Drillled and Tapped Pitot Tube and Mast

Man the last two days have been nerve racking. Most people write about these steps in their builders logs as though it is no big deal, but for me this task has to rank up there with all the tasks that I absolutely cannot stand  about this project - which includes the task of drilling raw holes in round or awkward shaped materials. I absolutely hate having to figure out how to jig, clamp, align, and whatever else that has to be done to do this right. You know, all the gory details that nobody ever seems to talk about in their build logs.

For starters, the shortest screws I could find locally were 3/8 inches long, and I really needed 1/4 long mounting screws. The solution - A dremel tool with a cutoff wheel, and a clamp. I started out by using one of my plastic squeeze clamps, holding it in one hand with the dremel tool in the other. This worked great - right up to the point that the heat from the screw started melting the plastic holder. So I stopped that foolishness to think of another way to hold these screws so I could cut off the last 1/8 inch. I have done this numerous times when building RC airplanes over the years, so this technique was nothing new to me - just that the length of the screw was  a bit shorter than I was used to working with. What I finally came up with was using 2 thcik wood blocks, adn inserting the screw head in between each block and clamping it tight in my table vise so that the screw head would mash down slightly into the wood. This made a stable way to use the dremel to cut off the ends of each screw. I then got out an 1/8 inch thick piece of aluminum from my trim bundle, and drilled and tapped the same hole that I was about to drill and tap in the real thing. At least I remembered to do something right. That all went as expected, and after a small amount of filing on some of the freshly cut screw ends, each of the 4 screws inserted cleanly into the threaded hole.

Now to drill the holes in the assembly. Silly me thought that I had it all figured out. TO do this right, it requires drilling somewhat precise holes, so that meant it was time to use the drill press for this. UNfortunately that means clamping and positioning the table in just the right spot so that the hole is drilled correctly. Here is a shot of my arrangement, complete with wood blocks, a drill clamp, and my #40 drill bit with a drill stop positioned so that it drill no larger than a 1/4 inch hole. It all looks pretty lined up too.....

By the time I had taken this pic, I had already drilled the two rear holes. That worked out ok, except for one thing that I will show in a bit. For the rear holes, the assembly was able to be clamped solidly into position without moving. To amke things a bit easier, the rear holes are drilled in a location where there is very little curvature to the assembly. However, from the above pic, you can see that when you drill the forward holes, this becomes a bit of a challenge. What I found was that the assembly would not clamp down tight in this position duw to the extreme curvature of the mast. Instead, the forward face of the assembly kept riding up on the wood block with each turn of the clamp handle. The one thing that it was doing was placing the assembly at the correct angle for the drill bit. It worked great for that. I thought I could just hold the part steady with my left hand while I ran the lever on the press to drill the hole.

I should also mention that I set the stops on the drill press in addition to using a drill stop on the drill bit to ensure that I would not drill the hole too deeply. I also secured the mast and the tube with gorilla tape as shown in the above pic. SO, everything was in good shape, right? WRONG. As soon as I turned on the drill press the clamp vibrated lose and the assembly would shift out of position. So much for that idea. I was not about to spend frickin hours making a jig that holds the pitot in just the right position to drill these stupid holes.

Too bad, because it sure looked like it would work great - here is another pic - everything looks spot on lined up. Note the angle of the pitot tube that is required to drill a straight hole through the mounting material in the inside of the pitot tube.

So at least I had the good sense NOT to try to drill these holes using this method. I stopped for the night so I could rethink this and figure out what to do.

So shift forward to today. The next pic shows what I basically came up with - take the assembly outside to the vise, clamp it upright against the two wood blocks, put the #40 drill bit in my cordless drill with adjustable speed trigger, lined up the angle as best I could, and drilled the first pilot hole. Then I turned it around and did the same thing on the other side. I did NOT use my air drill for this - the trigger is too unpredictable and hard to control. I needed to start this slow and keep the drill steady all the way through.

After that was done I changed drill bits to a #36, and drilled through each hole again to get to the correct size for tapping the 6/32 threads for the mounting screws. Then I ran the tap through each hole. In short, I free-handed the stupid holes. Other build sites I have visited where folsk are using their drill press actually don't seem to be doing much better than me. Several of them show holes that are drilled that are not really at the correct angle as determined by the aluminum flanges on the inside of the pitot tube. WHne you see the screws being inserted in the pics it clearly shows that the holes are not aligned correctly with the face of the mast.

For the #36 drill bit as well as the 6/32 tap, I used some electrical tape wrapped around the shaft to serve as a drill stop of sorts so that I would not risk drilling into the stupid air lines in the pitot tube. The rear holes are no problem, but the forward holes will get you into trouble if you run the drill bit too deep.

The above pic hints at my next problem. A couple of the holes were bottoming out on the tap - the reason - the hole was not drilled quite deep enough for the tap. A quick look at the tap revealed the problem. The tip of the tap barely has any cutting threads on it, and tapers off quite sharply at the tip. This basically means that the tap probably requires at least 1/16" more distance to allow the cutting threads to properly seat in the material all the way through the hole. I thought I had this all worked out by just continuing to run the tap alittle bit further, that is until I got to the forward hole on the left side.

The other holes had been drilled all the way through the aluminum flanges on the inside of the pitot tube - all of them except the one on the left front hole. When I tried to torque the tap a bit further in that hole, all of sudden it just let go - no threads, no resistance. Yup, I managed to strip the #$%&;^&;*^% hole! What an ass I am sometimes. That was about as stupid as it gets.

Out came the #36 drill bit to finish drilling through the material, and then I reran the tap through the hole. Bottom line is that this hole only has about 1/8 inch or less of viable threads that are actually grabbing and securing this screw - not good. But at least it does grab. Something tells me that before this is all done I will probably be resizing that hole for a #8/32 screw.

