I received a PM with some questions that I felt should go here as well, also, they are some questions that I am not 100% educated on.



quote:
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hi Jeremy
I am subscribed to your thread on the subject.
I appreciate you trying to help everybody.
I am working on my first turbine jet & want to know:
1- is the distance between the turbine & ss pipe crirtical & how
to determine that distance.
2- where to place the turbine components inside the jet to avoid
interference.
3- the best way to do a range check
4- dealing with residual heat at the tail section on the jet.
5- hot to avoid wet or hot starts.

I probably will have more questions as I make progress

thanks
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1. From what I have been told, the general rule of thumb for an engine into a SS pipe should be approximately 3/16" from the end of the turbine tail pipe to the entrance of the bell mouth on the pipe. (see the picture below)

2. The big trick is to place your fuel pump as far as possible from your receiver and ECU. I try to stay at least 5" away if possible. As for the antenna, I like whip antenna's, but if you don't want to do that, a good trick is to put a piece of outer nyrod down the leading edge of the wing when you build it, and then put your antenna in the inner nyrod portion, when you plug your wing in slide the inner nyrod into the outer sleeve. I would never run my antenna down the inside of the fuse in a turbine bird with a SS pipe, or down the tail end of a ducted fan if the back end was composed of alot of carbon fiber.

3. When I range check my jet, I first do a range check with antenna down and walk 100 paces from the model. Then do it again with the engine running (be sure to have a helper holding the jet when doing this one)

4. Residual heat really isn't as big an issue as you might think. The SS pipe should be double walled with a third tube called the ejector tube. There is a 3/16" gap between all the tubes. The tubes are separated with a crimped piece of SS at both ends. If you have a concern with residual heat (as I did on my exocet) use a piece of BVM's heat shield ceramic blanket in the back of your jet. When the jet is flying the cooling is very good, it is if you are doing extended run ups on the ground where no air is moving around the outside of the pipe that it gets hot.

5. To avoid wet starts I have always shut down my engine by turning off the manual fuel valve, that way it burns out all the fuel as the pump can't draw more in when the engine actually stops running. Should I have a flame out I just run some air back through my engine before the next start ( I still run air start engines and I prefer them in all honesty) I have only had one wet start and it was my fault. I had the receiver battery to low (just doing a run in the yard, no intent to fly) and I had the fuel ramp start just as the receiver battery went below it's limit to allow a start. The next start I never even thought about the raw fuel in there but it was just a small puff of flame and it was fine.



Of course there are many here more experienced than I am, hopefully they will add their 2 cents

Jeremy