metal naca duct for polished planes

[sonex892]

I've been working on fabricating some metal naca ducts out of 6061 to replace the inadequate standard ones. It gets pretty hot here in Australia.

I annealed the outer edges using the sharpie method where the compund curve is. Just finished fitting them today. Wont know if it works any better than the standard ones till it goes back out to the airport in 2 or 3 weeks. Quietly confident they will be better, if not will just clip a scoop on it like others have done. Fingers crossed it'll work.

Steve
Sonex 892 87 hrs 3300 TD
Home for annual and mods

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[Mike53]

Very nice work Steve.How did you form the shape? ie what type of equipment do you have in your shop?

[142YX]

i agree. that is some really nice craftsmanship.

[sonex892]

Thanks. Dont you guys know things always look better in photos ;)

Special tools include.
Old version of autocad to plot things out.
LPG torch to anneal and soften the fold lines.
Wood form blocks 2 male 1 female
soft face hammer and clamps
Band saw to make male form blocks
Router to make female form blocks

Annealing is the main trick. Just dont do it for any structural parts. It will still be 6061, but not T6! If you havent already tried the sharpie method out, give it a go. Its quite simple, draw on a piece of 6061 aluminium stock with a sharpie. Heat it until the sharpie marks vanish. The metal can then be shaped. Stretched and shrunk.

Annealing is also good way to make the cable exit fairings. Was my first experiment a couple of years ago.

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[Andy Walker]

Thanks. Dont you guys know things always look better in photos ;)

Special tools include.
Old version of autocad to plot things out.
LPG torch to anneal and soften the fold lines.
Wood form blocks 2 male 1 female
soft face hammer and clamps
Band saw to make male form blocks
Router to make female form blocks

Annealing is the main trick. Just dont do it for any structural parts.

Could you post a detailed description of the process, with some photos? I'm definitely excited by hos those parts look!

[Mike53]

I too am interested in your modus operandi .
In the mean time I found this from Kent White on U-tube The only thing he doesn't mention is the annealing and I'm wondering why. :?: http://youtu.be/9K6c3_DMXjQ see also part 2
I attended one of his workshops at Oshkosh and watched him weld aluminum . Truly amazing.

[sonex892]

I'll gather a few photos of the process and post soon

Steve
Sonex 892

[sonex892]

Make male form blocks one main one "the thicker one" and another to hold it flat to back it up

Make female form block the bottom has a slope. I made a template and used a router. To set up the slope I clamped the template to a couple of wedges approx 7 degrees. It also needs to have a bend radius sanded into it

Cut out template avoid excess. Any is probably too much, also drill a hole and cut a relief slot. Go close the the second outer bend line with the slot but not too close this will need to be hidden from outside when installed

I marked out the fold lines with a sharpie to anneal. Gently heat heat until the sharpie lines vanish. Its annealed. I tried to avoid the middle so it hopfully retained its temper.

clamp between the male form blocks and use a mallet to bend the first bend the same as if you were forming a wing rib. Only go to about 45 degrees.

I used a screws each end stop movement in the main male formblock these were done in the excess left on the ends and later cut off

Unclamp the 2 form blocks. Dont undo the screws!

Clamp it down into the female form until it hits the bottom. Then hammer the flange down flat. Remove from forms then apart from a bit of trimming and cosmetic work its done.

The picture with 3 ducts lined up is 1st 2nd and 3rd attempts

Steve sonex 892

[Andy Walker]

Make male form blocks one main one "the thicker one" and another to hold it flat to back it up

Thanks for the explanation!

[Mike53]

Indeed thanks.Looks like the only tricky part is that slope but it will probably be clearer once you have it all in front of you.