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Thread: Designing a Sailboat

  1. #36
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    Default Re: Designing a Sailboat

    , and much heavier too.

  2. #37
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    Default Re: Designing a Sailboat

    Quote Originally Posted by JimConlin View Post
    There are other people who experiment at measuring the properties of wood species, the Forest Products Lab of USDA. Look up their wood handbook. Itís available online.
    Thank you Jim, I'll be taking a look at that very soon.

  3. #38
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    Default Re: Designing a Sailboat

    Quote Originally Posted by Rumars View Post
    There is nothing wrong with hemlock, it's just a core, the natural durability of the wood is irrelevant as long as you don't have any unprotected holes. You could just as well use balsa and there would be no problem. If you stay with the equivalent weights of your proposed CSM layup (you should not use CSM and polyester on hemlock) you will have 72oz fiberglass in epoxy, 1/4" hemlock core, 36oz fiberglass.
    Just be sure any hole into the core has an appropriate epoxy plug, and you will be golden.
    Black locust is very good for any non-encapsulated elements, like a rubbing strake or an external stem.
    Hey Rumars,

    That was my thought exactly, to encapsulate the core in fiberglass epoxy. However, the amount you are suggesting sounds like it will make the boat very heavy. I've not done the math yet, so I could be wrong about that.

    As for Black Locust, I was considering building the rudder and dagger board with it. Still, I thought it would be best to seal it with something. I thought perhaps Dura-Lux Marine spar varnish. Also build the cockpit sole with it as well. But, for it to be removable for easy cleaning of the actual fiberglass cockpit. In other words, the black locust sole would be more of a wood grate and in a way just for looks. I know that sounds kind of a redundant procedure, but like I said, I'm a "think outside the box" kind of guy, and perhaps I do go a little overboard with my ideas.

    Thoughts?

  4. #39
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    Default Re: Designing a Sailboat

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    The Hull dimensions are pretty close to those for Uffa Fox's Flying Fifteen
    See https://www.flying15.org/The-Flying-...Specifications

    But that has an (approx) four hundred pound keel, 10% less sail area and is raced two up.

    Double trapeze???
    That is actually a very good point that I've been thinking heavily on. I would really like a retractable keel and I'd like to give some substantial weight to it. However, the idea of a mechanical lift system is not desirable in this case. I mean, I'd really like to lift it manually. I have some ideas for it, but still it would be a bit of a strain even with two good strong arms. I may have no choice but to build a mechanical lift system. I don't know, it's really not a very big boat and perhaps reducing the sail area is the best course of action. Having said that, my original goal was to sail a sleek little dinghy in light winds on the lakes of North Georgia. I guess there's still a lot of considerations to go through.

  5. #40
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    Default Re: Designing a Sailboat

    Quote Originally Posted by timo4352 View Post
    The bigger the boat, the greater the loss in time and money should a self designed boat be a flop.
    It has happened before...right here on this forum.
    My last build, a 22 foot outboard skiff, was built to an existing plan.
    I don't have a fortune in it, but could not imagine the feeling of wasting even 10 or 12 Grand plus 3 years time on a possible turd.
    Questionable materials...? I wouldn't do it, unless you don't care if it lasts more than a few years.
    My first little 13 foot sailboat was built from altered plans with cheap plywood...it worked OK and was fun, but I have graduated to using better materials, and un-altered plans since then.
    Consider how precious your time and money are to you before proceeding...
    I'm not saying "don't build"...just build it wisely and enjoy every minute of it.
    Good luck to you.
    That's very good advice Sir!

    I can assure you, I'll be doing all kinds research and will have my ducks all in a nice neat row, before I even start the first step to building this sailboat.

  6. #41
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    Default Re: Designing a Sailboat

    I have been following this thread for a bit. I am a novice and when when I decided to build a sailboat at age 61, I was going to design my own, just cause. Did a scale drawing and spent around 10 hours doing a table of offsets from my design. Learned a bunch of cool boat building words, and I am a clever guy. My design ended up being a warmed over Snipe. My sailing experience has been crewing for my Dad and other skippers for 6 years before owning one and quickly learning I couldn't afford the racing, or the maintenance. This was a 6 year period between age 16 and 22. The last thing I wanted to hear about my design was, "that looks just like a warmed over Snipe".... Just my 2 cents, Thanks for reading.
    Matt Jones

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    Default Re: Designing a Sailboat

    Robert,
    From what I am reading, you have put some time into designing this boat, and you have a good background in woodworking. If you enjoy the design aspect of such a project, I will say, "Go for it." When following someone else's plans, at each decision point those plans will give you guidance. When self-designed, you need to stop often and decide which alternative to use for each design detail.

