Understanding the Ratios

[Bash]

Originally Posted by Ishmael

I guess I always assumed the numbers would allow one to compare and contrast different/disparate designs on a purely objective basis.

I just reread the original post. I'm not seeing a request for purely objective criteria there. Rather, I'm seeing someone who subscribes to the tired old polarity of "bluewater" boats versus "coastal cruisers."

The boats being asked about in the original post were designed in the 1960s. One of them was available in a yawl version. Sheesh. Is there a real question there?

Yes, back then stability was mostly about ballast. Designers didn't know any better. Nowdays, now that computers are available to aid the design process, designers begin with other ratios, such as the sail area/displacement ratio. You want to compare the triton with the vanguard? Begin there.

Sailboat design has evolved tremendously since the days of the Pearson Triton. It was a great boat for its time, but that was 40 years ago, back in the days when telephones had dials you actually spun around.

[Target9000]

Originally Posted by Ishmael

I apologize for seeking clarity on a boating issue from knowledgeable boaters on a boating forum - how rude of me. Of course, you could simply ignore a thread that so clearly disinterests you, but that would deprive you of an opportunity to sneer condescendingly at us "wannabes".

To everyone else, thanks for the constructive responses. I guess I always assumed the numbers would allow one to compare and contrast different/disparate designs on a purely objective basis. Clearly, there is still a huge subjective component required in interpreting the data.

Cry me a river.

[barnakiel]

Originally Posted by Don Lucas

flat bottomed sailboats and now I need to be looking out for a sailing pig?
or
does this mean if my boat is seaworthy that I'm a pig?

I thought sailing was going to be fun, not this mental.

Don't blame barnakiel, he has a sailing pig!

Blame Marchaj!

Cheers,
b.

[Seahunter]

Some designer/architects stretch the ratios to fit their own designs and are mostly arbitrary. You can take two identical boats and they calculate differently based on added equipment or modifications. If you know your boats' true weight-length-WL-Beam you can calculate (to within reason) each boats' performance characteristics.
Here's a site that gives you the formula.
Sailboat Design and Stability

[Adelie]

Originally Posted by sabray

So far haven't seen pigs out sailing. I saw a goat once that was doing a RTW solo stint. You might try sailing a corsair f27 if you want fast and seaworthy just understand the compromise.

Are you sure it was a goat and not David-Old-Jersey?

[barnakiel]

Originally Posted by Seahunter

Some designer/architects stretch the ratios to fit their own designs and are mostly arbitrary.(...)

Well, yes, this can be done. But it is very easy to find out.

In fact, however, I think that on the whole the ratios calculated today are far more accurate than those calculated say 20 years ago. The help from computers is huge when it comes to establishing the actual parameters of the boats.

So as the newer boats may be burdened with some manufacturer's stretching things, the older ones are burdened with inaccuracies in estimations of their actual parameters.

b.

[Seahunter]

Originally Posted by barnakiel

In fact, however, I think that on the whole the ratios calculated today are far more accurate than those calculated say 20 years ago. The help from computers is huge when it comes to establishing the actual parameters of the boats.

That's why I added the link. You can use your computer and "click" on it.

[s/v Beth]

Well I definity stepped in it on this thread. I had not really been paying attention to these types of threads or I would have never have posted. Please sail the oceans in whatever floats your boat. Life is too short to deal with should I get this as opposed to that.
And please insert "high performance surfing hull" where I said "flat bottom".
Now if you don't mind, I will carefully clean the stuff from off my shoes and walk away, my little pig in tow.
At least she's potty trained.

[Ishmael]

Originally Posted by Bash

I just reread the original post. I'm not seeing a request for purely objective criteria there. Rather, I'm seeing someone who subscribes to the tired old polarity of "bluewater" boats versus "coastal cruisers."

The boats being asked about in the original post were designed in the 1960s. One of them was available in a yawl version. Sheesh. Is there a real question there?

Yes, back then stability was mostly about ballast. Designers didn't know any better. Nowdays, now that computers are available to aid the design process, designers begin with other ratios, such as the sail area/displacement ratio. You want to compare the triton with the vanguard? Begin there.


Sailboat design has evolved tremendously since the days of the Pearson Triton. It was a great boat for its time, but that was 40 years ago, back in the days when telephones had dials you actually spun around.

