet holes. So I think I may have made an incorrect measurement by measuring the distance from the very first set of rivet holes, which obviously would have forced the line from the other rivet holes to be adjusted by that 1/16th of an inch offset, which is why my lines did not match up to each other very well. So the lesson learned from that experience was NOT to use the forward-most rivet holes as a basis for measuring any lines that originate from the other rivet holes further back along the rib.
With that now understood, I proceeded to re-measure the lines again. the numbers, starting with the edge of the LE skin near the second rivet hole (not the first), was about 1 and 1/16 inches from the edge of the skin. This still left a 3/4 inch distance between the rivet hole and the first line known as the rivet line. the second measurement taken from the inboard edge of the LE skin was 9 and 9/16th of an inch. This marks the rivet line on the more outboard line as measured from the inboard edge of the skin, instead of from the rivet hole from the rib line on that outer section of the LE skin. This also results in s 3/4 inch spacing of the rivet line and the rivet holes of the second rib, which matches the spacing on the inboard rib flange. So far so good.
With both rivet lines drawn correctly this time, I was able to measure the same 5/16 inch spacing for the remaining inboard and outboard cut lines and nut plate lines on the inboard and outboard side of the LE skin. Just need to make another file folder flexible straight edge and confirm that the lines on the top and bottom of the LE skin on the inboard and outboard sides now line up as expected. This has to be the case before I finish this exercise by marking and drilling the initial holes for the new rivets and the nutplates that will need to be added.
Lots more work coming up on the fuel tanks, and some orders to place at Vans and a few other places for some parts and supplies that I need, including some special 90 degree corner nut plates for a #8 screw. More later.
KPR
In a prior post when I did this the first time, I noted that when I performed my trick to extend the cut line from one side of the Le to the other using a file folder as a flexible straight edge, I was not happy with how the lines were close, but not quite lining up with each other correctly. SO I vowed to correct this problem at a later time. Well, that time was now. At that time I commented that I had made my marks by referencing both sides of my best guess as to a centerline based on the centers of the rivet holes on both sides of the skin. I reasoned that I might not have accurately measured the lines on the top and bottom of the skin, and that may have been the reason the lines were slightly off when I tried to join them together with the file folder trick. So I surmized that the next time I would use measurements from a single reference point - that being the inboard edge of the LE skin. ALL measurements for both sides of the skin would be taken using the inboard edge of the wing skin as the reference point.
I had to take some isopropyl alcohol to remove the previous permament Sharpee lines. Works great for removing the so-called "permanent" marker. After that was done I set out to recreate the lines using the inboard edge of the LE skin this time. I started with the bottom side of the LE. I removed the necessary clecoes ad then suddenly realized why my line measurements s might have been slightly off. The very first rivet holes closest to the Actual LE of the airplane are in a very slightly different location than the line of the remaining rivet holes. this is because this very first hole goes through a single tab flange in the forward-most part of the rib. This tab is not as wide as the rest of the main part of the rib flange because this nose area of the rib is gradually reduced as it forms the very tip of the rib, and then it begins to widen again as it wraps around the the other side of the rib. I believe that this occurs as a result of the rib forming process at the factory, where slots are cut into the rib flange area BEFORE the flanges are bent, and they must also be cut at an angle to each other to avoid interfering with each other as the flanges are bent around the semi-circular form of the curve of the LE. Each successive rib flange TAB gets a little smaller than the previous one, until the curve is completed and the flanges can resume a more normal, flatter shape.
As a result of this reduction in flange surface area, the rivet hole of that very first hole ends up being about 1/16th of an inch offset from the other rivet holes. So I think I may have made an incorrect measurement by measuring the distance from the very first set of rivet holes, which obviously would have forced the line from the other rivet holes to be adjusted by that 1/16th of an inch offset, which is why my lines did not match up to each other very well. So the lesson learned from that experience was NOT to use the forward-most rivet holes as a basis for measuring any lines that originate from the other rivet holes further back along the rib.
With that now understood, I proceeded to re-measure the lines again. the numbers, starting with the edge of the LE skin near the second rivet hole (not the first), was about 1 and 1/16 inches from the edge of the skin. This still left a 3/4 inch distance between the rivet hole and the first line known as the rivet line. the second measurement taken from the inboard edge of the LE skin was 9 and 9/16th of an inch. This marks the rivet line on the more outboard line as measured from the inboard edge of the skin, instead of from the rivet hole from the rib line on that outer section of the LE skin. This also results in s 3/4 inch spacing of the rivet line and the rivet holes of the second rib, which matches the spacing on the inboard rib flange. So far so good.
