Two Questions Regarding Draft and Stability

[barnakiel]

Extra beam gives you extra shape stability but exposes you to many issues if the sea is very rough. Unfortunately, you cannot have both. So, since getting a very, very, very ;-))) beamy boat is not practical, I think you will be looking for a NARROW hull.

Look Marchaj up. He discuses the problems thoroughly.

b.

[Elemein]

Weyalan,

Planning for the future, yes I am. Little experience in sailing? I wouldnt say little, but rusty, and I've only just entered Bronze IV (if you have taken sailing instruction in USA or CAN, then that makes a lot of sense) and I never plan on letting draft decide what boat I get. 8' of draft? Wowza... Looks like draft wont keep me from much anymore... Less thoughts on draft for me, thank you Weyalan.

barnakiel,

Interesting, I never thought of it that way actually, I was thinkin that it seems something like a cat never seems to have any stability issues... But thats a cat- not a monohull.

Marchaj? Will do. I'll take a look into it after a break.

[markpierce]

Originally Posted by barnakiel

Extra beam gives you extra shape stability but exposes you to many issues if the sea is very rough. Unfortunately, you cannot have both. So, since getting a very, very, very ;-))) beamy boat is not practical, I think you will be looking for a NARROW hull.

Don't recall seeing a narrow life-raft either.

[Weyalan]

Originally Posted by barnakiel

Extra beam gives you extra shape stability but exposes you to many issues if the sea is very rough. Unfortunately, you cannot have both. So, since getting a very, very, very ;-))) beamy boat is not practical, I think you will be looking for a NARROW hull.

Look Marchaj up. He discuses the problems thoroughly.

b.

I wasn't suggesting a beamy boat was a desirable thing per se. But for a given aspect ration (length versus beam), as the boat gets bigger, so does the beam. Therefore bigger boats tend to be better in a storm than small.

[boatman61]

Originally Posted by Elemein

Okay, so question 2 is answered, but not the first one...

I get it, downwind, you dont want a boad hanging downwards else you trip or pivot, even in a gale, going directly downwind on a run can't really affect you (you're running away from the waves [mostly], away from the possibility of tipping [your going downwind], and away from the possibility of getting hit hard by any waves) but the thing is, if you're going upwind- you want the board UP to remove that possibility of pivoting or swinging over, and you want the sails down (this is UPWIND to remind you) so that you remove the possibility of tipping over.

Am I right? Or am I still missing something? Please correct me, chances are, I got something wrong

Good chance...
One thing you'll find is waves are not directionally stable... that is to say they can come from up to 3 different directions depending on prevailing swell and conditions 12 to 24hrs previous to the 'current conditions'
If your stern gets hit by a quartering wave as you crest a wave from the stern the effect pushes your stern sideways.... the board down will act as a pivot point accelerating your swing off line... for a short while you will lose steerage and the chances are the following wave will catch you beam on and broach you... especially if its a growler... (Breaking wave)
Board down is for sailing INTO the wind... your not going to tip over unless you've way to much sail up and get sucked outa the 'slot'.... then your in the **** if its a big sea...lmao

[Weyalan]

Originally Posted by markpierce

Don't recall seeing a narrow life-raft either.

Sure, but revisions to the SOLAS regulations (after the Estonia ferry didaster) now require that all new (commercial) inflatable liferafts be inherently automatically self-righting. The problem was, during the Estonia disaster, was the many of the liferafts actually inflated upside down (because, during inflation, the water pockets that are supposed to prevent the liferaft from going upside down, had not yet filled with water). So, once the liferaft actually was upside down, it was very difficult to right (it involves trained crew getting into the freezing water to try to right it). In this instance the wide beam of the liferaft was a hindrance to righting.

[Elemein]

Thanks boatman61,

That clears a lot up, that sort of made me hate fin keels though (now I love centreboard keels in addition to full keels)

May I ask a question furthermore though?

What do I do if the prevailing wind is coming from one of my sides? I would imagine to put the boat up since a wave hitting right on the broad of a boat MUST have a very great pushing force to a side, and without a pivot point, it is a lot less deafening... Though yes, what do I do if wind is coming from a side?

[delmarrey]

Originally Posted by Elemein

Alright, I decided that I want a boat that is unshakable- even in a storm. I know that a boat like this would have a good displacement, a full (or NEXT to full) keel, and a wider width. Now, those things add to the draft, and commonly, boats of that nature that are around the 36' to 43' have a draft of 6'+... I find this to be unreasonably deep, atleast for most marinas it is... As said, I want a full keel boat with heavy displacement- a boat that will live through a storm in the Atlantic as I throw the sea anchor windward, batten down the hatches, and watch classical movies. A real, stable, seaworthy boat.


Edit : Opps, forgot to mention. Bluewater boat of course.

What you need is one of these.

[barnakiel]

Originally Posted by markpierce

Don't recall seeing a narrow life-raft either.

A life-raft is a poor example. Let me remind you that of the people who left their sinking boats in life rafts 7 lives were lost at Fastnet.

None of these boats actually sank.

So much for life raft as an example of safety.

If you are now tempted to quote a catamaran, please save your breath ;-)

barnie

[barnakiel]

Originally Posted by Weyalan

I wasn't suggesting a beamy boat was a desirable thing per se. But for a given aspect ration (length versus beam), as the boat gets bigger, so does the beam. Therefore bigger boats tend to be better in a storm than small.

Eureka!

;-)
b.

[Adelie]

Originally Posted by markpierce

Last I checked, life rafts have little draft.

Great in heavy weather, but a real pain to sail close hauled between storms.

[Adelie]

So with a centerboard here's what I think you should do:

Sailing downwind, board is up decreasing drag and lessening the chance of a broach.

Sailing upwind board is down providing more and better shaped lateral area to resist lateral sail pressure.

Heaved to the board is up so the boat does not 'trip' over the board and roll more when a wave pushes the boat laterally.

The concept here is without the board, the boat is essentially a rather shallow full keeled boat with ballast in the fixed part of the keel. This ballast provides the inherant stability of the boat. The board is only weighted enough so it doesn't want to float up into the trunk of it's own accord or under the pressure of water flowing past it. The board does not provide any significant increase in ballast, it's only purpose is to provide a more efficient underwater shape when going to windward.

[boatman61]

Damn.... I wish I could be that concise.....

[barnakiel]

Originally Posted by Adelie

.. Sailing downwind, board is up decreasing drag and lessening the chance of a broach...

... Heaved to the board is up so the boat does not 'trip' over the board and roll more when a wave pushes the boat laterally...

Hmmmm...

Just asking.

Downwind the board is up but maybe not all the way up?

I can remember my Finn broaching wildly with the board fully up. Lowering the board a bit helped a lot.

Hove to the board will have to be down perhaps?

I mean - if you keep it up then how do you keep the boat hove-to? Will she not bear off?

barnie

[Elemein]

Thanks everyone! (espiecally Edelie)

My questions have been THOROUGHLY answered through and through- I am now seriously contemplating a centre-board as my keel, as it adds a whole new dimension to sailing AND safety (of course, safety is always #1 when you're in the middle of absolute nowhere) and I now know more what the whole purpose of centreboards are.

Later on in whenever, I my ask about full keels, as now I'm thinking when a wave hits a boat from the side (direct side) the boat may be pushed in the direction on the wave (not by riding the wave, but by the brute force of the wave).

Anyway thanks.

And good question barniekiel, I could use that answer under my belt also