Aerotowing a Sinbad? Rudder and Elev only?

[SteveNeill]

On Facebook this has been a great source of controversy. Can you Tow a rudder and elevator sailplane successfully? Many said it would be a disaster. Others said they towed Gentle Ladies and it was easy.

I recently built from a short kit this 94 inch span Sinbad. She's 3.2 pounds FUW. She hasn't been flown yet most of the places I could slope her were burned in the fires so I haven't maidened the plane yet.

I'm going to Vasillia this Dec for my first towing ever with the K-8 3 meter but I added a tow release to the Sinbad and was planning to bring it too. As I understand it if the tow is at a lower speed I should be fine.

Thoughts?

[SteveNeill]

This was posted for me as an example. Rudder and elevator plane. https://www.youtube.com/watch?time_c...&v=CUhQc6ErzxE

[ARUP]

Try it and just remember to have an itchy trigger... er... release finger!
I have seen polyhedral models towed successfully and I've seen one crash on tow. I don't know why the modeler or model didn't release. That's why I recommend that the release be the best part of your model! Have fun!

[SteveNeill]

Thanks Michael!

[lenb]

It'll work.

ONCE.

Take video ...



Ok, in all seriousness, it has been done, both successful and other times a disaster.
We watched a Gentle Lady self destruct on tow a few years ago at an event in Cumberland, event though many guys warned against it.

In the right conditions and the right tow pilot/plane combo it can be accomplished, however line it up and do it 5 times in a row without an issue and you'll prove us wrong. Since most of us get into aerotowing to enjoy the hobby and not really risk a plane, you won't see any rudder elevator only sailplanes on the flight lines of major aerotoew events. Why? It's not a question of if it will ball itself up, its a matter of when.
Even the most successful sailplane pilots will occasionally have an issue on a given tow when a wing touches the grass and drags, and that's WITH AILERONS. So take away the ailerons and insert a rudder, which simply induces yaw, which then results in roll usually much too late on a tow.

If you decide to risk the plane, insist on a slower tug that can lift off at slow speeds. Since the tug pilot needs to get the tug in the air to tow you, the takeoff roll is quite brisk and thats where the problem comes in for the sailplane. And remember,, less control is more.

What's the bottom line?
Sure, it may work. You'ill be successful a few times, maybe. But eventually you'll get bit and the plane will be destroyed. Its a shame, I saw the photos and its beautiful.

Why not save it for the bungee launch?

Good luck, be careful and take video...

That's my 2 cents.
Change please.......

LEN

[Mark9]

I've not had the aerotow experience base to build on, but both Michael and Len speak wisely. The method a rudder elevator only aircraft uses to turn, as Len describes, takes too long to react to a errant dropped tip. That is also one reason why many high performance slope gliders are aileron elevator only aircraft. At flying speeds roll and pitch control can work quite well, if precision and quick roll response is required. It too is the same reason aileron competition gliders took over rapidly and they had to give RES gliders their own class. Don't let your verve as a newbie drive you to make unwise decisions.

[SteveNeill]

Thank you gentlemen. High starts give me the willies enough. She's a sloper then..

[Mark9]

High starts work very well when the airplane is set up correctly and I leaves the throwers hand at the correct angle with flying speed.

[Stew2]

My plan to launch the 96" Sinbad I have to build is an F3J style manual tow. I have flown many 40" SIG Sinbad free flight gliders off of the a straight hand tow with the dorsal fin on the tow rig that compensates for the trimmed in turn. This will be done at Cumberland one day, soon..... You can't beat the smell of freshly doped wings!!

[Mark9]

Yeah, I wondered why my painting degraded the longer I painted using dope as a young boy. I now wonder how many brain cells I killed doing it.

[ARUP]

'Rejuvenator' on the doped surfaces will bring it back to 'like new'!

[SteveNeill]

Sounds scary to me. I'll keep mine on the slope.
But I do like the smell of the Dope. That's why I'm building Free Flight planes again. Working on a 45 inch span Wakefield now. Oh the simple days.

[JimD]

My experience with aerotowing goes way back to 1976 and it started with polyhedral RES sailplanes typical of the time. We used wing tip runners to keep the wings level until both tow plane and sailplane were moving. By doing this, we mostly avoided disasters at the beginning of a tow. Once in the air, the sailplane pilot had to resist using any more than the slightest control input or it would start a "Dutch Roll" event that would quickly go very bad. The sailplane needed to have a servo driven release and the sailplane pilot had to be quick on the trigger if the slightest issue occurred.

Mostly turning was out of the question. What altitude you could get going straight ahead was it. That didn't stop us from trying to turn, and occasionally we could get through a 180 degree turn. Usually, the sailplane would need to release mid-turn with things going bad fast.

Even though I was game to do it, having the only tow plane available, most sailplane pilots found high start launching much safer and less nerve wracking. Also, most did not want to install a tow release requiring an extra servo.

Here is one of our launches (circa 1976), I am the tow pilot second from the left. You can see the two wing tip runners down the field and both the sailplane and tow plane just getting airborne.

[ARUP]

What a great picture! It is a perfect example how friends interact within the aerotowing community!

[SteveNeill]

Jim thanks so much for your input. The Sinbad is a beauty and never flown as of yet. I'm planning a visit to the slope soon to fly the plane. I might invest in a high start to for upcoming events.
Who carries a good high start within our group or should I make one? I always prefer to support our vendors here when I can.

[lenb]

Check with Jeremy at the Model Box

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