A New Beach Trimaran

[Chris Ostlind]

OK, guys... I stuck it out there and competely revamped a design that I had been kicking around for a few years now and came to some very satisfying conclusions.

Here's the boat... Essentially, this is a beach style trimaran that is capable of near shore coastal cruising (anywhere, really, that you'd be willing to take a large fast beach cat) Not Blue Water, please, save for short jaunts in known conditions.

It is designed for easy setup and take-down and once taken apart, fits easily on any beach cat trailer that is hefty enough to handle one of the bigger beach cats (Nacra, Prindle, Hobie20, etc.)

Here are the specs:

Cardiff 21
Sport Trimaran

Specifications

LOA …………….. 21’

BOA .……………. 15’ (with amas)

BOA …………….. 32” (vaka hull)

Draft ……………. 12” (board up)
52” (board down)

Displacement … 1200 lbs.

Sail Area ………. 216 sq. ft. and up depending on desires of owner

The boat is designed for strip building in Western Red Cedar if you are in North America, Pauwlonia if in OZ and who knows what if you are anywhere else... (to be determined on a case by case basis if you can't get these woods)

It's a simple, form driven stripping process for each half hull along the longitudinal line of each hull. The interiors are glassed, they are joined together with thickened epoxy with bulkheads in place and then glassed on the exterior set in epoxy. Hatch openings as suggested.

The rig is from a harvested beach cat from H16 to H20 in size (depending on the thrill quotient desired) which also supplies the sailing hardware, the trailer, rudder and a whole bunch of other stuff. The board can be either a centerboard style of solution, or a daggerboard for those who are into limited compromises.

The amas and akas are bolted together with the tramps in place. They fit into built glass tubes on the main hull and are pinned in place. The ama'aka structure is further stiffened with waterstays from the ama/aka junctures to the main hull above the waterline. The tramp is hooked to fixed pints on the integrated hiking benches and tightened-up for a solid, unified structure.

Raise the mast with the winch handle on the trailer and a gin pole and you are in business in a flash.

The traveler comes straight off the donor cat, so there is total compatability with the hardware.

The boat will weigh between 500 and 550 lbs. all-up, if one is fairly judicious with the epoxy and will accomodate a nice bit of kit for a camping weekend on the water with a buddy, or even someone special.

I expect some fairly lively performance with this boat, whatever the rig and it will be an easy in, easy out, affair at the chosen launch ramp or beach.

I'd love to hear from you guys about the design, any limitations you might see in the details, such as they are, and just plain commentary from those who know about boats of this type.

Best, as always...

[Gary Baigent]

It's difficult to fault the design and anyway you end up with subjective viewpoints ..... which are just that. However in a beach tri design I think you could simplify, strengthen and lighten the design by not having a cockpit and perhaps make a lower wooded boat, reducing freeboard. But then my orientation is towards simple, high performance by reduction of size and materials, a minimalist approach - and that is not every bodies cup of tea. However on a daysailer you are going to have to take some cool weather gear because you are out in the elements perched on a trampollne so the "shelter" of the cockpit is not going to make much difference. But I can understand that many people like the conventional idea and illusion of a cockpit's safety. Whatever, the design is attractive and neat and is going to be an adequate to high performance boat anyway - so good luck with the design.

[rwatson]

I built a trimaran about that length years ago, with a cockpit - but much uglier.

I suggest you make the cockpit self draining - that was always a nuisance and a danger in decent waves (like off the beach). It also makes outdoor storage less problematic - it wont fill up with rainwater.

Likewise, a bit of of a splashguard on the foredeck ( or maybe a moulded foredeck)

The flat seats along the side will tend to drain splashes into the centre hull. I found curved "seats" more comfortable to sit on, and if you design the lip to empty before the edge of the hull, it will make a much drier boat.

You havnt drawn a net out near the bow. I found the narrow foredeck a real nuisance, and until I put a bit of netting up there, a bit hazardous.

It might seem a bit impure - but provision for a small outbard will make the boat have even more useful. On a windless day you can get back to port, or even go fishing when there is no wind. Put the motor at the end of the stern, not hung offcentre from a beam. The motor will be "drowned" by waves if it isnt behind the hull. The trimaran made a much better fishing platform than small, narrow rocking "tinnies".

The other thing I found usefull, was a bit of a "wash line", a slight horizontal ledge just below the gunnel, to deflect bow wash away before it sprays up on the crew.

I think you will find the "screecher" a complete overkill on a small boat this size - I dont even think Tornadoes have anything but a jib, and with smaller ama's, you could easily be overpowered.

See if you can figure out a way to keep the mainsheet traveller out of the way of the tiller and extension. I ended up running the mainsheet traveller on a steel cable, so the tiller could pass underneath the traveller. Having to backhand the tiller after every tack was a real pain.

Finally, a self tacking jib was a great asset. It made single handling a much easier job.

I look forward to seeing some pictures of it being built. Good luck

[Doug Lord]

Anyone considering one of Ostlinds designs should consider this from no less than Ian Farrier: Post #91
http://forums.sailinganarchy.com/index.php?showtopic=81148&st=50&#entry1981010

[Fanie]

Chris,

I can confirm what rwatson mentioned. A foredeck and the netting to the bow. I also prefer the ama's rather too large than too small.

Fishing (thanks rwatson ;)) from such a rig is something to consider. I myself is not interested in having the fastest rig around, just the fastest fish on my line :D Personally I think there is a huge market for sailing fishing rigs, just nobody provides for that. Keep in mind fishing is the most common sport in the world, fuel is expensive and not everyone buys a pesky ski-boat which is heavy and an unsafe outfit in my opinion. If the option is there, many will go for it.

Easy to use sails and a small outboard for the odd no wind conditions. Also consider a trolling motor. Perfect fishing rig, cheap to maintain and use, easy, spacious, safe, go anywhere.

Nice hull shapes.




Dough, nasty fall-out there, good language expressions too, sounds like me trying to be a sailor :D

I don't think Chris posted here with anything other than ask for opinions on his mind. I would like to honour that. The debate can continue in the other forum, and has no bearing on this one.

[Chris Ostlind]

I guess this means we're not going steady anymore... is that right, Doug?

[RHP]

I don't think Chris posted here with anything other than ask for opinions on his mind. I would like to honour that. The debate can continue in the other forum, and has no bearing on this one.

Hear hear.

[Doug Lord]

I don't think Chris posted here with anything other than ask for opinions on his mind.
-----------------
Fanie, I think he posted with the idea of selling plans and that makes Farriers comments very appropo......

[Chris Ostlind]

-----------------
Fanie, I think he posted with the idea of selling plans and that makes Farriers comments very appropo......

