Mirror 16 foot Sailing Dinghy

Discussion in 'Wooden Boat Building and Restoration' started by goolawah, Jun 6, 2006.

  1. danp
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    danp New Member

    Hi Rod,

    For the centreboard thickness I have 19mm. The width of the centreboard case slot is 25mm (in the centreboard case assembly that's above the floor).
     
  2. Ozducati
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    Ozducati Mirror 16 #189

    Thanks for the dimensions Dan. I will get in contact with again when I get to the gunwales and inwales to confirm the stock sizes of these parts,

    I have made a bit of progress in between running around over the weekend.

    One thing that I am wondering about..... the third set of floor webs back from the bow on the original Mirror 16 did not have the ventilation (or weight reducing) holes like the remaining webs. Does anyone have any idea why this was so?
     

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  3. goolawah
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    goolawah Junior Member

    I believe it was to provide separate bouyancy compartments. If you managed to punch a hole in the (4mm ply) outer skin you would only lose 1/4 of the total under-floor bouyancy. There should still be limber holes in all of the floor webs to allow drainage through the drain ports in the transom. I know some M16 owners fit the limber holes in the two solid webs with bungs which they can remove via an access port if necessary.

    Also, I would suggest finishing the corners of the floor web apertures with quite a big radius.
     
  4. goolawah
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    goolawah Junior Member

    The 'virtual model' is looking great Rod!
    I haven't checked the centreboard/case dimensions yet as I have been reluctant to remove the tarp from Lulubelle with all this rain threatening. I'm sure Dan's dimensions will be right.

    When I do get to it, there are a couple of other details I'll try to sketch out. I made a small change in the assembly of the centre-case to the forward and aft spine sections. Also, it is going to be important to get precise details of the pivot fitting. Perhaps a photograph of that might be useful.

    Would it be OK to include your pictures in the next WBAQ newsletter?
     
  5. Ozducati
    Joined: May 2008
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    Ozducati Mirror 16 #189

    G'day John,
    Feel free to include the images in the newsletter. The other boys might have some useful suggestions/critique. When does the next issue 'go to press'?
    I haven't put rads on anything yet... I'll get the basic shapes and then go back to refine the detail.
    I know a guy who works in the laser cutting business... might be expedient when it comes to making the real thing (cost notwithstanding).

    I scored some 2mm thick card from work that gets thrown out along with other packaging. This stuff comes in varying sizes up to about 6ft long x 3ft wide. I'm thinking of using this for the model and doing it to a 1/4 scale (4ft long). If the model turns out looking half decent the Wooden Boat Club can have it if you think it could be used to fill an empty space on a shelf somewhere.

    The deadline for the plant shutdown (and my redundancy) looks like it's going to be March 31st, so I should have plenty of time on my hands to build the model. Ideally I would like to walk away from Fisher & Paykel and straight into another job, but the way the economy is looking at the moment I don't think that that will be the case.

    I impressed myself (but then again, I am easily impressed) with the centreboard slot dimension. I attempted to scale from the pictures in Larry's assembly book and after a few varying results I came up with 26mm average.... Dan measured the size at 25mm... not bad!

    I was thinking about your concerns regarding rot, and I remember when I was younger that one of my uncles had a pergola post that was starting to rot where the beam for the rafters was set into it. He gave it a liberal dousing with glycol and that was it.. the rot progressed no further. Maybe you could slosh some around inside Lulubelle, or throw a bag of salt around in there. Just a thought.
     
  6. goolawah
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    goolawah Junior Member

    I received this email from the senior member of the Mirror 16 fleet in the US.

    Just as well the development of plans is progressing, so that some of these boats can get new hulls.
     

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  7. dream458
    Joined: Jul 2007
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    Location: Lawrence, Kansas

    dream458 Junior Member

    Floor Ribs

    Hi Rod,

    My name is Katrina, I am the grandaughter mentioned in the thread above. I was looking at your plans, and I was wondering if you were going to round out the corners of the sub-floor ribs, and if not your reason for doing so.

    Also, a small update for all on my project...
    I found blsiters popping up all over the hull this summer, so I popped them this winter and drained them, then proceeded to peel most of the fiberglass off of the wood. It is very strange, it appears as though the glass was never wetted out with epoxy in the first place because what I am peeling off looks like dry cloth. It is unfornutuate, and I have a rather large hole in the bottom of the hull just forward of the centerboard casing that I need to cut out and fix. Any advice from anyone who has cut pieces out of the hull and put them back would be greatly appreciated because I am really not sure how to go about doing that.

    Sorry no pictures, my digital camera hit the dust a while back.

    Katrina
     
  8. goolawah
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    goolawah Junior Member

    Hi Katrina, Great to have you contributing to this thread.
    It depends a bit on how big the hole is. The approach I would adopt is -

    Cut the patch first from ply of the same thickness as the hull. Make it a neat (preferably rectangular) shape that generously covers the area to be patched. Plane the edges to be straight, smooth and slightly beveled.

    Fasten the patch firmly to the outside with a few screws (maybe even nuts and bolts if you can get your hand inside).

