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Thread: Off center mast and dagger board - same side or opposite?

  1. #1
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    Default Off center mast and dagger board - same side or opposite?

    Could anyone please advise me as to the sailing advantages/disadvantages of off center masts and daggerboard being on the same or opposite sides of the boat. I am not interested in discussing the merits of center line masts and dagger boards verses off set ones. The boat I have in mind is 15 feet LOA and 3 foot beam. Almost like a canoe. I wish to install a long dagger board slot and multiple mast steps but keep the centerline clear for infinite seat/trim tweaking. This is a learning exercise for me to try different sails I have collected. Thanks, Alex.

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    Default Re: Off center mast and dagger board - same side or opposite?

    I'm no boat designer, but it is my impression that it pretty much makes no nevermind.
    David G
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    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Off center mast and dagger board - same side or opposite?

    I'd put them opposite. Daggerboard goes a wee bit deeper when the mast is a wee bit taller, and vice versa.
    - Mike

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Surf and Turf View Post
    I'd put them opposite. Daggerboard goes a wee bit deeper when the mast is a wee bit taller, and vice versa.
    I've seen arguments both ways. But I seem to recall someone authoritative saying that - in actual use - there was no noticeable difference. Do you have some experience, or reports of experience... or are you theorizing?
    David G
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    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Surf and Turf View Post
    I'd put them opposite. Daggerboard goes a wee bit deeper when the mast is a wee bit taller, and vice versa.
    Thanks. That makes sense.

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    Default Re: Off center mast and dagger board - same side or opposite?

    I"d line them up. In a more extreme case, when asymmetric catamarans are built, the sail, board and rudder are always in the same hull. But in a single, skinny hull, I suspect you'd have a hard time telling the difference.

    I just built a daggerboard case in my Whisp upgrade that is off-center and canted in. I do not expect to feel any real difference on port and starboard tacks. The same boat used to carry a single leeboard on the starboard rail, and the boat sailed the same on both tacks.

    For what it's worth, Bolger put them both to starboard on his Brick:

    -Dave

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    Default Re: Off center mast and dagger board - same side or opposite?

    Thanks Dave. Don't you love this forum? In as many replies I already have a definitive yes, no and maybe!
    I built a Bolger brick but strayed from the plans and it was a bit of a failure. Brick has such a short waterline and huge beam that having the foils and mast on one side seems like the only option.
    Last edited by Al G; 05-18-2017 at 03:42 AM.

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    Default Re: Off center mast and dagger board - same side or opposite?

    you might consider contacting Jim Michalak

    he has successfully designed several sailboats that utilize the "off center..." you are questioning

    his boats have proven themselves in a wide variety of conditions to include the TEXAS 200 & the EVERGLADES CHALLENGE

    just a thought...

    sw
    "we are the people, our parents warned us about" (jb)

    steve

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    Default Re: Off center mast and dagger board - same side or opposite?

    Hi Steve. Thanks, I've learned a lot of design theory from reading Michalak's design blurbs and newsletter over at duck works. Just thought I'd ask here as I haven't read a hard fast rule or been able to blindly copy Bolger on this query. Cheers.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Hi Steve. Thanks, I've learned a lot of design theory from reading Michalak's design blurbs and newsletter over at duck works. Just thought I'd ask here as I haven't read a hard fast rule or been able to blindly copy Bolger on this query. Cheers.

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    Hi Alex, The PDR racers often use offset leeboards. And due to the short fat nature of the boats this makes a pretty good test. Apparently the only real noticable effect is that the boat has slightly more weather helm with the leeboard to windward. This would imply that lining the mast up with the board might be a better way to go from a helm balance point of view? But then with a long narrow hull its not going to make much difference overall anyway.

    One issue with putting both on the same side of that narrow hull is that the boat may list towards that side. Why can't the mast be near the centreline up fwd?

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    Default Re: Off center mast and dagger board - same side or opposite?

    Gday mate. Nice to find a fellow Tasmanian! Good thinking on the PDR. That pretty much settles it for me - that it makes little difference. I'm keen for multiple mast steps on this boat so I can play with different sails and mast positions without having to butcher the boat for every experiment. I want the middle clear for a seating arrangement similar to Phil Bolger's sweet pea, Snow Pea.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Here's my take. Offset centerboards make a lot of sense. They open up the center of the boat for sleeping or more comfortable sitting and make very little difference in overall performance. Offset masts however are just hard to look at (ugly!) and should be avoided at all costs.

