Sailing Dinghy Design

[Paul B]

I guess you know best

If you look at the designs that have dominated the I14 class since the merger with the Aus 14 skiffs you will see the trend in shape. No successful boat in the past 25 years or more has ever had the deadrise you show.

Look at the photos of the Worlds this year (http://homepage.mac.com/sailpics/PhotoAlbum9.html). The top boats (Bs and Morrisons) have the slab sided skiff shape. If you look at all the latest successful designs for the past 15 years you see the evolution toward this shape. The path you are following is a dead end.

You owe it to yourself to re-read the rule, look at what is successful in the class, and why, find out where the best boats have weaknesses, and try to exploit that through an evolutionary solution.

Does your design take into account the rudder mounted lifting foil used by the top I14s?


You would think that a "professional" designer posting to this thread would have noted these issues and addressed them, instead of attempting a weak snipe at someone who is being truthful to the young designers working on this project.

But hey, I do believe that I14s plane upwind.

 

[Phil S]

Tim, I agree with all the criticism of your design. You need it flat on the keel and wider in the stern. This century you do not need flared topsides. They went out with adoption of wet suits and wings/racks, the first keep us warm when wet and the second gets us outboard (further if allowed) with less weight. The narrower vertical topsides go through waves easier.

Response to Mad re moths in 20-25kts. Unless you are pretty heavy a moth is fully powered up in more than about 10 kts upwind and 12 reaching.

I do not pretend to be an expert but I managed only one swim in two races last weekend. In 20-25: Upwind the top half of the sail is flagged out, Tight reaching the same. Deep reaching and running, less cuningham but more twist than expected especially in waves, to depower the top of the sail to keep the bow up. Deep reaching you sit on the back corner of the wing, with only enough sheet on to keep the bow up, backing off a bit as you go over the top of each wave and head for the trough.

When you get to the the leeward mark you thank your favourite deity, and enjoy the next work. The good rides stay in the memory a long while.

This is why I believe a longer boat of the same configuration would be significantly faster. It would not have the same nose dive speed limitations.

Everyone knows narrow is faster, its just last century's rule makers who are ruining the fun.

 

[SailDesign]

Paul,
"You would think that a "professional" designer posting to this thread would have noted these issues and addressed them, instead of attempting a weak snipe at someone who is being truthful to the young designers working on this project."

Yes, you would. However, I am here not as a "Professional" designer trying to show how much I know, but as someone that occasionally can help the "young designers" out. I try to adopt a "hands-off" approach to this stuff. We all have to learn, and having some egotistical 48-year old geezer (that's me, BTW) saying "don't do it that way" is all very well if he's paying you, but not OK if he's just a spectator.
My "pissed in your cereal" comment was intended to convey a modicum of humour, coupled with a desire for you to realize that the sort of criticism you were doling out (basically "Rip it up and start over") was a bit out of place here. Tim is having fun with this boat, and while it may not look right to you, there are more tactful ways of saying it.
Looking at the best boats from the current batch may have it's advantages, but frequently the major advances are made by NOT looking at the current crop, but by taking a flyer. It's a gamble, sure, but the Kiiws would never have got the Cup like that. ;-)

Anyhoo, I'll shut up now, and I promise not to mix dubious humour with serious comments again. ;-P

Steve

 

[SailDesign]

That's "KIWIS", dangit!

 

[Andy]

Tim - Id have to agree with all the points of criticism too im afraid. I think that with a tight rule like the 14's have there is comparatively little development available other than minor tweaking to suit advances in other areas of the design, or perhaps to refine the existing package. This is exactly what drove Paul Bieker to design the B4 in light of recent foil developments. This will have a subtle effect on the rig too (the B4 rig is further aft than before the B4, if you catch my drift...). Im pretty sure someone mentioned this before in the thread.

Its easy to be seduced by a personal idea and to stop making rational design comparisons and decisions - it wasnt so long ago that the usually brilliant Britt Chance designed a 12 metre with a cut off waterline which was anything but fast. Some of you will know the story concerning Ted Turners opinion on this boat that 'even a turd is tapered'(!!)

