Help with F-820/F-823 Fuselage Skin Lap Joint

I'm having trouble with the lap joints between the F-820 and F-823 fuselage skins on both sides of my RV-8. When I first tried to cleco the forward skin in place, I started at the firewall, clecoed the landing gear boxes (the holes there lined up well), but when I got the the lap joint, the holes were significantly off. The delta is about 3/32" on the right side, and 1/16" on the left. (Pics 1 & 2)

I removed the clecos and started again, this time from the bottom edge of the firewall and lap joint and clecoed up both ends. I then clecoed the landing gear boxes to the skin, which wasn't too difficult, but some of the holes took a bit of pressure to get them into position (mostly around the gear weldments). When I stood back and looked at it, I found waves across the top of the skins when viewed from the front. (Pic 3) When I looked at the side (Pic 4) I thought these waves might be caused by the bulkheads trying to curve the top of the skin, so I removed the top 8" or so of bulkhead clecos and the result looked better (Pic 5), but not perfect. When I took the skins off, there's still a lot of sheer pressure in the lap joint, and it sprung back to the position in Pics 1 & 2 when I removed the last clecos. It seems like it generates more sheer force than should be necessary or acceptable, but when I cleco the ends first and the gear towers last, it takes less effort to install the clecos than the fuel tank skin/ribs did.











As far as I can tell, everything is in alignment with the gear towers, lower longerons and cabin floor. I haven't riveted the bottom skin under the back seat yet so that might be a factor (I was waiting to prime it), but I will get that done this weekend.

Any ideas on how to proceed?

Thanks,
Rob

Hi Rob ... I've been watching your thread to see if the brain trust had any advice; I'm starting my fuse now and am very curious about the cause of your issue. Any updates?

Better late than never

I didn't see this when originally posted.

As for the holes not aligning, just keep at it and use lots of clecos. If you prep is good it will all come together. Mine was also very tight in spots.

I also had the waviness in the top of the fuse skins prior to the installation of the longerons. Without the longerons installed there isn't any lateral support at the top of the skin. When the longerons are installed use lots of clamps prior to any drilling. This will assure the skins are pulled down tight and all the pre-drilled holes are are correctly distributed along the longeron.

Hope this helps.

Blue Vinyl

I would recommend stripping the blue vinyl off of areas where parts join together before you match drill. It will change the thickness of the parts slightly and could affect overall alignment in certain areas. This may or may not help your specific problem, though.

Skylor

Problem area

Get rid of the blue plastic , as mentioned before . All these parts line up just about perfect , sometimes you have to figure out the right sequence, but they will line up . An ice pick it a great alinement tool .

Just in case this is still a problem.....

I had the same problem with the lap joint. Mine matched at the very bottom and was out at the top. Wrestled with it a for a while, searched the forum with no success, finally called Van's. Like G-Zero says, use an ice pick to help align as you move up clecoing every hole like a zipper. Vans said there is a lot of force coming together at that point, common issue...

http://www.mykitlog.com/users/displ...n&project=831&category=8759&log=183993&row=19

sapeloson said:

I had the same problem with the lap joint. Mine matched at the very bottom and was out at the top. Wrestled with it a for a while, searched the forum with no success, finally called Van's. Like G-Zero says, use an ice pick to help align as you move up clecoing every hole like a zipper. Vans said there is a lot of force coming together at that point, common issue...

http://www.mykitlog.com/users/displ...n&project=831&category=8759&log=183993&row=19

Click to expand...

Thanks, this is really helpful. I have learned that when I have to force parts together it normally means I've done something wrong. I figured the waviness on the top would clear up once I added the longeron, but it's great to have other opinions.