  14. #14

    Default Re: Off center mast and dagger board - same side or opposite?

    I think you need to have them both on the same side, for practicality reasons.

    If your objective is to have a clear space down the middle that you can move along, remember that this is a narrow boat. Both the mast and dagger board will eat into that width, and are quite close together. If on opposite sides of the boat, you loose room from both sides, making the clear run down the middle narrower. If both on the same side, you loose less of that clear space.

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    Default Re: Off center mast and dagger board - same side or opposite?

    I have built 3 boats with offset boards, but kept the masts in a central position. I would imagine that the issues of an offset mast would be down to how wide the boat is at that point, and how offset the mast might be. A slightly offset mast to clear a walk way, maybe not an issue. Not had any issues with offset rudders either. Things that might be hyper critical on a racing boat are rarely even noticable for small boats most of us use for pleasure.

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    Seems to me that a bigger issue with an offset mast is going to be with ergonimics. Ducking the boom might be less intuitive than it would be with a centreline mast.

    Prehaps some sort of movable mast box/thwart could work?

    Cystals and sweet pea's seating solution should make for a much safer and stronger boat, though I guess it will add some weight.

    I am looking forward to seeing how your experiments pan out.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Junks often have multiple sails off set off set quite a little. Dinghies that use lee boards generally have the board set on the stbd. gunnel. The LF Herreshoff "Mewdowlark" and "Golden Ball" designs have twin boards that can be raised or lowered on either side of their hulls.
    Jay

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by David G View Post
    I've seen arguments both ways. But I seem to recall someone authoritative saying that - in actual use - there was no noticeable difference. Do you have some experience, or reports of experience... or are you theorizing?
    Just theorizing, and basic trigonometry. I agree the difference is probably in the noise.
    - Mike

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    Default Re: Off center mast and dagger board - same side or opposite?

    Leeboards.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by kenjamin View Post
    Here's my take. Offset centerboards make a lot of sense. They open up the center of the boat for sleeping or more comfortable sitting and make very little difference in overall performance. Offset masts however are just hard to look at (ugly!) and should be avoided at all costs.
    I use offcenterboards ( SCAMP, Walkabout, Tread Lightly, now Long Steps) and sometimes offset masts. There are a few catches, ideally the hull shape around the 'board area needs to be such that the waterflow is at a similar angle when heeled on each tack, but rig wise, the only thing that would concern me is that I'd try to balance the weights up by putting the 'board and case on one side and rig and its step on the other.
    I've found that sailing boats are remarkably tolerant of asymmetry.

    John Welsford
    An expert is but a beginner with experience.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Great advice, thanks. I honestly hadn't considered the weight of the rig. Opposite sides it is. Thanks everyone for your advice.

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    Default Re: Off center mast and dagger board - same side or opposite?

    I like your idea of setting a range of mast steps so that you can experiment and see for yourself what the differences and effects are. I can imagine that in lightish wind, it might be difficult to balance the boat when the mast is positioned on the windward side.

    Rick

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    Default Re: Off center mast and dagger board - same side or opposite?

    Hi, sorry to resurrect this thread, but it caused a question to pop into my head. The OP said the boat was canoe like, and a few subconscious connections later, I had this question:

    What if you're using a steerboard rather than rudder with this rig? Balance issues aside (Lets pretend you're loaded in a way that balances the boa whichever arrangement), would it matter to have the mast, dagger board, and steerboard all on the same side, or should the steerboard be opposite the mast and dagger board?

    I know it's an impractical question, but my internal Philosoraptor stared driving me nuts over it. Partly it's to help me understand the physics of keeping your boat running in a straight line, partly, just pure, raw curiosity.

    Thanks!
    Chris
    I'm sure there are many wonderful free boats out there. But the truth is I don't want one of those. I want to build one.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Keep in mind that even when a perfectly symetric boat sails, all the forces applied and even the hull below the active waterline are asymmetric. So no matter how you line up sails and foils, once they start working things are not at all straightforward. Having these elements off center just doesn't seem to upset the applecart, which is already well askew anyway.
    -Dave

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    Default Re: Off center mast and dagger board - same side or opposite?

