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]

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]

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)

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]

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]

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.

[TimClark]

As others have stated, the bow looks a little fat. Also, I think that a wheel would be the way to go for a couple reasons. 1. Less space is being taken up
2. Boarding the boat from the rear would be easier because of the lack of clutter in the stern 3. Many cruisers prefer a wheel because of it's ability to easily hook up and autopilot to it

P.S.-What design program did you use for the boat?

Tim

[bhnautika]

If you convert from tiller to wheel on this boat you will have to take the step/foot well out of the cockpit sole as the boom would be to close to the head of the helmsman’s standing at the wheel as it is. This would also enable a longer bench seat, which you could also lay out on.
The companionway hatch is a little small for a cruising boat. There is only 1.24 metres (4ft) between the edge of the first step and the inside edge of the open hatch.
For the rig have you considered swept spreaders (no back stay) and self-tacking jib? Makes for easy sailing.

[solrac]

As others have stated, the bow looks a little fat. Also, I think that a wheel would be the way to go for a couple reasons. 1. Less space is being taken up
2. Boarding the boat from the rear would be easier because of the lack of clutter in the stern 3. Many cruisers prefer a wheel because of it's ability to easily hook up and autopilot to it

P.S.-What design program did you use for the boat?

Tim

As I stated on first posts, I'm just a naval aficionado, as an architect, I normally use Autocad, so it was preformed on it. The "fat lady" aspect was intentional, thinking that between comfort & speed, my option was comfort.

If you convert from tiller to wheel on this boat you will have to take the step/foot well out of the cockpit sole as the boom would be to close to the head of the helmsman’s standing at the wheel as it is. This would also enable a longer bench seat, which you could also lay out on.
The companionway hatch is a little small for a cruising boat. There is only 1.24 metres (4ft) between the edge of the first step and the inside edge of the open hatch. For the rig have you considered swept spreaders (no back stay) and self-tacking jib? Makes for easy sailng.
thanks for the advice, I've considered the spreaders option, but it depends on the availability & kind of mast at the moment of acquiring it. (don't forget such a mast system is as unavailable here in Uruguay as a green monkey with 2 tails) The only option is to import it it from USA or Europe or "adapt" an used model from another sailboat bringing it from Argentina or Brazil
Same concern about the tiler against wheel, tiler can be a wooden piece & some hardware, wheel must be imported or "invented"

As an example, there is only one operative CNC mill in the country, you must ask for it with 3 months pre advice.
another, there are just 2 naval suppliers in the country, mostly specialized in Optimist/Laser & some J24 spare parts, don't ask any weird part cause they'll laugh at your face...
Making a boat here feels alike Robinson Crusoe in his lonely island....

[bhnautika]

Solrac your road to building this boat will in deed be hard which bring me to the question of what material you plan to build with as the displacement looks like about 3000 kg.

[solrac]

Solrac your road to building this boat will in deed be hard which bring me to the question of what material you plan to build with as the displacement looks like about 3000 kg.

As calculated, the displacement is a bit higher, about 3500/3700kg.
I was thinking on a plywood structure (CNC cutted) reinforced with fiberglass (a kind of a sandwich) & a similar laminated multilayered hull (plywood/fiberglass) I think I can achieve enough strenght & low weight.

[Raggi_Thor]

Will you contact a designer or nav arch for help on the final hull shape and then do the interior yourself?

[solrac]

Will you contact a designer or nav arch for help on the final hull shape and then do the interior yourself?
I already did. it's mandatory here registering any sailboat with a Nav.Arch signature..

[bhnautika]

Solrac at that displacement it seems ok. I would go a little higher (nobody complains if the boat comes out lighter).
As for supplies, sometimes it pays not to think boat!

[solrac]

as stated, by calculations done (I'm not a specialist in this matter, but..)
Displacement about 3.5m3
LOA 10.00m LWL 8.50 BEAM 3.30
keel about 1300kg (depending on final weight of hull) but draft no more than 1.70m (no more water at port here), even thinking about a semi mobile keel, discarded it because it's a nightmare sailing with it in open waters
Mast (estimated by now, depending on availability at the moment) 14.00/15.00m
Think of an internal power about 30/40hp
by the way, seen on another post about tandem keels (http://www.boatdesign.net/forums/showthread.php?t=10395) would it make any sense or it's only marketing technique?

