Bob...

im getting ready to build a goldberg ultimate biplane kit and want to put a 4 stroke in it. the engine specs for the four strokes run from .91 to a 1.20. id like to get the 1.20 because it will fit nicely in a future sukhoi. will a 1.20 just be to much engine and weight (approx. 10 oz.) on the 54" bipe? i dont mind extra engine but i feel it might be a little to big. i hope you can prove me wrong because again, id like to get the 1.20. maybe you know someone who has an ultimate 54", or maybe you have one and can help me out. thanks.

p.s. i dont want the plane to be docile, of course.

Doug D.

Bob !
A O.S. 1.20 will be fine if you keep the model wieght in the recommended spec's.
I'd suggest a Saito 1.50 or a YS 1.60 if you want even better performance.
A friend of mine had one with a O.S. 90 two stroke which gave it very good performance.

MinnFlyer

My Feedback: (4)

A 120 will be excellent on it.

My dad had one with an OS 160 twin, and it was tricky to fly due to the excessive torque.

I also had a friend who had a surpass 91 in in it, and he could Knife Edge climb immediately after takeoff

So a 9 wouldn't be too small, and a 120 won't be too big

Personally, I have a YS 110 that is earmarked for a CGM Ultimate some day

BillS

I had a ST 90 and an OS 91 Surpass on mine and it seemed to fly about the same with either engine.

TLH101

My Feedback: (90)

! had a Webra Speed 1.20 2 stroke in mine, the 1.20 4 stroke will be just fine.