Bicycle high start?

[Cubby Boy]

Has anyone ever used a strong legged friend on a bicycle to pull their glider up to a decent height?

Just thought I would check before I attempt it.

I have a 53" wing with 5.5 oz. loading with a servo tripped release just forward of the CG. I am going to hook it to my friend's bicycle with about 200 feet of strong (but light) kite string.

I think that he can accelerate to about 30 mph in about 20 seconds. I figured that this should give me enough ummphh to get the plane up about 150 feet.

What do you think?

[BMatthews]

You'll want some fairly stretchy line so your buddy can actually start riding to build up some tension for that critical first couple of seconds. Speed is an issue but constant tension is more critical. And it's hard as a bicyclist to build much tension at the start with a gear that is best for speed. Changing gears will help but with the standard derrailleur system the rider has to back off the pedaling force for a second or so to ease the shift and prevent damage to the chain. This will show up as a loss of tension about 70 feet up and about the time you've turned the corner from needing lots of tension to needing more speed to flip it off the top.

Oh, and if you're doing this on grass you can forget about the 30 mph speed. Unless he's a world class mountain bike racer the grass will slow him down to about 16 or 17 mph tops.

Good luck.

[Cubby Boy]

Good input.

I don't have a highstart and wanted to try it on-the-cheap.

I may give it a try and see what happens.

I will report back.

[William A]

Somewhere I read about a guy that used a pulley setup that doubled the tow line speed using 1 man power to pull on main line.

[Gliderguy]

F3J most often uses a pulley and two guys. The launch has enough power to fold all but the most sturdy planes. Might try one guy and a pulley and see how it works.

[Cubby Boy]

Is there a thread or web page that describes such a monster?

I would like to give it a try.

[kjw03]

Tent stake-$1.50

Key ring-$0.50

25 ft of 1/2" surgical tubing(home depot)-$23.50

300 yrd spool 40lb test fishing line-$6.99

Roll of red colored tape(streamer)-$2.99

Not having your buddy laugh at your brand new , perfectly fine glider make a weak attempt to get altitude then lawn dart straight into the ground from some crazy half ass attempt at launching it-priceless:D

[Steve Diebolt]

What kjw03 said! :D

Steve

[Miami Mike]

Originally posted by kjw03
25 ft of 1/2" surgical tubing(home depot)-$23.50On the way home from work today I stopped at a Home Depot and searched every aisle in the store. I found no trace of surgical tubing. Furthermore, I was too embarrassed to ask anyone there if they had it because I couldn't think of any reason that they should. If Home Depot does carry it, what department do they put it in and what do their customers normally use it for?

On the positive side, I did find a nice plastic reel made for long extension cords that I can use to wind up my high start, that is, if I can locate some surgical tubing to make it with.

[kjw03]

found the tubing next to the plumbing section where they have all the clear tubing for washing mach. drains, etc... or you could try a fishing gear supply store. Surgical tubing is usually available there too. By the way the 1/2" tubing was in little supply @ home depot but there is usually lots of 3/8" which I have used also-either way will get you up there cheap. Forget the bicycle.

k.

[Cubby Boy]

Ok, I will forget the bike, even though my buddy wants to give it a try. The lawn dart senerio is just too creepy!

Remember, I am new to High Start / Bungee launch and need some direction.

Again this is what I want to send up:

53" Blucor Zagnuts launch. 20 oz. Flying weight. 5.75 wing loading (about 500 Sq. inches). I have mounted a servo-tripped quick release just forward of the C.G.

I have plenty of room at the local flying field for launch. I want to get the thing up really high (and be able to do it by myself).

What do you suggest for materials? Remember, on the cheap!
What size and length of tubing, etc.

[William A]

http://www.hobby-lobby.com/histart.htm#Complete

[Bernie Wolfard]

Most gliders just have a rearward facing hook for the winch/tow/high start. The launch line has a metal ring at the end that fits slips over the hook. The hook is attached at the bottom of the glider just in front of the CG (actual location depends on glider, further aft higher launched but more chance of coming off on tow or getting rotating, further forward lower launches, less chance of coming off or rotating). When the glider gets to height it will overfly the towline and the ring slips off the hook. You don’t need a release mechanism and you don’t need or want the weight and complexity. You do need a strong hook well attached.

