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Thread: Improving light air performance on Atkin's Mink

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    Question Improving light air performance on Atkin's Mink

    Hi everyone,

    I'm considering to build a William Atkin's design called Mink (http://www.atkinboatplans.com/Sail/Mink.html). It is a 30ft heavy displacement cruiser, kind of similar to a Tahiti Ketch. One of my desires is to sail it mostly engineless (with a small electric motor just to help maneuvering during docking operations). However, the original sail plan seems to be very under canvassed. Taking the specifications provided on the plans, (+-18k lbs D, 482 sqft SA) gives a SA/D of ~11.26.

    Do you think the sail plan can be modified to improve light air performance? If so, what would you suggest?

    One thing that is also important is to keep the traditional aspect of the rig.

    I was thinking about something around 700sqft total, with a lower peaked and longer gaff, a topsail, and a relatively large jib on a bowsprit. Something similar to the sail plan used on the Curlew Falmouth Quay Punt of Tim and Pauline Carr:
    curlew1.jpg

    I know that this will raise the CE, though maybe this will be compensated by some changes that I plan to make to the build itself. The original plan calls for outside iron ballast with almost the same amount of inside ballast (I plan to make the outside ballast of lead, thus lowering the CG of the boat). I'll probably make the mast hollow. I'll remove the 80 gallons fuel tank that is positioned high up near the cockpit. And probably more weight will be saved on the deck by building the boat in composite manner (strip-planked core, sheathed with fiberglass inside/outside).

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    Default Re: Improving light air performance on Atkin's Mink

    8 tonnes for a 9m boat???

    Why???

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    Default Re: Improving light air performance on Atkin's Mink


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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by luckystrike118 View Post
    8 tonnes for a 9m boat???

    Why???
    Comfort, economy, safety

    But I feel the WHY when it comes to "a small electric engine ,for entering harbors".
    Dreaming of environmental goodness? dunno.
    Engine only has to save the boat and its crew ONE time to pay for itself.
    With a strong diesel, someday you can even save others !!
    Last edited by wizbang 13; 08-26-2020 at 08:13 AM.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by luckystrike118 View Post
    8 tonnes for a 9m boat???

    Why???
    I think just like these kind of boats. The comfortable motion, the looks, the seaworthiness, etc.
    A modern light displacement boat, like Dudley Dix's MG 30, might be fun to race or cruise in light weather, but I just don't like how these modern boats look and I wouldn't want to be in one during heavy weather.
    I would say that it is almost like owning a classic car, though it is really different. A heavy displacement traditional boat is much safer to be in than most modern light displacement boats (unlike old cars vs new), and they look much better (to my taste anyway )

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by wizbang 13 View Post
    But I feel the WHY when it comes to "a small electric engine ,for entering harbors".
    Well, it is not a definitive decision yet. The reasoning behind it is mostly the desire to eliminate the smell of diesel, the noise, and the heat associated with a combustion engine.

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    Default Re: Improving light air performance on Atkin's Mink

    I dunno...there is something about the smell of coffee brewing, the faintest whiff of propane from lighting the stove, just a hint of diesel in the background, the salty, stuffy smell of old cushions and weather battered Sunbrella....

    Ive more than once been happy to set the hook, peel off the foulies and hop in the quarter berth with my back to the engine box for a little warm up

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by amendoim View Post
    I think just like these kind of boats. The comfortable motion, the looks, the seaworthiness, etc.
    A modern light displacement boat, like Dudley Dix's MG 30, might be fun to race or cruise in light weather, but I just don't like how these modern boats look and I wouldn't want to be in one during heavy weather.
    I would say that it is almost like owning a classic car, though it is really different. A heavy displacement traditional boat is much safer to be in than most modern light displacement boats (unlike old cars vs new), and they look much better (to my taste anyway )
    Where's the evidence for that claim about seaworthiness?

    How many times would you have to have a traditional boat very close to a modern boat in the same heavy conditions to prove which one was safer than the other?

    If the traditional types are so much safer when you put them close to modern boats in the same bad weather, why did traditional boats have by far the worst loss record in the '98 Sydney-Hobart, for example?