And now for the finished masterpiece. The left side with mounting screws inserted..... and NO I am NOT going to go through the trouble of countersinking these stupid things. Enough is enough already. I'll take the drag penalty.

...and then the crappy looking right side.

Note the mis-aligned screws. The sucky part is that this actually happened on the drill press. I must not have had the first rear hole lined up in quite the right spot, and so it got drilled slightly lower than where it should have. The other 3 screws are relatively lined up with each other. This is purely cosmetic, but pisses me off jsut the same.

SO there you have it. IF anyone can royally screw up such a simple task, it is surely me. At least the damn thing is drilled and mounted. I can't wait to see how bad I can screw up the mounting the mast to the wing spar - stay tuned for that episode of dumb and dumber.

OK, I need to go cool off now, this has been an exhausting and disappointing couple of days. I bought a "kit" for a reason. If I would have wanted to spend all my tine laying up undrilled holes in all sorts of wildy contorted non-linear objects, I would have built it from scratch. For me, this process ranks up there in the top 5 things about this project that I hope I never have to do again. I sure hope that I did not drill too far into the pitot and either scar the tube or puncture it outright. Initial "blow" tests through the line seem to indicate everything is working correctly, but only time and repeated wear and tear will tell, since you can't see any of the tubing buried underneath the silicone deep inside the pitot tube....

Deburring Rib holes and Marking Pitot Tube Mounting Holes

Well I was finally able to stop researching and get out in the shop to do a little metal work for a change. A rough few weeks at work, weather, and a head cold have kept me pinned down a bit, but tonight I was able to do a few small things.

First, I was able to debur almost all the holes I had previously match drilled in the main ribs where they slide underneath the main wing spar flange. I deburred both inside and outside holes f the wing spar as well as the ribs. Now I just need to finish drilling and deburring all the wire run holes and hopefully I can move on the prepping them for primer.

Then I decided to perform the steps to mark the hole locations for the pitot tube mast. Neither the pitot tube nor the mast holes are drilled at all, so you must locate, mark, drill, debur, and tap the holes.

1. mark the center of ech screw mounting point of ghe pitot tube. This is identified by the 4 thicker areas of aluminum that protrude deeper into the top face of the pitot tube as shown below:

2. Carry the line down the side of the pitot tube and continue the line past the point where the pitot tube base widens out.

3. Measure the height of the recess in the pitot tube to the top of it. Mine measured about 22/32. I then took half of that value, or 11/32, and marked the pitot and mast accordingly. This will effectively put all the mounting screw at the halfway point of the mounting flange of the pitot tube.

4. Slide the pitot mast over the pitot tube. I also used electrical tape to fill the slight gap between the outer edges of the pitot tube and the mast - this is typical of the pitot and mast that I am using. Some use electrical tape and others use heat tape. All you are trying to do right now is get the pitot tube to snug up against the wall of the mast so you can drill accurate holes through both of them.

5. Transfer the vertical lines onto the mast, and then measure the 11/32 from the end of the mast on both sides and draw the intersecting line on each side of the mast.

I center punched the hole locations on the mast and decided to stop there for the night. My plan is to gradually upsize the hole to make sure that it maintains the correct angle based on the mount points built into the pitot tube. The last thing I did was to reposition the drill stop on my #40 drill bit to just over a 1/4 inch. The mounting screws can not really be any longer than that,or you risk drilling into the actual air lines or heating element inside the pitot tube. You can order either countersunk or pan head screws from ACS, or I was able to find some 3/8 inch long, 6/32 pan head stainless steel screws at  local hardware store that I plan to use for my setup. Lots of folks go ahead and get countersunk screws for this, but I just did not want to go through the trouble. Neither of the screw types sits absolutely flush to the round pitot mast, so I am ok with just using the pan heads for now.

And lastly a shot of the electrical tape wrapped around the mounting flange of the pitot tube:

The tricky part of all this is drilling the holes at the correct angle and depth. I plan to use my drill press for this so I can clamp the work at the correct angle and ensure that the drill bit will maintain a straight path into the tube. Will try to do all that tomorrow.

Researching Lights and Pitot Tube Placement

After receiving my new Dynon Heated Pitot Tube I started researching the placement of the pitot  tube in the wing, and looked at several builder sites to see exactly where they placed the pitot tube, and how they routed the airlines and electrical wiring for the heat controller. As I was doing this, I had a revelation of sorts that kind of concerned me just a bit. The reason is that it seems that most builders using the same components that I am using are locating their pitot tubes in the bay just OUTSIDE of the location that Vans uses for the stock pitot tube. The reason is that the location for Van's stock tube is in the same bay where the aileron push/pull tubes and the aileron belcrank are located, not to mention a possible autopilot servo and all the associated wiring that goes with it.


In short, this is a very busy and critically important bay in the wing that houses some of the most critcal flight components of the aircraft. So anything that may interfere with those components is a serious potential hazard. The stock pitot from Vans works in this location because it is nothing more than a length of 1/4 inch aluminum tubing bent to shape and mounted through a hole in the bottom main wing spar flange, and then routed through the holes in the main wing ribs back to the fuselage. It is mounted to the bottom spar flange so it is out of the way of the push/pull tubes and the belcrank. Unfortunately, a pitot tube such as the one I am planning to use will have to be mounted in such a way that placing it in this same bay could cause several different problems, none of which I am willing to expose myself or my eventual passengers to.



The general thought is to move the pitot further out on the wing to ensure that airflow from the fuselage does not introduce airspeed indication errors due to disruptions caused by the fuselage or the landing gear, etc.

