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Thread: Moonfish Build in UK

  1. #36
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    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    Making the rudder has caused me more head scratching than any other part of this build. As allowed for in the Moonfish plans, I am using Sunfish rig and foils. The challenge is finding out the exact dimensions of the foils - particularly the rudder.

    The Sunfish class regulations give this information:



    While there are enough dimensions to work out the size and shape of the bottom part of the foil, there is nothing about the size, angles, curve radii or mounting holes (for tiller, rudder head and tension spring). In an ideal world, I would find an existing foil and just take the dimensions from it - but Sunfish aren't all that common here in the UK.

    So what I did was find the clearest photos that I could of the foil and the rudder head/tiller on the web and print them out blown up to the largest size I could without loosing resolution:





    By careful measurement of the photos (in both x and y axes, to take into account probable distortion of the photo views and printing/enlarging processes and all the necessary angles and radii) and comparison with the plan and the Sunfish rudder head and tiller plates that I had bought, I was able to rough out a hardboard template:



    I then fitted the rudder head and tiller plates to the template which allowed me to refine the rough shape and position the three holes:



    This whole arrangement allows the foil to kick up, yet be held securely in either the 'down' or 'up' positions without the need for lines.

    The Sunfish class regulations give the thickness of the foils as 3/4" (+/-), which matches the gap in the rudder head. To achieve a blank of this size, I had to laminate three sheets of ply: one of 12mm, one of 6mm with one of 4mm sandwiched between them:


    which worked well after a night curing under quite high, but uniform pressure.



    I then marked out the edges and shaped them down, mostly using a low angle block plane (with a small sureform in places), finishing off with sandpaper. There were some rough spots left where some of the rougher filler laminations of the ply were exposed; I filled these with wood filler and then sanded back again to achieve smooth curves and corner radii. The whole thing was then stained with mahogany wood dyes - as I had done on the deck of the hull.

    You will see that the three mounting holes have been enlarged (to 20mm with a forstner bit). These will be filled with epoxy before being drilled out again to the exact sizes. This will give me mounting holes that are (a) more robust than bare wood and (b) impervious to water penetration.

    Next up: finishing the rudder and making the daggerboard.
    Nick

  2. #37
    Join Date
    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    And a Few More ......

    ..... gratuitous shots of her outside on the refurbished 1960s trailer:





    A bit easier to appreciate the lines, I think.
    Nick

  3. #38
    Join Date
    Mar 2008
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    West Wales, UK
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    463

    Default Re: Moonfish Build in UK

    Getting Ahead of Myself

    I've got way behind with this thread and will work hard to catch up.

    Today, however, is the Red Letter Day - completion:




    Sorry - couldn't resist !

    I still owe posts on the daggerboard, tiller, spars, sail and trailer and will get on to them directly.

    (Just hope the 'Sea' Trials don't get in the way !)
    Nick

  4. #39
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    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    Daggerboard

    The daggerboard diagram in the Sunfish class rules was much easier than the rudder one to take accurate dimensions from:





    I did have to take into account, however, that the distance between deck and bottom of hull (given as 13 3/8" for the Sunfish above) is different in the Moonfish.

    Once I had the outline dimensions, I laminated two sheets of 12mm ply together using epoxy thickened with silica spread pretty thinly after prepping the boards with neat epoxy to prevent soakaway weakening the join. I then marked and cut out the blank with a jigsaw, using a thin Starrett blade and drilled holes to get around the curves accurately:




    This was then planed accurately to size all round, before marking out both the thickness and the depth of the foil edges:





    These were then all planed, Sureformed and sanded back to the marks. In doing this, I came upon quite a few voids in the ply laminations (but not in my glueline !) which I filled with filler and sanded back. I lived to regret this later ! Sorry, no pics of the foil at this stage !

    I did this work quite early on in the project, as the plans were very clear that the Sunfish foil was differently sized to the Moonfish ones and that the box in the central 'girder' of the frame had to be built to the revised dimensions. The work this far gave me the dimensions I needed, so I left work on the daggerboard there until the end of the project when I finished off both foils.
    Nick

  5. #40
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    Mar 2008
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    Default Re: Moonfish Build in UK

    Finishing the Foils

    Once I had finished the hull and got it out of the garage and onto the trailer, I had bench space to finsh off the foils. Most of the work was pretty straightforward but, as ever, there were one or two minor challenges along the way.

