Hard chine

[Jimmyb57]

Hard chine seems to be the marketing pitch these days. Is it a benefit? I understand that you will stay flat longer, but at some point do you suddenly heel, versus gradual heel without hard chine?

[Bill O]

There is also slamming associated w/hard chines. Nothing worse than sending a shutter through the boat after a good slam.

Nicer to have rounder sections. They heel over then stabilize, less slamming

[Manateeman]

Bill O is right on the money. It’s cheaper to build. Guess who profits.
Boatbuilders give the customers what they want. Fast and cheap.
The Principles of Yacht Design ...great book.
Happy trails to you.
Mark and his manatee friends.

[psk125]

Hard chines aft seem to provide extra stability on a broad reach, especially with big asymmetrical sails. You sail fast and flat. This is quite marketable. The chines also create big spaces below decks for cabins in the stern quarters of the boats. This is good for sales too. Ballasted keels keep the boats generally on their feet, so going beyond the "tipping point" is not overly worrisome.

[Dr. D]

Originally Posted by Jimmyb57

Hard chine seems to be the marketing pitch these days. Is it a benefit? I understand that you will stay flat longer, but at some point do you suddenly heel, versus gradual heel without hard chine?

“Hard chine” is a misnomer. “Chine” means a sharp change in a curve.

No, there is no flat to sudden heel. The boat begins to heel, then as the chine goes into the water there is more resistance to further heeling. Another benefit is the hull will plane sooner.

I don’t know why the other posters claim a chine means the boat will slam. When out sailing I observe other boats. In conditions where mine (which has the dreaded chine) is slamming, I see other boats doing the same. Even the “slender” hull boats. Slamming is due to height, period, and angle of the chop. The aft conformation of the hull is not a factor.

[rslifkin]

General hull shape and pointiness up forward should mostly determine if a hull pounds. Unless it has very wide chine flats, a hard chine shouldn't cause pounding.

[chrisr]

most of the chines you will see in production white boats these days are there for rating purposes in the racing version.

to be avoided for any other reason

cheers,

[Diamond-Esp]

As an owner of an aluminium yacht with chines I couldn't be happier. This is my fifth yacht, all GRP with rounded sections beforehand. As to the slamming, not an issue, it's about hull shape and a good design and build will be fine. Admittedly my hull is 8mm but I do sail in the southern ocean!

The yacht heals as any other yacht would, the only difference is when I reach a certain angle the chine seems to dig in and off she goes.

I believe if your considering a chine yacht there is a lot more to consider than this factor alone, design as a whole is more important.

[B23iL23]

Total nonsense.

Chines are put in for many reasons but cost if not one of them. With a chine you can get more form stability from a boat - it will heel to the chine and then not want to push over any more.

Second the chine adds more volume down below. You can have a narrower waterline which means more slippy, while it flares out above the waterline to make cabins wider.

Chines with a wider beam are everywhere now as they produce fast boats with lots of space and a stiffness that makes them easier to sail.

Originally Posted by Manateeman

Bill O is right on the money. It’s cheaper to build. Guess who profits.
Boatbuilders give the customers what they want. Fast and cheap.
The Principles of Yacht Design ...great book.
Happy trails to you.
Mark and his manatee friends.

[danstanford]

Any answers to the OP's question about rate of heel after the stability of the chine is overcome? I thought it was a good question but I am only an observer if boat design rather than any kind of expert so my answer is just a guess.
Dan

[B23iL23]

Yes - The hard chine, when sailing on a reach, adds significantly to stabilize the boat. Going upwind the leeward chine also works as additional stabilization as it tends to lift the boat higher. So the boats need less ballast which makes them lighter and faster.

Basically the boat doesn't want to heel beyond the chine and so you get a more stable platform.

Originally Posted by danstanford

Any answers to the OP's question about rate of heel after the stability of the chine is overcome? I thought it was a good question but I am only an observer if boat design rather than any kind of expert so my answer is just a guess.
Dan

[psk125]

A flat-bottomed barge with square sides (chines) will resist heeling very well until a certain point. Then it will flip over (or slide under). Naval architects work to avoid this by angling the upper topsides out (to make it harder to reach the "tipping point")and by adding decks to keep water out. Optimist dinghies are quite stable most of the time, but they have been known to capsize. The same thing applies to just about any boat- it just depends upon the conditions they're out in.

[Sparx]

Originally Posted by danstanford

Any answers to the OP's question about rate of heel after the stability of the chine is overcome? I thought it was a good question but I am only an observer if boat design rather than any kind of expert so my answer is just a guess.
Dan

I have owned two hard chine sail boats. Both sail flat and fast. I can feel when a gust submerges the chine; the boat stiffens significantly and accelerates away. Once the chine is submerged it takes a great force to push the boat further over. I found both these boats to have superior stability even when hard pressed.

A well designed hard chine boat when first submerging the chine will have some small percentage of the waterline length submerged at the chine. A small increment in heeling will quickly submerge maybe twice the length of the chine, drastically increasing the righting forces.

[Hesti]

A single hard chine can help a light boat to plane when reaching or going downwind.

Also, a single hard chine can add form stability as already written above. Form stability has its pro and contra like anything - the pro is, that it increases sail carrying ability (which could also be used to reduce keel weight as already written above). The contra is, that the boat will move more from side to side in a seaway coming from the side, which is more tiring for the crew.

As your wetted area is bigger than on a round chined hull, low wind speed (well below hull speed) might be impaired.

When you built from sheets like plywood or metal, a single hard chine can be easier and cheaper to build than multi-chine or round chine.

It's horses for courses.

[wingssail]

Originally Posted by chrisr

most of the chines you will see in production white boats these days are there for rating purposes in the racing version.

to be avoided for any other reason

cheers,

There is no rating benefit for adding chines to a race boat.

Chines first appeared in large numbers of boats due to construction requirements of flat panels. Think plywood=Thunderbird sailboat, think Aluminum=Ovni sailboats. This was neither a rating benefit or to increase stability although increasing form stability is a benefit of hard chines mid-ships, I doubt it was a significant reason for doing it.

In recent years racing designs featured chines aft to allow a flatter, wider running surface aft, which promotes higher speeds. This was not for rating reasons. Popular production designs copied the look, I think for marketing reasons, and there is a benefit in added space inside although that is more a function of the width of the hull more than the chines themselves.

Pounding is a function of flat surfaces which are presented to waves, in the bow! Few boats have chines in the front. Flat runs aft however may not cause pounding but do offer more surfaces for slapping while at anchor. One consideration when looking at pounding is that a chine forward becomes a "V" when heeled, so some argument could be made that chines reduce pounding when heeled over, except that requires a boat to be sailing upwind which is not often the case for cruising boats. Most of the delamination of racing boats due to pounding has been in the flat sides of the bow area which strike the waves while heeled over, not the bottom.

Form stability is real and any boat with a hard turn to the bilge (as in chines) will offer more of it. So a boat which floats on a narrow waterline, then immerses much wider portions of the hull as it heels has form stability. It must be mid-ships, not all the way aft, to account for much.