Are we making any real design improvements??

[SailDesign]

bless your enthusiasm, Steve!)

I'm not sure whether the reply with a "ppppfffttttt...." or not, so I won't

The Open 60 example was really just a stab at a "modern" boat for comparison. Yes, they are usuallyfat little beasts, which gives them sail-carrying power at a cost. THe coat being that they are bitches to sail in a good sea, especially into it. "Noise" doesn't even begin to descibe the sound.
As far as the narrower boats being built and designed (or vice versa), I think they are going in the right direction. Dave Adams in True Blue showed that skinny(-er) is not a race-loser, even RTW. Certainly their behaviour in waves improves, and they are much more gentle on the skipper, resulting in higher personal efficiency (not to be discounted as a tactic in long races).
Steve

[Wardi]

Originally Posted by SeaDrive

PHRF stats can be helpful, but they don't tell you if you need 5 guys on the rail to go upwind, or if the boat is suitable for a weekend cruise.

You are correct, but we need to start somewhare and perhaps it is easy enough to categorise each type based on experience. Another point is that if Crew ballast is used, then presumably they can handle more sail area, which would be taken into account in their D-L-SA ratio.

Originally Posted by SeaDrive

Multihull development was very rapid from the time of Piver until it became more or less mature about 10 years ago.

A couple of weeks ago I had the privelege to sail a currrent top German Olympic Tornado cat..very impressive!!. They were originally designed in 1952.

They perform very well and as far as I know there is almost nothing that is as fast for their size. Have there been any real advances since 1952?

[yipster]

wake from one hull may interefere with the wake from another, causing cancellation and actually decreasing the wave-making resistance.

and

Very few cats depend on wave cancellation - in fact the interference is generally adverse.

than why do 2 (mono) hulls sailing paralel get atracted, i'm having trouble understanding that.
would think there is a pressure buildup or is that conserved energy giving a faster sucking flow like in bernoulli's equation?

[SailDesign]

Yipster, the simple explanation would be that the water has speeded up between the hulls (being "squished" through the gap) abnd thus there is a lower pressure there, so the hulls are sttracted. In cats, this is present as well, leading to extra drag as the hulls get closer. While the hulls cannot be physically moved together, it does add compression in the cross-beams, and the energy has to come from somewhere.
That particular problem made for a fun tank test exerfcise at college - complete with strain guages on the beams.

Steve

[SuperPiper]

Real development:

Whatever happened to the "Bubbler" attempts? Were there not some ocean yachts that bubbled air through the hull to do something to the boundary layer? Obviously this did not work or there would be more of them about.

The new Parlier catamaran has hulls shaped like airplane floats. This could be a new idea with applications.

What is the name for the technology that keeps the hull fully submerged? Are these boats capable of S/L greater than 1.34?

Three bow types: raked, spoon & plumb. Are these just 3 ways to redefine water-line length or does each have a hyro-dynamic advantage?

Wardi's own foiling developments are truly the next generation of sailing technology.

[Wardi]

Originally Posted by Jeff H

I think that I can supply LOA, LWL, Disp, and SA for these boats but it will take me a little while as I was writing these numbers on an old evelope as I was working on the prior post last night. PHRF is not a measurement rule like the CCA, IOR or IMS but handicapping rule based on past performance. In that regard it is a pretty good indicator of the boat's relative speed at a single moderate wind range.

I have found a nice resource of data at http://www.yralis.org/
under "Handicap Racing Information with Rating Froms" , "Base Ratings".

I now have data on over 2000 boats with their basic dimensions and actual performance rating. The results of initial comparisons is very surprising!!

Most of the boats covered by this data are standard yachts 20-60ft from a wide variety of manufacturers. Unfortunately there is not so much information on the very latest racing craft such as Open 60's, V60, V70, Maxis etc or one designs like Mumm36, Farr40, Sydney38 etc.

Does any anyone know where I can get data for these types of craft?
Ideally I am after: Displacement, LWL, Sail Area, Beam, Draft, Ballast, Age, rating and most importantly a measure of their actual speed, not just their IMS or IRC. In a spreadsheet would be ideal!!

[Jeff H]

A lot of the kind of information that you are looking for can be found in listings for these boats on www.yachtworld.com. Boats like the Open 60's and Volvo Boats will vary quite widely in terms of their dimesions actual as they are not a one design class. There are a lot of sources for PHRF ratings although the ratings for individual boats will vary considerably with region. Also IMS certificates are a pretty good predictor of boat speed. The IMS rule is VPP based as a such predicts better predictions than earlier measurement rules.

Some of the key factors in the improved speed of new boat designs are the location of the longitudinal center of buoyancy, buoyancy and weight distributions, cross sectional modeling, more efficient foils, heeled hull form modeling, a move to more efficient and controllable fractional rig sailplans coupled with masthead assymetrical chutes, and the fineness of the bow entry angles. These kinds of subtle factors do not show up on any table.

Respectfully,
Jeff

[SeaDrive]

Originally Posted by Wardi

A couple of weeks ago I had the privelege to sail a currrent top German Olympic Tornado cat..very impressive!!. They were originally designed in 1952. They perform very well and as far as I know there is almost nothing that is as fast for their size. Have there been any real advances since 1952?