Doug,

While I do sell plans for some of the boats I draw, it is not the sole motivation for my design work. Selling something is rather far down the list, in fact. The Cardiff was presented here to gather input from the assembled readers who have a sum total of knowledge far greater than that which I will ever attain. I asked for their input because I wish to explore the potential of a given design genre such as the Cardiff and come to a much fuller understanding.

Your comment above, about the selling of plans, would suggest that my efforts are driven by the desire for money. I would suggest in return that if money is the singular energy source that drives a person to design, then they are in for a very rude awakening in their quest.

I've been a professional cameraman in the fields of still and motion picture work for more than 35 years, now. If my desire to create imagery would have been inspired by the pursuit of cash, instead of the inner need to create through the use of the tools in the medium, then I would have failed at my quest a long time ago.

I have been fortunate to be able to work at the thing I have always loved to do and, yes, make a dandy living from the process. But, if I were to be driven only by the sketchy income potential when I first started in this career, then my craft would have suffered and I would have been quickly left for dead by those who would hire me to visually represent their needs.

The same is true for working in the field of boat design, Doug. The financial rewards are typically limited, but the emotional satisfaction of creating boats that not only work properly, but also have an aesthetic feel that brings joy to the eye, are what motivates my entry into this area of work. One key to the fulfillment in that fashion is in the asking of others... and then the listening.

[Doug Lord]

Money is not the issue: the issue is inexperienced people being taken in by nice renderings and winding up buying plans from an exceedingly inexperienced designer: the blind being led by the blind. This subject has been
covered in great detail on the boatdesign forums. There is evidence both here and under "Sailboats", and on Dinghy anarchy and Multihull anarchy that you are ,in fact, using the forums to PROMOTE your designs-and I feel that is wrong-maybe dangerously wrong in the case of a KIDS boat!
Nothing is stopping you from building and testing your own designs-but using others as your guinea pigs doesn't cut it. Ian Farriers experience with you IS relevant for that reason alone.

[Chris Ostlind]

Regarding your insistance to go off topic in a very nicely communicated thread up until your totally unnecessary intrusion, I refer you to Post #37 of the New Cabrillo Skiff for Kids, thread.

And I quote:

"Doug,

As the person who started this thread, I'm going to have to ask you to put your comments back on topic, or please excuse yourself from the thread. You have made your simple foray into the netherworld as the water boy of record. Those so inclined, have already read the post from Ian Farrier and moved on with their own opinions.

It's now time to move back to the topic of the Cabrillo Skiff for Kids, specifically, or even any other kid related entry level boat that have a direct relationship to the boat in question.

How about you observe some Forum decorum and let this opinion of yours fall into whatever place you put lost thoughts?"


Anyone reading this thread and finding Doug's recent antics to be well beyond the expected behavior on this Forum... please avail yourselves of the opportunity to report said infractions to the Moderator.

There's a clean little button on the upper right hand corner of each post which allows you to make a written report of disruptive behavior directly to the Owner/Moderator. Since Doug has not responded like a gentleman to a kind request to let this type of hostility go, I would be very grateful if you would do just that.

[RHP]

Guys, life is far too short to get diverted by these needless attacks.

I buy old cars and motorbikes in good faith about the condition they are in and always end up paying twice what I imagined to fix them up, but thats life.

I am one of the blind and if a designer stands behind his design should something go wrong then thats good enough for me. With a 20' tri this simple, if it looks right it probably is right.

[Fanie]

I fail to see why only one designer should have a claim on all tri's. Everyone else is free to do his own thing. If it was a copy of someone else's work for reselling it may have been different. I fail to see what this tri has to do with any of Ian's tri's.

As far as I can see, many of the boat designers maintain a presense on various forums. They learn from us, and we learn more from them.

[Butch .H]

RHP the voice of reason. Good on you:)

[Fanie]

Chris, instead of the side pipes tucked inside the hull for trailing, why not make them foldable ? The BOA of your design makes it very easy to do.

If it is foldable, the ama's can stay connected to the side pipes. This will make the time to water a no brainer. Fold the ama's off the centre hull, insert the locating pins, raise the mast and you can launch.

My tri also has to be assembled, but the beams and ama's is a pain in the butt to assemble. Not difficult, but a pain. My one friend has a windrider. Same story, his beams also disasseble from the ama's and hull, and is a pain to assembe and disassemble.

On the drawing, if there is a piece of flat below the hull's 2 pipes it will keep the ama's beam from falling through. You can just hinge the amas off the hull and it rest in place on the flat. Insert the pins and they're set to go. The drawing is as seen from above.

The trampoline can stay in place and you can just cover with a sail for protection when out the water.

I plan to convert my manually assembled beams to semi automatic ones soon ;)

[jamez]

Money is not the issue: the issue is inexperienced people being taken in by nice renderings and winding up buying plans from an exceedingly inexperienced designer: the blind being led by the blind.

So Doug, how do you become an experienced designer?

This subject has been
covered in great detail on the boatdesign forums. There is evidence both here and under "Sailboats", and on Dinghy anarchy and Multihull anarchy that you are ,in fact, using the forums to PROMOTE your designs-and I feel that is wrong-maybe dangerously wrong in the case of a KIDS boat!

It is the responsibility of the parents to ensure their kids sail in safe boats. What do you think is unsafe about the Cabrillo Skiff?

Nothing is stopping you from building and testing your own designs-but using others as your guinea pigs doesn't cut it. Ian Farriers experience with you IS relevant for that reason alone.

Has Farrier built the first example of every boat he has designed? No. It wasn't necessary. On your logic it could be argued that the first F41 builder was taking a chance on an untried design because I.F. hadn't built and tested the first example.

We need new designers who are prepared to break new ground and refine old ideas. That is how boat design has moved forward over the years. All successful designers have become so on the back of someone elses money. End of story. I laughed my ass off when I saw that IF had complained about Chris calling his 24'non-folding trailer cat the FC24 (for Fat Cat 24). Thats pretty damn precious in my book.

Chris, I appreciate your work and I hate to say this, but these attacks on you are, I think, largely the result of your own previous pedantry. What goes round comes round etc.

I just wish you guys could keep to discussing the theory of multihull design, which all the rest of us learn from, and keep the personal attacks off list. The ****-fights just plain unbecoming and quite frankly boring.

[RHP]

On the other hand, that was the exact reason why I decided to show support for Chris.

We had a tango the other month but I believe he is within his rights to post aa design for comments. One must move on in life otherwise it becomes awfully tedius living in the past.

I cant draw for toffee but I´d be a proud man the day I designed a yacht and posted it on here and invited comments.