    Sail area: You know what kind of wind that is expected, but also listen to advice. Hemlock: I recently completed a table built entirely of Hemlock; a nice wood to work with. If the wood will be entirely encapsulated, then you should have no problems.

    Over the years, I have designed and built eleven boats, only one of which I would call a failure. That failure was due to having too many design goals. Better to concentrate on having a boat designed for one major purpose.

    developable-surface-boat-designs.blogspot.com

  8. #43
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    Default Re: Designing a Sailboat

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    The Hull dimensions are pretty close to those for Uffa Fox's Flying Fifteen
    See https://www.flying15.org/The-Flying-...Specifications

    But that has an (approx) four hundred pound keel, 10% less sail area and is raced two up.

    Double trapeze???
    Hey P.I. Stazzer-Newt,

    I just took a look at the "Uffa Fox's Flying Fifteen" and you're right, it is very close to what I'm trying to design. As a matter of fact, it even looks a lot like what I'm designing as well. It's kind of funny really, cause I've never seen that boat before till just now. Well, you know what they say... "There's nothing you can do or say that hasn't been done or said before".

    Thanks for the link! One thing for sure, I'd love to sail that baby!

  9. #44
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    Default Re: Designing a Sailboat

    Quote Originally Posted by jonesmatt1957 View Post
    I have been following this thread for a bit. I am a novice and when when I decided to build a sailboat at age 61, I was going to design my own, just cause. Did a scale drawing and spent around 10 hours doing a table of offsets from my design. Learned a bunch of cool boat building words, and I am a clever guy. My design ended up being a warmed over Snipe. My sailing experience has been crewing for my Dad and other skippers for 6 years before owning one and quickly learning I couldn't afford the racing, or the maintenance. This was a 6 year period between age 16 and 22. The last thing I wanted to hear about my design was, "that looks just like a warmed over Snipe".... Just my 2 cents, Thanks for reading.
    Matt Jones
    Hey Matt,

    I know what you mean, but the truth is all the best designs are already out there. So, it's going to be quite difficult to come up with something really new and innovative. In fact, I just looked at the link for the "Uffa Fox's Flying Fifteen" and was amazed how much my design resembles it. But, that's okay, this project is not just about designing a sailboat. It really is an experiment to some degree. There's no doubt that using materials that actually grow in my back yard is a bit unorthodox. However, I'm very confident, with a little time and careful attention to details, I'll build a fine quality vessel.

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    Default Re: Designing a Sailboat

    I considered building an Interlake, but never did.
    It may be something you'd like to check out.
    https://interlakesailing.org/resourc...pecifications/

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    Default Re: Designing a Sailboat

    Quote Originally Posted by Robert D View Post
    That is actually a very good point that I've been thinking heavily on. I would really like a retractable keel and I'd like to give some substantial weight to it. However, the idea of a mechanical lift system is not desirable in this case. I mean, I'd really like to lift it manually. I have some ideas for it, but still it would be a bit of a strain even with two good strong arms. I may have no choice but to build a mechanical lift system. I don't know, it's really not a very big boat and perhaps reducing the sail area is the best course of action. Having said that, my original goal was to sail a sleek little dinghy in light winds on the lakes of North Georgia. I guess there's still a lot of considerations to go through.
    I've seen a set-up with a dagger board case and a dagger board which has a substantial torpedo shaped cast weight.

    This was permanently down while sailing and lifted by using the mainsheet tackle with the boom supported by the crutch - giving shallow draught for launch and recovery but substantial righting moment when sailing.

    See the J70 for a current production version of the idea.
    Last edited by P.I. Stazzer-Newt; 10-30-2022 at 01:14 PM.
    I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

  12. #47
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    Default Re: Designing a Sailboat

    Quote Originally Posted by W Grabow View Post
    Robert,
    From what I am reading, you have put some time into designing this boat, and you have a good background in woodworking. If you enjoy the design aspect of such a project, I will say, "Go for it." When following someone else's plans, at each decision point those plans will give you guidance. When self-designed, you need to stop often and decide which alternative to use for each design detail.

