What's that thingy?

Discussion in 'Boat Design' started by Justaguy, Dec 29, 2015.

  1. Justaguy
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    Justaguy Junior Member

    I have to say that, while I enjoy learning, I'd almost rather learn a foreign language than these nautical terms. You know, something simple and practical like Outer Mongolian. Can someone please tell me what was wrong with the words "front", "back", "left", "right", "middle", "rope", etc? :confused:

    Anyway, on to the real topic. I'm trying to remember what a particular boat thing is called. It's a protective strip attached to the bottom of the hull, sometimes running the length of the hull. Typically they exist in pairs, equidistant from the centerline. The word "skeg" keeps haunting me, but that's not right (I think skegs are on the centerline, taller, wedge-shaped and attach to prop, etc). I'm talking about something like a 1x2 on which the hull would come to rest if put on flat dry land.

    Although it isn't exactly what I'm talking about, I attached a photo with a rough example.

    So, what is that thingy? ;-)
     

    Attached Files:

  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Call it a strake, and that would be close enough.
     
  3. SukiSolo
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    SukiSolo Senior Member

    That hull looks like a Mirror, I'd be amazed if it is not. Here in the UK we would call that a bilge keel. It is regarded as semi sacrificial and may be replaced if excessively scuffed or damaged. In the case of a Mirror it is placed directly beneath the edge ply forming the two side tanks.

    If you don't already have two internal floor battens, I'd add the second internally. It stiffens the floor a whole lot and prevents things like bad trolley supports putting a hole in and careless boarding by larger people...;) You don't need any screws or nails it will glue in place with weights and tape, just remove the internal varnish so it can grip good ply. One side at a time and it will not slide out of position if leant to natural angle ie to chine giving a horozontal floor, so all the curve is in a vertical plane.

    Note the current plans actually have two full length supporting floor battens. On these older ones just mimick the existing one and equispace it outwards, assuming the original is offset towards the centre which most are. BTW your hull looks in pretty good condition, how old is it? I know of one from circa 1969 still going strong....;)

    The aft protruding timber on the keel with hand hold in it is a skeg. Check yours is in sound condition as I have known these to get damaged on Mirrors.
     
  4. Justaguy
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    Justaguy Junior Member

    Confusion

    My apologies for any confusion, especially to SukiSolo: That photo isn't from my boat. It is just a random photo from the web. The only one that I could find with such a hull feature (slim pickin's not knowing what search term to use). I'll be clearer next time.

    However, the idea that these things (strakes?) would be (eventually) sacrificial conforms with my intention, which is that they would take any routine abuse from dragging the boat up on the beach, etc.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    A rubbing strake or a rubbing strip perhaps ?
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    A length of HDPE might make a good strip, what with its low-friction characteristics.
     
  7. Justaguy
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    Justaguy Junior Member

    Perhaps. In terms of additional functionality, this thing aids tracking (moving in a straight line), and might aid lateral resistance a bit as well. I'm thinking of a flat-bottomed boat here.
     
  8. Justaguy
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    Justaguy Junior Member

    Super idea

    I think that's a great idea, especially as this will not be a show boat. Purely functional (dinghy).

    Although a bit off-topic, now that you mentioned HDPE, if you (or anyone else) knows of any resources describing the use of HDPE sheathing on boat hulls (vs. entire boat made from HDPE), please add a comment. I've been looking and haven't found much.

    I did find one interesting reference to it, but only incidental with no details on the HDPE part as all:

    http://http://www.ankn.uaf.edu/publications/villagemath/fiberglass.html
     
  9. Justaguy
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    Justaguy Junior Member

    Thanks, SukiSolo, for another word to add to my personal boat dictionary (really, it's growing)! In the UK, maybe that term is used for more than one boat feature, but good ole' Wikipedia shows it to be a different thing (fin-like longitudinal gizmo) used primarily to prevent rolling ... which would make it a horse of a different color.

    http://en.wikipedia.org/wiki/Bilge_keel
     
  10. upchurchmr
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    upchurchmr Senior Member

    HDPE is great stuff for abrasion.
    But you can't bond it and expect it to stay on. You need to expect to screw it on.

    The PE is polyethelene and is almost impossible to bond with good strength.

    HD is high density.

