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Thread: Building a Hybrid Moonfish

  1. #1
    Join Date
    Mar 2018
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    Default Building a Hybrid Moonfish

    Our summer vacation fleet needs something that sails to complement the outboards, canoes and kayaks already on hand. So Iíve started building a Bateau.com MF14 Moonfish. The Moonfish is a tape-and-glue small plywood sailboat, similar to a Sunfish. The objective is to have her ready by this time next year.


    Sheíll be joining a fleet that features cedar strip-plank boats. Thatís where the ďhybridĒ comes in. Instead of ply, this Moonfish will have cedar strip topsides and deck. Iíll be using versions of the strip building techniques described by Schade, Folsom and others for kayaks and canoes. Topsides and deck will be finished bright.


    A few prior Moonfish builds have been well documented online here:
    https://forums.bateau2.com/viewtopic.php?f=13&t=20214


    Here:
    https://forums.bateau2.com/viewtopic.php?f=14&t=58206
    http://forum.woodenboat.com/showthre...sh-Build-in-UK


    And thereís another underway here:
    https://forums.bateau2.com/viewtopic.php?f=13&t=62869


    Iím indebted to those builders for pre-answering many of my questions and offering lots of good ideas. Now I get to make my own mistakes, of which Iím sure there will be quite a few.


    My sole prior experience in boatbuilding was a stitch-and-glue rowboat about 20 years ago. Iíve been planning this build since January, waiting for the weather to warm up and my daughter to get her stuff out of our garage. Thatís given me plenty of time to overthink everything. This certainly wonít be the fastest or most economical way to build a Moonfish. But itíll be fun! So here we go Ö

  2. #2
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    Default Re: Building a Hybrid Moonfish

    Bateau.com offers a CNC-cut kit for all the plywood pieces, but I couldn’t see ordering the kit only to throw a considerable portion away. So I’ll be cutting the plywood myself. The experience is good for me, right?


    There’s a boat in here somewhere:
    003 Half-inch ready to cut.jpg

  3. #3
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    Default Re: Building a Hybrid Moonfish

    Hey, look, I found a transom!

    006 Transom.jpg

  4. #4
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    Jan 2007
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    Default Re: Building a Hybrid Moonfish

    Quote Originally Posted by Chenier View Post
    Hey, look, I found a transom!

    006 Transom.jpg
    thanks for sharing, sun fish are awesome.

  5. #5
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    Default Re: Building a Hybrid Moonfish


  6. #6
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    Annapolis, MD, USA
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    Default Re: Building a Hybrid Moonfish

    Here's a visible sign of progress - the frames are all cut and trimmed.


    007 Frames.jpg


    Lightening holes, ventilation holes, limber holes and drain holes will all be cut later, after I assemble the parts and see where the longitudinals intersect the frames.


    Those longitudinals, the stringers and trunk sides, are next at bat.

  7. #7
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    Default Re: Building a Hybrid Moonfish

    The longitudinals are cut and trimmed. Bow and trunk sides on the left, aft stringers on the right.


    There are two trunk sides and two aft stringers - the pairs were cut stacked so that both sides of the boat would have the same mistakes. The boatbuilding literature calls this "symmetry".

    010 Longitudals.jpg

  8. #8
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    Default Re: Building a Hybrid Moonfish

    I tackled trunk/bow stringer assembly. This is a slight departure from the build notes which would have me lay out the deck next. As you can see from the photos my garage shop doesnít have a lot of extra room, so Iím doing as much as I can before erecting a big 4íx16í worktable.


    Here Iíve cut cleats for the mast step and daggerboard from cypress and added lightening holes to the big plywood parts. The lightening holes are partly to save weight but also to allow some air circulation during the months the boat will be in storage. The build plans say ďRespect minimum 2Ē offsetĒ for lightening holes in the frames. That seems like a good guideline. In addition Iím keeping 2Ē between holes.


    011 Trunk and Bow Stringer parts final.jpg


    Kindly ignore the limber holes some idiot cut on the deck side of the stringers. Thank you. The working limber holes are on the hull sides of these pieces.


    Next is a dry fit of the assembly. It took a while to get everything square and clamped into position. Then I drilled through at each of the cleats and pegged the assembly with 1/4Ē red oak dowels. That holds it square and let me put each component exactly where it belonged when epoxying.


