Hard chine vs round

[NoTies]

Anybody got any opinions, experience, advice, condecension condemnation, horrible tales etc. about the relative diffences between hard chine and round bilge? Use will be liveaboard cruising, coastal and bluewater. I know there will be differences based on individual design but really want to find out if there's any fundamental problems, especially with hard chine.


Pete

[delmarrey]

Generally hard chines are on power boats.

Sail boats may have a bit of a chine if it's home built of steel or plywood.

Although, some of the new designs (sailboats) with the wide ass could be considered chines. But more of the soft chine. They do have twin rudders too.

Power boat are designed to plane on the water, except trawlers. A trawler is a displacement hull but usually has soft chines.

But sail boats are designed to cut though the water while at multipule angles.

[NoTies]

Thanks. I guess my terminology wasn't quite accurate. I was referring to the homebuilt type steel boats that have angular framing and plating. Does this type of construction have any inherent faults in terms of sailing characteristics?

[Talbot]

A lot of steel yachts are built with hard chine shape cause its so much easier to plate. As the designers doing this include Van de Stadt, I suspect its like any other boat - a good design works, and a bad one doesnt.

[Jeff H]

I worked on the design for a number of hardchine steel boats when I was worked with Charlie Whitholz and have sailed on quite a few as well. This is a question with no simple answer. In a general sense soft chine boats allow a boat to be shaped more optimally to produce a combination of greater stability, better tracking, motion comfort and performance. While soft chines may allow this to occur, that does not mean that every soft chine boat will be more stable, comfortable or sail better than every hardchine boat. There are poorly designed hard and soft chine boats.

In a general sense, multiple chines allow the designer the greater freedom to shape the hull in a manner that is closer to ideal than a single chine hull and radiused chines allow even more freedom to get things right. With comparatively narrower hull forms, conic sections can be used to further reduce the difference in hull form between an ideal design and what is easily achievable with a hard chine hull within the material's limitations.

When you talk about using steel as a building material for boats under 40-45 or so feet there are already inherrently big compromises in the stability, motion comfort and sailing ability that is inherrent in the material so the losses in these categories between a hard chine and a radiused chine tend to be less apparent and significant tnan with many other materials.

Properly constructing a soft chine steel hull can greatly add to the cost of building the hull. It takes greater skill and so is generally predominantly done on higher quality, professionally built boats. Often soft chine construction can be a clue to the general standard of care with which the boat was originally designed and constructed.

But because all of the above consists of very broad generalities, and since since steel boats, like boats built in most other materials vary so widely in the quality of design, and the quality of build, that there are bound to be many exceptions.

Jeff

[By Invitation]

Minor point here. When anchored in a harbor for the night with any wave action, a hard chine boat will tend to "slap" the waves. A soft chine boat will not. I was on board a hard chined boat for one evening, it drove me crazy. I'll take a soft chined boat any day for night time comfort alone.

[Talbot]

Your point about hard chine slapping is true for radical hardchines, which are normally more predominant on motorboats. The hard chine design for yachts tends to have a much softer angle change, thus less likely to slap.

In any case, this slap is less of a problem than that experienced in boats with sugar scoops.

[jim lee]

I forgot about the "slap". I was in a steel hard chined boat for about 2 hours helpin' swap out a starter. It was like being in a steel drum!

As for round hull sections making for a smoother ride. Like they said above, its not always the case. My machine has a pretty much round bottom. Very little wetted area, good for speed, but it rides like a corvette on a dirt road. It'll knock your teeth out in rough seas.

-jim

[Wynand N]

A hard or multi chined hull will have more initial traverse stability than a round bilge which is more tender.
A chined hull also tracks better that round bilge hull.

However, there is a middle way where you can have the best of both worlds. A raduis chined hull can fool many into believing it is a proper round bilge hull, if it is properly designed......

[Jeff H]

With all due respect, I think you are mistaken. A single chine hull will generally have more initial stability than a soft chine hull but typically far smaller angle of positive stability. A single chine hull is also more likely to trip over its chine and snap roll capsize.

Multichine hulls generally tend to have less initial stabilty than a soft chine hull, and typically similar limits of positive stability.

Typically, a chine hull will not track better than a soft chine hull as small changes in heel angle will alter the angle of attack of the chine. This results in chine steer, or chine walk, which can quickly alter the course of a hard chine hull. This is especially a problem with single chine hull.

Jeff

[BC Mike]

Sail a Lightning, a Thistle or a Flying Dutchman and you will quickly feel the effect that Jeff is referring to.
Use a hard chine boat if it is not ballasted and it is not a sail boat.
That way you will have a bit more stability. If that sounds like a small row boat, good.
If it has a keel for ballast I would always get a soft ( rounded )chine. But that is just my opinion based on my boating experiences.
Michael

[delmarrey]

I would agree with JeffH. A chined hull heeled over would be a bit like having a keel out of alignment. It would want to follow the contour of the seam.

Back in the good ole days while taking sailing lessons we had to sail a Sabot without a rudder and that was done by leaning into the chines and shifting weight for and aft................_/)

[NoTies]

I guess now that I think about it I didn't really need to ask this question. A few years ago I was questioning figures from a naval architect about lifting stability on a hard chine 40' work boat. He showed me the computer modelling and it was very similar to the cat scenario. Much greater stability than equivalent round bilge boat up to a point then WHAM, over she goes.

[delmarrey]

Well, the nice thing about the round bilge with a keel, it's like a pendulum and it's EZ to lower the COG (center of gravity). Unlike a hard chine where most of the weight is spread over a wider area, in effect, raising the COG when it heels over. No pivot point.

I've always wondered how a boat would handle without any chines. Basically a water wing. The draft would probably be more then normal and it would probably take more sail area to get it to move along. Much like a heavy full keeled boat.

But it wouldn't roll over. Unless it were hit with a super steep breaking wave. Then nothing would survive that..............._/)

[BC Mike]

" Then WHAM, over she goes ".
That is the effect you get sailing something like a Lightning.
Good stability to a point, and this is separate to the steering effect of the chine.
Others might say they like the buoyancy effect of the chine and never sail with that much tippy anyway.
Some boats have minimul length chines ( they do not go as far foreward or aft ) so I would assume they behave somewhere in the middle.
If we have the technology to make them round, I would do it.
I do not think there are any hard chined fish.
Michael