Forming aluminum for a cooling outlet fairing

Bob Axsom · #1 03-10-2012, 08:53 PM

Gereed75 presented a fiberglass fairing that he made for the cooling air outlet that looks really good in a thread about exit drag. I would like to make one out of metal. It would have to conform to the radius of the cooling air outlet at the two corners. I can fill at the corners where the outlet turns out to blend in with the bottom of the cowl with fiberglass/resin/flox as necessary. One approach would be to make a wood forming block and beat it into shape. Another would be to fabricate it out of multiple pieces with no more than one bend on a part. And yet another way would be to build it out of fiberglass as Gary Reed did. Any good thoughts on how you would approach this?

Bob Axsom

hydroguy2 · #2 03-10-2012, 09:13 PM

I'm on it Bob. I'll be at the hangar tomorrow attempting the same thing...out of metal.

Bob Axsom · #3 03-10-2012, 11:48 PM

I've got myself into a task with the American Cancer Society that is going to tie me up for a while. I have 650 pages of real time notes hand written into these little pocket notebooks that I have to copy and reproduce 4-to-a-page to accompany a lot of other material that I previously submitted. At my current rate is is going to take 33.5 manhours. Well back to work.

Bob Axsom

g zero · #4 03-11-2012, 09:41 AM

Order some 6061 type 0 from Air Spruce , 2x4 sheets or smaller are cheap to ship. This hardness is easy to work ( think lead soft ) . Scoops can be formed over PVC pipe . Wood tools can be custom cut on the band saw. A little practice and you be making wheel pants in no time !!

Bob Axsom · #5 03-11-2012, 12:37 PM

I have bought a lot of aluminum from Aircraft Spruce over the years and I have more than enough left over for many of these farings but the easier to work with 6061 type O sounds very good. I'm just going to take a shot at thickness maybe 0.040".

Bob Axsom

#6 03-11-2012, 01:01 PM

English Wheel

Bob Axsom · #7 03-11-2012, 01:27 PM

I havd seen the work Jim Younkin has done on his english wheel and this seems like a different kind of work to me. I ordered two sheets of aluminum of "0" treatment/hardness... (they used to have more information in the catalog). One is 6061 bare 0.040 and one is 2024 alclad 0.032 - both are "0".

Bob Axsom

Omega232Devils · #8 03-11-2012, 01:39 PM

Hi Bob!
Gary has started an epidemic with this fairing! Haha. I talked to Gary a few weeks ago before this fairing picked up steam again. I made my first mockup out of cardboard, then used it to trace my pattern on scrap. 02 aluminum. I was going to use this as a test piece, but was too flimsy so I used the .02 piece to cut out .032 and formed that with some pliers, hammer and my work bench. Not pretty, but will allow me to test the fairing before permanent install.
Unfortunately I do not have test data as I had to rebuild a cylinder. Once I get the cylinder broke in I will test the fairing. My plan is to attached it with two screws into nutplates on bottom cowling and use speed tape to keep flush with fuselage for testing. If all goes well I will make a prettier one, paint it and permanently attach it.

Why alluminum? Because I have never glassed before. Otherwise I believe I would make it out of fiberglass.

Dan

terrye · #9 03-11-2012, 01:45 PM

Kent White has lots of good stuff here on forming metal. Tools, videos, workshops:https://www.tinmantech.com/index.php

Bob Axsom · #10 03-11-2012, 03:50 PM

Paul Mosher I think I was too quick in dismissing the english wheel. You were probably right on the money I think after looking at the Kent White stuff Terrye referenced. There is a whole field of expertese that I never really appreciated. Finally, Dan that is exactly how I normally go about it except I use file folders (a box full usually lasts me a few years) to make my patterns. Using the soft aluminum that g zero recommended this should go well. I like the aluminum approach because of the heat involved - I will not rule out stainless steel if I need to go that way.

One way to interface the outlet of the cowl will be to step down the fairing/extension and run it inside the outlet and tie the two together with platenuts, flathead #8 screws and dimpled washers. I can pick up attach points on the bottom of the fuselage in similar fashion. Placement will be tricky to avoid foot contact problems. But if it doesn't work out I can just fill the dimpled holes with flathead screws. Let's see how many days until the 31st ...

Bob Axsom

P.S. Dan that looks pretty darn good to me.