Prop pitch, rpm, and performance

Discussion in 'Firewall Forward / Props / Fuel system' started by Dana, Nov 13, 2019.

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  1. Dec 12, 2019 #81

    blane.c

    blane.c

    blane.c

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    My foot is the exact size of a Kings foot. Hmmm, I wonder?
     
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  2. Dec 12, 2019 #82

    BJC

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    Naw ....
     
  3. Dec 12, 2019 #83

    blane.c

    blane.c

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    Darn!
     
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  4. Dec 12, 2019 #84

    poormansairforce

    poormansairforce

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    Yup, just like the Supreme court ruled in 1781!
     
  5. Dec 12, 2019 #85

    mcrae0104

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    I was thinking about that the other day for no particular reason. It would be more consistent if a car standing still was considered to be doing 32 mph.
     
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  6. Dec 12, 2019 #86

    AdrianS

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    Have you tried on the glass slipper?
     
  7. Dec 14, 2019 #87

    blane.c

    blane.c

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    Wrong story dude.
     
  8. Jan 16, 2020 at 6:31 PM #88

    Armilite

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    =======================================
    https://en.wikipedia.org/wiki/Lycoming_O-290
    O-290-D Certified 13 December 1949. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes (Only for Takeoff), 6.5:1 compression ratio, dry weight 230 lb (104 kg).[1]

    Using 77F and Standard (2) Blade Prop: Are you sure these are the right Pitch Numbers?

    74"x50 Sensenich metal prop if Pitched for 2700rpm Calc says for (2) Blade 586.12 lbs Static Thrust and needs 200.494 hp!

    74x47 Sterba wood prop calc says for (2) blade 586.12 lbs Static Thrust and needs 188.464 hp!

    For your 130hp Pitched for 2700rpm using a 74" x 32 (2) Blade seems the best! Calc says 586.12 lbs Static Thrust and needs 128.316 hp!
    http://godolloairport.hu/calc/strc_eng/index.htm

    O-290D Manual
    https://www.lycoming.com/sites/default/files/O-235&O-290 Operator Manual 60297-9.pdf
     

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  9. Jan 16, 2020 at 6:57 PM #89

    TFF

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    Your calculator is for RC props it looks like. At least I have two of the brands listed. No standard airplane prop listed. Dana’s plane easily has double the drag of any “fast” airplane. It won’t go fast no matter. I think the program model is off when going big.

    I have experienced it with engine programs. When racing karts a friend and I found what the program said was the magic exhaust pipe. We made one. The standard race pipe was faster. It was at least fun taking it through tech and getting complaints and pointing to the rule book. Legal. No one in racing likes different.
     
  10. Jan 16, 2020 at 7:07 PM #90

    Dana

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    Armilite, your numbers are meaningless... nobody would expect an O-290 to reach 2700 static rpm with a usable prop. And as I said before, static thrust numbers are meaningless when you're optimizing for 60 knots.
     
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  11. Jan 16, 2020 at 8:02 PM #91

    Pops

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    I built a LYC-290 that turned a Sensenich 74 x 56 prop at 2900 rpm in level flight at 3k.
    How many HP was it producing ?
     
  12. Jan 16, 2020 at 8:35 PM #92

    blane.c

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    around 100hp I would guess?
     
  13. Jan 16, 2020 at 11:07 PM #93

    mcrae0104

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    What airframe (so that drag could be guesstimated) and at what TAS?
     
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  14. Jan 17, 2020 at 12:05 AM #94

    Pops

    Pops

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    Falconar F-12, EW weight 937 lbs, 27' 6" wing span, 2 place side by side tail dragger. 137 ft of wing area. Cruise at 150 mph true, ROC at GW of 1600 lbs at 1700 fpm. It also has higher GW of 1800 lbs with less than the +9 G's positive and -6 G's at 1600 lbs. With just me and 20 gal of fuel the ROC was 2200 fpm.
    Flew it for 5 years with a lot of traveling over the U.S.
     

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