Automatic sheet release

[Nordic cat]

Any description of how it works and the number of through-hulls required?

Regards

Alan

[fastcat435]

The Maximum load it can take is only 450 kilo or 1000 lbs so no good for a cat over 30 ft and it is another item that can get broken so not for us. just sail on the safe side and keep it that way . a advantage of a lightweight boat is that more wind is immediately translated into more speed and not into excess heeling. Light weight has its advantages although some people seem to think that heavy is better.
Greetings

Gideon

[multihullsailor6]

Originally Posted by Nordic cat

Any description of how it works and the number of through-hulls required?

Regards

Alan

Alan,
From what I understand of the technical description (which is still only in French, the English version should be around in a few months time) this UpSideUp system works mainly on the sail pressure for which you can input individual control and release parameters into the control box. I do not see any mention of through-hull fittings.
Not sure if Gideon's comment refers to this system, suffice it to sail that Alain Gautier had it on one of his 60' racing tris.

Roger

[BigCat]

The capsize of the Aotea:
Aotea Pitchpoles in the 1995 Double Handed Farallones Race by Jim Antrim
Antrim provides an interesting measure of capsize risk, by simply comparing the masthead height to the boat length. (divide air draft by length over all,) On Aotea, it was 1.4, which he had considered conservative for a racer- on my biplane-rigged cruising boat it is 1.085.

I am trying to remember what I came across years ago in a yachting magazine about a sheet release system that involved mounting a cam or clam cleat on a hinged board, with the whole thing held down to the deck with a bungee cord. It seems to me that you could test the pressure it took to trigger the apparatus with a block and tackle system and a spring scale like the one fishermen use. You can calculate backwards from catamaran stability formulas and the wind speed x the wind pressure at given wind speeds to calculate when you are entering a risk zone. (This would be for a sheet pressure triggered system rather than a heeling induced release.)

Wind pressure is wind speed squared x .004, with standard mph being the wind speed and the pressure being psf (pounds per sq.ft.) One capsize prediction formula can be found at www.kelsall.com/images/articles/A11_Kelsall%20Formulas_KC.pdf

[beiland]

I realize this is an old conversation,...but it just seems to have died out?

I had occasion to post on another forum a solution I once found for several multihulls I had.

Originally Posted by brian eiland

Here is a photo of another releasing cam cleat that I utilized on the centerboards aboard a Louisiane 37 cat, and on the centerboard and rudder of my Firefly trimaran design. Both worked very good.

Pfeiffer adjustable tension cam cleat - Boat Design Net Gallery

I'm pretty sure they are no longer manufactured.

I could well image a scaled up version for big sheet loads with perhaps a solenoid in control.

[UNCIVILIZED]

Do a search for Anti-Capsize System, & you'll get some info on a semi-current unit. And IIRC, one of the things which may turn up via such a search, is a link leading back to a thread on here.

Also, ti would be worth inquiring about such devices over on SA Forums also.

[Sos]

Those adjustable clam cleats look like a good solution.

I guess it would be a bit of trial and error to get the load you want
as long as you err on the safe side it should work.

[beiland]

Pfeiffer adjustable tension cam cleat - Boat Design Net Gallery

BTW, it may not be obvious how Pfeiffer unit worked. The cam cleat rotates up releasing the line in its jaws. The rotation was 'locked' into place by a ball detent that was adjustable by the 'micrometer' looking arrangement on its side.

[beiland]

BTW, I just discovered (rediscovered) an older subject thread I had started on this subject. There could be some good info here that I don't have the time to repost on this forum.

Capsize Prevention Devices - Boat Design Forums

[UNCIVILIZED]

Like I said, an older thread, but... http://www.cruisersforum.com/forums/...ces-66876.html
Plus a heap of links to; various devices, discussions, & other forums where such was a topic of note.... via Bing.com anti capsize device - Bing

[UNCIVILIZED]

Originally Posted by beiland

Pfeiffer adjustable tension cam cleat - Boat Design Net Gallery

BTW, it may not be obvious how Pfeiffer unit worked. The cam cleat rotates up releasing the line in its jaws. The rotation was 'locked' into place by a ball detent that was adjustable by the 'micrometer' looking arrangement on its side.

I have to say that this one, & the principle described on how it works, as well as one other similar to it in this thread, reminds me of a design which was in one of the older multihull books, which I read in the mid 90's.
It's not that I'm commenting at all on it's effectiveness, just that if someone's got a good multihull library, & the inclination to do a bit of digging, there may be more information out there on this type of release mechanism.

Plus, I Know, that there are other designs which have been tried. Many of them simple DIY affairs.
Such as modifying a cam cleat, so that the jaw on one side is affixed to a plate which swivels on the fore & aft, horizontal axis. And hanging down from said plate, in the vertical axis, is a large weight, designed to swing over far enough to ease the cam's pressure on, & release the sheet when angle X is reached.
Although, such a system, would have some obvious flaws.

[Therapy]

Originally Posted by UNCIVILIZED

Although, such a system, would have some obvious flaws.

Although, such a system systems, would have some obvious flaws.

Perhaps why we don't see any of them.
If they worked half assed they would be being sold with the drogues and life rafts.