With both rivet lines drawn correctly this time, I was able to measure the same 5/16 inch spacing for the remaining inboard and outboard cut lines and nut plate lines on the inboard and outboard side of the LE skin. Just need to make another file folder flexible straight edge and confirm that the lines on the top and bottom of the LE skin on the inboard and outboard sides now line up as expected. This has to be the case before I finish this exercise by marking and drilling the initial holes for the new rivets and the nutplates that will need to be added.
Lots more work coming up on the fuel tanks, and some orders to place at Vans and a few other places for some parts and supplies that I need, including some special 90 degree corner nut plates for a #8 screw. More later.
KPR
Sunday, January 28, 2018
Drove the Rivets for the cover plate
In case I have not mentioned this previously, lets just say that I am so glad that do NOT have put up with any of this stuff for the right wing fuel tank assembly. I finally got wipe to cobwebs off of my rivet gun and used it to set the 4 rivets to secure the cover plate over the hole. Since it had been so long since I had used the rivet gun and bucking bar to set rivets, I at least did the "smart" thing and took one of my test pieces that was already drilled, deburred, and dimpled, and still have a few holes available for some test rivets.
Another thing I wanted to do was test a flexible shaft flat rivet set with the rubber cup that surrounds the flat rivet set, which s at least 1.4 inch larger in circumference than my 1 inch flat set that have been using for my build up to this point. I bought this thing because it had the red rubber cup around the edges of the metal flat set, to allow it to grab the aluminum and keep it from slipping.SO I put it in my rivet gun, and well, lets just say that its a good thing I did some tests first, before I did the real thing.
Its hard to see in the next pic, but I was less than pleased with the rubber rivet set. The main reason was that the rubber extends almost 1/16th of an inch beyond the metal rivet set surface, and this does not allow the rivet set to sit directly on the rivet head before you squeeze the trigger on the rivet gun. The result was similar to what many others have experienced with this "stock" tool. The head of the rivet does not sit flush in the dimple and allows the head to rise up, resulting in a proud and improperly set rivet.
None of the pics of the shop heads came out very well, so you'll just have to trust me when I tell you that, in addition to poorly set manufactured heads, I also discovered that my air pressure was set way to high for the rivet gun. I don't even remember the last set if rivets that I drove with the rivet gun, but they must have been AN7470AD4 rivets, because the gun pressure was turned way up. The result on my test rivets was that the shop heads were all way over driven, and the gun was barely controllable.
Once I figured out how to turn down my gun pressure again, AND I switched back to my 1 inch wide flat rivet set, I was able to get satisfactory rivets.Here is the pic showing that horribly large flat set the rubber cup, and the bucking bars, rivet gauge, and my "normal" flat set already installed on the gun. You can see how much the rubber extends beyond the actual metal part of the larger flat set.
I think I can still make this larger set work, because I do continue to have problems with the flat set sliding off the rivet. I am going to have to sand or cut off the "excess" amount of rubber so that the flat set will make better contact with the surface of the rivet. I have to try taking off a little bit of rubber at a time, and run some more tests.
Now for the fun part. As I have mentioned many times before, the key to setting good rivets is all about how well you clamp the work piece to ensure that it will not bounce, bend, or vibrate in such a way that the rivet will not end up being set correctly. If you work alone and do not have a bucking buddy to help you, you absolutely MUST keep the work secure, since one hand will be operating the rivet gun, and the other will be working the bucking bar, the work piece has to be clamped down good. SO here is the contraption that I dreamed up - all for 4 rivets on one lousy fuel tank rib:
This "contraption" is made up of 6 different clamps, and 3 different wood blocks, all strategically placed on the work bench, with the rib positioned upright on the edge of the bench, with the bottom rib flange clamped in place first, followed by all the other clamps to make this assembly as rigid as possible, so I could set the 4 cover plate rivets. Here are the remaining detailed photos, showing exactly where and how I had to set each clamp to achieve the objective:
The smaller block of wood ha to used to ensure that the hing for the trap door could be cleared. the other clamps had to be placed carefully so that the stiffening rings would not be compromised. Every single one of these clamps was needed until I felt that the rib was stationary enough to be ready to set these rivets. Let's just say that I am glad that this is the only rib that I have to do all this work on.
And the final result, after using my standard rivet set with a piece of masking tape over the face of the set, and my "fat man" tungsten bucking bar.
At the end of it all I was pleased with the results, and my rivet gauge confirmed that the rivets were set correctly. There will be a million more of these rivets to set if and when I finally get to the point where I am riveting the skins to the wings.
With this little "project" done, I think I will turn my attention back on the Leading edge assembly, and I will remark the lines for the rivets, cut line, and nut plate locations on the LE skin, using the edge of the skin as my reference point, so that my spacing of everything from one side of the bay to the other is accurate and consistent.