    Whatever you do, take pictures! Seems like there are many other trim and balance factors that add up to minimize any impact realized from offset mast and trunk.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Woxbox View Post
    Keep in mind that even when a perfectly symetric boat sails, all the forces applied and even the hull below the active waterline are asymmetric. So no matter how you line up sails and foils, once they start working things are not at all straightforward. Having these elements off center just doesn't seem to upset the applecart, which is already well askew anyway.
    Very astute comment Dave!
    Jay

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Al G View Post
    Could anyone please advise me as to the sailing advantages/disadvantages of off center masts and daggerboard being on the same or opposite sides of the boat. I am not interested in discussing the merits of center line masts and dagger boards verses off set ones. The boat I have in mind is 15 feet LOA and 3 foot beam. Almost like a canoe. I wish to install a long dagger board slot and multiple mast steps but keep the centerline clear for infinite seat/trim tweaking. This is a learning exercise for me to try different sails I have collected. Thanks, Alex.
    I've designed, and people have built from those plans, a number of boats that are asymmetrical in terms of location of masts and (off) centreboards. There are some issues around the waterflow under the boat but if you place the "board" close to the widest part of the waterplane you'll be close enough, and offset rigs dont seem to make any difference at all.

    Good luck with that, at worst it will be a learning experience.

    John Welsford
    An expert is but a beginner with experience.

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Snow Pea View Post
    Hi Alex, The PDR racers often use offset leeboards. And due to the short fat nature of the boats this makes a pretty good test. Apparently the only real noticable effect is that the boat has slightly more weather helm with the leeboard to windward. ...
    --- Maybe. I sailed one for the first and only time in a Texas 200, and I recall having that tiller pulled into my knee for 5 days -- but sailing was mostly with wind on the starboard quarter. More likely it was a normal weatherhelm with a boomed standing lug with sheets eased? Could have been sail balance? I didn't think so (imagine a 56 s.f. Wooden Boat Store standing lug on the PD -- it seemed adequately balanced to me). There was some tacking, however, a few hours worth in total, but I don't recall a difference that made itself noticed -- nothing annoying, anyway. But a very short boat is such a strange thing, and perhaps I was overwhelmed by strangeness and to some extent fatigue.

    There is this: the PD had a weird habit of getting in irons that you would have to take my word for it was a bit of surprize. Even backing and other man-handling was nearly outrageously to no avail. And when as the rage built to peak, the boat would resolve itself and go around, usually (a few times I had to wear, though). A man with much more sailing experience than I have had the same observation. Once, we had the same issue in the same water zone at the same time to the extent that we had to give up our destination and camp where we could. Perhaps this was just a form of short-cat-rigged-boat-osis, but now I wonder if the rotational moment of offset rig/board or some induced hydrodynamics because of the offset was the key to this mystery. --Wade
    Last edited by wtarzia; 02-27-2019 at 09:28 AM.

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    Default Re: Off center mast and dagger board - same side or opposite?

    I have a Bolger Gypsy with the dagger board offset to the edge of the bottom panel. It does not appear to make any difference which tack the boat is on. My level of expertise is such that I might have missed the difference. It does make the boat a lot roomier. Being the only sail boat on the lake limits opportunities for comparison.

    It does look like you could get a significantly larger heeling moment on a wide flat bottom boat with the board opposite the mast. More vertical distance between centers of effort when heeled one way or the other? One of the NAs would know better than me.
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quick thought exercise: What's going on when a catamaran is sailing on one hull? Does that seem to work? How about a trimaran, which sometimes sails on the center hull, othertimes mostly on an ama?

    Having sailed both types a lot, I can say that the balance of things remains just fine as these boats heel.
    -Dave

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    Default Re: Off center mast and dagger board - same side or opposite?

    After 60 years of sailing with mast and CB in line and off line to small or greater degree I find the difference is not usually noticeable in normal circumstances. Normal means not heeled over enough to lift the CB partly out of the water. Since you are doing sail comparisons, I'd suggest eliminating as many variables as possible and line them up.
    Tom L

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    Default Re: Off center mast and dagger board - same side or opposite?

    Quote Originally Posted by Woxbox View Post
    Quick thought exercise: What's going on when a catamaran is sailing on one hull? Does that seem to work? How about a trimaran, which sometimes sails on the center hull, othertimes mostly on an ama?

    Having sailed both types a lot, I can say that the balance of things remains just fine as these boats heel.
    --- And some proas have their board in the ama, WAY off center from the mast. --Wade

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    Default Re: Off center mast and dagger board - same side or opposite?

    We sailed our Bolger Jessie Cooper several thousand miles which had the main mast, centerboard, and mizzen on the starboard side and never found we could tell the difference from tack to tack performance wise.

    Just my two cents...

    Bob

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