I think there is little doubt that if you were to compare, say, an Iroquois from 25 years ago to a current boat of similar size and purpose, you find find the new boat to be better in every way. Speed, capacity, safety, etc. Probably even cheaper (inflation adjusted price).

Originally Posted by Wardi

A couple of weeks ago I had the privelege to sail a currrent top German Olympic Tornado cat..very impressive!!. They were originally designed in 1952.

They perform very well and as far as I know there is almost nothing that is as fast for their size. Have there been any real advances since 1952?

I had the chance to take a deep look on a Tornado wich was trying to reach Athens 2004 this spring, so a very up-to-date model; if you compare this boat with a "vintage" Tornado, you will see that is a whole different boat; sails are different both in material and in design/concept, rig is different, foils and rudders are deeply different, deck gear is absolutely more sophisticated, lighter e stronger; just the hull shape is quite the same, but in a easy-planing multihull like tornado mere hull shape is one the latest parameters you have to consider to evaluate global performances.

Crispilo

[yipster]

on transverse wave cancelation and their effect at various speeds on a variety of multi hull design there is a good read at http://www.cyberiad.net/library/pdf/tl98.pdf

[Stephen Ditmore]

Originally Posted by crispilo

in a easy-planing multihull like tornado mere hull shape is one the latest parameters you have to consider to evaluate global performances.

I would dispute that the Tornado planes often. I've seen it written that a boat is planing when more than half its displacement is being supported by dynamic force (as opposed to static pressure). This means a boat that is barely planing is only "displacing" half the volume of water (at any given instant) as when it is stationary. I consider the Tornado to be a displacement catamaran because it does not lift half or more of it's static displacement out of the water at speed.

[SuperPiper]

Originally Posted by SeaDrive

I think there is little doubt that if you were to compare, say, an Iroquois from 25 years ago to a current boat of similar size and purpose, you find find the new boat to be better in every way. Speed, capacity, safety, etc. Probably even cheaper (inflation adjusted price).

Perhaps the skipper of 1979 preferred the ride of a deep, pointy hull over the performance of a flat-bottomed, wide-transom sled. Shifts in personal preference may be mis-construed as "advancement".

[Jeff H]

First of all the 'Iroquois from 25 years ago' mentioned in the quote was a catamaran and so I am not sure what you point is about the sleds relative to an Iroguois.

As to the rest of your statement, I think most of us would prefer the motion comfort of the modern IMS type form derived boats over the ride of a 'flat-bottomed, wide-transom sled' by which I am guessing that you mean Open Class type boats. But most of us also would prefer the motion comfort of the modern IMS type form derived boats over the miserable rolling, pitching motion, crash into every wave ride of more traditional designs. You are right that in 1979 the canoe bodies were deeper, but they were also far less pointy. In those days you had a choice between traditional hull forms with comparatively blunt ends and IOR style hull forms with their center flats and thier pinched ends. Neither offered very comfortable motions.

Jeff

[Wardi]

The rating rules do tend to favour boats of a particular configuration or seek to handicap out any real advances in design in the interests of "fair" competition.

I would like your thoughts therefore on:
"What should be considered a suitable basis upon which we can evaluate fundamental performance improvements?"

It is quite clear that Speed/Length ratio is the norm used by most casual observers, but we all know that displacement and sail area contribute significantly. So shouldn't a proper comparison be based on all of these parameters?

Could we perhaps establish a simple measure as a reference, based on the fundamental data established by Taylor in his Resistance vs speed/length ratio for hulls of various D/L ratios?

What do you think?

re:'Could we perhaps establish a simple measure as a reference, based on the fundamental data established by Taylor in his Resistance vs speed/length ratio for hulls of various D/L ratios?'

.i dont really see it being very simple a process. we have pretty much already shown that all ims irc irm ior etc rules have lead to weird boats with a bias toward slow or ugly designs.

this leaves the boats we can compare with being only
...........boats designed within the same rule for a long period of time
..........or boats designed to no rule at all.

which brings us to development classes really. development dinghys is where real design improvements have come. consider ns14 of 30yrs ago or moth of 75yrs ago. these rules and classes have been around for long periods and clearly the improvements in speed with the same boats are huge.

no rule boats
unlimited boats probably fail some of the other criteia which have prevented us analysing different boats. they have become lighter, got bigger sails and narrower hulls almost exclusivley, so are not really grounds for comparing. right?
the only other type of un measured boats which have not changed in fundamental terms are cruisers.

only cruisers and development classes are designed without the weird rating rules or extreeme dimensions which have been shown to be the domain of unlimited and rule rated boats.

in terms of development in yachts as we have been refering too mostly, the only way to see is real development is in which boats win the ims irc or whatever races. these rated boats are not developed to be fast exclusivley but are designed to be faster than the rule thinks they are. thats the objective and as you will find in general the newer boats are winning in the rated classes too this indicates real improvement in design.

we are getting better at design simply because new designs keep winning races. thats the measure of how well they are designed, how well they perform their task and how well they meet their design objectives.

andrew stevenson