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Old May 13, 2012, 10:09 AM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,510 Posts
Question
Question on bungeeing f3b models

Hi,

I have started on the road to wrack and ruin that is f3b, but my weakness is thermal soaring. I am thinking if I set up a bungee and just keep practising I can improve on this.

how much room do you need for a meaningful bungee?
recommendations on a set-up would be helpful.

I have about 400ft (130m ish) max to play with. I have my own small field, but it is not big enough for the 200m of an f3b line.

supplementary question - do you guys practice on your own? I am really cautious about self launching now, as I did severe damage to a model trying it on my own.

thanks
T
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Old May 13, 2012, 10:39 AM
Thanks CB, WD x2, T, DC
seaspb's Avatar
United States, OR, Silverton
Joined Nov 2008
923 Posts
Hi,
I used 100' of rubber and 100' of line that i would then strech 100' to launch a Tracer worked great. On windy days I even put ballast in it for some speedy dives.


Sam
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Old May 13, 2012, 10:54 AM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
6,940 Posts
BTW Tom, I just got some Hosemonster rubber. Mark at Aerofoam is great to deal with!
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Old May 13, 2012, 11:08 AM
dare to thermal
Mannheim, Germany
Joined May 2004
600 Posts
In Germany we call it "Flitschen". Horizontal acceleration to 110-150km/h and convertion of this speed into height. :-)

Check this out:
http://www.rcgroups.com/forums/showp...8&postcount=29
All you need is 15m rubber-hose and 15m line (total 30m) The rubber will be extended by 300%-400% (45-60m)., which leads to a total amount of space of about 75-90m.

Bernd

ps. this kind of start is very safe!
Flitschenstart: http://www.rc-network.de/upload/1106063149.jpg
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Old May 13, 2012, 11:28 AM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
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Quote:
Originally Posted by Bernd Brunner View Post
In Germany we call it "Flitschen". Horizontal acceleration to 110-150km/h and convertion of this speed into height. :-)

Check this out:
http://www.rcgroups.com/forums/showp...8&postcount=29
All you need is 15m rubber-hose and 15m line (total 30m) The rubber will be extended by 300%-400% (45-60m)., which leads to a total amount of space of about 75-90m.

Bernd

ps. this kind of start is very safe!
Flitschenstart: http://www.rc-network.de/upload/1106063149.jpg
Love that "Loop-landing" !

This would be similar to what Hosemonster call "Zipstarts".
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Old May 13, 2012, 12:01 PM
Build A Rocket Boys!
PDX Slope Pilot's Avatar
Portland, Oregon
Joined May 2002
4,012 Posts
To get the maximum straight and level speed with the Flitschen setup, will the regular tow hook position suffice or do you need to rig a hook towards the front of the nose cone as the pic in the link shows?
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Old May 13, 2012, 12:19 PM
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concreteman's Avatar
United States, CA, Torrance
Joined Aug 2004
1,830 Posts
Tom,I will get information from Target on what we used the other day, which works perfectly. I think its like 6-8 meters of some serious rubber, and maybe 15-20 meters of mono. Works like a charm. Target launched his Extasy and got to maximum height on every launch...

WD
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Old May 13, 2012, 12:34 PM
dare to thermal
Mannheim, Germany
Joined May 2004
600 Posts
@PDX Slope Pilot: The horizontal force of the rubber is about 15kg. Using the normal tow hook results in a strong righting moment (nose up) - this is very critical. The best way is using a short pin like in the picture. Donīt use a hook.. with the forward located pin the acceleration is more or less horizontal.

Masterpiece an der Flitsche auf 137m (0 min 12 sec)


If you need more informations let me know.

Bernd
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Old May 13, 2012, 01:06 PM
Build A Rocket Boys!
PDX Slope Pilot's Avatar
Portland, Oregon
Joined May 2002
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Bernd,

Thanks for clarifying this for me.

Vic
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Old May 13, 2012, 01:23 PM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
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I don't really want to modify my model. I was looking to use the normal tow hook.
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Old May 13, 2012, 01:23 PM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,510 Posts
Quote:
Originally Posted by concreteman View Post
Tom,I will get information from Target on what we used the other day, which works perfectly. I think its like 6-8 meters of some serious rubber, and maybe 15-20 meters of mono. Works like a charm. Target launched his Extasy and got to maximum height on every launch...

WD
Thanks Warren.
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Old May 13, 2012, 02:27 PM
Registered User
Joined Jan 2010
185 Posts
Tom,
I have bungeed F3B models using the normal tow hook.
Its like a winch launch but you cant turn the power off.
Get your model sorted on the winch before trying the bungee, make sure that the model isnt all flicky on the line, or you could have issues.
Make sure you launch with the nose up a little and always into wind.
Other then that treat like a normal winch launch.

Jon
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Old May 13, 2012, 03:21 PM
dare to thermal
Mannheim, Germany
Joined May 2004
600 Posts
tape-on hook for the zip starts

Tom, itīs possible without modifications!
You can use a tape-on hook for the zip starts. I use this on my X-21

Bernd
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Old May 13, 2012, 03:36 PM
Detail Freak
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Harbor City, CA
Joined Oct 2003
21,618 Posts
The following is for launching from the normal hook-

We used the AeroFoam "Mega Bungy" setup as a zip start.
Its 24' of 5/8" OD x 1/4" ID rubber, staked into the ground very securely.
At the other end is whatever length of line (I use @ 50' of old F3B mono), and a heavy duty chute with a ring on the apex. The chute takes all of the strain of the bungy setup this way, so it needs to be up to the task.

I hook up to the plane, get situated with the plane and radio, and THEN start walking back. I think its much better doing this NOT to use a neck strap....That's my opinion, if you can make it work, more power to you.

I get situated, and launch with the plane in section. There is no time to be flipping switches, in my opinion.
On the launch, the main thing is not to hit yourself in the head with any part of the plane, and make sure the wings are level.
Before all the energy in the rubber is expended, I do a little ping, and this is where the true altitude gets gained.

You should first have someone else that you trust launch, and launch for them, if you are not super comfortable winch launching with great tension. The tension is always there, you need to be ready to throw BEFORE you walk and tension the bungy.....

If you want to be REALLY careful, try it with a thermal plane first, like a 3.5 Xplorer or something similar. You can work on your form with a plane with giant tail surfaces before you take the plunge with a B plane.

Its really fun to launch only to about 125' and then find a thermal. a place that has active conditions is good, and I think also a light steady predominant breeze (just for launching into) is also a good idea.

I CANNOT STRESS ENOUGH how important securing the end of the rubber is..... The last thing you want is a spike launching at you with 35lbs of force behind it, and you holding a $3K molded plane.....

My ground end of the rubber has an eye (that it came with from AeroFaom). To that I have a looped length of chain connected with a quick link. The chain can be put around a fence poste, or have multiple 12" x 3/8" galvanized nails (pounded in at different angles) holding it fast to the ground.

Don't get hurt!

I have yet to try the forward hook, but would like to in the future using the setup Bernd posted above.

R,
Target
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Old May 13, 2012, 03:45 PM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
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Depending on the size of your field, I would imagine the longer the line part the better. It get's you more altitude, and also from a safety point of view gets you physically further away from the rubber and peg end of things...
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