I can get a single wall from Wren, or a double wall from Jet Hangar. The double wall is more expensive, but will naturally run cooler. Anybody have experience with either one of these? It will be used in a JH F-86.

I use a Wren single wall pipe with a PST 600 (54 size engine) in a Trim Sabre. The fuz does get very warm by the time the model is ready to taxi out. After taxying back in from flight the fuz is cold due to the airflow through it, but does warm up again after the engine is shut down, due to residual heat in the pipe. You will need to apply heat shield such as ceramic blanket to any cables or pushrods that are in the aft fuz. I use a Wren pipe with a 44 in a JHH Skyhawk but for that I made an epoxyglass outer pipe coated in BVM heatshield paint and it seems to work well. The problem to watch out for is that the Wren 44 is very sensitive to the pipe, and it must have a divergent duct at the start. If the JHH twin wall pipe does not have the divergent duct you may have engine running problems.

H.

If Jet Hangar do a double walled pipe with a Wren design internal pipe then that's the way to go. I have a Wren pipe in a stainless outer attached to a BVM Bypass and there's a thrust gain of over a pound. Its very cool too.

Jason

In addition to the heat concern that Harry mentioned, if the pipe ever failed at the seam you will fry your fuse. A dual walled pipe offers another layer of protection. By the time you add the extra insulation to the rear fuse there is no weight savings for a single walled pipe.

Gary Mueller at Jet-Tech makes a dual walled version of the Wren pipe. I had him make a 54 size pipe for my Maverick, which I am converting to turbine. It is stainless steel with a titanium outer wall and appears to be well made. He can custom make it to any length.

http://www.angelfire.com/wi/jettech/

Joe

In my L39 and F16 i run the Wren single wall tailpipe with no other insulation.
Both work perfectly with no heat issues.

Paul

Hi Brian,

Going back to the old Sabre, hey. Is yours a Green or a Gold? I am using a double walled pipe, one of the 1st Wren type pipes Larry W made for his Sabres. More than 100 flights, occasional flames, never any heat damage to the fuse. I recommend it.

Larry Turner,
Flying Electrons, Milwaukee
Fond du Lac Aeromodelers

My Wren is a green head. I have had it for nearly 3 years and finally am getting around to using it. I think I will go with the double wall pipe.