Originally Posted by
flywilly
Hi Tarquin,
Here are some pipe length starting points based on propeller choice for .60 sized engines. The pipe length is measured from the glo-plug to the first pipe baffle (measured from the front of the pipe).
PROP SIZE. LENGTH
10.5x7.5 - 11x8. 14.25 - 14.5 inches
12x9 - 12x10. 17.0 - 17.5 inches
12x11 - 13x10. 21.25 - 21.75 inches
These have worked very well for me for the past 34 years or so. I prefer to keep the pipe length a bit longer, especially for the larger prop loads.
Good luck - what engine, pipe, prop combination are you researching?
regards,
Will
Hello Will
I found some interesting things with my engine. Nominally the engine is a OS61RF-P but as the liner had peeled I replaced it with a performance specialties Hanno piston and liner. Since the case does not have the exhaust port ground out to match the liner I was treating it as if it was not a Hanno. I am not sure if this is a correct assumption.
With APC 12x11 open face I got just a shade under 10k. With the full length header and hatori long chamber pipe I was expecting a decrease in RPM but in fact I picked up to a comfy 10.5K. I was going to chop the header a bit but thought I would use your measure and found that I am already shorter than your recommendation. I then checked my hatori pipe against my Hanno pipe and found that it was near enough 40mm shorter to the baffle. SInce my hanno pipe looks a bit odd (it appears to be rolled and is slightly warped) I checked it against Rene's Hanno and pipe and it is definitely short.
Just for info I tried an APC 12x12N Pattern prop and got around 10.3K on the pipe. It was a bit peaky on the needle.
At this stage I am thinking of leaving the header as is and run the 12x11 and try it out in the air when I finally get the Beelte done. If it seems short I can probably get about an inch or so header spacer before I run out of room in the pipe tunnel.
Cheers
Tarquin