From: soc1070
Newsgroups: rec.models.rockets
Subject: Re: parachute 101
Date: 28 Sep 92 14:40:00 GMT
Organization: University of Minnesota CIS
News-Software: VAX/VMS VNEWS 1.41

In article <1992Sep28.045902.10967@cs.umb.edu>, mrubin@ra.cs.umb.edu (Mark Rubin) writes...
>I just got back into model rockets after about a 10 year break. Any help
>on the correct, sure-fire method of connecting parachutes would be great.

Connect the 'chute to the shock line and not to the nose. This helps
prevent the nose from getting tangled in the shroud lines and if the
shock line seperates from the nose, the body of the rocket is still
attached to the parachute. Only the nose will fall - you have a much better
chance of getting both back.

>On my launches today the parachutes worked good except in one case where it 
>didn't open all the way. I knew it was gonna happen b4 launch because there 
>was a small knot among tangled shroud line. It came down faster but with no
>damage. The problem was maybe that the lower 1/4-1/3 of the shroud line 
>closest to the nose cone was tangled - on both rockets. Maybe with more care
>this could have been prevented, but I kind of had a problem from the beginning
>with the way the instructs told of attaching the shroud line to the chute.
> 
>Here's a stupid diagram of the way it tells ya:
> 
>		1          2
>	       ______________
>	      /	x	   x \
>	     /		      \
>	 3  / x		     x \ 4
>	    \		       /
>	     \  x	   x  /
>	   5  \______________/  6
> 
> 
>Connect:  1 -> 2
>	  3 -> 5
>	  4 -> 6
> 
>The lines do not line up with each other. If you put the 3 -> 5 and 4 -> 6
>together, then when joining 1 -> 2 with the others it obviously has to be
>twisted which could be detrimental to the correct operation of the chute.
> 
>Would it be better to connect them like this?
> 
>	1 -> 2
>	3 -> 4
>	5 -> 6
> 
>Making 3 -> 4 a little longer than the others (haven't worked out the
>exact measurements yet).

Unless this is a weird manufacturer, the 'chute should be a perfect
hexigon. If the chute is any regular, even sided polygon (4,6,8,10
sides) all the lines will work out to be the same length.

Making your oun parachutes is pretty easy. Start with the desired material
(usually mylar or a light plastic). Make a cutting pattern out of cardboard
by first drawing a circle that will be the maximum size of the chute
(i.e. 16"). Take a compass something that will give you an accurate
radius of the circle. Pick a point anywhere on the circle and using the
radius as a length draw an arc that crosses the circle. At the point where
the arc crosses, reposition the compass on that point and draw another arc.
Keep doing that all the way around the circle - you will end up with
six points including the starting point on the circle. Connect these
points with a straight edge and Presto! a hexigon. Cut out the hex from
the cardboard (I use artists matboard...) and this is your cutting 
template. Lay the template on the material and using an EXTREAMLY SHARP
XACTO KNIFE cut along the outside of the template.

Make shrouds from a heavy guage thread - cut three equal lengths twice
as long as the diameter of the chute and connect the ends to corner
points adjacent to each other.

>Any help would be greatly appreciated along with any tips on judging
>the wind and how far the rocket should be angled into it - as well
>as predicting where the rocket may land.
>
I'll leave that one for another..

>Thanks alot!
>
You bet!

Tim Harincar			"Always listen to experts.			
Central Minnesota 		They'll tell you what can't
Association of Rocketry		be done and why. Then do it."
soc1070@vx.acs.umn.edu			-Lazarus Long