The first problem I had to solve was how to properly position the attachment bracket against the end rib so that it would allow the spar to sit as level as possible across the entire length of the wing spar.
I knew I needed to get the angle bracket flush op against the rib in just the right position, which is basically at a point where the bracket sits flush up against the web of the wing spar. The only problem with this is that this bracket is atached to the outside of the end rib, where no wing spar web exists. So how do you position this bracket in exactly the right position oif you cannot lay it down flush against the wing spar web?
After thinking about this, I had a moment of deja vu. I was sure I had been in this position before, just could not remember the specifics. Anyway, the solution was simple. The last three outboard ribs of each wing are W712s, the only difference is that the 2 inboard ribs are "L's" and the end rib is a 712 "R". This just dictates the direction of the flanges on each rib, but the ribs themselves are essentially the same part with the same dimensions. This means that I could take the W712R end rib and move it inward to the inboard location of the W712L rib, cleco it in place, and whaaalaaa, I now have a healthy amount of wing spar rib to butt one side of the attachment flange up against, while the other side is flush against the end rib.
The whole point of this exercise to position the bracket in the correct place on the rib so that I can match drill the 1/4 inch holes in the rib for the bolts that will attach the bracket to it. IN previous posts I had already drilled the mounting holes in the steel angle. All I am doing now is transferring those holes to the correct location on the rib.
A pic is worth a thousand words:
I clecoed the rib in every hole, then slid the attach bracket in place, clamped everything down, adn match drilled the mounting holes:
The wood in the above pic is used as a backer for the drill bit to help prevent the aluminum of the rib from getting too rough when the bit penetrates the other side. This is thin drilling aluminum 101.
Next is a pic of the whole thing clamped into position and ready for drilling. I clamped down the spar onto the table in addition to clamping the parts together. I have had enough of wallowed out, uneven holes die to improper securing of the work. Remember to clamp EVERYTHING securely before you drill or rivet. Any movement of the parts during either of these activities usually gives less than desireable results.
Remember to keep the clamps from rubbing or vibrating against any of the parts. Pad them if necessary or use a large enough clamp to ensure that it does not interfere with the parts.
Let the drilling commence:
The tooling hole is somewhat close to the bolt hole that I drilled on one side, but this is perfectly fine. Vans also states in their plans that drilling these mounting holes will not compromise strength of the rib, which also tells you something about how not to worry too much about drilling additional holes for wire runs as necessary. I removed the rib and the bracket, then deburred the new mounting holes in the rib, and reattached it to the correct location at the end of the spar. Then I bolted the atach bracket in place on the end rib. One down and one more to go for the right wing spar!
Then it was time to trial fit everything on the stands and do a general check for level.
This first pic shows the overall mount with both sides clamped to the stands:
Next is a series of pics showing the mounting bolt orientation of the mounting bracket and the clamping arrangement to the wing stand. I will most likely drill additional bolt holes in the wing stand and attachment brackets once I am satisfied that they are in the final position I need for assembling the wing skins.
A couple of important notes about this.First, remember that certain disimilar metals that come into contact with each other can cause corrosion and other problems. Not remembering if Steel and aluminum "play nice" with each other or not, I decided to err on the side of caution. I placed a piece of gorilla tape over the side of the attach bracket that contacts the rib, and I will do the same thing on the inside of the rib shown above where the mounting nuts and washers are located. The ribs will be completely primed, but I still want to do whatever is necessary to avoid any other means of introducing corrosion.
Next, I used standard 1/4 inch HD hardware for this assembly. The only problem with this is that the cut washers are exactly that - stamped from a press, which leaves a rather nastly burred edge on one side of the washers. I deburred them as best I could, but in the end realized that the easiest solution for this was to ensure that the side of the washer that is smooth (one side is very smooth, and the other is rough) is what is placed against the wing parts. The other rough side will rest against the bolt hardware.
Next is a pic that shows the clearance gap between the angle on the stand and the mounting bracket on the rib- which is the main reason that used the 2 inch wide angle. This clearance is needed for the wing skins that extend beyond the edges of the end rib to provide the mounting surface for the Wing Tip, I have pently of clearance here, and may end up moving the brackets a little closer together once I see how much clearance I actually need when the outer wing skins are on.
And then a couple of pics of the Root side of the wing spar. I used 6" C clamps for this and a block of 1x2 wood to keep from marring the thick steel spar bars.
The above series of pics serve as confirmation that I definitely have sufficient space between the wing stands to position the wing spar on them. I can move it up an inch either way and still have sufficient room to rest the spar on the stands. This is what I expected and was worried about based on the uneven garage floor and all the shimming I had to do.
And finally it was time to strap some levels across the spar and see where things are at. I can't really make any rush judgements about anything until all the ribs and the rear spar are clecoed to the main spar, and the sag is taken out of the middle by using a jack stand or similar solution. For now, I was pretty satisfied with the results - everything was "mostly" level.
I seem to have a slight twist in the spar as I get closer to the root end, and I also found out that the spar bars are NOT milled to exactly the same specifications from bottom to top. They are both uniquely milled to different specs to provide different specific levels of strength and support, and therefore you cannot just lay a level across the bars and expect to get a level indication. That said, the mounting flange of the wing spar where they will be inserted into the fuselage center section and bolted in place is perfectly level.
So it was good to get one of them ready for additional assembly. Now I need to wash, rinse, and repeat this process for the right wing spar, which I hope to have done by the end of this weekend. But alas, another round of snow is expected tonight....
No comments:
Post a Comment