All that said, positioning the pitot tube further outboard under the wing also creates a new problem. The problem can occur when the time comes to tie down the aircraft at your destination airport, either for a fuel stop or as you final destination. To do this, you have to rely on the tie down spots that have been positioned by each airport's FBO. The placement of these tie downs is up to the discretion of the airport operator, and is usually based on the types and even the makes and models of aircraft most frequented at the airport.



As I reviewed the plans, I started to realize that if I move the pitot tube to the next bay outward, there is a risk of a tie down rope coming into contact with the pitot tube. This is because the ties down ring will end up being inside of the pitot tube. I submitted a post to VAF to ask for photos from folks with a similar installation that shows the positioning of a typical tie down rope and the pitot tube after the airplane is tied down. What I found is that there is definitely a possibility of the rope interfering with the pitot tube and damaging it or even a part of the wing in the process, unless the wing tie down rope is positioned slightly forward. This may or may not be possible from one airport to another, and depends on several factors, such as position of the tie downs on the airport in relation to each wing tie down ring on the RV, and the position of the tail tie down point. The pictures sent to me in the VAF post pretty much tell the tale.



So, now the question is, what to do about this, if anything. Luckily today I think I arrived at a solution, while not perfect, is good enough for me and is one that I will implement when the airplane is ready to travel. Basically, what needs to be done is to find a way to extend the tie down ring a little bit more, so that the ring is just a bit lower than the lowest point on the pitot tube. The tie down rings are simply standard 3/8 inch eye bolts thatr are usually 2 inches in length. I googled for eye bolts to see if I could find some with longer shaft lengths that the typical 2 inch long ones at the local HD airplane store.


As luck would have, the first link in the search results returned a company that deals in exactly that, all sorts of different sizes and configurations of all types of different eye bolt applications. Therefore, my plan will be to carry these slightly longer eyebolt extensions with me on the plane, and any time I have to tie down at an airport where I have to be concerned about the clearance of the tie down rope or chain with the  pitot tube, I will just insert the longer eye bolts, and the problem should be solved.

Now I can proceed with installing the pitot tube in the outer bay without worrying about the tie down problems.



I have also spent some time reviewing lighting solutions. Duckworks has a lot of my attention right now, in addition to Aveo and AeroLED. I am starting to wane from any interest in AeroLED because they appear to be posturing themselves as a bonafied certified aircraft shop, with the experimental market as an after thought. Unfortunately the prices for their LED light solutions are also representative of that situation, and I am far from interested in spending 2000.00 + for a stupid outside light solution for this airplane. That is just absolutely absurd and rediculous, and anyone that pays that kind of money for something like that ought to be ashamed IMHO. I'll have more on the lights later on.

Aux Tank Inspection cover and Bung kit arrives

Received the external fuel tank access/inspection cover kit and the bung kit the other day from SafeAir1 . I just could not resist this bit o' fun by taking this rediculous robotically themed photo to show off the parts in the kits. The two round robot "eyes" are the bung flanges that will mount to the outboard ends of both main fuel tanks to provide the inlet from the aux tank into the main tank via the fuel transfer pump. The remaining robot parts are the back plates and cover plates of the additional inspection/acces panel that will be cut into the leading edge of the wing.

Next I set out to determine where to install the pitot tube. The builder is left with some decisions to make when deviating from the plans, but many folks have done this same thing prior to me so I am sure to make the right decision. One of the first decisions was deciding to keep the full length of the air lines extending from the pitot tube or not. They are too long to leave "as is" so you either have to bend them over or cut them down a bit. They also require you to flare the ends to accept the AN NPT hardware used to attach the colored lines from the SafeAir1 plumbing kit to the pitot tube.

UNfortunately I had never flared a metal tube in my life, so before I ruined the real thing, it was time to practice. I already puchased the Parker Rolo Flare Tool, and with te help of the instructions, I found some 3/16 inch OD aluminum tubing from K&S Engineering at the hobby shop to practice with. Although the OD diameter of the tubing is the same, the ID dimension is very different. The hobby shop tubing is very this walled - .014 inch thick aluminum, whereas the tubing on the pitot tube appears to be a bit thicker. Further research revealed that the hobby shop tubing is 3003 H14, while I think that the tubing they used for the pitot tube is 3003 0. Same alloy but a different hardness and thickness. The pitot tube appears to be a bout .025 inches thick.

My first attempt at flaring the ends "ended" in disaster - obviously I had to practice with this tool. It does not take much to create a good flare, ans since I was using tubing with a much thinner wall than the on the pitot tube, it was even more difficult to get a good flare without cracking the tubing. Here are some pics of my practice results after I finally got the hang of this tool:

First is pics of some tubing I found at Lowes airplane parts:

And next is the flaring tool. You have to purchase one similar to this because all aviation flares are made at 37 degrees. All automotive flaring tools are set to 45 degrees, and will not work with aviation-grade NPT plumbing hardware.

The above pic shows a locking flange in front of the hole where the tubing goes, butted up next to the business end of the tool that creates the flare as it is rotated inside the tubing. The locking flangen the left of the pic sets the correct depth of the tube by pushing the end of the tube until it hits this flange. Then, when the toll is locked into position, the locking flange slides out of the way of the flare bit, and you crank it down into the hole in the tube to create the flared end.

Here is a pic with the flange moved slightly out of the way:

And then finally the results of my practice attempts. The pics are blurry - could not correct that for some reason:

the last pic attempts to show some slight bumps on the outside edges of the flare. These were caused by the separation of the top and bottom dies, which are split in the middle. I am not sure if this means that I need to tighten down the dies a bit more, or if this is considered normal. The AN hardware fitting in the pic above that one seems to seat itself just fine. Problem is, you want to make absolutely sure that these are done correctly, or you will end up with leaks and possible failures - which is not good.

