Trailerable Multihulls

Hi Phil

Hey, if there's water constantly dripping off my nose, and down the back of my neck....you won't see me out on the open deck unless I have to, or I am having a bloody great time. There's a balance to everything. I just see a lot of under 30 ft 'floating hotel' catamarans, and I start to think that the designer, or the sailor is missing the whole point of sailing. I'm a hippy with hair blowing in the wind.

 

Hello Phil,

Ahhh...yes, the pits are there. They are there because they have not been ruled out since I am still trying to decide.

I don't think the bench seats will work even without the cockpit. My 3-D visualization is not the greatest, but the only linear space or volume I will acquire by eliminating the cockpit is vertical above the berth and galley. I don't quite understand what it is you see. Only a re-design of the interior layout may produce the possibility and with 150 hours into the design so far, I'm not up to it. No way. I really like the layout because it has used every linear foot of length and breadth to the maximum. It took a lot of though and measurement. It is ....cozy but pleasant.

This is an excellent idea and I can see the floor folding up into the pit and folding down on to the beams, but if the pits end up remaining part of the design, then I can just slide them and leave the reinforcing strength between the spans. I started to draw a "fair weather" cockpit and I'm attaching it for comment. This also would slide and would require tubes and canvas to be fully enclosed. It.s a rough hand sketch and doesn't look like much, but I think it gives a general idea.

I have been pondering the steering quite a bit. Centerline or in the pits with wheels, and or tiller extensions to the center line deck. Now with the windscreen, tiller extensions from the pits look impossible. Im working on this.

Sheeting is a matter of angles and I think that I can work those out with the deck provided on the hulls. Working on this also.

I don't see how any water will get below. The lowest part of the cockpit is 2.38 feet above maximum waterline and then the companionway has another 1.1' height above the cockpit floor and it is all at approximately 50% aft of LOA. Even if an inboard wave 3.4' in height made it to the pits that far back, the pits would evacuate that water as fast as it boards and scuppers wouldn't even make a difference. This additional increase of displacement from shipping water are at their best position (50% +/- LOA) because it lowers the foreward and aft waterlines equally instead of the ends.

I am of the opinion that regardless of cuddy or fair-weather cockpit, the windscreens are on the design to stay. I agree emphatically that full protection from all elements under all conditions is a must. For me, the question to answers is whether I want heavy, solid enclosed protection with lots of windage, or can I meet the same need with minimum solid protection and then put up canvas where needed and when needed, without all the extra weight or windage. The fair-weather sailing pit attached creates no extra windage until the tubes are deployed and canvas is up...and that is only if the side canvas is up.

This is another great idea, but again, I don't see how to incorporate the bench seats or where. I can't even fold up the berth to a settee/berth configuration because the tanks are below.

Thanks
J

 

Hello Richard,

I agree that they are quite flexible. I'm not aware of any marine material for which they do not specify however, including the netting.

Yes it does sound like it, but you will find that the Register of the Ukraine classifies that definition as a category 3. I'm not sure they call that category offshore rated. Is it? At 56' Loa I would hope she is.

Exactly. I always thought that many small designs could do it and didn't understand why it wasn't done. If you can work on her and get her offshore rated by design, that would be great! Now you can get offshore with significant confidence. Right?

I find that the governing agencies tend to be more concerned with the "global" design as it relates to structure and seaworthiness. If it has anything to do with those criteria, they do usually call out a minimum. For example, the crash bulkhead must be a % of Loa aft of the stem and hatches must be designed to open a specific way or tanks must be secured or motor mounts must be this or that.

Comfort is usually left to class rules and I'm sure the NA designing to a class rule, would undoubtedly design to both and those rules usually call out so much minimum sitting room, headroom, stores and many times minimum weight. If it exists on any boat, it should be built to cretain standards but it does not mean that it "needs" to be aboard. A good example is the overboard discharge head as you have pointed out. Just about any will do, but plumbed, it must meet standards to ensure that they are "locked" within the 3 mile limit etc and contain a holding tank etc, but what would stop an unscrupulous skipper from dumping his potti right at the dock?

