Hi Guys,

I scratch built a big 12 foot long T-38 and it fly's pretty nice with EDF power but is a little under powered. I was considering converting it to turbine. The plane is built entirely out of foam. AUW is 41 pounds

The plan would be to have a custom double wall bifurcated pipe made but my main concern would be protecting the internal foam structures from heat and was wondering if anyone knew what the average internal fuselage temperature got to on inside the fuselage of a turbine jet in the vicinity of the turbine.

Thanks in advance

Andy

Here are a few pics of the plane.

Its not the turbine are you need to worry about, its the area around the pipe. If you dont have good airflow around the outside of the pipe you can get some pretty high radiant heat temps. The warmest outside fuselage temp I ever got was on a BVM t33 at the end of the pipe. It was pretty tight there and it got to about 142 F. I would probably get some thermal insulation and line the foam around the pipe and turbine exhaust cone. Keep as much clearance between the pipe and foam as possible. Remember that much less heat transfer takes place >1/8th inch from the source. Scotty

You might consider adding a thin wall lining around the turbine pipe, say gutter pipe, and driving air out between them with a small EDF!

Sweet plane! Very nice build.

Use the search function to look at my thread entitled "Fabricating a Thermal Blanket".

Harley is right with the idea of a thermal blanket. The best kind would be thick header wrap ceramic weave with a metallic liner. These are the same type as we use on turbine helis where there is a lot of heat build up from bends in the pipe, and a lot of radiant heat near soft glass and plastic. In a heli we also do not have adequate airflow that you get from a dual wall pipe on a jet with air flowing over/through it. Wrapping the actual pipe in the header wrap helps keep most of the heat on the inside of the pipe ...


http://www.amazon.com/HeatShield-721.../dp/B0055BXW3Q

http://www.vario-helicopter.biz/us1/...ducts_id=37041

http://www.jegs.com/p/JEGS-Performan...18561/10002/-1


I would wrap a dual wall pipe in this, the then leave enough of a gap around to allow additional adequate airflow. While the turbine is running, the venturi suction will be pulling ait through the fuse .. Because of this i would definitely use a blower to keep things cool during start, and after shut down through the cool down cycle ..



~V~

Just a curious thought. Is the foam that was used safe against fuel spills. I know a lot of foams will melt from fuels, would have to be very careful.

Ive done small foamies with P20's and I tend to glass the foam with lightweight wing skinning material and high viscosity epoxy , then go with the heat blanket and some times paint the blanket with BVM heat paint ... I was really surprised the outside of the foamie was barely warm ... the most important part is the airflow though ...

Scott.

Andy, That is beautiful Talon you made, Wow!!!!

What is ur current power set up, how much thrust ur fan is producing, I will start working on my Arrow soon so trying to gather info from guys who have big edf jets...