On a launch the glider at first climbs almost vertically. It’s speed will be much higher than the tow as it is describing a circle to the tow’s straight line. Stress is highest at this part of the launch. When the glider reaches the top of it’s climb towline resistance goes down and speed goes up. I think there should be no problem towing your glider up with a bicycle, as the pull will probably be less than 15 lbs and the speed is not that great. The biggest problem, as I see it, is the bicycle pulling too hard and pulling the guts out of your glider. The other is timing the launch to the bicycle pull. You want some stretch on the line before releasing the glider so once the bicycle starts to move be ready to commit. Give it a try with a long fairly light nylon line. Nylon stretches over 20% so it gives lots of “spring” to the line. Make sure you can communicate with the bike driver throughout the launch and that the bike has good brakes. Let us know how it works.

[kjw03]

enough with the bicycle- unless you just can help it and need to find out how much fun it really will be. I used twenty feet of 3/8" tubing and 50 yards of fishing line tied together via a key ring. Then at the end of the fishing line I used another key ring to hook on the glider tow hook. I put about a foot long piece of red tape on the line at the end to use as a streamer so my line would fall near me and be easy to see. This set up was under thirty dollars and could get my 18oz glider up 100-200ft easy-just pull real far. For just a liitle bit more $ I used about 50ft of slightly larger tubing(bought at fishing store) and about 100 yrds of line and launched a 40oz plane way up there-15 min flights no prob. It was all really easy and very cheap too. Worse part about it was winding up all the line,so I switched to electrics. I was too cheap to get a spool so I used a block of wood to wind it all up.


k.

[Cubby Boy]

Thanks. That is just the kind of info I was hoping for. What lb. test fishing line are we talking about?

Also, How far back do you streach it. I saw somewhere that the tension should be about 4 times the model's weight.

[Cubby Boy]

I bought the latex rubber and stuff today. Now I need a tow hook (my servo device doesn't work worth a sh*t)

I started a new thread asking how to make a tow hook.

Any thoughts?

http://www.rcgroups.com/forums/showthread.php?s=&threadid=114566

[Miami Mike]

Cubby Boy, a friend of mine and I are getting Zagi THL's soon so I hope you'll share anything else you learn about hi-start launching them.

[kjw03]

Cubby- A plant hanger works well as a tow hook.
It's a hook that you would normally srew into the ceiling and hang a plant from.(home depot,lowe's, fred meyer) Usually there is only a small section that is threaded and the rest is smooth. The hook does not need to be large in diameter to work well, get a hanger that you can bend with pliers and make it into an L shape. It only needs to protrude below the body 1/2" or so max. I would make a reinforcemnt plate of small thin plywood(or similiar) maybe 1" square or there about and screw the hook into it, then epoxy to fuse. Hook the keyring to it, pull back until there's good tension. The fishing line will stretch and you'll feel things get snug as you pull but you can go quite a ways without worrying about anything breaking. Just make sure you have good knots! Hold the ring as you pull,keep the plane level and let go once you feel the line is tight enough. It should go straight up then level off at the end of the line.Keep the plane straight while going up and you shouldn't need to work the elevator too much. If it doesn't unhook right away a small loop always did the trick for me. Miami Mike- a Zagi THL was my first high start victim and it worked awesome! I cut out a samll square in the body about 8" back from nose and epoxied the mount/hook assy. I only needed a small amount of tubing to sling it up there because it was so light. I tried using my bro's highstart with a parachute on the end and it kept shooting of the line before it got to height. The chute was not letting the line go as fast as the THL and once I switched to a small streamer I had no problems. That thing really shot up there!Good luck!
k.

[Steve Diebolt]

Cubby Boy,

I found this link. Looks like there is lots of good info here!

www.charlesriverrc.org/articles/zag...m#Tow%20Hook%20

Hope this helps,

Steve

[Miami Mike]

Originally posted by Steve Diebolt
Cubby Boy,

I found this link. Looks like there is lots of good info here!

www.charlesriverrc.org/articles/zag...m#Tow%20Hook%20Your link got corrupted. This one should work:

http://www.charlesriverrc.org/articles/zagithl/zagithl.htm

You're right, there is lots of good info there.

