i am having a small issue ok that came out wrong i'll start over.
I am starting to notice that the lower cowling is begining to show signs of heat stress. you can see the fibers of the cowling coming through. Lu of maule west suggested a heat shield of some sort. i have never meet Lu but he seem to know his Maules. I was wondering if other have had this issue and what fixes are available. thanks Peter
I have a turbo inches from the top of the cowl and have seen paint bubble from heat. However, I have not seen the glass deteriate to a point that fiber was exposed.
I recommend cleaning the surface with Berrymans B-12 Chemtool in a spray can. You can find this product at almost any parts store. Spray this on a clean rag and use the rag to clean the suface (clean several times). Then apply a coat or two of resin w/hardner (can pick-up at the parts store), this should cover up all the fibers.
Order some reflective heat shielding from spruce, get the thinest that is recommended for this application and of course you will need some contact cement.
Also, you may need to cut the fibers to get them to lay down, if so, use a razor blade.
I'm no fiberglass expert, I just own two planes with HOT glass engine covers SO, get some other advise
AND MAKE SURE IF THIS SHIELDING FALLS OFF IT WON'T EFFECT SOMETHING ELSE, AS IN CLOG THE INTAKE OR ??????
A64
Did these things come with polyester in the begining or?
Can you put epoxy over polyester?
I have never asked this or heard about it. Been on the farm to long
All cowlings manufactured before 2003 (+/- ?) were all layed up with Polyester resin and fiberglass. Not just any polyester resin...FAA Approved High Temperture Polyester Resin that had to go through a lot of testing to pass flameability.
All cowlings manufactured after 2003 (+/-?) were layed up with Vinyl Ester resin and a fiberglass/carbon/fiberglass sandwich. Manufactured by LoPresti Speed Merchants at http://www.speedmods.com , these cowlings can be identified by the data tag located inside the cowling. If repairs are needed be sure to obtain the correct FAA approved High temp. materials.
David Wright
Wright Aircraft Technology, LLC
151 D W Wright Road
Moultrie, GA 31788
If my guessing is correct, the problem on your cowling should be located at the lower right side of the bottom cowling. If this is correct, you are not the first to have this problem.
The fix has already been approved by FAA and is on the Maule drawing for your cowling installation.
When I did the drawing for Maule, I made the installation of a heat shield optional, I wish I had made it manitory as this problem seems to be more common than it should be. The LoPresti cowls are the only ones that seem to have this problem.
Let me know if I can be of futher assistance.
David Wright
Wright Aircraft Technology, LLC
151 D W Wright Road
Moultrie, GA 31788
Oops,
Mine was repaired with epoxy bought from Spruce, and to think, I had the proper Polyester resin in 55 gl. drums. My fiberglass expert examined it and declared it to be epoxy. If it starts to delaminate, at least I'll know why.
Hey,
I got an idea, bring it to the fly-in and get David to fix it.
The gratitous advertising for te fly-in will only get worse as the time draws nearer.
As David suggests the heat is at the rear of the right muffler on the 540 engines. The worst of all is the 260hp.
If it has'nt yet fractured, then a layer of silver heat material as seen in many turbocharged engine bays should work.
An added culprit is the external air pressure forcing the centre of the bottom cowling upwards and thus pulling in the sides at the rear of the muffler.
First, it pulls the composite closer, stresses a complex formation area but worst of all does not allow full flow cooling air venturi effect, thus the result is a hot running engine.
I have added a steel stiffener to keep this composite area in a straight line as it should have been from Lopresti.
I must have mispoke, the lower cowling damage is right where you speak of but not nearly as bad. i am still waxing its cleaning shiny finish where the damage is. it is not even noticed by the untrained eye or much by me while washing the plane but i can kinda start to see what the cowling sandwitch is made of. the problem is that i see it progessing into something that will need to be resurfaced and i don't want that. so what does someone w/a turbo or someone w/this problem protect the inside of the cowling with??
As a trial to stop progression, you could try siver builders tape which is about 6" wide and place a couple of strips on the cowling beneath the muffler area.
Very carefully clean the surface to be covered from grease, gas stains etc before applying.
I would also fasten a stiffener across the air egress venturi to keep it straight. Think in terms of 150mph wind being held back or diverted by a bit of thin composite.
Jeremy,
Could you post a photo for the stiffner? I think all would like to see.
I wish I had my spruce catalog, I could give the part # for the stuff i have used.
It's very thin and has silver (foil type) on the side that faces the hot part (exhaust or turbo). It is between 1/16 & 1/8" and up to 1/4" thick.
The silver creates a reflective heat shield. You need an "air gap" between the hot part and the reflective surface (the ability for the product to keep heat away will diminish as the hot part gets closer to the reflective shield, if it comes in contact with the hot part it's effectiveness will drop by about 60%, so you need a small air gap. I think Jeremy's point is that the cowl can press up to the muffler as the air speed increases and also reduce the amount of exit area that heat can escape out the bottom of the cowl) adding stiffner stops this..
Another product that is Superb is made of ceramic insulation with a stainless cover or shield that you can place on the source (muffler). You only need enough to cover the bottom 40% (guesstimate)and you can saftey wire it to the muffler. You can find this at the hot rod shops. I think I would rap the hole thing to cut down on all the heat in the cowl and by saftey wiring you can remove each year for inspection. Some good points about rapping Vs glued heat shield. The heat shield is on the bottom of your cowl and all the oil,gas and trash is going to effect it and it will fall off every year or two. The cover on the muffler will be more effective and longer lasting with less hassle. I put reflective heat shield in the TOP of my cowl because I have a turbo and many hot components around it, making it almost impossible to wrape. If you look at my rocket exhaust (engine picture) on my site I wraped it with a heat shield because It was simple and reduced overall heat, It I had a muffler I would wrap the hole thing. Now, we have the FAA, so it's up to you and your IA/A&P.
Why not just incorporate the FAA approved fix that is on the Factory drawing? I have no idea what it is, but it is IAW the factory drawing. I won't get into the legality issue because that get's emotions involved, but if you start incorporating home brew fixes, even if it is better than an approved method, it at least de-values your airplane.
A64
You are correct. I am sure you too have learned over the years that some proper fixes are not necesssarily the best.
An IA/A&P cannot under any circumstances do things differently than the book without a 337. This is why I did not get my A&P 30 years ago. I HATE WORKING WITH THE FAA. I will add that 30 years ago I knew some wonderful and very smart people at the FAA, now I can't beleive the idiots I have meet with ZERO integrity.
My dander is up whenever I talk about these bozoo's. Forgive me for my thoughts.
Anyway, ALL of the folks that have a pilots lic know what is right and wrong in the eye's of the Faa.
What makes this site so great is that we exchange many idea's and we all learn from it. We don't have to follow it and if I had a repairmans lic I could not write what I do. I know some of you A&P/IA's would like to say things you can't, most understand this so let's keep the input coming in.
And all the comments that come with them.
I will post a picture of the turbo HOT area soon on the turbo thread.
ok that came out wrong i'll start over.
