Formula for Mono-hull water line placement?

[MrSheep3]

I am drawing up a rough sketch of a boat I would like to build, one day when I get the money, and I do not know of a better way to find how much lead to put in the keel for the most efficient waterline through the water without contacting an engineer. I have done some research on air buoyancy per cubic foot, 64 lb positive pounds and how much lead ways but I do not know the exact science behind it. If any one knows how to please help me!

[donradcliffe]

I suggest you buy and read "Principles of Yacht Design" for starters.

[Snowpetrel]

Simpsons rule. Alternately download Carlson Hulls and freeship.

For a real quick and dirty method multiply the midships coeficent by the prismatic coeficent, the LWL, BWL and moulded depth. Use meters and the result will be near enough displacement in tonnes for fresh water.

[GordMay]

Greetings and welcome aboard the CF, MrSheep.

You are taking on a tremendous challenge!

FWIW:
➥ https://www.glen-l.com/weblettr/webl....html#notebook
➥ https://www.glen-l.com/weblettr/webl...-designer.html

[Dave Lochner]

Start with Principles of Yacht Design

Good Old Boat magazine has a boat review in each issue with an analysis by a naval architect. Those articles will serve as a good primer on design and considerations.

[Trinational]

The world doesn't need another cruising sailboat! There is no resale market, anywhere, for those that exist. Buy an old vessel and bring it back to as new condition.

[Cadence]

Originally Posted by MrSheep3

I am drawing up a rough sketch of a boat I would like to build, one day when I get the money, and I do not know of a better way to find how much lead to put in the keel for the most efficient waterline through the water without contacting an engineer. I have done some research on air buoyancy per cubic foot, 64 lb positive pounds and how much lead ways but I do not know the exact science behind it. If any one knows how to please help me!

Do yourself a favor and buy a set of plans from a naval architect. Better yet buy a boat.

[Cadence]

Originally Posted by Snowpetrel

Simpsons rule. Alternately download Carlson Hulls and freeship.

For a real quick and dirty method multiply the midships coeficent by the prismatic coeficent, the LWL, BWL and moulded depth. Use meters and the result will be near enough displacement in tonnes for fresh water.

I use Simpson's rules just for giggles. My calculus stinks. I think you only pointed out a few things that need extensive calculating. and not for the novice.

[stnick]

It will Take you years just to plan and unless you are a shipwright you will not understand how to fit counters and such in a curved surface. Lets alone glass in ribs etc.
Yup buy a old boat and have at it .

[David M]

There is software that naval architects use for making those determinations. People spend 4 years in college just learning how to become a naval architect.

I think you are making things too complicated for yourself starting from scratch by designing and building a boat from the ground up.

Wouldn't you rather be out sailing instead? Buying a used boat is the least expensive way of getting there. I say this because you said in your first post that money is tight.

[Don C L]

Are you thinking of a displacement hull or planing hull? How much sail area are you planning? What's the beam? If it were me, I'd go looking for similar designs already out there and see what they have to get the ball park figure.
In the mean time, there is a Spencer 35 in San Diego that is practically free, looking for a good home. You'd be hard pressed to build a boat stronger than that one. You could restore her while you design a new one!
Welcome aboard by the way!

[Don C L]

Originally Posted by Trinational

The world doesn't need another cruising sailboat! There is no resale market, anywhere, for those that exist. Buy an old vessel and bring it back to as new condition.

Welcome aboard, Trinational!

[Simi 60]

Originally Posted by donradcliffe

I suggest you buy and read "Principles of Yacht Design" for starters.

I suggest he just buy a set of plans - they are cheap enough.

[GILow]

Originally Posted by Snowpetrel

Simpsons rule. Alternately download Carlson Hulls and freeship.

For a real quick and dirty method multiply the midships coeficent by the prismatic coeficent, the LWL, BWL and moulded depth. Use meters and the result will be near enough displacement in tonnes for fresh water.

Well, reading that sent my brain out my ears.

And I reckon you made half of those terms up!

Prismatic Coeficent! Ptooey.

[GordMay]

Greetings and welcome aboard the CF, Trinational.