Mr. Neumann, how'd ya do it?

I saw one of your FP 40's for the first time at a contest recently and was impressed with the consistency of the run. Very little difference in lap speed from start to finish. It was on a Brodak's Tanager. Couldn't help but wonder how this motor would perform on a plane that actually needed a 12x6 prop. Every plane I have that requires a 12" prop is in the 60oz.+ catagory. Also, how in the name of all things Holy, can you get a .40 size motor to swing a 12x6 without sagging and without achieving core meltdown temps.? Mr. Neumann, how'd ya do it?

Now you don't expect me to tell you everything, do you? Even though you talk about 60 ounce planes "needing" a 12 inch prop (I actually prefer to go to a 13 inch prop when we get that heavy), smaller, lighter planes can benefit from the larger prop, too. In fact, we used a 56 ounce, 570 square inch plane as the test bed for the .53 Magnum with a 13 inch 3 blade prop, and it was not too much prop at all. Pitch controls lap speed. Diameter controls slippage--like putting wide tires on a dragster. A bigger prop will give you something that will dig in the slippery air. It gives you greater tension overhead, and increased drive to power through the wind.

There is a point of absurdity, obviously, where you can get too big a prop (or too small of a wing.) If it starts to hurt the turn, you can always move the CG back a little to compensate. But if the prop stops and the wings start turning, you have probably gone a little too far.

Sorry about the percieved industrial espionage. Anyway, "Controlled Runaway" is not my preffered engine run. Just curious.

Well, in answer to your question, the real key to these engines is blocking off the boost port. It was not a part of the original Schnurle design and was added for one purpose only--to boost the high rpm, which is exactly what we don't want or need.

It is not a simple matter of blocking off the boost port, however, as setting deck height is also important, as well as compression, and so forth. On the FP engines I have found timing on the sleeve rather consistent (as it should be). Variances here are rather minor, although one sleeve was found to be ten thousandths off. Deck height is another thing on almost every engine I have worked on, and varies all over the place. I have a standard deck height that I set each engine to, and this involves dropping the sleeve--after measuring it up.

Now, interestingly, I have started to work in earnest on the TT 36 design since the FP engine may be a thing of the past (you never know if they are going to bring it back again or not). The TT 36 is a ball bearing engine, with a case width and mounting hole spacing of the Fox 35, and a weight that is 2/10 of an ounce LESS than the 35 FP. This should turn out to be a killer if I can get it right, and I hope to bring it in within about $15 or $20 of the current FP price. But in measuring seven different sleeves so far, I have found that the timing on these varies all over the place. The key to my rework on these engines will once again involve the blocking off of the boost port, but I must also work out the proper timing as well as compression, and then set each one the same.

Those people who say, "Raise this port so much", have never measured the variances on an engine. And if you ask me what I need to do to modify your engine, I won't know until I measure everything.