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Thread: Prop pitch

  1. #1

    Prop pitch

    Hi all , I'm soon to be buying a savannah classic , the stol is great , cruise not so great . It has gt2 prop 157x98 , does anyone know much about this configuration? Would changing to 157x100 or 151x107 make much difference ? All 3 props are aproved , but without buying 1 to try , could be an expensive experiment ??
    Mike

  2. #2
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    I don't know, the manufacturer will but if the aircraft is designed for stol, the wing may be the limiting factor

  3. #3
    To a degree yes , but must be some option to increase cruise slightly ?

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    The pilot formerly posting as MadamBreakneck
    One-to-one ground school, ground exams , and certificates of experience. PM me for details.

  5. #5
    Looks good Joan, I wonder how much it costs ? Reckon I'll get 1 for 50 ? Haha

  6. #6
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    Ooh, only about $1000 I believe, plus the approval costs; a mere snip for a 912 owner :-)

    On a practical slant, I reckon the 151x107 would give a bit of extra cruise at the cost of a bit of STOL performance and higher fuel consumption. How much extra speed though? Pure guess = square root of (107/98) -> 1.04 so an extra 3-4 mph roughly... ish? (if it's a cube root function, then it'd be an extra 2 -3mph at best). There used to be a TIL about propeller choice on the BMAA web site but it doesn't seem to have made it through to the new one though it is still there on the Internet Archive if you are really interested.

    Maybe one of the aero engineer type bods on here might help, or failing that a call to the Savannah importers, perhaps. Do share what you find out, please, so it's useful for others.

    Good luck - and enjoy your aeroplane
    The pilot formerly posting as MadamBreakneck
    One-to-one ground school, ground exams , and certificates of experience. PM me for details.

  7. #7
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    Cheapest option is run the donk a 100 or so rpm faster. Then you retain the stol as now and for the cost of a very little more fuel can experience a slightly faster flight without changing anything.

    Coarser prop doesn't always equate faster either !

    My 80 h.p. Rans has a ground adjustable Warp Drive two blader. I've experimented over the years with coarser and finer settings i.e. about 1/2 degree at a time. The coarser end (15 degrees at the tips) gave sluggish take off, and top speed the same no better. Cruise rpm a fraction lower but fuel usage - as one would expect - is the same, for speed = power used.

    In the end a finer setting for me still allows good all round performance. It's never going to be a greyhound, if that's what you want, cheapest option is to buy one and not sshave a poodle to look like one !

    mike hallam.

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    Visions of a drone with long ears preceding Savannah...

  9. #9
    Thanks Joan and Mike, can't get hold of the importer , apparently unless your wanting to buy a new 1 hes not interested ! , I'm still curious , if only I could borrow 1 to try , tomshep , what is that supposed to mean ??????

  10. #10
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    Think electric hare.

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