    Given the extremely high percentage of boats of all reasonable types that complete ocean voyages (including beachcats and windsurfers) how can one isolate one type as being more seaworthy than another? Sure, there are theories about seaworthiness, but arguably many of them just concentrate on factors that are not statistically significant when it comes to the number and proportion of actual losses.

    If a traditional boat just makes your heart sing then that's great, and good on you for getting one. But stating as a fact that they are "much safer" does not appear to follow the statistical evidence.

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    Default Re: Improving light air performance on Atkin's Mink

    I can't say which is safer. I own a 39' ketch, 32,000#, my friend sails a much more modern 36' sloop 11,000#. I've sailed with him, his boat points high and sails fast in a light breeze. He sailed with me down the coast a couple of hundred miles and had two comments: That my boat was faster than he expected and that he couldn't believe how comfortable she was in a sea. I've been bounced around enough, I prefer a heavy boat for weather. If I had a light boat, I might go farther between blows. Each has it's advantages.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by Chris249 View Post
    Where's the evidence for that claim about seaworthiness?

    How many times would you have to have a traditional boat very close to a modern boat in the same heavy conditions to prove which one was safer than the other?

    If the traditional types are so much safer when you put them close to modern boats in the same bad weather, why did traditional boats have by far the worst loss record in the '98 Sydney-Hobart, for example?

    Given the extremely high percentage of boats of all reasonable types that complete ocean voyages (including beachcats and windsurfers) how can one isolate one type as being more seaworthy than another? Sure, there are theories about seaworthiness, but arguably many of them just concentrate on factors that are not statistically significant when it comes to the number and proportion of actual losses.

    If a traditional boat just makes your heart sing then that's great, and good on you for getting one. But stating as a fact that they are "much safer" does not appear to follow the statistical evidence.
    I probably used the wrong word to describe my intent. There are so many variables in this equation, not all related only to the boat itself, that it seems hard to judge what type of boat is better.

    I apologise for making such a vague claim.

    I'm mostly referring to things like the way the boat moves and how this can impact the crew, which is closely related to the seaworthiness of the boat.

    I know that from a technical standpoint it is perfectly possible (and probable) to make a boat ultralight that is better able to take on bad weather than some older models. After all, it it wasnt, the guys racing single handed around the world would be using replicas of Suhaili and not ultrafast, ultralight, carbon (space?)ships that almost fly over the ocean. However, these guys are athletes, and I would probably be dead trying to keep up with what those guys have to do to keep on sailing I guess that, in my case, it is safer to be in a slower, heavier and more sedate boat.

    Anyways, thanks for your contribution

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    Default Re: Improving light air performance on Atkin's Mink

    Heavy double enders cannot outrun bad weather,so they stay in the ring and take licks.
    Modern raceboats used for cruising can, and Do, run from the sh!t.
    As far as boats "surviving" a race....slow down if yer in a full keel boat...that IS the plan.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by wizbang 13 View Post
    Modern raceboats used for cruising can, and Do, run from the sh!t.
    Yeah, but one cant load them up with cruising stuff, I guess. Unless it is a really big one, not a 30ft one.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by amendoim View Post
    Yeah, but one cant load them up with cruising stuff, I guess. Unless it is a really big one, not a 30ft one.
    I have never heard of a "modern" boat actually breaking up from overloading, but have seen a few so heavily laden that they dragged their transoms, which did reduce their normal speed. A typical French "First 30" weighs 3.5 ton with a max displacement given a little over 4 ton.....not much load capacity in the way of "stuff". On the other hand, a 30ft Tahiti ketch displacement is given as double that at 8.1 tons. I know which one will have more space and comfort, but will also be slower in light winds. A boat that actually sails really well is a wonderfull thing, but that performance generally gets worse as stuff gets loaded on for live-aboard or passage making. Your own priorities will dictate what works best for you.
    I might think about adding some bilge keels on Mink to slow the rolling down, her sections are pretty barrel shaped.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by Flobart View Post
    I have never heard of a "modern" boat actually breaking up from overloading, but have seen a few so heavily laden that they dragged their transoms, which did reduce their normal speed. A typical French "First 30" weighs 3.5 ton with a max displacement given a little over 4 ton.....not much load capacity in the way of "stuff". On the other hand, a 30ft Tahiti ketch displacement is given as double that at 8.1 tons. I know which one will have more space and comfort, but will also be slower in light winds. A boat that actually sails really well is a wonderfull thing, but that performance generally gets worse as stuff gets loaded on for live-aboard or passage making. Your own priorities will dictate what works best for you.
    I might think about adding some bilge keels on Mink to slow the rolling down, her sections are pretty barrel shaped.
    This is exactly what I was referring to. It is not that the light cruiser will break up, it will just slow down (by how much? I dont know) if you load it up, as the D/L ratio will increase faster than with a heavy displacement boat (and then maybe it will be as slow as a heavy sailboat in light winds?). As you put it, it is a question of defining your priorities and selecting the vessel accordingly.