    014 Trunk and Bow pegged with dowel.jpg


    This photo is the way the whole structural frame gets built - upside down on a flat deck.


    The epoxy step was a bit of a mess, in part because the last time I fooled with marine epoxy was about 20 years ago. Iím trying out SilverTip because the manufacturer says you can let it sit for 72 hours before needing to sand when putting more epoxy over it. Everyone else says 12 hours - even the same manufacturerís other brand of marine epoxy.


    Before assembling everything I coated the inside of the trunk sides with epoxy so I wouldnít have to get into that slot later. Then came a small frenzy of epoxy gluing and fiberglassing. There was enough play in the structure that the final piece, the starboard trunk side, might not line up with the dowels if the epoxy set firm. Fortunately, using slow hardener, there was enough flexibility after 1.5 hours to get that piece in place and then clamp everything:


    016 Trunk and Bow Stringer epoxied up.jpg


    In this photo the deck side is up.


    The Build Notes say to fiberglass inside of the mast step and inside the daggerboard slot. I used the method recommended in Gougeon Bros. book: Lay a piece of fiberglass around three sides of the hole. Apply a second piece to the fourth side, then close up the assembly. In retrospect it would have been much easier applying the glass as four pieces - one for each side of the hole. Except for the bow side of the mast step, all the glass could be applied to its appropriate component the day before. Live and learn.

  9. #9
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    Default Re: Building a Hybrid Moonfish

    A nice operation you've got going there.
    I was born on a wooden boat that I built myself.

  10. #10
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    Mar 2018
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    Annapolis, MD, USA
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    Default Re: Building a Hybrid Moonfish

    Itís been a while. Spent the rest of the summer and early fall using and repairing other boats. Now itís time to get back to the Moonfish!


    In this phase Iím working on the long, skinny parts. The 24-inch wide worktable is extended to 15 feet for cutting the side and bottom panels. Iíve also built an overhead storage rack to hold said long skinny pieces out of the way until the build is ready for them.


    024 Storage rack in action.jpg


    Side panels were next up. As mentioned earlier these will be ďstrip builtĒ: made of 1/4-inch x 3/4-inch cedar strips edge glued together. Later in the build these will be sandwiched in 6-ounce fiberglass and epoxy. This is the ďHybridĒ in the Hybrid Moonfish. Some kayak and canoe builders use this technique to produce compound curves and stunning designs. Iím using it just for the looks. That gives me some leeway in how I do the strip build. While borrowing heavily from the strip builderís toolbox Iíll take advantage of the fact that the Moonfishís deck and sides start life as flat panels. The deck stays flat while the side panels take a simple curve in one dimension (the long way.) Iím building these panels flat and will bend the sides into place later in the build.


    The strip builders construct their craft on molds spaced one foot apart. Iím in no position to argue so I set up MDF molds with that spacing. Rather than using staples or hot glue to conform my strips to a curve, Iíve set up each mold as a little panel clamp to keep the panels flat.


    029 Glueing up strip number 8.jpg


    The strips themselves were obtained from a supplier of strip-built kits so I didnít have to cut them myself. These are flat panels therefore no need for bead and cove. Since the strips are only about seven feet long Iíve joined them lengthwise with scarf joints. Theyíll need to hold together when bent onto the side of the boat, so 8:1 scarfs. Strips are glued together one at a time with TiteBond, the favorite glue of strippers. In the above photo the eighth strip was just put in place. You can see the extra clamps for a scarf joint about half way down the table. The tape between molds helps compress the strips together - TB doesnít like gaps. After an hour the tape and clamps come off and another strip gets added.


    In theory if one were a perfect craftsman there would be no difference between the panelís two sides. But Iím not such a craftsman so thereís a distinct difference between the side I can see while Iím building and the side I canít see. Therefore the side I canít see becomes the ďinsideĒ to hide my sins. Hereís the port side panel all glued up:


    030 All strips glued up.jpg


    Then I reversed the molds to glue up the starboard side.


    Once both sides were glued I stacked the panels back-to-back and taped them together so I could cut them as one. Here Iím laying out the curve of the bottom:


    034 Laying out bottom curve.jpg


    Et voila! Two side panels.


