Control Line...With a Gasparin??!!!

[kpriddle]

Hello, everyone:

After I finished The Bug, I thought I'd try making a CO2-powered control line plane.  From the get-go, it wasn't a practical idea, but I thought...what the heck, has it ever been done before?  If the lines were short enough, I knew I'd surely be in for a thrill.  

As you can see, I settled on probably the most impractical design that I could have...a combat wing.  My only explanation is that it's an simple design.  I used EPS foam stiffened only longitudinally with a strip of bass wood.  Then the leading and trailing edges were quickly and roughly shaped to reduce drag.  As I would learn, this material can be somewhat difficult to work with.  

This evening, my brother and I went to the field to give it a try.  With no right thrust and no extra weight to the right wing, my brother [PiperCub49] flipped the prop and let it go.  This being my third control line flight ever and my first C/L build, I had higher hopes than expectations.  It porpoised a lot and I had trouble keeping the lines tight, but I still had blast for four or five good laps before the charge ran out and it ever-so-gently plopped in the grass.  Two more flights followed.  PC49 and I were ecstatic!  We couldn't believe what we were seeing: CO2 and control line...at the same time??!!  It was unique for sure and showed a lot of promise.

What you see in the pictures is the wing adjusted to fly with more stability and controlability.  In today's flights, I watched the elevator go full up and full down due to slacky lines and too much elevator throw.  I've since cut the elevator down 1/2" and added wing tip weight.  I will also add right thrust and bellcrank stops to limit the travel.  My CG is about 0.75" from the LE, and this may also be adjusted later on.  

Please forgive my long-windedness!  I'm just too excited to share it's story in brevity.  If I had video, I would definitely share it, so until a later date...


Wingspan: 23.5"
AUW: 38.9 grams
Motor: Gasparin GM-120 Twin
Control lines: Kevlar thread

Happy flyin',
KP

[lincoln]

Congrats on accomplishing something new. (although perhaps if you look really hard, someone did it 70 years ago???) As long as you're doing a combat design, how long a streamer can you tow? How long are the lines? What diameter? How long does it take to do a lap?

Maybe if it's too twitchy, a slow combat (is that the right name?) design might be a bit steadier?:

Control Line...With a Gasparin??!!!

[OZPAF]

Looks like like fun - congratulations. I would suggest that you add a skid or piece of foam under the nose to protect your expensive and nice motor.
Lincoln's advice to use a slow combat model configuration sounds good however if you stay with the wing then I would also suggest adding side thrust ( around 8-10deg right) as well as tip weight  to maintain tension and possibly sweep the lead outs back at the tip due to line drag and the low weight of your model.
It may also be advisable to keep the line spacing on your handle only slightly wider than the bell crank to reduce sensitivity and give more control power with low tension.
Good luck.
John

[Konrad]

Guys this is Fantastic!!

You might find some larger tanks here.
http://www.hobbyclub.com/index.php?cPath=120&osCsid=ca2c4b74caecb1870d3625faffd64945

I would change the bellcrank material to something other than balsa. I'd use the printed circuit board material from say Radio Shack . Or 1/32 plywood, but not balsa.

I too would put some out thrust, but more like 4° to 5° I also like to rake back the lead outs.

So where are you finding all these great CO₂ motors?  I have a 120 single and have been looking for a twin.

All the best,
Konrad

[GM]

Hi.

Well done! That looks really fun.

You might find that you get a better motor run if the tank is more upright and you are using a liquid charge. (Might depend also if you decide on doing aerobatics )
The kevlar lines are a good idea to reduce line drag. You might be able to find even thinner line at a fishing shop.

I believe some speed control line fliers used "groupers" to hold the lines close together to reduce drag further and some even used monoline. Probably not practical in this case though.

[danmellor]

Nice work but it has been done before! My friend Colin Hutchinson did CO2 CL ages ago! Still on his website, I think...

Cheers,

Dan.

[Timp]

Dan:  You sir are a steely eyed missile man, like they said in the right stuff.  For thinking and executing an idea
that is totally out of the box.  I am thinking of doing some micro CO2 RC stuff.  I can get almost 3 minutes out of
the motor runs on some of my Gasparins.  Build something real light with rudder and elevator, no speed controller
needed.  Could probably be really light for indoor RC.  What do you think, Dan?

