......But to look at the pics you wouldn't think that I got too much done. I have a lot to post tonight with a large number of builder tips. Hopefully builder that read this will find them useful.
It started with a review of Vans instructions regarding the leading. I reinstalled the Left wing LE ribs to the skin in the cradle, and then I realized that I was going to need to remove more vinyl from along the edges of the skin that overlap and attach to the main wing spar. Some older videos/DVDs cover a process to attach the LE to the wing by using cargo straps to wench down the skin onto the main wing spar, saying that this is needed due to the extreme tight fit of the LE to the wing. Well, the cargo strap technique is not used quite so much any longer since all the building of the LE and the fuel tanks is done in the cradle, but the extreme tight fit to the wing spar is definitely still there.
I moved the LE to the correct position on the wing,which I had done before, and clecoed all the rib-to-spar flanges to the wing spar from underneath, except for 2 that I will explain later. Up till now I had only clecoed the end rib to the wing spar just to get an idea of the fit. I had not clecoed the skins to the wing spar, and that is where things get very, very tight. Then I clecoed the skins to the wing spar, starting with the bottom skin holes. In retrospect I probably should have started with the top skins first, but I don't think it would have made any difference. Once the first few clecoes were in place it got easier, but was still very tight. Then, when I tried to cleco the other side, this was almost impossible. I almost thought about getting the straps out to cinch then down far enough for the clecoes to fit, but eventually I was able to get them started without needing the straps. This was still very difficult to do, and after having done it I can now appreciate when they tell you that the LE is put on very very tight.
Vans instructions say that the flange of the 2 LE ribs just outboard of the tie down bracket does not match the holes in the wing spar, so this is yet another case of using the holes in the wing spar to drill the new holes in the rib flange and abandon the others. A note to other builders - 3 of these holes still DO match the same holes in the wing spar. They are the ones in the center. Only the two holes on the ends do not have pre-drilled holes in the rib flange. So you can cleco the holes in the middle to keep the flange secure while you drill out the other holes on the ends.
So how do you drill them out. Well this is where it gets interesting. You have to drill them out from the botttom of the wing spar.Also, to avoid the contact of the drill chuck with the main wing ribs, you have to use a drill bit extension. This actually turned out to be fairly easy, but you do have to pay attention. I used one hand to guide the drill bit and the other to run the drill while bending it just the right amount to keep the drill away from the rib flange. Here are some shots of the clecoes:
And here is the problem rib. Can you see the problem?
For all you future builders - make a note - when you figure out where to drill your holes for the angle used to mount the wing to the stand, make sure you position the bolt holes so they are not directly underneath a rivet hole. I was only able to drill out the three holes with the clecoes for now, and I will have to remove the bolts one at a time while ensuring that the wing remains properly on the stand. Since the wing is also secured on the bottom support angle of the wing stand this should not be a big deal - we'll see.
Here is the 12 inch #30 drill bit extension I used to match drill the holes.
Here are the clecoes for the LE skin on the bottom side. Vans says to cleco every third hole.I can never figure out if this means third hole AFTER the one that is clecoed, or third hole including the one that is clecoed, which basically means every other hole. Either way, it works.
Here they are on the top side of the wing, where they butt up right next to the top wing skins, exactly like they are supposed to. This never ceases to amaze me - that the match drilling and cnc holes are so precise that everything just lines up the way it is supposed to. I really liked seeing this. The skin with the vinyl removed is the lower wing skin, and the topis the LE skin:
And now for the less than fun part of the day - fitting the inboard 408-1-L rib and the joiner plate together. This rib has absolutely no holes in it whatsoever, the position/clamping/securing of this part is critical to ensuring that the holes get drilled in the correct location on the flanges. This becomes difficult when you try to position the joiner strip between the rib and the skin. You end up losing reference of the location of the rib and the edge of the skin because the joiner plate gets in the way and extends well beyond the edge of the inboard LE skin. You are trying to make a sub-skin that the fuel tank skins will slide over when the fuel tank is fitted to the wing right next to the LE. The two skins should butt right up next to each other. This joiner plate also gets nut plates attached to it later on.
All I can tell you is that this was a pain in the ass. The joiner plates is made from 1.5inch x 36.5inch long .032 inch thick aluminum sheet. I deburred the edges, and then marked a line 1/2 inch from one edge, per the instructions. This line is a guide line for the holes in the LE skin so you can line up both the joiner and the rib correctly.
Here is the strip with the reference line drawn;
The hard part of all this was getting the strip to fit in between the rib and the LE skin. I ended up doing something different than the plans by using the rib on the work bench as a form and then taking the strip and forming it around the rib to establish the necessary curve around the nose of the rib. The ends of the strip should end up matching the end of each side of the rib flange after it is all in place, but you are not sure where they will end up when you start fabricating everything. Once the strip is pre-bent to the shape of the rib, I placed the strip inside the wing skin, and then I took the rib and started inserting it from the nose first, followed by the base, which is different than how Vans tells you to insert the rib. This most likely resulted in the bending of my rear rib flange just a bit, but was not too bad, so I left it that way when I drilled it. I will bend it back into shape after I remove it for deburring later on.
The plans tell you to line up the plate by moving it until the line shows up under the rivet holes in the wing skin. Then you verify the position of the rib by ensuring that the distance between the rib web and the end of the joiner strip is 11/16 of an inch. I must have measured, clamped, remeasured, repositioned, and re-did everything all over again about 20 or 30 times. I used my ruler to verify the 11/16 inch measurement, and when I thought I had it all lined up and put a couple of clamps on as shown below to keep it from moving:
I found this to be very perplexing because you cannot clamp the rib flange to the main wing spar at all,and I wanted to make sure that the flange would not move when I started drilling it. So clamping the skins was the only way I could try to secure the assembly and keep it from moving. Then, when I was satisfied that i had everything as lined up as it was going to be I started by drilling the holes for the spar flange:
That seemed to go OK so I then started drilling all of the skin/joiner plate/rib holes from the top side and then around to the bottom side. I was very worried that the holes may not be lined up on the rib flanges correctly, and I do think that they are a bit on the inside and too close to the rib web, but I will know more when I remove the rib after all the drilling is done.
And finally, here are some shots of both sides after all the drilling was done:
And one last shot of the wing with a mostly drilled out LE:
Tomorrow I finish drilling all the remaining holes, and then I start working on the right wing leading edge adn do everything all over again, hopefully better than I did this time.
No comments:
Post a Comment