All in all I was satisfied with the results but it definitely has a certain feel to knowing when to stop cranking down on the flare bit, adn the prep on the end of the tube is absolutely critical as well. Any burs on the end will most definitely end up with a cracked flare, so care must be taken there as well. It was cool to see how this tool works.

Next post I will talk about my efforts to practice bending 3/16 inch soft aluminum tubing to shape with another bender tool I purchased. That experience was not as good as this one was - and I am not real happy with the claims made by the bending tool that I purchased that it will handle 3/16 inch tubing. After my experience I think that is a bunch of crap. Anyway, more on that tomorrow.

Pitot tube arrived!

I got my Dynon Pitot Tube today. I consider it an early birthday present, and easter present, and christmas present......well, you I am sure you get the idea. It comes with a microprocessor-controlled heat controller unit that will also be mounted somewhere in the wing. I think this is the unit that some folks are mounting on the inside of the inspection cover so that it is easily accessible for servicing/repair/or replacing as necessary. Of course the pitot tube itself also needs to be serviceable as well. Here is the pitot and the controller unit:

The long tubes coming out the top are 3/16" OD, and these are the tubes that will have to be flanged to accept the AN hardware fitting that will attach the plastic air lines to the pitot tube. The controller unit is electrically attached to the wiring coming out of the pitot tube, and the other wires are then routed back to the fuselage where a circuit breaker and a switch will complete the circuit. I also found some small 6 inch long 3/16 inch OD aluminum tubing at Lowes so I can practice making flared flanges with my flanging tool. They are not as thick-walled as the tubing in the pitot tube, so it might not work the way I want it to, but at least it will give me something to practice on.

I will need to determine the length to trim the tubes down to so that everything can be mounted correctly to provide proper clearance and security of the air lines. I like Steve Riffe's implementation for this but have also seen a couple of others that I like as well. How willing I am to trim down the tubes will depend entirely on how well I think I can make the flanges without messing them up.

Next is a pic of the tube as it will look after installing it in the mounting bracket:

Pretty sexy, huh? Can't wait to see it on the wing.

I am still waiting on the bung kits for my fuel tanks, and I should have those in a week or so. I still can't get used to calling them that, but that is apparently what they are called. All they are is a couple of flange fittings that will go on the outboard end of the fuel tanks so that if I ever decide to add the extended range fuel tanks I will already have a fuel line attach point from the fuel pump to the main tanks. Next I am going to start focusing my attention on some lights.

Received a Package of Goodies Today

I finally ordered my SafeAir1 Pitot/Static plumbing kit and the Pitot Mast, and both of these arrived in the mail today. I also ordered my Dynon Pitot tube from Steinair. I believe that the pitot tube is supposed to arrive tomorrow.

The pitot mast gets mounted to the bottom left wing skin, in the bay just beyond the inspection panel for the aileron belcrank. The air lines are color coded. Green for the pitot line, blue the angle of attack (if you use it), and white for the static line. You also get a bag of nifty fittings. The airlines just slide into these fittings and they lock in place. Pretty nifty setup as long as it works, but there are probably thousands of folks using this kit in their already-flying airplanes and I have heard hardly anything about any issues with it.

I also managed to match drill the holes in each rib to the spar flanges on both sides. I spent yesterday reviewing a whole bunch of posts about this particular seemingly simple operation. The instructions in the manual tell you to match drill ALL of the attach points of the ribs to the main spar web, and the builder must assume,since they do not call specific attention to it in the manual, that this includes the 4 holes on the top and bottom forward section of each rib that slide underneath the main wing spar flanges. Then they tell you to remove, debur, scuff, clean, and prime the ribs. Only problem is that these top and bottom rib-to-spar flange holes are the most forward attach points for all of the wing skins, and when you fit the wing skins to the frame the one thing that you are trying to do is get them to line up nicely to avoid any gaps between the main wing skins and the leading edge skins, etc. SO the typical preferred thing to do is to attach all the parts, including the wing skins, with clecoes and then match drill through ALL the layers at one time, including the wing skins, so that the holes are all truly matched to each other.

One question that arises from this centers on the fact that if you match drill the wing skin-to-spar-to-rib holes WITHOUT having the skins on the frame, as the instructions imply, you might not get a proper match hole in the wing skin if you finish match drilling them to the frame AFTER the ribs have been riveted to the spars. If you match drill only the ribs and spar flange holes first, without match drilling the wing skins, and then prep and rivet the ribs to the spars, you risk not getting a good matching hole fit of the wing skins. So the issue for this is if you should attach the frame and skins entirely with clecos and THEN match drill all the holes together, or should you wait until after the ribs are match drilled and riveted to the wing spars before you fit and match drill the skins, having already match drilled the holes in the spar flange and the rib? Clecos are a bit more flimsy, and may cause flexing or twisting of the parts, whereas rivets would not allow as much of this to occur, so the better option for fitting the skins is to have the frame solidly riveted in place, which is consistent with the way that all other skinned parts have been put together up to this point.

Then next part of the problem is deciding exactly when to match drill the rib-to-spar flange holes. If you rivet the ribs to the spar web, and wait to match drill the top and bottom holes to the wing skins until after you fit the skins to the frame, there is no way to remove the ribs to debur the newly drilled holes in the ribs or the spar flange. So this turns into a large discussion about waiting to dirll these holes until after you fit the wing skins, and risk not being able to debur the holes, or drilling and deburring these holes BEFORE riveting the ribs to the spar and then fitting and match driling the wing skins later.

Turns out different builders are doing it both ways. SO I chose to go ahead and drill and debur the holes before attaching and match drilling the wing skins. I can reduce or eliminate the tendency to mis-align the wing skin holes by back drilling through the rib and spar flange holes that I match drilled tonight, instead of drilling through the wing skins first. To further mitigate these issues, I used my #40 reamer that I got with the tool kit years ago, instead of a #40 drill bit, to keep the holes as smooth and accurate as possible. I did this to try to further reduce the burs around the holes.

