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Thread: Sail Area Differences

  1. #1
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    Default Sail Area Differences

    After many years of deciding which boat to build and waiting for the kids to move out, I have decided to start building the Joel White Marsh Catboat this winter. Now the Marsh Catboat is 15'-0” LOA, with a 6'-11" beam, and a sail area of 152 ft². Another Catboat I heavily debated on was the Sea Gull by Fred Goeller Jr which has the same LOA and beam but a sail area of 216 ft² and the barn door rudder that I prefer. Now the question at hand is this: I live in Missouri and plan to use it in local lakes and rivers mostly but do plan to get her into saltwater at least once. What are the pro/con of the 2 sail areas (152 vs 216)? My thoughts are to build the bigger sail area and add a 2nd reef to get the sail small on windy days. But I'm relatively new to sailing and I could be missing something here. Any thoughts, wisdom, and advice would be greatly appreciated.

  2. #2
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    Default Re: Sail Area Differences

    Putting a different sail rig on an existing design is not trivial. The geometry of the sail determines the location of its “center of effort” which needs to have a specific relationship with the hull and appendages’ “center of lateral resistance”. When the designers drew those two boats, they took care of this relationship for you, the builder. If you change the rig, then you are making yourself responsible for a big part of a successful sailing design.

    It can be done with care, but for a first boat, it seems unnecessary to take that risk. Joel White was a highly respected boat designer. I can’t think of an a priori reason to mistrust the decisions he made. Until you have built the boat as designed, you won’t know it’s strengths or weaknesses either. I say trust your designer until you have lived with the boat and learned otherwise.

    Just my two-cents from reading here and building my first sailboat … to the designers specifications.

    -Neil
    Dreaming of sailing in Iowa, building a Carnell Nutmeg.

  3. #3
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    Default Re: Sail Area Differences

    There are boats so exactly designed that more sail slows them down. I don't think your boat is one, so go with the bigger rig if the hull's shape can stand up to it. Many sailmakers have programs that can predict this.

    When Marmalade got full length battens and more roach, I gained 80 or 90 square feet - 520ish to a bit over 600. The first reef was as much sail as the old full sail and I often sailed her that way.

    It's a bit counter-intuitive but that extra sail up high did not increase heeling by much.

    There are engineering problems: the battens tend to thrust forward around the mast. We were that sailmaker's third shot at a fully battened gaff sail and by then he'd solved it.

    A sail of exceptional authority.

    Make a slab reefing system that can be done hove-to in rough weather.

    G'luck

  4. #4
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    Default Re: Sail Area Differences

    IMO the chances of an amateur improving on a Joel White design are slim at best. Trust his top-notch reputation.
    Last edited by Autonomous; 11-19-2022 at 12:21 AM.
    ​​♦ During times of universal deceit, telling the truth becomes a revolutionary act
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  5. #5
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    Default Re: Sail Area Differences

    What is the displacement difference of the two boats?
    Is was common for catboats to have "summer" and "winter" sails

  6. #6
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    Default Re: Sail Area Differences

    A 40% increase in the sailplan will make the boat more challenging to sail in any wind What’s your skill level?

    I’m guessing that the prevailing wind in your area is light and might consider a minor (15%?) enlargement of the sailplan.
    This will mean longer spars. Do your best to keep them light. Get a qualified designer to do the COE vs. CLR calculations for full sail and reefed conditions.

    If you mess with the sail plan and don’t get the balance just right, a barn door rudder will require more effort than the kick-up rudder Joel drew. In any event, it’ll be less effective when heeled.

  7. #7
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    Default Re: Sail Area Differences

    Isn't the OP choosing between two boats with different sail areas and not putting a different rig to a boat? That's the idea I got from his post.

  8. #8
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    Default Re: Sail Area Differences

    ^^^ That's what I thought, too.

    Tom
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    www.tompamperin.com

  9. #9
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    Default Re: Sail Area Differences

    I also thought the choice was between two boats.
    There may be other differences that merit the larger rig, more displacement for instance. In a daysailer I would always choose more area, as they're generally sailed in lighter winds, and ballast isn't hard to add.

  10. #10
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    Default Re: Sail Area Differences

    I'm reading his post thinking he's taking on the White design ("I have decided to start building the Joel White Marsh Catboat....) but asking whether maybe he can use the larger sail plan from the Goeller (I've looked for but failed to find plans for this craft so far) with a reefing capability added instead ("My thoughts are to build the bigger sail area and add a 2nd reef....).

    In that both designs share length & beam it may appear as a simple question to a relative novice, but my suspicion is that there's more to it.

