This is a new thread to expand upon the question by thouse about "Mast Flotation."

Some cats, like the Seawind 24, the Stilettos, the MacGregor 36, are not exactly "cruising multihulls" and not exactly beach cats, but share characteristics of both. They have trampoline decks, spartan "living" accommodations and are trailerable. A beach-cat can be righted by one or two people using sheer people weight. If a true cruising multihull capsizes, it is probably going to turtle, and it is going to take some major outside assistance to right it. But cats like the ones I mentioned are still in a range where turtling can be prevented with proper masthead flotation, and the boats can theoretically be righted by mechanical means without outside assistance. And if they turtle, with or without masthead flotation, it is interesting to consider possible ways to get the boat back on its side so it can be righted.

So my questions about boats in this category are:
1. What is the best way to prevent the boat from turtling if it capsizes?
2. If it capsizes but does not turtle (thanks to #1), what are ways to right it without outside assistance?
3. If it turtles, how can it be brought back to its side so it can be righted?

If anybody has references about work that has already been done or practical experiences that people have had with any of these questions, please share.

Mary,
The website for the Reynolds 33 which fits your description of non-beach/non-cruising cats advertises that they have addressed the capsize problem with a mast float and shroud extenders to allow the weight of the upper hull to right the cat. Interesting, though, all the pictures of the boat on their web site don't show this mast float and it seems as if they raced it with much success, but without the float. It would be interesting to know if the builders/designers have ever tried to right the boat in the manner they describe.

These boats are very interesting in that they offer very fast performance and the ability to do non-stop distance races. They do fly hulls and therefore are suceptable to capsizing (more so than a heavier cruising cat). The issue of righting certainly needs to be addressed and may have positive implications for beach cats.

Hi Mary

There is a good article on multihull seaworthyness.
http://www.steamradio.com/JSYD/Articles/NESTalk.html

It is difficult to address the capsize aspect without rethinking and redesigning a large cat or tri in total context. -
In attempting to fix one problem ,--say adding a large mast float ,--you just caused 5 more major problems in claiming it can right a boat ,-Stay strength ,-mast strength ,-mast base ,-fittings and hardware ,---
all prone to fail in extreme conditions in wind alone ,-now add huge seas and water forces . Worst of all the weight windarge of the mast float increases moment and the likelyhood of capsize , counter productive .

Long ago worked out a larger cat design for fun and addressed the capsize righting problem .
-We take monohull rigs and place them on very different catamaran configuration platforms with very different characteristics and expect them to work well --??

-A solution ,--again 20 years ago ,-designed was using a basic A FRAME support in place of stays . We see a very simple version ,-similar rig used in small scale on the catyak 12 design .
The A Frame has numerous structural advantages , triangles being extremely strong and stable . Many are used in easy mast stepping and for larger masts .
The A FRAME could of course be designed in a much more sophisticated configuration ,-arodynamic C F foil shapes -pivoting base ,etc.
Without going into alot of detail ,-the basic righting concept from inverted capsize is bows over sterns using the A frame mast rig as the lever arm. -It would be lowered beyond the inverted hull bows, an inflatable or Zodiac could be attached to the top.
Using a deck winch the volume of bouyancy along with A frame strength and stability ,--per Jakes engineering diagram ,--has the capability required.
This has to be combined with proper design --{see article}
Along with a refined A frame rig concept .--Something very different -but really needed for larger cat design .
The other important design feature was the open transom -stern area reserse sheer line design we now often see on larger cats with open transom and boarding ladder. The Benautieau designs are typical ,-very beautiful cats.
This along with fuel tanks water ,-engine all being located far aft . In some a partial water tank ballast or seperate stern bulkhead and flooding aft compartment may be needed per stern design . Reasonable Beam to L in design is also needed.
This allows the stern to submerge partially greatly reducing the center pivot point , bringing it closer to the water surface in turn requiring much less force in the righting equation.