I had some problems with inserting a few clecoes in some of the holes, but managed to work through that. Otherwise, all the rib to spar flange holes are now match drilled. I will debur them tomorrow and also mark and drill the additional wire run holes and pitot air line holes through the forward portion of the ribs. Should have more pics tomorrow.

Transferring Wing Parts to Different Staging Areas

I managed to drill the last two conduit holes in the end ribs today, and set out to re-organize some of the parts on my shelves in the garage to prepare for other wing sub-assemblies like the leading edges, fuel tanks, ailerons, and flaps. The main wing skins have been sitting silently on one of my shelves for quite a while now. I am getting anxious to start working on them as well as the leading edges so these things can start looking like wings for a change. There is still a significant amount of work to do before that happens.

I moved the leading edge skins to the same location as my fuel tank skins so I can start working on those as soon as work benches are clear of wing spars and main ribs. I then attached the main ribs to the left wing spar again to prepare to drill and debur all the spar flange holes in each rib. There are two holes per side for a total of 4 holes per rib, times 14 ribs per wing, times 2 wings, equals a total of 56 #40 holes pe wing, or 112 total for both wings.Then you have to double that for total holes to debur since each hole has two sides. I really get depressed when I start tallying up figures like that, because the task always seems so never-ending. If you just stick to one hole at a time then eventually you get through it. Then I still have several more additional holes to drill for wire and tubing runs.

Other than that I spent the rest of today troubleshooting and researching a car problem with the mule that needs some attention. Gotta get the ride ready for Oshkosh, since it IS just right around the corner ya know! Then I had to fix the snow blower so it would be ready for the next big winter blast that comes along. Looks like it will be 70+ degrees around here by week's end. It will be real hard to focus at work this week.

As for the car, I think I need to replace my fan clutch, but it may also involve anything from a tensioner pully, idler pully, fuel pressure regulator, or engine mounts. I just try to look at these things positively as opportunities to improve my engine and systems troubleshooting skills so that I will be able to put them to good use on the plane later on. If I can figure out what is wrong with my car and fix the problem, I should be able to do the same with an airplane engine, or so I hope.

Also need to rastle me up a couple of turkey basters so I can meter the primer more efficiently in my spray gun without making such a mess when the time comes. When my Dynon Pitot tube arrives, I will need to give some serious thought to the mounting locations for everything and the length of the tubes I should use. Some builders are using the full default length, while others are trimming them down in differnt lengths. The bottom line is you want everything to be easily serviceable, and then well secured to prevent movement and fatigue from vibration or impacting parts of the pitot mast or the wing.

So the shop is pretty much ready to rock, and the weather should be getting warmer for the most part. Sounds like time for building and flying to me. Need to get back in the Citabria again but it may be down for another week or two to finish a fairly major wing skin patch job that needed to be done. So who wants to go flying?!

Finishing conduit holes in both end ribs

I removed the end ribs from boths main spars the other evening. I then marked the position for the last conduit hole in each rib, and I still need to finish drilling the holes. Once that is done I will take one of "money pics" of the build. By that I simply mean that there are few times during the build where some fairly interesting pictures are taken. One of those, in my opinion, is the pic that most people take once all the conduit holes are drilled, and they take a pic of the ribs down through the series of holes with the ribs all mounted on the spar. It is another one of those optical illusion pics that I like.

Last night I took the fam to the Jeff Dunham show here in Broomfield at the 1st Bank Center. It was a blast. I first became acquainted with him during first year at Oshkosh in 2009, which turned out to be the 2nd year in a row that he was performing at Oshkosh. I have mentioned before that he also has ties to aviation, having built his own kit helicopter.

He is absolutely one of the funniest and most talented vantriloquists I have ever seen. All the characters were there, Achmed, Peanut, Bubba Jay, Jose, Walter, and Little Jeff. He began the show, titled Disorderly Conduct, with an absolutely hysterical video where all the characters end up in the slammer, getting interogated by Jeff himself. Then he showed pictures from his childhood, and the show was made up of a mix of old and new material. I highly recommend going if you really like to laugh.if you have the chance.

Now for some really wierd and amazing facts that my wife just told me about as she was reading his bio online. He was born 4-18-1962, a day before I was, in Dallas, Texas, same place I was, and was raised by a Presbyterian family, same as I was. How bizarre is that! We could have been neighbors for crying out loud. One big difference is that he grew up as an adopted only child. Of course, he is also a rich and famous entertainer - yet another major difference. Still, it's nice to know we come from the same background.

Back to the build, we had a major snow storm blow through last night so we are now thawing out from that. So not much was done on the build today. I did spend considerable time researching some things in preparation for a rather large parts order I am about to make. Soon on the way to me will be the following:

SafeAir1 pitot/static line kit #1
SafeAir1 Pitot mast kit
Dynon Heated Pitot Tube and controller
SafeAir1 extended range tank bung kit for both fuel tanks.
Additional SB375-4 plastic snap bushings for RG400 antenna coax wire run and additional wire runs at the forward end of each main rib.
Possibly the SafeAir1 Fuel pump access/inspection hatch kit for the extended range tanks

I also managed to drill and debur all the forward flange rivet holes in both the right wing ribs and main wing spar, as well as the underside of the Lef main wing spar. I will still need to do all the holes for both end ribs. I confirmed from VAF posts that the SB375-4 will provide good clearance for the antenna coax. It requires a 3/8 inch hole drilled in the rib for a 1/4 inch ID hole for the wires/tubing, etc. I also need to call Vans again and ask about drilling the rib holes through the main wing spar flanges. Problem is that you have to drill and debur these holes BEFORE you rivet the main ribs to the spar, but the wing skins are not yet final drilled to those holes, which may cause the skins to be offset just a bit. This may effect the alignment/fit of the leading edge skins against the main wing skins, so I want to check with Vans to verify when exactly should I drill adn debur those holes.

