I have seen many of these prop jets that seem nice but not quite there. I have a proposal to all those prop jet makers out there that I think would be "neat" for lack of a better word.

Problem with prop jets are that the engines stick out for tractor types and the CG is hard to get right on pushers (plus, even when right, not a fun flying airplane)

My idea is a prop jet using the powertrain from a nitro boat. Whereas now, prop jets have their engines sticking out like Major Wart, the nitro boat powertrain would allow the engine to be located further back, hidden in the fuselage. The engine would sit at a 90 degree angle inside the area which would normally house the jets. The intakes and and exhaust should provide adequate cooling for the engine.

The size would have to be larger, say a 60 to allow enough room on either side of the drive shaft. The tank would straddle the drive shaft and be made of two thin and long tanks joined at the bottom to balance the fuel levels.

Of course, smaller ones where pull starts are available are also possible as well as pushers that want to move the cg further forward and hide the engine. in fact pushers may be easier since you don't have to worry too much about the drive shaft interference as much. In fact, pusher may be a better idea even.

Anyway, I think nothing can be prettier in the sky and still fly like a dream.

Why ARF? Because I want to buy it as one :-) I think someone can easily put this concept together and for those people that have always loved a prop jet but don't like the big engine sticking out and fake intakes/exhaust would snap it up.

Of course, I am available to test the first prototype :-)

Go to the site of Graupner. (www. graupner.de)
See at the news 2004. They have the "turbo raven" as prop jet. This plane is a real hummer. It's a pitty the price is also.

So do you mean the engine being in the fuselage somewhere and a shaft going up to the front of the plane with the prop on it ?

Ahh, I saaay COOLING mah boy!
Gonna overheat fo certain, you do it that way...

i actually had a buddy that had an F-18 pusher that had a shft that extended mabe 8in. It was a scratch built job. The engine set up in front of the horizontals. You couldn't run it on the ground long, but in the air overheating was not a problem. He lives about 100 miles from me and I haven't heard from him in a while. I'll drop him an email and try to get some more info tonight, heck he may even still have it, he had an elevator fail on the last flight, crashed but wasn't too bad.

Anybody see the P-39 Aircobra? Same idea, which would work if you find a shaft light enough and strong. Many of the nitro boats use speedometer cable which, when dries out from lack of oil, comes apart and siezes. Cooling may not be a problem if you have airducts to the engine like in a deducted fan. Maybe have a heatsink head.
Weight is my concern since there will be many more parts, such as a coupler head for the spinner and prop, the shaft and shaft tube, and then a cooling system such as added ductwork and possible heatsinks. But overall you may have a well balanced plane with more scale appearance.

I have finished my experimental propjet. It is a AMD SU-35 Superflanker glider converted to a nitro power plane. The engine is mounted upside down between the two "jets" with a speedometer cable drive train from boats. The muffler is in one jet while the fuel tank is in the other. The pusher prop is mounted way back where the tail naturally ends in a cone. It will be belt started and powered by a O.S.32SX. The only problem I see so far is the added weight and more importantly the ground clearance of the pusher prop. It allows for only very shallow take offs and landings. I am deathly afraid that the prop will hit the ground and stall the engine upon takeoff. Wish me luck! Will post pictures afterward... hope they aren't of me weeping!!!

P-39 would be natural candidate for setup like this. What about using a carbon fiber pushrod tube? Light, strong, if it can be balanced and made to run true would be perfect. You let back end be supported by engine, support front end with thrust bearing in firewall. Would have to mount fuel tank either right in front of or behind engine, behind would be better as plane would get nose heavy as it empties. Or if plane was big enough fuel tanks in wings...... but that's getting pretty complicated.

andy

I just gotta ask, why dont you use an engine designed for ducted fan aeroplanes and a ducted fan ? The last one I saw was awesome for a glo powered model.
Why try and re-invent the wheel ?

Don't know much about ducted fans but I've been told they're a pain. Belt or shaft starting, in-flight mixture controls, tuned pipes[:'(]. Friends have told me its 1 hour of prep. for 10 minutes of flying. I'd take a nice prop jet anyday.

You mean something like this.


CARS II

Smile....

CARS II

Yep...that's sweet. Where can I get that? Or can I just have that one.

So... I brought the plane out to the field and couldn't get it started :-( The boat starting belt was caught and wouldn't come free of the flywheel. I've rectified the problem but still not sure if it will start. The other problem was that the engine is completely new and hasnt been run in yet. Thus the compression plus added friction makes it really hard to turn over. Anyway, will try again. I would post pictures but the problem is that my internet access kicks me off every time I try to post something big :-(

As for that f-4, you've got to try to mid-mount the engine!!! That would be so so cool! And that whole plane is a looker. Mine is definitely no where as nice... looks more like a mule!

Keep you guys posted.

Dlcarterjr
This one I build a few years ago and can you believe it that it has about 6 flights only, about the wing my wife decided to do a stress test on it and it took a while before it gave up to her madness, after the wing gave up I toll her " Any way I didn't like the way the wing came out thank you now I have a good reason to build a new one.

Keep the flying.

CARS II

G/P F-4
Robat retracts
GMS 75
seven servos
fuel tank over the CG
fuel pump ( crank press. )
monocote, white, black, clear paints
Top flight marking pen
canopy dowel/pin release
nose gear service door
Robart wheels
12 # dry
and lots and lots of hard work.

That's what I was afraid of...GreatPlanes doesn't make that kit anymore[&o]. That sucks because it was a nice kit.

You can find one for sale now and then, they still have wing kits, some 8 to 10 months ago the wing kit sold for $100.00 now I will be getting one for $40.00, a 60% discount.
This F-4 wil be flying in the next 6 month.

CARS II

I'll keep my eye out for one on sale. I'd like to see some pix when you get yours up[8D].

[img][/img] I am also determined to find a fun sport prop jet. My latest is a T-2 Buckeye. I tried to post an image but could not. Check out my gallery. There are two photos there.

Is that a kit?

The T-2 is not a kit. I like straight wing jets, and a T-2 was not available so I drew my own.

My prop jet hasn't taken off yet :-( and I don't have any time left. I'm considering selling the project to a friend since I will be moving soon and this plane will not survive the move, I suspect. Anyway, getting the engine started using a flywheel from a boat was more difficult than anticipated. And when I tried to start it from the prop end, the shaft snapped (as expected ... back to the drawing board when I get moved!

This plane finally did take off but I did also have to sell after the first day of flying. Like my WM Ultimate 30... The best offers come right after you have a decent flight. This one had a taker even before the maiden! After dremelling away more of the plane to make room for the belt to eject after the engine started, I finally got her airborn... these are pics a few days before...