I am now very close to making that dreaded cut in my LE skin.
On another note, we had our first YE rally of 2018 yesterday - flew 2 kids and one adult - had some engine issues on the third flight adn had to RTB shortly after Takeoff. Getting tired of dealing with fouled plugs on airplanes so I may renting a different one for next month's rally.
We also had our EAA Chapter 301 Founders Day Brunch and Awards Ceremony. A great time was had by all at the Mount Vernon Country Club high on top of Lookout Mountain. The Chapter is 50 years old as of the 23rd of this month, which is a pretty significant accomplishment, and we received a very nice new Chapter Banner from EAA HQ that looks really sharp.
Till next time, KPR....
Another thing I wanted to do was test a flexible shaft flat rivet set with the rubber cup that surrounds the flat rivet set, which s at least 1.4 inch larger in circumference than my 1 inch flat set that have been using for my build up to this point. I bought this thing because it had the red rubber cup around the edges of the metal flat set, to allow it to grab the aluminum and keep it from slipping.SO I put it in my rivet gun, and well, lets just say that its a good thing I did some tests first, before I did the real thing.
Its hard to see in the next pic, but I was less than pleased with the rubber rivet set. The main reason was that the rubber extends almost 1/16th of an inch beyond the metal rivet set surface, and this does not allow the rivet set to sit directly on the rivet head before you squeeze the trigger on the rivet gun. The result was similar to what many others have experienced with this "stock" tool. The head of the rivet does not sit flush in the dimple and allows the head to rise up, resulting in a proud and improperly set rivet.
Once I figured out how to turn down my gun pressure again, AND I switched back to my 1 inch wide flat rivet set, I was able to get satisfactory rivets.Here is the pic showing that horribly large flat set the rubber cup, and the bucking bars, rivet gauge, and my "normal" flat set already installed on the gun. You can see how much the rubber extends beyond the actual metal part of the larger flat set.
Now for the fun part. As I have mentioned many times before, the key to setting good rivets is all about how well you clamp the work piece to ensure that it will not bounce, bend, or vibrate in such a way that the rivet will not end up being set correctly. If you work alone and do not have a bucking buddy to help you, you absolutely MUST keep the work secure, since one hand will be operating the rivet gun, and the other will be working the bucking bar, the work piece has to be clamped down good. SO here is the contraption that I dreamed up - all for 4 rivets on one lousy fuel tank rib:
And the final result, after using my standard rivet set with a piece of masking tape over the face of the set, and my "fat man" tungsten bucking bar.
With this little "project" done, I think I will turn my attention back on the Leading edge assembly, and I will remark the lines for the rivets, cut line, and nut plate locations on the LE skin, using the edge of the skin as my reference point, so that my spacing of everything from one side of the bay to the other is accurate and consistent.
I am now very close to making that dreaded cut in my LE skin.
On another note, we had our first YE rally of 2018 yesterday - flew 2 kids and one adult - had some engine issues on the third flight adn had to RTB shortly after Takeoff. Getting tired of dealing with fouled plugs on airplanes so I may renting a different one for next month's rally.
We also had our EAA Chapter 301 Founders Day Brunch and Awards Ceremony. A great time was had by all at the Mount Vernon Country Club high on top of Lookout Mountain. The Chapter is 50 years old as of the 23rd of this month, which is a pretty significant accomplishment, and we received a very nice new Chapter Banner from EAA HQ that looks really sharp.
Till next time, KPR....
Thursday, January 25, 2018
Dimpled the Cover Plate for the Fuel Tank rib
Well I suppose that's a long enough break since my last post. Time for some updates. In my previous post I was trying to decide what side of the tank rib to place the cover plate over the hole in the web about half way up the width of the web. After mulling that over a bit, I decided to put it on the outboard side of the rib web instead of the rib web. My reasoning for this was that MOST of the time the wings should be level, and there is a slight dihedral angle in the wing where the tip will be just a bit higher than the root.
This, combined with a slightly positive angle of incidence of the wing while it is in sustained level flight, lead me to believe that pressure from the fuel inside the tank will be greater on the outboard sides of each rib most of the time, while the small holes at the bottom rear of each rib will allow fuel to slowly escape to the next inboard bay. Since the fuel pressure should be greater on the outboard sides of each rib due to the reasons I mentioned previously, I decided to put the cover plate on the outboard side of the hole in the rib web, so that any pressure from the fuel against that rib and the patch plate would tend to push the patch plate tighter against the rib web, keeping the fuel from entering that hole, and forcing it to go through the trap door instead, as intended.
