Davepar

Davepar

Well Known Member
The cowl instructions are rather confusing. I'm trying to figure out how to do the trimming for the horizontal seam between the top and bottom cowls. Do I trim the top cowl at all, or just trim the bottom cowl to the top one?

I was expecting the cowl to be as difficult as the canopy, but it's been a breeze so far. It's much easier to maneuver, cut, and sand, and it doesn't crack as easily.

Thanks,
Dave
 
I sort of figured this out on my own last night. The plans are apparently out of date versus the newer epoxy cowls. They mention a mold line on the bottom cowl which doesn't exist.

On my cowl, there will not be much overlap between the top and bottom halves, maybe 1/2". I'm just going to trim off the thinned edge on the top and bottom cowl halves and straighten up the edge. I'll then fit the halves to the fuselage and make additional trims as needed.

Dave
 
Hi Dave


I see you figured it out, so this may be useless info, but here it is anyway. What I did, was to carefully cut down the outside, front cheeks of the lower cowl around the front, and heading aft about 3-4 inches. This would allow the inside part near the spinner to come together, and the outside parts to overlap (see the figure below).

Once this cut is made, I was able to duct tape the lower cowl on the airplane, and start working on the cuts at the bottom of the cowl first (which allows you to raise the cowl into the proper horizontal position). Once that was done, I had marked the fuselage where the bottom of the top cowl was at the aft end, and I could see the bottom of the top cowl was at the front. I just connected the dots, drew a line on the bottom cowl, and took it off to cut.



cowlcut.jpg


(This is an edit after reading Mickey's response below).

Jim Daniel's did the same thing as me but was smart enough to take a picture of it. (I hope Jim doesn't mind me providing a link to his picture here) Note that the cut is made on the bottom cowl half and provides an overlapped lip that can be trimmed.

picg.jpeg


Cheers
 
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Cowl

I got some great hints from Jim Daniel's website. He's got 4 articles on how he did his cowl. It seems to mesh with what Mark writes above. I have to admit I didn't quite understand some of it until I saw Mark's drawing!

http://home.comcast.net/~jwdweb2/Cowl1/cowl1.html

I've only barely started on my cowl. I hope to get back on it in a few weeks.
 
That's a great web site. Thanks for the pointer. I remember reading it when I was considering Camlocs, but it also has some good pics of the cowl fitting process.

I have the same step at the front of the cowl behind the spinner. (I call it an over-bite.) I was able to improve it a little bit by sanding the inside of the top cowl and outside of the bottom cowl. I'll just have to build up the bottom with some filler. It's good to know that's normal.

The horizontal seam at the front of my cowl will need very little trimming. Maybe just a pass or two with some sand paper. I guess there was a flange on older cowls.

Thanks!
 
Cowl trimming

The drawings are a bit confusing indeed. I trimmed the Top cowling first until I had a reliable reference plane. Fitted and trimmed the aft edge with the plane. After that I trimmed the nose/spinner area, placed the cowl on the plane, trimmed and fixated the bottom, trimmed and fitted the sides and lastly trimmed the seam between the cowl halves. Worked great. Very important: make yourself a 1 meter file from a plank and sanding paper. Only way to get those edges straight. Do not forget to build in an allowance for future engine sag; I chose 5mm. For details and pictures: http://websites.expercraft.com/PHVII/index.php?q=log_entry&log_id=8267 and beyond.

good luck!

Ren? Bubberman

PH-VII | RV-7 | Tip-up | Fadec

Firewall Forward

http://websites.expercraft.com/PHVII/
 
Excellent write-up Ren?. I especially like this tip for the horizontal hinges: "If you end the lower half of the hinge without a tab at the firewall side it will be easier to remove the vertical hingepins." I hadn't thought about that yet, but it makes perfect sense.

Let's see... 5mm is 0.196850394 inches, which is about 3/16". I'm doing about 1/8" sag, so we're roughly the same.

Dave
 
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