Hello Peter Chinns Model Airplane New test of 1977 report of the similar OS10FSR had the C/L venturi at 6mm and the spray bar as 3.4mm with an effective choke area of 9 square mm
Regards Gerald
Thanks. That's perfect. I know what I need to know.
I wonder what the 'machinists' thought processes were to come up with that solution? The basic physics of a venturi requires a higher gas speed that gives a lower pressure at the just to induce fuel flow - the above venturi is completely backwards thinking - strange!
It's very pretty -- doesn't that justify all?
This came from a batch of airplanes that a friend of mine bought; there were other planes with similar venturi design, that benefited greatly by having normal venturi's bunged in there.
We're pretty sure that the original builder never actually flew the planes.
I also feel your trying to offer the .10 far too much prop with the 8".Even though the prop is cut down to 7", the blade area of a 8 compared to a 7 is quite substantial. A thinner Master Airscrew 7x4 should turn up pretty good. I'm thinking you should be in the high 17K range. I used the APC 6.3x4 quite a bit with this engine with good results.
I was going with what I have on hand. The only from-the-factory 7" prop I have is an old white nylon one -- I'm not going to run that. I need to order some props for it -- if the LHS has any nitro props they aren't going to be that small.