Thanks

JIm

1 - 16 of 16 Posts

Thanks

JIm

Joined

·
4,698 Posts

There are a wide range of hull designs. Some are dramatically different. And for displacement boats, the hull includes the keel.

There are a wide range of hull designs. Some are dramatically different. And for displacement boats, the hull includes the keel.

Thanks Mike. What is a displacement hull, one with an integrated keel? Like a full keel?

Thanks.

Joined

·
22,368 Posts

Its' a hull design that pushes the water aside, rather than trying to ride up on top of water. They are fuel efficient, but limited in speed. These are typically found on sailboats, trawlers, cargo ship, tugboats and the like. Planing hulls are found on go fast powerboats.What is a displacement hull

Not sure if true, but possible an US Aircraft Carrier, but you will never see that in print. DennisIts' a hull design that pushes the water aside, rather than trying to ride up on top of water. They are fuel efficient, but limited in speed. These are typically found on sailboats, trawlers, cargo ship, tugboats and the like. Planing hulls are found on go fast powerboats.

Joined

·
9,270 Posts

In its original conception, and without the tools to actually analyze the dynamic forces at play, initially the theory would have been implemented by boats that were true double ended and with cylindrical hull sections.

That hull form turned out to produce a hull that statically appeared to be balanced, but in practice did not behave as a balanced hull form.

Over the next century there were a wide variety of theories about how to produce a balanced hull form. One by one, these have largely been discredited.

It's only with the ability of computer modeling of the impact of the dynamic and static forces and the changes in buoyancy distribution with heel angle, that a truly balanced hull form can be achieved.

That hull form could not be more different than the original concept. It turns out that the 'pizza slice' hull forms with comparatively flat sections, ironically remain balanced across the heel angles that most boats sail within.

And yes, the keel type has little to nothing to do with balance. As a broad generality, full keels tend to produce the highest weather helms because the true center of lateral resistance is closer to the leading edge of the keel than static calculation would suggest.

Jeff

Thanks very much Jeff. Can I assume that designs from the 60s to the 80s are a serendipitous mix of well balanced and not well balanced? I understand they are not pizza slices so not as balanced as a newer design, but wondering how this should affect choice of an older (less expensive) monohull, like a Pearson, Irwin, Island Packet, Passport, Hallberg-Rassey, Swan, Valiant etc. etc.

In its original conception, and without the tools to actually analyze the dynamic forces at play, initially the theory would have been implemented by boats that were true double ended and with cylindrical hull sections.

That hull form turned out to produce a hull that statically appeared to be balanced, but in practice did not behave as a balanced hull form.

Over the next century there were a wide variety of theories about how to produce a balanced hull form. One by one, these have largely been discredited.

It's only with the ability of computer modeling of the impact of the dynamic and static forces and the changes in buoyancy distribution with heel angle, that a truly balanced hull form can be achieved.

That hull form could not be more different than the original concept. It turns out that the 'pizza slice' hull forms with comparatively flat sections, ironically remain balanced across the heel angles that most boats sail within.

And yes, the keel type has little to nothing to do with balance. As a broad generality, full keels tend to produce the highest weather helms because the true center of lateral resistance is closer to the leading edge of the keel than static calculation would suggest.

Jeff

Thanks again.

Jim

Joined

·
4,698 Posts

Thanks Mike, yes, this is a great resource. Much better than watching endless Youtube videos, that kind of info doesn't occur in sailing videos.

Thanks.

Joined

·
3,566 Posts

Thank you Barquito. I have ordered it, along with Sailing Theory and Practice by Marchaj, C. A. which was also recommended.

Thanks.

Joined

·
9,270 Posts

Marchaj's book is a great resource for basic theory. I will note that it is somewhat out of date in that a lot has been learned in the nearly 60 years since it was written.Thank you Barquito. I have ordered it, along with Sailing Theory and Practice by Marchaj, C. A. which was also recommended.

Thanks.

Jeff

Thanks Jeff. It's the 1985 edition, not the 1964, so it's only 35 years out of date . His 1989 bookMarchaj's book is a great resource for basic theory. I will note that it is somewhat out of date in that a lot has been learned in the nearly 60 years since it was written.

Jeff

Surely it would be nice to have something that includes more modern hulls. There are several books on sailboat design on Amazon but it's hard to know which ones are worth the price. If you have suggestions please let me know.

Happy sailing...

Joined

·
9,270 Posts

One of the biggest issues with the post Fastnet research is that the boat designs were IOR hull and rigs. Since then, boat design has moved in a very different direction that actually addressed many of the issues that Marchaj's book rightly identifies.

Jeff

Thanks. What do you recommend I read to understand the different designs from the 60-90s hulls and newer hulls?

One of the biggest issues with the post Fastnet research is that the boat designs were IOR hull and rigs. Since then, boat design has moved in a very different direction that actually addressed many of the issues that Marchaj's book rightly identifies.

Jeff

Thanks again, much appreciated.

1 - 16 of 16 Posts

Join the discussion

SailNet Community

A forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Full Forum Listing
Recommended Communities

Join now to ask and comment!