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Thread: GIS Yawl

  1. #16
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    I had written a longer reply basically agreeing almost entirely with Clint.

    The only thing I really wanted to add was that the mizzen should not line up with the transom.

    Best if the transom is the only one at that angle ... then it makes more of a statement about the hullshape.

    MIK

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  3. #17
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    Quote Originally Posted by jmk89 View Post
    Clint

    If all you are using a mizzen for is the trimming function of holding the vessel head to wind, wouldn't it be possible to just use a sea anchor (i.e. a canvas cone with the tip cut off at the end of an anchor warp). That looks like much less effort, takes up less space and you will drift to leeward more slowly as well.

    My view is that a sail that doesn't help with sailing is too much effort, but then again different strokes....

    A trimming mizzen does this job while under way as well as while hove-to.
    Also can be used to balance or even self-steer the boat relative to the wind.

    A sea anchor doesn't do these jobs quite so well ...

    cheers
    AJ

  4. #18
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    Quote Originally Posted by b.o.a.t. View Post
    A trimming mizzen does this job while under way as well as while hove-to.
    Also can be used to balance or even self-steer the boat relative to the wind.

    A sea anchor doesn't do these jobs quite so well ...

    cheers
    AJ
    Agreed, but it seems a lot of fiddle for marginal benefits when you are dealing with a well designed and thoroughly sorted boat and when most circumstances that Cliff mentioned would be when the vessel is hove-to.
    Cheers

    Jeremy
    If it were done when 'tis done, then 'twere well it were done quickly

  5. #19
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    Quote Originally Posted by jmk89 View Post
    Agreed, but it seems a lot of fiddle for marginal benefits when you are dealing with a well designed and thoroughly sorted boat and when most circumstances that Cliff mentioned would be when the vessel is hove-to.
    Aye.
    But then, some people like to have that extra piece of string to fiddle with.
    Sort of like the difference between manual & automatic cars I guess.
    And then there is aesthetics... some just like the look of the extra sail.
    That it can perform a useful function is icing on their cake.

  6. #20
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    Thanks Clint for your explanation.

    Does that mean that once you raise the mainsail (e.g. at GIS) you need to control both sails?
    Would the Goat sail even faster then if you sail with mizzen up? Or is the air flow arround the mainsail out of sync with the mizzen (as it is further back at the stern)?

    Peter

  7. #21
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    You can almost forget about the mizzen if it is very small...it has so little effect on the drive of the boat...it may have control over the amount of weather helm, but no the boat won't go faster or slower with or without the mizzen. It really effectively adds nothing to the overall sail area...in fact my mizzen which will be about 15 SF maybe a few more is only counted as half that area when if comes to figuring out the total center of effort of the sails. So that is maybe 8 SF...not going to make a big difference. But with the luf down and the mizzen trimmed in tight...it will help the boat ride into the wind or any of the other uses I explained before. So, yes you need to control both sails, but the mizzen very little compare to the big lug.

    Clint

  8. #22
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    With Beth and my limited number of hands I found that I still had to a reasonable amount of trimming.

    Usually after a tack a little and for any major course changes downwind. The rudder gives pretty direct feedback to tell you when something is not set up right.

    Michael.

  9. #23
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    One other thing misplaced in my not saving a previous post was that for a small sail like this there is a great argument for going tall as the sail will be much more able to keep the nose up to the wind.

    This is why I was so interested in the Salcombe Yawls ... that tall mizzen is as sexy as hell but also if functional if the twist is controlled.

    A second factor is to keep the mast weight right down even with the height increase so a sailboard mast looks like a good choice.

    Michael

  10. #24
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    Mik, the question of what aspect ratio is right for a mizzen intended as a trimming sail is a debatable one. Do you know Tony Dias, a US small craft designer, very good. I sailed abit with him this past summer in one of his boats. His approach for a trimming sail is small (he drew the mizzen on one 17' boat at 11 SF!) and raked far aft to get the mizzen CE further aft. I believe his thought was that this was better for keeping the boat head-to-wind and easier to stow in a sail-and-oar boat (something that I like). It makes sense, but so does your thought of high-aspect with CE further forward. It'd make a great debate and I might try to stir it amongst some yawl fans I know of...here is a Q:

    How tall can one go without requiring battens...I'm incined to stretch my mizzen shape vertically a little bit...but not sure how far to go...I'll play with it again soon and post a result, but in the meantime I'd be interested in the answer...it could mean not having to deal with a boomkin, which would be nice, but it'd probably mean having to use a boom rather than sprit. (Another thing Dias liked was to sleeve the mizzen mast in the sail and the yard of the lug in the sail...his standing lugs are very Nigel Irens-like).

    This may be an example of there being many ways to achieve a similar result!

    Clint

  11. #25
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    The limitations on spar height are

    1/ weight of the mast - it doesn't need to be much bigger diameter but it does need to be longer which adds weight. A windsurfer stick makes a lot of sense!

    2/ without battens (which is sensible for easy furling) the leach is cut with a slight hollow. At some point that hollow might become quite meaningful if the sail is high and thin resulting in a very narrow sail near the top ... there is no point in this

    3/ problems with sail twist. if the sail twists excessively then there was no point going high in the first place. A great argument for a sprit boom.

    X/ a funny argument I just thought of is that a tall mizzen can easily be allowed to twist off by easing the snotter a whisker rather than reducing the sail.

    XX/ a narrow sail is easy to furl without leaning so far over the back of the boat and allows for a shorter boomkin etc or may be able to avoid a boomkin using dual sheets from the transom corners.

    As far as a debate ... I would frame it from the point of view that the height does make the nose to wind effect stronger assuming twist is controlled. The shorter foot and lower area allows retrofitting to an existing boat with smaller changes to the existing rig.

