Dennis: I had two Surpass 40s and the only gaskets they had were cylinder and backplate.

Bob Z.

My two Surpass 40s were very early in the production.
I was told by the supplier that the gasket was eliminated.
No matter - as a matter of course, I eliminate all paper/fiber gaskets in all my engines.

Bob Z.

OK after scrambling around the shop I had some 2.5mm for the carb and cam cap. Then found the 3mm for the backplate. One thing that is tricky and a little strange is there is one bolt that adds support to the intake manifold to the case that is a slotted bolt not socket head. I think it is a shoulder type that is a little larger on the shank that goes through the case into the manifold. All good but I think it will get a bit more compressions after it runs a bit.

Best,    DennisT

Russ,
Sounds great. What fuel are you using? When I last had this engine in a plane it was my YAK YAK biplane (two Sterling Yak 9 wings, lots of wing area. The setup was 10%N, prop 11x5 BBYO, worked well. Might go with a 6 pitch to allow little lower rpm.

Best,    DennisT

Running them at low rpm with a high-pitch prop is the way to go.

   That's something to try, Igor Panchenko was the first guy to explore that. But I am curious how you came to that conclusion, since the only real success with 4-strokes has been with ~4"or so of pitch and 10,000 rpm, going all the way back to the mid 80's and Ted Fancher.

     Brett

   That's something to try, Igor Panchenko was the first guy to explore that. But I am curious how you came to that conclusion, since the only real success with 4-strokes has been with ~4"or so of pitch and 10,000 rpm, going all the way back to the mid 80's and Ted Fancher.

     Brett

Hi Brett, I came to that conclusion several different ways. Some RC guys at the field fly 3D style big pattern planes, hovering the plane vertically like a helicopter. They are using big four stroke motors running what sounds like maybe 3000 rpm at that moment, and big 21 x 12 props. It's interesting to see the low end power of a four stroke to hover the big heavy plane. I was thinking about that combination for stunt. Then I asked someone locally who flies a Shark, what prop he's using and he said 12.4 x 5.5 three blade. He didn't know what rpm his electric motor was turning, but to fly with a 5.5 pitch it must be around 8500 rpm. I also saw someone flying an F2B plane with the Discovery Retro 68 and he's using 13.8 x 6, again down near 8000 rpm. I really like the smooth flying of this engine speed on both planes. Then I was reading a bunch of articles here on stunthanger and I think I saw some people writing about using 6, 7, or even 8 pitch props on a four stroke, which means they have to be running down between 7000 - 7500 rpm. Then I saw some tourque curves for some four strokes, and yes the tourque curve is strongest between 7000 - 9000 rpm, and it goes down as the rpm goes above that. And finally I recall the stories you shared on the other thread about the Saito 82 causing weird plane vibration problems in some people's planes. I know they were running the four stroke with a high rpm with a 4" pitch. So with all that in mind, the evidence keeps pointing me to low rpm and high pitch is the way to go.

There was also some discussion about the benefit of a four stroke having 1/2 the "pulses" of ignition that a two stroke has, and somehow that is supposed to be an advantage from some gyroscopic reasons that I don't fully understand. I am curious to see if I feel any difference between the Saito 62 and the Discovery Retro 68 flying the same rpm and maybe even the same prop. If this is true about the "pulses" or whatever they are called, then there would be even fewer of them at 8k rpm than at 10k rpm.

To test all of this, I have a Saito 62, Saito 82, OS FS-40 Surpass (not for F2B) and one other four stroke for F2B that I won't mention at this time. I have an Impact plane as a flying test bed. It weighs 75 ounces so it will be a great test for the engine's pulling power. The 62 is my first test. I need to get it broken in and installed in the plane and start working with it. I've been slow to get it in the air for many reasons. I figure in late January I should have the time to start working again on this project. I plan to write a post as an update on my adventures with all of it. I'm learning a lot and having fun with it so far. I can't wait to get it in the air where the real testing begins.

Russell

Russell,
I like the low rpm/higher pitch with the 4strokes. There was some discussion about a progressive pitch that being low at the hub, high through the middle and slightly lower at the last 15% at the tips. Some have done just high out to the last 15 -20% then lowered the pitch 5 - 7%. I like wide blades but have also tried long skinny one too. You have to match the ship.

Best,   DennisT