Any body done it? I'm putting together an AMD Hawk clone w/a Jetjoe 1400, and want to build my own tailpipe. If you've done it, what did you use?

I used .010" thick stainless for the inner pipe. The toughest part was bending up the 3/8" wide corrugated strips between the inner and outer pipes. The other problem is the welding; fortunately, I had access to a resistive spot welder at work or it wouldn't have been possible to make one economically. I've made outer pipes from .010" thick stainless and aluminum. The aluminum is easy as you can tape the seam with metallic tape.

I've made several using stainless shim stock and nuts & bolts.

mcmaster.com part #9506K14 or 9506K16

Figure out the circumference and add a 1/2" lip. Drill 3/32" holes every 1 inch and bolt together with 1/8" 2-56 stainless flathead bolts with washer and nut (bolt head inside the pipe for less drag). Make the outer pipe about 1/4" larger in diameter all the way around. Use 1/2" 2-56 bolts & nuts at 4 points for standoffs at each end. Be sure to offset the inner pipe around an inch shorter than the outer at the exhaust end. The outer can be a few inches shorter than the inner at the inlet end.

Make sure you use a bellmouth at the inlet or a bolt on few wraps of stock at the inlet so the pipe will not collapse. If you don't, it will.

Note, most pipes taper down in diameter at the exhaust. You can do that or make it straight. Done it both ways.

If you use the same thickness shim stock for inner & outer, you can make a pipe up to around 28"-30" with one roll for engines up to about a P-80 at a cost of maybe less than $40 and 1/2 to 1 days work.

I've done several hundred flights on these homemade pipes and they will hold up.

You guys rock! I'm a certified TIG welder by trade and welded one up from .010" 301 Stainless yesterday= but it got stuck on the 3 1/4" stock I wrapped it around to hold it's shape while I welded it. I scrapped that one, but I'll do another on Monday!

I built a few with a homemade spot welder. Here are a couple of examples for a friend's turboprop and a long one for a scratchbuilt project.
I used .007 stainless sheet. It's cheap and easy to do. Best of luck.
Paul

i use a phone to make mine, call 1-800 TamJets

I used the .004 & .006 combo for my pipes and thought they were a little heavy. You guys ok with .010 for weight??

I haven't measured one of Tam's lately, but I thought his were .003" or so.

Tams used to be .006 and as far as I know has gone to .007. I think .007 is ok, but if I was going to make another, I'd go with .008 or 9. I am really liking the Eurofighter Straight pipe from Composite Arf, I have wetstarted it, flamed it beyond recognition, run a jet through a barbwire fence, and still three years later, that pipe is holding up really really well in three different airplanes. I don't know how thick it is, but it is bulletproof.

Went and measured a couple pipes I had laying around and most seemed to be .008".

Ok the question is ,now,how to build your own spot welder? parts list and links please

The 3-4 pipes I've made use .008" stl for the inner pipe, and .006" stl for the outer. The outer is thinner since it won't see as much heat (if things go as planned), and these things can add ounces. I'm using bypasses, so I skip the bellmouth.

http://www.5bears.com/welder.htm

Also http://www.gtba.co.uk/

there is technical article in the old newsletters section.

Paul

The normal stainless shim stock was just too small on the width for what I wanted, so I bought a sheet of .007 stainless, 24" x 10 feet long.

I don't think it's really worth all the hassel building a spotwelder from scratch, unless you just like puttering with this sort of thing, so I bought one.

On the old Isobars I would use .008" stainless for the inner thrust tube and hold it together with 6-32 bolts at the seam (be sure to do it such that the helical exhaust blow over the seam, NOT into it!). I would use some thin aluminum duct work that I got at a local hardware store for the outer tube. I would cut a strip of the .008" stainless about .5" wide and just bend it by hand to make the Z-like thingy to offset the inner from the outer. One in the front and one in the back. Make it tight and friction is plenty to hold it in place. Its easy and never failed in any way. Be sure to use aluminum for the outer tube to save weight, it does not get very hot so Al is just fine.