Built an angulating rig as an experiment using this type of A FRAME support --This version -configuration added the tilting
feature though on a 20 ft cat , righting was not the idea ,-lift from the angled mast and speed was.

The mast supported by forward A FRAME support was stepped on a traveler on the mid crossbeam . As you pulled the mast base towards one hull or the other the rig would angle back and to windward per geometry . The A FRAME base was approx 5 ft forward of the crossbeam -mast location.
A noted designer builder Chris White designed a similar A Frame rig configuration on a proa at that time .
A fun experiment but not practical . Similar A FRAME configurations are however very practicle for cat design and should be developed with this righting system in mind .

Fun stuff --hope this helps -
Carl

Carl,
It sounds like you are talking about cruising cats. Obviously, a masthead float would not be practical for boats like that (and it would be a very rare thing for one of them to capsize anyway). But the MacGregor 36 masthead float is not large, not heavy, does not seem to add to heeling moment, has an aerodynamic shape, and it has been proven to work to prevent turtling. I don't know why some people discount masthead floats for these "big-beachcat-type" catamarans as being not practical, when they quite clearly ARE practical based upon real world experience.

The MacGregor masthead float was made out of fiberglass. If someone is concerned about weight aloft, make it out of carbon. Heck, if they can make a whole mast that weighs 40 pounds, you would think they could make a hollow float that would weigh no more than a pound.

If there is a concern about it causing drag and slowing the boat by some miniscule degree, why can't the designers and engineers work on designing a masthead float shape that would either have negative drag or would actually have upward lift and/or forward lift. Wouldn't that be a great challenge? -- to design something that would improve safety and also improve performance? I can even picture someone designing a masthead float that articulates to stay level as the boat heels, so that it continues to provide lift to the top of the mast.

Masthead floats are not popular as safety devices, but if they became the "in" thing as speed devices, we would have a lot more boats saved from turtling.

As you always say, Carl, it is fun to think about these things.

what about a masthead float that acts like an endplate to prevent air from spilling off the top of the mast, a lightweight saucer or symmetrical fin perpendicular to the mast.

Mary,

There is an extensive discussion of this subject relating to trimarans going on on the F-boat list right now. It started over the weekend with Ian Farrier and a bunch of other people swapping ideas back and forth. Right now they are working on putting an airbag on the top of the mast that will inflate once it hits salt water. Most people seem to think that a fixed float would need to be too big to work well.

Drew

How about a 41' x 11" x 5" carbon tube for flotation? That is what my RC-27 has. The problem is, som many riggers want to cut holes in the tube to pass halyards and other "things" through. My mast is sealed AND actually has a foam core between layers of carbon. While it may not be quite as effective as a float in preventing capsizing, a mast of sufficient volume should impede the process of turtling.

Mary:

It mostly has to do with the "finished attitude" the hulls end up in. If the boat has gone fully turtle (Mast straight down) then the most common system for righting the boat is:

Cut away all halyards
Drop or cut away the sails
Submerge one of the hulls by flooding the boat by opening seacocks
Pull the boat with a frigate or tug boat slowly to an angle where the mast is well passed parrallel the water and then inflate expansion bags with CO2 cartridges that were placed in the hull prior to the final step.
Last but not least get the gunwhale bilde pumps going. Drag to a yard with empty hulls and crane out. Save what you can. Buy new sails. Replace all standing rigging. Wash out underwear. Go back out sailing.

Mark Michaelsen

Drew,
Yes, I would think a fixed masthead float would not be practical on a trimaran. For the Farrier tris, is it possible to fold in the amas once it is capsized, and would that make it easier to right? Can they be folded when the boat is turtled? I'm just asking because I think my husband wants one if we ever win the lottery.

Mary,

I am afraid that I am not an expert in the subject, in fact I have just been researching tri's because they look like fun (but then there is that COST issue). However, if I understood correctly, the probability of succesfully unbolting the ama and getting the boat to right iteself, as opposed to breaking itself (and you) apart, in the kind of weather and seas that one needs to capsize a tri is really quite low. The one thing that people did discuss was to flood the leward ama, lowering the boat and then it might right itself. But this only works with a capsize, not a turtle.

