ORIGINAL: NM2k
No, they do not. I'm certainly not expert on what they do and do not permit, but the customary tuned pipes that we are used to and flying with the retractable landing gear tucked up into their wheel wells are not permitted. I don't want to steal this thread talking about that stuff.
It's funny, but when trying to match the performance of an engine like the HB .61 PDP with a smaller/albeit higher horsepower smaller engine, it just never works out the way that some folks would like. The larger, older engine usually stomps the dickens out of the smaller engine with more horsepower. It's probably because the smaller engine has to turn a smaller prop faster in order to produce the lauted superior HP figure. This is something that I intend to experiment with in the coming months. I've flown an old original Kaos (60) size with smaller, but more powerful, engines and then compared the performance to the same model with K&B & HB .61 PDP engines. There is just something about the raw power of the larger displacement engines that the smaller, but more powerful engines, can't quite equal. I'm sure someone will have flown a sleeker old patternship with a smaller engine and liked it. But it just hasn't happened to me as yet.
Ed Cregger
Good point. I too found this to be the case when I went to electric powered ships. The power curve (slope) is actually reversed relative to that of an IC engine. This means that the bigger the prop the more power an electric motor produces (well until the magic smoke comes out [:@] ) compound this with a deep gear box and an electric motor with 1/2 the power often can compete with an IC engine that is rated (measured) to be twice as strong. What I think this is getting at is that torque is the variable we need to look at. The larger, within some constraints like pitch speed, the prop disk the better the performance.
Now a counter argument is that, in my day we had to give the four cycle engine double the displacement to even hope to compete with the piped 10 cc pattern ship. And these four stroke pattern engine often needed super charging on top of that! So again follow the torque curve (ref. my earlier post). That and the simplicity and light weight made the pattern 10cc 2 cycle engine all but impossible to beat. Did a 20cc four cycle ever hold a FAI F3A title?
This is still on subject as we are talking pattern power plants?
All the best,
Konrad