Open source 12-15m high performance/semi-cruising catamaran design

Ill let the cat out of the bag when im ready it forms part of a flat panel building system which is potentially profitable due to the immense time savings possible. It does require some investment tho and then it would have to be tested and proven so that all designers could spec it for boats they design. I become the supplier

 

OK, good luck with the business side then. Judging from the negative comments made by guys coving and taping bulkeads you could have a winner.
Back to design. What are your feelings on retractable foils? still going for them?

 

ive been thinking about a single dagger in a small center nacelle as discussed in another thread here on BDforums. The reason is because it frees up alot of room in the hulls and saves some cost/hassle etc and much better maintenance / damage survivability etc - many good reasons for it. But on the other hand its probably simply too "different" to be successful in the market place. Afterall, theres no point building a 50ft cat which will cost a small fortune and not be able to find a buyer for it once your done with it...
I like the idea of fully serviceable whilst on a beach, no jamming or fouling in cases and not having to worry about ripping a hole in the hull if hitting something at +25kts. Same problem applies to the lifting foils... This boat will frequently be sailing fast so if it does hit something its probably gonna hit HARD... im open to other ideas which achieve the same end but they all have compromises... I guess the C boards are the most proven system on sailboats to date? They could be angled straight boards instead? almost surface peircing in nature as the board exit in the hull could be around the static waterline. At least no marine growth in there but it completely ruins any accomodation space in that area which is up forward so not such an important area as the midship...

 

I read that thread on a center dagger and it really appeals to me too.

The system the proas use of a dagger that also acts as a rudder is also appealing, saves money and weight and its also outofthe hulls... dont see why the hull couldnt be slightly scalloped or flared out in front to reduce turbulence

 

That is how we do it with Intelligent Infusion.
Jorge,
Good thinking on copying proa rudders/daggerboards. Apply the same logic to the rest of the boat and see where you end up. '-)

 

semi-lift foil on the centerboard mounted in nacelle. 80cm clearance from foil bottom edge in stowed position to sea surface.
The lifting foil is held down by spectra rope that passes through the centerboard and turns around on a PTFE sheave at the bottom of the centerboard.

Edit: If the actuated foil is too complicated, fix it in place and set next to it a regular but slightly shorter centerboard. If speeds are too slow for foil assist use the straight board. If speeds are high enough, retract the regular board and use the foil board.

 

The aft bunk has very low headroom, even to get into it from the high side. I suppose that is what race boats have.
I put a bench in the space when you first enter, is that correct? It looked like galley went where dagger is because the cutouts are counter height.

 

Hi Jorge - ya gotta think in 3D man!
See this next pic;



The companionway step has been shown here and also a change to the cockpit seat which makes it alot wider to give more volume below to the bunk area. You can also see a raised section forward of the seat which provides headroom for the companionway to the rear bunk. Each companion way is offset laterally and also vertically so its ends up a bit like a spiral staircase if you will. The saloon floor inside also needs another small cutout step down like we put in the deck. The companionway from outside could be moved slightly further inboard, then omit a small section of cabinetry as you get inside to provide the space to walk. After that omission, the cabinets or seating can be full size.

The rear bunk can be lowered slightly to give more headroom - by how much determines the acceptable width of it. At present, its a queen. If you drop it down to give more headroom youll end up with a double. Also another 4inches of headroom down there can be had by raising the bridgedeck clearance from the 900mm or so at the moment upto 1m which could be good for other reasons also...

 

Okay, I was trying to follow your drawing as close as possible, I will give it another go tomorrow. Just working on small spaces gives me anxiety lol!!! Even though you don't have much of a bridgedeck I was surprised you had it under a meter, I think that should go up too.

 

Not nessesarily - 0.9meter clearance should be ok. Grainger on has 0.85m clearance on his 45ft flying fish design for example, same for many other designers...
Raising it creates another series of implications that go along with it

On another note - this boat as designed should have an OMR rating of 1.000 or better. The Sig45 has an OMR of .95 @ 7.3 tonnes.... this boat will come in under 5 tonnes in racing trim!

 

Interesting to compare the Sig 45 to the Schionning G 1400 wahoo
The Sig 45 looks to be much drier as the bows are much higher, not reversed. Of course, sail plan etc may be variables.

 

The sig should be a faster boat - im surprised its weighed in at 7.3 tonnes for its OMR measurement over in the US- the owner must have loaded it up with luxuries and what not as its supposed to be a 5.5tonne design according to lebreton...
Any real world figures on "Wahoo"?

 

4 tons including mast - lightship weight? So, to answer your question -- no real world figures
South African boatbuilder sells world’s lightest catamaran - IBI News http://www.ibinews.com/news/south-african-boatbuilder-sells-worlds-lightest-catamaran-4444

BTW Wahoo lost both rudders just off Guadeloupe
Latitude 38 - 'Lectronic Latitude http://www.latitude38.com/lectronic/lectronicday.lasso?date=2015-06-22

 

Its not overly difficult to build a light boat when your not designing or pro building for other people - a pro builder needs to have his *** covered so they generally build to a heavier spec. Same goes for designers. I guess schionning didnt mind pushing the usual boundaries a bit with "wahoo", it is also pretty low volume if you have a good look at it - 16:1 hulls...

This is my late fathers old boat, a 43ft CSK cat built in the 70`s;


It was only 4 tonne built way back then from ply and spruce... we often saw over 20kts on this boat with old dacron pin top sails, no battened sails, no rotating mast etc... a typical cruising speed on voyages was 15kts. You can see the hulls are very low volume however, not much comfort in this thing, almost zero fitout inside. But this boat sailed all over the world, crossed the pacific, who knows where it went after we sold it 20 years ago... imagine what could be achieved with carbon fiber and a modern rig?

 

Me like it.
Single board. Single outboard - rarely used, Empty bows. Kickup rudders. And decent stems.!! Did it have running backstays?
Believe that the bed in wall design would suit this 43foot.
Like the DeHaviland Mosquito plane - only what was needed where needed.