Newbie Tow plane assistance , what do i need next ?

[killowatt]

Ok I got bit by the Aerotowing bug and now I'm having fun again when i fly . It started accidentaly with a Fun cub and some cheapo fox glider . Now a few of the wiser fellows at our club are bringing out some great looking large gliders looking for a tow . I took our club trainer removed the .46 slimer and added a potent 50-55 670kv on 5s swinging a 13x7 zoar at 55a roughly 1k watts and fashioned a release ( which i found here thank you ) The trainer has dragged up all sorts of foam gliders with out a hitch .
The guy at the field whom infected me with the bug brought out a seagull ka-8b with an 118" wing and roughly 7 lbs and was looking for a tow . We towed it up with the "trainer that could" it was a bit of a battle but she got em up . The trainer does run out of steam well short of what i would assume would be a full pull . I guess what i am looking for is some info on how much tow plane is needed for how much glider . There is a bunch of guys re-fitting their birds looking to get them airborne again and I would love to oblige them . I was thinking of a senior telemaster plus with a power 110 on 8s . Any ideas on how big of a bird i could tow with that ? Any help would be much appreciated .

[JimD]

Killowatt,

Here are some stats on what an 8s setup can do. Our plane is a 2M TopModel Pilatus Porter with an AXI 4130/16 motor, Castle ICE 100esc, APC 15x8E prop, and (2) 5000mAh 4s Lipo packs in series (we did this so we could use our existing FMA CellPro 4s chargers).

Last week, we got to do some testing of the flight times and battery duration. A buddy was flying his Easy Glider Pro and I was doing the towing with the 2M Porter. We did seven tows to a good altitude, slightly higher than the average we do with our glow powered Telemaster 40.

Each tow cycle took about three minutes with the throttle up time being about 30 seconds of full-throttle on tow and about 15 seconds of partial throttle use to land and taxi to the start position. At the completion of the seven tows, the throttle up timer on my transmitter read 6:15 and the total flight timer read 18:45. (I set one timer on my Futaba 10C transmitter to start counting when the throttle stick is above 7%, the second timer counts from the time I turn on the transmitter)

After the flight test, the packs were placed on two CellPro 4S chargers and the pack capacity used measured 70% of each pack (very symmetrical). This means we use 10% (500mAh) of the pack capacity per tow.

My estimation of MA used based on a 5000MA battery and 70% useage (according to the CellPro 4S charger) was 3500MA. According to the data log, it was more like 2700MA. The difference can be accounted for by the fact that the batteries probably are less than 5000MA to start and that the CellPro does not use completely discharged to 0MA as the base (probably more like 500MA). So, if you take 200MA off the top and 500MA off the bottom:

5000 x 70% = 3500 - 200 = 3300 -500 = 2700 and that matched the data log!

It was a hot (temps in the 90's) and humid day with almost no breeze. These times would probably be better on a cooler day with a little breeze. The climb to altitude would be quicker and the motor run time per tow would be less.

And interesting note, the motor packs were barely warm after the seven successive tows, very nice for such a hot day. This is confirmed on the graph that shows the esc temperature, not much wormer than the air temperature.






As you follow the graph from left to right, you can track my throttle inputs for each of the seven tows. There is a little blip to taxi forward to tighten the tow line, then full throttle to takeoff and tow to altitude, then throttle off for the decent, and finally, a little blip of throttle to land and taxi to the start position for another tow.

Think of the graph in terms of what the use of throttle does to the motor and battery variables. Very interesting stuff!

Anyway, I have towed a sailplane about the size and weight of the Ka8 you mentioned with no problem. This motor on a Sr. Telemaster would be better because the 2M Porter is very heavy and has a high wing loading. The Sr. Telemaster with its high lift wing/stab and light wing loading would be much more efficient.

Jim

[JimD]

Killowatt,

There is a good article in R/C Soaring Digest about towing with an electric conversion of a Sr. Telemaster that Alex (aka IFlyTailies) wrote. Open the pdf file and the article starts on page 35.

http://www.rcsoaringdigest.com/pdfs/...SD-2009-04.pdf


If you are looking for massive electric power on a budget and 10s lipo (you already have the 5s packs just put two in series) consider the GreatPlanes Rimfire 50cc motor.

Check this thread for more info:

http://www.rcaerotowing.com/forum/sh...nd-experiences

Jim

[JimD]

Ok I got bit by the Aerotowing bug... It started accidentaly with a Fun cub and some cheapo fox glider... Any help would be much appreciated .

By the way, sorry about the nasty infection!

There is no known cure...but, the symtoms can be temporarily relieved by routine purchases of larger tow planes and sailplanes...mean time, it is best to join a support group...so, we are here for you!

[Len]

Welcome to the group, Stand Up, state your name and clearly admit you are an alcoh....... oops, I mean Gliderholic.

That seems to be the way it happens.
Where are you located?

LEN

[killowatt]

Thanks for the input ! I am located just south of Raleigh N.C. I must admit I was a typical power pilot and had little interest in gliders . Then one day I arrived at our club and found 2 guys trying to tow a fox glider with a fun cub . The two pilots just did not seem to click and towing wasn't going very well , so what the heck I offered my assistance . We got lucky and we specked the cub and glider several times . Then it happened , I got bit ! The glider pilot and I swapped transmitters and I got my first taste of soaring ! !

[killowatt]

And I like it

[Charlie]

Hey KW,

Charlie from the SKSS here in Delaware
When I tow with electric I use the Rimfire 50cc on 12s
Lots of power, It will tow an Easyglider up to a 6 m Ventus
I use a Hanger 9 1/4 scale cub , Tele would work well also with this setup
22 / 10 Zinger

You and your fellow enthusiast's should make the trip to the SKSS Great American Aerotow 3rd week in August
Jim and Dave will be there doing their Easyglider Aerotow training

We will also attempt to break the foam glider record with 12 going up at one time

It's a great show
We have a Saturday Evening crab feast and BBQ

Also some full scale there at the field

There will be a ton to see and learn
Stick close to Len and next thing you know your flying his majestic Arcus or Nimbus

Glad to have you aboard
Enjoy the ride

Charlie

[louierc]

Kilowatt - I am also located 1 hr. south of Raleigh in Southern Pines. I have several sailplanes and an electric tug. Give me a call sometime and we will see if we can get together. Louie 910-695-8896.