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Old Oct 05, 2009, 02:37 PM
Oh no...hot glue is gone again
catman529's Avatar
Tennessee
Joined Feb 2007
922 Posts
Question
Problem with building a good rubber powered plane...

I've built countless rubber-powered planes, using those basic 7-inch rubber bands for the power.

The biggest problem that I can't seem to solve is the duration of the motor. If I go for good thrust, I make a small, fast a fast-spinning prop that winds down in only a few seconds. If I go for longer duration (bigger prop, lower RPMs), I don't get enough thrust to get the plane to climb.

I don't think I can get much over 100 turns with the rubber bands I use. Is it really worth it to use the "aviation grade" rubber over the conventional rubber bands?

The planes I build are not the problem - they are good fliers, and would fly high if only they had engines to keep them going a lot longer than they do.
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Old Oct 05, 2009, 03:50 PM
Registered User
Ajax, Ontario, Canada
Joined Oct 2004
2,568 Posts
>Is it really worth it to use the "aviation grade" rubber over the conventional rubber bands?

Yes. there is no comparison between conventional bands and the strip produced specially for model aircraft. Try some Tan Sport or SuperSport and find a difference. You still have to match size of motor to model and prop, of course
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Old Oct 05, 2009, 03:53 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,289 Posts
If you've done a bunch of them now with the same rubber bands then there's two options. Fist is use a big prop and use two of the long rubber bands together. You'll have to use less turns but you'll have twice the power to work with.

Another option is to loop-chain three or four of them together to form a three or four times as long motor then put one end on the tail hook and loop the middle around the prop hook and then put the other end on the tail hook. Now you've got twice the strands on a 1.5 times or 2 times length motor so you can use more turns and have more torque.

The only other way to make a model climb better with a fixed amount of power is to make the model lighter. Not knowing what your models are like it's hard to say if this is an option or if you're already making them to indoor model like standards for weight.

In the end though if you know you're going to continue to make rubber models for some years to come then a one lb box of 3/32 or 1/8, depending on the size of models you like, is a good long term investment. Store the excess in the bottom back corner of the fridge where it's out of the way and it'll last for literally years without any issues. I'm still using "new" rubber that is now more than 10 years old and it is still working just like new thanks to living in the fridge all of this time.
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Old Oct 05, 2009, 04:32 PM
Oh no...hot glue is gone again
catman529's Avatar
Tennessee
Joined Feb 2007
922 Posts
Thanks...might have to look into some Tan Sport...for the time being, I might try chaining a couple bands together (tried that only once or twice before). I just want a good plane that will go up at least 50 feet or so before losing power.

Most of the time my building materials are EPS (foam plates) and a bamboo skewer. And a little hot glue to put it all together. So that might give you an idea of the weight of the aircraft...I would rather fly them outdoors than indoors.

With the cheap rubber I have now, I might try and build a glider-type plane using 2 or 3 bands and see if I can get some decent climb and flight times.

EDIT:
One other question - is this the right place to buy the Tan Sport rubber?
http://www.faimodelsupply.com/
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Old Oct 08, 2009, 07:56 PM
Registered User
United States, MA, Waltham
Joined Dec 2001
6,919 Posts
That's the place. And you'll be amazed how much better the good stuff is. Meanwhile, lube your motor and stretch it out when you start to wind, letting it shorten as you get more turns in. Silicone grease makes a good lube, or tincture of green soap with the alcohol boiled off mixed 50 percent with glycerin (the old fashioned formula). I use Formula 2001 rubber treatment. Not the other stuff, but the kind that's meant for rubber. (and maybe some other things, but rubber is one)
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Old Oct 09, 2009, 09:48 PM
Zach
Illinois
Joined Feb 2004
806 Posts
Of all the modeling supplies out there FAI rubber is the one I couldnít do without. I can carve my own props, I can find substitutes for balsa, I can do without dope and Jap tissue. But Iím yet to find a substitute for rubber.

My favorite lube is Son-Of-A-Gun. Itís a Armor-All type cleaner for car vinyl. Just spray a little in a bag, toss in a rubber band and roll it around.

When you wind and unwind rubber itís constantly rubbing against its self and with rubbers incredibly high friction coefficient a little lubrication makes a big difference. Stretch winding can also improve performance

Zach
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Old Oct 09, 2009, 11:03 PM
Zach
Illinois
Joined Feb 2004
806 Posts
Catman,
I just remembered something. Bill Kuhl emailed me a while back and he has designed a new, easy to build glider thatís built from foam plates. I think itís right up your alley. Bill also has a video of the planes design process on his home page. If you give it a try let him know what you think, he loves feed back.

Here is a link to the plan: http://www.hbci.com/~bkuhl/FoamJetII.htm

Zach
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