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Engine basics => Engine set up tips => Topic started by: Craig Beswick on April 22, 2020, 09:07:52 PM
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Hello all,
I am completing a Bob Palmer Hurricane and for the sake of scale I would like to use a three blade prop.
I am putting an OS 46LA in it and have read most of the 46LA, "Set up", posts but couldn't find one with a three blade prop. Is it not the done thing? Are there draw backs in using a 3 blade prop?
I was thinking of a 10 x 5, if okay to do so, any other suggestions?
Thanks
Craig
Ps. Engine is brand new stock standard.
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Hello all,
I am completing a Bob Palmer Hurricane and for the sake of scale I would like to use a three blade prop.
I am putting an OS 46LA in it and have read most of the 46LA, "Set up", posts but couldn't find one with a three blade prop. Is it not the done thing? Are there draw backs in using a 3 blade prop?
I was thinking of a 10 x 5, if okay to do so, any other suggestions?
Thanks
Craig
Ps. Engine is brand new stock standard.
Craig,
I have many three bladed props purchased for an OS LA 46.
Some carbon fiber also.
PM or email if interested.
Charles
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I was thinking of a 10 x 5, if okay to do so, any other suggestions?
That sounds a little too small and a lot too much pitch. I would probably start with a 11-4 3-blade, and then work up to a 11.5-4 3-blade.
Brett
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The general starting point rule of thumb when going from two blades to three is -1" in diameter and +1" in pitch. Less diameter to maintain rev range with additional prop area/drag and additional pitch to compensate for dirty air and slightly lower angle of attack to air flow behind leading blade.
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Thank you for the input.
So no real issues with going to a 3 blade just finding the right size.
Thanks again
Craig
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The general starting point rule of thumb when going from two blades to three is -1" in diameter and +1" in pitch. Less diameter to maintain rev range with additional prop area/drag and additional pitch to compensate for dirty air and slightly lower angle of attack to air flow behind leading blade.
To clarify, unless I am mistaken. A 10x5 three blade is about the equivalent of an 11x4 two blade. If I am off, please let me know.
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To clarify, unless I am mistaken. A 10x5 three blade is about the equivalent of an 11x4 two blade. If I am off, please let me know.
No, pitch is pitch. What you want is something like a 11.5-4 3-blade if you have a flat-backed or semi-symmetrical airfoil, and maybe 11.25-3.7 3-blade if the airfoil has undercamber. If the 11.5 is too big, you can cut it down.
Brett
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I use a Master Airscrew 11x6 3 bladed prop that I cut to 10” or 9-7/8” on my LA 46 powered Vector, the full blade is to much load on the engine. This prop work really well except on windy days. In the loops the 3 blade really winds up a lot more than the APC 12.25 X 4. I tried the Master Airscrew 10x5 but it does not have the same holding, stability that the cut down 11X6 3 blade has. The 11X6 has wider blades and I think that is making the difference over the stock 10X5. MS does not make a 11X5. I really like the way the Vector fly’s with the cut down three blade, but I keep the APC 12.25X4 in the flight box in case the wind goes over 10mph. I even cut the MS 11X6 down to 9-3/4 for my Brodak 40 powered Nobler and get the same results.
Al
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I use a Master Airscrew 11x6 3 bladed prop that I cut to 10” or 9-7/8” on my LA 46 powered Vector, the full blade is to much load on the engine. This prop work really well except on windy days. In the loops the 3 blade really winds up a lot more than the APC 12.25 X 4. I tried the Master Airscrew 10x5 but it does not have the same holding, stability that the cut down 11X6 3 blade has. The 11X6 has wider blades and I think that is making the difference over the stock 10X5. MS does not make a 11X5. I really like the way the Vector fly’s with the cut down three blade, but I keep the APC 12.25X4 in the flight box in case the wind goes over 10mph. I even cut the MS 11X6 down to 9-3/4 for my Brodak 40 powered Nobler and get the same results.
Al
Thanks for that info Al. Until the money fairy, or the hand-me-down fairy blesses me with carbon fiber blades, modified MA props are something I've tinkered with but hadn't tried modifying them.