[bhnautika]

I would keep it simple, the time and money to design and fabricate that type of keel can be better spent.

[solrac]

I would keep it simple, the time and money to design and fabricate that type of keel can be better spent.
ok, thanks for the advice, let's be traditional....
I suspicted from the beginning, that type of keel can't equal stab force than a traditional, as the mass distribution implies less distance must have a lot bigger weight... although, the only pro I've seen: less draft

[bhnautika]

Solrac since you have autocad it maybe worth your while to 3d model the interior as it would give you a feeling for the space and speed up the construction side a bit.

[terhohalme]

Sorry, been on holyday trip last week.

I meant that the mesh surface is "bumpy", not the design. LWL/BWL about from 3 to 3.5 and half angle of waterline < 20 degrees is quite reasonable for a cruiser.

Terho

[jedclampit]

Slorac,

I'm in the same boat...an engineer looking to build a custom sailboat with the same characteristics. If you like fat with a big fridge, look at the Bruce Robert Designs…You won’t win any races, but you won’t spill your beer either.

http://www.bruceroberts.com/public/HTML/plans1.htm

[solrac]

Guys, finished the interior design, attaching the drafts.
greetings.

[jedclampit]

I like the Design...nice work...I'm only concerned with the headroom in the forward cabin… and/or the head. Also it appears the headroom at the cabin hatch will be a bit too close for comfort and you will regret sometimes when you enter or exit the cabin and knock your head. Just my newbie thoughts...

See attached dwg

[bhnautika]

Solrac, jedclampit drawings show what I meant about the wedge shape in plan view (thanks Jed):) affecting the headroom. Maybe you should do an interior profile which will show seating height in relation to deck.

[jedclampit]

The human in the drawing is only 5'-6" tall...I always design for a six foot human because I’m only 5’-10”, but others might be taller and require more headroom.

If it was me and I was in love with the profile of this hull, I would try to move the head aft to the galley location. I would expect to have to crouch over or bend down in a 20 footer but not a 30 footer.

I also don’t like small galleys with limited storage. I would swap the mid deck berth across from the settee / dinette for a galley with large refrigerator and freezer boxes. If you are spending more than a weekend onboard (in my opinion) this would be a requirement.

I have traveled throughout the Bahamas on a power cruiser and have found that typical locations with provisions are usually not the best quality (limited selections and mostly old food) or the best price. Some locations I would not have wasted the fuel to get to port. On a power boat, if you run out of beer (or food) and the only place for provisions is 25 to 50 km away, then you are less than two hours away, but on a sailboat this could take you all day. And I know from experience that if I go without food or beer for that long of a period I become cranky and would probably end up in the dog house with the first (in my case the second) mate.

Just a though from the peanut gallery.

[solrac]

thanks a lot guys, I have yet seen the height problem, & the solutions, maybe a bit deeper hull or some extra centimeters on cabin roofing.
working on it. will post it asap.

[solrac]

Let's see it now, redesigned interior (sacrificed a seat for extra beer capacity) & even I still don't like it, incremented cabin height. will need some more work.

[bhnautika]

Solrac the new overhead bunk won’t work, as there is only about 300mm between bunk and deck, you need 600mm rollover room. The cabin in profile is starting to look a little chunky for the amount of freeboard, maybe if you increase the shear height a little you would get more headroom under the deck and more balance to the design. If you need that much sleeping area look to a convertible berth at the saloon table. The vee berth in the bow doesn’t have to be that long, which would give you some more room to put into the anchor locker. The large hanging locker opposite the head may be hard to construct as it is half under the deck and the rest is running up the side of the cabin.

