Launch cart for flying wing

[clolson]

Just curious if anyone has any experience or suggestions here.

I have custody of a 7.5' wing span flying wing that I've mentioned in other threads:

http://youtube.com/watch?v=xChvYP6Xr-A

I got this crazy idea to build a launch cart for it so I could fly it by myself off land without needing an assistant to throw it, or a fancy catapult (which takes two people right now to cock anyway.) My goal is to have something that can support the wing while it accelerates to flying speed and then pull back on the stick (or maybe release negative elevator) and the thing will fly away leaving the cart on the ground.

One of the things in the back of my head is that I'd like to try loading it up with more batteries or other payload which makes something that's already a bit tricky to hand toss, just that much harder if you add 2-3-5 lbs more payload.

I've got a plan and have even starting cutting wood, but before I get too far down this path, has anyone here done anything like this before and have any tips or suggestions or things to watch out for?

Thanks,

Curt.

[lvspark]

A winglauncher sized for your craft would be easy to handle and simple to make..
http://winglauncher.com/picsnflics.htm

[sim559]

HI
I think you have more of a landing problem then launching.
rubber band launch is the way to go.

[clolson]

For what it's worth, I'm not 100% happy with the results, but I did get my launcher to work on the 2nd try. The biggest limitation is that my wing is a bit underpowered to plow through grass, but she eventually bounced airborne and kept flying.

[Unterhausen]

Curt,
that looks nice, let's see some movies.

[clolson]

I don't have much for video ... but here's what I have straight off the camera (I just grabbed a bystander to run my camera ...)

http://www.youtube.com/watch?v=A5fCzNpEZYE

[clolson]

Here's one more video taken yesterday. I should point out that this cart is a crazy experiment I came up with to try to make the wing easier to launch when it's more heavily loaded or when I want to go fly by myself. So I'm still working out some of the kinks. In this video the left wing bounces up over the front stop about halfway through the take off run. Fortunately aero forces or maybe just dumb luck help hold the wing relatively straight and even though the right wing dips down, the aircraft stays on the cart long enough to reach flying speed. In this run, the wing slides forward as it departs the cart rather than getting a clean break upwards so I nicked the prop on the cart and took about 1/2" off each end. Went from a 10x7 to a 9x7. Fortunately the prop stayed balanced and I continued the flight ... almost as if nothing happened, except for that momentary whacking sound.

http://www.youtube.com/watch?v=-asYUsz_9jE

This wing has a pretty good glide ratio ... it would probably get thumped in a real competition, but about 1/2 way through the flight a very large cloud passed over and the aircraft started getting noticeably smaller. I kept pulling the throttle back and back until the motor was completely off, and it kept getting smaller, or at least not any bigger. Finally I dove the nose down steeply and bled off about 300-400' of altitude to get it back down where I wanted to fly. I'm used to RC sport style flying so getting caught up in a thermal like that (and doing it in an airplane that is thermal friendly) was pretty wild.

Another cool thing about this wing is with it's blended body design, you get a big fat bathtub to load your gear in. More room than a Rascal 110 or a Senior telemaster and it's very convenient to get at. But with it's size, I'm still trying to come up with a way to very reliably launch when i want to go fly by myself.

Curt.

[kd7ost]

Most excellent work Curt. It's very cool to see that project.

Dan

[macboffin]

You could maybe power the cart, better acceleration, ability to punch through long grass. Power could be as simple as a long length of rubber wound round a drum on the axle?
I have dolly-launched several different aircraft and always incorporated a hold-down released by "up" elevater..(SOP for skid/belly landing UAVs.)

[Magician]

Curt,

Congrats on the new wing. The dolly is a good solution but requires a relatively smooth surface. You can also attach a strenched bunge to the cart to get it going faster in a shorter length. But, the ideal solution is to use a small bungee and put a hook near the LE of your wing. This method is used for the Dragon Eye and Desert Hawk UAVs. You just need to get it to flying speed, not go for altitude like a sailplane.

Good luck with the future development.

Chris

[clolson]

I think that may be the next direction I go with this ... add some sort of locking mechanism with the cart using up elevator as the release, and maybe explore a bungie launch system. We do have a nice catapult that we've tested, but it is in the shop for it's own improvements right now. Maybe attach the bungie to the cart? I guess it depends on how much free time I have. :-)

[Tom Harper]

Impressive rig!

The bungee experiments will be interesting.

[CenTexFlyer]

You might want to consider a pneumatic launcher like this....

http://home1.gte.net/texhills/page13.html

The movie was of a 5 lb wing with nothing other than controls, no motor. Subsequent launches of heavier wings were successful by upping the pressure on the launch tube, which was still only half of it's safe rated pressure. A paintball cylinder will provide enough power for about a dozen launches, a scuba tank will last you a really long time. Out of air? Break out the bicycle pump!

If it has anything to do with a flying wing, we've probably done it.

Gene

[patrickegan]

Or a couple of JATO rockets and you're party'n

[clolson]

CanTexFlyer: pretty clever!