    Sail area: You know what kind of wind that is expected, but also listen to advice. Hemlock: I recently completed a table built entirely of Hemlock; a nice wood to work with. If the wood will be entirely encapsulated, then you should have no problems.

    Over the years, I have designed and built eleven boats, only one of which I would call a failure. That failure was due to having too many design goals. Better to concentrate on having a boat designed for one major purpose.

    developable-surface-boat-designs.blogspot.com
    Hey W Grabow,

    Thank you for the encouragement! I really appreciate it.

    Funny you should mention "someone else's plans". I really tried to go that route. I started researching sailboat design plans back in January of this year when I had COVID. Set me back for 3 weeks, so I had lots of time to do some online reading. Anyway, bought a few study plans, and a few books, and even bought a complete set of plans from GLEN-L, which is actually a real fine looking 15' sloop. However, after studying those plans, reading the books, and reading a fair amount of material online, I decided I would go out on a very long narrow limb and design one myself.

    My goal was a simple one. Build a sailboat that is light, strong, easy to trailer, have as little rigging as possible, (hence, freestanding mast) and be a simple design. Believe you me, I knew I had some challenges ahead of me, even with just the rudder design alone. Not to mention the mast, which is to be made of wood as well. But, it will be of a hollow design to reduce weight and my plan was to taper it as well. Still, this is going to require a technique that I'm not familiar with. The dagger board is a bit of a perplexing issue too. I'm sure I want to design it as a retractable system, but I'm not really wanting to go with a lift mechanism. But, as I've already said, I may have no choice. There are other design considerations as well, and just as you have said, I will have to "...stop often and decide which alternative to use for each design detail" Well, believe or not, that's actually the part I'm looking forward to. For me, it's all about the doing. The "journey" as they say. You could give me a set of house plans for a $10,000,000.00 home and I promise you it would be built just as stated on those plans, with a few exceptions of course. I could do the same with someone else's sailboat plans as well. Nothing wrong with that, I just wanted to challenge myself, but more importantly, I really thought it would be a good idea to design a boat for the area to which I live. Still, it may be a fine sailboat on the Indian River in Sebastian Florida. Maybe even the west coast and panhandle of Florida. With a retractable keel and large sail area I could sail in shallow waters on light winded days and do a little fishing too.

    So, in a nut shell, it is the design itself that I was hoping to get help with, which is why I'm here at this forum. So far, it's been hard to get past the whole Hemlock thing. However, to be fair, a lot of you are in agreement that as long as it is encapsulated in fiberglass, it is an acceptable core material. It really was my plan to build it that way from the get-go.

    What I'd really like to do here is get you opinions on the design/shape itself and perhaps some design suggestions on items like, rudder, dagger board, and mast. Now I do realize it's pretty hard for any of you to comment on something you can't see. But, believe me, I cannot figure out how to get anything uploaded to this website/forum. I have tried to the best of my ability, and it just ain't happen'.

    Well, I seem to be going on a long rant again. But, I did just get an idea. If anyone wants me to email the PDF drawings to them, just let me know. And just to help things out, here's is my email address... robertscandr@gmail.com

    Have a Great Today!

  13. #48
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    Default Re: Designing a Sailboat

    Robert, an interesting project, I look forward to following it.

    Maybe you can put your sketches in a dropbox and post a link.

    A lot of others have chimed in, but my gut reaction is that you are proposing a lot of sail area for a fairly narrow boat. The hull may not be able to stand up to such a large rig, and being somewhat narrow, may not need so much sail to be driven in the light airs at your lake. What are other people sailing on this lake?

    Is the rig unstayed? The hull may be narrow for an adequate stay angle.

    I suppose if you like the hull you can cut down the rig if it proves to be overcanvassed.

    I'd also be concerned that the 1/4" core is thin. It sounds like you are planning strip composite construction (a strip built core covered inside and out with cloth/resin). I am probably oversimplying, but the strength of this construction comes from the cloth and resin, and the stiffness comes from the wood core, which depends on the inherent stiffness of the wood as well as its thickness. I've seen the engineering principle of this construction method compared to an I-beam. While 1/4" might work for a canoe or kayak, those craft do not have to withstand the stresses of a sailing rig.

