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Getting back into RC sailplanes, and have noticed on several planes notations about a sling shot launch. I know what a high start or bungee launch is, but not what a sling shot launch is. Also noticed that the tow hook placement on the plans is not where I am use to seeing the tow hook for a high start launch. The sling shot tow hook is placed much farther forward. So what is a sling shot launch?

cfircav8r

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Not sure about it's use in gliders, but for smaller EDF's it is used for T/O due to the lower thrust to weight ratio. The ones I have seen are just like they sound, you stake both ends down perpendicular to the wind and use it lke a sling shot. The more forward placement is due to the fact that you are only using it to gain forward speed, and the climb is started after you have released. I don't see how this would be effective with a sailplane, but it is new to me also. Were these thermal gliders or slope gliders, and were they foreign made and maybe missused the term?

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The one plane that comes to mind is the ArtHobby Colibri which I just got. .On the plans is a note about the tow hook and slingshot launching. Another is the 39 inch Merlin which I want to fly as a a sailplane. when I wrote to the company about tow hook placement. I did not motorize it and was trying to figure out the company said that it could be flown as a straight sailplane. There is no place to put a tow hook, the place where a hook would have gone is the battery door for the motor. I have seen the sling shot method in the write ups on other gliders, and they all were smaller, handlaunch aircraft. So what you wrote makes sense. Thanks for the information. Now I have something new to try.

aeajr

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I know of sling luanched gliders that are very small, not RC.

I think people are talking about short bungee launches, also called zip start launches.

gliderguy100

You mention that you've seen the reference to sling shot launch on several planes.  It might be helpful to get a qualified response if we knew what planes yuo've seen this on.  I've been flying RC gliders for 30 years and have never heard the term "sling shot launch".  I use a power winch and I use high starts.  With both I sometimes perform what I've known as a "Zoom Launch".  Basically the way I do it is to first play the launch for as much altitude as I can get (pulling as much "up" as possible without unhooking or stalling out or ripping off the wings) then I flattenout the ascent and play the cord for as much forward speed as I can get out of it.  When I unhook it  "zooms" away.  I find this to be particularly helpfull on days with little thermal action.  It helps to get more range to sniff them out.  But I still use the standard hook location just beneath the CG.  

The comments about sling shot launch relating to small free-flight gliders makes sense to me.  I've seen some small gliders I've known as "chuck gliders" and other similar models (there are literally as many designs as you can imagine) and I've seen some that use a small hand-held launcher that resembles a sort of sling shot except it's more like a handle with a rubber band on it.  Shoots small gliders very fast.  Those definately use a forward hook location.

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I know what you are saying. It makes sense since I have seen these same things, but as an examply on the planms for my ArtHobby Colibri, there is a box that refers to a cross section on the fuselage and that that is where the hook is suppose to go for "slingshot" launching. Since I have not been in the hobby for quite awhile I thught I was seeing new terminology for a new procedure. Thanks for your help.

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I know what you are writing about with high starts, winches and zoom launches. I just got an ArtHobby Colibri ansd there are on the plans are a reference to sling shot launches and the fuselage cross section where the hook is suppose to go. I have always used high starts on my launches, and now I was seeing new terminology and a different palcement for the tow hook. So I thought I would ask. Also on my Multiplex Merlin when I asked the compnay about placement of the tow hook the email referred to a forward placement and a slingshot launch. Both planes are in the 40 inch wingpsan category. I remember sling shot gliders from when i was a kid. Yes they were free flights, but I just could not see how that applied to launching a small r/c glider. So since I have been out of touch for a long time with r/c sailpanes. I thought i would ask.
Thanks for your information, I appreciate it.

rcuname234

What would you like to know about the launches exactly? Iam sure I can help you...

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I am trying to find out what a sling shot launch is. I know what high starts and winches are because I have used them. As example on my ArtHobby Colibri there in the middle of the plans is a cross section reference of the fuselage with the notation that this where the tow hook goes for a sling shot launch. That spot is way ahead of the CG and not where I would expect it for a hight start launch. I have seen this refrence to a sling shot launch on other HLG sailplanes. Also on the Multiplex Merlin I bought I am not putting a motor in it and when I asked a representative about tow hook placement I got the same reference to a sling shot launch and tow hook placement. Some people have suggested that a sling shot launch is just that, a small bungee stretched between two anchor points. I hook the plane up and back up a bit and then just let go. The idea being to gain speed and not altitude. It was also suggested that a sling shot launch is just a modified high start launch, again with a short bungee and an attempt to gain speed and not height. So what is a sling shot launch, a friend, a retired airline/navy pilot, has a suggestion but the aircraft carrier is to big for my flying area.

rcuname234

The only thing youll be wanting to do is the following. You will use only one stake and place it in the ground followed by rubber tubing. Then youll want 7ft of line at the end of the rubber tubing. Attach glider and pull back and launch with one click of up trim. Youll gain speed that will be used to gain much altitude. Your glider will coast a good ways up.

