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08-05-2013, 08:49 AM
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Join Date: Jan 2005
Location: orinda, ca
Posts: 23
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cowling fit
What to do here?, looks like 2 to 3 degrees between flange and spinner. Will the engine sag that much? I saw somewhere that a guy with another model had the same problem and cut the whole flange off and reglassed it, is that recommended here? If I do that will the bottom need to be cut as well?
[IMG]  [/IMG]
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08-05-2013, 09:43 AM
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Join Date: Jun 2006
Location: Freericksburg, VA
Posts: 624
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I wouldn't do anything as my engine sagged at least enough to end up parallel once it "settled in. But my plane isn 't a prize winner so take that for what it is worth.
The bigger question is how did it end up that way? Did you put a spacer ring behind the spinner mount when you cut the cowling to fit. At this stage you could retrim the rear and get it parallel with the spinner mount. You' probably have to drill some more holes in the mounting hinge at the rear but you will have plenty of chances to fill the extras when you finish it.
No need to modify the flange - it the rear trim that is the issue here.
BTW - I just repainted my cowl after repair some damage and improved the fit at the front as well. After both halves are mounted and all hinges mounted I joined the halves together off the airplane and added 3/4 layers of glass to the back side of the front outlet edges essentially gluing the front pieces together. After cured I used a small cutoff wheel in a dremel tool to cut them apart on a straight line after using dry micro to get a perfect fit and shape to the inlet. Then you end up with a perfect match in this difficult area.
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08-05-2013, 10:17 AM
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Join Date: Jan 2005
Location: orinda, ca
Posts: 23
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I have not trimmed anything yet, just laid it on top so it is overlapping the top of the fuse, shimmed the front up to line up with the spinner and saw the alignment issue.
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08-05-2013, 10:35 AM
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Join Date: Mar 2005
Location: Bainbridge Island, WA
Posts: 333
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not following you - confused
Are you referring to the narrow gap on top, and wider distance between cowl and prop flange at the bottom? Top to bottom? That is the way mine is, and all the others I've seen. Mine also was wider on one side than the other, so I thinned down one side, and built up the other. I had to add glass/epoxy layups to the back on the thinned down side; both top and bottom. The wider gap at the bottom makes it easier to remove the lower cowl; less paint damage over time. For removal, the top cowl can be lifted straight up, but the bottom must be pulled slightly forward.
Otherwise, my engine cowl parts were well made, and fit pretty well; no complaints.
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Brian Vickers
Bainbridge Island, WA
RV4
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08-05-2013, 10:36 AM
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Join Date: Sep 2006
Location: Douglas Flat, CA
Posts: 589
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Airplane Bondo!
I would just:
1. Mix up some epoxy and microballoons
2. Pile it on the flange to fill in the gap between it and the spinner
3. Wait for it to cure and sand to contour
3. Add a layer of thin glass over the top
3. Be done in a couple of hours
Thanks, Bob K.
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Bob Kuykendall
HP-24 kit sailplane
EAA Technical Counselor
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08-05-2013, 03:50 PM
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Join Date: Oct 2009
Location: River Falls, WI
Posts: 38
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Too soon to tell.
If you have only laid the top half in place I don't think you should be cutting off anything or using bondo yet. Fitting that thing is exasperating. When you get the the two halves together, tacked in place as best you can and have done some of the required cutting to get it close, you may have a better fit or at least a more rigid and fixed cowling that you can then modify if required.
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08-06-2013, 06:58 AM
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Join Date: Dec 2006
Location: Portland, OR
Posts: 827
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Cowl gap
Exactly what Brian said. The fit will get a little better when the cowl is aligned with the fuse skin, but this is normal.
I would strongly suggest you bondo a spacer on the front face and off the top of the top cowl to use as spacer guides to the spinner back plate. It's the best way to reproduce the cowl position as you take it off and on MANY times during the trimming process.
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Long-EZ built 1985 -> Sold 2007
RV-9A; N539RV First Flight: 7/2010
RV-8A N468DL 40 hr Flight Test Program
Building Log: www.mykitlog.com/n539rv
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2017 Paid
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08-06-2013, 07:56 AM
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Join Date: Jan 2006
Location: Tucson, AZ
Posts: 818
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Cowl fits
Welcome to the ?fit the cowl club.? Mine was very similar to your situation. He is what I did.
First fit and trim the cowl so that it is attached to the firewall and the two cowl halves are attached. Leave ~1/4-3/8? clearance between the back of the spinner and the nose of the cowl. The greater the clearance the easier it will be to remove the lower cowl. I set the spinner proud by about 3/16? for engine sag. My engine was on the mounts for ~2 months prior to fitting the cowl. After 4 years (2.5 flying) my sag was a total of ~1/4?. So now the spinner is no longer above the cowl but below by ~1/8?.
The nose of the cowl sloped away for the spinner and I had to build up ~1/4? on the bottom cowl tapering up to the top cowl. I bonded some balsa wood to the front face of the cowl. ?? in some areas, less in others. I then glued some sand paper to a flat piece of wood to make a flat sanding plate. I sanded the balsa wood until I got the nose of the cowl proper. I intentionally sanded back an additional 1/16? so when I glassed over the balsa wood it would be at the final gap with spinner.
Contrary to a few posts you should have several layers of glass over the nose.
I didn?t have the prop on when I fit the cowl, I used a spacer adapter to simulate the prop hub. Having the prop on may make things a bit more challenging.
FYI I have a Hartzell BA prop.
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Dream it, Build it, Fly it
Paul Merems (EAA Tech Counselor, EAA Sheetmetal Workshop Instructor/Volunteer 12 yrs)
ExperimentalAero- HANGAR BANNERS
www.experimentalaero.com
RV-7A (Flying since 2010)/RV-4 (sold 1990)
Tucson, Arizona 85749
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08-06-2013, 09:19 AM
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Join Date: Jan 2010
Location: Ottawa, Ks
Posts: 2,188
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I drilled and clecoed some aluminum angles on the top of my cowling to lay on top of the spinner backplate to hold the front vertical position. I glued some Popsicle sticks to the front for my 3/8 gap. When I fit the rest of the cowling to the fuse my gap behind the spacer was uneven like your pic shows. I was going to buildup the front face of the cowling with west systems micro light, but I didn't want all the sanding and a huge glob of filler.
Instead i Installed the cowling, and used a die grinder to cut the cowling about an inch back from the lip. I left part of the lip attatched to the cowling that had the proper spacing. Then I clampd the lip to the spinner backplate with the proper spacing of Popsicle sticks and installed a couple of fiberglass strips to hold things in place. Removed the cowling and glassed/filled the gap that I had cut. I put most of the fiberglass on the inside of the cowling so it didn't have to be as smooth.
Sorry no pics, it was intimidating to cut into my cowl like that but I think it was much easier in the end to have the spacing behind the spinner set and just fill 1/4 cut on the cowling.
Last edited by crabandy : 08-06-2013 at 09:22 AM.
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08-06-2013, 07:23 PM
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Join Date: Apr 2011
Location: Cincinnati, OH
Posts: 2,791
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old style cowl
my old style cowl (no pink) was the same. I used fiberglass layers to build it up, up to 1/4 inch in some areas. it was a real effort sanding to final dimension but it's solid. covering with softer material and covering with glass may be a easier method.
__________________
Steve Melton
Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 800+ for all
Simplicity is the art in design.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com
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