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Old Feb 01, 2005, 12:06 AM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
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zip launch?

Is a zip launch a super mini hi-start?
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Old Feb 01, 2005, 06:26 AM
xtc
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a zip launch is similiar to a catapult launch,,the tow hook is near the nose so the glider goes horizontal very fast until after release at which point the glider is rotated up to burn off the excess speed

dont try this without ailerons for roll control!

xtc
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Old Feb 01, 2005, 06:53 PM
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Hesparia,CA
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O_O, wow. and i just made a hook for my RE handlaunch, anyone else chim in before i blow up my wing?
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Old Feb 01, 2005, 06:59 PM
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Be sure the cg is correct...use approx 25ft of 1/8" tubing and 200ft of line....should be fine..stretch the tubing approx 2.5x its length ... I have used the 2m upstart on my gnome... and other HLG with much succ.ess... though these have stronger wings.

Mike
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Old Feb 01, 2005, 07:45 PM
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im not shure of the strength of it, it has survived many a bad v tails so far i just know when the wing and fuse were originaly biult 15 oz was competitive for javalin planes, should i not try to zip it or go ahead, its RE only
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Old Feb 01, 2005, 10:56 PM
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What i described was a hi-start launch... this works very well with smaller planes.
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Old Feb 02, 2005, 02:42 AM
xtc
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Quote:
Originally Posted by tsunami
im not shure of the strength of it, it has survived many a bad v tails so far i just know when the wing and fuse were originaly biult 15 oz was competitive for javalin planes, should i not try to zip it or go ahead, its RE only
the bungee controls the pitch the you have no yaw control while on the bungee

without ailerons you will have very little roll control at excelerated speeds???

ailerons are a must for this form of launching
xtc
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Old Feb 02, 2005, 11:29 PM
Boomer
San Diego
Joined Dec 2003
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If you are using only rubber/bungee (no string) make sure that the staked down end cannot let go (one manufacturer recommends two stakes) or you could end up like a dead vampire. Can ruin your shirt!
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Old Feb 03, 2005, 07:00 AM
DrCarter
Princeton, TX
Joined Jan 2005
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You really don't have to have ailerons. Not meaning to correct another post but we have used this style of launch before models had ailerons. My first to do this with was the Skeeter when it first came out. Our local club has a once a month contest and we use small upstarts. With a slight wind we get about the same height as a good Disc launch. We have done this for over 20 years and I have seen 3 wings fold though the wind was over 15mph.

The best spot for the tow hook seems to be 1/4 inch in front of the cg. If the model is balanced perfectly, at 1/4 inch forward cg, you will not have to worry about stalls or pop offs at any wind speed and get the most altitude. The only control input needed would be rudder except for when it's time to come off the launch.
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Old Feb 03, 2005, 09:07 AM
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Seems to me that we are talking about 2 different launch methods. One which is a low power high start and another which is basically a catapult launch. Unless, you are familiar with both types, you could confuse the two.

The high start launch needs a tow hook close to, but in front of the CG. The catapult launch needs a tow hook considerably further forward, but not right in the nose of the plane.

XTC is discussing a catapult style launch which the plane is launched forward at a high speed. After the bungee disengages, you pull the plane up to climb. Since the bungee is controlling the direction of the plane, if you do not have ailerons, you will not have any roll control on the plane.

Thermalin is talking about an upstart launch which is simply a short highstart. RE planes can be launched easily with this method. Ray Hayes sells a "ZIP" start for HLG which is a short high start with lightweight rubber. This should be safe for most any HLG.

I would not recommend the catapult launch for HLG unless the wing has been strengthened with this type of launching in mind.

EJ
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Old Feb 03, 2005, 10:32 AM
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Delaware
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We did this years ago when we wanted to even out the throwing strength of different flyers during contests. Two poles firmly in the ground about 15 feet apart. High start tubing stretched loosely in between. Twenty feet of string with key rings on each end. One key ring on the tubing, the other goes to the plane. Pull back to a pre-determined spot and let her rip. No ailerons on planes back then.
Terry
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Old Feb 03, 2005, 11:35 AM
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terry:

Interesting approach. Where were the towhooks located on the planes? How much stretch did you use?

EJ
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Old Feb 03, 2005, 04:31 PM
xtc
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Quote:
Originally Posted by terry.cx
We did this years ago when we wanted to even out the throwing strength of different flyers during contests. Two poles firmly in the ground about 15 feet apart. High start tubing stretched loosely in between. Twenty feet of string with key rings on each end. One key ring on the tubing, the other goes to the plane. Pull back to a pre-determined spot and let her rip. No ailerons on planes back then.
Terry
place the tow hook right on the nose like the original topic of the thread and im sure you will need ailerons


xtc
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