How does a chine work?

[Rustic Charm]

Wow, what a discussion.

I know nuthink about yacht design, but my 36 footer has two on each side. All I can say from her performance is that when heeled, she doesn't roll as much as boats without chines.

But I thought chines were simply because the builders found it easier than making a round hull.

[Pelagic]

I just wonder where they decided to put the chine on this baby ?

http://gcaptain.com/austrian-company...Captain.com%29

[Dockhead]

Originally Posted by Rustic Charm

Wow, what a discussion.

I know nuthink about yacht design, but my 36 footer has two on each side. All I can say from her performance is that when heeled, she doesn't roll as much as boats without chines.

But I thought chines were simply because the builders found it easier than making a round hull.

You are right -- chines arose from builders trying to make boat or ship hulls with sheet goods, and can still be seen on home-made steel boats today.

All the rest is a question of form stability. For a good primer, see: Stability @ sailtheory.com

Basically form stability is all about how the forces of buoyancy of the boat stabilize it. How the vectors of those forces change with heel angle or other motions of the boat, resisting heel (or pitching etc.).

Flatter, wider boats have more form stability than narrower, rounder ones. Chines allow boats to be built with flatter bottoms but without the great increase in beam which would result if the curve of the bottom were constant.

[Rustic Charm]

Originally Posted by Dockhead

You are right -- chines arose from builders trying to make boat or ship hulls with sheet goods, and can still be seen on home-made steel boats today.

All the rest is a question of form stability. For a good primer, see: Stability @ sailtheory.com

Basically form stability is all about how the forces of buoyancy of the boat stabilize it. How the vectors of those forces change with heel angle or other motions of the boat, resisting heel (or pitching etc.).

Flatter, wider boats have more form stability than narrower, rounder ones. Chines allow boats to be built with flatter bottoms but without the great increase in beam which would result if the curve of the bottom were constant.

Even I understood that explanation. cheers

[Polux]

Originally Posted by Jim Cate

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


...
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.....

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

Jim

But I do, it means exactly this:

Originally Posted by Polux

..
... Chines increase form stability without increasing beam. Period! No compromise here.

I may have misunderstood you since it seems to me that you were specifically talking about a compromise taken regarding beamier boats not to make them more beamier. In fact chines work the same way on a beamy hull or on a narrower one. The effect and gains are the same and probably even more interesting on a narrow one since on that one the form stability (and initial stability) is small anyway and will gain more in being bigger.

[Polux]

Originally Posted by Suijin

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.

Yes off course, but you are wrong in thinking that I am talking about my opinion regarding it, I don't know enough to have an independent opinion. I am just following the opinion of those Nas, that contrary to Bob Perry, had developed modern chines, that had used them on hundreds of racing boats and are using then now on cruising boats. You are right in assuming that experience is fundamental to have a meaningful opinion about a subject.

[Polux]

Originally Posted by 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

That is the old type of chines that were used back on the 60's and 70's, the ones that were near the waterline (at the stern). They also increase stability particularly if the LWL is long and some amazing boats (for the time) were made using them, particularly a cruiser racer designed by Vand de Stadt, a radical boat that was against everything that was known in what regards the design of fast boats. It was assumed that to be fast they had to have smooth rounded hulls and then he designed Black Soo in 1957:





Look at that keel, look at that rudder and hard chines and think about the other "fast" boast designed in 1957 and look at how she still sails:

[Suijin]

Originally Posted by Polux

Yes off course, but you are wrong in thinking that I am talking about my opinion regarding it, I don't know enough to have an independent opinion. I am just following the opinion of those Nas, that contrary to Bob Perry, had developed modern chines, that had used them on hundreds of racing boats and are using then now on cruising boats. You are right in assuming that experience is fundamental to have a meaningful opinion about a subject.

Those people are not posting on this forum or in this thread. In fact, you have not cited any opinions from those NAs about chines at all, only pointed to boats that have been produced and then provided your own interpretation and conclusions about the hydrodynamic properties of chines.

Just because Bob Perry does not use chines on his boats does not mean that he does not understand them. It simply means he thinks they are ugly or that he has decided not to use them in his designs for other reasons that he has not articulated.

[Cadence]

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.

[Cadence]

Originally Posted by Suijin

Those people are not posting on this forum or in this thread. In fact, you have not cited any opinions from those NAs about chines at all, only pointed to boats that have been produced and then provided your own interpretation and conclusions about the hydrodynamic properties of chines.

Just because Bob Perry does not use chines on his boats does not mean that he does not understand them. It simply means he thinks they are ugly or that he has decided not to use them in his designs for other reasons that he has not articulated.

I think you nailed it about Bob Perry. He would definitely understand the dynamics involved with chines. He probably does think they ate ugly since his designs are elegant.

[Suijin]

Originally Posted by Dockhead

You are right -- chines arose from builders trying to make boat or ship hulls with sheet goods, and can still be seen on home-made steel boats today.

Not just home-made steel boats...on the majority of professionally produced steel and aluminum boats still being made. It is dramatically less expensive to fabricate boats in metal without complicated compound shapes to the panels.

[Delancey]

Far Harbor 39 designed by Bob Perry. Interesting concept for those who don't like ocean passages. Looks like a fairly short rig, which I presume is designed to lay flat on the pulpit and cabin top when it goes in a box.

http://www.containeryachts.com/container_yachts.swf

https://www.youtube.com/watch?v=SD7UQH7gShM

[David M]

Upside: Increased righting moment, decreased leeway, increased ability to plane, decreased tendency to roll while not on a plane.

Downside: more wetted surface area (drag) per amount of volume (buoyancy). Remember that a sphere has the lowest wetted surface area to volume ratio. This means that as a hull gets further and further away from looking like a sphere then the wetted surface area to volume ratio increases. At the turn of the bilge, a chine is going to have more wetted surface area than a smooth curve.

Name: Turn of the bilge (n)
Definition: The part of the bottom of a ship where the relatively flat shape begins curving up to form the topsides.

Source: Nautical Dictionary, Glossary and Terms directory: Search Results

[Cadence]

Originally Posted by Delancey

Far Harbor 39 designed by Bob Perry. Interesting concept for those who don't like ocean passages. Looks like a fairly short rig, which I presume is designed to lay flat on the pulpit and cabin top when it goes in a box.

http://www.containeryachts.com/container_yachts.swf

This does not look like Perry's normal deigns. It appears to be for a specific purpose. Like fast. It is soft chinned but not far from hard chinned. Under water cross section can vary greatly. It is not round bellied like cruising designs.

[Polux]

Originally Posted by David M

Upside: Increased righting moment, decreased leeway, increased ability to plane, decreased tendency to roll while not on a plane.

Downside: more wetted surface area (drag) per amount of volume (buoyancy). Remember that a sphere has the lowest wetted surface area to volume ratio. This means that as a hull gets further and further away from looking like a sphere then the wetted surface area to volume ratio increases. At the turn of the bilge, a chine is going to have more wetted surface area than a smooth curve.

Name: Turn of the bilge (n)
Definition: The part of the bottom of a ship where the relatively flat shape begins curving up to form the topsides.

Source: Nautical Dictionary, Glossary and Terms directory: Search Results

Yes if you were talking about the old chines that were used on that Van de Stadt boat that I posted, no with the new chine concept since they are not designed to be immersed but to prevent more resistance to immersion. Those boats are not designed to be sailed over the chine, but till the chine.