Forward top skin matching problem

[dmatre]

Performing an initial fitment check of the RV8 forward top skin.
The dimpled rivet holes align with the fuselage at the firewall and intermediate arched bulkheads but are 1/4" to 3/8" short at the instrument panel as well as the left and right welded steel canopy area brackets.
It seems I need to lower the entire panel assembly - thinking about keeping it 'floating' vertically while riveting the top skin.
Has anyone else had this issue?

 

[Carl Froehlich]

It looks like you had someone make the panel, correct? Did the top skin fit before you added the panel?

I suggest:
- Take the panel out and rivet the skin. If something needs to be adjusted the panel can be trimmed much easier than the top skin.
- While you are at it, you will need to provide a brace for the missing baggage door skin. I suggest fitting the cutout skin as best you can, then add two 3/4”x3/4” pieces of angle to bridge across the door opening to secure the firewall. This needs to be done before fitting the cowl as you want to make sure the firewall is not flexing when trimming the cowl.

Carl

 

[RV7 To Go]

Have you tried putting more clecoes in starting at the top and working down, then going from the firewall end and working back? Many times I have had to use an awl to pull the skin into position as I go. My forward top skin was tight but I was able to get things lined up for riveting.

 

[PhatRV]

Have you tried putting more clecoes in starting at the top and working down, then going from the firewall end and working back? Many times I have had to use an awl to pull the skin into position as I go. My forward top skin was tight but I was able to get things lined up for riveting.

Try this first. I filled the holes with clecos to make sure they will conform to the curvature. Also, did it fit before you mount the new panel?

 

[nzrv8]

I have just finished this task, and that skin is the worst of the build! Cleco every hole around the tight part of the curve, and you'll still need an awl to gently lever the skin down for the longeron holes. It'll fit.

 

[skelrad]

While it won't make up for huge mismatches, don't discount what heat can do as well, especially over large areas. I had a terrible time getting the front top skin on my 9A to fit without using straps and heat. If I were to do it again, I'd start by using a slip roller to put a curve in the skin to match the final shape. I bet that would have made a huge difference in how it matched up.

 

[dmatre]

Thanks for the inputs. I loosened up the panel assembly from the fuselage (two bolts in longeron) to be floating and was able to insert all clecos - also needed to match drill a bit on a couple holes. However, after that there are two gaps left and right between the wing panels and skin. I am the second builder and inherited the panel shapes. Maybe he made the arching member wrong and not the proper curvature. Thinking about locally remaking the riveting tabs in these gap areas to reach the skin. Really do not want to redo the facia panel.

 

[Ralph Inkster]

Try inserting a shim strip between the skin & panel mounting bulkhead. Cut them 3/4" wide & 12" long, .025" thick, match drill them to the top of the panel bulkhead & dimple. Trial fit a few times, trim the length as needed, stack them up if needed, paint black before riveting. Note that you will have to determine proper rivet length in the various holes along the shimmed areas.

Also, in the first post I notice the rivet lines were not dimpled as crisp as they could be (note the reflective distortions around each dimple. Look at the rivet lines on the fuselage side panel to see how distortion free they are). If the dimples were better finished they would lay deeper in the rib/bulkhead dimples and overall you would align the holes better with less tension along the edges of the top skin.

I would re-dimple the skin panel first before fitting the shim strips on the panel bulkhead.