Bungie Launcher

[Gabe]

Well, I almost lost my hand the other day with my Darkside Stryker. Throttled up against 20 mph winds and a side gust caught it. I was able to hold on to the finger slots on the bottom and drive her into the ground, upside down. The prop never hit the ground and the only damage was a little lifting of the glass by the finger slots.

I went to shop.rc-electric-jets.com/Jetapult-Complete-System-Jetapult-1.htm and bought the system. Matt from the company said he's sold a bunch to Stryker guys. I just need to set the prop horizontal and keep the throttle off until the plane has been released. There's supposed to be enough power to send it at least 100 yards.

I'll give the full report when it arrives.

[akent]

I have one of those, too, Gabe! I love it!

These are nice and compact, too.

I bought mine as my fast Funjet has a horrible torque left when you throw it. I have crashed this thing a few times on takeoff. Never again with the Jetapult!

The only thing I would recommend is to launch your plane without power from the Jetapult. The prop can hit the lines if you don't. It's really easy to just hit the foot switch, fly it up and away for a few seconds and then nail the throttle.

You are gunna LOVE yours!

Oh, one more thing. If yours isn't drilled for it, you should drill the nylon post of the release pedal for the safety pin. I didn't do that at first and I had the line slip off once. That took the Funjet and hurled it when I was just hooking it up. No damage, but it scared the crap out of me!

Kent

[Gabe]

Good advice Kent. I'll check for that when it gets here.

I'm stoked on it now that you've weighed in!

[19000rpm]

Glad to hear both you guys have got those launchers. Many an accident have happened without them.

[akent]

Yeah, 19k, and I've had my share.
The last crash I hit the pavement in the parking lot at the flying field at >100mph.
I think I posted that somewhere.

That scared the crap out of not only me, but the family on the bicycles who promptly left.

Granted, I think one of the aileron hinges was torn, but that would have been much easier to handle if it flew off of the Jetapult. At least with this you have flying speed early on, or not! If not, then you don't have to give it gas!

Man oh man...
Kent

[19000rpm]

One of best features, as you point out, of the bungee system is that you do have an opportunity to abort a flight at the last second because of the plane not requiring the use of it's own power to get it flying. That and the fact that you never need to have your hand anywhere near the prop. Bungee systems are great for safety and the launches are very predictable.

I've become more conservative about how and where I fly.

Having had more than a few planes fall out of the air last season, for no apparent reason other than electrical or mechanical failure, it became even more obvious (DUH!) how dangerous these things can be because of their unpredictability.

Most of my flying sites, soccer fields and parks, are bordered by homes, schools, trees, light poles, power lines and lots of people. And, many of those folks show up out of nowhere (How dare they!!) while I have a plane overhead. When that happens, I fly as far away from them as I can and/or safely abort the flight as quickly as possible.

Who knows when the the tragic, unexpected, thing is going to happen? I don't want anybody to get hurt just because I wasn't careful enough or the people wandering into the area are simply oblivious to what I'm doing.

If spectators show up: I insist that they stand behind me and the aircraft's flight path. If they don't cooperate, and most of them do, I just stop flying until they leave. That goes double for the times when the aircraft I'm flying is a heli.

The fastest planes I fly only do 50-75 miles an hour. That's walking speed next to the ultra fast planes some of you guys fly. So, for now, on I'm reserving the fast ones until I find an isolated area, or an official RC flying site, suitable for the purpose. And, you can bet I'll be using a bungee system to launch the FunJet or any other insanely fast pusher.

[Gabe]

Ok, I ran into an issue, my Stryker has a 5/16 cf tube running from tail through the nose. The Jetapult requires you recess a 1/4" piece of plywood into the foam where the tow hook will be drilled in and then it all gets epoxied. Any ideas? Maybe just drill straight into the cf tubing and throw some mesh and resin around it?

[19000rpm]

Sounds like that would work.

[akent]

I have not used that huge chunk of wood with the bent nail, yet.

What I did for the Funjet Ultra is to use a large nylon skid glued to the bottom.
I cut the tape and into the foam a little, then drilled holes in the skid and stuck toothpicks through, then glued with white gorilla glue. CA didn't stick well enough.
I did take some sandpaper to the bottom of the skid, too.
I then snipped the skid back to hold the hook.
It has held up great so far.

Here's a couple of pictures:

[Gabe]

Thanks Kent!

I ended up drilling a hole through the cf tubing towards the front, stuffing some glass in the home with epoxy, and then placing a little bit of mesh over the tow hook.. It's almost to the nose to I'm concerned about it being too far in front of the COG. Any thoughts on that? I'm guessing it's 8" from the COG.

[19000rpm]

Nice solution Kent!

Gabe, I don't think the location is too far forward. I remember doing some bungee launches (We used surgical tubing back then)on rocket powered planes and the key was to have the hook considerably ahead of the COG. If you got it too far back the plane had the tendency to nose up at the end of the launch. The only thing you might want to consider is checking to see if the COG is still the same and add weight to the tail if it's off.

[Gabe]

Matt from Fan Jets USA got back to me about it. The only thing I will see I a slight downward angle of the nose on launch. It will clear just fine he said. Countering with up elevator is the easy solution. Looks like it's a go for next week!

[akent]

Yep, I keep quite a bit of up elevator on launch. I like it to pop up.

I think you'll be fine with the more forward hook. You might need even more up elevator, though.

You'll know soon enough!

Kent

[Gabe]

I forgot to post my results!

The bungie launcher is awesome!!! Never again will I worry about losing a finger. I step on the pedal, five her a little up elevator and BOOM- she's 50 yards away in a snap!

Two thumbs up for the jetapalt! Worth the $70.

[akent]

That's great news, Gabe!

I've been using mine until weekend before last. I didn't bring the launcher to the field, so I hand launched the go-fast Funjet.

I couldn't get my hand to the sticks in time and it torqued over inverted and smacked the ground HARD. The fuselage bent in half and broke off almost at the carbon spar. The impact tore off the vertical stabs! I guess it was going pretty fast...

Scratch ANOTHER AR6200 and battery. UGH! The motor, ESC, and servos are Ok.

I will never hand launch a fast Funjet again. Funny as the slow (110mph) Funjet is easy to hand launch. It's also a LOT lighter.

This was Funjet #3 lost to a bad hand launch.

(I already have another one on order!)
Kent