Having finally decided where to put the plate, the next step was to dimple the holes for the rivets. This turned out to be yet another exercise in "imaginative problem solving." If you haven't guessed by now, I am documenting this entire tank rib trap door fabrication process because almost nobody documents this to the level of detail that satisfies me, and as it turns out, the steps required to complete this little side assembly are a little more involved than you might think.
First problem - decide which side to put the dimples for the 4 AN426AD3-3.5 rivets. I decided to use flush rivets for this since that should be sufficient for holing this small plate in place, and flush rivets take up less space inside the tank than an AN 470 rivet. Remember, I am trying to stuff as much fuel as possible in these tanks, so every little bit helps, even if that does seem a bit anal.
I decided to put the manufactured head of the rivet on the outboard side of the rib web. Again, this is because fuel pressure will tend to push the rivet head against the rib head, instead of pushing it away.
So I put the dimple dies in my hand squeezer and set the dimples in the over plate:
Next problem -I would need to use my C-Frame tool and table to set the dimples on the rib web. None of my yokes were long enough to reach the holes in the rib web. Then another problem cropped up. The trap door was getting in the way. In hindsight, all I had to do was remove the hinge, but stupid me likes to do everything the hard way. The rib sits awkwardly on the table because of the trap door.Another problem was that my C-Frame table had been setup with the male dimple die on the bottom and the female die on the top. With this application they would need to be reversed so that the male die is on the top and the female die is on the bottom. Why is this a problem - the female die is longer than the male die, so my table no longer sits "flush" with the dimple dies in this reversed state.
So the combination of the trap door interference and the reversed setup of the dimple dies on my C-Frame table presented some challenges:
Here you can see the female die sitting very proud of the table
And it looked like this sitting on the table as a result of the trap door interference:
So how do I get the rib to set level on the dimple dies so I can pound these dimples properly: I was not concerned about the proud dimple die situation, but I did not want the dimples to be improperly set at an angle, so leveling the rib web was a concern. My solution was to place a couple of the fuel tank access plates on the other side of the rib to level it out just enough for me to set the dimples properly.
And here are the pics with all the dimples set in both parts:
I will have to use the rivet gun and a bucking bar to set these rivets. this will be the first time I have picked up the gun in a very, very long time. I will have to do some practice rivets on some scrap first, to make sure my air pressures are set properly, and I get my timing back. I want to set all of these rivets perfectly so I can move on with other much more important tasks. This little adventure has certainly resulted way too much of a time suck on the build.
I also finally called my tech counselor Jim Elliot ad he came out for another visit to help me finalize plans for the mod to the Leading Edge. I think I now have all the info that need to be brave enough to drill the final rivet and nut plate holes in the skin and the subskin, so that I can take it off the wing spar and make that all important cutout. More on that visit and the next steps for that tomorrow.
KPR
This, combined with a slightly positive angle of incidence of the wing while it is in sustained level flight, lead me to believe that pressure from the fuel inside the tank will be greater on the outboard sides of each rib most of the time, while the small holes at the bottom rear of each rib will allow fuel to slowly escape to the next inboard bay. Since the fuel pressure should be greater on the outboard sides of each rib due to the reasons I mentioned previously, I decided to put the cover plate on the outboard side of the hole in the rib web, so that any pressure from the fuel against that rib and the patch plate would tend to push the patch plate tighter against the rib web, keeping the fuel from entering that hole, and forcing it to go through the trap door instead, as intended.
Having finally decided where to put the plate, the next step was to dimple the holes for the rivets. This turned out to be yet another exercise in "imaginative problem solving." If you haven't guessed by now, I am documenting this entire tank rib trap door fabrication process because almost nobody documents this to the level of detail that satisfies me, and as it turns out, the steps required to complete this little side assembly are a little more involved than you might think.
First problem - decide which side to put the dimples for the 4 AN426AD3-3.5 rivets. I decided to use flush rivets for this since that should be sufficient for holing this small plate in place, and flush rivets take up less space inside the tank than an AN 470 rivet. Remember, I am trying to stuff as much fuel as possible in these tanks, so every little bit helps, even if that does seem a bit anal.
I decided to put the manufactured head of the rivet on the outboard side of the rib web. Again, this is because fuel pressure will tend to push the rivet head against the rib head, instead of pushing it away.
So I put the dimple dies in my hand squeezer and set the dimples in the over plate:
Next problem -I would need to use my C-Frame tool and table to set the dimples on the rib web. None of my yokes were long enough to reach the holes in the rib web. Then another problem cropped up. The trap door was getting in the way. In hindsight, all I had to do was remove the hinge, but stupid me likes to do everything the hard way. The rib sits awkwardly on the table because of the trap door.Another problem was that my C-Frame table had been setup with the male dimple die on the bottom and the female die on the top. With this application they would need to be reversed so that the male die is on the top and the female die is on the bottom. Why is this a problem - the female die is longer than the male die, so my table no longer sits "flush" with the dimple dies in this reversed state.