I guess I'm confused by your tone in this post. I wasn't looking for purely objective criteria. I was confused as to how past statements I've read here about certain boats and general perceptions didn't always seem in line with "the numbers (which I thought were supposed to be more objective than they apparently are). I had just recently read a thread in which people were talking about the Triton - mostly glowing testimonials about its capabilities etc.. And I remembered another thread where the consensus seemed to be that the Vanguard is suitable only for coastal cruising. Having never tried to analyze boats based on "the numbers" (using the different ratios), I did a few calculations and noticed those two boats were pretty close on everything - they both seemed to fall into the same ranges right across the board. I was just wondering how the perceptions of the two boats could be so different. Didn't mean to cause anyone such heartache and angst.

I went to a web site that listed a few of the ratios, and I tried them - that's all. There were little summaries that said an "offshore" boat should fall in this range, racer/cruiser in this range etc etc.. You say that's "tired old thinking" - fine. That's why I asked the question - it wasn't making much sense to me. Thanks for the explanations you provided in your last response - I just don't understand why they need to be delivered with such disdain.

[Ishmael]

Originally Posted by Target9000

Cry me a river.

Scintillating

[mitiempo]

I don't think an offshore boat can be chosen strictly by the numbers, if at all. Many refer to D/L ratio as a measure of weight carrying ability for example. A larger boat with a smaller D/L ratio can carry the load a couple cruising may need as well or better than a smaller boat with a larger D/L ratio.

I think the so called "offshore" design with its long keel, attached rudder, and D/L ratio over 300 went away a few decades ago - the Valiant 40 for example. Considered reasonably extreme in the 70's when she was designed but heavy compared to many newer designs. Fin keel and rudder on a skeg. Still a great boat to cruise in though. Or the Peterson 44/46.

Although larger, the Sundeer 60 has a D/L of about 82 and was designed as a couple cruiser. Many have circumnavigated and more have crossed oceans successfully. The Saga 43 is a great offshore cruiser with a D/L of 160 as is the Saga 35 with a D/L of 151. These all have spade rudders, thought to be too dangerous to take outside of the bay 40 years ago.

Times have changed and the boats have as well. A good offshore boat has to be well built but doesn't have to be a heavy, narrow full keeler with attached rudder and long overhangs any more.

[mitiempo]

As far as Ishmael's dislike of the tone, this is pretty mild.

He should ask the same questions at Sailing Anarchy.

[sailorboy1]

Originally Posted by Ishmael

I guess I'm confused by your tone in this post. .

I think you just read it as a hash thing when it probably wasn't (I didn't read it as hash). Lots of the posts were about the ratios being old and not all that important to more modern design.

When it comes to it if you are looking at an older design from the "ratio days" you would get better info by chasing down an owner of a given model and getting the real story.

[barnakiel]

Originally Posted by mitiempo

(...) Times have changed and the boats have as well. A good offshore boat has to be well built but doesn't have to be a heavy, narrow full keeler with attached rudder and long overhangs any more.

Gotcha!

You completely obliterated the human factor.

For gods' sake PLS read some on the Dashews' background then tell others which boat is good for offshore work.

Off course, an IMOCA is an excellent offshore boat. For Vincent Riou. Please note not all of us are anything like Vincent!

To other sailors, a boat that will accept less than celestial sailing skills is perhaps a better choice.

BTW Long overhangs were never, to my understanding, confirmed to add to seaworthiness of a boat.

Cheers,
b.

[mitiempo]

I don't recall suggesting an Open 60 is a good offshore boat.

But a Sundeer 60 is hardly a skittish racer. It is a well balanced couple oriented boat with a relatively small easily handled rig. It is actually very conservative in design. Sail area/displacement is 17.61. As a matter of fact the Van de Stadt Samoa 47 has more sail area than a Sundeer 60 - 1277 vs 1240 for the Sundeer.
The D/L ratio of the Sundeer is 82 but if it had a waterline of 47' instead of 60' its D/L ratio would double. This really shows the problem with D/L ratios - if the Sundeer had the 47' waterline it would be lighter even though its D/L would double.

The Dashew's sailing background is irrelevant as far as the handling of a Sundeer, which is a production boat that was marketed as a offshore couple cruiser. Many have sailed across oceans and a few around the world - with couples, many of them older.

From Dashew Offshore - hardly an Open 60: