How does a chine work?

[Polux]

Yes, David de Prémorel, a yacht designer and structural engineer on Finot/Conq cabinet design was talking about a cruising boat when he made those explanations posted by Neil about the use of chines on performance cruising boats.

Some more:

"Walking around the hull revealed one of its most striking design features: a
prominent hard chine that extends from bow to stern and very steep hull
sides above it, which directly derive from Finot-Conq’s experience of
designing Open racers.
In simple terms, this hard chine is an artefact that allows you to increase the power of the boat without increasing its width.. without the chine it would be at least a metre wider. but if the hull is too wide, power is compromised by other disadvantages, not least in terms of additional weight.
By power, Finot-Conq refers to the righting movement of the boat, which
has a direct influence on its speed.

Basically, the bigger the righting moment, the bigger the heeling
moment that can be applied. It follows that the larger the righting moment,
the larger the sails can be for a given wind speed. If the boat carries more
sail, it can harness more propulsive power from the wind and go faster. "

http://www.maxidolphin.it/wp-content...March-2013.pdf

What he says applies to the Maxy yacht he is talking about, or to any kind of sailing boat: We all want more power with less beam and faster cruising boats.

This is the beauty he is talking about:

https://www.youtube.com/watch?v=kZkZ5zF4miA

Don't miss the movie on the link that is a lot better:

A bord de Nomad IV

[Dockhead]

Originally Posted by Polux

Yes, David de Prémorel, a yacht designer and structural engineer on Finot/Conq cabinet design was talking about a cruising boat when he made those explanations posted by Neil about the use of chines on performance cruising boats.

Some more:

"Walking around the hull revealed one of its most striking design features: a
prominent hard chine that extends from bow to stern and very steep hull
sides above it, which directly derive from Finot-Conq’s experience of
designing Open racers.
In simple terms, this hard chine is an artefact that allows you to increase the power of the boat without increasing its width.. without the chine it would be at least a metre wider. but if the hull is too wide, power is compromised by other disadvantages, not least in terms of additional weight.
By power, Finot-Conq refers to the righting movement of the boat, which
has a direct influence on its speed.

Basically, the bigger the righting moment, the bigger the heeling
moment that can be applied. It follows that the larger the righting moment,
the larger the sails can be for a given wind speed. If the boat carries more
sail, it can harness more propulsive power from the wind and go faster. "

http://www.maxidolphin.it/wp-content...March-2013.pdf

What he says applies to the Maxy yacht he is talking about, or to any kind of sailing boat: We all want more power with less beam and faster cruising boats.

This is the beauty he is talking about:

Don't miss the movie on the link that is a lot better:

A bord de Nomad IV

Sounds like we've all figured how how chines work on sailing boats. Good .

Where did the OP go? I think we answered his question.

[Polux]

Originally Posted by Dockhead

Sounds like we've all figured how how chines work on sailing boats. Good .

Where did the OP go? I think we answered his question.

nice!

[Jim Cate]

Originally Posted by Dockhead

Sounds like we've all figured how how chines work on sailing boats. Good .

Where did the OP go? I think we answered his question.

Well, what a lot of interesting posts!

And yes, these last few have indeed answered my question to my satisfaction.

The chine itself does not have a direct hydrodynamic effect. It is rather an artifact that allows the best compromise between form stability and acceptable beam width... and even the hot shot NA mentions aesthetic considerations, ie styling.

Thank you all for your contributions.

Jim

[Cadence]

Originally Posted by Dockhead

That sounds very reasonable to me

What it boils down to is this: introducing a chine allows you to make the bottom flatter without increasing the beam. That is, the radius of the curve of the bottom can be greater, which provides greater resistance to rolling/heeling without increasing wetted area. In other words: the greater the radius of the curve of the bottom, the more the buoyancy of the boat is distributed to resist rolling/heeling -- the very definition of form stability.

But as you increase the bottom curve radius, the beam of the boat gets wider and wider, which has a negative effect on stability (cf "capsize screening ratio"). So you introduce the chine to allow the topsides to go straight up from the heeled waterline (or thereabouts) and limit the beam, so that you aren't hurting the stability of the boat with your increased bottom curve radius. It gives you the possibility of greater bottom curve radius without a proportional increase in beam.

So the chine itself does nothing except get you around an unacceptable increase in beam. You can radius the chine without reducing this effect -- as Bob Perry mentions.

It would be nice to have a real naval architect weigh in, but that sounds right.

And if this interpretation is correct, then the chine in a sailboat performs a completely different function than the chine in a planing powerboat hull.

The last paragraph is no lie! Except!

[Suijin]

Originally Posted by Polux

I would appreciate that you don't put me sayng things that I did not said. What i said it was that Bob Perry had no experience in what regards designs with top racing boats with chines (modern chines like they are used on the solo racers or on the Oceanis 38) and that he does not use them on his ocean performance cruisers, that are rather few on the last decades, and are not top racing boats anyway.

The only one that could fit your description is Icon, a 65ft, but it is a fast performance cruiser or a cruiser racer and not a "sled" nor a top racing boat and most of all it has no chines.

