Self righting multihull?

[Alan Cattelliot]

I like rockets very much.

 

[Paul Scott]

Julian Bethwaite and an Argentine NA did some doodling, and came up with what looks like a kind of big trimaran, with raised small floats (at rest, IIRR well above the waterline) and a fin keel, a big version of the small one man trimaran Frank and Julian were messing with- the HSP

Anyway, in my mind that begs the question of what a Gougeon 32 type narrow catamaran would look like with a central fin keel (think large FrankenArrow Cat with lead), but how much ballast or fin length would you need to make the boat self righting (with or without the friendly mast blimp and sealed mast)? Water ballast is in G32 hulls already, so an extra 600 (?) pounds of ballast is already part of the G32 equation. Not exactly the smaller spiral, but compared to most 30 foot cats, maybe lighter?

Gets even more interesting contemplating the same ^ approach w/ a biplane catamaran with sealed unstayed masts.

Would going narrow with a catamaran save enough weight to put that weight into an effective ballasted keel? The engineering and build would be, um, intere$ting…. Carbon….. mmmmmmmm…….

 

[oldmulti]

Paul. please look at the following jpeg. The design was not a commercial success but attracted some comment. Again, people are not as concerned about capsize as the market is splitting into those who cruise and like a wide heavy cat with a lot of accommodation (big French cats that often lose their rigs before they capsize) and those who want to race and want a wide very light multihull. Ballasted multihulls were tried by the 21 x 10.5 foot Golden Miller in 1959 and was OK but a relatively poor performer. The Miller 24 footer performance is unknown. Speak to those who own a G32, all love the performance and few use the water ballast feature. They put up with the occasional capsize and self righting features to have the speed.

 

[Paul Scott]

As an owner who has commissioned a bespoke yacht, I’m going to disagree with the idea that the standard of ‘a commercial success’ means as much as you posit, as far as boat design is concerned.

I understand the rhetorical and economic power of the limits of commercialization of boat design, but it is usually 25 or more years behind even mild cutting edge.

Golden Miller had 2 (!) keels. Surely, in 60+ years, some advances in design may have occured.

As far as the G 32 is concerned, I don’t know of any who have removed their water ballast. If you know of any, I’d be delighted to know how many.

 

[oldmulti]

Paul. The water ballast on a G32 is just 2 tanks, 1 per hull. You either fill them or empty them at your choice. The majority of the time they remain empty. If heavy weather arrives and you are going upwind then you may fill the windward tank, down wind you empty them. The G32 was one of the first really self righting capable multihulls that existed with its partially adjustable rig and optional filling water ballast. But like all good ideas only 30 odd were ever made and the owners of the 30 boats rarely sell them. The G32 was very good for its time but has not been replicated by others. I can name several large multihulls that can be righted after a capsize (Kelsall 38 ft cat nose sinks then lifted, 2 Gougeon tris small floats, Gougeon cat strings, Farrier tris fold float lift mast to surface etc) but multi sailors don't seem to care that much about capsize and sail to their limits. Yes there has been many design advances in 60 years but when you have 21 foot home built Wharram's sail the globe and race across the Atlantic (Cooking Fat), self righting may be a desire but not important to many in the industry.

 

[Alan Cattelliot]

Would going narrow with a catamaran save enough weight to put that weight into an effective ballasted keel? The engineering and build would be, um, interesting…. Carbon….. mmmmmmmm…….

Interesting thought. I note that the GC32 is quite narrow. Could have been part of the equation indeed.

self righting may be a desire but not important to many in the industry.

What could be the cause of this ? Anglo-saxo are prone to speak about the bad habbits of french sailors in term of security. Could the market of multihulls be tinted as such, that it would become acceptable to sail with a boat that can capsize, without additionnal cares, allowing the overall risk to be balanced ?

 

[seandepagnier]

... when you have 21 foot home built Wharram's sail the globe and race across the Atlantic (Cooking Fat), self righting may be a desire but not important to many in the industry.