I also researched the DuctWorks site and saw that they are selling a new round stle LED wing tip lite kit. Only problem is that they require a separate flash unit to allow them to wig wag, which ductworks apparently does not sell. Aero Led also has some new high briteness LED lights. I like the wing tip light concept because I don't have to saw out part of the leading edge wing skins for a leading edge type of mount, and it makes servicing the lights a bit easier as well, since all you have to do is remove the wing tip or just the lense cover. This makes installation fairly quick and easy I think.

I like the AeroLED lights because they come with wigwag functions build into the lights, so no separate flash unit is required. Still mulling all that over right now. I also saw a recent post of a comparison of LED, Incandescent, and HID light systems. I don't think that LEDs do all that well for distant illumination, but we'll see. I may still go with them because one of the new features of the GRT AHARS avionics is that they provide an option for a night vision infrared detection - not sure if it is literally FLIR based or not, but I figure I could use this feature in addition to whatever my landing lights  do to provide me with as much situational awareness that I need during a landing approach or takeoff at night.

I then did some research on VAF regarding the installation location of the heated pitot tube controller. Some folks are mounting this on the rib just outboard of the last inspection/service palte location on the bottom of the wing, while others are installing it in the end rib or even on an inpsection plate itself. I will most likely put mine out on the end rib for ease of inspection and service, but may also explore the inspection cover installation a bit more. I am less interested in the rib location because I think this location is difficult to both inspect and service if/when the time comes. Others even run it all the way back to the fuselage.

The pitot tube mounting location is yet another decision that has to be made. I will mount it in the next bay outboard of the bay where the aileron belcrank is located. There are two reasons for this:
1. Dynon has some rather long 3/8 inch air line tubes coming out of the pitot tube where the air lines willbe connected and run back to the avionics, and this will provide enough room for them to be bent  and connected to the lines
2. It allows for connection of the air lines so that they can run through a mounting bracket underneath the entire aileron belcrank assembly, with no chance of interference with the bellcrank or the push/pull tubes. This is something that is rather important, if ya know what I mean.

Also need to get up in the rafters and shelves in the garage and start pulling down the aileron, flap, and wing skins - wow - I will have to order the fuselage kit or something to keep those shelves fully utilized!

Hope to have some pics tomorrow.

Drilling Right Wing Rib Conduit Holes

Yesterday I drilled the large conduit holes in the right wing ribs. I basically got lazy and determined the "center" of each hole by eye, without specifically measuring for the center. I think this worked out OK but time will tell.

I marked the center with a center punch, then used a #30 drill bit to drill the pilot hole:

Then I up-sized the hole to 1/4 inch.

Then, just as I did with the left wing ribs, I used a unibit with a 3/4 inch final step to drill the holes to their final size for the conduit. The last step was to take a deburring tool and clean the edges of each hole on both sides of the rib web.

I now have the holes drilled in all but 2 of the main ribs. Those are the end ribs with the attachment bracket mounted so I could test fit the spars on each of the Wing stands. The next step is to remove the spars from the wing stands, remove each of the end ribs, and then mark and drill the same holes in each of them.

Today I contacted Vans for the first time in a long time, to verify how many holes and what size I can drill them to for the forward part of each main rib. All of the W711 ribs have 2 additional tooling holes in addition to a third one that has been enlarged to 7/16 of an inch to allow for the pitot tube routing. I plan to use 2 of these 3 holes for routing the SafeAir1 air lines from the pitot tube to the avionics, which will require a bushing with a 1/4 inch ID hole, and I will possibly open the third hole for an additional pass through for any other wires that may be required in the future. The rear tooling hole will be opened up to allow for a similar bushing for the RG400 coax antenna cable. Long story short, I still have more holes to drill before I can move on to other things. It just never ends.

I also spent some time researching the Grand Rapids HXr AHRS, and the correct plumbing kit to puchase from SafeAir1. I also researched the Dynon Heated Pitot tube and realized I will also need to determine where to locate the heating element. I also recall some information about locating the pitot tube at least one full bay further outboard than Vans plans call for, I just cannot recall the reason for this off hand. this becomes important because the most outboard access plate only provides easy access to the bay where the aileron belcrank is located. Will have to look into that one again I guess.

This is all part of building the airplane from the inside out. The more you are able to plan for and install the internal components of a structure before you close it up, the better. Now if I only knew what exterior light system and autopilot I was going to use I would be all set!

When all the routing holes are drilled and deburred, then I can attach and match drill the holes for the rear spar, and scuff, clean, and prime the main ribs.

Conduit Holes Drilled for Left Wing Ribs

Friday night I managed to drill the Conduit  holes for the left wing ribs. I messed one up so it is at least1/8 inch off center from the others, but I should be able to make that work OK since the conduit I am using is flexible. I will drill the right wing rib holes today. The unibit makes quick work of this. My only concern is that many builders seem to enlargen the holes just a bit more to get them to fit easier, but we'll see how it goes.

In retrospect, there is one thing I should have done differenty before applying my template to mark the holes for the conduit. I should have drawn a difinitive line a specific distance perpendicular to the rib web to more clearly mark the location for the edge of my template, instead of relying on the "edge" of the stiffener depression, which is much less clearly defined. This has resulted in slight varances of the hole alignment from one rib to the next. As I said at the beginning of this process, I was not out for precision, and only time will tell if I really should have applied a bit more attention to detail than I have. I think that either way I slice it, pulling this corrugated conduit through these holes is a major pain in the ass, regardless of what you do. I will be glad when that work is all done.

