'Glass experts: RV-8 Top Cowl refitting advice needed

[Redwagon]

Well I'm starting to pay the price for getting too eager towards the end of build (long story)....phase one is complete with both wife and dog smiling from rides and now looking forward to paint prep etc but I have very very limited fiberglas experience.

I have two main issues with my top cowl, looking for advice on how to approach on fixing.

1. The top of the spinner sits about 3/8"-9/16" below the top of the cowl. This isnt due to sag or anything, it was deliberate skipped during the build process as I was overly focused on the spinner/cowl gap & straightness and figured I could grind the top of it down and reshape (and now having second thoughts). The bottom cowl fits fine, I was much more worried about that.

2. I have milspec camloc fasteners around the firewall/cowl (hinge along horiz parting line) and along the top I have some puckering between the top fasteners. In retrospect I should have reinforced the cowl more along the rear and then allowed for the additional thickness, but it wasnt that obvious or noticable until I started flying and sitting there looking at the puckering from the rear......plus I think with gloss paint instead of flat primer it will be more noticeable from the sides.

Of course one option is to start with a new top cowl, but would have to repeat a lot of effort and that may be a good option.

On the first issue I can:

a. fill in the top corner area behind the spinner and start grinding away and then reglass it. (original plan)

b. Make a cut on each side to lower that center portion of the cowl, push it down, and then glass it into the new position. Might need a lot of blending to make it look right. (thinking this may be better plan)

c. Take off the horizontal hinge, and make a small wedge cut that gets larger forward, although thats going to cause issues on the lower camlocs.


On the mild rear puckering, a few ideas-

a. could reinforce the cowl and build it up, and perhaps bend my camloc retaining tabs down slighty. Having it uniformly a little thicker might look OK and I could possibly put some microballoons on the front top fuselage to blend it better.

b. somehow cut slits to take up the puckering, and then repair. This just feels wrong......


Looking for ideas/advice before the power tools come out........!

Tim

[Redwagon]

The more I think about it the more I lean towards a new top cowl and redoing it right, although ouch on the price of that top piece.

If I do the wedge cut, then I have to move all the camloc fasteners on the sides, perhaps up to 1/8" and then I still have to deal with the puckering along the top.

If I start new I can also reinforce the rear edge of the top cowl more, drill new holes......but lots of repeat effort.

I'm really really really beginning to understand 'repeat offenders' who want to build again due to all the things they learned in the first time around.

Tim

[sf3543]

1 - You could also put an extra washer behind the two lower motor mounts to raise the spinner.
You can check w/ VAN's but I have seen this done on several RVs with no ill effects other than to raise the spinner to correct the same issue you have. It could greatly reduce, or even eliminate the need for glass work.
2 - For the puckering, depending on how much you have, you could fill in the underside of the cowl, with epoxy and fabric, along the hinge line until everything fits flush underneath and then grind down the top. (Just tape up the fuselage, lay up the cowl bottom and then put it in place till it dries. You should get a perfect fit.)

[fstringham7a]

Hi Tim

Pictures would help in giving direct advice......

FG is wonderful to fix compared to metal but ugly to finish and make pretty!!!

Frank @ 1L8 and SGU ...RV7A... Phase 1 @ 19 hours

[Ramendala]

Agree, pics would be great.

For your first issue I think option "B" is the way to go. You can cut the middle cowl where the arc meets the flat on either side and just move it down. A couple layers of glass tape inside and out, some filling, sanding, filling sanding, sanding would do it .

For the 2nd issue cutting the slits would work but you could also fill/fix the holes in the TE of the cowl and drill again. Do only enough to remove the pucker. Much easier and cheaper then starting with a new cowl.

My 2c

Ryan

[flyeyes]

I'm no glass expert, but I can tell you what I did, with advice and help from the local canard guru.

I had the same situation you describe with the spinner low. Mine was about 3/8" and slightly offset to one side. I considered adding washers to the engine mount, but I was very happy after about 180 hours with the speed and handling of the airplane, and was reluctant to change the thrustline.

All of the glass airplane guys who looked at it were unanimous: Cut the offending part off. I considered making two cuts as suggested above, but they just snickered and said it was less trouble to just make a new piece.

With direction and encouragement, I used a pencil to carefully trace around the spinner. Then I removed the top cowl and used one of those little air-powered reciprocating saws and cut the hump off entirely, leaving only the ring behind the spinner, and a little flange on the back side to maintain its shape. Using a cardboard dam taped under and around the hole, I poured some two-part foam in and let it cure (10 minutes maybe) and pulled the cardboard off before finishing trimming the flange off the ring.

20 minutes of trimming with files, rasps and sandpaper had the shape I wanted. I did have to trim a lot of foam out from the back to clear the ring gear and trin the center front baffle.

Then I sanded a few inches out on the cowl, masked the foam very carefully with duct tape and laid up three layers of heavy "biaxial" glass and EZ-poxy (because it's what one of the EZ guys had lying around). Turned everyting over, tore out the foam, and made another layup on the inside to pretty up the edges.

Finally put finish paint on it a couple of weeks ago

This sounds like more work than it really was. Definitely less than starting over with a new cowl. Hope this helps some.

[Redwagon]

Some good ideas, thanks! I've also had the realization that the puckering at the rear of the top cowl is 5x worse in flight than on the ground. So adding a few layers of carbon along the rear to stiffen that up. SHould have done that to begin with......again it was a corner that was cut when on that final charge to get the thing airborne.

For the front fit- Decided to essentially cut a wedge in the top cowl to lower it a bit. I dont want to start a engine 'sagging' thread, but there definitely was some change in engine position from the time it was hung to where it is today. But it eas never perfect to begin with.

The good news is that I am getting some help from some real pros on how to do this......and it'll be a superior result than me thrashing around on it.

All goodness.....

Tim