    I've read about a guy (forgot his name) that made some mods to a Westsail 32 that improved the performance considerably, even winning a transpacific race (if I remember right) with it.

    I don't know about using bilge keels. Besides reduce rolling, wouldn't it just add drag? Sometimes I wonder about using a deeper keel, but then it would probably be better to upgrade the plans to an Atkin Clione/Maytime or a Venus Ketch instead of risking screwing up the original design.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by amendoim View Post
    I don't know about using bilge keels. Besides reduce rolling, wouldn't it just add drag? Sometimes I wonder about using a deeper keel, but then it would probably be better to upgrade the plans to an Atkin Clione/Maytime or a Venus Ketch instead of risking screwing up the original design.
    Many of the original Tahits and others like it just had the sail area increased as the SA/Disp ratios are on the low side to start with. Bilge keels would add drag, but probably less than making the keel deeper. I might add not the kind of bilge keels to make grounding possible, but just big enough to reduce roll.




    Bruce/Whizzbang put up the off-sets for the Venus some years ago (yes i have been lurking that long), but the Atkin plans are pretty cheap if you do not need the advice from the designer. I do like Minks flush decks.

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    Default Re: Improving light air performance on Atkin's Mink

    Here is the secret to light air performance;

    power/drag

    Thats it, build a big heavy tub with a lot of wetted surface and it will be slow in the light, that design is a big heavy tub so the only way you're going to make it sail is add a lot of area. Better of just putting a diesel in and motor, most cruisers do when its below 5kts.

    Electric is not there yet unless you are a nut, its very expensive and if cheap then it has no range.

    The Pardeys sailed their 11 ton 30 footer without an engine around the world, but they also sh!t in a bucket and got towed in and out of places a LOT more than people were led to believe. Point is you dont need an engine if you sail where there's lots of wind and are ok either sculling or begging.
    whatever rocks your boat

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by Flobart View Post
    I do like Minks flush decks.
    Me too. I saw a lovely Tahiti Ketch that was flush decked here at the forum. I think she was called Mellita, but sadly it seems the boat was lost a few years ago.
    Atkin's Thistle and Clione are also very nice, the extra space would be very welcome.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by amendoim View Post
    Me too. I saw a lovely Tahiti Ketch that was flush decked here at the forum. I think she was called Mellita, but sadly it seems the boat was lost a few years ago.
    Atkin's Thistle and Clione are also very nice, the extra space would be very welcome.
    Mellita was owned by a forum member, but i do not recall the name, yes she was lost en-route to Iceland, and a very nice example of a Tahiti. A Thistle would be a nice alternative. I concur with what Paul G says, electric is not quite there yet, but it is interesting to see some cruisers on utube using it, let their experience guide you. Me, i would want a simple small diesel, i would pay extra for a "smart" prop though, something like a Bruntons that would be efficient for low wind motor-sailing and minimal drag for sailing. A Westsail would be an absolute bargain compared to a build, unless you really want the experience.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by Flobart View Post
    A Westsail would be an absolute bargain compared to a build, unless you really want the experience.
    I've yet to hear about a Westsail 32 for sale in Brazil. It is a shame the brazilian law forbids importing used sailboats (you can only buy new boats, paying double the price after you include the taxes and importing fees)
    Most used sailboats around here are the typical GRP 80s or later design.

