around in pocket, I I think so

Westel: "any idea how much a steel Ten would weigh ?

Windraf;" of course, I know exactle the weigh of each part and the total"


Windraf,
you must be the stand-up comedian of the BDF

 

????
are you ok?

 

the weight of only hul steel ten is 0,4 ton with fram ( 16 square m, two different thicknesses)
more the deck, more the interior, more the rudder, more mast, sail and equipment
more ballast
total empty boat 0,85 ton

displacement with 75% load 1,5 ton (skipper, water, wine, alcohol, food ...)
full load, in is water line, 1,75 ton

draft
0,8 m empty
0,95 m 75% load
1 m full load

 

oh dear

she's going to be very heavy in steel
by the time you have added everything at 100% she is going to be well over 2200 kgs fully laden

I was aiming at 1000 kgs and ended up at 1300 kgs fully laden, and I know its going to be even more than that.

I am not so sure of steel any more, sounds good but is it practical?

 

Manie, my calculations are correct.
Here we have a different system of work: before draw and draw, then the boat is built in a month.
1.75 ton will be his total displacement at full load.
For the sail is still work in progress.
I have a guy interested in the project, but still did not find the sponsor.
Even for this here's a different way to proceed.

 

I'm OK, are you ?

 

http://windraf.blogspot.it/

 

Whatever the length, displacement, sail area of a boat, it would be important to me that the boat makes sense and sails well. I think this gets increasingly difficult if the displacement-length ratio is over 500. By sailing well I don't necessarily mean sail fast, or be able to tack through 90 degrees. I just don't think you should give up too much to be 10 feet long when 12 feet long might sail so much better, all else being equal. Interesting challenge though.

 

Jamie,

you' re right about the 12 versus 10 ft being "better" but.....if you enter a competition which states that the LOA must be 10 ft than there's little choice I guess.
If one decides to make the challange multiple times more awkward by setting almost impossible goals for yourself than it's obvious that the outcome will be something which isn't "perfect" at all.
Designing a 10 ft boat which is capable to "safely" cross an ocean is one thing, make the 10 ft boat "large"' enough to sail non-stop around the world is another thing......

 

Actually the D/L ratio of a boat has little to do with its windward performance.

It's the shape of the hull, the effectiveness of its lateral area, the amount of windage vs. sail area, and the efficiency of its sails, that rules the day.

lighter boats can actually have more trouble going to windward than heavy ones under certain conditions. Swedish life boats, designed by Colin Archer, had D/L's well north of 500, but were known to tow stricken boats tow windward, out of trouble. They had huge long keels with outside ballast.

The advantage of greater length is that it gets you more potential speed, as the speed potential of a displacement hull is a factor of its waterline length.

A boat with a 12ft waterline, for example, is potentially ten percent faster than one with a 10ft waterline. Over a long distance, this advantage really adds up.

Here is a proposed design of my own. It has a loaded displacement of 1700 lbs, giving it a D/L of 780. I doubt it would have much trouble sailing to windward.

 

Yes, a 10 ft boat for ocean voyages is an extreme challenge.
First of all it is an extreme design challenge.
I'm fascinated by this.
Obviously a boat of 14 ft would be a measure with possibility very different, and the design of a 14 ft would be less extreme and with different performances.
But 10 feet is a challenge in the challenge. Is it easier to draw a 100 ft, than 10 ft.
Ten feet oceanic has inevitably big beam, very heavy and destined to sail, for most of the time, with the wind from astern.
This influences the philosophy of the project.
Interestingly, the design of the Manie boat, sharpii2 and mine, are very similar in general layout.
To compare the sail areas of different boats there is a simplified and fast formula: divide the area of waterline for the sail area.