[Fanie]

Maybe we can ask Jeff to clean this thread up a bit and continue on the tri ?

[Chris Ostlind]

Chris, I appreciate your work and I hate to say this, but these attacks on you are, I think, largely the result of your own previous pedantry. What goes round comes round etc.

I just wish you guys could keep to discussing the theory of multihull design, which all the rest of us learn from, and keep the personal attacks off list. The ****-fights just plain unbecoming and quite frankly boring.


Jamez, RHP...

I agree with you completely in your comments above. That is exactly why I have taken the steps to "clean-up" my commentary to Doug on this Forum. There is more powerful energy going on within this list than my indulgence in an unnecessary dust-up as one might have in the bar after sailing. I deeply appreciate the kindness I have been shown here in spite of some of the "issues" I have brought to the table in the past.

My most sincere thanks to all who have contributed to this Beach Tri Thread. Your comments have sparked a new set of ideas for me and hopefully, that process will lead to an improvement in the work I am looking to do.

[Fanie]

I withdraw my previous suggestion on the folding of the ama's. This is better and will work easier.

The two sidebeams are hinged in the hull centre. Sorry about the sleek shapes there :D but it's just to indicate the principle.

The tri can be launched with the arms up (ama's tucked in). Once in the water, the top of the beams are pushed down and the ama's spread themselves out. The beams can be located by a veriety of ways to stay in one place. This can be done before launching too if the trailer allows it.

The way this works currently both ama's are getting in place at the same time, and it should take about 15 seconds to get them down or up.

Each beam half gets two arms that forms a V with from the joint with the beam to the hull to keep the ama's from getting pushed foreward or aftward during folding, so each beam has two guide arms, one foreward and one aftward to form the V. The left and right beams being connected by a hinge makes the folding balanced and both sides works together as one.

[Fanie]

My tri's BOA is 4m, this allows me to fold it in to about 1m800 (easy fit any trailer) and height is just over 2m on the trailer. The trampoline stays in place. The front and rear arms when up could also be made to hold the mast, maybe in a sling.

[Fanie]

My one friend that was here earlier suggested that by partly raising the beams when it rains (it's raining here :D) you can pull a sail over to make a tent to sit under. I thought it was a cool idea.

Just note that the hull can rotate some when the beams are partly up. This could be contained by using a short rope to pull on both sides when the beams are lowered or raised.

[Fanie]

How about this ?

[RHP]

How about this ?


......and you get a fat lass to sit across the join?

How does that work Fanie?

[Fanie]

Hi RHP,

A couple of skinnier than fat lassies is certainly a tempting option :D

In my case the beams folds into the center hull so they are about flush with the deck. If one drill two holes per side horizontally through the beam and the beam gutter (under the deck) you can stick pins in there to hold them in place, or from the top you can bolt them into place, or you can use a rope tied to the beams to pull them into the hull and tie down there, or you can have studs protruding down from the beams where you can turn nuts or whingnuts on from below, or you can make a clip that folds over the beam that holds them down... and I'm sure I missed a couple.

I have bolts to bolt the beams down currently, but I find them a pain because of the time it takes to turn them in. I get no kick out of the assembly process, I want the setup to be done in a minute or two and go off.

I think the pins will be quicker and easier. Cannot take much longer than 10 seconds to stick a pin in there, so 40 seconds. You get some of which the one end has a 90 deg in it and the other end has an off-center swivel pin. The swivel pin hangs down and both it's ends hooks when you try to pull it out. You have to allign the pin and the swivel pin to pull it out.

[rwatson]

How about this ?

Fanie;237392]How about this ?[/QUOTE]

Fanie - this is the Farrier designed folding arms - which is now out of patent as wonderfully described in a previous link.

Except in yours, the cross beams magically grow longer to form the apex.

have you not had a look at the Farrier design before ?

[Fanie]

My beams are connected in the centre, the farriers gets lowered either side independent. The Farriers also have a double arm system. Nothing wrong with them though, I think they work ok.

Except in yours, the cross beams magically grow longer to form the apex.
Well, I'm going to build that magically grow longer in a couple of days :D

Print, then use your old school ruler to check the lengths are the same.
I've cadded it up, the fiberglass and the other stuff arrived yesterday. I have some things to finish for a few customers then I'm onto it.

A-hand, I've made a little model of the arms. Magic in it too :D

[rwatson]

Oh yes - now I see it. I didnt look closely enough.

The downsides that spring to mind (because I am a contrary bastard), is that you will have to take the boom off if the arms "happen" under it, and the cabin will need a groove through the middle. ( if you have a cabin happening ). But other than that, it should do the trick.

Look forward to seeing the piccies :-)

[grob]

I love these folding mechanisms, one thing you may not have considered is that your drawings show the frame folding in a symmetrical manner, i.e. the central joint in the beam is always moving vertically above the centerline of the boat, however there is nothing to stop that central joint from moving off the vertical centerline and the hulls from flopping about. Possibly why Farrier didn't join them in the middle.

edit .... I suppose in hindsight the weight and bouyancy of the hulls will keep them in the same plane (at the waterline) and will help to keep the mechanism quite symmetrical.

All the best

Gareth

[RHP]

Fanie;237392]How about this ?

Fanie - this is the Farrier designed folding arms - which is now out of patent as wonderfully described in a previous link.

Except in yours, the cross beams magically grow longer to form the apex.

have you not had a look at the Farrier design before ?[/QUOTE]


You mean Farrier used the fat lass method as well? :D

Get it patented fast Fanie and you´ll make millions!

[Fanie]

Chris can patent it then send me half ;) I'm just a hobby ? builder. The farrier's beams hinged differently, also they are not attached to one another.

There are also two arms on each beam, ok, one it attached to the hull before the beam and the other behind the beam. If you winch the tri up on a trailer you don't want the ama's to be left behind...

[Chris Ostlind]

I've been fiddling with this concept a bit. It's a modified version of what Farrier did and about halfway between the folding system developed by John Marples for his CC26 design and the demountable setup that is used by the SeaCart30.

For a solo sailor, I don't see this working easily for boats much bigger than the 21-24' LOA. It has been used successfully on the CC26 and the SeaCart30, but it is simpler to build than is the Farrier system and may be a whole lot less daunting for the home builder.

The beams slide into sockets in the vaka hull. The end fitting on the waterstay strut is pushed into a notch at the end of the sliding plate, locking the strut into location horizontally, where it is cinched down tight.

To fold the ama against the hull for transport, simply twist the cinch locks open on both beams drop the strut end out of the notch and pull the ama assembly away from the vaka hull. Rotate the ama down and into the vaka while lifting slightly. The beam ends will lift up and away from the boat tucking the ama down against the vaka hull for a very tidy package, well under trailer legal limits.

