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Old Jun 08, 2016, 08:35 AM
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Drop-Off-Motor Sailplane Launching

Looking for input:

Have several sailplanes, and numerous sizes of diesel engines that I like to use.

Limited ability to walk/move around. Retrieving winch line too tiring now.

Want to use drop-off motor that is tethered, ala a winch/high start line.

Interested in underslung motor on slender pylon strut, that is parachuted, then retrieved, via kite reel (very fast retrieve) etc,

Don't want fuel residue on model gliders, hence 6: O'clock downward strut.
Don't want to buy electric system, yet want any system to not weigh down model's wing loading.

My thinking is the motor/parachute retrieve system could be generic to similar size models.

This system, being contemplated, could allow me to fly thermal-type soaring gliders, and old timers, much more. No energy (walking) to do either winch or high start retrieves.

Servo-released .061, .15, .19 engine units would launch any size sailplane, with COMMON take-in reel eliminating walking for this handicapped flyer.

Fully understand up-thrust necessitating trim changes from under model engine location.
This seems so obvious a way to fly sailplanes/gliders , I wonder why it is not commonplace to launch models in this manner.
Engine struts would mounted @ CG, or slightly forward, to keep system more simple.

Just sounds fun, as well as doable.., to my limitations!
Any thoughtful discussion/input appreciated.

ScratchBuildrSAM _____AMA # 28854_____SAM # 1312
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Old Jun 08, 2016, 10:08 AM
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Why not just hit the easy button on this and build an E-fuse w/ electric motor?
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Old Jun 08, 2016, 10:22 AM
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+1 on that save your self effort and go electric. Folding prop no mess and done right easy as pie. No need to find motor and chute/ or what ever.
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Old Jun 08, 2016, 10:33 AM
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I agree with the above two comments. Having a drop away motor sounds like a PIA not to mention the noise of an engine. I electrified an old Oly 650 and the total investment was less then $50 and maybe 5 hours of my time and that included repainting the fuse and it came out pretty nicely and weighs less then it did when it was a pure glider.

Cheers,
Jim
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Old Jun 08, 2016, 11:47 AM
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It's sounds somewhat complicated, although solving problems is part of the hobby. I'm picturing a glider sitting upside down on the ground while you start the motor, then having to flip the whole thing over and launch it all without cutting yourself up. Gonna be tricky with the motor directly below the wing. Dragging the motor back through the grass/dirt doesn't sound appealing.
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Old Jun 08, 2016, 01:08 PM
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Jim, this sounds a lot like a government project.

I'm in agreement with the folks recommending that you convert your plane to electric power.

I do understand your feelings and thoughts on this, but I don't think it is particularly easy to manage the issues to do it.

Kudos to you though for thinking outside the box. Most of the best ideas are never in the box.

EJ
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Old Jun 08, 2016, 01:56 PM
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OP said that he likes to use diesel engines...

could even be done without any servo release: pod hangs on a pair of tandem tow hooks, engine thrust keeps it there, when the fuel runs out drag and maybe a bit of up elevator makes it slide off.

pretty sure this has been done in the distant past.
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Old Jun 08, 2016, 02:54 PM
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Other idea.....OP sells said diesel engines, invites Flying Buddy who happens to own TowPlane. Tows gliders up, release, fly!
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Old Jun 08, 2016, 03:55 PM
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Thanks, guys.

The engine would be on a parachute that is reeled in on a kite reel.
Engine not supposed to ever hit the ground.

Sounds too altitude limiting.., dragging the retrieve line and all.

Do have an electric motor and prop. These from deceased flying buddy.
Only have heavy NiCad packs from car/boat applications.

Would need latest LiPo battery packs, but do have modern smart charger to handle every battery chemistry.

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Old Jun 08, 2016, 03:57 PM
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I flew R/C sailplanes with both diesel and glow motors on pods in the 70's and 80's and enjoyed them very much. However, today it's a whole new ball game and the simplicity of electric power, either on pods or "winch-in-the -nose" is an order of magnitude more efficient than messing with diesel or glow.
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Old Jun 08, 2016, 08:31 PM
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Yes..., modern electric probably really is the only real choice to be made.

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Old Jun 08, 2016, 09:20 PM
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Don't forget cleaner. I fly electric sailplanes because I can't walk the distant for a high start either.
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Old Jun 08, 2016, 09:42 PM
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Hi, Sam,

There are inherently several hazards you may have to contend with.

* with a bottom pylon engine mount, you may have to start it with the plane upside down. Whether you hand start it or electric starter ignition, you may find yourself pushing hard or flipping hard to do the start. Depending on the model and how well built it is, you could crush the plane just trying to start it. And diesels have more compression

* once the engine starts, you have to flip it over....very hazardous with a running engine

* the launch: depending on how you hold the plane, you could have problem depending on the design and size of the motor pylon. fuel tank position would also be a problem. The engine may do well inverted, as long as the fuel pickup stays where the fuel is. BTW how do you hold the plane now?

* what do you do when you reach altitude and the engine won't stop? And if you dare to pull it off while the thing is still running....might have some serious untangling time to do.

Electric is the way to go. Modern power systems are powerful, lightweight, very easy to maintain and service , reliable and perform well. It is no secret that many electric models are just as light as their engine powered cousins and mondo strong . Their quiet systems make them perfect for use in the suburb fields. One man, one plane, a transmitter and a few battery packs makes for a morning of quiet fun. And, there is no oily, slimy mess on the plane.

Question: you are flying along in pure glide....no engine running and you hook a thermal. It carries you out and then turns to sink. No problem, just throttle up the electric model. But I'm afraid it may be the walk of shame for the diesel powered model. Are you convinced, yet?

Mike Lee
Fly RC Magazine
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Old Jun 08, 2016, 09:58 PM
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You could go old school and mount diesel on front of glider. Original Oly 650 showed this omn plans. Craft ait had Buttercup etc. Set prop on compression stoke and be out of the way. Ni-cads/ Fuel engines kinda out dated with new bl motors etc. Motor/ esc is about $40.00. Small 3 cell li-pos are cheap and on add all the time.
I know some will do it their way and thats fine, but in the end bl motor will smoke and fuel motor[engine].
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Old Jun 09, 2016, 09:15 AM
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Quote:
Originally Posted by ScratchBuildrSAM View Post
Would need latest LiPo battery packs, but do have modern smart charger to handle every battery chemistry.
Not hard to come by- hobbyking and rcfoam have suitable packs for under $20. Probably lots of other places, too.

Better or larger packs can be had for a bit more.
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