So the combination of the trap door interference and the reversed setup of the dimple dies on my C-Frame table presented some challenges:
Here you can see the female die sitting very proud of the table
And here are the pics with all the dimples set in both parts:
I also finally called my tech counselor Jim Elliot ad he came out for another visit to help me finalize plans for the mod to the Leading Edge. I think I now have all the info that need to be brave enough to drill the final rivet and nut plate holes in the skin and the subskin, so that I can take it off the wing spar and make that all important cutout. More on that visit and the next steps for that tomorrow.
KPR
Tuesday, January 9, 2018
Tech Counselor Visit and more Fuel Tank Rib Fabrication
Had a little lull over the new year holiday - cold temps, getting sick, holiday obligations - blah! Nice to get back to airplane building for a change. Picking up where I left off, per Vans input about the hinge for the trap door assembly I decided to do the same - leave the rear hinge pin bent to 90 degrees and leave a small amount of excess on the other side of the hinge without bending it or peening it, etc. The idea is that the rear hinge pin will hit up against the rear baffle plate without ever coming out of the hinge, as long as there is a sufficient amount of pin left on the other side to keep from coming out or causing the hinge to hang up.
So I straightened the bent part of the hinge pin a bit more to keep that end from binding against the eyelets of the hinge, and then I made a mark on the other end after setting the bent end along the rear flange of the rib, simulating where it would hit the rear baffle plate:
Then I cut the hinge with the dremel tool cutting wheel and deburred the end on the scotch brite wheel:
The piece of metal sticking up one the left is actually a reinforcement plate that goes on the forward part of the most inboard and outboard ribs. In this case it served quite well as a mock baffle plate so that I could verify the length of the hinge pin was correct.
Next came the cover plate for the open hole also seen in the above pic. Vans says that with the flop tube assembly this hole also needs to be covered with a patch plate so that fuel is only allowed through the trap door location. of course this is NOT in the instructions or the plans, so it begs the question, if someone was building the kit with very little or no outside help, they would never cover up this hole. How would they know f they needed to. Vans once again fails to impress me with its lack of updates to the plans of its older models that are still being built and flown. The hole is about 1.5 inches wide, so I reasoned that a 2 inch square patch plate over this hole with 4 AN426AD3 flush rivets in each corner should doe the job. this allows me to maintain 1.4 inch edge distance at each corner of the patch plate:
I cut the plate from scrap .025 inch thick aluminum sheet and deburred it on the scotchbrite wheel. then marked the location for the plate over the hole in the rib, as well as the location for the 4 rivet holes as shown above.
After drilling the 4 rivet holes in the plate, I had to match drill the holes in the rib. So I used the clamps to secure the plate on the rib and got that all done. then I deburred all the holes:
Now I get to decide which side of the rib to mount the plate. the general idea for this is that you want to put the plate on the side of the rib that might encounter the most force due to the amount of fuel in the bay at any given time. I need to decide this because I am using flush rivets to mount this thing. It is not structural so there is no need for AN470 rivets for this, and I am also trying to minimize the amount of space taken up by things other than fuel inside the tank. A rivet seems like a minute detail, but it all adds up in the end - excess sealant, excess hardware, excess rivets, and so on...... It all means less fuel in the the tank.
Since I am using AN426 rivets I will need to dimple the skins, and I have to decide which side of the rib I want to do this.
This past weekend I had my technical counselor Jim Elliot come out again to review my plans for the cutout of the leading edge skin. He was satisfied with my planned approach. So now I am almost ready to remove the LE and make the big cut. In the coming weeks you will finally start to see what I have been planning to do all along. To think of all the research, design work, and safety evaluations I have gone through to make this seemingly rather small mod makes my head hurt. So I'll leave it at that for now.
My big problem now is that I have the fuel tank in prep mode in my only LE cradle, so in order to take off my LE I have to figure out what to do with the fuel tank. I think I may be making another cradle this weekend to give me some flexibility with handling these big parts. Not really a big problem, just yet another one that I have to deal with on this never ending journey...