Drew

what about a float that could be inflated and attached to a spare halyard. then, you just crank in on the halyard and raise the mast to the float.

Hi -
good thread ,-always been the major problem with large cats and tris and why many monohullers look down on catsailing deeming it unsafe .

Multihulls are safer in most regards ,-positive floatation ,-not sinking if rolled over as many monos will with their lead mine keels to pull them to the bottom once evan partially filled with water. -being the biggest single advatage over them . Multihulls are faster ,-can run up on beaches if designed to do so, and can float if inverted keeping crew safe for days if needed and designed correctly.

As boats or most anything scale up --become larger,-- there are a whole series of compounding engineering problems to address .
Interesting ,also --if one doubles the size of a cat design ,--say from 18 ft to 36 ,--is the 36 faster ?? ---NO often not as fast . ! Why ,--again scale and measurement we use does not corespond in direct proportion to the engineering realities .
We use math ,-but different units of measurement to form our comprehension ,weight units of measurement , strength of materials ,-stress in bending aspects,--adhesive and expoxy .f g strengths ,-metal strengths and fitting ,--hardware .- basic scantlings descibing boat construction in numerous forms ,--metric -imperial measurement ,-weights ,-volume ,-buoyancy ,-moment ,-S A forces ,---none of these corelate without applied engineering calculation relative to one another . These do not uniformly scale with size ,---they are all very different .
Going from scale models to full size the --law of mechanical similitude is applied . ---Here is an example applied to planning craft ,--- http://naca.larc.nasa.gov/reports/1936/naca-tm-795/

-Getting back to the speed question ,-a 36 is often slower than the 18 at half the size ,--why ? --
For many of the same reasons sticking a huge mast float or airbag at the top of a mast does not work ,--why ?

Many that build small scale models ,-be it sail speed trial models , then converted to large scale models fall apart of break up ,-like the resent double masted cat design for the RACE round the globe ----why ? - Scale ,mechanical similitude ,-engineering strength problems that increase rapidly and compound with size disproportionally with other design features that do work in smaller scale . --
These 120 ft cats had to solve these types of engineering problems which had never been directly tackled at that huge scale ,--They were experimental to some extent .--
Recall the bulkhead crossbeam and other related stress -structural problems during the RACE .This is HOW WE LEARN grow and achieve ,-the benifits in future engineering and design applied to help create future safer faster craft far outweigh the setbacks and problems initially overcome in these fantastic cat designs raced round the globe .--
Can't wait for the next one ..

--Added for larger cat design . --
Along with the A FRAME rig --per post above ,--the design had larger bow sections above the sealed crossbeams and an extended aft crossbeam hull section as well again extended above the crossbeam . When inverted the design still floated on the extended inverted hulls.. Simple concept ,-basically build hulls with entended rounded tops for headroom and place crossbeams and hatches below , --add the open stern design features .--This type of design is safe when inverted indefinately and could be powered and brought into port ,--along with the righting system described .

now about this rating system ,-- ---
have fun
---Carl

Check out this article on the Farrier site about righting capsized & turtled F-boats:
capsizearticle

With a tri the biggest pain is a pitchpole. The problem is that the top of the mast is not parallel to the water but, without floatation, aimed to an angle under the water. An unsealed mast will simply begin to fill with water, becoming heavier and compounding the problem as the mast sinks to a lower angle. You're screwed at that point.

The only answer I could come up with on my tiny tri (after a pitchpole experience) was to stuff the hollow aluminum mast with foam noodles. I figured the expanding foam would turn to dust after a couple of summers. We then tossed the mast into my test tank (my swimming pool) and my wife and I could sit on the mast without it sinking.