    So, It seems that if I want a traditional design building it myself its the only option.

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    Default Re: Improving light air performance on Atkin's Mink

    Building a boat is a huge task, if you want to build read on....

    Weight (displacement) is a pretty good guide to the work you will be doing. 8 tons is say 4-5 tons-ish of woodworking, shaping sanding painting. It's a lot.
    What's your budget? Whatever it is start thinking along the lines of 50-100k plus for an ocean ready fully equipped 30 footer
    Do you have the space, time, tools and skill? If not budget for it.
    What you will end up with will be worth about 1/3 of what you put into it and forget about time. The market for double ended trad boats is small.

    If you love the boat and have a passion then go for it but you can buy a lot better than you can build plus you'll be out there next week not in 5-10 years. But some people just love building, its a mighty fine pastime!
    Last edited by Paul G.; 08-29-2020 at 04:03 AM.
    whatever rocks your boat

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by Paul G. View Post
    Building a boat is a huge task, if you want to build read on....

    Weight (displacement) is a pretty good guide to the work you will be doing. 8 tons is say 4-5 tons-ish of woodworking, shaping sanding painting. It's a lot.
    What's your budget? Whatever it is start thinking along the lines of 50-100k plus for an ocean ready fully equipped 30 footer
    Do you have the space, time, tools and skill? If not budget for it.
    What you will end up with will be worth about 1/3 of what you put into it and forget about time. The market for double ended trad boats is small.

    If you love the boat and have a passion then go for it but you can buy a lot better than you can build plus you'll be out there next week not in 5-10 years. But some people just love building, its a mighty fine pastime!
    Hi Paul,

    thank your for your advice. I am aware that building a boat is a huge task and it seems that many projects just end up unfinished. It would be quicker/safer to buy a boat, as you said, though I did not find anything along the lines of what I want (traditional looks - like colin archers, falmouth working boats, etc - heavy displacement, blue water capable, not too large - 30- 35ft). I might just buy one small trailer sailer to do coastal cruising while I build my dream boat at home, as I only expect to have time to actually go cruising offshore a few years down the road. The Pardeys say "go small, go now", but I just can't go now (unless I win the lottery and stop working ).

    I like doing stuff myself. so I'll follow the advice given here on the forum and build the dinghy first (a nice one, not those boxy things lol) This way I'll discover if I have what it takes to build a larger boat, and If I don't, maybe I'll have to conform myself with the plastic racer-cruisers after all.

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    Default Re: Improving light air performance on Atkin's Mink

    " you'll be out there next week not in 5-10 years".

    or 10 months.




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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by wizbang 13 View Post
    " you'll be out there next week not in 5-10 years".

    or 10 months.

    Hey Wiz, not all builders embrace the grinder and the epoxy barrel, if they did then there would be plenty of 10 month builds Round here its housed half dovetails, caulking irons, red lead and arrrgh by gum, which of course translates to anything from 5 to 25 years! There are boats on here that were being worked on when I joined the board, and are STILL in the shed! In olden days wealthy eccentrics use to build things called follys, not a bad way to pass the time but with boats you have to make the decision- are you a builder or a sailor?
    whatever rocks your boat

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    Default Re: Improving light air performance on Atkin's Mink

    Performance:
    Reduce drag. Build a smooth fair bottom and keep it clean. Minimize the hardware and crap that will disturb and disrupt the smooth flow of water over the surface.
    Drag shows up in speed through the water and pointing, both are essential idf you intend to sail where others power.
    Keep the rig simple and clean. Aero drag is about 1/800th of hydro drag, but that doesn't mean it's nothing. Holds onto your mooring line when the wind pipes up and you will get a good idea of the parasitic aerodynamic drag of your boat. The induced drag of the sails creating lift is on top of this. Good sailboats become bad sailboats with a thousand little things that don't matter much but which add up.
    In light air, the critical ratio is Sail Area to Wetted Surface so sail area is your friend. Most often it is going down wind where this is most acutely needed. So big spinnakers or running sails will often get you home against the tide.
    SHC

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    Default Re: Improving light air performance on Atkin's Mink

    There's a giant group of boats between 'slow tubs' and ultralight moderns that perform well and don't slow down vastly when loaded. And comfort or motion is about dead rise or how much 'v ' in the sections. Flatter = harder ride, faster generally. More v or depth in the bow sections, softer ride , probably pitch more , slower.

