I want/need extentions for my Twinkie. Knowing that the common ones are not so common, has any one ever thought of an owner produced part? How about as a "minor alteration"? They have no connection to any other system, can't impead any other system, attach with only a band clamp (super easy) and easy to make. Seems to meet the "minor alteration" criteria. Thoughts anyone?

The logic works for me....
-Zach

I would suggest that you use more than just a band clamp... Gulf Coast used a "button" on the clamp that required drilling a hole in the stock pipe. I've seen a set of extensions on the fastest twin out there (sorry Jeff) that uses a retaining link.

A lot of vibration on those stacks and with heat and cool down,... IMHO you need some form of a mechanical retaining mechanism and not just a friction clamp for attachment and retention.

I agree with the minor alteration... altho most of the airplane records that I've pirated have a 337 on file for the extentions.
Jim

Do we have a website address for Gulf Coast? thx

I was thinking of a band with some kind of a button or pin to help retain them. Shouldn't be too difficult to come up with.

Without a button of some sort you will lose the extension in short time due to the heat/differential expansions and vibration.
A hardened rivet welded to the extension with a corresponding hole drilled in the original stack to receive the rivet with a proper band clamp would closely approximate the Gulf Coast stack and mine have been trouble free for years. They sure keep a lot of heat and exhaust stains off the bottom of the wings, too.
If unable to find the real Gulf Coast Stacks, a detailed drawing with metal specifications along the lines of the Gulf Coast design would probably be a fairly easy 337 to run through.
Steen

As a "minor alteration" I don't think a 337 would be required and as an owner designed part no PMA authority is needed either. This should be a very easy project as soon as I get time.

Careful......exhaust systems are considered very "HEAVY DUTY"by the FAA folks. Additional weight/mass at the end of exhaust stacks that crack upstream and create hot spots in dangerous
places are not to be taken lightly.
Just my opinion, of course.
Steen

A reasonable retort for the Feds would be to refer to the previously STC'd units no longer available.

To believe there is a "reasonable retort to the Feds" could also be dangerous, IMHO.
Steen