Double Ender
- Thread starter Roger Long
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ooh nice! I was just thinking if you mentally carve away at the transom a little bit there is a mini VOR60 waiting to get out!
Well in fact I like the look of a plumb bow, looks tough and manly, I think it would go well with your flat sheer.
Well in fact I like the look of a plumb bow, looks tough and manly, I think it would go well with your flat sheer.
Hmm my wife doesn't understand my humor either, it was kind of taken off the useful comment that lurking inside every double ender was a boat with a flat transom.
I started wondering if my off the cuff guesstimate that my double ender would have more sail carrying power than Eric Jr. was accurate. It was quick and easy to trace lines around the waterlines in CAD and run a moment of massproperties check to get the moments of inertia of the waterline planes.
The I of the waterline plane divided by the displacement in cubic feet gives you the distance between the vertical center of buoyancy and the M in GM, GM being a direct measure of sail carrying power per unit of displacement. The two boats have almost exactly the same displacement and it can be seen from the overlaid lines plans that the vertical centers of buoyancy will be very close. The differences in waterplane moments of inertia should therefore be proportional to the potential difference in sail carrying power if the same vertical centers of gravity can be achieved in construction.
The Iwp of my design is 11.6% greater so there should be correspondingly greater sail carrying power. Eric Jr. carries that big sloop rig well so my design ought to do quite well as the lower aspect ketch I envision but should also be able to stand up to a tall single stick.
My design does have more deck and ends which are additional weight above the center of gravity. However, she is intended for the lighter construction made possible by modern materials so she ought to come out as quite a comparable vessel in power to slug it out to windward but with less resistance and greater pitch damping.
The I of the waterline plane divided by the displacement in cubic feet gives you the distance between the vertical center of buoyancy and the M in GM, GM being a direct measure of sail carrying power per unit of displacement. The two boats have almost exactly the same displacement and it can be seen from the overlaid lines plans that the vertical centers of buoyancy will be very close. The differences in waterplane moments of inertia should therefore be proportional to the potential difference in sail carrying power if the same vertical centers of gravity can be achieved in construction.
The Iwp of my design is 11.6% greater so there should be correspondingly greater sail carrying power. Eric Jr. carries that big sloop rig well so my design ought to do quite well as the lower aspect ketch I envision but should also be able to stand up to a tall single stick.
My design does have more deck and ends which are additional weight above the center of gravity. However, she is intended for the lighter construction made possible by modern materials so she ought to come out as quite a comparable vessel in power to slug it out to windward but with less resistance and greater pitch damping.
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I am not a yacht designer, but am curious. I a boat like this you have hull speed which you basically can't go over. To get to hull speed you need a certain amount of drive from the sails. Excess drive past that is pointless. I suppose as wind increases you get more windage so some additional drive is required to overcome this. Given that isn't there more or less an optimum amount of sail for any condition?
Namely just enough to reach hull speed. Excess beyond this point isn't helping right?
So the correct sail carrying power is so long as you can carry the sail to get you to hull speed you are done? If you have more sail carrying power than that might not you wish to reduce the ballast?
It is a cool idea of yours, I often wonder about a carbon fiber Ingrid. Take an old timey design and render it in modern materials. My own boat is fin keel spade rudder setup and is a bit of a handful running with waves, although it beats nicely.
Namely just enough to reach hull speed. Excess beyond this point isn't helping right?
So the correct sail carrying power is so long as you can carry the sail to get you to hull speed you are done? If you have more sail carrying power than that might not you wish to reduce the ballast?
It is a cool idea of yours, I often wonder about a carbon fiber Ingrid. Take an old timey design and render it in modern materials. My own boat is fin keel spade rudder setup and is a bit of a handful running with waves, although it beats nicely.
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