    Trace the shape of the patch onto the hull.

    Remove the patch.

    Drill a few holes inside the line to allow penetration with a small hand saw. Then cut to shape staying inside, but close to, the line.

    Use sharp plane/chisel etc to carefully trim and bevel the hole to match the patch.

    Epoxy glue battens (say 1 1/2" by 1/4") inside the hull so that they half-lap across the edge of the hole. Clamp them in place until the glue sets. The more clamps the better. Be sure to wipe off any glue that extrudes into the hole. Otherwise it will be difficult to fit the patch neatly.

    When the first lot of glue is set, glue the patch in place and screw through into the battens.

    The attached picture will give some idea. These were roughly done by a previous owner of Lulubelle, but you'll get the gist.
     

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  9. dream458
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    dream458 Junior Member

    Thanks for the advice, I hadn't thought to put stiffeners behind it, that is a fantastic idea. I wasn't sure how to clamp the final piece into place, and screwing it into somthing that was clamped is a great idea.

    One note, howevever, and it is what prompted my earlier question about the floor ribs, is that a rectangular shape is the worst shape to cut out of a rib, and also the worst shape to cut and replace structural pieces (such as the hull) of the boat. The corners of a rectangle create large stress concentrations which will break much sooner under much less load than a curved corner, which is why most aircraft and boat ribs have circular cutouts. It is certainly much easier to cut rectangles, and it may end up that is what I do to make sizing easier... but the way you described making the patch first, then cutting out from the hull will make it much easier to cut a shape with curved edges.

    Thanks for the advice, I will keep everyone updated on the progress.

    PS- Like the MODYC picture I created for my grandfather? I thought it was pretty clever.... :)
     
  10. goolawah
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    goolawah Junior Member

    You're absolutely right! It would be much better to make it a rectangle (or at least a quadrilateral) with rounded corners.

    Rod tells me that the cut-outs in the floor webs of his model is because he 'hasn't put rads on anything yet'. He certainly will do so.

    I love the idea of M.O.D.Y.C and have submitted your picture for inclusion in the next issue of our Wooden Boat Association newsletter.

    My wife asked me to mention that, if you have to strip old fibreglass, a heat gun is a great help. Full ventilaion and safety gear needed of course.
     
  11. dream458
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    dream458 Junior Member

    Heat gun? I might try it, although you should see how easy it pulled off, especially when it was still damp. It is much more difficult now that it is cold outside and everything has become very brittle. The heat gun might definately help with that.
     
  12. goolawah
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    goolawah Junior Member

    Another point of possibly more general interest.
    A year or so back Lulubelle suffered a small but severe 'puncture wound' (due to a sharp rock hidden beneath the surface of a muddy beach) in the outer skin in a spot where I could not reach from inside..:mad:

    In that case I made an elongated oval hole to remove the damaged plywood. I then made a patch to perfectly fit the hole. Next was a backing piece the same shape but about 9mm (3.8") bigger all round. I glued the patch to the backing piece to make a sub-assembly. I hammered two carefully positioned, fairly long thin, nails into the patch.:idea:

    A bit of epoxy glue around the hole and around the patch and I was able to manipulate it sideways through the oval hole, rotate it 90 degrees, then use the nails to pull it into the hole from the inside until the backing piece stopped against the inside of the hull.:D

    (a picture would be worth a thousand words in this case)
     
  13. dream458
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    dream458 Junior Member

    That is how I had thought to do it at first... kind of.... but I have to replace a fairly large piece. I think I will make some makeshift stringers where the patch is to go and secure them with clamps and epoxy before putting the patch in. That way I will have something moderately structural to attach the patch to when the time comes.

    Sounds like Lulubelle has been through her fair share of rough times!
     
  14. Ozducati
    Joined: May 2008
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    Location: Brisbane

    Ozducati Mirror 16 #189

    Carlin size

    Hello Katrina,

    The internal corners will be radiused eventually.... After seeing all the grief that people are having with cracked ribs I was thinking of doubling the thickness of the web in this area by laminating a second thickness of 4mm ply.

    Your photo of the beached Mirrors is great! The white hull with the lacquered deck is what I envisage for mine when it comes time to build it. It was good to see one in the 'flesh'.

    Anyway, back to work.....
    Under the corners of the deck where it meets the gunwales is a piece of timber which the Building Instructions refer to as a 'carlin'. Attached picture shows the location of the carlin.
    Can someone let me know the dimension of the carlin shown on the second image, please?

    Also looked up the definition of 'carlin'....hmmmmm....
     

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  15. ICLYM
    Joined: Oct 2008
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    Location: Lymington UK

    ICLYM Junior Member

    Hi Looks like new Foredeck, Transom, repairs to underside of hull near transom, I think I also need to lift cockpit floor and look at state of interior frames plate case etc. I have original trailer mast and mainsail with the boat. I am very interested in your progress with CAD hull design. I have been worked with building small boats using CNC cut ply panels before and I think the structure of the 16 might well lend itself to this process. Have tried to attach pics of boat. Please note I have an original trailer with her!
     

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