shroud line length?

[jerryb]

is there a good formula for the LENGTH of shrouds on chutes?

I've gotten good at sewing the rip-stop canopies, but have been just kinda eyeballing the shroud line lengths.

say for a 24" or 18" canopy.. what would be the optimal length for the shroud lines?

later
Jerryb

 

[powderburner]

Someone did some research many years back, and came up with the observation that the optimum line length is 1.5 times the diameter. I doubt that if you are off a half-inch or so that it would matter much, but don't forget to allow some shroud length for attachment to the canopy and for gathering/tying into the tether.

Equally important qstn: How many shroud lines are best? Answr: Something like eight to ten was the 'sweet spot' but it doesn't hurt to have a few more, especially since using ten to twelve shrouds will turn a parasheet (a 'chute cut as one piece from a flat piece of stock) into a pretty passable excuse for a real 'parachute' (in other words, don't stop at six)


Welcome to TRF! We are glad you joined in, and if you will post a bit more info on your project I'll bet a bunch of guys will jump in here and give you more pointers!

 

[Micromeister]

As with most everything there are options: sport or competition, etc.
First when we say shroud length are we tallking about the total length of the line or the half length between a camopy point to the shock cord attachment point? The lenghts below are Total Shroud Length canopy point to canopy point.

For sport flying parasheets 6 points (three shrould lines) are fine. Competition parasheets 12 points(6 lines) have worked best for me.

Generally sport model Chutes have Shrouds 2.25 to 2.5 times the diameter, while competition chutes may go as long as 3 times the diameter. If your planning on going over the top of the canopy for heavy duty dual egg lofting for instance you'll want to increase to 4x diameter. I've seen chutes over 48" dia with shrouds that looked to be 5 or 6 time the diameter but I can not for the life of me figure why they need anywhere near that length.
If your using a flat mylar, plastic or nylon parasheet the longer length (to 3x dia.) helps the canopy develop the widest possible canopy pocket. If using a hemispherial gore consturction parachute, 2.5 times has worked fine for me. The new Mars lRover type skirted chute has much longer shrouds maybe 4 times the dia. to help keep the curtain wall open, maybe someone who knows more about that design can explain the extended shroud length.