Hard chine

[yesthatsue]

Originally Posted by Manateeman

Bill O is right on the money. It’s cheaper to build. Guess who profits.

A fiberglass hull with a hard chine costs exactly the same to build as one without one. Possibly a bit more if the point of the chine is to carry more beam lower, increasing the boat's volume and the hull's surface area.

Hard chines in plywood, aluminum, and steel are cheaper and easier for amateur builders to build one-off, but production boats and their associated tooling are a whole different thing.

[wingssail]

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

A wide, flat, hull, (with chines or not) moves its center of buoyancy rapidly outboard when heeling while the center of gravity stays centered. This creates righting moment, or stability.

When the chine is immersed and as the boat heels further the center of buoyancy does not continue to move further outboard so the righting moment does not continue to increase. Nor, HOWEVER, does it go away. Because the center of buoyancy and center of gravity are both low in the hull the leverage, the righting moment, changes little. Stability does not suddenly disappear and heeling does not suddenly increase. Only when the heeling has become extreme due to the force of wind on the boat's sails does the center of gravity begin to align vertically more closely with the center of buoyancy, and stability is lost.

[wingssail]

Originally Posted by yesthatsue

A fiberglass hull with a hard chine costs exactly the same to build as one without one. Possibly a bit more if the point of the chine is to carry more beam lower, increasing the boat's volume and the hull's surface area.

Hard chines in plywood, aluminum, and steel are cheaper and easier for amateur builders to build one-off, but production boats and their associated tooling are a whole different thing.

"Possibly a bit more if the point of the chine is to carry more beam lower, increasing the boat's volume and the hull's surface area.

This is a very minimal effect. If you look at the transoms of a Oceanis 50's before and after the addition of chines you see a very small difference in cross section area; they haven't added much volume or surface. The chine is more of a little crease along the hull rather than a true change in the overall shape.

[Erik de Jong]

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?

Depends on the type of boat and the location of the chine. Ultra lightweight racers benefit from the hard chine in the aft 3rd of the hull with a wide waterline, displacement cruisers will be slowed down by it and will make more hours on the engine while burning more fuel to reach the same speed as well.
For stability it makes no real difference, you would not be able to tell from a righting-arms curve if a boat has a chine or not.

Fast racing boats surely benefit from the chine+wide butt which means that there is an image around them that makes it look fast, while for many boats it will actually slow them down. The wide and rectangular transom does add a lot of space, which is something that is always useful on a cruising boat. But the fact that you see these kind of chines on cruisers is pure fashion.

[Matt Johnson]

Originally Posted by wingssail

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.

100% agree! It's a shame this dogma about beam carried aft and chines persists.

Matt

[B23iL23]

here's an example of what chines can do. May not look like much but it does make a difference. These are aft chines - you can also add them up forward which greatly improve volume in the fore-cabin.

Originally Posted by wingssail

"Possibly a bit more if the point of the chine is to carry more beam lower, increasing the boat's volume and the hull's surface area.

This is a very minimal effect. If you look at the transoms of a Oceanis 50's before and after the addition of chines you see a very small difference in cross section area; they haven't added much volume or surface. The chine is more of a little crease along the hull rather than a true change in the overall shape.

[Bill O]

Originally Posted by wingssail

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.

I hear what you are saying, but on an offshore test sail/delivery in a very recent Frers designed hull (with the flatter aft section), we didn't like it.

We were doing a 1k nm offshore test run on a boat that was on our short list. The boat was very fast, but slammed heavily causing the boat to shutter. Even the owner remarked to the helm crew to try to reduce the slamming while he attempted to sleep below.

There were lots of other things that didn't cut it for us, so needless to say that boat is off our short list. If fact, after that test sail we decided to stay w/our old school rounded hull design, since it doesn't slam and can run deeper than the Frers hull. Will say it is slower (~10' less lwl), but then again it isn't the slowest either.

In this case, it's personal preference. I will cut down a little on speed to get a more comfortable ride.

[Manateeman]

To begin a post with “total nonsense”, then to quote me. WOW. It’s interesting when you go to the “about me “ there is nothing there about you. Notice I never quote posters. Kinda rude.
So I will restate. Hard chine is nothing new. In some designs, it costs less to produce. Like all hull designs, it has positives and negatives. Marketing stresses the positives. Lastly, a number of statements posted here use the wrong terminology or talk about some Principles without proper context. All I can suggest is ...again, Find a copy of Principles of Yacht Design by Larsson. Study the history of American Fishing Craft, talk to any Naval Architect and go build a few boats. You will learn that there is no perfect design, nor method of construction. Buying a boat, sailing it, that’s nice. But..you are looking at the world through a peephole.
Nothing new : The Chesapeake working oyster hull did not fall out of the sky.
The design is a response to the needs of fishing in that bay and...the cost of construction...and the strength, longevity, and availability of materials.
Look at the hull of a Lightning. Materials and cost of construction played as much a part of the design process as it did a hundred years before.
Stability curves, acceleration, prismatics, hydrostatics. Some of the post are wrong, incomplete, wrongly applied or understood. Professional boatbuilders do more listening to alternative ideas, they welcome new ideas and incorporate them or recycle aspects of older designs because there’s not a lot of new in boatbuilding. Hard chine or chines...pretty old stuff.
Here is an example : I like the French multi chine aluminum sailboats. Did I build one? No. I wanted curved panels. No to the centerboard. I knew it would cost a huge amount for twin keels but I liked all the advantages. I know, like and respect the French and Dutch builders. I also know they’d go bankrupt building custom designs like my boat because of such a limited market.
When people claim expertise by making all encompassing statements I ask only that they state their credentials. What is your experience building or designing.
Have you built anything substantial with your own hands. Do you hold any professional credentials. Expertise is earned and it’s just good manners to respect someone’s accomplishments. But ... what the heck...
Happy trails to you.
Captain Mark and his fuzzy faced, bad breath, biscuit pooping manatees.

[Jimmyb57]

As the OP, many thanks to all who commented. As with everything, there's more than one answer, but all of your responses have been informative and appreciated. I just have to figure if the chines and twin helms/rudder on the Bene 38 are worth the extra $ over the 37. Thanks again to all.

[boatpoker]

Hard chine, higher initial stability, lower ultimate stability.
Roud chine, lower initial stability, higher ultimate stability.

Builders build what the markets want. The market wants every avalablle square millimetre of volume, hence hard chines.

[chrisr]

[QUOTE=wingssail;3226047]There is no rating benefit for adding chines to a race boat.

sorry...must disagree. my experience is that under IRC rating hard points (aka chines) can offer significant benefit

maybe your experience under different rule is different...

cheers,