Have any of you run props like this?
04-29-2007, 10:33 PM
#1
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Have any of you run props like this?
I have seen a few of these from time to time. Very few actually. I am betting most are hand made. Certainly they would need hand balancing!
I believe this to be a Tee Dee .020 I can hardly imagine this to be a .010. There was no text other than that which I scanned here. I wish there were a little more info...
I am drawn to the unusual!
Robert
I believe this to be a Tee Dee .020 I can hardly imagine this to be a .010. There was no text other than that which I scanned here. I wish there were a little more info...
I am drawn to the unusual!
Robert
04-29-2007, 10:46 PM
#2
RE: Have any of you run props like this?
I've asked the C/L speed flyers about it. You can run more diameter and blade area with one blade and if the engine can rev high enough there will be a performance gain. There is more vibration with one blade, and there is no way to truly cancel it out. The AMA rules book has a diagram for how to build them. The type of airframe matters too, you wouldn't put a dragsters' torque converter in a dump truck......the way I understand it the single blade idea is only more efficient [than 2 blades] in a speed application. Good excuse to build a SWR, huh?
04-30-2007, 12:27 AM
#3
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RE: Have any of you run props like this?
On old time rubber models the counter weight was attached to a wire boom that was raked back a lot. Placing the counterweight to the rear tended to create a swinging effect that would counter the oscillating force of the thrust from the single blade. But there's no way I would want a weight on a wire swinging around at 25K ! ! ! ! ! 
However if your counterweight could be placed or at least concentrated towards the rear I think you'd see at least a reduction in the thrust coupled vibration.
However if your counterweight could be placed or at least concentrated towards the rear I think you'd see at least a reduction in the thrust coupled vibration.
04-30-2007, 07:37 PM
#6
RE: Have any of you run props like this?
They have been used on gas free flight models, too. Some of them even fold back after the engine is shut off.
BMatthews, those old timer, single blade rubber props are things of beauty. I have the plans for a Korda Stick (wing is on a pylon!) with a single blade folder shown. One day I will build it.
BMatthews, those old timer, single blade rubber props are things of beauty. I have the plans for a Korda Stick (wing is on a pylon!) with a single blade folder shown. One day I will build it.
04-30-2007, 08:29 PM
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RE: Have any of you run props like this?
I hate 'em personally. They'll run nice and smooth at one power setting and all the rest of the time it's jiggle.. jiggle.. jiggle.. jiggle.. I've done 3 or 4 of them in my days and on one I tried a lot to adjust the counter weight angles and other factors. It never did run smoothly the whole time.
The FAI 15 size control line speed models have used a lot of singles over the years. The assymetrical thrust leverage must create quite a buzz I'd imagine. Probably pretty hard on the engine bearings.
In one of the Zaic Yearbooks ( a collection that any true modeller should own) there's a rather long article on rubber model props. He basically makes a good point for the efficiency of the single as opposed to two or more blades. Heck, the only reason they used 3 and 4 or more blade props on the WW2 and later prop fighters was to lessen the need for stupidly long landing gear and prevent near Mach tip speeds.
Give me a nice two bladed prop anyday of the week....
The FAI 15 size control line speed models have used a lot of singles over the years. The assymetrical thrust leverage must create quite a buzz I'd imagine. Probably pretty hard on the engine bearings.
In one of the Zaic Yearbooks ( a collection that any true modeller should own) there's a rather long article on rubber model props. He basically makes a good point for the efficiency of the single as opposed to two or more blades. Heck, the only reason they used 3 and 4 or more blade props on the WW2 and later prop fighters was to lessen the need for stupidly long landing gear and prevent near Mach tip speeds.
Give me a nice two bladed prop anyday of the week....
04-30-2007, 10:16 PM
#8
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RE: Have any of you run props like this?
ORIGINAL: BMatthews
the only reason they used 3 and 4 or more blade props on the WW2 and later prop fighters was to lessen the need for stupidly long landing gear and prevent near Mach tip speeds.
the only reason they used 3 and 4 or more blade props on the WW2 and later prop fighters was to lessen the need for stupidly long landing gear and prevent near Mach tip speeds.
