direct connection tsunami/prop question

[capncrunch]

its more of a pattern plane... does it belong in this thread?

im almost finished with a pretty sweet covering scheme, pictures will follow. OS 46FX in the nose with an AUW in the neighborhood of 4.5 pounds.

one question though, why do people fly fun fly with low-pitch props? i see 40ish size engines running 11x4 or 12.5x3.5 props, when it seems to me that the opposite would be better, a smaller diameter prop with larger pitch would have lots of bite and spin up to pretty high rpm... can anyone explain this?

peace,

Barrett

[Ulf Rieder]

The low pitch props produce more thrust. It is not about higher rpm or speed, but for the unlimited vertical and instant thrust instead of reving up. Fun Fly planes shouldn't be flown fast anyway. They will flutter to death due to the large surfaces.

Ulf

[gordo-plast]

Yup, what ULF said. We want power NOW when the need arises. if you're not gonna hover, harrier, or other "Non-lift" flying (ie stall areobatics, 3D) there is no reason to think Greater lenth/lower pitch. The choice prop for the OS.46fx on a pattern plane would be 10x6 or 10x7, IMO.

Gordo

[capncrunch]

righto, those two questions were unconnected.

i'll be trying out 10x7, 10x8, 11x6 props on this plane, methinks.

but back to props, the prop doesnt make more thrust because of the lower pitch, its the size of the prop, right? you have to step down in pitch to let the engine rev to its power band, right?

barrett

[Ulf Rieder]

lower pitch allows for bigger diameter of the prop. That gives you more thrust.

Ulf

[capncrunch]

here she goes, maiden flights and subsequent flights (6 so far) were absolutely awesome.

[Ulf Rieder]

Looks great. Good job. So what prop did you decide on ?

Ulf

[capncrunch]

it *seems* that the 10x8 is the best for top speed, and since this plane is at full throttle pretty much most of the time, it works out well. im estimating ~100mph cruising speed. this is after trying out 11x7 11x6 and 10x8, with 11x6(wood - lighter than apc) and 11.5x4 yet to be tried (and 11.5" is stretching the clearance issue)

can i put a pipe on the os .46 fx after having run it on a standard muffler without any performance loss (compared to piping it from the beginning)..? if I did get a pipe, any recommmendations/prop suggestions?

13th flight today, very happy with her.

barrett

[Ulf Rieder]

well for speed, the n the 10x8 is probably right. Try a Ultra thrust muffler. Will give you around 1500 + rpm increase. Simply bolts on the engine like your muffler.
You can order them here : http://www.pspec.com/html/muffler.html

If you want one, I can sell you one of mine for which I have no use for right now. Send me a PM if interested.

Ulf