Helijack

Hi,
I need information regarding BVM ceramic paint, fiberglass heat tolerance, and stainless double wall exhaust for a turbine. This is in a helicopter so I don't get the airflow through the fuselage you guys get.

So far, I have created my own dual exhaust system from 0.008" stainless steel. At 85K (my normal flight speed) my EGT is fine, well within normal limits at 460 C average. The exterior of the exhaust pipe at the locations that will touch the fuselage run from 220-270 F. (with a 47 degree ambient outside air temp) This will be right up against the fiberglass. About the only airflow inside the fuse is for the turbine to suck in, so lets assume that the ambient temp inside will be stagnant and climb up there as this is a super scale model.

My questions are:
1. At what temperature does fiberglass become effected by heat to the point of softening and damaging it?
2. How well does the BVM ceramic paint work?
3. Is there any info out there on the R-factor of the paint?

So long as the paint does not delaminate from the glass it will take up to 300 F.

So what have your experiences been. Thanks for your time
Jack

MAX EFFFORT

all i know is the more coats of bvm heat shield you brush on the more it protects. they recommend 3 coats..

Wayne22

My Feedback: (2)

I...I mean a friend...spilled some burning fuel...well it kinda blew out the tail pipe..on to the back of a balsa fuselage that was liberally coated with ceramic heat shield..it was a fair size fire, and was burning maybe 10 - 15 seconds before we got it out...... the heat shield merely turned brown in a few spots, but that was all..... highly recommended

Jetkopter

My Feedback: (1)

The heat shield will not stop the fiberglas from getting damaged, you need to have an air gap around your pipe. The heat shield will not stop the long term transfer of the heat radiating from your pipe. Your TOT will be way over 460 C once you start to pull a lot a pitch with a heavy scale machine. I make plywood rings that I bolt to the fuse to keep the pipe off the fiberglas. I have used this method in six different helis and it works well. The smoother your pipe bends are the cooler the turbine will run. You do not mention if your building a double wall pipe or single. Double is the way to go. You also need to move some air inside the fuse for the double wall pipe to work. What kind of fuse is this pipe going in?



Don

Helijack

No it is double wall, you might read again previous post with temp values. This will be an EC145 (similar to BK117)
I can fly with doors open and not loose points.
Thanks
Jack

I-NAV

My Feedback: (3)

Good stuff, but goes on like stucco. Anyone know a way to lay it on smooth? Also, what can you thin it with if the can dries out a bit?

Mike

Gazzer

Helijack,

I am sure there was an EC 135 going about in the UK that was turbine powered, it might help if someone knows who that was, to give some info about the exhaust systems they used. I will have a look through some of my UK magazines for you and see if I can find someone to contact/speak with.

Interesting subject for the states, what paint scheme do you intend using?

Gazzer

Rainman-ACRF

I think it was Dave Hollins - Feb 2003 "Model Helicopter World". I don't know if Dave is on here but I'm sure you'll find him on RunRyder. In fact here's a link that you might find appropriate:-

[link]http://www.runryder.com/helicopter/t55196p1/[/link]

Hope that helps,

Phil

Helijack

Ya Dave is over on RR.

I just remembered that on a different machine, (glow) that I used some silicone exhaust tube split as an insulator between the fuse and the pipe to resolve a similar issue and it worked fine, so I will go get some of that and use the paint some too.

I am doing the factory demo heli scheme from Germany. Can't figure out how to post a picture here. My avitar on ScaleRChelis.com is a pic of it.
Thanks.
Jack

JohnMac

Hi Mike,
How Ya doing? I thinned mine with a little water as the end of the tin was getting a bit gooey. Worked a treat but don't overdo it.
How is that F106 coming along? I flew my Eurosport last weekend (at long last).
All the best,

John.