RV-7 N117TR - Page 37

crabandy · #**361** 01-08-2016, 06:39 AM

Second time is going much better, sand a little here a little there and then stepping back and looking. The side profile blends much better with the side now.

The top and bottom portion are starting to mirror the round portion behind the spinner.

I'm thinking a little deeper between the inlet and the flat area behind the spinner.

More filler and shaping to go, but I'm liking this shape much more.

Darren S · #**362** 01-08-2016, 07:24 AM

Wouldn't it be easier to just buy a Sam James cowl?

DanH · #**363** 01-08-2016, 07:56 AM

Andy,

Be sure the end result removes all the pour-in place foam. I had poor results any place I left some as core material. The stuff seems to be brittle and exhibit poor crush strength; given flight time, changes in atmospheric pressure resulted in lumps and depressions in the overlying glass.

crabandy · #**364** 01-08-2016, 08:24 AM

Quote:

Originally Posted by Darren S

Wouldn't it be easier to just buy a Sam James cowl?

Possibly, the thought had crossed my mind several times but $$ for the cowl/shipping, and the inlets are lower than I would like on the SJ Cowl. I almost bought the X-Large rings from SJ, but........
-$250 for the pair
-ID is only 5 7/16, I wanted larger albeit only a 1/2ish inch
-Inlet lip radius, I wanted a larger radius on the lip of the inlet

crabandy · #**365** 01-08-2016, 08:27 AM

Quote:

Originally Posted by DanH

Andy,

Be sure the end result removes all the pour-in place foam. I had poor results any place I left some as core material. The stuff seems to be brittle and exhibit poor crush strength; given flight time, changes in atmospheric pressure resulted in lumps and depressions in the overlying glass.

Thanks Dan, yes removing the foam is on my radar. I plan on cutting the underlying portions of the stock cowling out and probably putting a few layers of glass on the inside of the cowl. I thought about using automotive body filler instead of the foam to shape things, but I think it will be much easier to remove the foam than the body filler.

Dorfie · #**366** 01-11-2016, 12:07 PM

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Andy,
Would you mind describing how you got the split between upper and lower cowls so perfectly uniform? Do you have hinges installed down that split?
Not trying to hijack the thread!!
Thanks.
Johan

crabandy · #**367** 01-11-2016, 12:21 PM

It's been a while but I think I used a 3 ft oak 1x4 with sandpaper to get the cowl edges straight. When I installed the hinges I made the split line gap pretty tight and went back with a small jewelry file and filed the split line to the thickness of the file.

crabandy · #**368** 01-13-2016, 11:32 PM

I made some lower attach brackets for the curved center baffling, I used some heavier paper to make templates and get a basic shape. I'm still not sure how this is all going to fit together with the inlets etc so I'm leaving things long so I can trim to fit later.

I filed a slight radius on a 2x4 and used it on my el cheapo harbor freight bending brake but with the radius of the curved part I found a clamp and my fingers did the job for .032.

The lower 2 brackets fit on top of the existing Van's baffling, I plan on nutplates and screws I can hopefully reach with a long screwdriver behind the ring gear support.

I must've got lucky on the first 2 brackets because I've already tossed 2 top brackets in the scrap bin and am dreaming up version 3. Good news is the plenum seems to fit well and is trimmed to the front baffle. I want to verify the clearance from the top cowling before I start drilling holes, to bad the top cowl is "tied up" at the moment.

crabandy · #**369** 01-13-2016, 11:50 PM

I'm finally satisfied with the new shape of the cowling, I think. I bought a gallon of auto body filler to do the final shaping mostly because I could spread it and be sanding in 25 minutes, it was also cheaper but I missed the workability of the west systems. I did add some West Systems and flox immediately aft of the inlet rings. All the foam, filler etc is getting removed after the glass is on and cured.
My reference lines have mostly been sanded out, but they helped me keep things uniform as far as I can tell.

I tried to shape a bump aft of the new inlets to mirror the bump after the spinner as well as fitting into the lower cowling shape.

You can see the left inlet is taller than the right, I don't think it will be obvious on the airplane.

Front shot, as another friend said "Those are kinda big...." Yes, yes they are.

crabandy · #**370** 01-19-2016, 09:20 PM

My latest version of the top bracket for the center baffling turned out decent, but I really should've drilled it on the drill press after bending. The predrilled holes are slightly of after bending, hopefully the next one will be good.

[IMG]//i1137.photobucket.com/albums/n516/crabandy/airplane/E3770EBC-496F-4DA4-9E60-66099B3637FA_zpsgelwqosi.jpg[/IMG]

I sprayed the filler/foam with some leftover spray paint and several coats of PVA and then laid up 2 layers of 8.9 oz glass.

My flannel clad helper is finally old enough to start helping out! I drilled and clecoed an old yardstick as a saw guide and used a flush cut trim saw to cut the split line.

Now to cut the old parts/foam/etc out.

I really should've used more than 2 plys, the split line seemed a little weak so I added a couple layers of glass before I dig all the foam etc out.