The shape you have designed is not necessarily inherently bad, it just defies the theory about what makes a fast racing International 14 hull. Any hydrodynamicist would be able to tell you that this theory is, barring some very small percentage variations, fact. So your hull is probably not going to beat the other 14s. But credit where its due - this hull would be much more forgiving to sail than a modern 14 hull, and in many applications this is a desirable design trait (it almost looks Lark like in section, no?).

My tuppence of advice would be to start with the rule, not a wild idea, assess the current state of the art, see if any ideas jump out at you and then let scientific and empirical reasoning be their judge. There are certainly plenty of books and web sources to keep any free thinker honest. Rule 'ideas' such as the wing keel in 12 metres demonstrated obvious benefits from the outset which clearly outweighed any disadvantages before anyone tried it. Outside of restrictive rules, free thinking has more of a place, but you can be sure that whichever ideas succeed (eg CBTF) were of sound technical basis in the first instance. The 'hula' was marginal - look what happened there. If radical hull forms are your interest then you might want to look more into the air lubricated and vortex inducing hulls of Viking longboats, as an example, and design a modern boat based on these principles. There are other hull form ideas around which merit a further look too. But you would never get a hull like this to measure as a 14.

All this said, its an interesting world out there so - KEEP DESIGNING!!

Andy

 

[Tim B]

Thanks guys,

To be honest I'm still playing with the hull-shape, but part of the question is that I like boats that handle nicely and sail fast, its a difficult comprimise anyway, but I've pulled the bow finer, flattened the stern, and I'm moving the aft end of the semi-sheer out, just to increase the ease of planing (and I think I've overcooked it slightly).
You have to admit that it's progressed a hell of a way from version 1, posted in the 2nd page, and considering that that was posted in May, perhaps there's an indication of the rate of change. Admitidly the hull-form is similar, but the construction method is completely different. V5 has come from taking a keel-line that has max draft amidships, at the section rule. Then creating an intended waterline, semi-shear (just below the wings) and sheerline, then fitting stations between them. It produces a nicer hull geometrically I've found. Remember also, that the posts are possibly not as current as they might be.

Andy, about the similarity to the lark sections. I sail a Lark, and I'm very happy with it, The main concerns are weight and lack of trapeze, not really the sectional properties, so whilst they may be the tiniest bit Larkesque, they're certainly not that close.

Thanks everyone for your support and input,

Cheers,

Tim B.

 

[Paul B]

Kiwis?

"My "pissed in your cereal" comment was intended to convey a modicum of humour, coupled with a desire for you to realize that the sort of criticism you were doling out (basically "Rip it up and start over") was a bit out of place here. Tim is having fun with this boat, and while it may not look right to you, there are more tactful ways of saying it."

No Steve, your comment was directed at me because I disagreed with a fanciful claim made in an earlier discussion. Phil's comments about the lines looking like a 1954 design preceeded my post, yet drew no comment from you. I never saw any comment from you, tactful or otherwise, attempting to steer the project in a better direction.

Tim asked for comments in his post. Seems maybe he did not want comments, he wanted agreement. And I was being tactful, but after Tim's attempted condescending "cutting" remark maybe I should not be. If you actually built a boat anything like the sketches shown and showed up at a major I14 regatta you would be laughed out of the dinghy park.

The first step in any design or engineering project is to define the problem. In this instance that would have included reading the rule and examining the successful solutions to date. I don't think either was done. That may sound harsh, but to continue down a wrong path is nothing but a waste of time. You need to understand the fundamentals and trade offs before making a decision based soley on BWL.

I included a link so all could see what the latest successful shapes look like. The shape I pointed to was rejected out of hand because it did not agree with the "blinders on" view. I think Tim and the rest should do some research into why the boats have evolved this way before forging ahead with a design direction that will not be competitive.



"Looking at the best boats from the current batch may have it's advantages, but frequently the major advances are made by NOT looking at the current crop, but by taking a flyer. It's a gamble, sure, but the Kiiws would never have got the Cup like that. ;-)"

KIWIS? Do you mean Aussies? It was the Australians who won the cup with a flyer of an idea (winged keel). When the Kiwis won the cup they did so by hiring the designer from the previous winner (Doug Peterson), and the 1995 winning Kiwi shape was an evolution of the 1992 America Cubed shape.

 

[Another Guest]

Hey Paul B

What design of 14 is that in the rendering you posted? Are you "A" Paul B, or "the" Paul B moved further south?