Then, I re-sealed all the existing rivets on the mast with silicone. Not "Goop". Goop will turn to powder in a couple of seasons of Florida heat and sun. I also stuffed jumbo noodles into the beam (17' wide) and into the amas and also placed four of them as far forward as I could lash them down into the bow of the central hull. Next time, I hope the mast and beam will float higher which will give all my 150lbs a shot at righting it by hanging off the transom in typical grunt-and-pray capsizing/pitchpole fashion.

From experience on my small tri I believe the the CO2 idea is a super solution. I think I now have a use for those surplus CO2 inflatable PFD's that I have. I can place one in each ama bow with a cable attached to the ripcord on the CO2 bottle. I have to figure a way to keep them attached to the ends of the bows once they're inflated.

MULTIHULL SEAMANSHIP by Gavin LeSueur covers this topic in pretty good detail, esp for trimarans

sea ya
tami

Mary,

I've been discussing anti-turtling devices and righting techniques with the Catri designer one or two years ago and also followed the recent discussion regarding mast floats in the F-Boat discussion group.

The following is a summary of what I consider to be the concepts to be followed for the anti-turtling device:

1-In a big and wide multihull a sealed/floating mast does not help much because the relatively thiner mast would have to sink A LOT before providing a reasonable righting torque. This is especially true in wider tris.

2-An efficient mast top float for big multihulls would be bigger and clumsier then one designed for beach cats. This is due to scaling, as Carl explained earlier in this thread.

3-An airbag is NOT a feasible solution - they are activated by explosives and destruction of the mast top is a real possibility, while reinforcing this area is not desirable (weigth). Since in our case the time lapse available for activation is a lot bigger then in a car crash, there is a better solution.

4-A water activated inflatable masthead float resembling a water activated life jacket (but for the shape and size) seems to be the best solution.

5-The water activated sensor must be protected from the rain.

6-The water activated masthead float should be stored in a flat or aerodynamic package, attachable to the head of the mainsail or its halyard, so that it can be removed with the mainsail/from the mainsail. This increases durability and simplifies maintenance.

7-Speed adicts could possibly try to separate the bottle of gas to keep it on deck. This would reduce the weight aloft, but there would be a tube all the way to the top to complicate things. I tend to prefer the simple, self-contained, removable unit.

8-The device is simple, all parts already exist in the market and are relatively inexpensive. It increases safety and greatly reduces the costs and difficulties of recovering from a capsize. The only mistery is why it is not for sale already...

Cheers,

You guys really need to take a look at some HPA systems, commonly found in use in paintball guns. They are small 68cubic inch fiberglass/epoxy wrapped cylinders with integrated regulators. They can hold up to 4500psi currently, and output as little as 300psi. Using one of these to inflate a mast bag would be simple. I would know, I used mine one time to blow up an inflatable chair. Lets just say "blow up" is the appropriate term.

Righting a Stiletto 27 is becoming a pet interest of mine.

An interesting article can be viewed at:
http://www.users.globalnet.co.uk/~fsinc/yachts/slade/page2.htm

http://www.messingaboutinboats.com/archives/mbissuejuly01.html

http://www.f-boat.com/pages/background/capsizearticle.html

I also have an old Mac 36 owner's manual of how they recommended righting the boat in a capsize.

The process seemed laboriously tough in the inner bay....and more than challenging in the open ocean and conditions which probably dumped the boat.......but when you're upside down...I guess one would have time to sit and think, time to mount an attempt to right the boat or time to wait for someone else to come help....

If anyone is interested in looking over the old Mac 36 owner's manual, give me your email address and I'll attach the acrobat file to my response.

Tom H.

Tom,
I would like a copy for my files. I have always been mad at myself for not keeping a copy of the manual from our Macgregor 36 when we sold it. Please send it to [email][email protected].[/email]
Thanks!

Mary,

I can't seem to get that Mac 36 attachment to go to you without an error message from the cyber king.

What I get back is as follows:

The message that you sent was undeliverable to the following:

[email protected]. (553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1))

Earlier this month, I sent it via email, to a friend, without this kind of message coming back.


Got any ideas... ?

If we can't get the acrobat file to you via cyber space...I could print it and send it snail mail....

Tom