I spent some time researching VAF, Vans, and Steve Riffe's builders log last night to get some more info about the size of the holes and bushings needed for the RG400 antenna coax that I will use for my Bob Archer wing tip nav antenna, and the pitot lines that will run from the pitot tube back to the fuselage to the necessary avionics locations. I needed to get some specifications for the coax so I know what size hole to drill in the rear tooling holes of each rib. I have to be careful though, because I need to leave the tooling holes in tact to assist with determining the "level" attitude of the ailerons and possibly the flaps against the chord line of the wing, so I need to leave those "as is" until I reach that point in the build.

Steve's site has some really good pics and info about a borrowed solution from other builders to fabricate a bracket that utilizes the attach brackets and harware for the aileron belcrank asembly. This bracket provides a guide that will keep the pitot air lines very close to the web of the main wing spar and away from the actuating arms of the belcrank, and the push rods connecting the joy stick and the aileron. This ensures that the air lines will never come into contact with the moving parts for the aileron or auto pilot servo by routing them underneath that entire assembly. This is a great tip and an easy one at that.

Specs for hole requirements that I was able to find:

Diameter of RG400 coax antenna cable: 3/16 inch (4.9530 mm) (requires at least a 3/16 inch hole and will probably go up to 1/4 inch for ease of pulling it through, so may need 3/8 inch hole for SB375-4 snap bushing

Diameter of SafeAir Pitot/AOA lines: 1/4 inch ( requires 3/8 inch hole for SB375-4 snap bushing - supplied with line kit)

Max diameter Vans says tooling holes can be enlargened to in each rib: 5/8 inch.

My plan:
I am still hedging more toward a grand rapids ADHRS avionics package, and as such I do not plan to use the Dynon AOA solution which requires a separate air line coming from the pitot tube. Grand Rapids calculates the AOA from other information that is evaluated by the ADHRS unit, while Dynon apparently evaluates pressure differential between the aoa and pitot air lines to determine AOA. I am, however, more than likely going to purchase a new Dynon Heated Pitot tube for value and cost reasons, and this unit has both air lines already built into it. I will call Grand Rapids to discuss this application with them.

As for the holes on the leading edge of the Wing rib webs, It looks like the W711 ribs all come with 3 holes already drilled. One of them is for the supplied aluminum tubing pitot air line that comes stock with the Vans Wing kit. They do not supply a heated pitot tube solution, and lots of folks stick with the stock method for reasons of cost and simplicity. My plan for these holes is to use the bottom 2 holes for the pitot and potential AOA air line, so those will be drilled to 3/8 inches most likely to accept the correct size bushing for 1/4 inch air lines. The top hole will be drilled to the max 5/8 inch hole to accept the larget bushing (SB625-7) I can put in there for additional wire runs above and beyond whatever I can imagine will fit inside the 3/4 inch conduit holes I am drilling now. Probably a lot of overkill, but better to build the capability in now instead of fretting later over why you did not do it when you had the opportunity.

After doing some research, I found that I could shop for used heated pitot tubes online, and the cheapest one I could find would be about 200 to $250.00. The Dynon Pitot tube sells new for about $450.00. I am a little leary about purchasing a used Pitot tube and find out the heating element does not work, or the wiring is decayed beyond usefulness, or it is corroded to the point if restricting airflow through the tube, etc. New pitot tubes, on the other hand, run in the 1500.00 to 2000.00 range and up from there - absolutely rediculous, as are most prices involved with anything in aviation. So the Dynon Pitot tube by far seems to be the better value any way you slice it.

SO the question them becomes, what will I do with the additional AOA airline in the Dyon pitot tube? My original plan was to go ahead and run the additional line from the pitot back to the root of the wing and then plug it there. Then I read a post the other night that hinted that the est thing to do was to cap the line as close to the pitot tube as possible, or in other words, do not run any additional line from the pitot and cap it right at the end of the supplied tubing on the pitot tube. Perhaps there is some element of trapped air in that line that may affect the air pressure coming from the pitot line, and therefore introduces some sort of error into the pitot line, which would not be good.

Anyway, I will have to think about this a bit more and ask some questions before I decide what to do. Plenty of time to come to a solution for this. With a nice bonus from work, and hopefully a somewhat decent tax return coming soon, and a birthday on the horizon, I have plans for several wing-related purchases in the not-too-distant-future. Now, what to do about the landing, strobe, and position lights? Hmmm. :)

Marking and Drilling Holes for Conduit

Tonight I set out to mark and start drilling the location of the 3/4" holes required for running the conduit that will contain the majority of my wire runs for various electrical components in the Wings. These will include things like strobe and navigation lights, landing lights, pitot tube heat, autopilot servo wires, antenna wires, etc. For most applications you will be running 18-22 ga. wire, so it is relatively small, but items such as the autopilot servos require between 5 to 7 wires just for that, so you have to ahve enough space to run the wires for each component.

I chose to use the Vans Conduit, which is a black flexible light weight conduit that can be easily mounted through a series of aligned holes in the wing ribs. I am admittedly concerned about using it after reading several posts from folks that performed fire tests with this stuff, all of whom comment about the thick toxic black smoke that exudes from it, and how easily it catches fire and how quickly it burns. Not a very comforting thought for a pilot. But I have also reasoned that I do not hear of any accidents or problems that are attributed to wing fires and such, and with 8,000 airplanes flying I think I am OK using this stuff as long as am careful about all of my electrical wiring when the time comes.

This process begins with a service bulletin that can be found Vans website. It contains instructions for drilling additional holes for wire runs in each of the ribs, and provides some general information about where this can be done.

