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Has anyone tried making a catapault for GP Synapse?

Old 07-15-2008, 11:50 PM
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Merlin1959
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Default Has anyone tried making a catapault for GP Synapse?

...or other flying wing? I usually fly alone and am right handed so tossing this sparky gets a little hairy. Woul dbe nice to have a portable catapault that I could activate with my foot.

Thanks
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Old 07-16-2008, 01:01 AM
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FlyWheel
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I've toyed with the idea, sort of a miniature high-start about a meter or so long using latex tubing for thrust. A foot tredle to release the plane, hit the throttle once the prop is clear. But I never got around to it. All you have to do is get the plane above it's stall speed so even if it doesn't power up it'll just glide to earth a few feet beyond the launcher.
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Old 02-16-2011, 01:09 AM
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siginden
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Default Synapse hi-start

Has anyone used a hi-start to launch the Synapse edf? I just bought one of these at an auction. The seller had never flown it but he glued a hi-start hook on the bottom. In reading the various threads, it seems that stalling on hand launch is a major problem. Maybe a short hi-start would help. Thanks
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Old 02-16-2011, 01:21 AM
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Nitro Blast
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Originally Posted by siginden View Post
Has anyone used a hi-start to launch the Synapse edf? I just bought one of these at an auction. The seller had never flown it but he glued a hi-start hook on the bottom. In reading the various threads, it seems that stalling on hand launch is a major problem. Maybe a short hi-start would help. Thanks

I have one, and am afraid to launch it again, as launch #1 ended up in breaking the fan on the stalled hand-launch...

I have upgraded the motor and controller, so it should be fast, If I can ever get the cajones to try again!
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Old 02-16-2011, 01:48 AM
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siginden
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As i understand your comment, you tried a hi-start with the Synapse with bad luck. Could you please tell me how long the rubber tubing and the string is that you using? Did the hi start seem to cause too much drag to get enough altitude? Any information would be appreciated. I would like to try mine with a hi start considering all the problems people seem to have with hand launching. Thanks, siginden
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Old 02-16-2011, 01:57 AM
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tampaflyer
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you need to CATAPULT it . i can launch a 4.5 lb mig21 using 15ft of nylon and 10' of latex tubbing , pulled to 20-25lbs.

the placement of the hook will be the end of it if placed wrong.

high starts(gliders) are near the cg ..for max altitude gain.

tow rigs are on the nose for the plane to follow the tow plane.

the catapult needs to be ahead of the le about half way from the nose.
this will give you some nose up but more forward speed to get it to flying speed fast. the launch rails allow for a release point and some up attitude.

see my youtube for the mig21
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Old 03-01-2011, 03:30 AM
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FlyWheel
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Originally Posted by tampaflyer View Post
you need to CATAPULT it . i can launch a 4.5 lb mig21 using 15ft of nylon and 10' of latex tubbing , pulled to 20-25lbs.

the placement of the hook will be the end of it if placed wrong.

high starts(gliders) are near the cg ..for max altitude gain.

tow rigs are on the nose for the plane to follow the tow plane.

the catapult needs to be ahead of the le about half way from the nose.
this will give you some nose up but more forward speed to get it to flying speed fast. the launch rails allow for a release point and some up attitude.

see my youtube for the mig21
Ahead of the LE (leading edge)? That would put the hook in front of the plane in the case of a flying wig. You meant behind right?

And if so, halfway to what? Or is it halfway between the LE and what?

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Old 03-01-2011, 09:59 AM
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Larry3215
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hi-starts and tow cables are always attached at or very near the CG of the plane being towed - never on the nose or even very far from the cg.

If you attach too far ahead of the CG, the pilot will not be able to control the pitch during the launch. Its like having a very very nose heavy model while the launch is going on - which is generally bad news.

If you attach the cable at the nose of the plane you have almost zero elevator effectiveness while launching. Doesnt work very well at all.

If you attach the cable too far behind the CG, its like having a very tail heavy model during the launch - again with little to no control over pitch. Thats usually even worse news.

For the most part, the attachment point should fall somewhere within the CG range of the model and for safer launches its usually set just ahead of the cg by a smidge for starters. Then its fine tuned to get a balance between max altitude without going toooo steep or being un-controlled and better control but with less climb.

On a towed glider I like more control but not so much climb that you rise faster than the tow plane, so I set the tow hook further forward but it will still be near the CG.

Some folks like it up close to the nose but I dont like the lack of control with that placement.
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Old 03-13-2011, 12:00 AM
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siginden
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I saw a video on u-tube of a synapse catapulted. It looked like the hook was back at about the CG. It rose spectacularly on launch, but on release, it didn't have enough flying speed and immediately stalled and spun into the ground. From watching this, I'm of the opinion that the hook should be further forward to gain speed and not as much altitude. Sailplanes fly much slower, are much harder to stall and need altitude vs speed, so the CG hook placement seems reasonable for them, but an EDF, it would seem, should be further forward, as tampaflyer suggests.--Any comments?
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Old 03-13-2011, 01:36 AM
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iflyrc1012
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being right or left handed makes no difference. just launch it like in this video. if it CAN FLY, IT WILL.
i have launched everything from the lightest little wing to big heavy overpowered strykers, e.d.f.'s and everything in between using this launch toss.

[media]http://www.youtube.com/watch?v=UJJe7QLT0vE[/media]

if that don't work, then get a launch truck and a driver !!
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Old 03-13-2011, 09:33 AM
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Larry3215
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Originally Posted by siginden View Post
I saw a video on u-tube of a synapse catapulted. It looked like the hook was back at about the CG. It rose spectacularly on launch, but on release, it didn't have enough flying speed and immediately stalled and spun into the ground. From watching this, I'm of the opinion that the hook should be further forward to gain speed and not as much altitude. Sailplanes fly much slower, are much harder to stall and need altitude vs speed, so the CG hook placement seems reasonable for them, but an EDF, it would seem, should be further forward, as tampaflyer suggests.--Any comments?
It didnt stall because of the tow hook placement. The pilot just screwed up

Its also possible they didnt stretch the cable far enough to get up to speed fast.

Glider hi-start launches are usually milder/slower speed than what you would generally want for an edf. That has nothing to do with hook placement though.

Thats where a catapult would likely do better. Gets you up to flying speed faster.

I would also be carefull trim the plane for neutral elevator if I was going to do a hi-start - just because of that slow initial start. Then the pilot needs to be carefull to keep the nose down to be sure the model DOESNT climb to much and thus loose speed.

Tow hook position helps, but the pilot still hjas to fly the model from the moment it leaves his hand
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Old 03-13-2011, 06:36 PM
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iflyrc1012
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Larry makes a very important point about hi-starts and catapult launching.....
YOU GOTTA FLY THE PLANE!!!
alot of first time hi starts and cat launches are F.U.B.A.R. because the pilot just stands there waiting for the plane to release from the hook. as soon as the plane starts moving, you should be flyin it.. keeping the wings level, adjusting the rate of climb and throttle management. anyway it sounds harder than it really is.
JUST GO FLY AND HAVE FUN!!!!
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