I have yet to see a directive concerning sail area. The sky is the limit. But, there are stability criterias and they are the result of many things which includes sail area. I believe that your AtCat may have the ability to become Category B but I'm not sure it will be as easily accomplished as you indicate.

Wow. Almost GUARANTEE? What have you heard or learned? Care to share? If you cannot identify a source that can demonstrate the rating, then you're saying the same thing that everyone else has been saying.."almost guarantee" with nothing else to prove otherwise and, I can continue my contention that "the TR27B will be the first and is the only trailerable catamaran that will be rated Category B right from the design stage", because none other exists to date.

Disappointed? Burst my bubble? Get for real. If I do find the design I would be happy as hell in knowing that this underserved portion of sailors have a reason to look no further. My disappointment would come if those more experienced than I that have an edge in getting the design rated from plans very quickly steal my idea and work to beat me to it. That would be disappointing because if they asked, I would share it.

Thanks
J

 

OK J, I've been searching for hours and haven't found what I believe are truely trailerable offshore cruisers....just a bunch of inshore trailerables....and the ones that look vaguely capable of being offshore, don't show much specs, so finding one that proves to be category B is like finding a needle in a hay stack.
If you can disprove the ones already mentioned in this thread, then MAYBE you are on to something

If my rear hatches are 'illegal' by cat B standards, then screw the rating. If they are not illegal, then as you say, I could just tell my NA to "make it happen". You've got 2 years before my boat becomes a possible competitor for the title.
(not taking it too seriously, but hmmm.....offshore rated does sound good)

All the best

 

Is the Cat-2-fold considered offshore?

Kurt Hughes designed the hulls while the client patented the folding connectives. Is that design considered offshore? The designer is now working on a 28' version of the original design.

 

Ahoy there Richard...

It is difficult and even more so when they are "made to sound" as if Category B and then you have to go through the whole disqualification/qualification process. Bottom line however, is that producing the rating will seal the deal. I still can't believe that no one has done it, even if the market didn't call for it whenever they thought about it.

I believe this has been done already. I have kept an open mind about the designs offered as Category B and have in their favor attempted to qualify them as such, but two truths remain..

1. The Category B rating has not been produced by any of the designs,
2. The initial challenge is that designs be produced to disprove my claim, not the other way around,

Neither has occured, therefore, my claim stands on all counts, that a design does not exist and that mine will be the first...until either is disproved.

That isn't a lot of time. But the only deadline I'm racing is my own. There is no possible way after all this time and posting that the idea of a trailerable rated catamran from design cannot be attributed to me being the "first" person "to take action" to fill the gap for those avid catamaraners that would like to feel confident in exploring because the design is rated.

Why not serious? Wouldn't you feel wayyyy more confident knowing that your vessel can endure F8 winds and 4 meter waves without breaking up or breaking her back regardless of where you sail?

Okay...she will require some beef (more than CPA driven designs currently available) and, she will need to be heavier than usual so that she is bulletproof and built like a tank for such a small design, but dammmm... 40 kn winds and 13.1' foot waves is no damn joke for such a small Loa and beam.

I think that with current materials and the advancements made in multihull form and design, it can be done and still produce a good performing, seaworthy design, (as long as the CPA's stay out of it), albeit with significant difficulty for my person anyway.

Update:

Worked on the cuddy to get a general idea. Kind of overworked the top a bit but the idea is to have two openings to walk into the cuddy before sitting down or entering the forward cabin without crawling all the way. The headroom is 4.1' and in the cabin it is 3.2' with the hatches closed. I can see myself sleeping in the cuddy cabin, but not sitting. An ecellent berth, a horrible salon. All seating will be outboard except the helm which is on the centerline and the rear openings allow entrance to the aft hull cabins when the cuddy is folded into the pits. Obviously, full enclosure would mean canvas.

