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RepmikeBrown

Well Known Member
I fit my top and bottom cowl this weekend. The cowl wouldn't lay on the firewall without pushing it down in the center. It was really tough pushing down, marking, cutting filing, re-filing 1001 times to get that just right fit. Afterwards I pulled the pins across the top of the firewall and down the sides on the bottom cowl, removed the cowls, filed the corners of the hinges. I cut a small door to access the hinge pins on the top. It's impossible for me to install by myself, I can get the hinges started together on the lower ends but the top bulges up where I need to start the pins. Pushing down in the center makes the ends pop out. I'm ready to run a 1/4" saw blade down the middle and relieve some pressure and reglass. Has anyone else done this or will the fit I have now relax itself and finally conform over time? I've searched the archives but failed to find an answer. Any help here on previous builders solutions would greatly be appreciated.
Thanks Mike

 
I know of at least one RV-3 with pretty much that same cowl that had to cut a series of slots and reglass, for that very reason. I'm not far enough on mine to have any experience with it yet myself.

If I understand it, the RV-4 and the RV-3 use the same cowl but the RV-4's is several inches longer.

Dave
RV-3B, building the fuselage
 
My experience was that the cowl relaxed a bit after the first few flights (heat cycles, I imagine). I don't know how much of a fit/shape problem could be corrected that way.
 
Mine was a similar experience getting the fit right, and it did require 3 hands and a hammer at first. After a few hours of flying, and cowl on/off, it settled in nicely. you will need to learn the best method of hinge sequence,and how to hold your mouth just right! Looking at your pics, I will speculate with the spinner /prop installed, you will be pretty close at the forward end, as the lower cowl needs to drop down at a slight angle. Also, I started with my gear leg cut-outs tight like yours, and ended up making them much larger, as the intersection fairings will cover them, and you will need that area to pull the cowl down...remember, you dont have your gear leg fairings on yet. The hinge pin ends and technique to lube and insert them will also help you. I use a parifin based door hinge lube called "door ease" which looks like a big chapstick tube..no mess and works great. I also have a small cut-out at the top/center for the upper firewall hinges. Need to make sure they are safetyed (I use tie wrap) as well as the lower cowl side hinges, or they will shift into adjacent structure during flight. ..feel free to PM if you need any other suggestions...keep building!
 
Cowl pins

I used stainless steel welding rodso for my pins. They are just slightly smaller. Slide in and out very easy
I had grab rings brazed on. On long pin and one short pin, both accessed through oil door.
 
cut

Mike,
I have installed 2 new cowls to exiting airframes and several other glass work jobs. The fiberglass does not expand or contract with time or heat.
It will or can soften and reset but not much. If the parts don't fit or go together now, they will not later. Trim and re-glass....
Just my 2 cents.

BTW, your works so far looks nice. Those nice fits don't come easy.
 
If the parts are epoxy they will soften with heat. You can make them take a different set by squeezing or stretching with straps as required, then heating the highly stressed areas with a heat gun, carefully.
 
Big thanks

Thanks for all the replys.
The fit is good while it's clekoed down, so I think I'll try a little from the guns and let it set for day. If it doesn't settle, I'll just cut it and reglass.
Thanks again.
 
RV-4 cowl fit

I fit my RV-4 cowl too high/tight. I had to cut a seam & re-glass it to give it enough room around the headers to keep from scalding. It was a lot of work, but really helped. I don't remember exactly how I made the cuts and I sold the plane so I don't have pictures. sorry. I know it was about 3/4 of the lendth and probably rand just above the bottom corners so it was more dropped than wider.

-Bruce
 
Same here

Same here ? big hassle at first

The radius of the aft edge (side to side) of my top cowl was tighter than the radius of the firewall, and at first I had to stand on a stool to exert enough downward pressure to get the two top pins started. I operate the pins by reaching inside the oil door, which is hard to do while pushing down on the top. Don?t worry about it because over time it does relax and get much easier. Now I can do the whole top cowl on-off by myself, but it helps if an assistant pushes in on the left side, right where the cowl cheek radius starts (end of pin/hinge). Like you, my left side bottom corner flairs out slightly when I push down. Just enough to hamper the pin from sliding through the last two hinge eyes. At my hanger I have a 10 inch thick block of wood (end cut from a glue-lam beam) that I stand on to install the top cowl. The long leg RV-4?s are pretty tall.
 
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