21 foot wharrams are slow and heavy. I also think the more likely place to flip is where there are strong currents and contrary wind.

Often I am limited to 10 knots speed when the boat is capable of 15 or more. I just don't want to flip the thing over knowing that this design also does not have the buoyancy in the amas of newer designs. Maybe ok if you are hand steering, and I can sail faster in protected waters, but in sea state, the autopilot doesnt yet see the waves, so it can only react to gyros and a few other sensors. It could potentially hit a wave wrong at high speed and bury an ama. Even a human could struggle on a dark night, perhaps bright lights could be used to see waves?

Being able to self-right means you could really push a small multi harder and sail in difficult seas without risking it all. Agree or disagree?

 

[Paul Scott]

Interesting thought. I note that the GC32 is quite narrow. Could have been part of the equation indeed.


What could be the cause of this ? Anglo-saxo are prone to speak about the bad habbits of french sailors in term of security. Could the market of multihulls be tinted as such, that it would become acceptable to sail with a boat that can capsize, without additionnal cares, allowing the overall risk to be balanced ?

Active recovery (hull flooding, mast canting etc) vs automatic recovery (Gougeon low displacement hulls or possibly keel ballast)?

Monohulls that can capsize tend to be smaller in size (so active recovery there), although Open 60’s capsized enough that rules were re written. (And there was one Open 60 that sailed to race finish after she lost her keel!) To turn Old Sailor’s argument on it’s head(capsize it?), would it be ok with enough sailors to allow unballasted large Monohulls that could capsize and actively recover or stay capsized without outside help at the same frequency as multihulls? Ballasted monos can sink, granted, but more monos are being designed with buoyancy.

IIRR, Mr Brown’s capsize and active recovery in his G32 was pretty miserable, in much the same daylight rough conditions as Sean just described.

 

[seandepagnier]

Could a system of kites on both the hull and masthead be used to both orient the mast upwind, and then lift it upwards righting the boat again?

I prefer active recovery to automatic, although there is no real distinction since any mechanical movements can also be automated by electric motors and pumps.

 

[Paul Scott]

I prefer active recovery to automatic, although there is no real distinction since any mechanical movements can also be automated by electric motors and pumps.

Agree, and I apologize for not finding a better term than ‘Automatic’ to describe a system with no moving parts. Electric motors and pumps are taking over- we just installed 6 electric winches on our recent refit to accommodate our looming old age…

 

[rob denney]

Manual righting is likely to end in tears, automatic/self righting is a whole lot better but the best solution is not capsizing.

The requirement is something that works on all points of sail with no crew input, no electronics, and regardless of whether sheets are cleated, stood on or tangled and has no relationship with sheet loads or wave size. Ideally, it should be easy to reset (ie, no trips to the end of a flogging boom).

The simplest I could come up with is a wand with a float on one end and a T bar with a cam cleat on the other. The sheet is led through a block with a tail which is in the cleat. When the hull leaves the water (heeling or pitchpoling), or gets to a predetermined height, the wand angle increases, the T rotates and the cam cleat releases. To reset, the sheet is eased, the tail replaced in the cleat and the sheet trimmed on.

Works best on a proa as only one is required. Works best with low sheet loads (balanced or self vanging rigs) so the cleat loads are low. Only works downwind with unstayed masts so the main can weathercock without hitting the shrouds.

Knowing that you won't capsize is a major stress reduction when sailing in gusty conditions, strong winds or at night. It makes cruising a whole lot more enjoyable and racing, especially shorthanded, much faster.

 

[Russell Brown]

Here's some description of righting the G-32 that I wrote for a book chapter:

The G-32 is a narrow boat, so the masthead float has less "load" when capsized than a wider boat would have, but my two capsizes showed how little flotation is actually needed. The first was a test of the system in steady 25 knot winds. We tipped the boat over and the mast stayed on the downwind side, so the windage of the boat was pushing the float down hard. We were setting up the rigging for canting the mast so that we could right the boat and noticed that the float was much lower than when we had capsized and we realized that the float was sinking. We managed to right the boat anyway and water poured out of a the float for a long time. I later found large leaks in the shaft housing on this stock G-32 float that caused the float to fill halfway or more until the trapped air was all that was left.

