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Old Dec 14, 2005, 05:29 PM
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Joined Jun 2005
22 Posts
F-4 Phantom II for a first timer?

Greetings to you all!

I have done some research on my first pusher jet project. I have looked through many sets of plans, printed out a few to get a better idea of the measurments and the F-4 Phantom park jet somehow stood out, mainly becaouse of the large wing area.

Mine is to have a 76 cm (30 inches) WS and is to be built out of 5 mm thick depron with a carbon wing strut.

As this is my first pusher-jet build I am in a dilemma on whether my power setup is enough to power this thing.

I have the following: a 7 cell NiMh pack (one 1000mAh, one Pansan 1200mAh), a new Speed 400 6V motor and a speed-controller to go with those. Somehow I would prefer it to be direct-driven if possible. I plan to use two servos (10g) to control the model - one for both ailerons and one for elevators.

I chose F-4 becaouse of its relatively large wing (low wing loading) area but am worried about the large cross section causing too much drag for my setup. Therefore I have sized-down the fuselage cross-section by around 15% and made the whole lower fuse hollow to allow air from the intakes to move through unobstructed and exit at the rear. Will this do any good?

Will try to draw up some drawings to give you a better idea in the morning as it is getting real late here right now.

Any thoughts on my project and all recomendations are most welcome.
Aeroplan, Slovenija
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Old Dec 15, 2005, 08:40 AM
MJH
Registered User
Helsinki Vantaa, Finland
Joined Apr 2004
168 Posts
Having done one phantom myself, I would say Your setup is not up to the task. It'll propably fly, but the fun might not be there. Direct drive on speed 400 might also be a problem. I do not think the cross section is that big of a problem. Small prop on DD setup might be in the turbulent airflow, so in that case it could present some problems. Big prop and less rpm make these planes perform more jet like than great speed. Read throught jetset's f/a-18 thread (hehe) and You will get a lot good answers about setup and aerodynamics.
Airflow through the ducts will propably add more drag than just blocking them up front.
These are just my thoughts, but they do some backing up. I hope I didn't open a can of worms.
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Old Dec 15, 2005, 01:45 PM
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Joined Jun 2005
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Thanks for Your thoughts, MJH. It makes sense what you say about the small direct-driven propeller being in a a turbulent airflow behind the fuss and thus not being able to work its best. And I am also getting worried about the open ducts only causing more drag as the inner surfaces (foam) are not really smooth- it is a good thing I didn`t cut anything yet and just used some cardboard to draw up my plans.

Looks like I will make my way to the LHS and get myself a gear drive. I was thinking something like 2.33/1 with a 9/5 prop on my speed 400. Do you think this setup would allow me to fly some sort of a pusher jet? I mean, this being my first jet I am looking for something that would allow me to fly relaxed circles around the field with a nice airplane I have build myself. High speeds, high roll-rates and too steep climbs are not wanted/expectet, but I would like to see some acceptible low speed handling and maybe a loop here and there.

Again, all recomendations are most welcome. All my best,
A.
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Old Dec 16, 2005, 08:58 AM
MJH
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Helsinki Vantaa, Finland
Joined Apr 2004
168 Posts
Ok, here we go with the recomendation:
Put the speed 400 to zagi or something else fast.
Get a nice outrunner BL for Your phantom. Aurora 400T is what I like. Good, cheap? bl outrunner. 3s lipo and APC 8X6 prop. Not terribly fast but fast enough to give You a thrill when You want. Enough power(thrust) for fighter like performance (accleration and climb)...
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