Rubber

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Re: Rubber

Post by obstinate » September 3rd, 2010, 11:28 pm

How many winds, realistically, should our models be landing with?
I read that most wright stuff models use up all their winds before touching the ground...
is this realistic for helicopters?

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Re: Rubber

Post by smartkid222 » September 4th, 2010, 6:56 am

Actually i think that WS models, properly trimmed, should have some winds left over. You should expect the same with heli. maybe 50 (out of 1000) winds left? If you run out of winds the heli/WS goes dead stick, which generally isn't good.
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Re: Rubber

Post by obstinate » September 4th, 2010, 8:04 pm

Oh, what i was saying was that mine landed with a significant number of winds left....

also, is there a proper way to tie the knot in the rubber?

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Re: Rubber

Post by awesomeness » September 21st, 2010, 2:40 pm

How does the width of the rubber band factor in helicopter flight?

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Re: Rubber

Post by jander14indoor » September 21st, 2010, 7:13 pm

Like Wright Stuff, rubber width is used to control the torque (and power) of your motor. Not enough (too narrow) and no lift. Too much (too wide) and you drive into the ceiling and run out of winds too soon.

How much is too much or too little depends on your rotors. Unfortunately, I'm not sure there's the wealth of experience there was with Wright Stuff to recommend good starting points. Expect a LOT of testing to determine the best matches.

Fortunately, you can run fairly complete helicopter tests in a closet if you spend some time developing a test rig. Less need for gym time than WS. Still need some, but more can be done in a small space.

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Re: Rubber

Post by illusionist » September 23rd, 2010, 3:13 pm

Could you explain how I can go about flying it in a closet Jeff?
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Re: Rubber

Post by awesomeness » September 26th, 2010, 8:23 am

about how much does the knot weigh? i'm about to cut my rubberband, but it cant be over 2 grams. i'm guessing the not will way .5 grams or less.. if i just cut it at 1.5 grams, will i be safe?

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Re: Rubber

Post by illusionist » September 26th, 2010, 2:39 pm

From my wright stuff experience, the way I do it is I measure rubber that weighs around 2.1 grams, so that when I tie the not and cut off the "pigtails" that are left over, I end up with a rubber loop w/knot that weighs 2 grams. That might not be the best method, but its always worked for me, and the final weight is just under 2 grams.
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Re: Rubber

Post by jander14indoor » September 26th, 2010, 7:47 pm

Whatever you do, DON'T cut the rubber band to 1.5 grams. Mass is your fuel, using a 1.5 gm rubber band is like filling the tank 3/4 full on an endurance race! The knot doesn't ADD any weight, it is part of the rubber band to start with.

OK, here's how I do it.
Cut the motor to as near, but under 2.0 gm as you can, say 1.98 gm or so. Include your O-rings. Good O-rings only add 0.04 or so to the mass and are more than worth it when stretch winding. Remember, you want your motor to pass the judges scale, but not give away any energy you don't have to.
Now, lube the motor. Yes, that right, lube it before you knot it. The knot I use has never slipped for me in 10 some years of flying and coaching. But its hard to tie without damaging the rubber if not lubed.
Now, lay the two ends side by side, pointing the same direction and even. Tie an overhand knot to join the ends. If you don't know what an overhand knot is, see: http://www.iwillknot.com/overhand_knot/
Don't worry about where the knot is in the loop or long tails. The next step will fix that and is why you want to tie lubed.
So, now we have to move the knot. Grab the two strands coming out of the knot, on the same side of the knot, on the loop side of the knot, one in each hand. Pull apart gently. The knot will start moving away from you towards the tails. Keep pulling until the tails are short as you dare. I generally leave mine 1/8 inch long or less. Any rubber beyond the knot only adds weight without contributing to flight time.
OK, here's the slightly tricky part. Tie a SECOND on the loop side of the first one, but in the OPPOSITE direction of the first. Here's how I remember, I've tied so many overhand knots since my boyscout days without thinking, that I just think and tie it awkwardly backwards. Works for me anyway.
Now, time to move this knot too. Grab the strands on the loop side of the knot and pull apart till the knot moves up against the first knot. Give it a good tug. Your done.

Here's a version of the knot in pictures: http://cloudbustermac.tripod.com/knot-page.htm I do it a little different because that person is tying the motor to length, and we're tieing to length.

Hope that's clear.

Jeff Anderson
Livonia, MI

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Re: Rubber

Post by chalker7 » September 27th, 2010, 5:40 pm

Jeff, You're forgetting the possibility that having a lower rubber mass will lower the overall flying mass of the helicopter and possibly be better. While I think teams should absolutely start out as close to 2.00 grams as possible, lowering motor mass may be a good experimental variable for teams as they advance throughout the year.
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