Tim Pivonka

[kpriddle]

Thanks for the kind words.  Relative to internet history, I thought it was a rather genuine idea, but I had a feeling CO2 C/L had been tried before.  

As for the wing, it is already a plane of the past.  After making adjustments following the first few flights, I made the ignorant mistake of using a bellcrank that would give me less controlability (more throw) than than the first bellcrank.  After two crash landings, the motor mount came loose, and rather than fixing it, I decided to make a new plane...one more suited for the power system.  So...voila!...here is it.  

I took the simple plans from the Aeromaniacs website and modified them to my liking (http://www.aeromaniacs.com/Freeplans.htm).  The old combat wing weighed in at 39g while this weighs in at a far chunkier 57.3g.  I have thought about lightening it--drilling out the fuselage or drilling out the left wing then covering it or filling it with foam.  I'll wait until the first flight to see what it may need.


Konrad,

You're right.  I probably should make the bellcrank out of a different material, but it is plenty strong and only weights about 0.3 grams.

As for the tank size, I really should be using a larger tank.  Has anyone ordered from HobbyClub before?

I bought this twin from a gentleman on RCG for about $70 shipped.  You really just have to keep an eye out.  My Cox .020 w/ Davis Diesel conversion head was found on the auction site for about $55.  My second motor, the G-24 was stolen from the auction site because it was misnamed.  It sold for $25 in only the nose of an old plane.  I snagged a Brown CO2 a week ago without the capsule holder for $10.24 shipped.  Believe me, I fly on a budget...but I've still caught the illness!;)  


GM,

I am using the same kevlar lines on this new plane and to be honest, they're a pain.  The line is made of many strands that aren't wound, so they tend to hang up on everything (even microscopic wood splinters) and frazzle and break.  I've considered using something like this 2 pound .005"/.127mm fishing line (http://www.basspro.com/Berkley-Trilene-XL-Smooth-Casting-Line-110-Yards/product/10206478/).  What do you say?


Dan,

Do you happen to have a link?  I'd love to see your friend's work--probably far more impressive...

Do you know of any more effective (lighter, more efficient) props for this motor?  It's running a 7X? right now, but it just feels like a paddle wheel.  It just doesn't produce the thrust I'd expect it to with that steep pitch.


Happy flying,
KP
 
P.S. Wingtip weight still needs to be added.  And...yes, I should probably trim that bolt.

[Konrad]

...
As for the tank size, I really should be using a larger tank.  Has anyone ordered from HobbyClub before?
...

Alberto has been good to me in the past. But I haven't ordered anything from him in about 5 years. He is my dealer for the Actro line of motors.

[Robmoff]

I am using the same kevlar lines on this new plane and to be honest, they're a pain.  The line is made of many strands that aren't wound, so they tend to hang up on everything (even microscopic wood splinters) and frazzle and break.  I've considered using something like this 2 pound .005"/.127mm fishing line (http://www.basspro.com/Berkley-Trilene-XL-Smooth-Casting-Line-110-Yards/product/10206478/).  What do you say?

You could try Spiderwire, sounds promising. See:- http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=2814.0
No good for me, I need something to carry a few currants!

Rob

[danmellor]

http://homepage.ntlworld.com/colin.hutchinson/index.html The control line CO2 is in the FF CO2 section, I think!

Cheers,

Dan.

[FreeFlightModeller]

I saw this when Colin gave a demo at Impington a few years back ...great stuff 

[danmellor]

Regarding props, the supplied 7" is a good match for the 120. I've used smaller Williams props in smaller, lighter models with the 120 but it's hard to find anything better for the 120.

Cheers,

Dan.

[kpriddle]

Dan,

I've been through that site about five times now and I've never noticed that.  It sounds like he had some similar surprised as I...mainly that it flew!  I'm sure he made less silly mistakes than I did in building.  Maybe this next design will be more successful.  

Because it has been raining and I'll be leaving for a trip soon, it'll have to wait until Tuesday at the soonest for maiden.

KP

[kpriddle]

Here's a video of one of the eight or so flights made on the evening of the maiden.  It flew well with the addition of wingtip weight and a small vertical stab.  From the looks of the plane in flight, it could use less wingtip weight.  

As previously stated, I will have to buy a larger tank to increase flight times.  At the moment, I think I have a 5cc-6cc tank.  Does that look right?  Might anyone have recommendations for the new tank size?

https://vimeo.com/68821020 (Password is CL)

Happy flyin',
KP