    040 Two side panels.jpg


    Thereís a bit of scraping and sanding in my future to knock off the squeezed-out glue and fair the surface...

  11. #11
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    Default Re: Building a Hybrid Moonfish

    I want to be a boat when I grow up!

    053 Rough cut deck template.jpg

    Just finished the rough cut of the deck template, still need to trim it to the lines that you see in the picture. Since the Moonfish uses the deck as a construction platform, I'm using a BC plywood deck template so I won't feel bad about drilling holes for construction cleats etc. in the fancy strip-planked deck I'll build later.

  12. #12
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    Default Re: Building a Hybrid Moonfish

    I imagine that you are already aware of this, but I'll mention it just in case. When bending flat stripped panels to make boat sides you can have the inside surfaces pre-fiberglassed. The bend will put the glass in compression a bit, but not generally enough to be a problem. The outside surfaces, however, are usually a different story. Glassing them flat and then bending them puts the outside fiberglass layers in tension, stretching (and often micro-fracturing) the fiberglass. The laminate is both weakened and the tiny fractures may show on clear finished panels - something which can not be fixed. So you want to do your outside glassing after the panels have been assembled and bent to their final shapes, or possibly on the bench, but pre-bent into the approximate curve they will take on the boat. Unless you are doing something drastic in the way of bending and twisting (which you won't be) the inside fiberglass is enough to hold the panels together long enough to get them tacked together in preparation for glassing the boat's outside.

    Been there, done that. This one had 1/4" thick side strips, 3/8" thick bottom panel strips and 7.5 oz, fiberglass with three small ash "runners" on the outside bottom (un-glassed) for skid protection.

    drift-boat.jpg

  13. #13
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    Default Re: Building a Hybrid Moonfish

    Very good to know - Thanks!

    I'd been planning to bend the side panels in place and glass later. Theortically it works - at least on the 12"x24" test panel I made up. But pre-glassing the inside is probably lots safer for the panel and certainly a lot easier for the boatbuilder than cutting those fiddly bits of fiberglass to fit between the frames. I'll give it a try when I get there.

  14. #14
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    Default Re: Building a Hybrid Moonfish

    Laminating a sheer clamp:

    057 Laminating a Shear Clamp.jpg


    But wait. The MF14 doesn't have sheer clamps.


    From the examples online, Moonfish builds end up with a noticeable gap between the deck and the side panels. The gap dissapears after it's covered with fiberglass tape, epoxy and paint. But since the deck and sides of this Moonfish will be finished bright, a gap won't do. Shear clamps on each side will replace the cleats outlined in the Build Notes and allow the deck to be firmly affixed to the side panels. They will also fill any gaps that might appear when I radius the deck/side joint.


    The sheer clamp is 3/4" x 3/4", laminated from three cedar strips, on the left side of the assembly. I'm laminating because a solid piece of cedar or cypress won't take the bend by itself. And I'm not about to build and fire up a 15-foot steam box when I have easy access to cedar strips and epoxy.


    To the right of the lamination, the large strip you see with the shiny top is my fairing batten covered with packing tape to keep epoxy from sticking. It's held firmly against the edge of the deck template by pine cleats screwed into the worktable. This forms the basic shape. The deck is also screwed into the worktable, under the poly sheet, to make a rigid jig. Spring clamps and a sprinkling of quick clamps hold the cedar strips against the jig while the epoxy sets up.


    I made two of them, one for each side. The sheer clamps will be trimmed to fit and glued in place just before the deck goes on. In theory I could wait to laminate until then. But, being in uncharted waters, I didn't want to risk distorting the boat with wierd stresses. Not to mention this is a sloppy process and cleanup is way easier at this stage when it can't dribble all over the rest of the boat.

    059 Sheer Clamps.jpg
    Attached Images Attached Images

  15. #15
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    Default Re: Building a Hybrid Moonfish

    All the pieces for the internal structure are cut and dry-fit in place.

    062 Inside structure, rough - bow.jpg
    063 Inside structure, rough - stern.jpg
    I'll be cutting lightening holes before gluing it all together.

  16. #16
    Join Date
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    Default Re: Building a Hybrid Moonfish

    Sweet project! Those strip built panels are going to look great.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

    15' Welsford Navigator Inconceivable
    16' W. Simmons Mattinicus double ender ​Matty

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