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Rubber Power Question (Going Old School with an Earl Stahl Hi-Climber)

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Rubber Power Question (Going Old School with an Earl Stahl Hi-Climber)

Old 08-15-2013, 11:06 AM
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Bigshark
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Default Rubber Power Question (Going Old School with an Earl Stahl Hi-Climber)

My experience with rubber band powered planes has been of the dime-store variety. I'm making a stick and tissue Hi Climber with my 6 year old son and the plan glosses over the "14 strands of rubber" for the motor like everyone knows exactly where to go from there. It also speaks of winding "750 turns" "if stretched out two and one half times." The plan is from 1939 so maybe everyone did know then.

I've seen pictures of folks winding rubber powered planes with the prop and nose block hanging out of the plane but I can't seem to find any info on how long to make the rubber strands or how to do serious rubber powered stuff at all. Any info or source of info would be appreciated.

Thanks,
Rich
Old 08-16-2013, 07:02 AM
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Rich, the Hi-Climber isn't all that big a model. So I would suggest that a good motor and prop combo would be 8 strands, or 4 loops, of 1/8 and a 10 inch carved prop. If you don't plan on carving a prop and will go with the more available 9 inch plastic prop then start with 6 strands of 1/8 since the plastic props have a lower pitch than a typical carved prop and run out the power too fast otherwise.

The motor should be about 1.25 to 1.5 times the hook to hook distance for the model. This produces a nice run with minimal bunching up issues as the motor runs down. And the prop block should ideally use a tension stop setup that stops the rubber from unwinding all the way and disengages the prop so it can freewheel.

This length thing most certainly means that you want a stooge and winder since you WILL be stretch winding even for the lower powered test flights. Even if the "stretch" is simply enough to take up the slack.

From there it can become funky. A lot of contest flyers use blast tubes. But for sport flying it's easier to simply never wind up the motor that far and instead just wind the motor with the prop and nose block in place.

You want to lube the motor too. Products like rubber grease or Son Of A Gun can be used directly. Or you can make the classic old lube out of drugstore liquid hand soap, glycerine and a dash of castor oil. The recipe that works for me is half and half soap and glycerine then add about a 10% dash of castor oil and shake well. Just be sure to get the thickest liquid hand soap you can. Or pour it out on a pan and let it dry/thicken for a while before making the lube.

In use check your motor at least once a day for signs of nicks in the edges of the strands. Small feathers of rubber is normal. But any of these nicks that pass completely across the edge from face to face of the strand are a broken motor looking for a moment to ruin your day. But if you only wind up to 75% for sport flying you'll easily get a hundred or so winds from the motor.

If the motor pukes out the nose and gets sandy switch it out for a clean one and clean it when back home. Grit and sand is death to the rubber when you wind it again.

And DOOOOOO put a DT system on that model. A Hi-Climber is VERY capable of going up-up-and-away never to be seen again otherwise.

Last edited by BMatthews; 08-16-2013 at 07:07 AM.
Old 08-16-2013, 08:54 AM
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Bigshark
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Thanks a bunch for the info. I can't imagine carving a halfway efficient prop so I'll be using what's commercially available. I'll have to find some info on de-thermalizers too although our field is notorious for near zero thermal activity.

Thanks,
Rich
Old 08-16-2013, 08:16 PM
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Originally Posted by Bigshark View Post
......although our field is notorious for near zero thermal activity,,,,,,
You say that NOW!

Even if for some odd reason there are not many thermals around you a DT makes it easier to fly in marginally windy conditions by allowing you to control the flight time to a higher degree and keep the model within the field. So it's still well worth the effort to get and use one which can be decently calibrated to some reasonable consistency.
Old 11-13-2013, 10:19 PM
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Just got back into the field myself and building indoor models as it is winter here in Washington state...see a2zcorp.us and the book Rubber Powered Model Airplanes by Don Ross...basically the same time frame as your model with all the tricks of the trade..also rubber lube and other issues.
Also they have "tan rubber" in varying sizes and lengths and they " speak rubber models" when you talk to them..answer promptly and are quick to send stuff by US mail too... there are pages of tips by current modelers and you are not alone...

I found a California Models FEATHERETTE indoor model kit and plans I last built in 1954...Kit cost $1.00! got out my razor knife and remembered about 1/2 of how to build with 1/32 balsa frames and 1/64th balsa motor tubes..then I found the web site above and a lot more
came back..got 1 done now and covered and will go flying at the local gym on Friday PM...ask about, you may find a group of rubber flyers near you...still a lot of us out there..still is a US Wakefield Team flying in International rubber contests
Old 11-13-2013, 10:23 PM
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Is BMatthews a track rider or road racer? ...I had to give up track time this year and am selling off my Mille R Aprilia...wife and doctors suggestion...good news it means more time for models and 1:1 scale glider flying though as long as it is 2 place...
Old 11-13-2013, 10:35 PM
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A2zcorp.us also has winders at 5:1. 10:1 and 15:1 ratios for as little as $8.00

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