Long versus short overhangs

[sailingdog]

Valiente-

A 50-gallon tank should probably have some baffles in it, at least perpendicular to the long-axis of the tank to help prevent the free-surface effects that Jody is talking about. The number and position of the baffles really depends on the tank geometry though.

[sailaway21]

Trying to stay on topic here without getting off into free surface effect which is certainly a topic for another thread.

Val will likely negate any free surface effect by the increase to four tanks versus two. But the idea that a stiffer boat is inherently more desirable than a more tender boat is not necessarily vaild. The stiffer boat is only desirable to the extent that it allows for more efficient operation of the boats sails. All other craft spend a good amount of effort in avoiding a too stiff condition. Stiff vessels roll with a period that causes damage to the vessel, particularly at the vertical extremeties and are uninhabitable.

Fishing boats and ships have provisions for winging out tankage, thus raising the CG, for different loading conditions, particularly light ship conditions. Tankage so poisitioned increases the vessels moment of inertia and results in a better more comfortable ride. In fishing vessels it compensates for the catch stowed low in the hold.

[hellosailor]

I'm surprised that no one (especially you, jeff!) has yet commented that sailboat design, including hull and rigging design and all the other bits and pieces of the whole boat, is still AS MUCH AN ART AS A SCIENCE.

Considering that "real computer power" has only existed for the last 20-30 years, and that so much design was done before then, frankly I'm in awe of how some designers got some hulls just so sweet. And having read Marchaj and a batch of other texts (some of which simply hurt) along with the more interesting books, I'm surprised NA's don't run away screaming at the thought of having to run equations.

The boat is going to move in three dimensions (actually four once you count time) and about three axes (roll, pitch, yaw) and then you've got to figure the hydrodynamics of the hull, which change every time the submerged area changes as the boat heels/rises/pitches, the more pronounced airfoil efects on the keel, and another whole set of similar variables on the sails from the wind. Times multiple sail plans and trim combinations.

Good lord, doing all that with a set of drafting curves and "Well, I think this might work" and getting it right--borders on a black art. And when I say getting it right, I mean a boat that doesn't slam in a chop, holds her own rudder when trimmed on any point of sail, and doesn't for a minute make the crew think they are on a roller coaster. There are such things, but for every one of them there's a slower rougher boat that stalls out in a short chop or finds other ways to abuse her owners.

"Horses for courses" and all that other fine stuff, there are many boats that fill many needs very well, and let's face it, very few that are really "poor" for any use. The really sweet ones, the ones that take anything with aplomb and make you wonder why you've never been on them before--that's a bit harder to find. And I've even heard some Big Name Deisgners admit that on some designs, they simply got lucky, because the boat was sweeter than anything else they'd done,and they had no idea why. (But promptly scaled the same form for other sizes.<G>)

Jeff, is there any commercial software that even attempts to solve the multi-variable analysis that a complete hull and rig entail? I'd be afraid to even ask the price of it, because I suspect it would be one HUGE programming job requiring years of fine tuning. Which leaves real Good Design still in the realm of the black arts (OK, experience counts!<G>) and not just something anyone with a buck can crank out.

[Valiente]

Originally Posted by sailingdog

Valiente-

What the H*** were they thinking putting the tanks just under the deck?

No clue. I have spoken once with the boat's designer, but haven't reached him since by phone or e-mail, and that might be because he can't make any money from something he drew in 1982.

As for the tanks themselves, yes, I will arrange for them to be pumped fore or aft as trim requires. Having four tanks also helps out with the issue of containmination, plus I could collect rainwater into a dedicated tank for non-potable use, which would significantly spare my drinking water supply.

Fifty gallon tanks might not require internal baffling depending on their height, but I have to get the old tanks out first before I can go in with sheets of corrugated cardboard to see what will fit and what makes sense in that regard.

Anyway, didn't mean to derail the thread, but it does underline the idea that stability isn't all form.

[Valiente]

Sway said:
Val will likely negate any free surface effect by the increase to four tanks versus two. But the idea that a stiffer boat is inherently more desirable than a more tender boat is not necessarily vaild.

