Sailing Dinghy Design

[dishsail]

Thanks, Tim B.

I don't know where to start through. I really don't have any ideas as of right now. I would like to get starting on drawing but don't know where to start. Shortly I am starting private lessons for hand drafting architecture building. Please let me know if you have any suggestions.

Thanks.
Joseph

[Tim B]

Below I have attached a ZIP file containing some step-by-step instructions and multiple figures. I hope this is of some use. I would strongly reccomend looking at dinghy sailing books, websites and Principles of Yacht Design by Lars Larson.

Good Luck,

Tim B.

[Tim B]

Well, almost. I've left the deck off this rendered image ('cos I haven't designed it yet). I've attached it to this reply because my network system won't let me post to the gallery. Anyway, let me know what you think. Incidentally, the crew are to scale, but they are really only illustrutive, and all I had at the time (download from http://www.3dcafe.com). Tell me if you like it, or if I've been wasting my time. The wing had to come forward from the origenal sketch, because of the section rule at 2843mm (I think its 2843mm It's in the class rules) download rules from http://www.i14.org/boat/rules/class.html

One thing I might try is a harder 'chine' on the hull, to incorporate the section data. I don't know what that will do to the heeled drag.

Tell me what you think,

Tim B.

[Tim B]

Its interesting, the more I work on the second option, the more I don't like the first as much. The problem is, that I don't know if I can get away with putting the defined section point (Rule 3 a and b), outside the beam of the canoe-body, and thus claiming that is irrelevant. I don't think I can. We don't have any official I14 measurers on the forum do we? Anyway, the second hull has a large planing surface aft, with slight deadrise. I'd like to put some strakes on for directional stability while planing. That's outside the class rules though isn't it.

Tell me what you think,

Tim B.

[CT249]

It's hard to see the sections in the rendering; the bilges look very soft to me. The many skiff and dinghy designers I've spoken to generally believe that a hull capable of I 14 speeds needs a chine for water release and directional stability.

[Tim B]

You couldn't tell me if we are allowed to put the defined section outside the hull could you?!! The second possible hull does embody a hard chine at the stern, becoming almost vertical at the bow... you'll see what I mean when I eventually post it. There's only about two days work to do on it, and I'll get that done by the 7th June (I hope, don't hold me to that!). With the first Hull I did, I was trying to move away from tube outriggers, and give a more comfortable boat. Though I agree, there isn't huge inherent longitudinal stability built in, which would require the sails to be set perfectly for the heading, and the boat to be flat. My great concern with a 'canoe' body and outriggers, is that the outriggers are not likely to help the boat to stay upright when it heels a long way over. I fear that they will tend to roll it in. Anyway, I'll post the second possibility in about a week.

Cheers,

Tim B.

[Tim B]

OK. slightly less than two days work!! I don't much like the shape of the canoe body, but it gives the general impression. As you can see, the hull sweeps from an almost vertical line at the bow, to a hard chine at the stern. I'll probably widen the hull in the first 2/3, just to make it look a bit better. Having said that, it's beginning to grow on me.

Cheers,

Tim B.

[Polarity]

Great thread all!...

I have been lurking around, reading with itchy Rhino fingers... I have never read a set of hull design rules - they take a bit of understanding! I think I got most of it in the end.

My first passes at a hull look not to disimilar to Tim's (which looks good to me!) except not as refined.. But then I got to thinking a bit ...and it all got a little more radical. the problem was I could not make it look even vaguely pretty!

I'll try and post by the week end...

Paul

[Tim B]

I have to admit, I liked the first design when I did it, perhaps I should just stick a rig above it and see what it looks like, the problem with the second is that I'm not sure I'd get away with it under class rules (see section data within class rules). I'll need to get a new computer first though! the second image took three hours to render on... a 486!!!! Thanks for the reply Paul, good luck, and do post any renderings.

Cheers,

Tim B.

[Polarity]

The class rules do dictate the shape quite a lot.... and thats after you can figure out what they are on about!

I have not even looked at the rig regs yet!

Paul

[Tim B]

Ok, talk about throwing something together, the first hull with the second boat's rig. It gives something of an idea of what the entire finished boat will look like, I felt I should render it, simply because I'm not used to looking at yachts without rigs.

This is it so far,

Cheers,

Tim B.

[SailDesign]

Tim,
This is what I have been playing with. Not many hours into it yet, but it's kinda fun. ;-)

Steve

[Tim B]

What I really love about this thread is that there are now several people trying to design to the same rules, all coming at it from different angles, and all producing different answers. Of course, short of model-testing we have no simple way of testing any of the hulls, unless someone has access to a CFD or VPP package that would cope with this size of hull. So we're really only going on empirical data and general knowledge. While I think of it, could we get some sort of indexing system going, because with different designs at different stages it could get complex. I'll take TBI14v1p1 for my most recent post (5th May 2003) and TBI14v2p1 for my previous post (2nd May 2003).

Therefore:
Steve's hull would appear to have a fantastic planing area aft, and I like the near-vertical bow. I would be concerned, though, that at displacement speeds (Yes an I14 can go that slow) we may lose some speed through the quite low deadrise forward. That said, It's much easier to build. I think generally it's good, perhaps a bit more deadrise forward, just to reduce the drag, but I like it.

Cheers,

Tim B

[Polarity]

What would be interesting would be if you guys could "talk through" your hulls why a particular hull form in that area, how it fits into the overall picture... Why you think it will be fast, what does it compromise? what conditions have you designed for? etc..

At least for a complete amateur like me it would be interesting!

Paul

[Polarity]

Umm did I mention I had some different ideas...? I have reason for the shape of most parts of the hull, Not sure if they all make sense though! It fits the rule I believe but its in development. Actually this is the less radical version...