Hi Brion -
I must admit I'm a bit taken aback by the vehemence of your response - I was hoping for constructive input, not browbeating. I'm not making recommendations. I'm simply sharing ideas and rigging that works for me in the hopes we can collectively improve the enjoyment and safety of sailing.
That said, here is the engineering data on the hardware I used:
Belay Device:
http://www.amazon.com/Black-Diamond-...ef=pd_sbs_sg_5
Micro blocks:
http://www.harkenstore.com/uniface.u...?409Z56LC3VXJE
1/4" 3 strand nylon:
http://www.westmarine.com/webapp/wcs...4&ci_sku=25499
Belay device rated at 22kN -
I kN = 224 LB and 22x224=4928lbs
SWL of Harken 348 blocks: 330lbs, ultimate strength 1000lbs
Ultimate strength of 1/4 Nylon (3/16 was a misprint) 2000 lbs - SWL therefore equals 200lbs (10% rule)
The blocks and line are well matched, with the SWL of the line well under that of the blocks. I have empirically tested the setup and it needs only direct hand tensioning to function effectively - no purchase - maybe 70 or 80 lbs ...
As far as loading and vectors, I am a licensed Architect with an extensive engineering background, so yes I'm aware that load paths and angles effect actual loading in structures due to leverage and mechanical advantage.
I chose nylon for its elastic properties.
All lines should be regularly inspected for wear and chaffe, including dacron. 3 strand nylon is cheap, elastic, and its structure provides a lot of point loading friction against the aluminum.
Boom vangs are not critical components - I did without one for over a year. My brake sorta is, but the way it's set up, the boom will move slowly rather than overload the line the way a boom end preventer will if the boom and main trip in the water badly enough during a roll or broach.
At that point something is going to give, and I'd rather have micro block flying across deck than a stanchion carrying part of the deck with it.
If the block bail or pin fails, the cheeks and sheathes are still captured by the line. If the line fails....big deal - the boat performs a "normal" (-deadly-) jibe.
You have to duck when jibing no matter what, but I'd rather be hit by a boom moving 2 feet per second than one moving 10 feet per second if I'm distracted by a hot chick or something while jibing.
( You know: F=MA and all that...)
Everything on a boat is a trade off. I've found the additional cost, complexity, and small risk of injury from my setup is more than offset by the boat handling advantages and safety it provides by controlling the boom downwind in challenging conditions.
Here is a video that shows how it works:
http://www.youtube.com/watch?v=GWJRfLGwex8
Booms can and do kill and maim people all the time aboard sailing craft.
Micro blocks?
Not so much.
Rather than give the next guy who posts something you consider dangerous or not well thought out a hard time, why not try to help him? You never know - that guy might have a good idea, have actually thought it out very carefully, and be an expert in a field related to yours.
You might learn something from him, and he from you.
You say "Fair Winds"?
I say "Following Seas"
Bill Hogan