Propellers

jander14indoor
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Re: Propellers

Postby jander14indoor » September 24th, 2009, 3:48 am

Probably not because it has little effect on prop speed. That is driven more by aircraft drag, prop pitch and diameter, and torque (which is driven by winds and rubber width, NOT hook length).

Hook distance has a little more effect on energy stored and returned, but not large until you get to silly extremes.

Note, many students seem impressed by the slow turning props on well tuned planes and ask how its done. Actually you don't directly control prop speed, its a by-product. As you make your plane more efficient by losing weight and minimizing drag, it takes less power to pull the plane through the air, you can use thinner rubber with less torque, and the speed naturally drops.

You can also slow a prop on a given setup by increasing the prop pitch, but then you have to increase torque (increase rubber width so less turns possible) to fly it and the net trade off for flight time is a wash.

Concentrate on light weight, efficient trim and matching prop and rubber to the plane. Slow prop speed naturally falls out of that.

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Re: Propellers

Postby Cyrus_D » September 26th, 2009, 3:00 pm

Thanks Jander, I will really take note into that.

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Re: Propellers

Postby smartkid222 » November 15th, 2009, 3:11 pm

I belive someone last year on the thread reccomended the Harlan penny plane thrust bearing over the SO one? is there a reason for this?
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Re: Propellers

Postby jander14indoor » November 16th, 2009, 5:57 am

In the past, Harlan's Penny Plane prop hanger had the split rear allowing you to remove the prop and wire from the plane to change props easily.

The SO prop hanger did not. Just a hole in front and one in back. Had to cut the prop axle to remove and change props, and a new wire required for the new prop.

I assume its still the same, but I don't know as I make my own prop hangers.

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Livonia, MI

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blue cobra
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Re: Propellers

Postby blue cobra » November 18th, 2009, 12:41 pm

What's the best shape to cut the propeller into?
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Re: Propellers

Postby eta150 » December 3rd, 2009, 12:28 pm

At the risk of sounding like a fool, are the ikara props easily attached to the Ray Harlan assembly? And, if so, is there enough of a difference that it is worth it?
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Re: Propellers

Postby jander14indoor » December 3rd, 2009, 2:09 pm

I find it easy to do. Cut the wire on the old hanger. Replace with new .020 (I think, should check) music wire.

I find it worth doing because I find the Ikara prop hanger flimsy and hard to attach properly. The Harlan is more robust and easier to attach to the plane. For me.

Even better than the Harlan SO hanger is the Penny Plane hanger which has a split tail allowing the prop to be changed without cutting the wire.

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Livonia, MI

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Re: Propellers

Postby smartkid222 » December 3rd, 2009, 4:27 pm

At the risk of sounding like a fool, are the ikara props easily attached to the Ray Harlan assembly? And, if so, is there enough of a difference that it is worth it?
Are you comparing this:
Image
(is this what is considered the Ikara prop hanger)?

and the Ray Harlan assembly?

If that is the ikara prop hanger then: when i did WS i used the freedom flights kits which used the ikara prop hanger which worked fine. The prop fits well into the hanger. the hanger is glued fairly well into the Motor Stick, you just have to make a cut which a part of the hanger fits into. I dont know if it's much better using the ray harlan assembly. I dont see any benefit except for less weight, but for WS the weight limit is easy to get close to.
Also thinking about Jeff's comment, the ikara prop hanger makes the prop detachable.
For the Harlan SO thrust bearing you can use .020" music wire for the prop shaft
for the Harlan Penny plane the hole is SMALLER, so you need less than ~ .017" MS
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Re: Propellers

Postby eta150 » December 4th, 2009, 10:55 am

thanks, that really helps
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Re: Propellers

Postby calgoddard » December 4th, 2009, 11:14 am

Yes - the image posted above shows the Ikara prop hanger from two different viewing angles (side view and rear perspective view).

At one time you could purchase prop hangers from a supplier named Geauga that were suitable for Wright Stuff planes. They were fabricated from a tiny block of Aluminum alloy that was precision milled. These beautiful pieces of workmanship were not subject to bending on frontal impact during flights and had a pig tail rear end that allowed removal and replacement of the prop. They were comparable in weight to the Ikara and Harlan SO prop hangers. A picture of the Geauga prop hanger is shown below. Personally I prefer the Geauga prop hanger.


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