I have diamond dust with an os 32 with a pre tuned MACS pipe.
Can I shorten the pipe and get more rpms? If so, how much should I shorten it? What are the drawbacks to haveing too short a pipe? Tuning, engine life?

Here is something that has me wondering if the engine will go any faster.

I had a APC 8x8 and got 17,100 rpm on the ground with 15% fuel. I tried a 8x9 with 15% and had about 15,900 rpm.
I tried 30% fuel on the 8x8 and got about 17,000. I went a head and tried the APC 8x9 on 30% and got 16,900rpm. It seems like the engine was making more power but I couldn't get any more rpms. The 8x9 really moves the plane well.

You should have seen this engine and pipe on a .10 shrike. It was really screaming just before the wing came off.

Harlan

Yes you could shorten the pipe and get more RPM with the 8X8 on 30% but it will be faster with the 8X9 and 30% with the pipe where it is now.

another case of soft balsa spars !!!

A buddy of mine had a Wonder with an .18 on it and for it's size it moved out pretty good. Not anything extreme but sure has me wanting to get one.

I flew his a few times and they are so easy to fly. They are pretty predictable and very easy to land. His glided in for days before it would settle in. Cool plane thats for sure.

I think those Wonders and Shrikes are to cool. I have a few small .15 car engines and would like to see how it would work it it with a pipe. I have nothing else to put them in so should be cool to tinker with.

I have an OS .32SX on a Gremlin. I just got the following numbers. They seem kinda off but tell me what ya think,.... OK,.... its appx 35degrees outside and I got the following results: APC 9x6 15,600 , APC 8x6 19,500 , I am using a mouse can muffler, and Power master 15% fuel. It just seemed strange that the RPM's varied so much and seemed like the RPM's were a little higher than expected. I checked my tach and all was well,..... I even rechecked other planes and they all tached the normal rpm. Also,... what would be the best prop for all out top speed.


Thanks,
FUZZ

Not sure what a Gremlin is. I never seen one of those before so hard to say what size prop.

usually high speed props are in smaller diameter with high pitch. But it all depends on the type of plane also and weight. You can go to where the prop gets to small and has no thrust to tote it around.

If you go down in diameter go up it pitch. So if you was using 9x6 I would go down to a 8x7 or maybe 8x8 or 7x8. I am not sure if 8x8 is to much so just guessing here. These are just ballpark figures.

Experiment some with different props. You need to get as much RPM as possible to go fast. So thats where the smaller size props come in to turn fast. Then you find a good pitch that can turn fast with that certain size diameter. That should get you moving out pretty good.

The Gremlin is a flying wing type of plane used in combat and an all around fun speed plane. Mine weighs 3lbs. I havent flown it with the 8x6 yet,........ but I am also trying a APC 8x7.

thanks,
FUZZ

crazy4flight
Actually the spars were hard wood. It was a hole in the covering that did it in. I don't imagine it would have survived the first few flights with the balsa spars. I really like the diamond dust better. Wide open straight down with a last second yank on the stick with no worry of the plane coming apart.


Thanks for the info ewspears. I guess I will leave it alone for now.

harlan