 

Thanks for the thoughtful replies. I am both fascinated and horrified. I thought the Colin Archer Rescue Ships were around 500 or less but the fact that they can tow to windward, in adverse conditions no doubt, is very impressive. What makes the Around In Ten so challenging is not just the 10 foot limit but the payload requirement for food. Even some of my worst baking makes for rather poor ballast. I like the idea of 'making hay' in more moderate winds and sea states. I will have to experiment with this I suppose. I have an old CL12 in rough shape in the backyard I could mess around with, see how it might sail even when loaded to the gills. Both of your designs seem very sound to me. Ultimately I would like to try something similar some day, with a storm rig and working sails for rough conditions and when sleeping, and more sail and perhaps a trapeze or hiking seat for making hay on fair weather days. I don't think the underwater plan would have to change much on fair weather days as I would have more speed to generate lift, but I suppose raising a centerboard or leeboard so I don't trip or roll over it might make sense. I accept the idea of designing for downwind or across wind most of the time rather than designing for windward sailing as you might on a river, while still retaining as much ability as you can to enter harbours and beat off a leeward shore and so forth. I assume the rudder and rigging can exceed 10 feet as long as they do not effectively increase the waterline length or even the pitching. I think I would like to try something like the Vertue 25 of Laurent Giles, only beamier and perhaps deeper. It is 11000 pounds, but lets say 12000 when loaded for a crossing.

So...
LOA 25 feet >>> 10 feet takes us down to 4800 pounds
BEAM 7.2 feet >>> 6 feet takes us to 4000 pounds
DEPTH 4.5 feet >>> 2.25 feet takes us to 2000 pounds

I think that might be a good start. I like the aft hung rudder on a full keel.
I would love to go deeper rather than beamier, but sea biscuits aren't great ballast.
I also like the cutter rig, but I think it could be a gunter like the mirror dingy.

I wonder how it might go to weather in a gale with just a storm jib and self steering vane, and the gaff and boom stowed on deck of course.

https://www.youtube.com/watch?v=EMKtOlK6WjM

 

Jamie Kennedy, this is my designe

 

Thought about this some more. If we assume a prismatic coefficient of 0.5 for slow speeds and a displaced volume of 35 cubic feet for 2240 pounds the area midship would be 7 square feet, so it might have a decent metacentric height even with only a 5 foot beam rather than 6. Looking at it another way, using the formula for metacentric height of I/V , so for L=10 and V=35 roughly...

m = B^3 /100
so for a beam of 5 feet, m= 1.25 feet, and for a beam of 6 feet, m=2.16 feet

If I recall, m is measured from the centre of buoyancy not the waterline, and for our little boat and its cargo we would do well to keep the centre of gravity lower than that but might not expect to get it much lower than that. I still thing some lead ballast is needed for self righting, as both of you seem to have done. I think a 5 foot beam might work if you could afford a higher ballast ratio, but as we don't have that luxury a 6 foot beam may have to do. I also thought about fatter ends like a scow, but still not necessarily a high prismatic coefficient. Then you might get by with a 5 foot beam, and the heel shape with an arc bottom and plumb sides might provide effective lift. Ugly, but I think you could clean it up a bit, and it would be like a Dutch sailing barge, or a swamped Optimist Pram. Other thought might be to add a small but very deep lead bulb on a minimal lateral area steel strut. Say 200 pounds 5 feet down. This would lower the centre of gravity by about 5 or 6 inches, and might still not trip the boat too much. Might even stuff a couple of crystal lead battery in there, and if it lights on fire it might not disturb your sleep too much. ;-)

 

Windraf. I saw that on your page from the other thread. It is in steel also is it not? I like it. Very much like a classic pilot cutter or Virtue 25. I wonder however just how strong and stiff these hulls need to be, and whether the storage bulkheads and distribution of cargo might be enough to spread the loads about. I like the idea of foam for insulation, but also wonder if laminated wood and glass epoxy might work better than using foam. With steel you would use some foam on the inside? I do like the idea of steel for a tough exterior, and foam for insulation only, and padding. I also like the idea of reducing hull weight however, as much as possible, and adding some lead. Of course the lead means you need to add strength you have just taken away. Tough challenge.