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Author Topic: P30 rubberpower prognostications  (Read 935 times)
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DerekMc
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« on: November 14, 2012, 01:41:26 AM »

Idea: to use full length six and four strand motors in a shOrt motor tubE
Access the impact of fully wound motors in short motor tubes.

Procedure is to use see through rigid aQuarium tubing as the motor tube. Use a floating bobbin to smooth out the unwinding. Observe knotting behavior in various diameter tubes and it's effect on propeller efficiency. Interested inwhatcould haPpen and it's effects on a P30? Check back on this winter project.
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Derek
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« Reply #1 on: March 19, 2013, 01:19:24 AM »

Derek,
The idea is sound and if I recall correctly, Andriukov used to do that with several tubes loaded for his Wakefields before competion. 
However, I have some misgivings about it from my recent experience.  I was readying my Gollywock for a mass launch one time at Waegell, Sacramento, and had it fully wound, I mean 101percent wound.  But I missed the window so I locked itput it away, and waited for the regular rounds which would start in earnest during air picking time.
About a half hour of waiting it exploded and ruined my chances for the day.
I believe Alex was not fully winding but maybe to 80% (?)
Ding
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DerekMc
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« Reply #2 on: March 19, 2013, 01:48:46 AM »

I forgot all about that post. The idea was to use a long 6 strand motor in a short wide tube. Like half the length of standard motor tubes. Use a rubber anchor that can spin around the motor anchor and see how it unwinds. Carbon tube out the back to support empennage. Has possibilities. Somebody should try it!
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Derek
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« Reply #3 on: March 19, 2013, 02:05:53 PM »

Dereck, I like the principle of a short motor tube. The benefits would be similar to those of geared designs. I don't quite understand how you suggest achieving this. Could you offer a sketch to clarify please.

Martin
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DerekMc
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« Reply #4 on: March 19, 2013, 04:24:08 PM »

Dereck, I like the principle of a short motor tube. The benefits would be similar to those of geared designs. I don't quite understand how you suggest achieving this. Could you offer a sketch to clarify please.

Martin

The idea comes from the world of FF scale models. Specifically short nosed ones. People are very successful using an incredibly short prop to motor peg with long motors.  They use a sleeve over the motor peg to hold the rubber that allows the motor to move around on the rear peg. Scale models tend to have lots of fuselage space for the motor which your tipical P30 does not. My thought is to shorten the tube, like a geared P30. Increase the tube diameter so it lessens the chance of the motor knots hanging up on the motor tube and use a sleeve on the rear motor peg.

I thought of using different widths of clear hard plastic aquarium tubing as motor tubes to see what the rubber motor is doing as it unwinds. To reiterate use a full length motor in a short tube.
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Re: P30 rubberpower prognostications
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Derek
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« Reply #5 on: March 20, 2013, 01:33:10 AM »

I'm going to follow your progress on this, Derek.  Seems like a good idea.  Much lower moment of inertia, any knot bunching would be closer to the CG, the potential to reduce tail areas or shorten the fuse because the nose moment arm will be shorter, etc.  Wonder if the weight tradeoff is positive or negative?

My Titan modified for long motor run had about as long a nose moment and as short a tail moment as looked reasonable.  Any more tail weight and I don't think it would be a good model.  Your idea would certainly address that, and like you said, the scale flyers are using motors 2x and 3x the hook-to-peg distance, so why not here?  Hmm...my Titan re-build isn't finished yet...I could roll a short tube...

Keep us posted!

--Bill
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« Reply #6 on: March 20, 2013, 06:21:09 AM »

Derek

An excellent bit of lateral thinking - thanks. Another fuselage to build methinks   Roll Eyes

Peter
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