6.5 to 7.5 metre performance/cruise multihulls

wow that is glassy!

Barry

 

The skeleton of Sid 650 lay untouched in shed for 3 months or so - but I did build the foils and T rudder; however got some 3mm ply and started skinning the framework.

 

Good to see you building and posting again

Hi Gary, its good to see the small Sid growing again. I have missed your posts, I like the way how you are building boats.

Go on, Michel

 

What about a 6.5 meter Trimaran Transat class ?

Gary, interesting projects you are working on. Cool boat building life you have, so it seems...

Related to the headline of your thread "6.5 meter performance multihulls"... as you know, since long we have the 6.5 meter class which is racing annually from Canarean Islands to Carribeans. Its the "qualification race" for young and upcoming sailors who intend to become professionals...

The 6.5 meter one design class known as "Mini Transat 6.5" is highly performant...



LOA 6.5m 21.5 ft
Beam 3.0m 21 ft
Draft 1.6m 5.25 ft (keel down) 0.55m 1.8 ft (keel up)
Displacement 1065kg 2350 lbs (At Class Mini measurement, incl. Liferaft, batteries etc)
Sail Area Up 40.5 sqm 436 sqft
Sail Area Down 98 sqm 1054 sqft



There are two boat classes, the series built ones, and the "experimentals" (which have bigger sponsors and doing some crazy experiments) as we can see with the "top favorite" sailor Davy Beaudart who let built "Flexirub 865" with a "spoon bow" and canting keel.



What do you think about a 6.5 m (21.3 ft.) Trimaran Transat Class ? Might be something interesting, isnt ?

Maybe little bit longer, e.g. a 23 or 24 ft. Trimaran Transat Class for more safetyness, as we see that there are boats of that size sailing successfully, e.g. the Diam 24 (some call them the "mini MOD70") or the Multi23 (designed by French designers Van Peteghem and Lauriot Prevost / VPLP Yacht Design).



Little bit re-configuration to have a "one person cabin" under deck can make them capable to sail trans ocean.

So loooks a 6.5 Mini Transat under deck... the kick of the Minitransat: The sailors must navigate traditionally.... so they have paper charts on board (and sextant).

 

My sailing mate Jacques de Reuck did the 1979 6.5 Transat (came 4th or 5th) in a Charles design named Vileda, a skinny, lightweight dinghy built in alloy so I know about the 6.5 class, even wrote articles for local Auckland sailing magazines about the race.
Sid 6.5 foiler trimaran is a small boat in comparison to the mono 6.5s which have 3 metre beam, accommodation beam that is, whereas Sid, although having a very flared and wide deck, is just wide enough on the waterline for a bunk at both ends. Also compared to the mono 6.5s Sid 6.5 will weigh around 200kgs, very different type of fish.
My problem at the moment is designing a sensible pivoting beam and float/foils. The boat has changed from what originally was a very simple boat to something else entirely - although I'm determined to make it simple to trail and also to sail.
photographs:
John Patterson 6.5 - an inspirational design; Sid will be wider overall (7m) but similar main hull dimensions.
Jacques mini-Transat 6.5 Charles design

 

Tks, Garry. Very neat this 21 footer... would be great to have an own class for a MiniTri Transat !

With a powerful mast and modern sails it doesnt look "old fashion".



The real beauty and "modern design" can be seen looking at her from front... see attachment. And it seems enough space under deck for one person at least (Source of pic: Tom Henry @ FB)

Tom is here in this forum, too.

 

Mini transat--- Huh!!
That brings us back to the proven Tri----The Buccaneer 24.

 

Has the B24 been successfully used as "one design class" for single-handed Trans Ocean Races ?

