Sailboat design

[solrac]

hi guys, I'm a kind of a newbie to al this concerning to design of a 30" sailboat. I'm a 50 year architect (not naval arch, only arch) been sailing since I was 12.
For the last 30 years, I've designed & built my own daysailers, so i decided it's man on board time & started from scratch (70% from scratch 30% from internet data) my dream design sailboat, a kind of a IMS33.
Would appreciate any coments about the design.

[Guillermo]

Originally Posted by solrac

hi guys, I'm a kind of a newbie to al this concerning to design of a 30" sailboat. I'm a 50 year architect (not naval arch, only arch) been sailing since I was 12.
For the last 30 years, I've designed & built my own daysailers, so i decided it's man on board time & started from scratch (70% from scratch 30% from internet data) my dream design sailboat, a kind of a IMS33.
Would appreciate any coments about the design.

Could you please post the images in a JPG, BMP or the like format. I have not CAD programs at the home computer, so I cannot open DWG files...
Thanks in advance.

[tamkvaitis]

Nice job, although I didn't like the shape of the hull. It looks litlle bit to "fat" in the front part of the boat, but if you done the calculations right and lcb and lcg is right then its nice. Why only one spreder? or is it only sketch of the rig? I'd like it more if the cabin was lover or totaly removed in front of the mast I would be more beautiful (for me)

[terhohalme]

The lay out and the idea is OK. 3D-model tells more about difficulties in AutoCAD while making 3D design. The hull is very bumpy and unfair. Try Rhino or Free!SHIP and minimum number of control points to design a fair hull. Use NURBS surfaces, not meshes.

The best results I've got in modern sailboat hulls is to use 3 x 3 control point surfaces and changing the point weight to get the shape, LCB and prismatic coefficient right.

Happy designing

Terho

[terhohalme]

Here is one example:

[usa2]

may i inquire to as why you modeled it on an IMS 33? Most IMS boats are inherently slow and unstable by design.

[solrac]

Originally Posted by tamkvaitis

Nice job, although I didn't like the shape of the hull. It looks litlle bit to "fat" in the front part of the boat, but if you done the calculations right and lcb and lcg is right then its nice. Why only one spreder? or is it only sketch of the rig? I'd like it more if the cabin was lover or totaly removed in front of the mast I would be more beautiful (for me)

Ok, thanks for the advice, as I told in first post, I'm just a "naval aficionado"
the design is a really fat lady, not intended for regatta, just for cruising, & the main design reason is comfort, not worried about speed (just a kind of a floating home but with sailboat appearance). Only one spreader just for easy handling & sailing, not intended for a crew of 8...
The cabin height reason, my first sailboat was a woody 21' nicknamed The toaster, to roll on the bed you must first keep out, roll & get into bed again, I'm too old for that, would appreciate some comfort, to be able to stay stand in the cabin changes my life (my back & bones will thank a lot for that extra centimeters) Also, I'm not concerned too much for speed, not either thinking on a Round Alone (my wife promissed to drill it like a cheese if I'm not back home on sunday night for dinner)

Originally Posted by terhohalme

The lay out and the idea is OK. 3D-model tells more about difficulties in AutoCAD while making 3D design. The hull is very bumpy and unfair. Try Rhino or Free!SHIP and minimum number of control points to design a fair hull. Use NURBS surfaces, not meshes. The best results I've got in modern sailboat hulls is to use 3 x 3 control point surfaces and changing the point weight to get the shape, LCB and prismatic coefficient right.

You say it's very "Bumpy", think meant the same tamkvaitis said about "fat aspect" do you think it will compromise the sailing behavior?
In our southern waters (Rio de la Plata / Uruguay / Argentina / even south of Brazil) we have not really bad waters, short wavelenght & about 1.50mts wave hight. in open water may have long wavelenght & 2.50mts high, winds in the 11/15knots (not intending to sail under a real storm on a homemade sailboat, there are cheaper ways to suicide...)

What can I say? it's only a pastime/vice, like a daysailer but a little bigger & comfortable...
Once I've heard an old sailman saying: "Who goes to sea for pleasure, will go to hell for a pastime"

[mholguin]

Why two set of runners on each side? This will prevent the mainsail to open freely when running, and will add up to more work, which can be a burden when short handed. How tall is the rig?

