on bows shape

[Corso]

What are the pros and cons of the behaviour of a full bow, example: Gartside's Surprise, compared to an overhanging bow, example: Buzzard's Bay. (im not comparing the two boats, they are just to explain myself and someone might even have better examples).
I know that a really buoyant transom isnt good in following seas and could be even not so seaworty, exist the same thing for bows?
And to which extent there is a relationship in between a bow and a transom? (i know the basics of it but, on the extremes, what would happen to a double ender with a full bow?).

[Ian McColgin]

When I was young, Spaulding Dunbar told me there were three sorts of bows. Those good in a head sea - very sharp. Those good in a following sea - rather full. And those good for nothing.

Not exactly true but a good bon mot.

The bow has three major parts: below water, waterline, and above.

In a sail boat this is much complicated by the fact that the bow will approach the water at radically different angles.

Once upon a time bows on off-shore boats were plumb to pierce the waves and bows on racing boats were very long because the rating rule only measured static waterline length and a long overhang gave what amounted to a penelty-free bigger boat.

If there ever was a rule that encouraged very wholesome sailboat bows it was the old CCA rule. Look at the S&S designs through the '60s for numerous examples. The IOR rule encouraged very pinched somewhat plumber bows which I think are nasty.

A fine bow, perhaps with a bit of hollow in the waterlines ala LFH, is generally a bit faster. A bit of bouyancy above the waterline so the boat doesn't plunge too much in a seaway is generally good. Some designers like John Alden had their own personal favorite. You can spot an Alden bow a mile off and if you're wrong it's because it was drawn by one of his many disciples like Agee Neilson or Carl Alberg. But even Alden did the occasional clipper bow.

Atkins had a slightly different approach to bows but certainly a good one.

LFH consumated his family heritage of incredible bows.

The bow is just the pointy end. A boat's lines must harmonize all the way along, which is why one designer will show quite a few different bows depending on the total boat.

[John E Hardiman]

Bows are marvelously simple things that all boats and ships have. All they have to be is:

Sharp enough to reduce drag but full enough to lift the hull;

Deep enough to improve tracking but shallow enough not to impede turning;

Narrow at the deck enough to reduce butting the seas but wide enough at the deck to work the rig and support the ground tackle;

V shaped enough to cut through chop but U shaped enough to prevent the head from being pressed down while running;

Harmonious with the style of the hull as to not be obvious yet distinctive enough to be individualistic.

:D

In the big picture, the volumes and the overhangs of the bow and the stern should be balanced to moderate the behaviour of the hull. As to the rest, thats all up to the intended purpose of the hull.

[Ian McColgin]

Actually, one of the earliest attempts to bring science to boat design created the 'cod head and mackrel stern' shape. I've forgotten who it was launched a series of experiments about how water actually flows and he came to believe that if you could duplicate the shape that a chunk of ice naturally takes when slightly warm water flows past it, that would be the nicest thing.

The theory was wrong but it was a start.

My two kayaks look a little alike to some people, though the Nigel Foster 'Shadow' has hard chines and the Nordcap is round bottomed. Even though the bows look much alike, the Nordcap's deceptivly fine entry makes almost no bow wave while the Shadow sholders the water aside.

[Corso]

ok i understand that without a particular hull to take as example the whole discussion would be pretty vague.

Thanks for the replies, ill let the question drop and maybe resurrect the thread when ill came up with something more precise.

[Ian McColgin]

Ted Brewer wrote a nice primer on boat design that you will like.

[Corso]

"Understanding boat design" eh?
ill get it from the library

[Lucky Luke]

John :D