    Centers of Sail Areas and Centers of Lateral Resistance would also have to be pretty near identical under reefed conditions as well as unreefed for such a swap to be predictable for a skilled sailor.

    For a novice my take is that it'd be a risky proposition.
    Last edited by sp_clark; 11-19-2022 at 08:51 AM.
    They have bartered their birthright for a mess of pottage.

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  11. #11
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    Default Re: Sail Area Differences

    Just some clarifications,
    I am staring to build Joel White's Catboat. Good reputation of the designer, many have been built over the years, highly detailed plans, and it was love at first sight when I sailed on one. The Sea Gull from Fred Goeller, Jr comes from an old Rudder magazine. From what I can see for the most part, they are roughly the same boat. Same type of boat, same LOA, same beam, same draft and displacement. My question is whether bigger is better? I understand that if I went with the larger sail, I would need to follow the location of mast, centerboard size and location, and rudder exactly. If went with the smaller sail to follow White's plans exactly. It comes down to more of a sailing issue rather than a building issue, and my inexperience is why I bring up the question. Looking at wind roses at various places around the state shows roughly about 5% calm, 20% 1-5mph, 35% 5-10mph, 25% 10-15mph, 10%15-20mph, and 5% above 20mph. Am I going to be fighting the sail all the time and lose the point of a relaxing cruise if I went with the larger sail area? Are the winds roughly optimal for the boat as Jim White drew them to be, so I should just let it be and use the smaller sail area? Thank you all for your time and thoughts.

  12. #12
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    Default Re: Sail Area Differences

    m-spangle... Joel White has a solid reputation with many of his designs on the water. How do you know that the Goeller boat, with little known about them, was a good performer? Other than what you can see in their appearance, how do you equate these boats?

    Jeff

  13. #13
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    Default Re: Sail Area Differences

    Ok, so you WERE planning to swap the rig from a different boat. If you are not familiar with defining the center of latelar resistance, center of saila area and how these should be placed in relation to each other, then my advise is don't do it.

  14. #14
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    Default Re: Sail Area Differences

    Obadiah, sail #14, is a Marsh Cat and AFAIK has the stock sail plan. She is a fine sailer. She is a regular at the Mid-Atlantic Small Craft Festival and has undertaken many long camp cruises.

    Don't change a thing.

    "George Washington as a boy
    was ignorant of the commonest
    accomplishments of youth.
    He could not even lie."

    -- Mark Twain

  15. #15
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    Default Re: Sail Area Differences

    In the video, Obadiah looks to have a reef tucked in even in these moderate conditions. I think second-guessing Joel White and adding a LOT more sail area would be a mistake.
    Exactly as you pointed out, you would probably trade a perfectly lovely experience for a white-knuckled, hiked-out hell ride.

    Just my 2 cents, build as the designer intended.

    Good luck!

    Mike

  16. #16
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    Default Re: Sail Area Differences

    Marsh cat has a bowsprit and the mast is not right
    forward. I am guessing the Goeller design a more of a Cape Cod type with the mast way up in the bow. I doubt you can just drop the Goeller rig into Marsh Cat, she isn’t designed for that rig.

  17. #17
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    Default Re: Sail Area Differences

    I always wonder why people want to modify boats that work well, when it is their first effort? If you have plenty of experience in designing and building,then, yes, have some fun on changes.
    Altering established designs needs a lot of knowledge. Anybody caperble of it would not be asking on here.

    If that is a bit harsh, so be it. My current build is different from the designer, but I kept the basic elements the same. And, I grew up by my father's design board, so have a little more experience on it.

  18. #18
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    Default Re: Sail Area Differences

    Agreed 100%. Sometimes reality can be harsh. That's just the way it is.

  19. #19
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    Default Re: Sail Area Differences

    All of the known plans for Goeller’s Sea Gull are published in Boat Design Quarterly #42. They are not to scale. Available from our hosts.
    The scantlings appear to me to be pretty typical construction for the early 1900’s. Cedar planking, finished 5/8”. 1” x 1” oak frames 12” o.c. No specification of spar construction. The main boom is 17’ long!

  20. #20
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    Default Re: Sail Area Differences

    Quote Originally Posted by nrs5000 View Post
    Marsh cat has a bowsprit and the mast is not right
    forward. I am guessing the Goeller design a more of a Cape Cod type with the mast way up in the bow. I doubt you can just drop the Goeller rig into Marsh Cat, she isn’t designed for that rig.
    I stand corrected, maybe -- I have found a couple of articles that identify Obadiah as a Marsh Cat. They are both in the Small Boats online magazine which requires a subscription. In any case, here is a video of Obadiah sailing with Little T and another Marsh Cat.

