Panel Installation Issue, Need Advice

I have come across an issue when fitting the F-803 instrument panel sub-assembly into the fuselage. I have a gap between the 803 and the F-821 top skin where the panel intersects the F-887 longerons. Also, below the longeron on the left side, the panel interferes with the side fuselage skin. I am trying to figure out what is causing this problem. Are the sides of the fuselage spread too far apart? If I try to pull the fuselage together, the interference on the left causes the panel to bow. Should I shim these gaps or should i try to trim the panel and pull the fuselage together? Is there a problem/solution that I am not thinking of? Has anyone else had this issue? If I try to rivet as is, the 821 skin will dent a good amount in these areas. Pictures of my problem are attached. Thanks for the advice, I'm stuck.

I dont have manual with me to let you know parts number or exact name but you should install windshield steel frame and seat back steel suport (steel parts painted white than come ready with the kit) before to atemp to install intrument pannel or front deck. that parts will square your fuselage. I hope you understand what I am trying to explain

Panel

I built my RV-8 10 years ago. Had the same issue. The easiest solution is to shim and move on. Cover it with upholstery. The elegant solution is to cut new panel pieces to fit out of new stock. I believe it?s .063 (maybe .090, don?t remember for sure) material with a 90-degree flange at the bottom. I?m pretty sure Van?s sell the bent but uncut stock.

Shims

flyenforfun said:

I have come across an issue when fitting the F-803 instrument panel sub-assembly into the fuselage. I have a gap between the 803 and the F-821 top skin where the panel intersects the F-887 longerons. Also, below the longeron on the left side, the panel interferes with the side fuselage skin. I am trying to figure out what is causing this problem. Are the sides of the fuselage spread too far apart? If I try to pull the fuselage together, the interference on the left causes the panel to bow. Should I shim these gaps or should i try to trim the panel and pull the fuselage together? Is there a problem/solution that I am not thinking of? Has anyone else had this issue? If I try to rivet as is, the 821 skin will dent a good amount in these areas. Pictures of my problem are attached. Thanks for the advice, I'm stuck.

Click to expand...

Very common on the -8. Use shim stock as necessary to fill the void. IIRC, I used cut up .125in angle at the widest part. From there use combinations of .062in, .032in, and .025in. as required to fit.

Make sure the roll bar is bent to the correct dimension, then use the shims.

Just remember to countersink/dimple as required.

Matt,

For the instrument panel to fit exactly, a lot of things have to work perfectly and chief among those are the longerons require precise bends at precise points for the final location of the longerons to fall absolutely within spec. Since we form the overall shape of the longerons more or less in a free-handed manner, that is, without bending those structural parts into shape with dedicated tooling specifically designed to insure consistency from one airplane to the next, rarely is such perfection achieved for the average homebuilder.

I agree with Fernando that first, you should install the windshield frame to help make certain the longerons are correctly located. This detail photo may suggest why:


Next, I would trim to remove any riding condition in the area circled in yellow. Doing so may relieve some outward pressure on the side skin and help to relieve some of the gap above the left longeron, but I wouldn't count on it reducing it by much.


Finally, to eliminate any chance of denting the exterior skin when everything is finally riveted together the gaps simply have to be shimmed. There is no way around it. Gaps larger than .125 should be filled with solid shims. This can be tedius work but from what I see in your pictures may only be applicable to a relatively small area. All smaller gaps can be quickly and easily eliminated using "liquid shim," a technique I have used many times in many applications with great success:

http://www.vansairforce.com/community/showthread.php?t=6750&highlight=liquid+shim

I took a strip of aluminum about 1/2" X 4" and filed a taper until it just fit in the gap. Drilled & counter sunk. Painted black. It's virtually invisible. Gap's still there but it's in an area only you will notice.

Interference

I saw your post and as I was going to cleco my panel in place in preparation for checking position on my instrument panel, I gave that area special attention. Thanks for bringing the issue up.

It looks like I have interference issues in the same area. That would be easily solved by trimming the offending points on the 803.

It doesn't look as though I have quite as large a gap with the top skin, but it IS there.

Has anyone tried letting the rivet flange "float" out to mate with the upper skin, and then drilling new holes in the flange to match the holes on the 803? Do you think that would work?

I haven't yet looked to see if the aft face of the flange is wide enough. Probably will be in mine but I'm not sure about yours. If not, perhaps you could "de-rivet" that section and replace it. Another idea might be to "de-rivet" the flange from the 803, cut an "extension" out of .063 to match the curve of the flange against the skin, and use keeper rivets to attach it to the flange. There might be a gap there (but not a hole), and at least the upper skin would be tight against the flange and everything secured nicely.

Thoughts, anyone?

Follow Up

I worked on this issue today. First let me say that the panel support flange was clecoed on, not riveted, so it was easy to modify things.

I first trimmed the 803 subpanels where they were tight against the side skins. I probably belt sanded no more than an eighth inch on each side.

Next, I enlarged the notches where the 803 fits around the longeron. I filed the bottom side of the horizontal notch (fits around the horiz portion of the longeron), then filed the vertical notch (fits around the vertical half of the longeron).

This allowed me to move the panel up to meet the skin rather than pull the skin down to meet the panel. It took out more than 90 percent of that gap.

Don