Electric glider tug

[Neil James]

Has anyone any experience of using an electric motor powered tug for towing gliders? We have a couple of petrol powered tugs but I’m looking to find something that can tow relatively small gliders - perhaps up to 3Kg - off a grass field without making a lot of noise! Are there any kits designed for electric power and are able to be converted to towing duties? What have other people designed or converted? 

[Frank Skilbeck]

3kg glider, well Ray Watts towed my old Pat Teakle HP18 with his 6s powered E Flite Cub fine, a bit leisurely but Ray is a very good Tug pilot, my HP18 is no more but I guess it was probably 4-5 kg in weight (3.8m wingspan).

 

We have built a Ghost Squadron Ampley and now we built the old Mike Trew Towrag and electrified that, this will tow more than a 3kg glider, but it runs off an 8s and pulls some 70 amps at full throttle, around 2Kw.

 

For a 3kg glider something like a Grand Tundra or the Multiplex Fun Cub XL would work well.

 

The only downside to an electric tug is the number of tows per charge, our Towrag gets around 3 tows on the 5,000 mah 8s battery.

 

Here's our Towrag in action just after we'd built it.

 

[Trevor]

From my (limited) experience, a 6s powered tug will tow a typical 1/5 scale glider comfortably but 1/4 scale can be a challenge. As mentioned, towing is a power-hungry operation so it pays to design the tug to accommodate the biggest batteries possible. My Spectre for example uses a single 6s 4000mah battery when flown as a sport aerobat but has provision to fit a second 6s x 4000mah battery on the cg (wired in parallel) for towing duties. This arrangement seems to work well.

 

https://www.bartonhewsons.uk/home/modelflying/sport/spectrediary.html
 

Trevor

[Frank Skilbeck]

Neil, I forgot to mention the other model we use as a tug is Seagull Maxilift with a Laser 150, much quieter than the 30cc petrol it had in it previously, if not quite the same umph. It would probably convert quite well to electric and batteries could either go in the tank bay (which has a removable hatch) or the toffee bomber compartment.

 

 

[steve 1]

Hi Neil, we are in the early stages of trying the tow glider thing, still learning for the tug pilot and me the glider pilot, we can see the tug needs to do a shallower climb to keep momentum as a couple of the tows have come to a stall, obviously once I realised/seen the tug was/had stalled I released from the tow. Steve

[Wookman]

A couple of observations.

I would be inclined to put the elevator servo the other way up and put the horn and linkage underneath. The tow line didn't catch but it will, most likely when the glider release fails and you need to drop the line from the tug!

I would have a small flag on the line near the glider to give a better visual confirmation of separation.

Basically it looks like you have got the hang of rather well.

[steve 1]

Thank you Wookman.

The tug pilot did make sure the line was on top of the servo and in theory the line should never be that low again, sods law says it will at some point. I have suggested perhaps some balsa or wire going from the tail plane to the top of the fin done on both sides at an angle so the line could pass over the fin if needed.

Steve

[Neil James]

Thanks guys, that was very useful. I found Sarik have a Towrag plan although they say the designer was  Keith Humber, or is Mike the builder? It also ticks all the right boxes with two wings and the third wheel at the back like it’s supposed to be but it might be a bit big for our purposes. The V-tail is a good design feature too.  Battery life shouldn’t be a big issue as there’s likely to be only a couple of gliders on site at a time and it won’t be asked to tow up my 1/4 scale Fox.
I like the fun cub which comes ready to tow and looks like fun to fly anyway so I’ll look into that and similar models. 
Thanks for the suggestions. 

[Frank Skilbeck]

Oops, my mistake it was Keith Humber, but it has towed our Mike Trew 1/5th scale T-21s