    Probably the one that remains most noticeable is that - in order to get the Sunfish rudder head to fit - I had to sand back the head of the rudder foil through the first, very thin layer of hardwood veneer:

    This is aesthetic only ..... but it niggles me. The foil was made exactly to the specified thickness (3/4") but at that thickness the head wouldn't fit on - let alone rotate around its pivot bolt ! I took off as little wood as I dared and substituted the rather thick teflon washers (which you can now see used on the tiller bolt) for a much thinner pair make from milk bottle (in the US aka 'jug', I think ?) thermoplastic. Seems to work - another thing to test in sea trials.

    Once fully shaped (which included cutting the handle for the daggerboard and ensuring that the curve at the top of the rudder was good), the ply on both foils was given the mahogany wood dye treatment that I had given the decks. This worked better than expected where the edges were shaped - except where I had had to use filler on voids. The filler now stands out far more than I am comfortable with - all functional, though I suppose ...


    Next, the foils were given a coat of epoxy, before I applied a layer of glass cloth on both sides and biaxial tape on the leading & trailing edges and bottom ends of the foils. All of which went with several layers of epoxy and quite a bit of sanding ! They were then finished off with several coats of the same (Coo Var) yacht varnish that I had used on the decks.

    I'm more pleased with the rudder:

    than I am with the daggerboard:
    although this is all aesthetics. Functionally, they should both be sound.
    Nick

  6. #41
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    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    A few more shots:

    Daggerboard handle and mahogany deck stops:


    Trailing edge:


    leading edge:


    Black dots on the leading edge were the 'cut to' marks on the glass cloth. I forgot them until after I had squeegee'd on the epoxy. Duh !


    Much less filler on the rudder edges:

    If I can find the right stock and some time over this winter, I may well replace these plywood foils with solid wood boards.
    Nick

  7. #42
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    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    After a winter of waiting, we conducted sea trials of Blue Streak (as the Moonfish has been named) on Easter Day.

    After suitable christening with beer:


    she was launched onto the River Cleddau.

    She floated (level !) and the test pilot reported that, when there was wind, she sailed well:



    Unfortunately, there wasn't much wind and he was really unimpressed at having to paddle back the last quarter of a mile to the slip against the incoming tide !

    All the rig seemed to work as it should and I'm pretty pleased with the shape of the polytarp sail. We'll have to wait for some better wind when the test pilot is next available (heavily engaged in revising for upcoming public exams - GCSEs) to see how she performs when pushed a bit harder.
    Nick

  8. #43
    Join Date
    Jan 2007
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    North Shore, Massachusetts
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    Default Re: Moonfish Build in UK

    Quote Originally Posted by Whameller View Post
    After a winter of waiting, we conducted sea trials of Blue Streak (as the Moonfish has been named) on Easter Day.

    After suitable christening with beer:


    she was launched onto the River Cleddau.

    She floated (level !) and the test pilot reported that, when there was wind, she sailed well:



    Unfortunately, there wasn't much wind and he was really unimpressed at having to paddle back the last quarter of a mile to the slip against the incoming tide !

    All the rig seemed to work as it should and I'm pretty pleased with the shape of the polytarp sail. We'll have to wait for some better wind when the test pilot is next available (heavily engaged in revising for upcoming public exams - GCSEs) to see how she performs when pushed a bit harder.

    how did I miss this thread?

    cool boat! nice job, a very Popular Mechanics type home built, very cool, looks like fun.

  9. #44
    Join Date
    Dec 2011
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    North East England
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    Default Re: Moonfish Build in UK

    Or use Tapatalk App, free and you donít have to upload the pictures somewhere else

  10. #45
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    Mar 2008
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    West Wales, UK
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    Default Re: Moonfish Build in UK

    Quote Originally Posted by Daniel Noyes View Post
    how did I miss this thread?

    cool boat! nice job, a very Popular Mechanics type home built, very cool, looks like fun.
    Glad you enjoyed the thread. She's now starting her third season of pretty hard use and performing well - all the better after we replaced the polytarp sail with a proper Sunfish-pattern sail.
    Nick

  11. #46
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    Jan 2007
    Location
    North Shore, Massachusetts
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    Default Re: Moonfish Build in UK

    thats' great, though not a surprise, little boats like this are great fun to sail and simple to maintain... and seem to get used very regularly when owned by folks who really enjoy sailing.

    any more photos?

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