Sorry Tim, I have to agree with the comments about the 14 design. I'm no expert, but I've been lucky enough to talk/correspond a bit with most of the best 14 designers. I have spent a bit of time looking at 505 lines and I think your hull is actually more veed than the 505 or the prototype, the Coronet; in fact it looks like the Farrar I-14 "Thunderbolt", which was an influential failure in about 1952.

Check out the sections on Phil Morrison's Mk 8 (on the Rowsell & Morrison site) much flatter than yours and yet Phil's boats are renowned for being nice to handle.

The flares do NOT necessarily make the boat easier to handle - Dave Alexander (top rig designer, about 5th last I 14 worlds) and Grant Geddes ('98 ? world champ) say that the water rising up the topsides and striking the flare at the stern creates a lifting force at the transom, driving the bow down and into a nosedive.

Also racks can be pitched higher than flares, which stops the lee side dragging in the water and keeps them above waves. The Aussie B4 has 20 mm more topsides than the normal B4 'cause it's sailed in big waves, adn theextra freeboard pitches the racks higher against. Grant reckons it's a much more comfortable and drier ride than the Ice, which had flares like your boat.

The flares at the bow increase drag dramatically when the bow goes in, stopping the boat, increasing apparent wind and destroying any chance of a recovery. Look at multis, they have rounded, low-drag deck and gunahwales so you can drive deep without further drag. A boat like an A or Taipan can drive underwater all the way back to the mast and still reco ver, because it slows but does not stop and trip.

The vee shape increases wetted surface for a given volume, compared to an ellipse.

Also note that all of the top skiff designers (perhaps Phil Morrison is now an exception but he has huge experience) are active skiff sailors; as a professional naval architect who designed a couple of moderately succesful 18s told me recently, hands-on expedrience is vital in these classes and non-skiffies can't compete.

re the Lark; check the sections of the Lark (Mike Jackson design about '62 from memory) with his later N12 designs; Jackson was perhaps the first designer to have an almost (or truly) flat panel along the keel line. If the Lark designer moved towards a flat panel in his later boats, surely that's a perfect demonstration that the Lark's deep Vee it isn't the fastest/best shape.

Re under-hung rudders. I use one on my International Canoe and love it, because the foil is so small and well balanced that the helm is the best you'll find in any boat, anywhere AFAIK. But Rob Brown tried one on an 18 and it was a disaster downwind, because it was "like power steering"; ie over-sensitive because it was so close to the centreboard. Also some top ICs now have transom-hung rudders although water-flow off an IC stern is not like a normal transom.

Also, having no chine and a very soft bilge means that water will "wrap" all around the hull at planing speeds, dramatically inxcreasing wetted surface. The only chineless skiffs are the Howlett Boss etc and the Vanguard Vector, all of which have evoked controversy regarding their performance. Many skiff designes say you must hae a chine aft to act as a water release; even those I have interviewed who like round bilges, still put a chine in the last few feet for directional stabiliy and water release at speed.


Sorry to be so negative, I'm not saying I could design a boat but I'm just passing on what I have been told.

 

[Paul B]

Not a real I14 design

The jpeg I posted is not really an I14. I took a couple of hours one day and eyeballed some sections to show what the slab side look should be. I think my model is really too wide, the bow isn't right, and I'm sure the rise of floor isn't right. I did this quick study without one dimension, so who knows what it would really be. Someday I might find time to really look at it.

NO, I am certainly NOT "THE" Paul B. I hope I have not given anyone this idea.

Actually there is a linesplan of the Morrison 10 on one of the links from the I14 site, can't recall which one at the moment. It is very much more slab sided than the 8. I believe the 11 is even more so. (edit: here is the link to the 10 linesplan: http://www.rmwmarine.com/14design.htm).

I have a cool book done in the 80s about the history of theI14 class. It contains plates of a lot of linesplans up through the years, includeing stuff from Fox, Kirby, Cross, Benedict, Morrison. This was all pre-Bieker. I once owned USA #197, a post war Fox design in molded plywood, and it was flatter than the sketch shown here.

 

[SailDesign]

Paul B,
Since you turned off the email option, I'll have to reply in public.

