A

apatti

Well Known Member
All,
I have a tank / leading edge fit problem. The tank skin sticks out a little farther than the leading edge skin. By little I mean about the thickness of the tank skin (a little more in some parts and a little less in others). This occurs aound the front (leading edge) where the two skins meet. When I remove the joint plate and mount the leading edge and tank to the spar they look OK. Thus, my diagnosis is the joint plate was not drilled properly. So, easy enough, just make a new joint plate, right?

Well, not so easy... both the tank skin and the leading edge skin have already been dimpled. I did manage to drill the holes in a new joint plate for the leading edge attach. However when I try to fit the tank to the leading edge so I can drill the nut plate holes the dimpled #8 holes in the tank skin prevent me from getting a tight fit. Any thoughts on how I might locate the nut plate holes on the joint plate and get a good fit?

Thanks,
 
Well, there are a couple of things you can do here.

1) Make sure that you're problem is not a sagging spar. I'm assuming that in this stage your wing is in your jig/stand or whatever. Make sure that the rear spar is supported and try pushing up on the wing.

2) You may have gotten too much pro-seal under the outboard-most z-bracket/rib. That will push up the tank a litte. Some folks have filed down that outter bracket to get the tank to sit a little farther aft on the spar.

3) A local builder here had problems getting everything lined up with that splice place so he opted to put floating anchor nuts on the strip instead. It worked well for him.

4) I had a very similar problem getting the fit just right. I had not put the bolts in from the back-side of the spar to the z-brackets and this was causing my problem. Once I put the bolts in it pulled the tank down nice and tight.
 
If the problem is you have a widening gap between the tank and the leading edge that expands as you work closer to the spar, the problem is most certainly that the rear spar is sagging. I encountered this problem a few years ago and Van's was puzzled until I told them that all I had to do was give the bottle hydraulic a couple of cranks and "pop," it all fell into place.
 
Oh, one other thing to check. There is VERY -- and I mean VERY -- little clearance between some of the rivetson the baffle and the inboard area of the main spar. If you've put a lotof ProSeal on the heads of those rivets, it will rub up against the doubler bars and prevent a good fit. If you liftyour tank off the spar, check for ProSeal remnant in this area and you'll see the spots on the baffle where you may need to remove ProSeal.
 
joint plate

apatti said:
All,
I have a tank / leading edge fit problem. The tank skin sticks out a little farther than the leading edge skin. By little I mean about the thickness of the tank skin (a little more in some parts and a little less in others). This occurs aound the front (leading edge) where the two skins meet. When I remove the joint plate and mount the leading edge and tank to the spar they look OK. Thus, my diagnosis is the joint plate was not drilled properly. So, easy enough, just make a new joint plate, right?

Well, not so easy... both the tank skin and the leading edge skin have already been dimpled. I did manage to drill the holes in a new joint plate for the leading edge attach. However when I try to fit the tank to the leading edge so I can drill the nut plate holes the dimpled #8 holes in the tank skin prevent me from getting a tight fit. Any thoughts on how I might locate the nut plate holes on the joint plate and get a good fit?

Thanks,
Click to expand...
You might want to look again at your original splice plate. If you had things in alignment when you originally drilled the holes, I'd play with the original splice plate before hassling with a new one.
Does the alignment occur without the fasteners in place? The platenuts cause local flattening which could cause the slight fitup issue you see at the LE (the flats cause slight bulging at each end). Put a block of wood on the tank LE and tap it a few times with your dead-blow hammer. If that brings things in line, look at the holes in the splice plate see how they align. That will tell you if you need a new splice plate or not.

If you decide you do need a new one, I'd slide the tank inboard enough so that the splice plate clears the dimples and mark the fore/aft position (line up a ruler through the center of the hole in the tank). Then slide the tank into position to mark the centerline (do multiple locations and draw a c/l for all the holes). In other words, you'll have to carefully mark the location and drill rather than drilling through the tank.

Dennis Glaeser
7A Fuselage
 
Jamie said:
Well, there are a couple of things you can do here.

1) Make sure that you're problem is not a sagging spar. I'm assuming that in this stage your wing is in your jig/stand or whatever. Make sure that the rear spar is supported and try pushing up on the wing.

2) You may have gotten too much pro-seal under the outboard-most z-bracket/rib. That will push up the tank a litte. Some folks have filed down that outter bracket to get the tank to sit a little farther aft on the spar.

3) A local builder here had problems getting everything lined up with that splice place so he opted to put floating anchor nuts on the strip instead. It worked well for him.

4) I had a very similar problem getting the fit just right. I had not put the bolts in from the back-side of the spar to the z-brackets and this was causing my problem. Once I put the bolts in it pulled the tank down nice and tight.
Click to expand...


Jamie, Bob, & Dennis,

Thanks for the suggestions...

1) Sagging spar is not a problem. In fact, I adjusted screw jack until I had a good fit "side-to-side" fit between the LE and tank and then verified it with a "cross-hair" lasers.

2) Also, I should have mentioned that I have not Prosealed the baffle on yet. Also, since the skins match up perfectly when I removed the joint plate, that makes me think the Z brackets are OK.

3) I may have to look into those floating anchor nuts. Thanks.

4) This is interesting. At this point I don't have any bolts in the Z brackets. I was expecting the joint plate to pull the two skins into alignment. This brings up a question... When mounting the tanks do you tighten down the Z brackets first and then install the screws to the joint plate or the other way around? If the former, maybe I don't know if I have a problem at all.

However, the problem did exist with the wings in the jig and all clecoed together back before the 'big move'. I sent a picture to Van's back then and they said their usual "build on". No, I am not building a grand champion. Too many first timer mistakes already :) . But this is in such an obvious place...

Bob's comment reminds me that I need to check the proseal on the end tank rib to see if it is interfering with the joint plate. I used a lot of proseal so it is not out of the question. It's like when I was learning to solder and my lab instructor asked me if my uncle owned a solder company. :D

Thanks again. If anyone else has ideas please send them on. I will post what I eventually end up finding.
 
apatti said:
4) This is interesting. At this point I don't have any bolts in the Z brackets. I was expecting the joint plate to pull the two skins into alignment. This brings up a question... When mounting the tanks do you tighten down the Z brackets first and then install the screws to the joint plate or the other way around? If the former, maybe I don't know if I have a problem at all.
Click to expand...
There is room for a bit of movement in the screw to dimpled nutplate connection, so this will accommodate a tiny bit of misalignment. There is much less room for movement at the Z bracket to spar joint, so tighten that one first. I would tighten the Z bracket bolts first, then tighten the screws to the joint plate.
 
Ditto Kevin's comments above. The first time I put the tank on the spar after sealing it up (and already having the LE riveted on) I found that the leading edge of the tank didn't match up real well with the LE even though it had originally when I match drilled. However, with a little light persuasion from some tie down straps around the tank and the spar, I was able to get everything to light up just fine and all the screws fit into the nutplates perfectly still. If I understand your post correctly, I wouldn't worry about this until you get everything riveted together. A "lot" changes in the riveting process. Good luck.
 
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