    If you haven't already found this resource, check out the West System/Gougeon Brothers book on wood epoxy composite boat building, there is an entire chapter on this construction method and also discussion of the engineering principles of cored construction. It's available for free on the West System web site.

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    Default Re: Designing a Sailboat

    Quote by.
    (J. E. Hardiman)
    Naval Architect P.E. (retired)
    This quote was stolen, slightly damaged, and some parts omitted.
    "Just build it because there is no single absolute correct answer, never will be. That is why it is Naval ARTchitecture, no correct answers, only better compromises. Your structural analysis, building skill, and weight management as well as the sailmaker's skill and your sailing ability will have more effect on boat speed and safety than which method you chose to calculate drag....the vessel will go as fast as it goes as permitted by wind and seaway.
    FWIW, if you are really worried about losing the vessel to weather, don't build it and don't sail. The only totally safe boat is the one never built and the only risk free sail is the one never taken. "


    Quote by:
    (…mile-Auguste Chartier)

    "Every boat is copied from another boat... Letís reason as follows in the manner of Darwin. It is clear that a very badly made boat will end up at the bottom after one or two voyages, and thus never be copied... One could then say, with complete rigor, that it is the sea herself who fashions the boats, choosing those which function and destroying the others."
    I think this sounds cleaver but not true for the modern designer.
    "We prove what we want to prove, and the real difficulty is to know what we want to prove."

    Another Quote I ripped off and broke from:
    (Daniel Dennett)

    "Darwin science of evolution is a free floating rational a bubble up methodology of design. If instead we use empirical data with peer review this is a trickle down method of design a hierarchy system of checks and balances.
    Darwin science of evolution is a free floating rational a bubble up methodology of design from the 1800ís"

    A Naval Architecture methodology is one that uses empirical data with peer review this is a trickle down method of design a hierarchy system of checks and balances. They would charge for a particular outcome speed...etc.

    I think that the truth for us amateur designer/builder lays somewhere in between these quotes.

    Last edited by John Howland; 10-30-2022 at 04:07 PM.
    John H.

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    Default Re: Designing a Sailboat

    I think you might usefully delve into calculations for the strength required from an unstayed mast to support that amount of sail.It could well be that the weight of the mast would be rather a lot and would further add to the obstacles to be overcome.Which leads to the amount of structure required to hold the hull in shape and on it goes.Each and every decision,or choice,has consequences.A lifting,ballasted daggerboard is something that has been done-the Laser SB3 has such a system-but keep in mind that the weight of the ballast reduces the ease with which the boat can be handled ashore and the ballast doesn't contribute too much to stability until the boat is heeling considerably.

  16. #51
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    Default Re: Designing a Sailboat

    Quote Originally Posted by Robert D View Post

    I'm a "think outside the box" kind of guy, and perhaps I do go a little overboard with my ideas.
    Quote Originally Posted by Robert D View Post

    For me, it's all about the doing. The "journey" as they say.
    Good on you Robert, you're a man after my own heart.
    Enjoy the "journey"... nothing ventured, nothing gained.
    Best of luck to you.

    Cheers,
    Mike.

    Quote Originally Posted by John Howland View Post
    Quote by.
    (J. E. Hardiman)
    Naval Architect P.E. (retired)
    This quote was stolen, slightly damaged, and some parts omitted.
    "Just build it because there is no single absolute correct answer, never will be. That is why it is Naval ARTchitecture, no correct answers, only better compromises. Your structural analysis, building skill, and weight management as well as the sailmaker's skill and your sailing ability will have more effect on boat speed and safety than which method you chose to calculate drag....the vessel will go as fast as it goes as permitted by wind and seaway.
    FWIW, if you are really worried about losing the vessel to weather, don't build it and don't sail. The only totally safe boat is the one never built and the only risk free sail is the one never taken. "
    Love it.
    I'm going to print this out, frame it and hang it on the workshop wall.
    Focus on the effort not the outcome.

    "Don't take life seriously. Either way, you won't make it out alive."

  17. #52
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    Default Re: Designing a Sailboat

    Quote Originally Posted by wizbang 13 View Post
    cuz there are so many good balsa core boats sailin around.
    or boatyards that are infected with waterlogged balsa wood boats
    yes, hemlock is just as good as balsa
    There are enough, you just don't here of them because there's nothing to tell. There may be more of the waterlogged ones, but it's always related to poor construction practice and/or owners drilling holes into the core without sealing it properly.
    But, you already know that.