True, and generally, she's a bit "rolly" already, but my idea, in addition to getting the ton of water down low, is to convert an existing SS tank below the engine (formerly a holding tank, and now clean and empty) into a third diesel day tank, post filtering. This will give me 40% more fuel, plus considerable range on "non-suspect fuel" should water or really fouled fuel get into my main keel tanks (50 gal. x 2). I am thinking this will get all the weight where I want it and will solve some fuel management problems as well.


Fishing boats and ships have provisions for winging out tankage, thus raising the CG, for different loading conditions, particularly light ship conditions. Tankage so poisitioned increases the vessels moment of inertia and results in a better more comfortable ride. In fishing vessels it compensates for the catch stowed low in the hold.

My steel boat is vaguely trawler-like to begin with, but I don't anticipate adding radically to the weight even when fully provisioned. I will have 600 pounds of batteries, true, but they are practically AT the CG, and so shouldn't affect pitching much...wetted surface, maybe!

[seabreeze_97]

Funny how Jeff feels the CCA's aren't good for offshore work, but wasn't the CCA a major force in reviving (when CCA was the ruling body) and keeping the Newport to Bermuda race alive? How much further out must one go to be considered offshore?
Another little detail that appears to have been lost is that in the CCA's constitution, one of their goals is "to encourage the design and construction of suitable boats for offshore sailing." One of the CCA founding members wrote, "I am convinced that it is our duty to stimulate the production of fast, as well as comfortable, boats for long-distance work."
I guess all those post-CCA boats in Fastnet '79:
1. Weren't designed to fit into racing rules as has been stated in this thread about CCA boats.
2. Were more seaworthy than CCA designs. Some were so seaworthy, their crews were terrified into abandoning them. Hmm, wouldn't have anything to do with their motion in a seaway, now would it? Were changes made as a result of Fastnet '79, you bet. Is ocean racing the venue of multi-million dollar operations now (building specialized hulls) as opposed to past generations where at least some actual consumer yachts were used? You bet, which is why Ted Brewer has nothing to do with them, as he has stated. Their merits for high-speed sailing are considerable, but can any of you go out and buy one? Oh, and forget that racing crew (you know, like those nasty CCA boats had). Try single-handing it.
Keep waving the banner Jeff.

[Jeff_H]

There's a hornets nest of missinformation. CCA like many of the U.S. offshore cruising clubs encouraged the use of small boats offshore. Just like today, during the period of the CCA rule, the fleets that raced in offshore races were a mix of outrageously expensive custom race boats, and production racer cruisers. Class winners in the Bermuda Races routinely include production boats with boats as modest as Beneteau First 40.7's and various J-boats having won their classes.

The boats in the 1979 Fastnet disaster were early- IOR boats, boats that I think anyone who has studied the disaster would agree were boats that for a variety of reasons were a poor choice for offshore work due to deviations in good design practice, which, like the aberant design principles that resulted in CCA rule, were were chosen to beat a the then popular racing rule.

If you read Adlard Coles who was very familiar with the race rules that were in effect in this period, he marvels at how much more seaworthy, albeit less motion comfortable the IOR boats were as compared to the RORC and CCA boats that preceeded them.

But yacht design did not stop 30 years ago at the time of the 1979 Fastnet Disaster. The Fastnet Disaster lead to the reseach that lead to greatly improved understanding motion comfort and seaworthiness. Over the 30 years since, much of that research has flowed into the design of racing rules (IMS/IRC) that truely encourages and produces boats with greater seaworthiness and motion comfort. If you read Ted Brewer he checked out during the era of the IOR and states that he never made an effort to understand what was going on with the newer rules.

As I have said before, these days, just like in the CCA era, once again, there is a proliferation of new racing rules out there and many of these produce extremely fast boats, but they are not exactly exmplary designs, producing compromises that run counter to motion comfort, structural integrity, and seaworthiness for the sake of speed that beats some arbitrary racing rule. I am not a fan of the boats that have emerged out of these rules.

But the cruiser/racer designs that have emerged out of the IMS/IRC rules and the performance cruising oriented designs that have been designed incorporating the principles learned at the grand prix levels of the IMS/IRC and filtered down into normal production boats has produced boats that are extremely easy to handle across a wide range of wind conditions with exceptionally comfortable motion and excellent seaworthiness. You should try one of these newer designs in a blow.