The process is illustrated below.

The nice thing about this technique is that it forms a really strong triangulated structure that places the beam in compression. All the parts of the main structure are aluminum with off-the-shelf urethane bushings from the car industry.

As usual, comments and such are welcomed.

Simple, durable and minimal moving parts that can be quickly fabbed by the home builder with alu welding skills, or cost effectively built by a good welding shop.

[Fanie]

The reason for tying the two beam ends together is exactly so that a single person can fold or unfold both ama's at the same time. I haven't worked anything out for larger tri's yet. I first want to play with the small version first.

As for your daysailor Chris, I think this will be the easiest and fastest to do.

[jamez]

A single-strut system is also used on the latest Grainger 7 metre racing tri

http://www.graingerdesigns.com.au/stock-plan-detail-145beam.php

[Fanie]

I ordered some SS brackets for lasercutting, and bought two SS hinges this morning. It's going to be a few days yet before I can do anything constructive, but I will let you know where the issues are with folding this method if there are any. Think I'll play with it in the pool :D

[catsketcher]

I like the idea Chris but I don't get the sockets as drawn. Would it not be simpler and lighter to have the waterstay strut attached to a single point and have the inner end of the beam bolted down to the gunwale. Maybe you could mould the deck to the beam end so that the bolt does not take that much load and gives redundancy - I love redundancy in beams.

What would happen if the strut slips in its slide out sailing? The beam then ends up being a cantilerer and under heaps more load. I would like to see a the waterstay strut ending on the beam with a yoke and a bolt that goes all the way through the beam (nice bush on it) that can't slip or slide.

I can't see much wrong with the Marples idea for a small tri that is going to be rigged on the beach anyway. I would like to see composite techniques used to hold the thing together - inner ends only just inside a small glass and highly tapered socket so that you can sail the thing without any bolts at all. The good thing about a tri is that the beams are always being pulled upwards. You do need the strut to be a strut for any compression loads of people on the beams on the beach etc.

cheers

Phil Thompson

[catsketcher]

I forgot to mention another thing. With the strut angle as it is there will be a substantial vector turning the strut into a compression member at its inner end. I haven't done the maths on your tri but I would suggest lowering the struts closer to the waterline. On a tri the main hull only ever lifts - a cat is of course different, but the this means you can put things (flare, struts) lower down on a tri than on a cat.

By increasing the strut angle to about 20 degrees the compression load on the beam will be about 3 times the load on the sidestay - 15 degrees about 4 times and it gets worse and worse as you narrow the angle.

This is another reason I don't really like the long sleeves. They don't really serve a useful function on a typical short compression loaded column. Pin jointing should be fine on this design. Close fitting sleeves scare me when rigging (sand, oxidation etc) and loose fitting ones are almost pin jointed anyway. So I think make it lighter, cheaper and faster to rig by having pin jointed ends in a nice composite moulded end fitting on the deck.

I like the boat and your ideas - my feedback is in the best of intentions

Cheers

Phil

[Chris Ostlind]

Thanks for the input, Phil. I really appreciate your experience in these matters.

The Vaka tube receiver serves to provide a passive "connection" to the vaka. I looked a long time at the socket and insert that are being used by the SeaCart30, along with their simple, waterstay wire from ama to vaka. I also was struck by the simple folding system being shown by John Marples.

The socket of the beam and the simple, single strut for folding and loading, were my solution to the issues present while trying to maintain as simple a mechansim as possible with most security and the easiest rigging.

A four sided conical structure, such as being used by SeaCart would have been enormously more solid of a connection with none of the binding potential that is potentially evident with the tube within a tube setup. This conical structure is incredibly easy to seat without binding issues, but it is much, much harder to build for the guy who wants to do this boat in his garage and does not have the ability, or the inclination to build a really cool mold for the job.

The passive aspect of not having any bolted end terminous for the beam is important to my concept of reducing the tasks involved for the end user. It may well serve me better to include a welded, end fitting on the beams so that they can be simply bolted down to the vaka deck, but I'll have to look at that possibility a bit more.

Marple's single strut system is elegant and totally simple to build, as long as the boat's ama is of the weight that can be be handled by a single person... hence the nod to relative LOA limits.

Your comments about eliminating the hand tightening setup against possible loosening while at sea were excellent and will be incorporated in future iterations.

I'm more than sure that things can be further simplified without going to an agricultural aesthetic solution, so.. I'll be looking at the entire setup further.

Please, keep those cards and letters coming folks, as I'll be dipping into the drum on a regular basis for more ideas for this fantastic, simplified folding system for small trimarans.... ;-)

[rwatson]

A single-strut system is also used on the latest Grainger 7 metre racing tri

http://www.graingerdesigns.com.au/stock-plan-detail-145beam.php

Yeah but you cant fold them in the water ....

"ST7 High Performance Trimaran - Trailerability
This is not a boat that can be folded on the water.

There are two reasons.

The first is that you don’t have the upper folding strut to control the attitude of floats as described above.

The second is that because of the overall beam and float buoyancy, the floats would submerge too deeply in the water while folding, thus requiring a lot of force to physically lift the mainhull as the floats are being folded.

By avoiding the constraints that would be applied if we had made the boat able to be folded on the water, we have had complete freedom with determining outrigger buoyancy, overall sailing beam, and the beam clearance from the water."


http://www.graingerdesigns.com.au/stock-plan-detail-145tra.php

Will that be a problem with yours Chris ??

And fanie, will the bouyancy of the Amas create problems in your method ?

[Chris Ostlind]

Will that be a problem with yours Chris ??


I don't anticipate that kind of problem, RW.

The Cardiff is base line specified with a rig from a Hobie 18 and has an outside limit of a rig from a Hobie 20 at 250 sq. ft. of sail area.

The Grainger boat is quite a bit heavier and carries quite a bit more sail area (mast height estimated at 35 ft. compared to the H20 mast at 31') The result is that the Grainger machine will probably have a much larger demand for fuller and taller amas, putting a larger premium on water clearance when folding. The boats look to have fairly similar freeboard, as the C21 is done with a generous water clearance for its size, though I do expect that Grainger is a bit higher than the C21, simply due to its overall bigger volume.

I'm really guessing at the Grainger specs, as they do not seem to provide the numbers for the boat at that link shown. Is there another location for a better idea as to just what specs the G-boat might have?

It's all about the geometry of the beam to height to strut length when one looks to water clearance for the folding amas. Just running through the simplified numbers with the prototype drawing, it looks like there will be a nice degree of surface clearance when folding. This will allow the boat to be launched with the amas folded. This, in turn, should make for a comfortable launch procedure that does not get all the other boaters at the ramp up in arms due to the expanded beam needs.

