Trouble fitting F-1041 and F-1069 side skins

I was making great progress on my SB fuselage.... longerons curved to within 1/16" of an inch compared to the template, side skins rolled to ~60 degrees.

Everything seemed great until I clecoed it all together, and I am having some alignment issues on both sides of the fuselage.

I twisted the F-1041 channels until they were parallel with F-1042 on the aft end and the WD-1003 weldment at the front. Before I clecoed on the skins, I used a sharpie to draw a line where the F-1042 wraps around the WD-1003.

After a bit of wrestling, I got the forward side-skin all clecoed on. The curve (as seen below) matches the firewall, and the underside edge of the skin buts nicely to the floor skin.



However, when I started to look at the F-1041, it appears that clecoing it to the skin caused it to shift outward from the WD-1003 weldment. Additionally, you can see where the floor pan is to be riveted to the F-1041, there would be huge edge distance issues if I tried to drill it as is.



So here I am looking for suggestions as to how to get this all to align better.

Thanks,
Jason

Happy New Year Jason

I struggled\hesitated\worried about drilling the holes in those weldments as I could not get everything to center up. I spoke to Vans and basically came away with the understanding I may not be able to achieve the optimal centering\edge distance of 2 x dia and that would be OK

I ended up clamping the weldment with c-clamps\wood and drilling ended up closer to 1 dia edge distance.

It is just not possible to move that weldment around close to the center hub. Out at the end of the three tabs, you can push is around\align it a bit but close to the root edge it is not going to move. Here is pic of my toughest area

Steve

Found a solution.

I have just gone through this part and believe that I found some details to help.

I was looking at how to get the top and bottom flanges of the WD-1002 upper firewall brackets to line up closer to the upper channels (F-1040). I noticed that as I tightened bolts in the engine mount holes, the flanges came dramatically closer to lining up properly. I even used a heavy steel piece behind the bolt to put pressure as far outboard on the upper firewall brackets as possible.

As for the floor skin not lining up with the bottom channels, I found that I had to bend the skins a lot more than 60 deg to keep the outboard stress off the channels. I kept bending the skins so that they fit with almost no pressure on the side channels. It is the outward pressure from the skins that pulls the bottom channels outboard.

I have some pictures in my log (link below) to help illustrate what I'm saying

I hope this makes sense.

BTW Happy New Year!

Nick

I had to go back into my logbook for this, it's been so long ago. When I did the side skins, I had a friend used a block of wood to push the weldment to the longeron/skin. Then he pushed from the outside while I did the top/bottom flanges of the channel to the weldment. As Steve mentioned, the edge distance was not perfect there, but not bad. I worried about the force it took but that longeron is in the middle of the bend and the skin wants to flex outward. Possibly pre-curving it might reduce the stress, but once it was all together it was rock-solid. Later, when I went to rivet the forward floors I found that it had flexed so that the aftmost rivet hole was about one diameter out. I was able to get an electrician's pick in that hole so that I could get a #30 punch in the next forward hole, which brought everything back into alignment. Still a lot of stress from that skin in that curve.

So, you may be aware that my project was on a lift that failed and dropped it hard enough to wrinkle the skins at the main spar. The engine was mounted and the equipped panel (pretty heavy) was in place but there was no movement or damage at the firewall or especially at that weldment area. So much for instantaneous loads. I've not heard of problems with flying aircraft, so I don't think the stress shows up over time, either. So, this is one of those rare instances where my advice would be to just horse it into position with brute force and move on.

Thanks for all the suggestions. I spent alot of time today futher bending the side skins, and making sure everything was exactly per plans.


After alot of wrestling, everything now lines up much better. It looks like the edge distance for the WD-1002 weldments and the floor skins will now be fine.



However, just when I thought I had this portion licked, I noticed a skin crack at the tightest portion of the bend on the left F-1069 side skin. I've stop drilled the crack, and am hoping that will be sufficient, but would love to hear from any thoughts from any VAF tech counselors.




Thanks,
Jason

Just to close the loop, I spoke with Vans this morning and they thought I would be ok with stop drilling the hole, but a new skin was only $50 so I decided to just replace it. Now I have plenty of 0.032 scrap!