"No Steve, your comment was directed at me because I disagreed with a fanciful claim made in an earlier discussion. "

I had forgotten about that, life is too frikkin short. if you want to believe I made a comment based on pettiness from a few weeks ago, I can't stop you.

"Phil's comments about the lines looking like a 1954 design preceeded my post, yet drew no comment from you. I never saw any comment from you, tactful or otherwise, attempting to steer the project in a better direction."

That's because I didn't make any comments ;-) See my previous post for reasons. I am not here to "Steer the project", I am here because I enjoy deisgning boats, and I enjoy talking with others who feel the same. If you want criticism, you'll have to pay....

"If you actually built a boat anything like the sketches shown and showed up at a major I14 regatta you would be laughed out of the dinghy park. "

PLEASE see my "pissed in your cereal" and "tactful" remarks. Please!

"The shape I pointed to was rejected out of hand because it did not agree with the "blinders on" view. "

It hasn't been rejected yet - it has only been posted for 12 hours or so. Patience, Grasshopper.

"KIWIS? Do you mean Aussies? "

Does the name "Michael Fay" mean anything to you? Can you think of a bigger flyer in Cup history?

Steve

 

[SailDesign]

Paul,
This is intended in exactly the spirit it seems:-

Take a free shot, by all means, but "yes" I did "forget" that the Kiwis didn't take the Cup that time.

It was a heck of a flyer, though....

Sometimes I wish I had Alzheimer's, it would make it easier to explain a bad memory......

Steve

 

[Guest]

Nonsense

I haven't purposely turned anything off. If the e-mail option is off then it is the default or maybe when I signed up here I toggled it. Regardless, I do get messages in my User CP. Got one today. So if you really wanted to do this off topic you could have.

I don't think any individual should steer the discussion. But as the senior professional designer in this discussion maybe it would have been good for you to do a bit of mentoring when things started to go astray. The fact that someone else did seems to have hit a nerve with you.

You claim you didn't make "any comments", but you did make a comment to me. You lack a bit of logic there. If you didn't feel the need to comment to Phil you shouldn't have felt the need to comment to me. Do us a favor and don't comment on anything I post, unless your comment is design related.

The Bieker shape I pointed to was clearly dismissed by Tim, due to the superior narrowness of his BWL. The fact you don't recognize that goes directly to your need to quibble with me about anything you can. That is clearly the result of the Planing Open 60 discussion, whether you admit it or not.

Your quote: "It's a gamble, sure, but the Kiiws would never have got the Cup like that. ;-)" Michael Fay never "got the cup". The Kiwis "got the cup" in '95 by hiring in the lead designer and the CFD expert from the '92 winner, and worked up an evolutionary design.

Now if you have finished perhaps the discussion can get back to the merits of the I14 design.

 

[Paul B]

The above message is mine Paul B

I don't know why it shows as Guest. I am shown as logged in.

I believe this the 2003 World Campion Morrison 11.

 

[SailDesign]

Paul says: "But as the senior professional designer in this discussion maybe it would have been good for you to do a bit of mentoring when things started to go astray."

Why? Part of the fun of drawing boats, and not as a "professional", is trying new and diferent things. Actually, that is part of doing it "professionally" as well, come to think of it.
As I have said before, my presence here is not to "steer" or otherwise mess with other folks' fun. I don't comment on their designs from an aesthetic point of view, or a technical one unless there is a safety issue or something like that. If they like what they are drawing, then fine.

If they were paying me to teach them design, then I might have more to say, but this is for fun. Maybe you forgot that.

"You claim you didn't make "any comments", but you did make a comment to me."
Only to ask who p*ssed in your cereal. Not boat or design-related in any way, shape or form, and certainly no comment on the link you sent.

"Michael Fay never "got the cup". "
I believe I covered that, but I did offer you a free shot - consider it taken.

"None of the sketches I've seen in this thread look anything like a modern I14, or any skiff."
Well, gee - thanks!

"Do us a favor and don't comment on anything I post, unless your comment is design related."
??

Steve

 

[Paul B]

Nice I14 shots

I don't read Japanese, but here is a link with good shots of the more modern shapes, complete with foil rudders and gantrys. The rudders are moving back as opposed to the idea of putting one under the boat.

http://www.i14.jp/t-foil.html