At least, that's what I'm hoping for.... ;-)

[rwatson]

Sounds reasonable. The other side of the coin is being able to fold them in choppy conditions prior to motoring into the marina or narrow launching ramp.

When I think about it, a 21 ft tri is not really an "off the beach" animal at all. The 16ft cats are a handfull as it is, and I know from experience that assembling a 20 ft tri on the beach, from the trailer is a major pain in the ... back.

[catsketcher]

Gday all

I am interested in the idea of moulding a composite part instead of using alloy sockets. I don't like using alloy and bolting it onto a composite boat - that is one reason I would go the composite socket. Composites do so well being added onto a composite hull and an amateur can do this instead of getting someone to machine them a part.

I am thinking of a very simple cone moulded off a cylindrical fuel funnel. It then gets fillered then glassed onto the hull. Super simple, light and no leaks. To get the beam end to fit put a rough fit wooden plug in the end - smaller than the cone and put lots of filler onto it. Then insert into the honey waxed glassed down fitting you made from the funnel. It will come out exactly matching the first part. I do this on my little cats to make matching hinges and such on the folding mechanism.

Stay away from alloy bolted to the boat if you can! Composite to composite is sooooo nice.

cheers

Phil

[jamez]

The Grainger ST7 design is certainly NOT designed to fold on the water. I merely offered it as another example of the CC26 type folding arrangement. It is a re-design of a 20 year old boat that was a real giant killer in its day. If they hadn't reduced the cabin to nothing this would have been a great alternative to the F22R IMO.

Chris, I have study prints for the ST7. Let me know what specs you want and I'll PM them to you if I have them.

[Fanie]

And fanie, will the bouyancy of the Amas create problems in your method ?
I doubt that they would since one can adjust the position of the side arms.

I don't lay any claim on this, anyone who wants to use it is free to do so. I just fiddled with beams and stuff here and it came out that way.

I have a couple of things to do before I can tackle the tri. Once it's working I can feedback on it some. It fits in the pool so I can test it there to make sure everything works as it is supposed to.

With the beams folded one would want the ama's to support the centre hull so it would stay upright like a small single hull. When you unfold, the ama's should move out in such a way that there shouldn't be problems either.

For a daysailer I think this would be nice. You launch the beach tri folded, and getting ready to go should be a matter of minutes. Before winching it on the trailer, fold up and go home. For light tri's like daysailors I foresee little problems.

[Fanie]

I would like to view my opinion on patents. I see a lot of people tends to think if you think of something and you patent it, you can lay some claim to fame on something. It was also mentioned that the farriers' patents went out or expired or something.

Now about 500-and-somethig hundred years or so ago when I was born I got pushed around in a pram because if I was let out of the thing I'd hit the road and just kept on going. I 'ran' away a couple of times before I could even walk, had the whole town on their toes :D It got worse as I got older too :D

Anyway, the pram thing had a folding menchanism in the awning and it could fold up to fit in the car's boot. So if they were using it in prams that long ago, what's the big deal suddenly to patent it for a boat ?

To suddenly lay claim on something that can fold is in my opinion rediculous. Quickly look at your arm. See, it's got a folding menhanism in there :D Patent it... but it's so old as man himself :rolleyes: We also get ama's around the waste as we progress in years ;)

Very very very very few things are really unique. So unless you can come up with a 'new' something (which is outside our reference boxes anyway) then you are laying claim to an existing thing.

I see loooots of patents on the net, some sh1thead claiming a patent... and when you look what it is, it's something we did 30 years ago aleady. Seems someone is making some money offen some dumb arse who wants to part with his money. It's like the teenager coming home and excitedly announce to his parients he disconered a new band called Led Zeppelin :D

[catsketcher]

Folding multis is something that has occupied my mind since 2000 when I came up with an idea for a folding cat. Since then it has taken thousands of hours and more money on two prototypes - and yes I am applying for a patent - the process is arduous and costly.

That is not what I am writing this for - it is a scale thing. When I was first making scale models of the little cat my model worked really well. On the 6m prototype a few early folds on wheels in the backyard had me learning that hulls that you hold in your hand don't cooperate like that in full scale.

Cats and tri hulls are thin and want to fall over. They also bind up poorly designed mechanisms and need to be "fed" into their receiving sockets. In Chris's case I have already stated my thoughts on the sockets. Getting two beams to fit into two tight fitting sockets while holding up a float is going to be tricky. I have been caught trying to short cut on the cat and have ended up wrestling with a little 6 metre cat - it was a tussle.

So again I would like to see the tri have quick fit sockets - if you go to a stainless place that sells hinges and stuff for truck tailgates there are even nifty little spring loaded pin systems that click when they line up with a hole. With the simple struts and sockets you lie the float on the beach - attach the struts to the main hull and then lift the float up. The beams then nestle into the sockets and the stainless pins click into place. Lift and click rather than "A bit your way - a bit my way - PUSH!" Otherwise you do what the Windrider does and go really loose and floppy but I don't think that will work so well on this boat.

Fanie - As stated in previous posts I think that there could be some issues with your boat wanting to fall over - especially with a mast up - as it folds. Again the model may not show this up. With a raised mast the main hull could fall to one side, the floats stop this but the mechnanism may bind up and you may have to get ashore to give it a tug. Also the mast raising procedure will have to deal with a big folded rear beam in the way of mast lifting. It may need a temporary brace instead of an installed one - or just use the Farrier system - it is very well proven - you can use alloy - the Tramp did.

cheers

Phil Thompson

[Chris Ostlind]

Fanie,

Here's my take on patents for boat stuff in general. All you guys out there in TV land can have your own take on these things and I encourage you to make your points known. It won't change my opinion on the matter after 25 years of fiddling around producing video programs for start-up companies who blew a large wad on their chase to "get a patent in place" and then fitfully protect the same thing.

Real simple, patents can cost really large amounts of money. The more complex the claims in the patent application, the more money it takes for some patent attorney to make use of his selective knowledge of the arcane language of the patent application.

If patents could be submitted in normal language, there would be many fewer reasons for hiring of an attorney at $300 an hour to write this stuff for you. After all, who knows the way the machine works better than you?

For most patents, the big cost is in the process of the "patent search" so that you can quote many examples of prior art in your submission. Again, this is all part of the game, should you need to pursue some violator of your precious patent in a court of law. Notice how it, once again, comes back to a court scenario so that you need to hire another attorney to stand in for you?

