Tow mechanical setup..

[Highfly]

I am working on a Seagull 2.1m Space Walker e-conversion to be used as tow plane. I have a Himax HC6332-230 running on 12S swinging a 19x8 prop. Test flights so far were uneventful with almost vertical performance at normal flight.

I am building the tow setup which is about 1” behind the CG and was wondering what kind of mechanical construction I should be investing in considering that I would like to tow sailplanes up to 4m. The way it is setup now, attached to the fuselage I can lift the fully loaded airplane by the tow pod and there are no signs of complains or funny cracking noises. However I am still concerned that I have missed something and would appreciate comments and critique before I start schlepping…

I have attached a few pictures and would appreciate some comments.

Thanks
MG

[Gunny]

Hello Highfly,
Welcome aboard RcAerortowing. There is a wealth of information all throughout this site ie. the forums and the main website. The main site has news and useful articles too.

I cant remember excactly where I read this, but "now-a-days" the tow release is mounted much closer to the wings trailing edge of the tow plane. There is a reason for this. In the 90's what you did (and what I did too) was the norm of having the release mechanisim just behind the CG. It's O.K. I still use my ZDZ 40cc powered tow plane with this set-up, but I do notice on heavier and dragier sailplanes that the tug wants to pitch upwards more. Like someone pulling on a pair of riens (sp) on a horses' head. By having it nearer to the T.E. the effect is not so great.

The other thing that mostly concerns me is the physical size of that release servo. The small gears, spines. servo arms and mounts used on a mini or micro servo is insufficient The tow release servo should be of standard "physical" size and have metal gears and a rating of at least 100 in/oz of tork. And I use strong metal gear servos on the elevator and rudder surfaces too... along with tail bracing wires all around the tail.

Final note that I have is that the tow release mount is very tall. I would add some gusset plates to spread out the side loads (that's when somthing goes array in towing). Kinda like the fore and aft gussets you have shown in your pictures.

Gunny

[Highfly]

Gunny thanks for your input. The location of the tow was chosen due to easy access as well as having more available meet to work with. I will take your advice and add some reinforcement to the sides as well.

The servo you were looking at has an holding torque of 8kg and is metal gear. The horn looks funny I know but I hope that it will do the job. All other servo's are digital metal gear with a 23kg holding torque. I hope the power system will do justice to the time I have put into it. I have almost 3Kw at WOT which should be sufficient I hope.

For the first couple of flights I have a Telemetry system build in that monitors temperatures, RPM, RX Volts, Amps, Watts, Speed, Altitude and ESC Volts. This should provide the performance data needed and keep my spotter busy.

Thanks!
MG

[Gunny]

Very good.
Put a light coating of oil on the release rod... Ask me how I know this. Well one day the darn thing rusted shut on me. On the first flight of the day I do (and always perform on tug and glider) a tow release check by connecting up the line and pulling about twice the weight of the heaviest sailplane being towed. In my case about 25 pounds.

Gunny