Prop pitch

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Prop pitch

Postby mumdad696969 » Wed Jul 11, 2018 3:01 pm

Hi all . Anyone know much about GT props ? Theres 1 for sale , GT2 157 x VZZ ?? What pitch is that? Cant find any
info on it anywhere ???
Mike Gregory
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Re: Prop pitch

Postby mumdad696969 » Sat Sep 08, 2018 12:35 pm

Is there anyone out there who can help me with prop pitch?? I tried everything! I have a gt2 prop 157x98 on a savannah and have rubbish cruise. I have borrowed a prop to try but no idea what the pitch is. I can't warrent paying £900 just to try a prop, can anybody advice how to measure pitch? Or what prop I could buy that would guarantee to have the desired effect. And before people tell me you can't make a flying box do 200mph. I know its not a fast plane. But I'm getting at least 10mph calibrated, less than stated expected figures. 70 to 75mph at 2800revs on a 80hp jab engine is rubbish. Can anybody help??
Mike Gregory
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Re: Prop pitch

Postby mikehallam » Sat Sep 08, 2018 4:15 pm

Mike,

Props are oftem pitch measued using some form of clinometer at 2/3 dia.
Warp drive make it easier to position by have a square tip and placing the bubble gauge there. Take each blade at 3 and 9 o-clock and also add/subtract the crankshaft tilt when taking readings.

Blade area, thickness and profile all have =/- effects and for a draggy a/c possible a larger blade area is better, but it's a dark science best left to the propeller designers & manufacturers to advise.

All I can say is that my short wing 80 h.p Rotax Rans S6-116 enging runs much faster at 4,800 rpm in the cruise, and one is then whizzing (creeping ! )along in the 80's mph.

IMHO. Always best if in new territory to ask your Inspector - he may have all you need.

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Re: Prop pitch

Postby mumdad696969 » Sat Sep 08, 2018 9:13 pm

Thanks Mike.. Most appreciated. Inspector says fly it and try it. And the importers and sky craft give very little info to help.
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