A New Beach Trimaran

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...

 

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.

 

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.

 

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

 

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

 

Why the sockets?

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

 

another thing

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

 

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.... ;-)

 

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 ?

 

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.... ;-)

 

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.

 

Moulding parts

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

 

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.

 

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.

 

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 It got worse as I got older too

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 Patent it... but it's so old as man himself 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