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3-blade propellers

Old 02-28-2008, 11:26 AM
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tlroliff
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Default 3-blade propellers

Just looking for some general input on 3 blade prop selection. I have zero experience with them but would like to run one on a GP P-6E Hawk I am putting together. I will be running a Saito 1.50 FS and am thinking I will use a 17x6 2 blade for the first flights. Suggestions on manufactures would be helpful also. Graupner and Master Airscrew don't appear to go larger than 16 in. diameter.

Thanks in advance.
Old 02-28-2008, 12:38 PM
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dasintex
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Default RE: 3-blade propellers

The rule as far as what size of 3 Bladed Prop to use is to decrease the Diameter by 1 inch and increase the Pitch 1; so for the 17 X 6 2 Bladed Prop you would need a 16 X 8 3 Bladed Prop as an equivalent to the 2 Bladed Prop you listed.
Old 02-28-2008, 01:36 PM
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bbagle1
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Default RE: 3-blade propellers

Xoar hads some vey nice 3 blade props, zinger can also make you whatever soze you need.
Old 02-28-2008, 02:23 PM
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Default RE: 3-blade propellers

I have run a 16x8 three blade, both Graupner and MasterAirscrew on my Satio 1.50 and they are a bit much only allowing about 8,400 rpm. The Master Airscrew 15x7 3B is perfect for the 1.50 as is the Graupner 14x7 3B due to its wider blades. People tend to forget that adding the 3rd blade is a 50% increase in load, the one inch rule simply does not allow for this.
Old 02-28-2008, 05:24 PM
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pe reivers
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Default RE: 3-blade propellers

you are right , though the load increase is slightly less than 50%, more like 35-40% because the blades now work in a higher slipstream speed due to the higher prop disk load.
It is the prop disk load that accelerates the air mass passing through it. (according to one theory, and the Newtonian action=reaction law)
Old 02-28-2008, 09:11 PM
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blw
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Default RE: 3-blade propellers

Pe- yes, better load distribution along with reduced vibrations. Sideslips and turns are better. Asymmetrical cowl/body shapes benefit from more than 2 blades.
Old 02-29-2008, 12:06 AM
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Default RE: 3-blade propellers

They help slow the plane too, it's like you droped flaps when you thottle back.
Old 02-29-2008, 10:45 AM
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Default RE: 3-blade propellers

Yes, that is true and a reason some pattern guys are using them.

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