    I don't think anyone would be technically equipped to make any argument based on aspect ratios ... it is an insignificant effect and even more so when applied to an insingificant sail ... the whole argument of making it taller is just to get more turning effect from a very small sail.

    MIK

  12. #26
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    Clint,
    Interesting concept you are developing here hope you don't mind me asking some questions.
    1. How will the mizzen be stepped to allow for tiller, offset I assume so how does this affect performance on either tack.
    2. What use are you proposing for your GIS as it seems you regard a mizzen as critical to your sailing along with good rowing qualities from the hull.
    3. My guess is balancing mizzens have been developed over the years for specific handling characteristics as you have previously descibed ie fishing and such or perhaps to correct a deficiency in rig balance or hull form ie to remedy lee helm. I have not read any descriptions on how the GIS steers on all points so I am assuming no news is good news as in it is well behaved on all quarters.
    So I can't help wondering if this exercise maybe somewhat futile, I hastily add that I do not mean to quench you enthusiasm for the project. Experimentation is always a good thing and an admirable pursuit in itself.

    Just wondering
    Mike

  13. #27
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    Some issues I would like a shot at here too Mike, if you dont' mind.

    Quote Originally Posted by m2c1Iw View Post
    Clint,
    Interesting concept you are developing here hope you don't mind me asking some questions.
    1. How will the mizzen be stepped to allow for tiller, offset I assume so how does this affect performance on either tack.
    Slightly offset ... that is why the mast is so close to the transom.

    2. What use are you proposing for your GIS as it seems you regard a mizzen as critical to your sailing along with good rowing qualities from the hull.
    Not ideal from storer's point of view as he likes the simplicity of the original boat and can't see the real need. However I am happy to collaborate to make this hybrid behave as well as possible

    3. My guess is balancing mizzens have been developed over the years for specific handling characteristics as you have previously descibed ie fishing and such or perhaps to correct a deficiency in rig balance or hull form ie to remedy lee helm. I have not read any descriptions on how the GIS steers on all points so I am assuming no news is good news as in it is well behaved on all quarters.
    With the standard Goat there is no problem with balance. Also there is a considerable opportunity with the balance lug to slide the rig backwards and forwards a bit. Also downhaul and stretchiness of halyard have a big effect. If they are set up properly to restrict twist then that tends to induce weather helm as well. (ie a too floppy downhaul can result in a slight feeling of lee helm so best to fix that before the rig is slid forward or back relative to the mast.

    So I can't help wondering if this exercise maybe somewhat futile, I hastily add that I do not mean to quench you enthusiasm for the project. Experimentation is always a good thing and an admirable pursuit in itself.

    Just wondering
    Mike

  14. #28
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    Thanks Mik. I don't think this idea of adding a mizzen to the boat is futile at all, Mike, or else I would not have tried. I have a bit of background in design -- nothing like Mik's but enough to understand the designer's concerns but enough to know what can be done with out ruining something....adding the mizzen is a variation of the original concept but I think it is a variation not a diversion...it is an option that may make the boat more flexible for different people's style of use in different parts of the worls. The great thing....i that the original boat is still there...I will have the original mast step and the ability to step the lug only...it is the same boat.

    2) Mike you asked about the use...I explain in several posts back. I do not ask for rowing qualities from the boat, just a boat that I can row for auxilliary power from one lee side of an island to another lee side of an island with perhaps a burst of sailing between...this can occur in one daysail or in a multi-day sail up the coast. A mizzen is critical, in my view, to using the boat as more cruiser on occassion and as a dayboat on other occassions. So there will be two steps to suit. I also plan to sail with kids and the mizzen will help manage issues of they come up; outside a beach landing stick her into the wind lower the sail and row in...she'll bob into the wind and I can take my time switching to oars.

    I will post the latest drawing that I think will clinch it. Mik, any chance I can get a plan view drawing to accompany the profile views you sent? And I will try to resize the file with the link you sent. I am happy with the latest version, a little more rake in the mizzen and higher cut...

    Cheers,
    Clint

  15. #29
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    Quote Originally Posted by Compass Project View Post
    I will post the latest drawing that I think will clinch it. Mik, any chance I can get a plan view drawing to accompany the profile views you sent? And I will try to resize the file with the link you sent. I am happy with the latest version, a little more rake in the mizzen and higher cut...

    Cheers,
    Clint
    Clint,
    I came across your discussion on another forum re adding an interchangable mizzen.
    I have only sailed on one yacht with a mizzen actually a 50' ketch were it was big enough to be deemed a driving sail I certainly am not qualified to criticise your endeavour nor is that my intent.
    I look forward to the result of your thinking and hope the end result works to your satisfaction.

    Regards
    Mike

  16. #30
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    Can confirm that the Swallow Boats Bayraider does use a windsurfing mast for it's mizzen mast. Also uses one for the gunter spar. Rather than the usual affair of twin wooden jaws going round the mast sides at the bottom of the spar it uses a very neat idea. The top section of the mast has a dinghy fairlead track fitted on it's back face and the bottom of the gunter spar has just a sliding hinged fairlead fixed to it.

    The weights of the different versions are

    Polyester GRP - 430kg
    Epoxy GRP - 370kg
    Plywood Epoxy- 360kg
    Carbon Epoxy - 270kg

    using the same sort of proportions.

    So a Polyester moulded Goat would be 20% heavier
    An epoxy moulded Goat would be about the same.
    And a full carbon Goat about 20% lighter.

    I guess with Goat's large expanses of flat areas which would need greater strengthening the results would be even more in plywoods favour.

    Congratulations to good old plywood I say!

    Would you say these proportions are about right MiK?

    Brian

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