Picture 19 is the TR27B on her waterline with the windshield. Gained some more windage area there. Not very good.
Picture 20 gives a perspective view of the cuddy in service.
Picture 21 denotes the cuddy slid into the cockpit and shape.
Picture 22 is the half top view. I made the sole green to show the openings. Looks kind of weak and may need serious re-inforcement.

All in all...I'm not exactly pleased. I like and understand the importance of the outside area for enclosed seating. The cuddy cabin is a total waste. Any body have any thoughts on this or in comparison with the fair weather center cockpit? Should I attempt a combination of both?

Thanks
J

 

Hello Rapscallion...

I cannot even tell you how much I like that design. It is without a doubt a huge leap forward for catamarans.

It is my understanding that the hulls were already designed by Mr. Hughes and the client chose them for the folding system. In my mind, I would think that the 36' that Mr. Hughes designed would fit every criteria for category B and possibly a category A but there isn't enough data on site to study it nor does Mr. Hughes claim that the design or any model built was designed specifically for or carries the rating.

The Cat2Fold is not rated, nor does it carry the rating even if the Hughes hulls may have the rating, which I do not believe it does. It definitely isn't the product of a design that started as a rated offshore trailerable catamaran because the original Hughes hull was a bridgedeck "waterlocked" version. However, if the Cat2Fold owner can demonstrate that he received the rating then he would disprove my initial claim and I would not care whether the design is the sum of non-trailerable designed hulls and the incorporation of out of design components.

Perhaps it should be suggested that the 28' version be rated right from the design stage?

I wissshhhhh I had one of those. A little big for the trailering concept in my opinion, but that folding mechanism is insane. One is up for sale right now at $195K.

Perhaps it should be suggested that the designer design the 28' to acquire the rating?

Care to suggest on the current work in the thread?

Thanks
J

 

Mast/Beam Calculations

Hello to one and all...

Well...the first mate gave me a stern talking to today after she pointed out that I am spending lots of time "designing" and "foruming" while there are things to do about.

Soooo...I took my lecture and have a list of some things to do around here before I start my boating season, but, I gotta keep up the fun because I know that bets are being taken by my forum brothers and sisters that I will or will not endure and succeed.

I would not put my money on the nay sayers.

J has been working. I had some trouble with cut and paste and the calculations left more questions than answers since the rig is not my strength. Any help with the questions would be greatly appreciated.

I have attached the mast and beams calculations and specifications. All are calculated in cantilever but the rig will still get 2 stays outboard and aft just in case.

I'm researching the motors and have almost completed the hull scantlings.

Thanks
J

 

Hello J

I think I would also have confidence in the weather forcast, my eyesight, emergency beacon, redundant beacon and a life raft....all of which will be on my boat, regardless of whether it is category B or not.

I like the idea of making it a true offshore vessel, but if it means adding extra weight so I can't take 8 people, then I will not make it offshore.

I also like the idea of buying a home on one of those man-made canals I've seen in LA. Just launch your boat from your own personal boat ramp. No need to collapse or demount the boat. Man that sounds good....but now I am just dreaming I think. Megabucks.

 

Is this for a mast or beam?

Hello JCD

Are you calculating for a mast or a cantiler beam? The typical cat beam is a simply supported beam and so is different from a cantilever. If you want to work out the dimensions of a mast use Yades notes in the mast compression thread in the sailboats forum.

The mast you have sounds really heavy. I am pretty sure my 38 footers mast is an IM20 section from Allyacht spars - 200mm front to back, about 150 across. If this is a mast you will need 95.7 kg x about 5.5m to lift it (bare section) = about 526kgm. Cats-paw's present mast is a hefty push at 40 kgm (bare section). You are not going to want to get this thing up and down often. I would want a crane.

