# Waterline for planing boat

Discussion in 'Boat Design' started by gpaladin, Aug 29, 2006.

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Instead of this :

Is there a rule by wich waterline for planing craft could be determined when the craft is at rest?

The question should be :

How can a good waterline heigth above chine be determined, so that when planing, a boat rests on its chine?

I am talking about 14 metres in length and 30-40 kn of speed.

I am aware that waterline is result of geometry and weight (mass) but I am interested in position of the waterline that should be appropriate for certain speed/length/displacement ratios.

Last edited: Sep 4, 2006
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### WillallisonSenior Member

In terms of comfort, the chine should be fully submerged when the boat is at rest, otherwise it will be very tender - not to mention noisy.
The chine generally exits the water at around station 4

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### T1MMYJunior Member

could you please explain what the 'chine' is and what 'station 4' is, thanx.

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### WillallisonSenior Member

on a normal planing hull, the bottom is v-shaped. The chine is the point where the bottom meets the sides.
Traditionally, when designing a boat, you divide the waterline length into 10 even divisions - stations. With 0 at the point where the bow meets the water and 10 where the transom meets the water. So station 4 is 40% of the waterline length, aft of 0

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You mentioned tender, and noise.

Could you please explain?

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### Raggi_ThorNav.arch/Designer/Builder

Timmy and gpaladin, are you joking?
Why not go to the library and read a book?
Sorry if this sounds unpolite

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### T1MMYJunior Member

sounds very impolite mate.

I simply did a search for powerboat forums so i could learn a little more about boats etc.. and get some advice on how to sort afew problems with mine and i saw a thread which looked interesting to me but didnt fully understand all the terms so thought it best i asked.

nowadays who uses librarys anyway? everyone i know uses the internet for info and to gain knowledge on something, mainly because it is far far bigger than any library and a book doesnt give a second opinion, which is always useful.

I use several car forums and the majority of them are friendly and helpful, but afew of them have unhelpful members who make comments like yours especially to newbies (such as myself) which really doesnt help the forum grow and become a 'community' if you like, all it does it creates a divide and you have very few new members, you current members all chat to each other for a few years, people lose interest and the forum becomes very quiet and eventually ha to start over again or dies.

sorry for going off topic, and sorry if that was impolite. simply my view.

if there was a glossary of terms somewhere on the site and i was directed to that, that would have been fine etc.....

lol, ill shut up now lol

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### Raggi_ThorNav.arch/Designer/Builder

Yes, I was afraid it sounded impolite, sorry fro that, as I said, and for my spelling .
But I think you (both) ask some strange questions, like "explain tender"

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### Raggi_ThorNav.arch/Designer/Builder

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### antonfourieSenior Member

Have a look on Amazon there are lots of books there for a coupla quid that explain all about powerboats

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### froshSenior Member

Hi T1mmy, not good form to criticize anyone when you still know nothing about boats. Try Google. Put in the word, then open the Wikipedia site. It is the encyclopedia of the internet and covers everything about boats as well.

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Well it sounds a bit impolite, but never mind.

Excuse me, I am not familiar with term tender when talking about planning hulls, and I would appreciate a short explanation.

Also I do not know where does the noise comes from if the chine is at or above the waterline. I can only guess what was meant by that answer and I would also appreciate a shor explanation about that.

It seems that my first question wasn't asked correctly.

I am not talking about hydrostatics in general here but I am talking about hydrostatic waterline.
For given displacement, L and Cb one can change B in order to change T. So If I make my boat narrower it will have bigger draft which can be identified as increase of waterline heigth above chine (I am not changing the angle of deadrise).

So to ask my question again.

How can a good waterline heigth above chine be determined, so that when planing, a boat rests on its chine?

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### T1MMYJunior Member

Hi frosh.
IMO it was perfectly fair of me to criticize him, and the fact i know little about boats has nothing to do with my criticism. Ok i should have searched for it first, just seemed easier this way at the time. if i knew you would all get this upset over a simple question i wouldnt have bothered.
My criticism was to do with the fat he was impolite and unhelpful, i mean come on, what is this forum about? surely its about helping out others, sharing information, gaining knowledge from other peoples experience and sharing your own knowledge, whether that be a great deal or a very small amount, forums can also be fun places too.

not trying to get peoples backs up here as its obviously a well established forum, with a great variety of members from all around the world, just expressing my views.

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Timmy. You have every right to ask questions. This is what forum is for.

If you want to educate yourself I would like to ask you how old are you?

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### T1MMYJunior Member

gpaladin, i am 19 years of age, out of interest, why do you wan to know this?

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