    The boats i mean have modest overhangs, CCA, RORC ,early IOR maybe and variations on moderate to deep ish deadrise. Mostly pre 80's.
    If there's import protections the local secondhand boat market will be artificially high?
    But have you considered an older boat?
    Last edited by John B; 09-15-2020 at 02:20 PM.

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    Default Re: Improving light air performance on Atkin's Mink

    The Carrs kept their boat in phenominaly clean condition.
    No baggywrinkle kind of things, no lazy jacks...they were faster than the average bermudian boat. Full batten main...performance was their thing.
    I've had so much stuff in the rigging it's crazy.
    All the above, plus radar 'flector or 2,dingy masts on the mizzen shrouds, outside speakers, my sons bicycle tied in the mizz rigging,wood rtlins on both spars,(the mizzen is harder to climb than the main),canvas dodgers, a canvas bimini thing,honda generator on deck, the Monitor...more stuff I forget I'm sure.

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    Default Re: Improving light air performance on Atkin's Mink

    A 58ft double ended ketch, "Kathini" was built to Ed's design in a shed on the beach at Cajaiba that I think is south of Sao Paulo. So it seems there are wooden boat builders around down there.

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    Default Re: Improving light air performance on Atkin's Mink

    I've sailed next to Lark, which is a Curlew clone, she's quick for her size too.
    We've got so much parasitic drag on our boat we get leaflets dropped on board by the rent-o-kill people.

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    Default Re: Improving light air performance on Atkin's Mink

    Quote Originally Posted by luckystrike118 View Post
    8 tonnes for a 9m boat???

    Why???
    If you have a look at the waterplane loading, I think that weight on a boat of that type would be toward the heavier end but still in the right bracket for a comfortable heave rate. Her D/L ratio will be around 350 which is not outrageously heavy and would give a fairly gentle motion.

    John Welsford
    An expert is but a beginner with experience.

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    Default Re: Improving light air performance on Atkin's Mink

    My boat, Truth, was a 30' gaff rigged cutter. She was cold molded which simultaneously saved internal space, and made a light strong hull. She displaced ~8000 empty and had ~4000lb lead in her keel. SA was about 730 sq ft. She moved well even in light airs, and stood up to her canvas, carrying full sail up wind in 15kt true. With the cutter rig, it was easy to balance the helm, and take in the jib when it breezed up, thus having all the sails inboard. Slab reefing also made reefing the main easy. I believe high peaked gaffs are a little more weatherly.

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    Default Re: Improving light air performance on Atkin's Mink

    What David said.
    Topsail philosophy is interesting. Some boats have it as part of their normal sailplan, ie it's the first reef.... some treat it as an extra for light air.
    When I designed and built my rig I wanted the sailplan to be the latter, so I made the gaff peak at about 30 degrees rather than the usual 35 to 40. It meant a smaller topsail but that worked for us and the windward performance was better than when we were bermudan. Pointed as high and sailed faster due to the sail area hammer she'd been hit with.
    We could sail and perform well bald headed but had something else to pull out for classic races and regattas.
    Incidentally, I copied the Carrs interpretation of using the topsail halyard as a jackstay to control the yard heel, worked well. I also made my topsail live on chocks on the boom so it was easier to set , already inside the topping lifts.
    There it is on the boom, lived there the whole time moored or sailing. Love that snap, it got used on a yearbook cover too.
    100-0076_IMG_18.jpg
    Last edited by John B; 09-16-2020 at 03:22 PM.

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