[solrac]

Solrac the new overhead bunk won’t work, as there is only about 300mm between bunk and deck, you need 600mm rollover room. The cabin in profile is starting to look a little chunky for the amount of freeboard, maybe if you increase the shear height a little you would get more headroom under the deck and more balance to the design. If you need that much sleeping area look to a convertible berth at the saloon table. The vee berth in the bow doesn’t have to be that long, which would give you some more room to put into the anchor locker. The large hanging locker opposite the head may be hard to construct as it is half under the deck and the rest is running up the side of the cabin.

ok, let's see the attached release 14.8... no bunk, & the cabin profile.... it's not only chunky, it's awful, makes me throw... think better cut this crap & begin with a serious sailplan from a professional....

[bhnautika]

Solrac I would never put any gas in a locker inside the boat. Also it makes it harder to trim the boat when one weight (batteries) is balanced with a consumable on the other.
Don’t give up on the cabin shape, just refine it .The windows could be made smaller and their shape altered slightly. You will get more harmony if you extend all the edges and outlines of cabin and windows up to roughly a single point. I know you seem reluctant to increase the sheer hight but I think you are going to have to. Having modelled the boat originally on a race boat, different priorities.
The spinnaker I wound go asymmetric, can be handled easier. The interior is coming along, why is there (I think) a step in the sole near the nav area.It maybe time to do some joinery sections thru the hull and deck.

[bhnautika]

Solrac I hope you don’t mind but I did a quick sketch of what I meant in my last post, 100mm more freeboard and moved the lines of the windows. I also reduced the back of the coach house a little and lengthened the front a little. I don’t have Autocad so I hope the translation will work.

[solrac]

Solrac I would never put any gas in a locker inside the boat. Also it makes it harder to trim the boat when one weight (batteries) is balanced with a consumable on the other.
Don’t give up on the cabin shape, just refine it .The windows could be made smaller and their shape altered slightly. You will get more harmony if you extend all the edges and outlines of cabin and windows up to roughly a single point. I know you seem reluctant to increase the sheer hight but I think you are going to have to. Having modelled the boat originally on a race boat, different priorities.
The spinnaker I wound go asymmetric, can be handled easier. The interior is coming along, why is there (I think) a step in the sole near the nav area.It maybe time to do some joinery sections thru the hull and deck.

thanks again for your patience, feel as I'm on a kind of abuse..
your concern about the gas container & the batteries, the cylinder alone weights 60kg, it's designed vor vehicle use, carbon-steel there is not any security issue within.(attach a photo) the weight balance, think batteries would weight about the same, the weight difference will be the 60lts gas (60ltsx0.84=48kg, not real difference)
I will modify the hull lines to get some more height as you sugested, still don't like the cabin shape. as an old master always said: needs a couple more sheets of paper....
thanks again

[jedclampit]

Sorac,

There was nothing wrong with your first design… just a few headroom issues… which is a personal choice… I’ve seen many boats where you have to duck your head here or there… not a problem. The only (my personal opinion) real issue is trying to take a shower or wash your hands in the head. And of course, the cabin entry issue. I only pointed it out because I have to put a large rubber pad on that location on my current boat…I’ve hit my head once too often. I would just tweak the first plan to make the cabin acceptable.

I don’t know why you have not used the dinette /settee as a double berth. Almost every boat has this arrangement…it’s very common and there is a reason for it… it works and saves space…. Just a thought…

I would just move the head aft and move the dinette forward... simple changes would help you keep your original configuration….

Here is my revision to your original concept… I had to convert to inches and this is just a rough idea… you’d have to make the adjustments to fit your needs…

I agree…don’t put the gas inside the cabin…use a cockpit locker...

Jed.

[jedclampit]

just for kicks

[solrac]

sorry guys for the time to answer, was working outside home for 2 weeks. just returned yesterday, promise to answer soon. thanks again

[bhnautika]

Jed your layout flows well, I would look at your door opening’s there a bit small (min 20ins). The distance between mast and dinette seat is too small to swing legs past.

[bhnautika]

Solrac I was looking at the waterlines and they don’t seem to refect the section lines. How are you generating your line drawings and from what hull model?

[jedclampit]

BH...
Yes you are correct...I didn't spend much time...just playing on concept...
I would much perfer to have a center table fixed on the mast that would fold away...I've seen this a 100 times...and works well but then you lose the ability to have a double berth...