I could be wrong, but two set of spreaders can make your life easier, and if the rig is not too tall, you may even not use the runners at all (depending of course of the type of mast used)

[solrac]

Originally Posted by mholguin

Why two set of runners on each side? This will prevent the mainsail to open freely when running, and will add up to more work, which can be a burden when short handed. How tall is the rig?

I could be wrong, but two set of spreaders can make your life easier, and if the rig is not too tall, you may even not use the runners at all (depending of course of the type of mast used)

thanks for the answer, as you stated: spreaders, well, one may be a bad choice, they came from a standard model mast & boom seen in internet,
It's not decided yet, maybe can find another mast model with more than 2 spreaders, even 3,
about runners: I don't like them at all, but think a forestay only may compromise mainsail size (may be an option a hydraulic fastener?) & also will change force centers, even will need to move mast to front a bit. in that case all stability calculations must be done again & not sure the final "behavior" of the boat will be the same (don't forget, I "borrowed" the original design from the net & made minor adjustments, I'm not an expert tecnician, just an "aficionado").
I'll post some renders of the surfaces as asked for Guillermo.
again, thanks for all advices.

[tamkvaitis]

I would rewove one of the rear bunks with cocpit loker, it would make sailing a lot easyer, because, you always have a lot of struf on an ordinary cruiser. I would remove the stering mechanizm to it looks like some kind of nonscence. Or you should instal "normal" stering weel instead, it would create a lot of space in the cocpit. And I would try to move the engine as far aft as posible (I like dashev concept) It would make a lot of space inside. Actualy you should look more on th dashev boats, thay look (I have not sailed any) great sailing boats, with huge amount of comfort. IMS isnt the one you should look for as an example. Do you have a list witch includes what you want from your boat I think it should look something like that
1. Comfort ashore
2. Comfort then sailing
3. sailing performance
4. Looks

You should know how much people will sail this boat, How long etc. Knowing enables you to design your boat many times more comfortable.

[bhnautika]

Solral
Terhohalme is right. From the line drawing of the sections it appears you have some major localised flat spots, hollows and maybe even creases. This is a surface fairing problem of the type of cad you are using not about the shape. You mentioned your sailing type as cruising. If this is the case don’t go for the wedge shape in the cabin in plan view. If you transpose the outline of the cabin on to the layout plan you will see that above most of your seating areas you have little or no headroom and no shoulder room or full headroom in what I think is the head.
If you still want to keep those racy sheeting angles you could put the tracks on the cabin top. The rig could lose the runners for your style of sailing, maybe a running backstay for mast bend and a baby stay to stop the mast from pumping.
Style is always up to the individual but you seem to be mixing old and new together.
Good luck you are on the first steps of the design spiral.

[solrac]

yes, you discovered me. must recognize, I'm an old fashioned guy, can't get out of my mind the old "fat" designs I've sailed 20 ys ago & of course, I'm not a specialist, no experience on this kind of surface design, only an enthusiast of sailing, with some experience in architectural design (maybe the interiors are best than exteriors in this sailboat?)
I'll work on the steering mechanism (don't you think a wheel will reduce too much the cockpit space?) and the engine. thanks again
PS. my list includes exactly what you stated:
Comfort on harbour
Comfort as sailing
and a reasonable big fridge full of ice & beer

[tamkvaitis]

steering weel uses less space in the cocpit than tiller, you need a lot of space to turn it, and if you are sailing with friends free space would probably be hard to find , and mounting autopilot system (which might be very usefull for sailor like you) would be simplier to.

[Windvang]

Originally Posted by tamkvaitis

steering weel uses less space in the cocpit than tiller, you need a lot of space to turn it, and if you are sailing with friends free space would probably be hard to find , and mounting autopilot system (which might be very usefull for sailor like you) would be simplier to.

I don't agree with that. A folded up tiller takes less space in harbour than a wheel. With an open transom like this it is much easier to access the boat trough the transom from a dinghy or pontoon than with a wheel. A wheel is also much more expensive.

[tamkvaitis]

I was talking about cocpit space then sailing. This design uses stering system similar to stering with steering weel it is dificult to see, the ruder is in front of the tiller! I have seen prety nice removable and rotating stering weel systems, so it can be removed or rotated, to minimize place required.