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Need some advise Great Planes F-4 Phantom .61-.91 conversion

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Old 01-02-2018, 03:33 PM
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CalvaryCustoms
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Default Need some advise Great Planes F-4 Phantom .61-.91 conversion

Hello, I have a client that has an old Great Planes F-4 Phantom .61-.91 kit that wants build, but he wants it converted to electric or nitro ducted fan.

I have 2 main question... Would a .91 DF unit be equal to a .91 puller prop set up ? As far as EDF (if he decides to go electric), what system would you suggest ?

The specs on the kit say it will be 10 pounds and he wants retracts added to it. Any advise would be greatly appreciated.

Thanks,
Tim
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Old 01-02-2018, 03:36 PM
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Desertlakesflying
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Nitro ducted fan is going to be fun to try to find

Spend $1500 bucks and go this route. Going electric will cost 2/3 of that

https://pacificrcjets.com/collection.../kingtech-k45g
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Old 01-02-2018, 03:40 PM
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CalvaryCustoms
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Thanks Desert, That was my first thought as well, but he is trying to keep the cost down, so he wants edf or nitro df
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Old 01-02-2018, 03:55 PM
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CARS II
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I had one with a two strokes 90, it neede more, like a nelson engine with a pipe to really performe like a jet but just the engine was nearly $500.
I think it will be too heavy for an electric setup.

Better to go with the advice above.
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Old 01-02-2018, 04:00 PM
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Not to mention the kit really isn't engineered to handle that kind of conversion. You'd be a lot better off just scratching this old design from Pavel Bosak and selling off the Great Planes kit.

And if you do build the kit watch out for the ailerons, you can't install them as designed.

https://outerzone.co.uk/plan_details.asp?ID=5982
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Old 01-02-2018, 04:03 PM
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patrnflyr
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Or you could wait a few months and let him get one of the new foamy F-4’s that are rumored to be in research/development. Freewing has been hounded for a couple of years to put out an 80mm Twin one. of course, they’re silent but the outcry is deafening among the EDF fliers. Same setup as their highly successful A-10. The entire pkg would probably be much cheaper and fly much better than the conversion
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Old 01-02-2018, 04:14 PM
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CalvaryCustoms
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Thanks guys, I appreciate the advise. I'll talk to him and let him know
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Old 01-03-2018, 04:52 AM
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RCFlyerDan
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Originally Posted by MajorTomski View Post
Not to mention the kit really isn't engineered to handle that kind of conversion.
The kit is kind of a poor kit and design with the ABS parts that don't fit well. I built one 15 years ago, or there about. I sheeted and fiber glassed the jet. Came out heavy. I put mechanical retracts in it and the struts were too long for stable ground handling. They needed to be long for prop clearance. I had an OS 91 with a tuned pipe. There are DF stuff on E--Bay. Just saw a new Dynamax fan on this morning. You would be better off finding an old Yellow Aircraft DF and convert it to electric or one of the small turbines. I would not build it again, and wouldn't recommend spending the time or money on it to anyone.
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Old 01-03-2018, 10:24 AM
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Does the GP F-4 even have the internal volume necessary to accommodate an inlet, engine, tanks and exhaust? I seriously doubt it.
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Old 01-03-2018, 12:27 PM
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ID:	2249811I had to dig in my old pictures of my build. This was back in 2004. The ducts would go along the outside of the center fuse, down the exterior bulkhead and exit out the back. Now that I am looking at it, I could see where it could be done and put a 45 in it. Things would be tight and it is a heavy plane.
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Old 01-03-2018, 12:33 PM
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Was having picture upload issues...........

CavaryC: I reread your intentions. I have a feeling this is more for nostalgia and the "what if". Another buddy of mine built one the same time that I did and kind of a little competition. On the two ducts on the sides of the outer center of the fuse, he sheeted the interior bulkhead wholes making a true duct, thinking it would go faster. We never knew, because he never flew it. It was tedious and added a lot more weight. If you do a single center fan and maybe make cheater holes on the interior wall would be another option. The biggest issue will be there isn't much room in the wing saddle area for the fan. Unless some how it was behind the wing.
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Last edited by RCFlyerDan; 01-03-2018 at 02:12 PM. Reason: More thoughts
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Old 01-03-2018, 11:17 PM
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Nice work on the build. But echoing other comments, converting this to EDF(DF is not going to work here, you need as much power as you can get for F4 ) would be very difficult even if you are experienced in efficient DF systems. Intake area here is probably sufficient for a 100mm+ fan but the outlet area.. bifurcated you'll loose some efficiency and hard to make well.. probably better to bash a single, more efficient outlet. Otherwise twin smaller EDF units.. now it gets pretty complicated and expensive with 2 of everything. If he still wants it built I'd go with a hot prop setup. Now a DF engine with a cut down prop might work but again special segment of the hobby.. a BVM 91 on a prop can throw a blade at 20k rpm.

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Old 01-12-2018, 04:56 AM
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RCFlyerDan
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Calvery:

This just came on the market this morning, if you are interested:

F-4 Phantom Prop Jet WING KIT ONLY (ID: 1127450)
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Old 01-12-2018, 12:04 PM
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Terry Holston
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William Donner from the Detroit Area built one back in the day with a Ram 750 in it.... Believe it or not. Painted up like an American flag if I remember right.
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