Bungee Questions

[Hamburglar]

Hey guys,

I'm after a new bungee for launching my foamies in the park when there is no wind (like today ). I made one using 10m of elastic cord from Bunnings. It launches the Wasp really well but it's a bit gutless for the Moth. I did a search and found that you guys use the Hosemonster bungees. I checked out their website but there are so many to chose from

Are you happy with their performance?

What's the difference between a high start, a catapult, and a bungee?

Which one would be suitable for launching 30-60" foamies in the park or at the slope?

And are there any other brands that I should check out?

Thanks,

Jordan

[thevon]

Sean and I have this one from www.aerofoam.com/hosemonster.html
- it's the basic catapult:
25' Catapults (shipping included Con.US. email for shipping elsewhere.)
Standard bungee 1/4"ID x 1/8" wall x 25' with connectors $50.00

Truly awesome. I think Ezza has the next thicker one

[skyzking]

The one Andrew mentioned in the previous post looks like a very good deal for the price.
If you cant be bothered ordering something and anxious to have something going quick, then heres a suggestion; go to a marine shop and ask for shock cord of about 5 to 6mm in diameter. 30 meters of the stuff is enough to launch a 2m glider to good thermal hight.

I hope that helps...

[chamm37]

yer that is what i have done mate.....i went to a marine shop and said to them what i was doing and they sudgested 8mm thich shock cord i did some calculations and got 25m of it.....i am so impressed with it and it only cost me $55....It stretches to about double its origonal lenght and shoots my Bevo which is 1030grams about 200ft in the air at SC today....just ask mark and Andrew. Andrew was even impressed with the height that i was getting on the bungee at Mt Mee a couple of days ago ;D

I have also gone down to the local field amd lauched it in the air and i still get as much hieght on which i do at the slope......The Bevo is built to DS and not glide so it goes up but it comes down after a little of glidding but if you go up and dive back down it sounds ausome coming at you really fast ;D i havnt tried it yet but when you have the larger and heavier models you could double up the bungee and produce some more power to launch out on the slope or even test your model
I have also launched in the air at the feild when there is wind and it goes highier if you angle the glider right I havnt had the radar gun at it yet but it is going fast and makes the BEvo fly HIGH ;D
The shock cord system has been a real success and is worth trying it

What is the weight of the Moth

[Slopefun]

HI Hamburglar

I have 25feet off latex rubber if you are interested.
I bought 2x50 feet rolls and i use one roll for launching a 2.5mtr glider and cut the other one in half for launching epp wings etc.
I used to launching a wingwarrior Raider and a zipper with a lot of fun.
Paul

[Hamburglar]

Jul 12, 2008 22:24:50 GMT 10 Slopefun said:

I have 25feet off latex rubber if you are interested.

Thanks for the offer but I've got less than a week left in this country and I doubt it would get to me on time.

I'm gonna order that $50 Hosemonster catapult when I get home. Thanks for helping make the choice.

The one I'm using at the moment is 10m of 5mm shock cord followed by 3m of orange bivvy cord. I have a 3L bottle of water tied to the end to take the weight if the stake pulls out of the ground.

The Moth weighs around 19oz.

Jordan

[thevon]

The rubber tubing is heaps better than shock cord. Chris's 8mm cord is better than the 6mm one I've used. But the rubber stretches to 3x its length, whereas shock cord is 2x or less. I found the shock cord fine for the lighter planes but it didn't handle the Reaper well, although doubling it helped.

There are articles on the net about bungeeing - it's a real science. What we've been doing with our bungees is a CATAPULT, which launches the plane like a PROJECTILE. You mount the hook a long way forward of the CG, and use massive acceleration to shoot it forward then you use the speed to pull up to get height, trying to avoid the back window of your Subaru while you do this. The catapult is maybe 8m of thick rubber with about the same length of thin line.

Whereas a HI-START launches the plane like a KITE. It has thinner tubing, and a very long length of thin line, maybe 30 metres or more, and you have a parachute near the end of the line to assist the line to detach. The Hi-start is like a winch launch (without the ability to switch the winch off if things go bad!). It's more suited to thermal sailplanes. You mount the hook only a few mm in front of the CG, so the plane "stands up" like a kite, it lifts and points up hard right from the launch.

[Hamburglar]

Thanks for explaining the differences!

My bungee hooks are well forward of the CG. I built one on my Moth using these plans from the NCFM site www.northcountyflyingmachines.com/bungeegraphic.jpg
It's great being able to remove the hook/pin so that it doesn't catch on anything during transit. It looks nice and clean too. I'll definitely be using this idea again.

[thevon]

I just noticed looking at the Hosemonster page, he has a big variety for different planes. For example for the 3 metre planes (like our Fazers, Pikes etc) he sells either 50 or 100 ft of rubber with 250 or 500 feet of line!

That Moth hook idea is great. Might use it for the Ozprey and Reaper.

[thevon]

Guys I sent a question to Mark at Hosemonster and thought the reply might be interesting to some of you. Here 't'is ...

Hi Mark, I bought one of the standard 25ft catapults from you recently and have been using it to launch foamies etc. If I wanted to get a good histart for my 3M carbon thermal ship (Fazer F3B weighing 2.4 kg), would it work if 2 of us joined our standard catapults together? Are they the right size rubber?
We did try using the 25 ft length today with a bit of shock cord added, and it was OK but it ran out of pull pretty quickly. The height was OK, but not great. Thanks, Andrew

You need to use a line that is 4 to 5 times as long as the rubber, so 125ft. for the 25ft. section, or 250ft. for the joined 50ft. section. You can join 2 together, it will be a bit stronger than the 4m rubber, about 10% more pull. You can also over stretch the rubber to about 400% if you really want a hard launch. I am in the process of coming up with suitable short field F3J launcher that will handle 90oz. planes like a fully ballasted Pike perfect. It looks like the magic formula may be a mega bungee with 75ft, of heavy line and a chute with heavier rings. This puts the plane up with more force than a winch and allows a good zoom. It actually launches almost as high as a winch, but in a very short distance. Not for the physically challenged....

[sean]

Sounds great Andrew, lets give it a go!