I would hesitate to do mast calculations - I really think that there is a lot of empirical design to this. Again - go have a look at similar boats and see what masts and beams have proven themselves over the years. Mast compression loads are vital for beam engineering.

I have reverse engineered a Seawind 24 design as these have worked well for a few hundred boats. It gives me good background on what works and has been proven. I also reverse engineered lots of other cats too and there was a wide variance in stiffness and strength. This would help with your engineering.

cheers

Phil Thompson

 

Don't worry too much about numbers

One thing about peace of mind - I think it is important not to get to technical about the design without carefully considering current design trends. You may forget something that a experienced designer includes as a matter of course.

A case in point - In the 80s a cat (Richard Woods knows this one - he sailed it across the Atlantic - Rush) was sailing with a well designed laminate (Crowther) But the silly builder had not installed the interior furniture.

The boat got hit by a blow and split the hull/deck seam. It filled with water and a bloke died. The laminate was strong enough but the boat failed due to oversight of an integral part.

I am sure ISO is based on empirical knowledge as well as theory. Make sure you follow standard empirical concepts as well as the theoretical ones. Keep looking over sturdy cats that have crossed oceans.

In my case I would prefer to have a boat designed with large amounts of proven sea miles behind her designers concepts rather than an industry standard. Having both would be best.

cheers

Phil Thompson

 

Hi Phil.
Good advice. This has been my strategy:
look at others....forget the numbers
I will get a NA to do the final engineering.

J
obviously you have a keener interest in going into further detail. How far do you intend to go by yourself? Do you hope that a NA will be required to do nothing more than a final inspection...or do you want him to be an integral part of the final development?

If someone else is going to go through all the math anyway, then you can afford to relax a little. If you are using a bermudian rig and 2 hulls, then you will never be designing a truely new invention, so just some crude weight estimations is probably good enough for now. You should be able to make adjustments to the weight when you talk it through with the engineer, by adjusting some non-critical areas to compensate for final changes made to beams and mast etc.

I can see this scenario:
You spend ages and finalise a very nice looking design....and then the NA/engineer says...."cool...but what about this and that....do you mind if I change this and that and that and this...."

You could save a lot of time by staying loose and flexible at this stage.

Think "general layout and function" more than "beam thickness and peak forces".

On the other hand, you are probably almost a NA, and it looks like you are having fun, so what the heck...do the math....but be prepared to do it all again.

You have been given a wise and balanced (and long-winded) view from a person with virtually no experience.
Lord Richard has spoken.

 

Just been reading the pirate thread. I am officially no longer interested in offshore cruising. My boat will probably remain a party boat. And I won't be partying in the Carribean either.

 

Ohhh, Richard, dont be such a ???? words fail me... There is Australian waters, NZ of course, and up through Melanesia & New Caledonia, Kiribati (pronounced Kiribass) and a lot of other sailing to be done...

Or is it "unofficially" you will be sailing, but not everywhere... Don't go to USA. I hear there are pirates on the roads over there, who will shoot you for minor traffic infringements? that game is called "drive-by-shooting" or "road-rage"...

 

Ahoy there Richard,

You are a true sailor...the boat is the means...it is my belief that you will be a very conscientous skipper. Good for you. Don't forget PFD's.

In this case, the "minimum" extra weight will be required because it is a multi-hull, but as you have pointed out, the Category B will require extra because it will encounter greater forces offshore.

Dream on Brother...it is good to do so...then take steps to make your dreams come true. I will remain hopeful that you get that little home in one of the canals in LA with your own boat ramp and wish you nothing but success for all your endeavors.

Update...

I'm calling out the motors. My recommendation is the F2 or the F4 with a 9.5" propeller. Weight is below moderate and they are quite reliable. My estimate with 24 gallons of gas, she will run for 20 hours burning approximately 1.2 gph at 10knots for a range of 200knots. Throttle her down to hull speed and you can add another 100knots to the range.

Thanks
J