  18. #53
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    Default Re: Designing a Sailboat

    Quote Originally Posted by Robert D View Post
    Hey Rumars,

    That was my thought exactly, to encapsulate the core in fiberglass epoxy. However, the amount you are suggesting sounds like it will make the boat very heavy. I've not done the math yet, so I could be wrong about that.

    As for Black Locust, I was considering building the rudder and dagger board with it. Still, I thought it would be best to seal it with something. I thought perhaps Dura-Lux Marine spar varnish. Also build the cockpit sole with it as well. But, for it to be removable for easy cleaning of the actual fiberglass cockpit. In other words, the black locust sole would be more of a wood grate and in a way just for looks. I know that sounds kind of a redundant procedure, but like I said, I'm a "think outside the box" kind of guy, and perhaps I do go a little overboard with my ideas.

    Thoughts?
    I didn't suggest anything, I just translated your propsed layup of 2x4oz CSM. As I said, CSM weight is by the square foot and all other fabrics are by the square yard. 3/4oz CSM weighs more then 6oz plain woven fabric, since there are 9 sqft into a sqyd.

    If i had to suggest anything I would say 12oz biax followed by 6oz plain/twill cloth inside and out. Add more plain underwater if abrasion is a concern. I would prefer thicker strips then 1/4, but stiffness can be managed with bulkheads/frames.

  19. #54
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    Default Re: Designing a Sailboat

    Robert-
    A good journey in a boat should include floating and staying upright for its entirety.
    This requires that the designer have a basic understanding of boat design.
    We’ve given you the syllabus.

    More on CSM-
    The weight of Chopped Strand Mat is measured in ounces per square foot. The weight of other fiberglass goods is measured in ounces per square yard, so 6 oz. glass cloth weighs about 0.7 oz./ft^2. If applying glass cloth with epoxy, the weight of the epoxy will be about the same as the cloth, so a square foot of 6 oz. applied glass cloth will weigh about 1.5 oz. Chopped Strand Mat soaks up lots of resin, at least 1-1/2 times the weight of the glass, so a square foot of CSM will weigh about 10 oz. It’ll be lumpy, so add something for fairing. 100 ft^2 of CSM vs. 6 oz glass will add over fifty pounds to your boat. Arithmetic is cruel.

    As a bonus, CSM is intended for use with polyester or vinylester resins and the binder used in CSM only becomes pliable using those resins. If applied with epoxy, it’ll lie flat only on gentle curves.
    Last edited by JimConlin; 10-30-2022 at 06:34 PM.

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    Default Re: Designing a Sailboat

    McMullen?

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    Default Re: Designing a Sailboat

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    I've seen a set-up with a dagger board case and a dagger board which has a substantial torpedo shaped cast weight.

    This was permanently down while sailing and lifted by using the mainsheet tackle with the boom supported by the crutch - giving shallow draught for launch and recovery but substantial righting moment when sailing.

    See the J70 for a current production version of the idea.
    Interesting idea Sir!

    I have seen the torpedo shape you're referring to. That just might be the way to go.

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    Default Re: Designing a Sailboat

    Quote Originally Posted by JimConlin View Post
    Robert-
    A good journey in a boat should include floating and staying upright for its entirety.
    This requires that the designer have a basic understanding of boat design.
    Weíve given you the syllabus.

    More on CSM-
    The weight of Chopped Strand Mat is measured in ounces per square foot. The weight of other fiberglass goods is measured in ounces per square yard, so 6 oz. glass cloth weighs about 0.7 oz./ft^2. If applying glass cloth with epoxy, the weight of the epoxy will be about the same as the cloth, so a square foot of 6 oz. applied glass cloth will weigh about 1.5 oz. Chopped Strand Mat soaks up lots of resin, at least 1-1/2 times the weight of the glass, so a square foot of CSM will weigh about 10 oz. Itíll be lumpy, so add something for fairing. 100 ft^2 of CSM vs. 6 oz glass will add over fifty pounds to your boat. Arithmetic is cruel.