After all, the patent by itself, is nearly worthless, save for the so-called ego boost one might get from being a "patented inventor". It's just a crappy, official looking document on your wall that just might impress your buddies when they come to visit. Without the desire and resources, as in MONEY to pursue the violators, the whole patent process is absolutely worthless as a business enterprise.

My take is that for the average guy, who has developed some really cool thing for the boating industry, the best thing to do is to take all the money that they would otherwise toss at a patent and save it for something else. The intellectual properties attorney, the draftsman who does the nifty and similarly arcane drawings of the invention and the fees at the patent office; Save it for another, more important thing.... That would be to use that money to invent the next best thing for the boating industry, OR... better yet, spend it on the marketing of the first really cool thing they did, so that they can achieve something like market penetration and hopefully, market share.

There is one exception to this patent thing for boaty kinds of things. That being the absolutely inconceivable potential that your patented device can properly be licensed out to a big time boat company for MILLIONS of dollars. Really, MILLIONS... as in the kind of money one might get for inventing a new medicine that cures five kinds of cancer. You know, the kind of cash machine idea that would move the desktop computer industry into the next millenium... Otherwise, it's a huge waste of time and money and it will give you a false sense of confidence that you really have something worth fighting over.

It is just so damn easy to make a ten- percent improvement in an existing invention that, in the words of the Patent Office, moves the invention forward, that it's ridiculous. Want to know how simple in actuality this all is... just go to a big tradeshow for any industry, you pick it, and watch the hordes of guys from Asia running around with digital cameras, taking pictures of everything under the sun that looks even mildly interesting.

Now, what do you suppose those dudes are doing with such a fervent sense of purpose? The answer is, and I hate to dump it on you nice guys who think otherwise, but they are swiping your ideas. They are shooting photos of your stuff so that they can take all that home and reverse engineer it. They will make some very small and virtually irrelevant change in the device and come roaring back next season (or sooner in some cases) with their own brand of your hard-earned super cool, next best thing. Now, don’t get me wrong that it’s only those Asian guys who are doing this. Everyone is doing the same thing, or they will soon find themselves without a job. Well, they will unless their company has a very high degree of ethics and they have their own super smart inventor dudes who don’t need the leg-up.

Think you can stop that? Think that it matters to them if they "might" get sued by you? Think they worry about your limited financial resources that totally inhibit your ability to mount an on-going legal procedure? Hey, my friend, this is modern business which is the civilized equivalent of open warfare without the explosions. If your figurative army is too small, you can only try to make a hasty retreat and lick your ego, literally.

All this boils down to the fact that you should be spending your lovely time, your creative problem solving genius inspiration and going down to the shop and inventing that "next best thing". This will, once again, put you ahead of the market and force the other guys to play catch-up to your glowing capabilities.

Does all this make me sound bitter and hateful? Do you think that maybe I had one of these gotchya experiences myself and have the wounds to prove it? Well, I'm not and I didn’t.

I just worked around hundreds of creative industrial types, making video based marketing presentations for them and their really cool, patented new gizmos. Most of them, if their invention was, in fact, really cool, were unceremoniously shoved to the corner of the big sales floor by a bigger outfit who brazenly nabbed the idea and had the resources to go full-tilt with it…. Within two years!

The good guys had no fall-back position and no fresh ideas, as all their time and money had been spent on chasing that “Hey, I’ve got a patent” concept. Eventually, many of them accepted full-time jobs at the firm which nabbed the invention, where they learned to keep their mouths shut and take that lovely paycheck home.

There isn’t much that would suck more than that.

[Fanie]

Chris I agree with you fully. Besides everyone looking for ideas, you can go on the internet and get years and years of information on anything.

I'm not a boat builder, but I would rather attempt to give the customer a better deal to buy a great boat than having to rev his pocket to accomodate my legal costs amongst others.

If a courier has to charge me for a packet delivered here, there are two ways. The driver can bring it the shortest route and save time and fuel and make his ounce of bread, I'm happy and they are happy - or he can take the route via Cape town then here in which case the parcel is going to be very expensive. The extra traveling and expense has wasted time, fuel and produced extra cost that didn't contribute any to the value of the item I am getting.

What many people forget is that in many communities people discuss things. If someone is happy with something he got everyone else in that line would be interested too. If the price is right then there is a good chance of selling more.

Big companies won't put out the millions for a little swing arm that you designed. It is far easier for them to just sue you, right or wrong, and keep you in court until you are bankrupt. Old trick. Why do you think it is that fuel is our only source of energy... many has come up with much cheaper alternatives. They will even just let you disappear if you are in their way.

As for my tri, I can see the mast up could topple it over, especially if there are some wind. The idea won't be to launch with the mast up. I will see how well it works once I've got it assembled. Patience... :D

[Manie B]

Chris

you are 100% correct

Here's my take on patents for boat stuff in general

nailed it spot on :D :D :D

[idkfa]

Guys you're right, the only time to patent is when YOU will manufacture yourself! Otherwise you will not get millions from some Co. for any of the different reasons stated above.

catsketcher if you still would like to patent, use the UK patent office. It is the cheapest and geared towards the backyard inventor, ie. you can write the patent yourself, a copy of NOLO - Patent it yourself, can help but not necessary. They will search the patent databases, periodicals for prior art and advise if your application can stand as worded. Then if you get through all this, less than 6months if you pay app & search fee upon filing 30+70lbs, withdraw and re-file in the US, the biggest market and the one you should own.

That's my take on individual patents and I ain't no lawyer.


Have you seen this folding system? The Exploder 25, I'm working on my own 20ft folding tri! Think I'll use a Farrier like system, not too worried about capsizing.

[nhatlamntu]

This is my multihull Product.
http://www.youtube.com/watch?v=sGPyl-Ja2Jc

[rwatson]

This is my multihull Product.
http://www.youtube.com/watch?v=sGPyl-Ja2Jc


What are the expected benefits - and what is new about the concept?

[rustysunner]

Glad you guys are diving in deep into improving "trailerable" tris. IMHO it's the key to a boat being trailerable. I'm confident I could have cobbled something ugly together that would've killed someone
first time it opened.

Thanks

PS: You must know my younger son. He was the one who discovered Led Zep about one year ago

[Fanie]

Dear Mr Watson,

The folding arms like in my earlier posts are working. There are some pics in the link below.

http://www.boatdesign.net/forums/boat-design/boxy-fisher-catamaran-idea-20022-18.html

I haven't gone to any troubles to add another hinge or mechanism to keep the centre hull upright while it is partly folded since the tri is only a test boat for some things I have to try before I jump in making the cat. It is however easy to keep it upright if you stand inside the hull and push the arms up or down, I can do it on the lawn. The position of the hinge on the hull determines how high or low the ama's fold in. The folded width is about 1m400. The hull wasn't designed so the ama's would fold in snug as Farrier did, never the less an easily trailable setup.