KPR
So I straightened the bent part of the hinge pin a bit more to keep that end from binding against the eyelets of the hinge, and then I made a mark on the other end after setting the bent end along the rear flange of the rib, simulating where it would hit the rear baffle plate:
Next came the cover plate for the open hole also seen in the above pic. Vans says that with the flop tube assembly this hole also needs to be covered with a patch plate so that fuel is only allowed through the trap door location. of course this is NOT in the instructions or the plans, so it begs the question, if someone was building the kit with very little or no outside help, they would never cover up this hole. How would they know f they needed to. Vans once again fails to impress me with its lack of updates to the plans of its older models that are still being built and flown. The hole is about 1.5 inches wide, so I reasoned that a 2 inch square patch plate over this hole with 4 AN426AD3 flush rivets in each corner should doe the job. this allows me to maintain 1.4 inch edge distance at each corner of the patch plate:
After drilling the 4 rivet holes in the plate, I had to match drill the holes in the rib. So I used the clamps to secure the plate on the rib and got that all done. then I deburred all the holes:
Since I am using AN426 rivets I will need to dimple the skins, and I have to decide which side of the rib I want to do this.
This past weekend I had my technical counselor Jim Elliot come out again to review my plans for the cutout of the leading edge skin. He was satisfied with my planned approach. So now I am almost ready to remove the LE and make the big cut. In the coming weeks you will finally start to see what I have been planning to do all along. To think of all the research, design work, and safety evaluations I have gone through to make this seemingly rather small mod makes my head hurt. So I'll leave it at that for now.
My big problem now is that I have the fuel tank in prep mode in my only LE cradle, so in order to take off my LE I have to figure out what to do with the fuel tank. I think I may be making another cradle this weekend to give me some flexibility with handling these big parts. Not really a big problem, just yet another one that I have to deal with on this never ending journey...
KPR
Thursday, December 28, 2017
Called Vans again to get answers to yet more questions about fuel tanks
Q: How to finish securing the the trap door hinge pin?
A: They just bend one side of it (the side toward the rear of the rib, like I have already done). They depend on the joint between the rear baffle and rear rib flange as a hinge stop and don't even bother bending the other half.
Q: How to fabricate the rear-most anti hangup bracket for the flop tube assembly? I asked because the small drawings were not clear how this was supposed to be designed, and they do not provide any instructions for it either.
A: you can twist/bend it so that the face of the bracket is properly oriented on both the stiffener and the rib web. they said that using an "angle" is probably overkill. So attach one end to the stiffener and then twist/bend it forward enough so that the other end of the bracket is properly oriented 90 degrees from the other end.
Q: What thickness material and rivets to use to cover up the t-704 hole in the rear web of the first inboard tank rib. Needs to be done since all main fuel flow into this bay of the tank is supposed to be controlled ONLY by the hole in the lower rear of the rib where the trap door resides.
A: Use whatever scrap you have and put 4 rivets of your choosing to permanently cover with no proseal or anything - just cover that hole so the majority of the fuel entering that bay must come through the bottom hole with the trap door.
There are several other smaller tooling holes in the rib that will also allow fuel to move through them, but they are so small that they shouldn't matter much.
Q: Use the tank dies or no?
A: Says you are supposed to use the tank dies on the ribs, and the regular dies on the skins.
I don't think this is correct per Mike at Cleaveland Tools - I told the guy at Vans about a video that MIke had finally produced where he attempts to cover the proper use of the substructure dies, tank dies, and regular dies. I need to review that video again and make my final decision about which dies to use on which parts.
Q: Proper washer placement for the AN fittings for the flop tube?
A: There is no spacer(washer) placed on the T-405 tank attach bracket because that part already basically serves as a spacer since it is 3/16ths of an inch thick. So I just need to fab the part, cut small recesses in it where the rib flange/skin rivets are located around the very front of the rib, place the nut on the part and mark the rivet hole locations as best as possible to ensure clearance around the nut so that it can be secured with a wrench later on, and the nut is the only thing that rests against the face of the attach bracket.
Then my friend Mike Rettig supplied me with a few more answers to some Proseal questions:
Q: Buy and use the 1/2 inch wide x 1/16th inch deep spouts for the SEmco tubes to apply a coat on each rib web, or just use the circular tube tat comes with each tube?
A: Just use the circular applicator tube that comes with each tube, apply the bead on the rib flange only, and NOT the skin, and use a pop sickle stick or other applicator to spread it evenly across the width of the flange.
Then attach the ribs to the skin per Rick Gialotti's faying method as posted in VAF.
SO to finish up the trap door tomorrow I will shorten up the other end of the hinge pin, smooth it out, and proceed with making the cover plate for the other hole and riveting that in place.
A: They just bend one side of it (the side toward the rear of the rib, like I have already done). They depend on the joint between the rear baffle and rear rib flange as a hinge stop and don't even bother bending the other half.