    As a bonus, CSM is intended for use with polyester or vinylester resins and the binder used in CSM only becomes pliable using those resins. If applied with epoxy, itíll lie flat only on gentle curves.
    Jim, there is no doubt I'm in need of more study. You may have heard the old saying "Some study shows the need for more". Kind of fits me to a "T"

    As for CSM, I really like the way it forms to surfaces. However, I've never played around with biaxial cloth. I probably need to experiment with some. I just started an experiment with a piece of Hemlock and applied a layer of 1.5 oz CSM with Silmar 249. More curious than anything.

    Having said that, I hadn't given any thought to the difference in weight between the epoxy and CSM. I believe it would be appropriate to experiment with a piece of Hemlock and epoxy as well. I've got a gallon of that on the shelf.

    Thanks for the info about that!

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    Default Re: Designing a Sailboat

    Quote Originally Posted by Rumars View Post
    I didn't suggest anything, I just translated your propsed layup of 2x4oz CSM. As I said, CSM weight is by the square foot and all other fabrics are by the square yard. 3/4oz CSM weighs more then 6oz plain woven fabric, since there are 9 sqft into a sqyd.

    If i had to suggest anything I would say 12oz biax followed by 6oz plain/twill cloth inside and out. Add more plain underwater if abrasion is a concern. I would prefer thicker strips then 1/4, but stiffness can be managed with bulkheads/frames.
    I just realized I may have got my quotes mixed up. Sorry about that...

    I'm definitely going to get some Biaxial cloth and do some experimenting.

    Thank you for the clarification Sir!

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    Default Re: Designing a Sailboat

    Quote Originally Posted by Mike1902 View Post
    Good on you Robert, you're a man after my own heart.
    Enjoy the "journey"... nothing ventured, nothing gained.
    Best of luck to you.

    Cheers,
    Mike.



    Love it.
    I'm going to print this out, frame it and hang it on the workshop wall.
    Hey Mike,

    Thanks for the encouraging words!

    I'm going to give it my best, that you can count on!

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    Default Re: Designing a Sailboat

    Quote Originally Posted by John Howland View Post
    Quote by.
    (J. E. Hardiman)
    Naval Architect P.E. (retired)
    This quote was stolen, slightly damaged, and some parts omitted.
    "Just build it because there is no single absolute correct answer, never will be. That is why it is Naval ARTchitecture, no correct answers, only better compromises. Your structural analysis, building skill, and weight management as well as the sailmaker's skill and your sailing ability will have more effect on boat speed and safety than which method you chose to calculate drag....the vessel will go as fast as it goes as permitted by wind and seaway.
    FWIW, if you are really worried about losing the vessel to weather, don't build it and don't sail. The only totally safe boat is the one never built and the only risk free sail is the one never taken. "


    Quote by:
    (…mile-Auguste Chartier)

    "Every boat is copied from another boat... Letís reason as follows in the manner of Darwin. It is clear that a very badly made boat will end up at the bottom after one or two voyages, and thus never be copied... One could then say, with complete rigor, that it is the sea herself who fashions the boats, choosing those which function and destroying the others."
    I think this sounds cleaver but not true for the modern designer.
    "We prove what we want to prove, and the real difficulty is to know what we want to prove."

    Another Quote I ripped off and broke from:
    (Daniel Dennett)

    "Darwin science of evolution is a free floating rational a bubble up methodology of design. If instead we use empirical data with peer review this is a trickle down method of design a hierarchy system of checks and balances.
    Darwin science of evolution is a free floating rational a bubble up methodology of design from the 1800ís"

    A Naval Architecture methodology is one that uses empirical data with peer review this is a trickle down method of design a hierarchy system of checks and balances. They would charge for a particular outcome speed...etc.

    I think that the truth for us amateur designer/builder lays somewhere in between these quotes.

    Well said John!

    Now you got me thinking... I wonder if I can prove what I want to prove? Doesn't matter I guess, I'm going to try anyway!

  26. #61
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    Default Re: Designing a Sailboat

    You can stand on the shoulders of giants and make your own design or an inspired by. Then just go sailing.
    Most of all have fun and Don't breath the foul air.
    Last edited by John Howland; 10-31-2022 at 10:44 AM.
    John H.

