I know that there is a lot of great knowledge/experience on this forum. I need help/suggestions for converting my CJM F-4 Phantom from twin d/f to turbine power. The plane is built and was almost ready to fly with 2x91 d/f engines. The previous owner sold the engines and I bought the airframe seperately. I am leaning towards a turbine in the 25-27# class with a Tam bifurcating tailpipe. I have talked to CJM and they have a tailcone upgrade from the ABS ones on the d/f version. However since this is the older, one piece wing, the brackets for the Elevators are made of nylon/plastic. I don't think they will hold up to the stresses that a turbine will put on the control surfaces. I have Hitec high output digital servos for all the control surfaces.

My questons are:
1) Which turbine will give me the best performance and reliability? (I know this question could open a whole can of worms)
2) Any suggestions for the torque brackets on the Elevators? The old ones look like the mounting bracket off of a .60 size nose wheel.
3) The full-size F-4 had its engine mounted with about 10 degrees of down thrust. Is that necessary for the model?
4) I know that I have to change the formers to suit the tailpipe and turbine. Any suggestions with the ease of retrofitting and maintenace in mind?
5) I have seen several threads on the behavior of the BVM F-4. Does anyone have any feed back/experience with the CJM F-4?
6) One of the threads I read pertained to the AoA while on the ground. I have noticed from all the pics of the BVM F-4 that the nose wheel strut is longer than the CJM. The CJM sits with a neutral or slightly negative AoA. Do I need to adjust this or will the plane rotate gently? The F-4 mains are well back of the CG.

Thanks in advance for your feed back.

Cary

I have good contacts to the "phantomstaffel" of germany. Their F-4s are about your size, so i can get you their experiences.
A german air force F-4 squadron is also based near my home, and this is where i spent my time during the military...

To your questions:

3.) The engine is mounted with 3,5 deg down attitude in relation to the fuselage reference line. This is unneccessary in the models, however a slight down-thrust comes in automatically because of the low nozzle position.

6.) the F-4s i've seen all had negative AOA and rotated smooth. Do it up according to pics and scale documentation just like the real thing and you'll be fine

Cary

I solved the elevator torque bracket problem by using two pieces of aluminum angle stock and press fitting bearings into each angle to form the torque rod support. A pair of bearing brackets are used for each elevator. The bearings are secured in the aluminum with JB Weld.

Send me a PM and I will e-mail a photo. I am not able to load photos , RCU keeps telling me they "won't load to disk".

Roy

Thanks Guys,

Re: the thust issue. I was concerned with melting my elevators. I will go with what I have as far as the nose gear is concerned. If the plane 'jumps' into the air too much, I will deal with it then.

Roy, I sent you a PM re: pictures of the bracket you made up.

Thanks again,

We have the conformal fuel tanks for the turbine F-4. I think we can make the nose gear oleo extend like we do on the F-18E and our F-22. You might contact us off line and lets see what we can do to help you out.

Do not use spoilers. Unless they are hydraulic powered, they will "float". Use ailerons like I think BVM does.

Bruce Sanders
Century Jet Models

For what its worth, rotation on the f-4 will not be smooth with a negative attitude on the nose strut. The strut either needs to have a positive attitude or you need a scale type strut that extends to a positive attitude on take off. this " scale" strut can be mixed with the throttle for optimal operation. For example you could mix it so @ half throttle the strut extends about an inch and a quarter. BV can tell you where to get this item...Ray Blair

So the front of the turbine would at positive attitude relative to the thrust line of the model?
Creating the desirable negative thrust angle for the turbine or fan unit.

Seems that post is incomplete...but from what i read i see the question which way the engine is tilted. The nozzles are slightly pointed towards the ground, so the front of the engine would be slightly higher than the noisy end

Miniflyer,

Could you PM me with regards to the "Phantomstaffel" info?