    "George Washington as a boy
    was ignorant of the commonest
    accomplishments of youth.
    He could not even lie."

    -- Mark Twain

  21. #21
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    Default Re: Sail Area Differences

    Quote Originally Posted by JimConlin View Post
    The main boom is 17’ long!
    On a 15' LOA? Best watch your noggin!

  22. #22
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    Default Re: Sail Area Differences

    From Kevin Macdonald's article on his Marsh Cat " Little T"(6/15 Small Boats Magazine)

    "The Cat likes to sail level and the weather helm is all but eliminated when it is. With a single reef and a slackening of the mainsheet in gusts, it remains docile and in control in winds of about 14 knots. As the wind builds to about 18 knots, it’s time for the second reef. Above 25 knots, it’s time to head for the barn unless you have crew. I’ve sailed my Marsh Cat in the Florida Keys with a competent crew member aboard in 30+ knots of wind with a double reef and both of us—over 500 lbs—hiked out over the rail. In gusts we buried the leeward rail but were still in control and felt no need to return to shore. Beating into the wind, it is common to make 5.25 knots; 6.5 knots running before the wind. "

    Reefed by 14 knots? It just doesn't sound like the hull needs any more sail area than the 152 square feet Joel White drew.
    Steve

    If you would have a good boat, be a good guy when you build her - honest, careful, patient, strong.
    H.A. Calahan

  23. #23
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    Default Re: Sail Area Differences

    Have to say that I did this on a Fen Williams 18' cat. Just lengthend the past a foot or so, left the gaff the same and ran the leech down to determine the foot length. It gave me one of the preengine era rigs. The first reef went in around 8-10 knots of wind It worked great, if there was any wind around I could sail. Never had an engine. Boom overlapped the stern by a bit. The first reef got the sail back to what Fen had designed. Then the next reef went in as normal. However, I did have a little experience. Subsequent owner of my cat put in an engine and shortened the rig to what Fen designed.
    Ben Fuller
    Ran Tan, Liten Kuhling, Tipsy, Tippy, Josef W., Merry Mouth, Imp, Macavity, Look Far, Flash and a quiver of other 'yaks.
    "Bound fast is boatless man."

  24. #24
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    Default Re: Sail Area Differences

    Quote Originally Posted by Ben Fuller View Post
    Have to say that I did this on a Fen Williams 18' cat. Just lengthend the (m)ast a foot or so, left the gaff the same and ran the leech down to determine the foot length....
    Reasonable approach, maybe Fen would agree?

    On an eighteen footer w/~ 260 sq ft sail you added maybe 10% more sail area – down low – with this change.

    Then 1st reef brought it back to original config.

    Quite a bit less risky an approach compared to adding 40+% sail area to a boat some 20% shorter, to say nothing about how CLR/CoE balance would be affected.

  25. #25
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    Default Re: Sail Area Differences

    Quote Originally Posted by sp_clark View Post
    Reasonable approach, maybe Fen would agree?

    On an eighteen footer w/~ 260 sq ft sail you added maybe 10% more sail area – down low – with this change.

    Then 1st reef brought it back to original config.

    Quite a bit less risky an approach compared to adding 40+% sail area to a boat some 20% shorter, to say nothing about how CLR/CoE balance would be affected.
    That was and would be my approach to dealing with increasing traditional area to deal with light air. It worked and I was totally not surprised as it was the traditional approach.
    Ben Fuller
    Ran Tan, Liten Kuhling, Tipsy, Tippy, Josef W., Merry Mouth, Imp, Macavity, Look Far, Flash and a quiver of other 'yaks.
    "Bound fast is boatless man."

  26. #26
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    Default Re: Sail Area Differences

    Quote Originally Posted by Ben Fuller View Post
    Have to say that I did this on a Fen Williams 18' cat. Just lengthend the past a foot or so, left the gaff the same and ran the leech down to determine the foot length. It gave me one of the preengine era rigs. The first reef went in around 8-10 knots of wind It worked great, if there was any wind around I could sail. Never had an engine. Boom overlapped the stern by a bit. The first reef got the sail back to what Fen had designed. Then the next reef went in as normal. However, I did have a little experience. Subsequent owner of my cat put in an engine and shortened the rig to what Fen designed.
    I think pre-engine is the key here. When people were entirely dependent on sail, they carried more of it, so that the boat could move in anything above a strong calm. Getting home in the lightest winds was balanced against reefing early, often, and deeply. Now you can put a little outboard on the boat and get home easily even in force 0.

    You fell in love with the boat with the normal rig, so I'd say you should stay with that.

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