  27. #62
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    Default Re: Designing a Sailboat

    Welcome to the forum! I look forward to following along with your build.
    At the risk of seeming more negative than I feel, I will add my voice to the concerned chorus. It seems to me that any design should start with a more thorough brief than I've seen here. Some of the deliberation above concerns exceedingly small-scale issues. I think you should enumerate exactly what you want your boat to be able to do before you worry about the type of fiberglass you apply. You might be better served if you can tell the community more of the following:

    Where will the boat be used? Is that local lake the only destination, or will you take it further afield?

    What conditions to you expect to encounter?

    What conditions do you intend to design for?

    Trailer sailed or stored on the water?

    How many crew?

    Will you ever sail with young / aged / inexperienced / potentially uncomfortable crew?

    Will you ever hand the boat over to anyone else?

    How important is not capsizing? Will everyone always be ready for immersion, or do you need a design that keeps the mast pointing up more often than not?

    Is self-rescue required after a capsize?

    Will you ever beach the boat?

    Do you intend multi-day cruises?

    Do you intend to sleep aboard?

    Will you ever race? Against whom? How is that class regulated/ handicapped?

    And so on

    My not-particularly experienced mind reads your numbers and imagines a demanding white-knuckle sled that might spend as much time on its side as it does upright. But I've never designed a boat, so take that with a big grain of salt.
    Just be aware that the seabed is littered with cautionary tales: "I spent three years on the design of this. I've looked at thousands and thousands of yachts."





    - James
    Last edited by pez_leon; 10-31-2022 at 02:46 PM.

  28. #63
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    Default Re: Designing a Sailboat

    Here are Robert’s drawings. Sorry about the extra lines, that’s on me. I’ll see about getting them off here later.

    35EFECA7-D208-47E9-8C6D-E62CD791D5D2.jpg
    5E698405-27E7-43F0-98A3-9D6E329B9CFA.jpg
    8B022457-9F6F-404F-9E98-8AFDC4AC56C3.jpg
    "Yeah, well, that's just, like your opinion man"
    -The Dude-

  29. #64
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    Default Re: Designing a Sailboat

    Quote Originally Posted by Hwyl View Post
    McMullen?
    I did wonder if there was a sub-genius link....

    The initial drawing ,recently posted, shows an unfeasible amount of roach on the sail and looks really skinny.The vertical topsides aren't really necessary with the freedom to shape a strip planked hull to give any desired characteristics.A few more iterations may be in order.

  30. #65
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    Oct 2022
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    Wink Re: Designing a Sailboat

    Thank you Matt!

    I don't know how you did it, but I'm grateful.

    Well folks, as you can see, all these drawings are at best, is an outline of an idea. I plan on really getting into the nitty gritty details, but it's going to take some time.

    My idea was to be able to sit on the deck with a tiller in one hand and the main sheet line in the other and not have to worry about anything else. Having said that, I was planning on a boom vang, so I'd have to pay attention to that now and then. Also, with a retractable daggerboard/keel, I may have to make adjustments depending on the depth of the water.

    To answer some of pez_leon's questions...

    Lake Lanier is the largest lake in Georgia and has quite a bit of open water. However, I'd love to sail her in the shallow waters off the west coast of Florida, which is one of my favorite fishing spots. Or the Indian River on the east coast of Florida. So, it will be a trailer-able boat. As for conditions, heck, I don't know. I guess I'd like to sail in 15 knots winds for the fun of it. But, cruising along at 5 MPH would be quite relaxing. If I knew I was going out on a very windy day I might invite a couple of friends, just to keep her at a reasonable list, not to mention the fun it would be for a few sailors to really feel the spray in your face! Still, I was planning on having the sail maker incorporate 2 reef points, just in case I wanted fly alone. As for capsizing, I've actually put some thought into that. There are a number of ways to deal with it. One is to have some substantial weight to the retractable keel, which is probably the way I will go. This type of design should be adequate as an almost self-righter. Also, I thought it might be a good idea to incorporate some floatation material of some kind at the perimeter of the deck under the gunwale. If done correctly, the boat could never sink. But, since I plan on an open transom, with water tight compartments, that's not likely to happen anyway. Of course, strange things can happen and having floatation material built in would give me a good piece of mind. I can see where there may be a time or two when she gets beached. But, that would probably be just to take a break or have some lunch. As for racing, well that sounds like fun. However, I've got no idea what class, if any, this boat would be rated at. I doubt I'll ever sleep on this vessel. Well, unless the wife kicks me out one night, but then it would be on the trailer and I wouldn't have to worry about going a adrift...

