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Cowl attach/upper fwd fuselage

dhmoose

Well Known Member
Following the advice of others, I have delayed the installation (final riveting) of my upper fwd fuselage so i can make the installation of my avionics easier (benchtop versus upside down in aircraft). I'm now at the point of installing the Skybolt flanges on the upper firewall area so that I can begin installing the top cowl (engine and prop are on). Problem is, can I do this without having my upper forward fuselage riveted on yet?

I'm contemplating two options:
1) Trust the clecos are holding the Skybolt flanges/upper fuselage/firewall together well and start trimming the cowl
2) Rivet the Skybolt flanges/upper fuselage/firewall portion and then drill the rivets out later when I want to pull the upper fwd fuselage off for avionics installation.

Obviously, I don't want to induce any errors or distortions into the cowl trimming process. Has anyone been here and done that?

Thanks
David
 
other ways

You did not ask this, but I for one installed the upper fuselage fairly early. If you are installing a panel with large EFIS displays the panel will have large holes in it for those displays. (In my case, two GRT Horizons). I found I could work thru the holes in most cases, without having to lay on my back. The Horizons install from the front, making it easy to put them in at the very end (yes, a bit of on-your-back to tie wrap their cables once installed).
 
First, I would not use the skybolt camlocs. They won't work with the new Vans cowling without modification to the cowling. I tried and returned them. Search for my long thread on this subject. I wish I could have used them, but didn't want to mod my cowl.
Second, I would not trim the cowling without permanently attaching the upper forward fuse. In fact, I would not attach the engine mount without attaching the upper fuse. It is difficult to squeeze some of the perimeter rivets around the engine mounts. I was also concerned with the structural integrity of hanging the engine without the entire upper fuse and cabin cover installed.
When you trim the rear of the cowling you are setting the gap between the front of the cowl and rear of the spinner to 1/4", not much room for error, and not a lot of room if things change after you rivet it on.
What I would suggest is that you order the trays and harnesses, and whatever else you need for your panel to cut the panel and get the wiring completed. While you can reach through the front panel through the efis holes, it is still easier on the workbench.
 
I agree with Bill re Camlocks, assuming you have the pink cowl. If you have the old green cowl, Camlocks will work great. Did mine that way, and love 'em.

I trimmed my cowl without the upper forward fuse riveted and it worked out well. Also hung the engine mount and engine, so I could get the cowl-to- spinner spaced correctly. If you do it that way, there will be 2 rivets outside each upper engine mount bolt that will be a challenge to buck, but it can be done.

Jim Berry
RV-10
 
Gray cowl

I appreciate the input from everyone!

The engine has been mounted for some time now and everything is ok (no bent longerons, alum sheet, etc). I never did understand how the upper fwd fuse added strength seeing as is simply mounts to the top of the upper longerons. If the fuse is a rectangular box, the upper fwd fuse seems to be a "protrusion" from the box that doesn't seem to add strength. Either way, that ship has sailed :)

As for the skybolts, I have a gray cowl and understand the interference issue with the honeycomb. When eyeballing it today in the shop, it seems like I'd need to remove the aft 1/4-1/2" of the honeycomb...... either in small segments to clear the Skybolt flanges or in one long segment. Either way, does that cause any issues? I know some have suggested carbon fiber tape reinforcement. Btw, the skybolts appear to be spaced 3.5" apart which should prevent the cowl from expanding in flight.

So have folks done this? Pics? Thoughts on shimming distance? Am I complicating an otherwise straightforward thing?
 
David,

This is actually not that difficult of a modification. On my RV-8 I used a different spinner backplate assembly that pushed my entire cowl back and then proceeded to compound the problem by using a cold air induction system that pushed the fuel servo forward. I simply used my 90 degree die grinder with a sanding disk to very carefully remove the honeycomb material inside the cowl to a predetermined distance. I used regular 9 oz cloth the recover the trimmed away area. Other than a bit of extra work it was really a very easy modification. You do need to be careful not to add too much thickness the cowl where the Skybolt receptacle fits. Otherwise, you'll be doing a lot of trimming/sanding in order to get the lock ring to engage. I'm not certain, but Skybolt may sell deeper receptacles. I had already purchased mine at the time I made the modification. I think the idea of using carbon cloth would help avoid this problem.

I just started building a -10 and although this work is a long way in the future, I have every intention of using the Skybolt fasteners on the top cowl again. I went the hinge method on my RV-6 years ago and it certainly works. But after using the Skybolt fasteners on my -8, I won't go back.
 
Hmmm

I tend to agree that you should have the upper fwd fuse permanently installed before doing the cowl. I riveted mine early and didn't have that much trouble with the panel install. It also means you have to do the windshield transition after the instrument panel install, and that sequence was all wrong for me.

FYI, I had the pink cowl and used camlocs without any trouble. I had to grind a bit into the cowl core to get the camlocs to fit, but sufficient reinforcement was all it took. Love the camlocs.
 
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