I suppose nowadays the bow form of Lock Crowther's design is "out of fashion" and cant be seen as "state of the art" in modern yacht racing / Trimaran design



7-8 knots in light wind.... no sponsor would invest in such boats anymore.
https://www.youtube.com/watch?v=94-SYOFG3Ow


Little bit overpowered with loooooong bow sprit and modern sails... the B24 can be of fun...
https://www.youtube.com/watch?v=Z-lgC4WBk6Y#t=54

 

Few more Sid 650 shots. Jacques came round yesterday ... long discussion of how to swing the main beam, thinking about many alternatives, one being reduce the beam to 6.5 metres and have it being able to be lifted out, stored on trailer beside main hull - another where don't have any floats at all, just a swelling at the top of the foils, my suggestion, sounds very dangerous - eh Doug Halsey? Have I your courage?

 

Im still voting on slight extension under mast ball, just a square section under ball, then matching square in center of beams to sit on it, then on trailer pick up beam spin 90 and done. easy peasey, simple simon. hell even take square tube, fillet bottom and use walls bent over as the mounting straps to firewall. weld a large plate on bottom of ball that transfers load to a large ply washer to distribute load. when trailering just unscrew ball and rotate beams 90.

I know I know, back seat engineer! lol



Barry

 

Barry, thinking of very similar solution to yours at the moment ... but that for sure will change; (because I'm so fickle) will finish main hull first and then make the BIG decision.
One alternative is to have a lower cuddy, half the height of the main beam, square mid section of the beam sits into female box across the hull in front of cuddy, there is a tubular bearing (which also carries on top wing mast male bearing) - that allows you to lift the beam halfway up and out of the female box so the beam can pivot to fore and aft for trailering, sitting on top of the low sized cuddy. Simple enough??
That way I don't have to connect the cuddy to beam (so beam and cuddy pivot as one as formerly planned) - cuddy is fixed ... and no waterproofing problems compared to earlier idea.

 

One other alternative for svivelling. Take a tow ball, screw it to the ring frame, dead center. Epoxi a cup on the beam underside. That's your pivot just like on the mast. On the gunwales epoxi a piece of curved track (like you have for the mainsheet traveler on your other boats) with the cars epoxied on to the underside of the beam. Pin the cars in place when sailing. If you think the loads are to much for the cars, drill and tap the tow ball and install a threaded rod that goes trough the beam, with two big wingnuts (weld a handle to a normal nut) and tighten them when in use. The towball has enough meat to install a really big bolt that can take all the loads. Or go crazy complicated and use an excenter in place of the wingnuts. Or use one normal wingnut and make the second one out of a second towball that represents the pivot for the mast.
If you want complete positive control for on the water folding extend the track from under the beam to a complete circle, in this instance the beam is fully under control troughout the folding sequence and just maybe (depending on geometry) you can also use the aft part of this track for the mainsheet traveller. Maybe even a little more than a half circle would suffice and you can save weight.
I do not know how this would interfere with your planed cabin tough.

 

Thanks Rumars.The pivot point is not that importamt, imo, I mean a simple tube going through to beefed up ring frames will do the job. If the beam is a tight fit in the half female box across the hull, that will (even without the locking pins/bolts) hold the beam from fore and aft movement.
What I'm also saying is that once the beam is lifted from the long box, then swung round, will not be a problem, don't need tracks for it to run on.
Also I worry about the loads at the gunwhale areas (will have to be some heavy carbon laminations there too). I'm trying to get away from water stays going to the mast sidestay position - but will probably have to incorporate them ... for peace of mind. They triangulate the loads beck to main hull.
Keeping things simple ... is not simple?
Here are the various foils.

 

Ohh yeaH, half profile on top is all ya need, didn't even think of that. With that no need for any corresponding shapes in center, just lock it into channel and your good. And yeah, no need for tracks on such a lightweight hand toss-able item. Tiny springload might be handy though, just so it pops up when loose for easier swinging.




Barry

 

Hi

Has anyone checked out the polish catamaran, nawiatr 700k?

Seems like a decent candidate for this 6,5 to 7,5meter performance cruise category.

http://nawiatr.com/en/nawiatr700k.html