My second capsize happened on a reach while racing in quite rough conditions with the same float (after the leaks had been sealed). The G-32 has a very unique rig, where the shrouds are in line with the mast and only the running backstays keep the rig from falling down over the bow (15 minute set-up time at the launch ramp is part of the reason).
My capsize was caused by an equipment failure on my windward running backstay which caused the mast to pitch forward to about 45 degrees, being stopped by a tangle in the mainsheet. The capsize was very violent because the mainsail was suddenly sheeted hard and the jib turning into something like a spinnaker.

So, in the first case, the float worked with it more than half-filled with water, and in the second, the masthead was somewhere out over the bows when I capsized. In both cases, I sailed away from the capsizes because of the float.

This blog post talks about the second capsize, but if you click newer posts there are lots of photos of building the float: Gougeon 32 Refit in 2015 http://gougeon32.blogspot.com/search?updated-max=2017-01-01T08:49:00-08:00&max-results=10&start=2&by-date=false

 

[cando2]

Nice to have you back again, Paul. After your February posts I came up with a few ideas you might want to consider, especially since I see you are open to a bi-mast arrangement. Tilt those sealed freestanding carbon masts outward 10 degrees or so and install the mast bases as close as possible to the outer side of the hulls. Once you get up to 45 degrees or so in a knockdown the outer sheer and mast should be starting to create floatation and righting moment in addition to a gradual loading of the mast eliminating the shock load, with or without a topmast float. The entire mast is being used for flotation and righting, not just the mast top. The 10 degree or so mast tilt should go a long way to preventing the cat from turtling and allowing the mass of the cat (not past vertical) to bring it back down upright. The mast base tube should be elongated crosswise at deck level to allow the masts to pivot upright at the dock. Mast tilt can be controlled manually with a 10 degree male/female radius wedge placed either inside or outside the mast. Perhaps the lower center of sail area using bi-masts may make it possible to get by with 8' beam, on boat lengths in the mid 20s, without ballast.

 

[kdifzero]

Manual righting is likely to end in tears, automatic/self righting is a whole lot better but the best solution is not capsizing.

The requirement is something that works on all points of sail with no crew input, no electronics, and regardless of whether sheets are cleated, stood on or tangled and has no relationship with sheet loads or wave size. Ideally, it should be easy to reset (ie, no trips to the end of a flogging boom).

The simplest I could come up with is a wand with a float on one end and a T bar with a cam cleat on the other. The sheet is led through a block with a tail which is in the cleat. When the hull leaves the water (heeling or pitchpoling), or gets to a predetermined height, the wand angle increases, the T rotates and the cam cleat releases. To reset, the sheet is eased, the tail replaced in the cleat and the sheet trimmed on.

Works best on a proa as only one is required. Works best with low sheet loads (balanced or self vanging rigs) so the cleat loads are low. Only works downwind with unstayed masts so the main can weathercock without hitting the shrouds.

Knowing that you won't capsize is a major stress reduction when sailing in gusty conditions, strong winds or at night. It makes cruising a whole lot more enjoyable and racing, especially shorthanded, much faster.

Hi Rob I always wanted to ask will proas self right "if" capsized? seem to recall a short video clip of I think it was you in a pool with a model proa self righting and just wondered would that also apply to the cruising proas you design?

 

[rob denney]

Hi Rob I always wanted to ask will proas self right "if" capsized? seem to recall a short video clip of I think it was you in a pool with a model proa self righting and just wondered would that also apply to the cruising proas you design?

The model is discussed on p2 of this thread. It could be used in the cruisers, but the lee hull would only be usable for storage. It's unnecessary if an anticapsize fuse is installed.