    HDPE is very tough, heavy, and not very stiff. Not what I want for any kind of practical boat hull, in general. However, all the rota-molded kayaks are made from PE (not HD), but are heavy as a consequence.

    Good luck. All the nautical terminology is so we can have a "secret society" and look down on those different from us. Seriously, the special terms have the advantage of being specific to the needs of boats and more exactly describe the function - if everyone uses them right!
     
  11. Justaguy
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    Justaguy Junior Member

    Generally familiar with HDPE and its failings with regards to adhesives. Based on info from a vendor, 3M makes a specialty adhesive that they claim works on HDPE (DP-8005), but it costs about $30USD for a few drops.

    According to 3M's reply to me:

    "The DP8010NS (two part structural acrylic), 4693 (single part industrial plastic adhesives) and possibly our high strength 90 (aerosol contact adhesive ... our products are tested and we show all of these products have success on PE and HDPE. However, it’s your decision on which product to choose. Of these products our DP8010NS is going to provide the highest overlap shear strength."

    I knew it!

    ;)
     
  12. messabout
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    messabout Senior Member

    Just for fun, I'll describe the claimed origin of the terms Port and Starboard. As far back as the Hanseatic league, boats typically had the rudder mounted to the side of the boat not at the back of the boat. It was customary to mount the rudder on the right side of the boat near the stern (back end). No one knows why the right side was customary, maybe because Poseidon wished it so.

    The rudder was called a "steer board" because it was a flat board used for the purpose of steering the boat. The right side of the boat was the steer board side. That description became one word; starboard, which was always on the right side because Poseidon said so......The starboard side.

    When the boat came along side the dock or wharf, they docked in such a way that the left side of the boat was against the dock. They did it that way to avoid damaging the steer board (rudder) against the dock. So the left side of the boat was nearest the dock and it naturally became the "Port" side or the side nearest the port.

    Justaguy is right that boat folks talk funny. I mean we have things called kicking straps, spitfires, garboard strakes, and dorades.

    I think that the OP might be pulling our leg because he knew that the "runners", "bilge strips", " "skids", or whatever you choose to call them, also help the boat to track straight and/or diminish leeway.

    In any case, Welcome to the forum Justaguy.
     
  13. upchurchmr
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    upchurchmr Senior Member

    3M says that because they know you can stick it together, but they also know the strength will be low.

    Try something, compare it to a wood with epoxy joint and let us know how it compared.

    I'm willing to be wrong with some real experience. Learning its called :)

    "The DP8010NS (two part structural acrylic), 4693 (single part industrial plastic adhesives) and possibly our high strength 90 (aerosol contact adhesive ... our products are tested and we show all of these products have success on PE and HDPE. However, it’s your decision on which product to choose. Of these products our DP8010NS is going to provide the highest overlap shear strength."

    OBTW< I recently had a shock. I was gluing some 1/2" square struts to an epoxy coated surface with Titebond 2. I chose that because I was sure it would be easily removed. Fat chance, six feet down inside a kayak I had to try to cut them off the surface and damaged the hull. Just to show you I can be wrong!
     
  14. SukiSolo
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    SukiSolo Senior Member

    Well maybe the Wiki needs a bit of editing. However I will say that the term bilge keel, this side of the pond includes both the protective strip type (as in original photo) and full on twin keel (one each side) boats. Certainly this is well understood over here, in fact many dinghy classes refer to bilge keels in their rules and specify minimum dimension(s). The intent is that when on level ground a boat heels over due to shape she is protected on her bilge (shoulder or edge). On an offshore yacht I would expect two permanent shallow draft angled outwards ballasted bilge keels. Normally these yachts can sit on both keels in harbours and creeks which dry out at low tide, thus the yacht remains upright.

    Hope that clears things up.
     

  15. PAR
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    PAR Yacht Designer/Builder

    That's a rub strip and HDPE makes a good one, so does UHMPE and hardwoods. Plastics will expand and contract at a much higher rate than the wood, so elongated slots for the fasteners are necessary. Use small, short screws, preferably in bonded holes, so if you bash into something hard, the fasteners and rub strip pull off, rather than tearing up the bottom. Typically I'll use #6 screws on small craft, with just enough penetration to hold it in the bedding, but not much more. It's a lot cheaper to replace a strip and a few fasteners, then repair major divots and gashes from more substantial attachments.
     
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