how much heat is to much for the fuse ,i have a bvm t-33 with an open install the p-80 is set about 1 inch from the bell mouth of the pipe which is a bvm or tams not sure double wall starts about 6 inches after the bell mouth on ground run the fuse gets to about 130 to 140 degrees after about 3-4 minutes of run i think the fuse will cool down in flight just wondering if this it to much heat for repeated runs any help thanks

When it catches on fire, it's too hot.

Any pictures of your installation??

Actually, I have a lot of experiance here. This is a post from another thread:

Most of the fuses I have dealt with start to get soft around 150 and up.

As a rule of thumb, anything above 120 degrees, you can not keep your hands on it, you can touch it, but you'll have to pull away, even though it won't burn you.

So sometimes even though you can't keep your hands on the fuse, if it's at say 140, you are still good.

Mileage may vary, and ceramic blankets, work well for this type of issue, mounted to the fuse. I've had no real good luck wrapping the pipe, but some have.

i could take some pictures and post next day or so

i should have icluded the top 1/3rd of the fuse has the blanket [bvm] and the rest of the fuse from the hatch back has 2 layers of the heat paint [bvm] and the top dose run a little cooler than the sides and bottom was trying to avoid lining the whole back half with the heat blanket as cg is right on the mark now

Hi,

I'd also be curious about the rest of the install. Did you get a chance to take pics yet? I'm wondering how far forward from the tailcone (of the airplane) is your pipe? I've seen installations where the builder (usually a beginner) is worried about hot exhaust burning the fiberglass tailcone, so he puts the aft-end of the pipe too far aft in the fuse. With a good healthy inset of the pipe, the fast-moving exhaust can grab some air on the way out and get a draft doing through the fuse.

Still, I think a double-layer (shiny-side-out and crumpled so there are lots of pockets of air between them) of regular ol' aluminum foil is a far better heat insulation for your fuselage than all the ceramic blanket and ceramic paint on earth....

Would have to agree with Shaun on this one. Nothing is a better insulator than a compartmentalised air space, and the aluminium foil option is very light, and will reflect and dissipate radiant heat well. The problem with ceramic blanket is that it might be slow to heat up but once it is hot it will also retain heat for longer than Shaun's option.

Just one other thing.....the softening point of epoxy resin is around 100 degrees C depending on the type of resin of course. I would not want my fuselage getting that hot as permanent deformation can result. If I can feel the fuse is warm I would fix the problem rather than tempt fate.

Hope that helps.

yes the end of the pipe is out side of the tail just a bit maybe a 1/8 inch and the opening around the pipe is very tight about a 1/4 inch, so how far would you say to side the pipe back inside the tail and in doing so should i keep the gap between the pipe and the turbine at around an inch ,moving the pipe in makes alot of sense to create a suction from the exhaust i think it may have been inside about a half inch or so and i slid it back some as to like you said avoid heat inside the tail i will check the f-5 i have and see how far the pipe is in it as it is an open install also and i don't have a heat problem with it if i remeber right it is not inside the tail cone very far at all thanks for the help

update on my heat issue i have moved the pipe inside the tail about a 1/2 inch now and ran the engine today and the heat has been reduce to around 75- 80 degrees almost half what it was,thanks for the responses and the solutions for my problem one more very important building tip to remember

Hey,

Awesome!