Anyway if I had the time I would work on a v 2.2...but I have my own projects... :)

Good luck and thanks...

[FAST FRED]

"just for cruising"

If cruising is your desire starting with a race boat hull is a disaster.

Seakindly and seaworthy are far more important than .0001K or a low "rating".

First take a look at all the numbers , after the boat has an extra ton of "Cruising needs" placed aboard , and see where she sits.

FAST FRED

[solrac]

hi guys,
when I started this crazy idea of homebuilding a 33ft sailboat, about 2003, started searching the net for a starting point, and found (as I told on my first posts) an interesting info from someone in Sweden, who was on the same idea.
Well, the Swedish guy (Henrik) has completed the job, and posted a page with all the stuff. surprisingly, found today his internet page with the original sailboat from where I took the idea. (mmm, honestly I took some more than the idea, drawn the hull lines as similar as possible to the original model)

http://web.telia.com/~u21114029/#

[bhnautika]

Solrac I now see the problem, I think you are losing the fairness of the hull in translation from one to the other. I was wondering if the model you posted in thread nine was done in Autocad. I put a surface over your lines, then put a Gaussian Curvature map over the surface (see JPG) as you can see the bow section has a lot of lumps and hollows in it (red=hollow, blue=curve). If you like I can clean this up for you and maybe supply some more 3D lines.

[solrac]

bhnautika: thanks for your offer, would appreciate it too much, but think I must try it by miself. otherwise (abusing from you and the rest) will be something like stealing someone´s design....
The original lines I took from the net, were aproximated from an JPG image, then translated to autocad, scaled & retouched to fit a couple of spline curves & finally surfaced in Autocad. I´m conscious the result is not as good as a result of the freeship design proggie, but on those times I´ve never heared of it. last week downloaded the freeship v2.4 program & still familiarizing with it. promise for the weekend to post a new hull result surface and arrange of the cad model.(in advance preliminary hull results, lack of some severe hammer retouch...)
thanks again.

[bhnautika]

No worries. Like to see the new hull when you’re ready

[MikeJohns]

Solrac

I don't want to call rain on your parade but ....

I was wondering what sort of cruising you intended to do?

Form should not be put ahead of function. Racing hulls make poor cruising hulls and the demands are diametrically opposed.

Also have you done any preliminary weights and moments calculations with full stores life raft dinghy outboard, Solar panels, Wind generator etc .

I would also be very mindful of your stability curve with this sort of design used as a crusing boat. The keel and rudder are both deep and vulnerable to severe damage from collisions and grounding. I beleive a cruising boat should survive a collision with a reef at hull speed.

The hull is far from balanced, hard work for an autohelm.
Will also be a bit light for comfort in a seaway. Were you cruising alone or with family ? Hard racing sailors are quite a different breed to family members, too many get off after the first passage because of the intense discomfort sailing in light boats. Have a google for "comfort factor".

Do you have enough sweep back on the spreaders? This should be at least 30 degrees to make it worthwhile.

just my humble opinion

All the best

[solrac]

Solrac

I don't want to call rain on your parade but ....

I was wondering what sort of cruising you intended to do?

Form should not be put ahead of function. Racing hulls make poor cruising hulls and the demands are diametrically opposed.

Also have you done any preliminary weights and moments calculations with full stores life raft dinghy outboard, Solar panels, Wind generator etc .

I would also be very mindful of your stability curve with this sort of design used as a crusing boat. The keel and rudder are both deep and vulnerable to severe damage from collisions and grounding. I beleive a cruising boat should survive a collision with a reef at hull speed.

The hull is far from balanced, hard work for an autohelm.
Will also be a bit light for comfort in a seaway. Were you cruising alone or with family ? Hard racing sailors are quite a different breed to family members, too many get off after the first passage because of the intense discomfort sailing in light boats. Have a google for "comfort factor".