If one cad a mechanism up and the ratio's work out it is very seldom that it won't work out in real life. I'm visiting a friend at a dam with the tri after Christmas and will do some more testing on the hinging there amongst other things, on the water and not the lawn.

On fixing the beams to the 'housing' I have four bolts. It is a bit of a pain, it takes too long to screw them down and you need a spanner or socket drive.

A far easier and faster way of securing the beams in place would be a cam with an arm on it. You can then just hook the cam and push the arm down and the beam is locked into place.

In the event of a capsize, the cam can be released, the beams folded and the tri can be righted, then folded out again and cam clamped again.

[bushsailor]

I am building a 7m racing tri similar to a multi 23. I started with a old tri cut it up and kept modifying it till it works. (This process was slow but has avoided some design faults and was a huge learning experience) The plug is now complete and I will be making a mold next week. (easier to make a mould than fair several hulls). I now need some advise on beams. I have decided to use a grainger system similar to the new grainger 7 boat. Any advise on material to use and ideas would be greatly appreciated. My original idea was to 3D model a beam, 5axis route a plug make a split mold then layup vacuum infuse 4 carbon beams.
Weight is critical to this boat. My target is 250kg so I have little margin to waste on heavy beams.
I am not a boat designer so I have no idea how to calculate the strength required. Boat details are as follows:
Max sailing weight 500kg
Beam 5.2m
Beam length 1650mm
Main hull max beam 900mm
Underwater stay 800mm (supports beam nearly in the middle)
The tri will be sailed on one float upwind
Distance between underwater stay hull mount and top of beam 350mm
I worked out that breaking strain of one assembly would need to be about 1000kg including safety margin. Would this be correct?
thanks

[tugboat]

Hi everyone- I have a question on trimaran waterstays- why the heck would anyone use them? as soon as they go through the water the boat slows considerably. Doesnt this extra drag created completely defeat the purpose of a trimaran in the first place?...are they only used in folding designs? they seem to me to be not very intelligent. maybe im missing something?
- i have no idea why they are used and i am designing and building a core cell racing/cruising tri. I refuse to use expensive cross arm systems and also refuse to use waterstays: why could i not just use aluminum tube akas curved slightly at the amas and mounted with sleeve and pins? what about eliptical (tubes), curved akas? or triangular,? even an i-beam or something should be better than waterstays?
it seems that would outperform any tri in the same class that uses waterstays??? hope someone can explain why waterstays are used...
thanks !!

Doug

[Chris Ostlind]

... waterstays- why the heck would anyone use them? as soon as they go through the water the boat slows considerably. Doesnt this extra drag created completely defeat the purpose of a trimaran in the first place?...are they only used in folding designs? they seem to me to be not very intelligent. maybe im missing something?



Waterstays are used in various ways, Doug. Typically, you can use a much lighter aka beam with a stay, than you can without one. This may allow an overall lighter structure and ultimately, an overall lighter boat. Many times, it can also be less expensive to build the aka structure with stays, than to build it as a stand alone beam. You can usually build with a smaller diameter beam with stays than without, reducing the aero drag signature.



... i have no idea why they are used and i am designing and building a core cell racing/cruising tri. I refuse to use expensive cross arm systems and also refuse to use waterstays: why could i not just use aluminum tube akas curved slightly at the amas and mounted with sleeve and pins? what about eliptical (tubes), curved akas? or triangular,? even an i-beam or something should be better than waterstays?



Let's see... a racing boat design that is not going to use "more expensive" beams (I assume carbon construction here) and also do not want to use waterstays. This means that you are probably limiting the discussion to larger diameter aluminum tubing, or wood/composite box beams designed for the loads of a racing boat. You can use alu tube akas with a curve if the tube wall and diameter are of sufficient strength to handle the job. Finding a good mandrel bending service for tubes of the proper spec may be a bit of a job and it will not be free to have it done. You'll probably need to have them shipped two directions if the bender is not within reasonable driving distance.

Outside of those two solutions, the design of the L7 sliding beam trimaran utilizes pultruded fiberglass I-beams to solve a very similar dilemma to the one you describe. You may want to take a look at how they have integrated that material in their boat.

Using flat beams will probably require you to have taller amas, as sea clearance is a bigger issue for drag than your complaint about waterstay drag problems. If your design regularly immerses the ama end of the beam you'll see drag numbers through the roof compared to wire stays.



... it seems that would outperform any tri in the same class that uses waterstays??? hope someone can explain why waterstays are used...
thanks !!




Well, yes, properly integrated and designed aka structures can contribute to a faster boat over one that uses waterstays. It all depends on where you are going to sail and in what kinds of typical conditions, as well as a very long list of design brief issues which need to be thought of as a whole if you are going to arrive at a truly fast boat.

In parting, you may want to look at the exceedingly fast SeaCart30 trimaran from Sweden. It uses waterstays as a functional design component to full advantage. Virtually the whole boat is carbon with really strong and slender, low drag carbon aka beams that fit into sockets in the vaka hull. This design solution is done so that the boat can be easily trailered without the added weight penalty of a typical folding system. If fast is what you seek, you may wish to consider how they have completed their design with waterstays. The SeaCart30 apparently suffers no serious problems when it comes to fulfilling the goal of an incredibly fast boat for racing.

[tugboat]

Thanks Chris! and every one for responding-- i will check out the above mentioned designs- yes i had thought of using large diamater tubes but you have brought issues to my attention regarding that..what i think i will try is using corecell...making large diameter aka halves, epoxing and glassing both sides(composite foam sandwhich)and then joining the halves with epoxy to create light but large and inexpensive akas. Maybe 8 inches in diameter?. lets see thats PI x dia x length say using 8 inch dia akas and 3/4 inch core cell- aprox 200 square ft of core cell...i can get that much core cell for about 500.00 at noahs marine...and the glass and epoxy should not be too much- thats maybe another 300.00 or so to do that amount..looks like i could make my akas for around 800.00 give or take ..that doesnt seem too bad for unstayed akas.? does it? i could make a 45 ft mast in the same way but only 5 inch diameter and eliptical in shape.

peace and thanks to all..any comments positive or constructive are appreciated.

[tspeer]

Hi everyone- I have a question on trimaran waterstays- why the heck would anyone use them? ...

Waterstays are generally out of the water (despite their name), so don't add appreciable drag.

