Power pod for gliders

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Stew
Posts: 495
Joined: 02 Mar 2018, 10:21
Location: Staindrop, Darlington.

Power pod for gliders

Post by Stew »

Hi all.

I'm after a bit of advice..
I have been given four FF towline gliders from the estate of the late Robin Kimber of SAM1066 and I'm after converting one of them to power assist and single channel RC. The rest will remain FF.
They are I believe 'Nordic' gliders, and most seem to be around at least 6' span or more. Beautifully built.
Can anyone advise on a power pod?
Designs?
Thrust Line?
Mounting?
Rudder size for effective RC?
Can such a design be sloped?
Will they operate off a bungee rather than a tow line?

I know very little about gliders!

If you need details, photos, measurements etc. I can supply all details.
I'm just looking for something to get it gently up to height for some relaxed gliding.

Any help gratefully received,

Stew.
Martin
Posts: 744
Joined: 16 Feb 2018, 14:11
Location: Warwickshire

Re: Power pod for gliders

Post by Martin »

Electric or IC power?

There are two main ways of doing it:

1. Saw off part of the nose, and mount the motor there. This is probably the best method if you don't intend to fly that particular model as a pure glider. You can always take the propeller off, if you just want to occasionally fly it as a 'pure' glider - say for slope soaring. The motor usually replaces the nose weight that is present in most gliders - so often it doesn't actually make the model any heavier - though if you're using battery power, the battery normally sits back closer to the c.g. position and does increase the weight of the model.

2. Fit some sort of pylon over the wing, so the motor is up above the centre of gravity. If the glider has removable wings, the 'power pod' can usually be made completely detachable - held on by wing bands, or by the wing-joiners for plug-on wings. This is the best method if you don't wish to alter the structure of the glider, and keep the glider streamlined when the power pod isn't fitted - but when it is fitted, it produces a lot more drag than the 'motor on nose' option, as well as making the model heavier (you still retain the glider's normal nose weight, so that it will still be balanced when the power pod is removed).

Providing the thrust is kept low, so that the model just gently climbs up to height, the thrust line doesn't matter very much - just point the motor straight ahead. Back when we used mainly glow motors, a 0.049 motor (0.8 cc) driving a 5 or 6 inch diameter propeller, was usually enough to allow gliders up to about 8 foot span to gently climb up to altitude.

If you want the glider to climb out more like a sports plane, then a bigger motor mounted high on a pylon above the wing does tend to push the nose down when power is first applied, but as the speed builds up (assuming the model doesn't flutter from overspeed) then they usually end up climbing anyway, and need down elevator to prevent them looping, even with the very high thrust line.

I've found that up-thrust and down-thrust on pylon power pods above the c.g. don't seem to make much difference - so I just point the motor straight ahead. For nose mounted motors, a bit of down-thrust normally tames any excessive climb, but unless you're overpowering the model making it more of a hotliner, again, a straight ahead position is fine.

Regarding rudder throw, you normally need less throw if the model is flying faster - but, you'll still want it to fly in glider mode, so keep the rudder and throw standard, and maybe switch in low rates when you're in powered mode. Again, if you're not overpowering the glider, you don't really need to worry about it.

You can use a bungee on most tow line models. A powerful bungee does put more stress on the model than a gentle hand tow - so may not be suitable for very lightly built gliders; but, of course, you can make a bungee set-up as gentle as you wish by varying the diameter and length of the bungee cord you use, and how much stretch you put into it.

Bungee launching is good fun, but a bit of a hassle to set up: you need a big open field with not many bushes, trees, thistles, or even long grass; also not many non-bungee fliers or members of the public present, because you tend to get in each other's way. Adding an electric motor, either in the nose, or on a power pod, is a lot less hassle - and you'll get more and longer flights.

Any gliders can be slope soared in the right conditions. For lightly-built single channel, tow line types, and especially free flight, you usually want very light winds. You also want a hill with a big landing area and not many obstructions (trees, rocks, etc.) Best to go along to some slopes when others are flying, and see what type of models they fly under different weather conditions.
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_AL_
Posts: 160
Joined: 17 Feb 2018, 01:09
Location: Sydney Australia

Re: Power pod for gliders

Post by _AL_ »

There is a simple pod on the Aeroflyte Aries that might suit what you are looking for.

https://outerzone.co.uk/plan_details.asp?ID=6275
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Phil_G
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Re: Power pod for gliders

Post by Phil_G »

Mines rough-&-ready but has its own rx and lipo so it can easily rubber-band to anything with no wires

Image
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Shaun
Posts: 1049
Joined: 15 Feb 2018, 21:49
Location: West Yorkshire

Re: Power pod for gliders

Post by Shaun »

I did the same thing as Phil when we had the mass Impala launch except used a long extension lead to the models Rx.

Works well.👍
Stew
Posts: 495
Joined: 02 Mar 2018, 10:21
Location: Staindrop, Darlington.

Re: Power pod for gliders

Post by Stew »

Thanks so much for the info and ideas guys. I really do appreciate that. Great stuff. I can get something built now.
Nick M
Posts: 92
Joined: 19 Dec 2018, 20:39
Location: Camberwell london

Re: Power pod for gliders

Post by Nick M »

One further suggestion

Mount the motor in the nose - but in a way that you can put on a hollowed out nose cone

That way if you take the prop off the glider looks as it would have

The way to do it is to extend the fuselage sides. Probably less aerodynamic but still far better than a pod
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tiptipflyer
Posts: 393
Joined: 16 Feb 2018, 22:49
Location: Germany

Re: Power pod for gliders

Post by tiptipflyer »

A picture of my reworked power pod for the Graupner Cirrus, Cumulus, K8b might be of interest for you.
I reworked it to look more like the real IC equiped power pod from the old days.
Flight test already done. Works great
I will improve other power pods in the future.
On 3S it climbs like powered by an old 2.5ccm OS, when using half power like my old Cirrus using an OS Pet.
AufsatzCirrus.JPG
AufsatzCirrus2.JPG
Frank
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Wayne_H
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Joined: 17 Feb 2018, 05:26
Location: Temora, NSW. Australia
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Re: Power pod for gliders

Post by Wayne_H »

Most realistic Frank, nicely done 👍

It appears that the e-motor (2212?) firewall mounts onto the dummy i.c.engine, such that the integral motor assembly can be removed by undoing the beam mounting bolts. Have I got that right?
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)
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tiptipflyer
Posts: 393
Joined: 16 Feb 2018, 22:49
Location: Germany

Re: Power pod for gliders

Post by tiptipflyer »

Yes Wayne that´s right, the e-motor is mounted to the dummy OS10 crankcase and the whole assembly is screwed to the alu beams and the fairing which hosts the ESC instead of the fuel tank.
It was the old version of the original Graupner power pod kit. It was on my first Cirrus almost 50 years ago.

Here is my next reworked power pod for smaller gliders, it uses a Cox PeeWee dummy and the 1306 e-motor mounted to it.
I use it on my Hegi Spassvogel. It will fit other small gliders as well.
SAM_4635.JPG
SAM_4637.JPG
Frank
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