  31. #66
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    Oct 2022
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    Default Re: Designing a Sailboat

    Quote Originally Posted by John Meachen View Post
    I did wonder if there was a sub-genius link....

    The initial drawing ,recently posted, shows an unfeasible amount of roach on the sail and looks really skinny.The vertical topsides aren't really necessary with the freedom to shape a strip planked hull to give any desired characteristics.A few more iterations may be in order.
    Hey John,

    Thank you for your input.

    I should say straightaway, that I'm not familiar with some of the terminology of sail configuration. But, if "Roach" is what I vaguely think it is, might not a properly designed sail with well thought out placement of battens create the proper sail shape while under load?

  32. #67
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    Default Re: Designing a Sailboat

    Quote Originally Posted by John Meachen View Post
    I think you might usefully delve into calculations for the strength required from an unstayed mast to support that amount of sail.It could well be that the weight of the mast would be rather a lot and would further add to the obstacles to be overcome.Which leads to the amount of structure required to hold the hull in shape and on it goes.Each and every decision,or choice,has consequences.A lifting,ballasted daggerboard is something that has been done-the Laser SB3 has such a system-but keep in mind that the weight of the ballast reduces the ease with which the boat can be handled ashore and the ballast doesn't contribute too much to stability until the boat is heeling considerably.
    Hey John,

    Seems I missed this post a couple of days ago.

    Well, you've mentioned so many details to think about my head is spinning...

    All good stuff though, and you're right, I need to consider all the aspects involved in this design. I may have to make more adjustments than I really want to, but heck, that's what designing is all about. Working out the kinks before one nail is driven. Been doing it with custom homes for years, no reason why that same perspective can't be applied to sailboat building. Which means of course, It's gonna be a while before I even get started on the first strip plank.

    So, I just looked at the Laser SB3. I guess, inadvertently that is, I've been inspired by that design. I've sailed lasers, but I've never seen that one before. Well, to be honest, since I moved to Georgia in 1995, I've been a little out of touch with sailboats. It's just been recently my sailing interest has been rekindled, so to speak. But, I remember my sailing days very well, and I'm really looking forward to getting back to it.

    Anyway, looks like I need to do some math. I'm also going to perform a few experiments. I'll try to post some pics of those experiments as I go along.

    Thanks to all once again!

    Have a Great Today!

  33. #68
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    488

    Default Re: Designing a Sailboat

    "Build a sailboat that is light, strong, easy to trailer, have as little rigging as possible, (hence, freestanding mast) and be a simple design." - OP
    Look at the Goat Island Skiff

  34. #69
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    Oct 2009
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    NW Georgia
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    Default Re: Designing a Sailboat

    Quote Originally Posted by gray duck View Post
    "Build a sailboat that is light, strong, easy to trailer, have as little rigging as possible, (hence, freestanding mast) and be a simple design." - OP
    Look at the Goat Island Skiff
    Or the Calendar Islands Yawl 16 which was my choice. It's a lapstrake "version" of the GIS. I'm so excited to be near the end of my build.

    However, I believe Robert is enjoying the process. I designed my first build but it was a simple 7-1/2' sailing dinghy. I basically looked at dinghies, made a cardstock model, scaled up the model and built my dinghy. S&G, hard-chined: Not too many places to go wrong, though there were some things I would have changed if I built that same dinghy again. I enjoyed the process and satisfaction of "designing" my own boat. If I had it to do over again though, I'd probably spring for the $40 and buy plans. Later builds, which have been bigger boats, no way was I going to try and design my own. Too many good choices and too much at stake for me.

    Robert, be careful, be smart and have fun. As an earlier comment stated - you really don't want to spend $k's and hundreds of hours on a dud.

  35. #70
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    Default Re: Designing a Sailboat

    Quote Originally Posted by gray duck View Post
    "Build a sailboat that is light, strong, easy to trailer, have as little rigging as possible, (hence, freestanding mast) and be a simple design." - OP
    Look at the Goat Island Skiff
    Hey gray duck,

    I really like the look of that boat. However, I'm wanting to design a sailboat with an open transom. I'll admit though, the Goat Island Skiff has a real classic look about it and I'm sure I'd enjoy sailing it.

    Thanks for your input!

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