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Old Sep 25, 2015, 06:25 PM
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Power system for 2.4 mtr. span tug suggestions.

I'm currently looking at buying or building a powered model for aerotowing gliders. It will be around 2.4 mtr. span. Most likely a Piper Cub or a Piper Pawnee.
I'm still considering power options, both electric and internal combustion. In order to make that choice, I would like some suggestions for an electric power set up, including motor, battery (or batteries), prop size and charging requirements.
I have limited knowledge of electric powered aircraft and have only flown gliders to date.
So, basic information will be much appreciated.

Jim.
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Old Sep 26, 2015, 02:31 AM
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If you're building the model specifically for towing gliders, then fit a petrol engine. From experience, an electric tug is usually capable of three, maybe four tows per charge, so you'll be continuously changing and charging battery packs if you want to maintain a good launching rate. If you're building it as a sport/scale model that'll perform occasional towing duties, then electric can work quite well - it all depends on your requirements and expectations. If you want a detailed electric setup, then more model details are required, such as wing area, weight and maximum prop size.
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Old Sep 26, 2015, 04:35 AM
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Good points Gordon.
I am exploring the feasibility of converting a small four stroke petrol engine at the moment. The model has not been chosen yet, but will probably be either a Piper Cub or a Piper Pawnee. Around 2.4 mtr. span. Build (most likely) or buy.
Most advice I have received to date also is to use an internal combustion engine.
This project is still at conceptual stage, needless to say.
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Old Sep 27, 2015, 03:24 AM
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Jim - OK on that. Of the two models, I think I'd choose the Cub for towing. Whilst the Pawnee is less common and perhaps more attractive, it does present the problem of how to attach the towline. Most that I've come across use a tow release either side of fuselage with a bridle to attach the towline - more weight and complication which you really could do without.
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Old Sep 28, 2015, 05:49 AM
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High Wing Tug

Jim,

A high wing model for a tug is always the best option. The reason being is that because you tow from basically the C of G ( most times it is on the spar so you are that close to C of G that it doesn't matter). Think of it this way, if you were to suspend a model from the roof by the tug point on a piece of string, you would find that you can pretty much manouver your model where ever you want without interuption or affect on the model. The same goes when you are towing a glider. A glider can be above, below, at the side etc so you want that to have as little affect on the tug as you can get. So hopefully on a high wing plane the glider will have as little as possible affect on the flying of the tug. I hope that makes sense.
As with the Pawnee, yes they use a bridle connected to each side of fuse at the C of G location. I made this modification to my Pawnee as it's purpose when finished ( long term project) to use a a tug for my Kookaburra. You are welcome to come and inspect both my models( as I have one of each) to help in your decision making.
Andrew
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Old Jan 28, 2016, 10:56 AM
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I have the H9 33% Pawnee and it is a "towing machine"! I don't use any "bridle", the tow release is right behind the cockpit and works fantastic. DLE 111cc turning a Falcon 27x9W carbon fiber prop. Largest sailplane towed to date was just over 55 lbs with a 9M wingspan. I've got 300+ tows on the plane and it has performed flawlessly.
Marc
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Old Jan 28, 2016, 04:10 PM
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30% Klemm build thread.

Good to read your post Mark. Do you have pics or a dedicated thread? If so, please post here or over on my build thread.
I've started to build a low wing large scale model plane for towing too. I've abandoned the electric power option and will be using a 100 cc two stroke.

The build thread for the Klemm is here:

http://www.rcgroups.com/forums/showthread.php?t=2523079

The title of the thread is a bit misleading, the plan kind of morphed into something much bigger.
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Old Jan 30, 2016, 04:54 PM
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Hi
Look here for the "Gambitron" = very good aero tug (span 2.8m)
http://www.rcgroups.com/forums/showp...postcount=9705
Louis
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