Q: How to fabricate the rear-most anti hangup bracket for the flop tube assembly? I asked because the small drawings were not clear how this was supposed to be designed, and they do not provide any instructions for it either.
A: you can twist/bend it so that the face of the bracket is properly oriented on both the stiffener and the rib web. they said that using an "angle" is probably overkill. So attach one end to the stiffener and then twist/bend it forward enough so that the other end of the bracket is properly oriented 90 degrees from the other end.
Q: What thickness material and rivets to use to cover up the t-704 hole in the rear web of the first inboard tank rib. Needs to be done since all main fuel flow into this bay of the tank is supposed to be controlled ONLY by the hole in the lower rear of the rib where the trap door resides.
A: Use whatever scrap you have and put 4 rivets of your choosing to permanently cover with no proseal or anything - just cover that hole so the majority of the fuel entering that bay must come through the bottom hole with the trap door.
There are several other smaller tooling holes in the rib that will also allow fuel to move through them, but they are so small that they shouldn't matter much.
Q: Use the tank dies or no?
A: Says you are supposed to use the tank dies on the ribs, and the regular dies on the skins.
I don't think this is correct per Mike at Cleaveland Tools - I told the guy at Vans about a video that MIke had finally produced where he attempts to cover the proper use of the substructure dies, tank dies, and regular dies. I need to review that video again and make my final decision about which dies to use on which parts.
Q: Proper washer placement for the AN fittings for the flop tube?
A: There is no spacer(washer) placed on the T-405 tank attach bracket because that part already basically serves as a spacer since it is 3/16ths of an inch thick. So I just need to fab the part, cut small recesses in it where the rib flange/skin rivets are located around the very front of the rib, place the nut on the part and mark the rivet hole locations as best as possible to ensure clearance around the nut so that it can be secured with a wrench later on, and the nut is the only thing that rests against the face of the attach bracket.
Then my friend Mike Rettig supplied me with a few more answers to some Proseal questions:
Q: Buy and use the 1/2 inch wide x 1/16th inch deep spouts for the SEmco tubes to apply a coat on each rib web, or just use the circular tube tat comes with each tube?
A: Just use the circular applicator tube that comes with each tube, apply the bead on the rib flange only, and NOT the skin, and use a pop sickle stick or other applicator to spread it evenly across the width of the flange.
Then attach the ribs to the skin per Rick Gialotti's faying method as posted in VAF.
SO to finish up the trap door tomorrow I will shorten up the other end of the hinge pin, smooth it out, and proceed with making the cover plate for the other hole and riveting that in place.
Tuesday, December 26, 2017
Riveting the Trap Door
Here is a pic of the lower hinge assembly with the trap door riveted in place. I used my manual rivet squeezer for all the rivets due to the slippery nature of the hinge metal and the tight quarters that the squeezer needed to fit into, requiring a bit more control than if using the pneumatic squeezer.
The rivet on the left was the first one that was set, and of course, this being the first rivet I have set in quite a while, it naturally got messed up and I had to drill it out an reset another one. In the process of that the ends of the door next to that rivet bowed a little bit, and so even the replaced rivet is not very well set. Thoroughly aggravated by this, I decided to leave it alone before I caused any more damage to everything.Here is a blurry view of the bottom side. this actually turned out OK.
And here are the flush sets that I used in the hand squeezer with a standard 3 inch Yoke:
I used the larger 1/2 inch wide by 1/8 inch thick flat set against the manufactured head of all rivets, and the smaller 3/8 inch wide by 1/2 inch high flat set for all shop heads. I did it this way to ensure that the set would not accidentally end up hitting the hing rings, deforming them so that the pin would not rotate freely. This worked OK except for that very first rivet.
For the top hinge rivets, I was able to set the first one relatively easily, but the second one required the use of my bench vise, and a spare piece of wood that would fit inside the the flat part of the rib web surrounded by the stiffener ring on the outside. I need both hands to ensure that the rivet sets would be positioned properly and not screw something up - like smashing the stiffener ring, thus ruining the entire rib and forcing me to start over.
While I did not get a pic of it clamped to the vise, here are the pieces that were positioned onto it. The vise was lightly clamped, just enough to secure the rib so that I could position the squeezer and set the rivet.
Here are the shop heads - you can see how close the one is to the edge of the stiffener ring to get an idea of just how tricky it was to position the squeezer to set the rivet.
And here is the other side with everything riveted together:
Now, can you see my next dilemma? I still have to decide how to "secure" the other side of the hinge. This turned into yet another head scratching moment, and caused me to wonder of I should have trimmed and bent the other side of the hinge pin before I riveted everything in place. Unfortunately, I did not do that. Now I have to figure out how to accurately bend this pin with everything now tightly secured to the rib web.
