Carbon Fiber Cowling for my ULPower 350is powered STOL CH-750

I was told my cowling is the third one off the molds from Aviation Composites.  I'm starting this thread to show chart my progress with installing it.

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The AerThe AERO-Classics LTD Engine Oil Cooler looks like its going to fit better than the factory supplied oil cooler. (P/N 8000081, 10 Row Drawn cup)  I got lucky and found this one new in the box on Ebay.

Hello Timothy: I like your carbon fiber cowl. What is the weight difference between the Zenith cowl and the Aviation Composites cowl? How well does it fit (right out of the box)? Can you provide contact information for the person you dealt with at AvComp? What sort of lead time did you experience in obtaining your cowl? Biggest question - Cost?   Richard Kaczmarek

I haven't put my cowling on the scales. But when I first saw photos of this design on facebook, 12 pounds was the number quoted.   I don't know what the factory cowling weighs.  I had Zenith delete it from my FWF order. There's a lot more work getting this to fit versus the factory cowling. 

$1200 plus LFT motor freight shipping.

Thanks for the prompt reply, Timothy. Please keep us posted on your cowl fitting process experiences. I'm not even close to that part of my build, but I'm a firm believer in learning from the experiences of others - both good and bad! Thanks again.


Placing the cowling on the fuselage was a bit of  set back.  I'm building from plans and I trimmed my top cowling to extend 50mm past the firewall.   The plans don't have any dimensions listed.  But I figured that would be long enough.  But this cowling is too short!   I pondered my situation for quite a while.  Do I make a new longer top cowling or do I make the cowling longer.  

What went wrong here?  The cowling was designed for the ULPower engine and the Zenith firewall.  But, the cowling maker / designer didn't have the right engine mount when calculating the proper length of the cowling  The top tubes on the ULPower engine mount extend ~25 inches.   This cowling is the third one off the molds.  The other two didn't use ULPower.  They used much heavy engines with shorter engine mounts.  I've had a chat with the designer and this issue has been corrected for future buyers.

While considering the idea of making the top fuselage cowling longer, I said to myself I'm going to make the instrument panel bigger so the avionics fit where I want them to fit.  Long ago I decided to use Garmin 3X Touch for avionics.  The 10" display doesn't fit very well into the stock instrument panel.  I've also considered using dual 7" vertical displays.  Placed the seat parts in to the ariplane climbed in.  I want my HSI display to be centered between my eyeballs.  I want my head to be looking straight forward.     I planned on 3/4" of space required from the corner of the display so there would be enough space for the backing plate, and a fold down hinge on the bottom of the panel.   New instrument panel form block made and a new panel is born.

Metal is expensive and paper is cheap.  So here's the paper version of the new top cowling.

I eventually decided it would be smarter to extend the cowling rather than extending the top cowling.  I would also have to deal with extending the forward cabin sides.   So, I took some left over 0.020 and started celcoing that to the cowling to make the cowling longer.  My first attempt at making these extensions was with 8" strip of metal.  It didn't fit well, so there was a redo in paper to get the curves right, and then I added a 12" strip to the top and bottom cowling.  The celcos will go on the other side when it's time to do the layup of epoxy and cloth.

Two layers of 6 oz cloth is ready to be applied to the inside, and then I'll remove the metal and do one more layer on the outside.  The first two inches of edge have been sanded down to wafer thin.  There will be an inch of overlap between two layers.

The cloth was laid down first on a sheet of 8 mil plastic then the epoxy was poured on.  I'm using medium viscosity laminating resin and medium speed laminating hardener from PRO-SET.  LAM-135 and LAM-226.  There's plenty of working time to get this placed out.   Another layer of 8mil plastic covers the cloth and epoxy so rollers and squeegees can be used to get the cloth completely wet and not have excess epoxy.   After placing the wet cloth, peel pile is placed on top and you can squeeze out a bit more epoxy that way.  Plus you get a nice finish when its removed.  The white stuff is dacron cloth.  The peel pile wasn't that wet so I didn't get used.  Dacron can be pressed on to of the peel pile if there a lot of excess epoxy.

After removing the peel pile and the metal the result looks like this: ...  The inside has a nice texture from the peel pile and the metal side is really shiny with just a few lines from the packing tape that I covered it with.  Epoxy doesn't stick to packing tape.  But all of that shine is for nothing because it all has to be sanded down so the top layer will stick.  The original edge will be sandwiched between layers.


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