GP ultimate bipe
 

My friend bought my an ultimate bipe kit for christmas,he thought it would look nice on floats. We don't have a field near by so we do all of our flying off of a near by lake. I have a GP super sportster on GP floats and it flys awesome. I posted this on the rc news group and the consensus was a forty size engine wouldn't be enough to fly it. Are these kits usually tail heavy requireing nose wieght to balance? Could I get away with a 60 size two stroke on it? I really don't want to deal with learning how to operate a four stoke motor. I was thinking of a piped Rossi 60 wieghing 21 ounces without exhaust system, any thoughts on this? Mike

GP ultimate bipe
 

I'm currently building a GP Ultimate (my first build). I plan on powering mine with an OS 46FX. From everything I've read, I gather that most people favor more power than this, but I'm not looking to hover or do any wild aerobatics. The 46 is rated as 1.62bhp, the Rossi looks like 2.5. I would think that'd be enough - that's comparable to an OS 120FS.

Also, I have read that these kits do build heavy. I expect to have to add weight to the nose.

I'll be interested to see other replies as well.

GP ultimate bipe
 

Mystic6-you are wasting time worrying about horsepower figures they dont mean much.
There is no way you can compare a 46 2 stroke to a 120 4 stroke.

GP ultimate bipe
 

Go 4-stroke. It's not hard to learn and you will appreciate the thrust a bigger diameter prop will give your ultimate.
A have one with a Saito .91.
Good luck,

GP ultimate bipe
 

guaraguao-I was thinking about putting a Saito 91 in mine.Did you have to move the batteries from the stock location to get it to balance?Did you have to add lead?What does yours weigh with the 91?

GP ultimate bipe
 

Yes, I have to put behind the last former in the wing saddle to balance. With a 5cell 1100 battery and tru-turn spinner, it goes for 6 pounds and 9 ounces. No lead required.

A great flier (best maneuver: inverted flat spin)

Good luck

Gp Ultimate and FX 46
 

Mystic. I built a GP Ultimate last summer, powered with an FX46. 11x5 APC prop.
Tons of power. Wont hover, at least not for me, but all else is great. Flies great. Watch the elevator throws. I set mine by the recommended amounts in the manual and almost lost it on first take off. Straight up, straight down and up just in time to bend the landing gear but saved the plane.
Did have a lot of engine problems that turned out to be overheating and subsequent leaning out. Ended up covering the front hole in the cowling opposite the cylinder. Much better after that. Go figure

GP ultimate bipe
 

front shot

GP ultimate bipe
 

Dang, the front shot doesn't work. I'd like to see it!!

trying again
 

lets try this again.

GP ultimate bipe
 

Humm,..... must be a problem with the front shot set up photo.

GP ultimate bipe
 

The thumbnail isnt working but click for full size, works for me

GP ultimate bipe
 

The plans call for 1degree upthrust.I have built lots of planes and have not come across any needing upthrust
Is the upthrust necessary?

up thrust
 

I built mine as per the instructions and it flies great, so if 1 degree up thrust is called for i'd put it in.
I have noticed a tendency for the plane to flare at very slow speed. It's very gentle and predictable but I have to put a little down elevator in when landing. I think this is a wing incedence problem and was making small changes to the top wing but ran out of summer before getting it nailed down for sure.