Tips

You dont want the hook in the very end of the nose. It will fly too low during launch and will be unsafe. This method is hard to use on ships without ailerons. This method works on most any size glider. Mine is over 2 meters at 80 ounces and does well. Ihave videos of it on youtube. I call it catapult of bungee launch on youtube.

This can make things flutter and do damage if part are not stiff. Do pull back too far.

This saves more time than using a full length highstart. Its all I ever use.

gliderguy100

Funny thing about the english language, and it's use in hobbies liike this specially.  Words can have many different meanings.  I get the impression that this "sling shot launch" is an idea more than a specific technical thing. 

Everything rcuname234 says sounds right to me.  I've never heard the specific term "sling shot launch" before this discussion string but it sure does sound like he nailed it.  And his caution about doing damage if you pull back too far (gives too much speed) is GOLDEN.  Not all gliders are built for speed so would not necessarily be good candidates for this kind of treatment.  Guessing that if the Colibri plans refer to it then it must be suitable.  I would not try this with a lightweight floater like a Gentle Lady for example.  You'll need good penetration to take advantage of the speed that is generated.  If the plane isnt' designed for speed (but it still survises the sling shot) it will simply loose the speed very quidkly due to drag before you gain the altitutde that is (in my mind) the primary objective when launching a glider.  234's other comment about the tow hook NOT being at the nose is solid advice.  Heed that advice and follow the plans recommendation.

Additionally I would offer that if you want good long duration flights you'll want a good launch altitude.  A short stretch speed launch "saving time" is O.K. if you plan to make a hundred short flights.  You save time between flights by not walking so far to retrieve the line.  But if you want those long duration thermal flights you'll likely do better with a (longer) highstart or winch to get that altitude so you have time to seek out those thermals before you have to re-hook and do it all over again, and again, and again....  Know what I mean?  After all the idea of being out at the flying site is allabout flying, not walking.  Where I do most of my flying is flat land, thermals.  I have routinely had better results hitting thermal action with a higher launch derived from the winch.  When I use the highstart I just can't get as high.  I generally try to set the winch with 1,000 feet to the turn around.  Im sure I'm getting well in excess of 500 feet at the release.   And with practice you can still get the "Zoom" just before the release so you have both altitude AND speed once you unhook.

Now I'm getting all jazzed up to get out there and start the new season..............

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Thanks for the reply. I think you are right about what a slingshot launch is. I live in flat land and used a long high start for my launches, a cornfield is right across my my lane and this is what i am use. I would really haul my old Paragon up in the air using a releaseable tow hook. All of the new terminology uis overwhelming, and as to lauggage I love crossword puzzles and can see how flexibl;e launage can be. So tonight a short bit of bungee cord and a little fishing line and I will see what happens.

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Makes sense, I am trying this tonight.

Thnaks for the help.

gliderguy100

So how did it go? 

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I did not get the chance. The rain moived in and now it is here to stay for awhile. My fields are all muddy right now.

gliderguy100

Ah yes, the wonders of March.  Well I will be watching for a follow-up report whenever that happens so please do post.  thanks.

GBR2

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You should call Andre at Art Hobby and talk to him about the sling shot launch. A friend of mine just built his Bobolink and was also puzzled by the slingshot launch thing. He ended up building one after talking to Andre and he is extremely please with it. Basically it whips the plane to a very high speed in a short amount of time, once off the launcher he just pulls elevator and gets extremely high launches. I believe he used 3/8" surgical tubing but I'm not sure of the length he used. He only put loops on either end made from the pull pull cables used in RC planes (from Sullivan I believe). Here are some pictures Andre sent him:

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I should have thought of that in the beginning. Thanks for the photos, now this makes things very clear. I have the extra tubing so I will make my own now.
Thanks again.

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I made a sling shot set as suggested by one of the other posters. I used tubing from a high start I got with my Fling HLG and weed wacker nylon cord for the loops. It worked and it did not. I got lots of altitude, about 30 feet, but I could not not the loop to slide off of the tow hook. I had to zooom up and stall to get the loop off. I lost my height and speed. I am going to install a steel ring since I think the nylon loop is sticking. I am also going to use a different glider, one where the tow hook is very far forward. That airplane will want to go straight ahead rather than zoom up. Anway it works, I just have to fine tune it. The only downside is that the tubing lands up by the anchor rather than drifintg back to you like a high start parachute. Oh well.