Displacemnet length ratio

[dskira]

It is not unusual in fishing vessel to have a displacement lenght loaded around the 800.
A tug will be aroud the 700, as also the small cruiser in the end of the nineteen century will goes from 400 to 700.
Do someody as some hands on information on passing the 1000 on small vessel, around 14' to 16' in waterline?
Is somebody allready study the result by testing, or built an extremly heavy small vessel?
I would like to compere our finding.
I tryed already the the ratio 1010 on a model of 32" waterline, and I it find very powerfull and no big trouble. Of course the speed was not high, and speed is not a priority. Speed ratio from 0.9 to 1.1 is what expected
I am investigating unusaly heavy very small sailing boat (around the ratio 1000 and up). It is slightly unusal, but an interresting vessel can result.
Cheers
Daniel

[baeckmo]

Please define your "displacement length"!

[FAST FRED]

It is slightly unusal, but an interresting vessel can result.

Plan on a huge sail area if the boat is to be useful in light winds.

FF

[Ad Hoc]

Daniel

I don't follow your L/D ratio numbers, they are too large.....are the values imperial you are using or... something?

[dskira]

Originally Posted by Ad Hoc

Daniel

I don't follow your L/D ratio numbers, they are too large.....are the values imperial you are using or... something?

Yes John, indeed they are extremely large.
I use in imperial Diplacement Lbs /2240/(0.01*Lwl(Ft))3
It is my intention to investigate to be between 800 to pass the 1000.
The first model was fine, but it is normal for a heavy model to be around 1000 and when scale up to the real size the ration fell to 350. As larger the vessel the smaller the ratio.
But my research will be on very small craft, around 14' in Lwl. Yes it will need quite a sail area, and that is intended, mostly spread longitudinaly.
The goal is to achieve with a very high prismatic coeficient around 0.66 to 0.70 and a waterline coeficient around 0.77 to 0.8 a very small boat with some comfort and power to continue sailing by adverse condition.
I had in ime a 18' who was 1.6 Lt. (D/L 268). For experiment I loaded it with 1 long ton of lead inside and since the extremity was straigth the waterline length didn't change (D/L 438)
I find it was in the right direction for smooth sailing in bad condition. My research is always for one man operation.
Then life took over, and the expriment stayed put!
And since in the extremely heavy fishing vessel built never had sail, I didn't have feed back of course.
Yes Fast Fred, you right, I think an interresting vessel can be done.
To tell you the truth the experiment is for myself. It is for me the time to built a little boat to explore by myself the beauty of the North Atlantic, since been guest on a boat, start to bug me. I am quite a looner.
I want a small, very small boat, but as heavy my experiment will show the possibility. For the moment the design is 14' Lwl, 5170 Lbs, D/L 808,PC 0.66.
I have BM of 1.2' and a ballast ratio at 64%
Also the reason of this experiment is that the skipper is not as fit as he should be
I have to do a model, to check.
Cheers
Daniel

[baeckmo]

Aah, Ad Hoc, what a relief to find there were others uncomfortable with the D/L as well....... felt stupid in my isolation for a while!

Anyway, when kids were still small and handy here, we used to have a "Daddys racing around the island"-weekend in all the Optimist dinghies available. Used to collect a dozen and half of entrants... Madly fun!

My point is; an Optimist with an adult male in good fit, provided with a decent supply of beverages and food for a good night with friends, all clothing thorougly soaked due to repeated capsizing (very liberal competition rules....) is probably very close to your 3.0 in slenderness, and it is still sailing. Oh sorry, that would be about 1000 when using man's extremities for measuring.... . So scale up, bigger boat, more beer, more fun!

[Ad Hoc]

Daniel

Is that why the US still clings to imperial...because then your numbers are bigger than mine???

[dskira]

Originally Posted by Ad Hoc

Daniel

Is that why the US still clings to imperial...because then your numbers are bigger than mine???

You are right John, here we have big ego, everything as to be bigger.
I finished the lines of the prototype, I will post them next week and the numbers just for curiosity. I will be very interrested to have your input.
Cheers
Daniel

[lewisboats]

Here is a doodle (design noodle) that I did for the Around In Ten proposal...10 ft long and .883 long tons displacement. Reminds me of a Civil War Bullet. Lotsa displacement to length here. There is actually 6 ft standing headroom along the center line of the boat to a width of about 12" for 2ft. or so. Motive power would be a fully battened balanced lug. Beam is a massive 5.85 ft so this is basically a carved weighted buoy that can be moved in a general direction. Biggest problem is that 500 lbs of weight needs to hang under the box keel...so the box keel/hull connection would be under a large amount of stress.

[dskira]

Originally Posted by lewisboats

Here is a doodle (design noodle) that I did for the Around In Ten proposal...10 ft long and .883 long tons displacement. Reminds me of a Civil War Bullet. Lotsa displacement to length here. There is actually 6 ft standing headroom along the center line of the boat to a width of about 12" for 2ft. or so. Motive power would be a fully battened balanced lug. Beam is a massive 5.85 ft so this is basically a carved weighted buoy that can be moved in a general direction. Biggest problem is that 500 lbs of weight needs to hang under the box keel...so the box keel/hull connection would be under a large amount of stress.

Hi D/L will be 819.64 which is heavy but since the boat is very short, nothing wrong.
Good luck
Cheers
Daniel

[lewisboats]

Just a thought exercise...not likely to every be built unless I win the Powerball.

[Fanie]

At 10ft or 3m long she's going to rock a lot to the fore and aft...

[frank smith]

Originally Posted by lewisboats

Here is a doodle (design noodle) that I did for the Around In Ten proposal...10 ft long and .883 long tons displacement. Reminds me of a Civil War Bullet. Lotsa displacement to length here. There is actually 6 ft standing headroom along the center line of the boat to a width of about 12" for 2ft. or so. Motive power would be a fully battened balanced lug. Beam is a massive 5.85 ft so this is basically a carved weighted buoy that can be moved in a general direction. Biggest problem is that 500 lbs of weight needs to hang under the box keel...so the box keel/hull connection would be under a large amount of stress.

I did a few noodles for the Around In Ten . No easy solutions , you need every inch of water line , and the box keel is a good way to spread out the displacement . It is still an interesting exercise.

[lewisboats]

The keel was actually a method of allowing standing headroom (for dressing, stretching etc) while at the same time keeping the Displacement within reasonable limits. It functions as a limited foil and a storage space for heavier items. I tried a bit different hull with really slack bilges but it just didn't work out the way I wanted...the standing room wasn't there and yet the displacement was. I didn't like the trade off.

[frank smith]

You pick up huge amount of displacement if they are wide and deep . But you can pick up buoyancy in the ends without the penalty of a high PC # .
I think that the increased buoyancy demands hard bilges , with the upper hul most like a garvey . I tried inverting the vee in the upper hull , to end up with a tri type hull . I think it might be a way to go . But anyway the increase in carrying capacity and pitch damping make the box keel interesting .