I assume you realize that the water stays react both the drag loads on the leeward ama and the forward thrust from the shroud on the windward ama. If you don't have any water stays, the beams have to be stiff in the fore-aft direction to take these loads, and that adds weight to the beams. For example, the structural part of the beams on my Chris White-designed 34' trimaran are only 2" wide. The rest is just a light foam and glass fairing.

Another reason to use waterstays is to have a statically determinant structure. If you depend on the bending of the beams to take the drag and thrust loads, you have a statically indeterminant structure. You have to take into account the elasticity of the structure in order to analyze the strength and stiffness. Finite element methods are great at doing this, of course, but I'll bet most designers of homebuilt beach trimarans don't use FEA. With waterstays you can use pinned joints for the beams that allow you to analyze the structure as a truss - much simpler, and you know where the load paths are.

You can integrate the water stays into the design of the boat so they serve other functions as well. For example, running the stay taking the drag loads from the bow to the outer end of the forward beam makes it a great place to attach the forward net. Otherwise, you'd need to provide lifelines all the way from the bow to the forward beam on boat that was bigger than a beach cat.

[tugboat]

Ok..ill put myself on the line here: this is the concept of my amateur designed tri- i have the plans dawn and the core cell for it now. i have based it on the premise that the originators of multihulls(the polynesians) did not have autocad or any real modern naval architecture knowledge albiet what they learned over years, may have been of trial and error. of course those boats are probably not as fast as todays but they still have merit in there design concepts. i.e they used only their brains and guts to design their crafts.- now having said that I know i am opening a can of worms here and there will be people who will disapprove of my design and tell me that it wont stand up to heavy weather etc etc blah blah. but i guess i wont know for sure till i try..but try i must so here it is...
the vaka design is essentailly an ama shaped 32 ft loa hull with an area of 256 square feet. it is made form 3/8th core cell lamainted with two layers of cloth inside and out. using a wave cutting bow- rockered at the stern- shape smaller but very very close to the float of an extreme formula forty cat float. but it will be wide enough say about 3 ft at its widest beam amidships, to accomodate one person on a mattress berth to lay down on when i need to rest on extended ocean crossings. the boat will be water tight using an entry hatch on the deck being sealed up in heavy weather. a self draining central cockpit which is built similar to Chris Ostlinds cockpit- which i
sorta-kinda got the idea from a warren design. the mast will be made from core cell in halves having a dia of about 6 inches and about 45 ft high. rotating on a ordinary wheel bearing mounted at the hull keel. and through the deck. with a good sized mast diamater cyclinder mast step protuding up through the outboard deck about about 8 inches or so as added support. the rig will be a large wishbone rig similar to the nonsuch im thinking around 450 square ft.- hopefully jibless!. the sail is attached to the mast using a sleeve. and reefing is done by pulling the sleeve at the bottom and pulling it down. then pushing it back up with a long pole type tool(?) .... (btw how important is a jib anyway if i use a huge wishbone rig??) i would like there to be a mainsail only, if possible.
the akas are made again from core cell- 8 inches dia by 1/2- 3/4 inch thick each 28ft long. WITHOUT using waterstays. as i want no drag when i hit a wave to slow me.
the design is very sleek and made for speed but it will be strong with the foam and epoxy. and i plan on using it for extended passages with bear minimum gear. mostly coastal cruising but i could cross an ocean if needed.-The rest of the boats area will be used for food and water for long crossings. free board about 30 inches plus at the cockpit. i will use dagger boards or even leeboards to prevent dmagae should i hit soemthing- although i have been toying with assymetrical amas to do away with a dagger board. alternately i may or may not use daggerboards in the amas themselves, regardless of what others say about that type of system. amas will be half the size of the hull beam and attached using standard ratchet straps recessed into the amas about a 1/8th inch. so as not to move or cause drag. or perhaps a bolt mechanism. the cross arms are one piece long 28 ft running running THROUGH at the cross arms and step to aid in mast support and help in the rotation without binding. and a cross arm running through the hull at the cockpit aft. the mast will be freestanding rotating type. i have experimented using core cell for masts and let me tell you- they are strong !! in the event of a severe storm and high winds and seas- the boat will be watertight and ill hide below using a sea anchor till its done. or outrun it. The idea is, it is a capsule 32 ft long. with slenderness ratio of about 10:1. the main hull will weight around 250 lbs dry. but no carbon fiber will be used. people have crossed the atlantic in dories and even 10 footers! and Web Chiles crossed oceans in the south pacific in an open standard dory 18 ft long using canvas sails!
ok...i know its what might be called primitive design but to me that is a compliment - because the idea is minimalist and simplistic and cheap!- lol.if not ill just go buy a k design catamaran plans. anyone think the duo 800 would be a good choice for passagemaking if using the right precautions? the idea is to get on the water as fast as possible..btw the sails will be polytarp. im sure the traditional sailors out there will have some objections to the poly, but they also do work well! any positive or nicely communicated constructive ideas are welcome...
thanks-

i wish i knew how to upload my hand drawings for you to see.
Doug

[idkfa]

Your slenderness ratio 10:1 is not fast, more like 14:1 +

[tugboat]

IDKFA- yeah i understand what your saying- the more sleek the better- that means at its widest - 14ft you have a 1 ft beam, at 28 ft you have a 2 ft beam and at 42 ft you have a 3 ft beam, .yes very true- that would slice through the water have low wetted surface and if there is good rocker and a round bilge design with wave peircing bow,combined with a huge sail area and rotating wing mast- you would have a racing design ...very nice , but i need a berth inside the hull- so i have kept the beam to a minimum for a comprimise..i may lose two knots with a 10: 1 rather than 14: 1 but i can sleep in it more comfortably and that makes the experience thoroughly enjoyable. 10:1 is still fast at 32 ft. better than the standard 5:1 or so on the farriers and they'll do 20 knots.

[idkfa]

Actually, 10:1 would have significantly less wetted surface than 14:1 at same DSP. But ignore WS, not important, get the prismatic right and keep the surface smooth for high-end speed. One would have is significantly less wave-drag and that’s the limiting factor. (if didn't screw something up). Taper the freeboard to maintain your reserved buoyancy and allow for a bunk or shoulder room when sitting.

20ks+.... That's with spinnaker on a broad reach. Approx 2/3 of wind speed, so in 30+kns wind, or with a bit less wind and surfing on large quartering seas. Beam reach at high teens with risk of stuffing ama. On all other points of sail not even close. Average speed a few kns better than a monohull. I’m suggesting sailing at wind speed, and at much wider range of angles, with less effort adding, changing and adjusting sails. You’ll probably have two reefs in the main most of the time. Which probably is desirable most of the time single-handed blue water sailing and especially at night. No expert here, just a suggestion.