GP ultimate Bipe 40

A Saito .91 weighs less and produces considerably more power than the OS .70. There really isn't that much difference in cost.

Ed Cregger

I had a Saito .91 in my GP Ultimate .40. 14x6 APC.

Lost it trying to land between two trees without being able to see it as it descended.

Can't blame the Saito.

It was tons of fun.

BUT Tom already said he wasn't gonna exceed the box recommendation, so you and I have just burned up a whole load of electrons just for the fun of it. :o)

Marty

I don't have that bipe but have two 40 size bipes and found them both to be tail heavy and the 70 OS was the way to go for me.

I have seen the light! The Saito 91 weighs less than the OS 70, (over 100 grams less!) has more power and is only about $20 more. Just might be the 4 stroker of choice for my bipe! In the past I have always stuck strictly to the manufactures recommended engine size. This always left me wanting more power. Maybe you guys have something here. :-) Soooo, if I do go with 4 stroke power a Saito 91 looks good to me. I truly want unlimited performance. Thanks, Tom.

One question about running this big bore Saito on the GP ultimate, is there clearance enough to run the 14" prop with the stock gear? If not what did you do? Tnx Tom

A .90 four stroke. This plane and engine go together sooooooooo well. I used a Magnum 4 stroke, no problems except a tree. Do not use a 2 stroke!

The Saito .91 is quite happy spinning a 12x9 or 13x8, whichever you have clearance to use.

Ed Cregger

In that case, I would suggest the Magnum .91, if he needs extra weight. He can also save a few bucks, if that is important.

Yes, I own a Magnum .91 four-stroke. I bought it for the Global Ultimate ARF I am assembling. It too needed the nose weight. Otherwise, I would have used a Saito .91. There is no doubt that the Saito is the more powerful engine of the two.

Has anyone seen the new OS Ultimate .70 four-stroke yet? I forget which web page showed it, but it looks as though OS is getting into the souped-up mid sized four-stroke market along with YS and their .63. A Google search should show it.

The OS .70 is a fine engine. I do not mean to slight it.

Ed Cregger

I flew the stock gear:

The guy who built the plane flew it on an OS .46. He didn't like the performance, so he traded it to me for some stuff. I put the Saito in and had 85 flights over 16 months before I stuffed it in the trees. I can still hear the sound it made. :o(

The fuselage is still flying, though in new colors and with Avistar wings.

I love the Ultimate design. I've got a bunch of pages on its history:

Let us know how your experiment turns out. :o)

Marty

I've got the OS 4 stroke it flies a treat. Beefed the u/cart mounting plate and replaced the dural with a carbon fibre undercarriage. The OS 72 provides ample power to go vertical and a little bit more

Yeah, the 72 makes it fly nice, but a 90 adds 'zip'.

I know you said OS, but Saito FA-72,... Hands down:-) There's a reason OS has come up with an analogue. Good power and keeps it light. If the OS unit does as well, go for it.

Heres one I think u better look at,The YS63,boy will that do the job,,mostly run it at half power and gun it when going up,,I mean up..Engine is light about 1.1lbs and turned ,20%nitro turning a 12-6 at 12,600.. I love it..

The OS .70 predates the Saito .72 by at least a decade or so.

Ed Cregger

instructions

How come none of you guys took the tree magnet out of the fuse before you flew?

My vote goes to the YS .63

JR

Hi Ed:

I realized that shortly after I posted. I wasn't familiar with the older 70, but was thinking of the new one. I didn't realize it the new one is pumped either. Anyway,...looks like the perfect engine for Tom's Ultimate. Powerful and still light, light,...light. A difference of two ounces in fuel tank size changes the way this plane flies noticeably. A 4stoke 70 with 8oz would be ideal. Can't loose either way ;-)

Cheers,

The OS is as solid as an anchor, a very reliable engine. All engines mentioned would fly the model well.

The pumped OS .70 hasn't made it to the States as yet. At least I haven't heard about it if it has.

Ed Cregger