Hot Cowl

kakkenmc · Post by **kakkenmc** » Fri Apr 25, 2008 5:19 pm

Hello,

I have just noticed that the top of my cowl, about a foot from the nose, is hot to the touch after a flight. You can keep your hand on it, but barely. I've also noticed some tiny blisters in the same area and wondering if something is too hot or if this is typical for Maules. Recent annual, oil and cylinder head temps good.
I now have 20 hours solo in my MX7235 and have become Loran proficient.

kakkenmc · Post by **kakkenmc** » Fri Apr 25, 2008 5:20 pm

Oh yeah,

The area is diffuse and on both sides.

210TC · Post by **210TC** » Fri Apr 25, 2008 8:44 pm

Mine gets SO hot you can fry eggs on it. I have a turbo very close by.
Buy some heat sheild and contact cement. Helps deflect heat

jsavage3 · Post by **jsavage3** » Sun Apr 27, 2008 11:34 am

My M-5's previous owner told me the "cowl had oil spilled on it before it was painted" but I've since come to the conclusion that the blisters are from the engine's heat. Even though my M-5's numbers are all good (although she will overheat on the ground if I sit around long enough), my cowl is blistered up pretty good. Bottomline, the blisters are a very common problem on our Maules, albeit, a minor problem.

a64pilot · Post by **a64pilot** » Sun Apr 27, 2008 5:02 pm

It helps to shut it down facing into the wind and open the oil service door, especially if it's fuel injected (vapor lock).

donknee · Post by **donknee** » Mon Apr 28, 2008 7:22 am

The top of my cowl is painted black and it gets very hot, about 20 degrees hotter than the white from just the sunlight. I haven't noticed any blisters, only a couple of spider webs from the spark plug and valve cover right side forward. (was thinking about trying the autolite/unison shorter sparkplugs) After the Iranian revolution in 1979 there was an oil crisis that impacted the price of fibre glas resins. I know the boating industry had real problems with blistering of fibre glas boat hulls. It is a type of osmotic blistering that allowed water to to pass through the outer layers and create blisters of water in the fibre glas. It was not a problem when they used plenty of resin to thoroughly wet/saturate the cloth. Now they use epoxy paint for a barrier coat to prevent the osmosis problem. Maybe it is some "dry" spots in the lay up? Warm and dry on the inside drawing moisture from the outside. Any liquid in the blisters? If it is a similar issue, it would take grinding the bad spots to raw glas and baking the cowl in a tent to get it dry and painting with an epoxy primer. This may not be relevant...never mind.

kakkenmc · Post by **kakkenmc** » Mon Apr 28, 2008 5:43 pm

Donknee,

It seems reasonable that the small 1/8 -1/4 inch blisters are air voids in either the paint or beneath my gelcoat may be heat expanding and forming blisters similar to the osmotic blisters on boats. Just like my boat, my Maule will have to look pretty ugly before I go repairing blisters.

Thanks everybody, I feel reassured that I'm not about to experience a meltdown.

donknee · Post by **donknee** » Mon Apr 28, 2008 7:20 pm

I don't think there is any gelcoat on the cowl. Gel coat is a pigmented outer layer of polyester resin in lieu of paint. When using a female mold, like on a boat, you apply the gelcoat first...then the matt and roving. When you pull it from the mold, voila. I'm thinking of rebuilding my cowl, I just want to be careful not to add too much weight in the rebuild process. Those dzus things get sloppy after a few decades...I'm thinking carbon fibre and kevlar.

a64pilot · Post by **a64pilot** » Tue Apr 29, 2008 7:14 am

Toss the Dzus fasteners while your there. The newer Maules I think come with Camlocs which are far better than Dzus. Get the stainless ones. I replaced mine and they are much better.

kakkenmc · Post by **kakkenmc** » Tue Apr 29, 2008 2:55 pm

My Dzus fasteners had wormed many of my cowl holes too big. Mauleflight cheaply fixed this (in both senses) by adding washers and slightly longer (I think) Dzus fasteners. It doesn't move, but it would be a headache to remove and replace. I don't really like the limited engine inspection on my preflights. I like supercub or champ cowls better. Of course they would blow off when I'm flying almost twice as fast!

maules.com · Post by **maules.com** » Tue Apr 29, 2008 6:33 pm

A big reason for worn through Dzus fasteners is the contact of cowling and airbox at the intake hole. Cut the airbox back so there is no contact and you will save the airbox, the oilcooler flange, and the oilcooler bracket, all of which fail eventually with the engine rotating on it's mounts and the ridgidly fastened cowling.

kakkenmc · Post by **kakkenmc** » Wed Apr 30, 2008 5:49 pm

Thanks Jeremy.

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