As to single-handing the boats that derived from these newer rules. I own a very early IMS type design. I routinely single-hand it. She was single-handed from South Africa to Maryland in the early 1980's. I met a fellow who single-handed a 25 year old sistership of my boat from South Africa to the Carribean spending the first 10 days in 30-50 plus not winds and seas that he estimated exceeded 15 meters (mast height). He averated over 150 miles a day including passing through the duldrums and used less than 15 gals of diesel. I would sooner make that trip in my boat than almost any 10,500 lb boat from the CCA era.

So Seabreeze, stay locked in the past, and ignore the research, content with what you sail and that your love of CCA era boats even if that love flies in the face of the best designers of today, and designers of yesteryear like Olin Stephens. Wave your worn out banner and I'll wave mine, and I'll wave to you as I go by.

Cheers,
Jeff

[Hartley18]

Originally Posted by Jeff_H

....
As I have said before, these days, just like in the CCA era, once again, there is a proliferation of new racing rules out there and many of these produce extremely fast boats, but they are not exactly exmplary designs, producing compromises that run counter to motion comfort, structural integrity, and seaworthiness for the sake of speed that beats some arbitrary racing rule. I am not a fan of the boats that have emerged out of these rules.

But the cruiser/racer designs that have emerged out of the IMS/IRC rules and the performance cruising oriented designs that have been designed incorporating the principles learned at the grand prix levels of the IMS/IRC and filtered down into normal production boats has produced boats that are extremely easy to handle across a wide range of wind conditions with exceptionally comfortable motion and excellent seaworthiness. You should try one of these newer designs in a blow.

As to single-handing the boats that derived from these newer rules. I own a very early IMS type design. I routinely single-hand it. She was single-handed from South Africa to Maryland in the early 1980's. I met a fellow who single-handed a 25 year old sistership of my boat from South Africa to the Carribean spending the first 10 days in 30-50 plus not winds and seas that he estimated exceeded 15 meters (mast height). He averated over 150 miles a day including passing through the duldrums and used less than 15 gals of diesel. I would sooner make that trip in my boat than almost any 10,500 lb boat from the CCA era.
.....

Jeff, I've been following along with interest since starting out (still half-heartedly) on the long journey of finding alternative to the Hartley - a boat with "character" - something like CharlieCobras (long keel, cutaway forefoot) perhaps? Dunno, yet. It's early days.

You have stated your belief that many newer boats can handle a blow better than the older designs and I notice with interest that, according to your profile, you sail a Farr 11.6 (modern, fin keel).

Examples of Bruce Farr's designs can be seen in almost every marina in Australia (just look for names like FarrOut, FarrAway, FarrGone, etc, etc.) and he and Joe Adams were probably Australia's best-known yacht designers in the '70s and '80s. Some of their designs produced wonderful boats - yours, the Farr 6000, the Adams 20, Adams 10 - and some rubbish as well.

Would you care to list a half-dozen or so from different designers in the up-to-40' range that would meet your ideals of "motion comfort, structural integrity, and seaworthiness"??

I, for one, would really like to know... Thanks.

[Jeff_H]

A few that come quickly to mind might be the post 2000 Dehler 36 and 39, a boat like the J-44, the Rob Humphrey designed Elan 40, boats and boats like the X-40 and X 41. Certainly not a comprehensive list but it these are a few examples that might demonstrate the type of boats that I am referring to.

Jeff

[bestfriend]

Originally Posted by Jeff_H

A few that come quickly to mind might be the post 2000 Dehler 36 and 39, a boat like the J-44, the Rob Humphrey designed Elan 40, boats and boats like the X-40 and X 41. Certainly not a comprehensive list but it these are a few examples that might demonstrate the type of boats that I am referring to.

Jeff

This is a great thread, glad to see it come back every once in a while.

JeffH I am wondering what a timeline would look like for boat eras and maybe a few boats to show the design of each era. Do you have something, or can you whip up something like that? Just for S*#*ts and giggles, doesn't have to be exact or completely accurate, just a basic idea. I am also wondering what my boat would fall under. 1990 CS34. You can see it here at fogcitysailor[dot]com.
Thanks