Hey all, I have a problem, I am in the final stages of building an F4U from GS (Giant Scale) and have to make a decision on the engine. THEY suggest a 1.20 4C and I have been looking forward to using a 3cyl. 0.90 radial 4C from Saito. When I asked the pundits at the Toledo show they all said "not enough power"--maybe!! Can anyone give me an expert opinion whether I should even try this or forget it and purchase a 1.20 4C or higher??
PS: Do radials have any advantage over their corresponding single cyl. displacements??
I am new to all of this so forgive my ignorance.
jack

Jack
you didn't say how big the plane is...wing span? weight? A typical giant scale can run from 80 inch wing to 120 inch wing. If it's an 80 inch wing, I would think the 1.2 is plenty...don't know what you're referring to when you say 3cyl .9 4C from Saito...do you mean 3 cylinder (.90 per cylinder) for a 2.70 Saito 4 stroke? If so, then that engine will pull a much bigger airplane. My experience is that radials, while very cool, do not add much power to the single or twin cylinder set-ups...with a big Corsair, you can hide a big twin

If your talking about the GSP 75 inch Corsair, we have a couple here. One with a OS 1.08 and it puls very good. The other guy has a Saito 120 and also very good. Personally, I may trad off a Hangar 9 NIB for this plane and through a 180 in it but thats me.
The 1.08 pulls it good. Also consider some other 120ish two stroke.

I do not know the particulars on your Corsair (how much it weighs), but I do know that if "THEY" recommend a 1.20 4 stroke and you are contemplating the Saito 3 cyl .90, then you are looking at giving your Corsair about 1/2 the recommended power. As mentioned above, multi cylinder 4 strokes have less power, while having more weight, than comparable displacement single cyl. 4 strokes. In other words, your 3 cyl. .90 will have less power than the Saito .91, yet the .3 cyl. will weigh more. If you anticipate that the final aircraft weight will be under 9 lbs, then it just MAY work, but it kinda looks marginal.

Yes it is the 75inch Corsair form GS. The Saito is 3X0.30cu in. in a cylindrical configuration giving a total of 0.90cu. in. (4 stroke.).
I guess I'll do some thrust measurements. wing loading and finally the power to weight ratio before I consider trying to put it in the air.
Thanks for your help guys.
regards,
jack

I bought my husband the Saito FA170R3 and he put it in the small Yellow Aircraft Sukhoi. It has about the same size and weight specs as your Corsair. They recommend a 1.20 to 1.80 4c. This engine flew the plane, but my husband eventually took it out and put in an OS 1.60 2 stroke that he was much happier with. Also, if you are new to 4 strokes, the radial will give you nightmares. There are several threads on here about them, I believe. They are great when broke in, but they have an extended break in period and are very picky. It will require a great deal of time and patience to get it running just right. Plus you will probably require the added weight of an on-board glow driver. We ran ours without one, but we had to hand fabricate our system to start the motor. I believe these engines are better suited to an old bi-plane with a big round cowl. The .90 will definitely not fly this airplane. The 170 will, but depending on how you want it to fly, you may or may not be disappointed. I would recommend the Saito 150 at least and would probably opt for the Saito 180 myself.

Carol Cox
Gulf Coast Gulls

Consider an RCS 140 for you Corsair. Better on the pocketbook and will cost about as much as a saito 180 Pete

Thank you Carol and Rocketman, I appreciate your input. Just had a long discussion with my son who is our PILOT!!. We decided to do some power, size and price research along with our test experiments. I'll post an update on our results, good or bad.
regards,
jack