Daggerboard Coating

Discussion in 'Sailboats' started by Herk_Man, Jun 16, 2015.

  1. Herk_Man
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    Herk_Man Junior Member

    Hi all,

    I'm finally getting around to making a new daggerboard for my 1969 Chrysler Barracuda. I'm making out of solid mahogany. Once I get it all shaped I want to coat it so it's waterproof.

    What is the recommended coating to use for something like this? Epoxy? Resin? Lacquer?

    Also, what would be the best way to protect the bottom of the daggerboard and the lower leading edge from grounding damage? I don't want a big ugly buildup and I want the daggerboard to be functional but still be a nice piece of woodworking.

    Any ideas welcome.
     
  2. rcnesneg
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    rcnesneg Senior Member

    If it was me, I would probably lay up the bottom tip with one or two pieces of woven fiberglass, and coat the whole board in epoxy, then apply Spar Urethane or something like that over the epoxy. If you're in a hurry you can just apply the spar urethane straight to the wood, but you give up the hardness and protection of the epoxy, and the thickness of the fiberglass on the tip to protect it, and you'll eventually have something expose wood under the urethane, which will need more urethane applied to the missing patch.
     
  3. Herk_Man
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    Herk_Man Junior Member

    Thanks for the response. I think those are great ideas. My one concern with the fiberglass is that I'll have an area on the bottom end of the board that is thicker than the rest of the board and that there will be a lip where the edge of the fiberglass is.

    I don't have much experience laying up fiberglass though so maybe I'm overestimating the thickness it would represent.

    Also, if I use the fiberglass as the protective layer on the tip, when I experience damage, how easy will it be to do a repair and retain the aesthetics of the woodwork?

    Again, thanks for the reply. Woodworking is no problem but waterproof coatings is something I don't have a lot of experience with and I want this board to look really nice.
     
  4. Herk_Man
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    Herk_Man Junior Member

    Also, when you talk about using Epoxy, do you use that to lay up the fiberglass? Or do you use resin to lay up the glass and then coat everything with the Epoxy?

    I'm assuming I can acquire Epoxy in large quantities for this application at West or a similar marine supply company?
     
  5. Jamie Kennedy
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    Jamie Kennedy Senior Member

    If the real thing don't do the trick
    You better make up something quick
    You gonna burn, burn, burn, burn, burn to the wick
    Oooo, Barracuda, oh yeah

    sorry. couldn't resist.

    I second the epoxy, and glass for the bottom tip. I would also get the wood nice and warm with even heat on both sides so the first layer goes on nice and smooth and gets sucked into the wood without the wood bubbling water vapour out into the epoxy. Normally I put it in the sun, and then apply the epoxy in the shade, but with two sides I would be sure to apply even heat on both sides and let it equalize a bit before applying the epoxy.
     
  6. Herk_Man
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    Herk_Man Junior Member

    Good stuff, Jamie. Any comments on my follow-up questions? I really appreciate you guys.
     
  7. Jamie Kennedy
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    Jamie Kennedy Senior Member

    West System has a lot of great documentation online on how to do stuff.

    Epoxy for sealing coat, and also for the glass layup. If you are glassing just the edge with a light glass cloth it doesn't add much thickness, especially if you are able to do the sealing coat and the glass at the same time as the glass can then sink down into the sealing coat. I would then let that dry and then sand it to remove that waxy coating. If you are happy with the fairness I would just add a final coat of epoxy and let that harden and sand it before applying the urethane layers. If you do see a bit of a transition from no glass to glass I would apply a thickened layer of epoxy using that colloidal silica and just a little talc to help break up the colloidal silica. Doesn't have to be too thick, just enough for you to apply a thicker layer without it sagging. It will still be hard and strong and not easy to sand to fair it, but it should be hard and clear, and thick enough for you to fair any remaining discontinuity from no glass to glass. You might also consider a thin layer of glass over the whole thing. Maybe do a trial run on a scrap of wood to see what you think of the clearness and discontinuity before you do the real deal.

    Important question. How thin do you want your trailing edge to be? The aim is always to have your airfoil curve trail off to a virtual point in space, and then square it off to 1/16" or 1/8" or 1/4". You can get the thinnest trailing edge with glass reinforced epoxy. If that is what you want I would fair the wood as thin and even as you can get it, and then square it off at 1/16" and then when you glass it have the glass just barely go past the wood, like maybe 1/2" at most, so it stays against the wood at the edge as it is setting. Then when it hardens square it off to maybe 1/4" past the wood, then do all your sanding, then maybe square it off again to a square edge of as little as 1/16" or perhaps 1/8" or however thick you think it needs to be for the abuse it might take.