This revelation led to yet another interesting observation. It involves a decision about how tightly or loosely to leave the other side of the previously bent hinge pin, and the same question for the bend to the pin on the other side. too much lay will allow the pin to slide from side to side a certain amount, and over time this would run against the rib web and/or the proseal in a very critical area of the tank that is very prone to fuel leaks as a result of it not getting sealed enough in the corner between the rear rib flange and the other rib flanges. It could even start scratching against the rib web, and I have already seen some evidence of this.
But none of these things was as disturbing to me as what I discovered while checking for freedom of movement of the door. Sometimes the door would not open when the rib was in a position where the gravity should have caused the door to open easily. A closer inspection revealed that this would happen when the 90 degree bend in the hinge pin would get forced very close to the first hinge rung that it encounters. This was effectively locking the door in place, not allowing it to open, similar to this next pic - and this is NOT good.
A closer inspection of the pin revealed why this is happening:
The pin is not bent at a perfect 90 degree angle. There is a slight amount of bend on the pin just prior to where it actually bends 90 degrees, and this bend is slight enough to allow it to be inserted into that first hinge rung if that end of the pin has any force exerted on it.I think I can try to straighten it a bit where it won't be as much of an issue, but the problem is you are just trading one bend for another one - that one being the 90 degree bend in the pin. Now matter how hard you try, there will still be a potential situation where that end of the pin with the bend in it can cause friction when forced up against the rung in the hinge.
So right now I have mixed feelings about this, and they consist of everything from abandoning the entire flop tube assembly to doing the "best I can" with the hinge pin and not worrying about it too much. Whatever I decide to do, I just do not want to ever run out of fuel for any reason unless I intentionally want to drain tank completely for some reason.
I could not get the pic to focus properly, but you can still see the small bend in the straight part of the pin just before it gets to the 90 degree bend. I have some small hobby pliers that I think I can use to remove that small bend on that side of the bend and complete the bend on the other side as well.
What a pain - and look how much this has time sucked the build - all for a little door in a rib - crazy.
For the top hinge rivets, I was able to set the first one relatively easily, but the second one required the use of my bench vise, and a spare piece of wood that would fit inside the the flat part of the rib web surrounded by the stiffener ring on the outside. I need both hands to ensure that the rivet sets would be positioned properly and not screw something up - like smashing the stiffener ring, thus ruining the entire rib and forcing me to start over.
While I did not get a pic of it clamped to the vise, here are the pieces that were positioned onto it. The vise was lightly clamped, just enough to secure the rib so that I could position the squeezer and set the rivet.
This revelation led to yet another interesting observation. It involves a decision about how tightly or loosely to leave the other side of the previously bent hinge pin, and the same question for the bend to the pin on the other side. too much lay will allow the pin to slide from side to side a certain amount, and over time this would run against the rib web and/or the proseal in a very critical area of the tank that is very prone to fuel leaks as a result of it not getting sealed enough in the corner between the rear rib flange and the other rib flanges. It could even start scratching against the rib web, and I have already seen some evidence of this.
But none of these things was as disturbing to me as what I discovered while checking for freedom of movement of the door. Sometimes the door would not open when the rib was in a position where the gravity should have caused the door to open easily. A closer inspection revealed that this would happen when the 90 degree bend in the hinge pin would get forced very close to the first hinge rung that it encounters. This was effectively locking the door in place, not allowing it to open, similar to this next pic - and this is NOT good.
A closer inspection of the pin revealed why this is happening:
The pin is not bent at a perfect 90 degree angle. There is a slight amount of bend on the pin just prior to where it actually bends 90 degrees, and this bend is slight enough to allow it to be inserted into that first hinge rung if that end of the pin has any force exerted on it.I think I can try to straighten it a bit where it won't be as much of an issue, but the problem is you are just trading one bend for another one - that one being the 90 degree bend in the pin. Now matter how hard you try, there will still be a potential situation where that end of the pin with the bend in it can cause friction when forced up against the rung in the hinge.
So right now I have mixed feelings about this, and they consist of everything from abandoning the entire flop tube assembly to doing the "best I can" with the hinge pin and not worrying about it too much. Whatever I decide to do, I just do not want to ever run out of fuel for any reason unless I intentionally want to drain tank completely for some reason.
I could not get the pic to focus properly, but you can still see the small bend in the straight part of the pin just before it gets to the 90 degree bend. I have some small hobby pliers that I think I can use to remove that small bend on that side of the bend and complete the bend on the other side as well.
What a pain - and look how much this has time sucked the build - all for a little door in a rib - crazy.
Subscribe to:
Posts (Atom)