Sailboat design

[solrac]

Originally Posted by bhnautika

Solrac don’t give up, Rome wasn’t built in a day (“two maybe, three tops”). The original hull shape based on a generic IMS hull form is more than adequate for the type of sailing/cruising you want to do. These types of boats enter and win the toughest ocean/ coastal yacht race in the world (Sydney to Hobart) so it does not take much to change them to a more coastal cruising type of boat.
You need to sail with less crew?
Change the displacement/ballast add more ballast make the boat stiffer. Set the boat up for shorthanded sailing, if one man can sail a 60 ft boat, 33 is no problem. It just a matter of systems.
The hardest boat to design well is a small boat; humans are just to damn big!
The hull is coming along. Remember longer waterlines are faster but watch out that your fore foot doesn’t get to deep as it tends to take over the steering on a run.
There seems to be a hollow running down the centreline this I think is a fairing problem in the computer model. May I suggest you work on just the hull first, then go back and add deck, cockpit etc.

thanks again for your support, the problem of sailing with reduced crew, think is easily solved, remember the big water tanks in the model? a good old water pump and a couple of electro-valves will make a marvelous primitive "movable ballast system"
the hollow in the centerline, (excuse my primitiveness, haven't discovered it) surely a bug on the freeship model or in translating to autocad.will check it soon.
Untill construction time, not too worried about the hull bugs & hollows, just need to plot the section lines, translate (carbon paper) to plywood, and try to assemble them properly. On that stage, all bugs & hollows will be corrected (one of the greatest master Architects said "there is no miracle on nature most perfect than synchronization between hand & eye" so, I'll trust on that to correct all mountains and valleys....

[bhnautika]

Originally Posted by solrac

one of the greatest master Architects said "there is no miracle on nature most perfect than synchronization between hand & eye" ....

So true, too many people jump to technology to soon.It’s important to keep the art.

[solrac]

excuse me, art? ART? ART? sorry if it sounded as more interested in art than hydrodinamics....not that kind of guy....
I was just talking about curve appreciation on a tactile & visual basis as a simpler way to detect surface defects as oposed to computer simulation models. (a variation on a method I have learned at university) I'm convinced that, as a negative mold can be easily done in plywood / plaster or whatever you can find out there, all defects the model can bring are simpler to correct with some sanding & plaster, before using that mold to produce the positive piece.
In my working experience (more than 25 years on pre-cast concrete & molding in civil & architecture) can say that 90% of design or mold defects can be corrected this way...

by the way, I'm not expecting to paint the ship in pink....hehehehe

[bhnautika]

Solrac sorry you misunderstood my meaning. Navel architecture/boat design has always been a mixture of art and science. When I first started designing we used nothing but splines, weights, ships and French curves. To look along and draw a long sweeping curve was one of the great delights. The shifting of weights and taping the splines to detect the slightest movements, was both tactile and visual. The computer has taken the hackwork out but it is still just a drawing board and pencil with a planimeter thrown in.
The best way to do any job is your own way.

[MikeJohns]

Originally Posted by bhnautika

I first started designing we used nothing but splines, weights, ships and French curves.

But the number of erasers that you wear out !

[bhnautika]

Arrh yes, but the getting of wisdom.

[Tim B]

Interesting last few posts here.

I actually started designing using the pencil and film technique for model aircraft. Produced a few nice drawings as well. Aerofoils became hard, though, and when I found out that you could analyse them on computer and draw them, the hard bit was taken out of the drawing.

Several years later I was arguing the benefits of 3D CAD in design and I was asked to do a glider design. So, using a 3D CAD package, I designed everything in 3D. (piccy attached below)

So onto boats. The first I did in 3D (contract fell through sadly) was a 47 foot Powercat. I'm now doing a 46 foot cruiser for a GDP and we're starting to realise exactly how useful 3D CAD actually is. I'm also doing a 35 foot high-performance cruiser (Could be RCD class A (though I was aiming for class B)) which is also designed completely in 3D CAD. One of the most convenient aspects of this is being able to fit things, and also being able go between CAD, stability and performance prediction fairly easily.

As for CAD v Drawing board? I still do preliminary general arrangements by hand, but usually on A4 paper roughly, then I work to fit everything in CAD. There's nothing wrong with using a drawing board for the whole lot, but having 3 dimensions to work in is incredibly useful. In my opinion it would be foolish not to use modern technology where it can help so much.

That's not to say the art should be forgotton, of course, it just changes into a need to practice.

Nothing and everything changes,

Tim B.


ps. Feel free to e-mail me if you want to see more of the model glider.

[SouthSail]

Whoever said that IMS Boats were SLOW must be mistaken. Unstable, yes, and with that little high aspect keel for sure, unless you’re running at 12+KNTS.
I would have a heavier displacement boat if you wanted more comfort. You can still have a fast boat without all those flat section forward. That Hull shape looks very uncomfortable into the wind. Like a rocket off the wind, but very difficult to take any-ware with the breeze on you teeth.

Rick

[solrac]

Originally Posted by SouthSail

Whoever said that IMS Boats were SLOW must be mistaken. Unstable, yes, and with that little high aspect keel for sure, unless you’re running at 12+KNTS.
I would have a heavier displacement boat if you wanted more comfort. You can still have a fast boat without all those flat section forward. That Hull shape looks very uncomfortable into the wind. Like a rocket off the wind, but very difficult to take any-ware with the breeze on you teeth.

Rick

I must admit, sailing is a compromise... as an old sailing guy, I'm more interested in comfort than speed, got a 4 members family to acomodate, but that does not mean, the comfort level of the "C" Caribbean Cruisers, as also not interested in 15 days holyday cruising on a high speed windsurf table or a spartan raft... the design is mostly intended for sail-cruising, but on a reasonable speed basis, maybe what achieved is not a comfortable cruiser, also a sailing turtle, but as stated, it's a compromise...
I've started thinking on a "heavier displacement boat" maybe a Roberts 40' steel hull instead...
by the way, just began tracing the sections for CNC cutting...

[bhnautika]

Solrac if you are thinking of a boat in steel have a look at the Van De Stadt 34
http://www.stadtdesign.com/products/vds391.htm
It can also be built in wood.

[solrac]

Originally Posted by bhnautika

Solrac if you are thinking of a boat in steel have a look at the Van De Stadt 34
http://www.stadtdesign.com/products/vds391.htm
It can also be built in wood.

thanks, just keeping an eye on all the Roberts site... there are some models that look some "old fashion" but others woooow. like them too much.
However it comes the future, my messy design or a professional made, I'm still now at the planification stage, for the final decision about materials & building technique still not sure, a couple years ago, have seen here at the Yatch Club, an argentinian VdS steel made, don't remember exactly but think it was about 26' & seemed a bit corroded (even we have not very salty waters here) that keeps me a little anxious, imagining me with a mag glass all day checking under flloor panels...