[procrastination inc]

*comes in with huge grin*

Yesterday, I hunted aound for surgical tubing to make a bungee (hi start for you non-english speakers :P)

$24 (AUD) per meter!

so I went to office works and bought a bag of No.64 rubber bands ($4)

WHOOSH. bungies are so much fun, no probs launching the wing at all. 3 mistakes high.

bungee materials

12 meters of doubled up linked rubberbands
~30 meters of heavy fishing line
A really big screw driver (my peg)
3 key rings
a shoelace
plastic self adhesive hook
a bright hair ribbon

This worked for my 400g 36" wing, launches to about 20 meters, maybe more, enough for some fun afterwork in the local park


Last edited by procrastination inc on Mar 11, 2003 at 10:18 AM

From here:http://www.rcgroups.com/forums/showthread.php?s=&threadid=98283&highlight=64+rubber+bands+self+adhesive+hook

[Cubby Boy]

I am going to make a tow hook out of wire today and fly by wednesday.

Is the tow hook positioned differently on a bungee launch than on a high start? Seems that the hook would be farther back on the highstart. If so, what is the placement rule (for the hook) for a bungee start?

[procrastination inc]

I stuck a plastic self adhesive cup hook about 7/8" infront of the CG.

Don't sweat on the placement too much, stick it on and try it out.

[Cubby Boy]

I tried out my new high start today!

50' of 3/8" latex tubing + 160 feet of heavy nylon string.

I stretched the line back about 80' and let-her-rip.

I think that I got my hook placed correctly, because the plane climbed pretty aggressively, although, not as high as I thought is would go.:(


I don't know if I have too much or too little of the nylon? :confused:

I will play around with the nylon length to see how it effects the launch characteristics.

[Miami Mike]

Originally posted by Cubby Boy
I will play around with the nylon length to see how it effects (sic) the launch characteristics.I figure there must be a formula somewhere that can tell us how to build an ideal hi-start, given the elastic properties of the material used, the weight of the plane, and so on. I picked up a couple of bags of #64 rubber bands to try the "procrastination inc" method with a Zagi THL, but I'd like to fine tune the lengths somehow. Any ideas?

[NickW]

Your average high start is one part tubing, and three parts line. So one hundred feet of tubing, and three hundred feet of line. I have to say I find this thread pretty funny. Rubber bands! :) now that cracks me up. Personally I bought a fully complete NSP Pinnacle high start for 50 US dollars or so. Nice and easy. But I just finished my winch, so I can now kiss high starts goodbye! But they are a fantastic learning tool, and take a lot of the pressure off of learning to fly, and learning how to use a winch at the same time. Good luck with yours!

Nick

[Ollie]

Miami Mike,

The best high starts are made with mandrel formed tubing rather than tubing formed by an extrusion process. This is because mandrel formed tubing stores more energy for a given tension than other types. This is because mandrel formed tubing can be stretched more without suffering. Tubing that is UV protected will last about four times longer than unprotected latex tubing. The best ratio of chord length to rubber length depends on the wind strength. The stronger the wind the more cord you can use for a given length of rubber. Three to one is a good ratio for no wind. About four to one works when the wind picks up to about the stall speed of the model or about 10 miles per hour. An extra length of chord you clip on with a snap swivvel on windy days is what I recommend. For best results the size of the tubing has to be matched to the weight of the plane. When the rubber is stretched to three times its relaxed length the tension on the line should be at least four or five times the weight of the plane.

For a source of the best rubber tubing see:
http://www.aerofoam.com/hosemonster.html

[John Gallagher]

Years ago I tried rubber bands and they worked for about three or four sessions. The rubber in rubber bands is not treated for resistance to sun exposure. It's surprising how fast the sun affects the rubber.

