Originally Posted by Tom.151
Brilliant boat! Truly an inspiration of simplification.
Would love to see more pics of the boat - especially out of the water hull shapes, and the rudder arrangements, and more of the centerboard ..
?? Are the 90 degs and the 80 degs accidentally reversed here ??
Anyway, thanks for posting so we could see a bit of a tease of the centerboard details.
I will try to post more details when I get to my other computer. The whole system is very simple centerboard is made from wood with fiberglass glued over. It is mounted between two stainless steel plates with reinforcment ribs. Whole assembly is bolted to mast beam. Hinge on which board pivots also holds side stays keeping board vertical against side loads and also helps resist bending loads coming from mast.
Hull shape is conventional with V shaped front section, semicircular middle and aft. Rudders are kick up attached to transom like on most beachcats.
By 80 and 90 degree angles I meant angle between tacks shown on GPS track basically if you are tacking while sailing upwind good boat should make 90 degree angle when beating upwind. 45 degree on starboard tack and 45 degree on port tack.
Would you mind sharing details/sketches of your centerboard? |
Is the catamaran design yours or someone else's? (Wood's Skua?) I'm curious what the hull is made of? The other catamaran that you have a video of (https://vimeo.com/104815976) appears to have a very thick hull, maybe of foam? Finally, on the outboard ends of the pole that connects the two tillers there appears to be two horizontal rods, one at each end. (From 0:30 to 0:45) I'm scratching my head trying to figure out what they are for?
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I will try to post some sketch. Design is custom made by me with help from another Latvian multihull builder. Hulls are foam sandwich construction.
The green cat in another video is my first boat built 11 years ago. Hulls are carved from insulation foam then cowered with fiberglass that's why they are so thick.
The horizontal rods attached to pipe connecting tillers are extensions to make steering easier when sitting on the side seats.
Thanks for your posting. |
I do have a question however. In the video it appears as though there is a forward and aft 'stay' to the blade that attaches below the waterline. Is that so, and if so how does it kick-up??
The red line is to pull the board down and hold it in position. It is stretchy enough so it usually don't break if the board hits bottom. The white line going aft is for raising the board and also prevents the board from pivoting forward.
Of course a surface piercing board will work----but it will be very inefficient . |
See the turbulent wake it makes in the video, at the 40 second mark,
Also, as has already been mentioned, the bending stresses on the board and the extra weight of the structure to hold it, must be addressed. The lesson of "Occams razor and the Gordian knot" comes to mind.
It is good enough for cruising and only easy way how to make board that kicks up on impact. I sail a lot in Estonian islands where water over large areas is only 2 - 4 meters deep with large boulders hiding just below the surface. If you go off the marked channels sooner or later you will hit something. I gladly trade half a knot or so of speed for a board that don't break in half or rupture a hull in serious impact.
The support structure to hold the board weighs around 8 - 10 kg. I doubt the slots and all the reinforcments to mount daggerboards into hulls would be much lighter.