And so it begins

[skywagon8a]

Have you considered the flammability of the resins you are planning to use with your carbon fiber? Long ago when we were certificating the Twin Bee, we had to prove to the FAA that the fiberglass cowls would not support combustion. The test involved aiming a blowtorch at the vertical section of cowling until it was burning. Then removing the blowtorch with the fire self extinguishing. Initially, using convention resin materials, the burning continued. This required adding a third chemical to the resin mixture which caused the finished product not to support combustion. The FAA was only concerned with the resins used surrounding the engine compartment not elsewhere on the airplane.

Perhaps the resins available today do not support combustion? I don't know. Whatever you use, it would be a shame for a close exhaust to ignite the resins and continue burning.

[supercub83a]

You could also use metal tape on the carbon where it is close to the exhaust or a shroud around the exhaust.

I used pink foam from home depot for my smaller, lower cowling but painted it with two coats of water based latex paint before the bondo. That prevented the bondo resin from melting it. Epoxy resin will not melt the pink board foam; however.

I had considered doing exactly what you are doing with the expanding foam. Please keep us posted with lots of updates and pics!


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[Mr. Ed]

https://www.aircraftspruce.com/catal...heatshield.php

Perhaps a layer of this stuff would work. Says it reflects 80% of heat up to 3000* and will withstand continuous 1100*.

[rc dude]

I've used this stuff before for Formula SAE cars to stop heat going through the firewall and heating up the gas tank, and it works well. It's also less weight than the mat you linked to and comes with adhesive applied to the backside, although the max temp is slightly less. This is what I plan on using when I do a carbon cowl for my plane.

https://www.pegasusautoracing.com/pr...sp?RecID=11221

[Mr. Ed]

I laid up the carbon fiber air filter tunnel and dome. Thought it would look better with a beaded lip so I glued a piece of .25” foam cord on flush with the inside of the lip. Then faired the outside with micro bubbles and covered with a couple layers of carbon fiber.

The cowl is ready for lay-up but I’m searching for a suitable resin. I’ve been using West Systems 105 but it won’t take the heat without getting soft. Flammability is also a concern. If anybody has a suggestion I would appreciate it. I don’t have the ability to post cure in an oven…the mold is formed on the plane.

[Mr. Ed]

Back at the project after almost a month off. I did the lay up on the lower cowl and should have the upper sections done this week. Four layers of 3K twill. Shark gills will be added later.

[supercub83a]

Did you find a resin that is capable of higher temps than west systems?


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[Mr. Ed]

Pulled it from the mold and did an initial trim. The rest of the cowl will be laid up tomorrow.

[Mr. Ed]

Turning out ok with a couple spots that need a little fixing. Once those are addressed I can make the cuts for the hinges.

[Mr. Ed]

Modified the nose bowl by making the inlets slightly smaller on the prop flange side and making it fit the profile of my spinner. Since the center area will be covered by the spinner I trying to come up with a method to attach the upper and lower sections of the nose bowl once I cut it in half. If anyone has come up with a good solution please share photos. Thanks.

[Supercubrancher]

What did you use for a mold to get the shape for the top of the nose bowl?

[Mr. Ed]

What did you use for a mold to get the shape for the top of the nose bowl?

First, I bonded into the cowl openings a flat sheet of carbon fiber, traced the final shape I wanted the opening to have and used a die grinder to cut the shape. Then I just taped a plastic sheet around the area I wanted to modify and poured in expanding foam. Once it was set up I shaped it with sand paper. I traced around the spinner base on a piece of cardboard and put that on the prop flange and traced around the cardboard onto the foam and nose bowl to get the final profile.

[Olibuilt]

I trying to come up with a method to attach the upper and lower sections of the nose bowl once I cut it in half.

I have a CubCrafters split composite cowling and I’ve only split it once for maintenance. I better like to remove the prop and the complete cowling to have access to everything when needed.

Mine has 1 upper part that goes over 1 lower flanged part, with screws and nutplates. Machine Screws and 2 aluminum threaded vertical flat bars near the prop spinner.

[Mr. Ed]

Thanks Oli.

The issue I have is the spinner is rather large, 14 3/8” diameter. I was planning to do something like you have but realized the screws would be behind the spinner and thus not accessible without prop removable.

[bcone1381]

Modified the nose bowl by making the inlets slightly smaller on the prop flange side and making it fit the profile of my spinner. Since the center area will be covered by the spinner I trying to come up with a method to attach the upper and lower sections of the nose bowl once I cut it in half. If anyone has come up with a good solution please share photos. Thanks.

I would fabricate a fibergalss flange to join the two halves. First I would plan on a method to mate the upper and lower parts together before I make the big cut with my bandsaw. for example, for temporary mating I envision a 2" wide strip of .025 Aluminum match drilled and clecoed to the outer cowl surface over where the big cut will be made. Actually, I like four places where the cowl can be re-assembled...the outboard and inboard areas of both sides.

Then I would disassemble it, and cut it on my band saw.

Then I would put apply a mold release product to the upper cowl part along the seam. Use smooth 3m packaging tape for this mold release.

Then I would reassemble the two parts and apply epoxy impregnated fiberglass cloth 2 or 3 inches on both sides of the seam.

I like rutan 7725 bidirectional cloth. One layer of cloth has about the same strength as .010" thick of Aluminum. SO if you migh twant the strength of .060 AL you might use 6 layers of this 8oz cloth. Let this cure up, then disassemble the pieces. The upper part of the fiberglass will match the upper cowl, but it will pop right off because of the mold release packaging tape. Lastly, trim the oversize flange to a desirable shape and size. Sand the edges smooth. Match drill the two pieces through the flange and install your fasteners. Maybe tinnerman clips?

[skywagon8a]

Thanks Oli.

The issue I have is the spinner is rather large, 14 3/8” diameter. I was planning to do something like you have but realized the screws would be behind the spinner and thus not accessible without prop removable.

Insert the fasteners which are behind the spinner from inside using either screws or AN-3 bolts depending upon which type of tool works best. Attach plate nuts outside the cowl hidden behind the spinner.

[Mr. Ed]

[QUOTE=skywagon8a;852417]Insert the fasteners which are behind the spinner from inside using either screws or AN-3 bolts depending upon which type of tool works best. Attach plate nuts outside the cowl hidden behind the spinner.[/QUOT

Good idea! ��

[Mr. Ed]

I split the nose bowl. It will be held together by two screws on each outboard section (where you can see the pink silicone pull from the Click Bond nut plate) and two pins on each side of the center section. The sections have been sprayed with Eko Fill for UV blocking and primer. Paint will wait until I’m ready to paint the wings.

[Mr. Ed]

Starting to come together. I should have the rubber baffle seals all cut tomorrow.