BsSmith

I'm trying to decide an engine for a Great Planes Gee Bee. The instructions reccomend a 1.20 4 stroke as the biggest engine for the plane. I am thinking of modifying a 31cc Ryobi weedwacker engine for it. I will also be putting foam between the ribs of the wing and horizontal stabilizer and covering it with silk and dope for the speed issue. Is the 31cc engine too big for this plane? The engine will probably need a larger fuel tank also, how will this effect the balance of the plane?

This is my first scale airplane, the most "advanced" thing I have flown so far is a Tower Voyager. I will learn how to fly this eventually...

FILE IFR

The GeeBee is a short coupled airplane (small moment). What is the weight difference of the 2 engines?

FILE IFR

I just checked the engine.... forget it.

If you were to modify it to make it work, torque alone will make take-offs a nightmare... with THAT plane.

Go with the factory recommendations for power options.

... just my opinion.

jay2000dakota

Im all for overpowering a plane but I think a 31 cc may be too much just due to the nature of the GeeBee. You might try a Saito fg 20 or saito 150. You will have to weigh the 31cc the compare it to the 120 or another motor of choice to test balance. If it was me I would run a Saito 125 possibly a 150, If I wanted to run a gasser it would be the FG 20. As I understand the Gee Bee can be tempermental on the ground as well as on landing and not forgiving to mistakes in the air. That being said I think 120 or 150 would make that Gee Bee fly like a bat out of hell, and as long as you learn the plane it should be a real show stopper. I was thinking about buying one myself :-)

BsSmith

Is there anything that I can do durung takeoffs to avoid the torque like taking off on a lower trottle? The verticle stabilizer is tiny, so there is barely anything I can do with the rudder. After take-offs, what difference will flying it be?

Weedwacker engines are CHEAP! That's why I keep on coming back to them.

Smacka

Agreed! An unintentional torque roll on take-off is a real beyotch!!

FILE IFR

A screen door on a submarine is cheaper than what the manufacturer recommends to be used too.

Your question for a high powered GeeBee take off overcoming the P-Factor?... Peg full right rudder and full left aileron then hope for the best! Just kidding[8D]

foodstick

There is a long gee bee thread on here somewhere with oodles of info..that being said I have the GP gee bee with a mcculloch 25cc in it . I only have one flight, and with the slight down and right thrust it took off and flew very simple...where I had my first problems is dealing with a slight crosswind landing, and wheel pants that were not trimmed enough to roll in grass, only on petrolmat.

So far I agree with the common concensus on this plane, takesoff easy, flies good, deadsticks bad, landing tricky.

Also I cut open the wing bays above the landing gear and added some structure, I had heard a few people say they were jamming the gear right through the wing, and believe me the gear blocks in the wing are minimal.

BsSmith

OK, then...

What about the Saito 125 or 150? Will one of those work or do I still have to go smaller?

Jester241

I dont think the 31 will have THAT much more power once you consider the extra weight. Alittle yeah,but probly not overkill. I am glad to see another "converter" like me! I have 2 or 3 ryobi/troy built 31cc's. And indeed it is hard for guys who've never got into converting engines to see the value of it. It took me one converted engine to say to myself...."why the **** did I pay $300+ dollars for those glow engines when I can spend less then $100?....for that savings,I can afford a bigger plane too and even a crash one or two and it wont break me considering the money I've saved" Well,almost....lol.

Now for the most important issue.....You say this is your FIRST scale model,and your most advanced plane is a voyager? Ouch....you might want to reconsider the gee bee. I've heard there very hard to fly and land. I would even be scared to fly one yet,lol. Maybe other could add some advice here.

BsSmith

I can fly the Gee Bee in realflight just fine, almost easy. Simulators may be far easier than real flying, but I know what to expect.

An engine that I could take the muffler off would be fun too. Any ideas on fuel pumps?

Rcpilot

My Feedback: (78)

A converted Ryobi weighs about 4.5lbs

A 120 4-stroke weighs less than 2lbs.

Don't use the Ryobi

BsSmith

Wow, I didn't know it was that heavy! And I thought weedwacker engines were small...

I guess the big question now is what engine will give the most power for the lowest weight?

FILE IFR

Is the GeeBee your first or second plane?... in other words, what is your flying experience?

Charlie P.

No. You don't.

If the Ryobi has a Walbro carb it already has an internal diaphram fuel pump. You're going to have to get the exhaust out of the cowl and the down-shooting muffler is the easiest way to do that.

The Gee Bees I have seen at fun flys seem to have a great tendency to nose over. More so than the WWI Camels, and that's considerable. You have to about stall it to flare it, and with those wings you're right at the point of a ground loop then.

It's no wonder the real ones killed so many pilots.

David Bathe

I wouldn't expect the Ryobi to be that much more than a 1.20.
Certainly not mine, and I have the factury conversion with the CH ignition.
Heavier up front certainly, but the factury converted one is lighter the the stock.
The good thing about the Ryobi is that it can swing a decent sized prop, 20" for example.
That isn't a bad thing considering the size of the cowl.

A scale Gee Bee isn't forgiving at all, the ones I've seen have been just horible, stroppy monsters .
One presumes GP have done some modifications for it's sports scale application.
My advice would be to built it as per the book.
Good look.

BsSmith

It is my third plane, I have been flying a trainer for 2 years and the voyager for a year and a half.

Yes, this plane wont be flying at NATS or anything. It still looks close enough though.

The plane was bought from an auction here, and right now it has a Ryobi Fa 100 in it. I swiched out the engine in realflight, and it is too small. I have about 2 months before it will even get warm enough outside to start any engine, so I will be doing some strengthening work and revoving all of the Monocote, because Monocote sucks. All of this work will add weight, so I need to size the engine appropriately.

FILE IFR

With a wing area that you cannot change, adding any unnecessary weight will require faster take-off and landing speeds.

With that said, operating off grass at higher speeds just adds aches and pains to the gear and frame.

Keep in mind the W/S is around 6', and length is 45+ inches and it has a very draggy fuse.

FILE IFR

B Smith, Here's an engine for your GeeBee, you'll never have to worry about breaking props. I got it from another thread here at RCU.

http://video.google.com/videoplay?do...50128014201935

BsSmith

Haha, yeah!

Now if only I could get one of those for a few hundred bucks...

j.duncker

My Feedback: (2)

By all means have a go at a Gee Bee but keep it as light as you can and stick with the recomended engine not the weed wacker conversion.

Fly it of tarmac not grass and keep the speed up. Your simulator experience will not really prepare you for the real thing. These are nasty little b's to take off and land. They are OK in the air.

Best of luck but you may well roll it into a ball on your first flight.

BsSmith

The field I fly off of is grass, so that is another problem.