John

[leverick]

This thread is a crack-up. Ollie comes through with some more sage advice as always. OH, one last tip, with what ever tubing you end up with (assuming your using the tubing-line formula present above 3 ft of line to 1 foot of tubing) walk it out about to about 2.5 times the length of your tubing to launch the first few times. Then go to 3 times the length of the tubing when you have a few under your belt. If the wind is up you don't have to go 3 times the length. If you walk it out 100 feet on 50 feet of tubing with wind, you will see that the glider will actually travel staight up or even behind you as it climbs, DON"T panic!! Its just physics at work and the plane will eventually move forward....

OH ONE last thought, on the launch.... don't just let it go, give it a good hard toss level with the horizon, be sure to duck a little so it doesn't clip you in the ear!!.

CHEERS, Leverick

[black alder]

I presently use a bike winch to launch my 3 meter Mystery ship - weighing in excess of 85 oz. with no problem. great height , higher than high start. I don't have the weight of the rubber to lift into the sky

[RCheroske]

Do you use the bike winch to launch your own plane or do you have somebody else run the bike winch while you launch your plane?

[black alder]

When launching the larger sailplanes- 3 meters we use 1 guy on the bike winch and 1 to launch. the guy on the bike pre tensions the braided nylon line by peadaling and when the guy launching feels he has enough pull he lets the sailplane go. we have launched 2 meter with 1 guy on the bike only.

the guy on the bike has 1 hand on the rope you see him holding due to the fact that when he pedals and the launch is underway -if he didn't - the chair which he is sitting in- also pegged in the ground would push back. he also would need a hand for the sailplane- can only rest the transmitter

we find that in a fairly light wind you initially pedal fast- about 15 turns to pretension -and then maybe about 10 turns during launch.

You pedal at all times - when the sailplane will allow you- which is not very often. We find that when we have a good launch you cannot turn the pedals at all- just hold on a steady pressure.

we use about 1600 ft of line- 800 to the turnaround and on good launches only take in about 50-75 ft of line with a launch height of about 600- 700 ft.

[Kestrel]

Black Alder tuned me in to the bike winch idea a couple of years ago. I was unsure as to how it would perform. So, I kept my highstart. After getting the bike winch set up and making a few launches I decided to sell the highstart! It is a rather effective way to launch a model. Only a little more effort to set up than a highstart but will launch higher and is controllable and is less harsh on a weaker model. It is not a direct replacement for an elec. winch but is a lot less expensive and lighter.

I am gong to try to attach a pic of my version. I am able to launch my 3 meter by myself while sitting on the bike. I am sure that someone else may have a different idea as to how to set it up. But, this works for me and the price was right!

Ditto everything else that black Alder has said about launch height etc. It still amazes me how hard a 3 meter ship will pull on the line in a 12 or 15 mph breeze!!!!

[steelhead]

Good stuff, currently on topic in the threads. This one has a pic of the recumbant style bike winch I was looking for. Anyone seen the plans or want to share theirs?

Dean

[Thermalin]

Maybe a really really big hamster on a wheel for a winch setup would work. I did find a winch setup that used a coil spring setup similar to that in a rertactable tape measure but with much more pull... looked like a neat idea.

[jojoen]

In 2002 Nationals we had lots of fun in the evening with a bicycle "competition". I flew while the guys gave their best. I had an altimeter (Lolo) onboard and we used 200m to the turnaround. Best launch was 220m while most were in the 160-200m. The biggest problem was just after the zoom when the pedals suddenly got some speed again. There was some damage to some knees... :rolleyes:

Pictures here:
http://www.eurofoto.no/fotoalbum.php?aid=76886&portal_language=no_NO

Regards Jojo
www.grini.no

[Miami Mike]

Maybe a really really big hamster...A friend of mine and I plan to try towing a small handlaunch glider with one of those r/c cars.
http://www2.gpmd.com/imaget/d/tdtxd22.jpg
I figure they must be good for something.

[Majortomski]

I didn' see anyone answer the pully tow question. Works like this.

Stake the line into the ground. Pass it over a pully on the bike, or have your friend run with it. Run the line down wind to the glider. With your friend near the stake, pull the line out tight with the glider attached down wind from him, glider pointed into the wind. When your friend takes off running or riding into the wind, due to the geometry of the pully the glider will now be flying at twice the speed that your friend is moving. So in your origial post if he really can do 30 on grass, then the glider will be doing 60!