 The big hole on the bottom of the rib in the above pic is the one I am focusing on now. As is usually the case, Vans fails to provide any specific measurements about the location of the holes, just a general picture. So step 1 was to figure out exactly where I need to locate the center of each hole in the rib, then how to create a template that would ensure that each hole in the rib is streamlined from root to tip so that the conduit, adn therefore the wires inside, run in a straight line.

At first glance this seems like a fairly simple process. As you dive into it a bit more you discover there are some things you need to take into account to ensure that the holes are aligned correctly from rib to rib. First is the realization that the ribs are not all the same size. Several of the more inboard ribs are a little shorter in length that the outboard ribs. Why? because the inboard ribs are attached to the doubler plates of the main wing spar, which is about 1/8 inch thick. So these ribs are 1/8 inch shorter. Then you have to determine how they are shorter. At the forward end or the back end. Since the rear spar runs in a straight line all of the ribs ends are aligned, so the difference in length is at the forward part of the rib. Why am I going through all this thought process? Because if you don't get the holes aligned relatively well with each rib it will make running both the conduit and the wire runs a bit more difficult due to the increased friction caused by the uneven line that the wires will need to follow when being pulled through. So the straighter the better.

I took measurements from the front flange of the ribs to the line formed by the perpendicular crease that separates the first and second lightening holes of each rib. This line turns out to be the best reference point for determing where to place the holes. As long as the holes are the same distance relative to this line then they should be relatively aligned with each other.

So now it is time to determine where exactly to mark the center for these holes. My process was to take one of the ribs, eyeball the distances from the document as best as I could, and draw some initial lines to define the center point and the end points of each hole. Then stare at it for a bit to see if ot look right.

I thought that the location in the above pic looked pretty good, but then I had another revelation. I recalled some posts I had read from builders along time ago that mentioned some difficulties with the conduit when it came time to start riveting the skins on. Then I noticed the relative position of my center line and each end point of the hole relative to the two rivet holes on the bottom flange of the rib. The hole I drew was just slightly forward of the center line between the two rivet holes for the skins, so I decided to adjust the hole back about another 1/8 of an inch. For those that may be interested, the location of the rear-most edge of the hole is about 1/4 inch forward of the forward most line of the straight line depression, and the bottom reference is about 5/8 of an inch from the bottom flange of the rib. I found these to be the best reference points to use for creating a template for the remaining ribs that will allow the transfer of the location of this first hole to the other ribs.

With the center point of the hole determined, it was time to drill. I used a center punch and then drilled a small 1/8 inch (#30) pilot hole. No turning back now. Next came a 1/4 inch hole to widen it just enough to fit my unibit with a final 3/4 inch step - you know, that crazy tool that I last used on my rudder rib that I had to replace after screwing it up. Fortunately, I did remember the lesson I learned from that experience. Very simply it is to make sure that when I use that unibit, or step drill as it is also known, use it ONLY with a variable speed electric drill and NOT the air drill. That is how I got into trouble before - just pressing a trigger and letting it wallow out the hole however it damn well pleased.  Not letting that happen this time - so I used the electric drill. Worked out fine.

I clamped the rib using some thick pieces of wood, since the unibit I have is quite long, and would need to penetrate at least 1.5 inches of material before the final 3/4 step would drill through the rib. From this next pic you can see how the hole was repositioned about 1/8 inch back from the original marks. I wanted everything to be equidistant between the two bottom flange rivet holes so that the effort of getting a bucking bar positioned for each of the holes would be as easy as possible.

and the unibit I used with the electric drill:

And then finally with one hole drilled successfully, it was time to make the template for the other ribs. My method - I used half of a cardboard paper file, aligned it with the edge of the straight line stiffener impression aft of the first lightening hole, and placed the bottom corner of the file at the bottom of the rib web. I taped it into position, and then drew the hole on the opposite side, using the edges of the hole in the rib as my guide. I then took an Xacto knife and cut out the hole in the cardboard template. Now all I need to do is tape the template in roughly the same position and draw the hole onto the rib web. I used regular cellophane tape, which seems to work great for adhering, removing, adn adhering again to the next rib. All of the template fitting was performed under several general assumptions, including:

1. The perpendicular stiffener impression is in exactly the same location and orientation on all of the ribs(I forget the technical term for these, but they significantly stiffend the web of the rib - see Hints for Homebuilders videos on the EAA site for info)
2. This rib width is exactly the same for all ribs.
3. I was not looking for perfection here. I figured as long as the hols are within about 1/16th of an inch aligned with each other, then that should be more than fine.
4. I laid the template down across the flat side of rib, where the stiffener impressions are inward or concave to the surface, so that the template would lie flat on the surface. The opposite side of ribs contains the outward or convex part of the stiffeners, and these stick up aboce the surface of the rib web, making it harder to apply a flat piece of cardboard - so use the other side when marking your holes.

Since the ribs have flanges that face in alternating directions (L and R desingations on the rib part numbers), all I had to do is flip the cardboard template over and align it exactly the same way as I did for the other ribs.  Only problem with this is that you have to remove the tape and reapply it to the other side of the template, so it is best to do all the ribs facing one direction first, and then switch the tape one time and do the other ribs, to avoid ripping the cardboard too much. You can also use the same template for all the ribs or make separate ones for the left and right-flanged ribs- the choice is yours.

Now I just have to finish transferring this hole onto all the ribs for both wings, drill, debur, and then I drill a couple of other smaller ones along the front of each rib and one in the rear for the nav antenna wire. I only need to enlargen this rear hole for one wing, but I may go ahead and drill antenna wires access for both wings just in case I decide to run more than one antenna. Antenna wires need to be about 12-16 inches away from other power source wires to prevent interference from the electromagnetic fields that are generated by the power wires. Fun stuff.

So that ends our lesson on how to locate, mark, drill, and debur holes in the ribs for running conduit.