Hi....

I've got an Ultimate all framed and ready for an engine. Right now I have a couple of choices immediately available, but am not sure that I want to use either.... (a .108 2 stroke and a Saito .120).

Can anyone tell me what has to use on this airplane for a half-throttle hover?

Your comments are appreciated!

A lot of people are putting 1.20 four strokes in their GB Ultimates and love the resullts. However, I do think that the structure will need a little strengthening with that size engine. I think the Higley Bipe book has a whole chapter about strengthening this model in it... I have also been told that tail braces are a good idea with that size engine...

So I vote for the Saito...

I'm putting a Saito 120 in mine right now. My opinion is that the 120 size four stroke is a tight fit for this airplane. My issues were:
Overall length of engine
Exhaust routing
Balance
Throttle linkage
Stretching cowling over engine for final assembly
Fitting big fuel tank
Strengthening firewall mounting structure
Did I say "balance"?

I have everything under control now. It's a clean installation. It just took a little engineering and patience.

Good luck.

Thunder Tigre 1.20...
- 2 rear mounted elevator half servos
- rearward mounted (under canopy) rudder servo
- rearward (just forward of canopy) battery
... gives me a slightly rearward CG for great performance

carbon fibre re-inforcing, especially at the lower wing mount.

weak spot now is the elevator "couterbalance" (forget the proper term; section ahead of hinge line), keeps breaking near the glue joint.

I'd use the 1.20 4-stroke. I built 3 Goldberg Ultimates in the last 10 years - all were powered with Enya R1.20GP 4-stroke engines with a Don Harris pitts smoke muffler. No firewall mods. I used the stock 2 piece mounts. Engine mounted as far back as possible - carb is 1/16 or so from the firewall. I have to remove the valve cover when installing/removing cowling. I mounted a 1200 mah battery in the tail (saved the cutouts for lower aft fuse and made a door). Good luck. You'll love the Ultimate!

For a half throttle hover a 4 stroke 120 wont be enough. My ultimate hovered with an OS 120fs at nearly full throttle, sure it was do-able but the safety just wasn't there. The airframe is perfectly strong enough stock for the 120 and a YS 120 was what the designer Dave Patrick used in his "wring it out" series of tapes. The only mod I would do is put in the two wing servos. Currently I fly my stock ultimate with a saito 150 which I feel is close to the perfect match for this plane, it hovers just about half but the pull-out is much better and its general flight characteristics are excellent. My votes for the saito 150, my airframes had about 8 years of flight with big four strokes and is still holding together.

What would be a good size 2 cycle?? I have a mag 1.08 in a GP 300 .60 size waiting for its first flights in the spring and am looking to build an CG Ultimate over the winter. Wife actually is asking me to.. (she likes the looks of the plane) I am looking at possibly another 1.08 and also want about 1/2 throttle hover ability. I don't think a .91 is enough and maybe a 1.20 is too much in a 2 banger. Any imput would be a great help
Jeff