Do you have enough sweep back on the spreaders? This should be at least 30 degrees to make it worthwhile.

just my humble opinion

All the best

"Form follows function" said one of the biggest modern architects (Ludwig Mies Van der Rohe)
first, thanks for your advice, but my main interest is not a round alone, nor an America cup. just a design for cruising on weekends & holidays.
Maybe the cruising concept I have will sound weird to you, but here, (Uruguay, South America) the cruising distances we are acustomed to, are mostly summer sailing from Montevideo to Punta del Este (about 100kmts) and at least coastal sailing to Florianopolis - Brazil, about 1500kmts on about 10 to 15 days, and at least 2mts height waves, never as far as 10miles out from coast... (by the way, no coral reefs in this side of the world)
In my ears I´m still hearing someone of you shouting: "don´t waste our time, buy yourself an optimist!!!" hehehehe....
I admit, there is a kind of exageration in the tanking volume, but it´s just a preliminary sketch. probably on future drawings will adjust the weight & balance, but by now, think summing all stuff, we are around the 4.500 tons... (with a calculated displacement of 4.188 tons) maybe I´ll float a little deeper, a little slower, but still float...
About spreaders, seen other posts here recomending about 20 degrees, may I ask why 30? reduced tension?
and finally, thanks to all for your help.

[bhnautika]

Solrac 30 degrees would be the max angle. The reason for swept spreaders as you probably know is to remove the backstay and shifting the fore and aft staying to the lateral (side) shrouds. This then becomes a problem of vectors, the more you shift the push of the stay back to support fore and aft you reduce the support in the lateral direction. Also the more sweep the further back the chainplates can be placed, sometimes increasing the chainplate base, which allows for a lighter mast. There tends to be more tension in these rigs as they are not just holding up the mast but also tensioning the forestay.

[solrac]

Hi guys, as promised on last post, drawn some changes to the hull, with freeship, (now version 32.9 or 39.2, don´t remember...)
regards
Carlos

[jedclampit]

Solrac,

Hey, thanks for the link for the designer builders website...very nice job, don't you think? You hope that you understand that they built this boat to race with a crew of six. Thus the hi-tech materials (lightweight), wide deck, small cabin and open cockpit. You need 4 or 5 bodies hanging over the sides to reach top speed. This design works great for their requirements and I too also like their design, but this boat was not designed for comfort or ease of handling.

If this meets your requirements, then I’d say you found your dream boat…if you want speed you’ll have to have a crew…and watch your head… that’s just my two cents…not really worth that much in these times… good luck!

Nice job on the Acad file…

[MikeJohns]

"Form follows function" said one of the biggest modern architects (Ludwig Mies Van der Rohe)

About spreaders, seen other posts here recomending about 20 degrees, may I ask why 30? reduced tension?
and finally, thanks to all for your help.



Regarding function , my comment was that you are designing a racing boat
for cruising.:)

As for spreader rake .. Sorry Solrac I am always in too much of a hurry I should state more information. From your early posts I glanced at it appeared that the rake was very small, small rake is not worth having and you are better going inline. 30 deg is the maximum but the final rake really depends on the design spiral too.

If it was just a question of rake 20 deg is alright too for most designs however 15 deg. is too little.

You may not need any depending on what sail combinations you fly and from where. I presume your rig is going to evolve further?

For some of the issues have a look at:

http://www.boatbuilding.com/article.php/rigdesignhints

[solrac]

ok kids, that´s the challenge.... a cruiser design with the elegant lines of a Vo70 racehorse, or a cruiser that resembles a petroleum bulker tanker shaped vessel like the Exxon Valdez? which would you prefer for holidays?
That´s the reason (I think) for spending time redesigning the original swedish racer for better interior spaces, the cabin height & the rest.
Maybe (surely) will end up with a sailboat really too fat/ heavy for racing and as spartan and uncomfortable as a naked racer, but I will not give up (at least not yet). in that case, the obvious solution, make a good fire with the sketches & buy a real industrial made sailboat... :D :D :D

PS. posting the new modified 3d model

[tamkvaitis]

sorry, but this boat is ugly, for me

[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.

[solrac]

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]

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....:D :D :D :D
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]

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]

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...:D
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]

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...:rolleyes: