Aerotow Trainer Sailplanes

[ARUP]

Two Sig 'Riser' sailplane kits are being modified as aerotow trainers. Construction of the air frame is done with one. So far, it weighs 705g with two regulators, four Hitec 55 'Feather' servos, receiver battery and JR DS368 release servo. The fuselage of the second is finished. The other will get completed as soon as the first proves airworthy enough! The wings were 'straightened out' in lieu of the polyhedral design and strip ailerons were fashioned from the kit's TE. A retracting 'pin-in-slot' release was built into the nose. The tail feathers and wing tips were rounded... just for fun... and the rudder has pull-pull control. Spoilers were contemplated then dismissed because I wanted these to be very simple flyers... and I was lazy! Hopefully some interest will be generated when the 40 glow trainer tow plane and these are brought to the field and flights offered.





Thanks to Joespeeder in Michigan for the idea! He had a couple of small sailplanes for folks to try out at Frankenmuth. Wish me luck!

[JimD]

Absolutely great idea Mike. We did this back in 2010-2011 with an Easy Glider and a Telemaster 40 powered with an OS .52 4-stroke glow engine. Dozens and dozens of pilots had their first aerotow experience with it.

[edfmaniac]

Easy Glider is a great trainer and solid performer in light lift. I like those Risers too. Might take the air balance section of the rudder off though, or beef it up to prevent flutter on tow.

[ARUP]

Thanks for your concern! Hopefully, high speed towing will not be done so we can only hope flutter won't be an issue! The kit is designed with a rudder like this. I merely rounder the corners. At least the loads on the Hitec-55 'Feather' servo will be reduced. Hard points were added to the fin and stab so they can all be braced together in case a hard landing causes the fin to break loose. It is poorly designed IMHO. I 'doweled' the fin's LE to the bottom edge that is glued to the stab and have some large-ish gussets in there. Flight testing will commence as soon as nice weather arrives. It rained all weekend.

[Mark9]

Mike, I agree with Victor. Many of the early thermal ships had a balanced rudder and they were quite prone to flutter, even at normal flight loads. Eliminating the aerodynamic balance is one mod most do to eliminate the problem. Word is that the servos at the time were to weak and needed the help. Also, talking servo power the HS-55 is pretty small and may not be up to the task. Are they 100" or 2 meter? If they are the 100"er I would go with stronger servos on both flight functions the nose weight will be required anyway. Let us know how it goes. Great idea to get people involved.

[ARUP]

They are 2 meter airplanes. We'll try 'em out and see what happens! The tow plane is powered by an Enya 40 2 stroke that has a baffled piston so not a lot of power there!

[Joespeeder]

Hi Mike,

Cool project !

Thanks for the shout out. We've found trainer aerotow sailplanes very fun and interesting. Some things you'd expect and lots of surprises in getting lots of aerotow 1st timers into the air for their first tow.

Thanks to the Ka8's, we had 2 sport pilots that added balsa sailplanes to their fleet of rc aircraft for last years event. I know we generated interest in some of the DLG guys and I'm betting some will add an aerotow plane to their lineup from the exposure they got to aerotow at the event.

Plus, thanks to our event the Frankenmuth Aeromodelers have generated lots of interest in sailplanes in general and now are flying sailplanes on Wednesday mornings.

They have a group of guys that are learning to thermal and really enjoying the change from power. Electrics and winch launch mainly but if I could get up there I'm sure we'd do aerotow as needed.

I'm really a carpet bagger up there. They are very kind and excited to see the aerotow event grow each year.

Keep us updated on your progress and how the trainer works out.

Joe

[ARUP]

If they survive I'll bring 'em to Frankenmuth next year! That was fun!

[JimD]

Mike, when we were using the Easy Glider trainer, we found the HS-55 servos were plenty strong enough for the flight loads, but not the abuse of the landings (cartwheels, tree branches, etc.). They were replaced with HS-65HB servos and no more problems!!!

[ARUP]

Thanks, Jim! I have a bunch of these so when they get all busted up I'll replace them with the ones you mentioned. I plan to bring the extra 55s with me during any outings just for that purpose!!! I don't know how I ended up with so many of these 'Feathers'! Must have ten more in a box besides the ones I'm using for these two birds

[jswain]

What a great idea !!!

Not that its earthshaking but that it is a basic and quick (relatively) aerotowing solution to fun fly sailplanes or introduce existing flyers to something *non-competitive* oriented.

After seeing this thread i ordered a sig riser 100 kit and will make the modifications to have a tow release, ailerons, spoilers, undo the balanced rudder,
and round out the flying surface's tips just as seen above. Got to have the fixed wheel too - just have to........

To tow this Riser 100 locally ( and my just finished 1/4 scale hall cherokee) i have assembled all the bits and pieces to complete a stock H9 81" Ultra Stick.

No doubt i will take it to regular aerotows in 2019 with a buddy box for others to try.

john s. in so. calif.

[ARUP]

I toyed with the idea of a wheel and spoilers but decided to KISS! I'm keeping the rubber band-on wing just in case of a ground loop at take-off. I fully sheeted the 'D' tube. I reduced the dihedral in the main joiner. There is ample material in the kit for this. Way to go Sig! I love Sig! One sailplane has kit wing plan form which is double taper and the other has a straight LE root to tip. The first one with the double taper has a little built in wash out. The one with the straight LE shouldn't need it. I just laminated a bunch of spar joiner 1/64" strips to 'fit the bend' of the spars for the straight LE one if that makes sense.

The H9 Ultra Stick will have more than enough vitamins to pull the Riser!

[ARUP]

Joe- if the group build these it is really a simple matter to flatten the wing and cut ailerons from the supplied TEs. You might let them know RES polyhedral models can get towed but it's a little dicey! 'Full house' control is better.

[Joespeeder]

Thanks Mike, I'll ask about adding those changes. Gino is the one leading the charge up there and he's really happy to have more thermal hunters in the mix. I get the sense these are going to primarily to fly on their Glider Wednesdays. If it were me, I'd build mine as you described but it's a great 1st step either way. I bet we'll see a mix of props and winch launch set ups. If I can agitate Gino a little maybe we can get some aerotow Risers in the mix?? lol

[jswain]

Small update -11/12/2018.

the sig 100 kit showed up just fine last week and i am planning on starting on the H9 big ultra stick this week.

getting all the Stick power plane bits and parts was kind of a never ending shopping dirge as i hadn't done a non-glider power plane in donkey years.

the fundamentals of model e-power are already with me so i don't have to sweat that. fyi - why electric power ? have an unreasonable aversion
to IC motors after dealing snarling Cox TD engines as a kid and hacking my fingers to bits on those props - that nitro fuel still stings in my mind

building the riser kit will be a no-brainer so maybe the new two plane package and first tow flight will be done by Christmas time (.....2018....)

js

[Mark9]

Yeah, no goop to clean off afterwards either using electrons.

[lenb]

Alright!!!!
Looking forward to watching the progress.

[ARUP]

I'll second that... let the fun begin!

[ARUP]

Well... the Sig Riser #1 was had a successful maiden flight being towed by Stephane with his foam Carbon Cub at the MRCA Aerotow. It flies really good. Stephane was able to find some lift even while it was lightly raining on an overcast day! We flew it four(?) times. Now... to finish Sig Riser #2!

[ARUP]

I had my longest flight at Cumberland this past weekend of over 75 minutes flying the Sig Riser! The Riser flies great and the rudder never came off!!! I'm going to finish the other one and put spoilers on it... it needs 'em! So... if you are looking to try soaring 'on the cheap' then get a Sig Riser and consider these mods to the wing. For such an inexpensive kit it offers a wealth of fun flying!!!

BTW... tow was by a big Bidule with a DA180??? or some such engine this weekend. The Hitec 'Feather' servos are doing great service. The airframe can handle larger servos for peace of mind.

[ARUP]

Sig Riser #2 is completed airframe wise. It just needs the radio install. Riser #1 has double tapered outer panels and Riser #2 has a straight LE. A comparison can be made in the last picture. They are the same structure otherwise.







That's all for now!

[JimD]

This sure brings back memories...While you are mainly concentrating on the sailplane side, I was working more on the tow plane side. Here are two of the Telemaster 40 tow planes I built between 2007 and 2012:



The one in the rear was built in 2007 and had an OS .52 4-stroke glow engine. The one in the front had an electric motor running on a 4-cell LiPo. Performance was very similar between the two with these power systems.

The electric version was built from the newer Deluxe kit (still offered by the present owner of the Telemaster designs). The older glow model was built from the original kit design.



Our sailplane of choice was the Multiplex Easy Glider.



Tow release was fabricated from scrap DuBro pushrod. Worked very well, never had a problem with it on hundreds of tows.







Tow release servo operated the release pin through a bellcrank mechanism. Fabricated from piano wire for the axle and wheel collars to hold bellcrank in place.



Makes me want to build another Telemaster 40 toe plane!!!!

[DustinI]

JimD Those pictures are probably just what I'll need to figure out the tow release on my Tele40.

[DustinI]

ARUP You got me thinking about my Gentle Lady. It would be real simple to build an aerotow wing for it. Reading your descriptions and looking at the pictures, you eliminated the polyhedral and decreased the dihedral. Is this correct? How much dihedral do they have?

[ARUP]

Those Telemasters look great! It sure is fun putt-putting through the sky with those floaters!

Dustin- I eliminated the outer panel dihedral but kept the stock center wing joiner/dihedral angle. They really don't need the dihedral except to keep the models from catching a tip at take-off or landing. Also, I cut strip ailerons from the kit stock TE. They work just fine. I was lazy and 'didn't' but do put spoilers on that Gentle Lady! I was flying last Spring(or was it Summer?) and got caught in a boomer. It ended up being a 78' flight but at times it was at my limit of vision at '400 feet'. With a rubber band-on wing I couldn't do too much and was afraid of overspeeding if inverted to lose altitude.


Memory isn't good. I reduced some of the dihedral in the center by cutting the wing joiner a little.

[JoeN]

I built a L'Bird and a SkyBird with the polyhedral. The inner wing panel trailing edges were modified to allow for ailerons and flaps. Both planes were set up for aerotowing. The ailerons mix works great on towing and the flap mix is fantastic for glide path control on landing. This modification allowed me to keep the original glider and allow for aerotowing. Should work for the riser as well.

[ARUP]

Now that's a cool idea!