Dick, Thank you very much for your reply. I was inexperienced at posting on this site and inadvertently included your original posting. What I actually was interested in was the center of buoyancy of trimaran floats, not catamaran. Do you have any advice regarding the former? The original floats I designed for my 1.7 meter (or thereabouts) tri were too narrow and the center of buoyancy was certainly too far aft, since it nosedived in anything more than a light breeze. I cured this by moving the floats forward (so that they projected about 6 inches beyond the bow of the main hull) and by putting a foil on the rudder. However, now that I am extending the tri to 2 meters in order to conform with the 2 meter class, I cannot have the floats foreward of the main hull. So I clearly need to move the center of buoyancy on the floats forward. I was thinking that the center of buoyancy should be around 30-40% aft of the bow, but this is just a guess. The floats will still have a very low beam to length ratio (around 1:25). They probably will still lack a bit of buoyancy, which seems to me another reason why the CoB should be forward.
Many thanks for your reply. I visited your homepage and looked at the pictures of your models (superb). It seems that your CoB is around 40% -45%. I am not sure what you mean by your data sheet – I could not find this on your site.
Best,
Colin
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by Idealist
Dear Colin! -
If you look at my published data sheet, you will find the answer to your question!
But 1/3 of the bow it too much forward - definitely! -
The opening angle of the bow would be too blunt.
I hope, this helps!
Best wishes, Ernst Zemann
Professional shipwright - boatbuilder/-designer with 27 years of experience and a special interest in multihulls
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<font color=“red”>(It’s not from me!)</font id=“red”>
“The ideal CB location for any hull fits within a very narrow range close to 53.5% of the waterline aft of the bow.”
“For RC trimarans it is critical that the Center of Buoyancy of the outside hull must be forward of the Center of Gravity of the whole boat so that, as the boat heels and flys the main hull, the weight of the boat is acting to prevent pitch pole.”
<blockquote id=“quote”><font size=“1” face=“Verdana, Arial, Helvetica” id=“quote”>quote:<hr height=“1” noshade id=“quote”>Originally posted by Colin M
…They probably will still lack a bit of buoyancy, which seems to me another reason why the CoB should be forward.
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Colin - here is the latest thinking out of the U.K. in a currently being built 2 Meter. You will notice how much, and how far forward the float bouyancy is, and how wide and far back the main hull bouyancy is located. BUT - the main hull has sort of a “T” shape and gains bouyancy when it is pressed under, whereas the float bouyancy is pretty much the same regardless of relative position with the waterline.
Dick, Many thanks for posting these shots. The floats are very interesting - almost as slim as mine. I think I detect the influence of Nigel Irens’ designs in the floats. His floats don’t seem to taper much towards the stern at “deck” level, but are a very rounded V towards the stern. Since I will be sailing on Lake Champlain, which can have quite a swell, I may put more freeboard into the bows. The ones you illustrate look too low for me. Best, Colin