Ummm...as much as I am all for self reliance and building stuff for the boat form the ground up and all...I would think long and hard before taking the DIY approach to a parachute
anchor.
Firstly the stresses involved are pretty hefty (especially for the weight of boat you are dealing with), secondly is the fact that the secret (or "dirty little secret") of most parachute
anchors is not the unit itself but the deployment and recovery gear and methods. That is where the patents lie and where individual units vary wildly.
The thing is no use at all if you need to risk your neck for 45minutes to deploy it in the sort of awful weather where...well..where you would consider deploying one. It is of even less use if it tangles into a huge clump of rope and fabric and fails to balloon.
Then there is the issues of chafe prevention on the
line used and lastly (on the bright and peaceful dawn after the storm) the problem of getting the bloody horrible but expensive thing back on board and stowed, despite the heavy swell etc.
It is these "secondary" functions that make it worthwhile getting a ''chute made by a reliable and proffessional company that specialises in them.
And that is even IF you can get your hands on the walking-foot industrial sewing machine that you will need to make one and if the fabric and labour costs does not put you right back int he ballpark for what you would pay for a commercially made unit (they pay a lot less for their materials by buying in bulk, In this type of stuff, the retail markups are truly hideous).
So my suggestion is do some serious pricing and shopping around and consider whether you want to "experiment" with something that can serve as a last-resort survival tool on the off chance that you can make it nearly as well as the commercial models and for a couple of bucks less.
Just my thoughts on it, since we had the same sort of thought to think through when we outfitted our boat recently. I did about 95% of the labour, about 60-70% of building stuff from scratch....But we bougt the ''chute...and ours is only one of the smaller ones (10.5 meters).
My final bit of advice is to NOT get the chute made by your sailmakers. They are totally different products. When we talked about para-anchors with a sailing mentor of ours he said that his had been made by a sailmaker (good quality) but that the one time it had been deployed (''98 Sydney-Hobart) the only thing to do aftetr the blow was cut it loose and wave it goodbye (hoping that it would not wrap around the rudder as you went past), the thing had twirled and tangled all night long and though it had done its job, it was $1400 they got to write off)
Sasha