Maybe you can tell me of what boat you are talking about regarding a Bob Perry designed over 45ft performance cruiser with chines? I don't know that boat and I know pretty well Bob Perry's work.

All I said was you dismissed Bob Perry's opinion regarding chines, which is what you did by asserting that he has no experience designing racing boats. If that was not your intent, please explain to me the point of your comments about his experience.

The design in question was never built, so you would not be familiar with it, although I think there is a cross section in his book, I'm not sure.

[Cadence]

Originally Posted by Suijin

All I said was you dismissed Bob Perry's opinion regarding chines, which is what you did by asserting that he has no experience designing racing boats. If that was not your intent, please explain to me the point of your comments about his experience.

The design in question was never built, so you would not be familiar with it, although I think there is a cross section in his book, I'm not sure.

Hay guys.

[Polux]

Originally Posted by Suijin

All I said was you dismissed Bob Perry's opinion regarding chines, which is what you did by asserting that he has no experience designing racing boats. If that was not your intent, please explain to me the point of your comments about his experience.

The design in question was never built, so you would not be familiar with it, although I think there is a cross section in his book, I'm not sure.

Not experienced regarding designing Solo Ocean racers, or top racing boats with chines, obviously because he had never done that.

[Polux]

Originally Posted by Jim Cate

Well, what a lot of interesting posts!

And yes, these last few have indeed answered my question to my satisfaction.

The chine itself does not have a direct hydrodynamic effect. It is rather an artifact that allows the best compromise between form stability and acceptable beam width... and even the hot shot NA mentions aesthetic considerations, ie styling.

Thank you all for your contributions.

Jim

Hum it seems you had a prejudice against chines from the beginning. It seems to me that your conclusion is not correct with what have been said:

First something that has not an hydrodynamic effect serves no purpose since it does nothing. Chines work, so they have an Hydrodynamic effect.

Than I don't understand what you mean with this: "an artifact that allows the best compromise between form stability and acceptable beam width."

What compromise are you talking about? Chines increase form stability without increasing beam. Period! No compromise here.

[Dockhead]

Originally Posted by Polux

Hum it seems you had a prejudice against chines from the beginning. It seems to me that your conclusion is not correct with what have been said:

First something that has not an hydrodynamic effect serves no purpose since it does nothing. Chines work, so they have an Hydrodynamic effect.

Than I don't understand what you mean with this: "an artifact that allows the best compromise between form stability and acceptable beam width."

What compromise are you talking about? Chines increase form stability without increasing beam. Period! No compromise here.

He means the chine itself does nothing -- it's the flatter curve of the bottom which the chine enables which provides the effect.

Here the difference with planing power boats is important -- for them, the actual form of the chine is important, since that feature in itself has an effect. For us, the form of the chine is not meaningful. It's an "artifact". Jim understood everything perfectly (not surprising; he's a very astute individual).

[Suijin]

Originally Posted by Polux

Not experienced regarding designing Solo Ocean racers, or top racing boats with chines, obviously because he had never done that.

That is a a dismissal of his opinions about boat design, with respect to chines. In all honestly, I'm disposed to give more weight to his general thoughts on the matter than yours. That is, unless you've designed some solo ocean racers, or top racing boats with chines.

[El Pinguino]

They put hard chines on modern 'cruising' yachts for the same reason they put fins on the 1958 Cadillac... to make them go faster.

[boatman61]

From the 'DORK' point of view it seems obvious to me... the change is from a flattish bottom to a V when the wind ahead of the beam.. and it works..
But then.. WTF do I know..
But then again.. having overtaken several ships while doing 17kts in a 26ft v hulled boat... I can only say..
V's and chines rock..
PS: Apologies to those who can only think 40ft +.... maybe big boats behave differently...

[Jim Cate]

Originally Posted by Polux

Hum it seems you had a prejudice against chines from the beginning. It seems to me that your conclusion is not correct with what have been said:

First something that has not an hydrodynamic effect serves no purpose since it does nothing. Chines work, so they have an Hydrodynamic effect.

Than I don't understand what you mean with this: "an artifact that allows the best compromise between form stability and acceptable beam width."

What compromise are you talking about? Chines increase form stability without increasing beam. Period! No compromise here.

My only response to this, Pollux, is to re-quote from an earlier post:


"Walking around the hull revealed one of its most striking design features: a
prominent hard chine that extends from bow to stern and very steep hull
sides above it, which directly derive from Finot-Conq’s experience of
designing Open racers.
In simple terms, this hard chine is an artefact that allows you to increase the power of the boat without increasing its width.. without the chine it would be at least a metre wider. but if the hull is too wide, power is compromised by other disadvantages, not least in terms of additional weight.
By power, Finot-Conq refers to the righting movement of the boat, which
has a direct influence on its speed."

This was simple enough for me to understand. Why is it that you can not?

Jim

[Panope]

Not really answering the original questions but I will echo what Boatman said. When the boat is healed over, the leeward chine is pretty well pointed down and is now behaving more like the center-line of an upright boats "V" bottom.

I believe that when in this healed over state, the water will be travelling perpendicular all along the chines length.

Steve