    I've seen them pretty thin and still be strong, but if you are not racing I would say 1/8" is certainly thin enough. If you are happy with 1/4" then you may not need to glass it at all. Just two coats of epoxy and then your urethane coats. There is something to be said for keeping things simple. If you can do it in half the time, with less materials, you can make a second one if and when the first one wears out.

    That is my thoughts. I've worked some with epoxy and glass and wood and faired daggerboard, as seen a Finn rudder made this way described, but I have not made a wood and epoxy and glass daggerboard or rudder myself yet. Have fun with it. I look forward to comments from others.

    p.s. Regarding epoxy resin and polyester resin. There are a lot of advantages to working with polyester resin versus epoxy. It is cheaper. You can often work faster. It is less harmful to your skin when laying up, and less harmful to your lungs when sanding. It is also easier to sand. The downside is that polyester is not as hard, it does not adhere as well to most materials, and perhaps the biggest downside is that it does not provide as good a vapour barrier. Nonetheless some people have had a lot of success with polyester resin and glass over plywood. Good way to go if you want to do a lot of projects and experimental boats, and perhaps not the best way to go if you have put a lot of time and money into the rest of the boat. If you do go with polyester you can still give it a final coat of paint, or epoxy. You can apply epoxy to polyester, after it has hardened. You can't apply polyester over epoxy. Epoxy will adhere to polyester but not the other way around.

    On your project, where it sounds like you have made a nice board out of mahogany, like the original laser daggerboards, it would make sense to go with epoxy, two coats, with or without glass, and then 2 or 3 coats of spar varnish or urethane to protect the epoxy from the sun. Epoxy also gives a much clearer finish than polyester resin and the glass becomes almost invisible, so it will look like bare wood with 7 or 8 coats of varnish when you are done.
     
  8. Jamie Kennedy
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    Jamie Kennedy Senior Member

  9. Herk_Man
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    Herk_Man Junior Member

    Wow. The time you took to help me is humbling. I'll be sure not to waste it. When I get it done I'll post pictures. I'm also working with a woodworking store to identify something I can use to do an inlay of the Barracuda symbol in the handle of the daggerboard so that will take a little time. The symbol on the sail is black so I want to use ebony but that's a very hard wood and I'm not sure it will work. Going to be great when it is done though!

    Thanks again!
     
  10. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Thanks Herk_Man. The real work is what you will be doing. Look forward to seeing your pictures. Enjoy the work and sailing the boat when you are all done.
     
  11. SukiSolo
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    SukiSolo Senior Member

    Epoxy sheathing will give you the most durable finish. It will need a sealing coat first, and then a layer of (approx) 270 gsm roving or woven cloth for a decent covering which will add a lot of stiffness. This will need at least one more coat of epoxy, but after that I personally prefer to 2k paint in white. It protects the epoxy from UV and the board from heat and warping, as well as being easier to see weed on the board when sailing. Varnish is OK, but not as UV protective, you can also use just clear and polished epoxy throughout but note it will yellow quite a bit over time.

    The edges of the board especially the bottom and leading tip should be given a moderate thickness of an epoxy microfibre/sawdust/other hard filler mix. Relieve the wood to accomadate this prior to any epoxy sheathing and glassing. It is also useful to 'cap' over the glass so it does not lift if the barrier is penetrated. Also note that any through ropes for lifting should be made oversize, filled with an epoxy and filler mix, then redrilled to desired size.
     
  12. rwatson
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    rwatson Senior Member

    Umm - is this a windup ? "new daggerboard for my 1969 Chrysler Barracuda"

    When does a car have a daggerboard ?
     

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  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Most of the above advice is on target, though a thin coat of goo and fabric isn't going to add any real appreciable stiffness to the board.

    On a solid wood board, strip planking is the preferred method, so the thing doesn't warp, check, split, etc. Alternate the strips grain as you glue them together, to relieve potential internal stresses. Encapsulate the board with 2 or more coats of straight goo (especially the end grain), then apply the fabric. Dynel or better yet Xynole are much tougher choices than 'glass cloth and far better than CSM. The 270 GSM (8 ounce) weight is fine, though consider 135 GSM (4 ounce) in multiple layers for better abrasion resistance if using 'glass. A single layer of Xynole or Dynel is fine (roughly 8 ounce), as they're much tougher than 'glass.

    Lastly, it's often wise, particularly on daggers to make a "water stop" line and reinforce the trailing edge, in the event of impacts. When a dagger strikes something, it's driven backwards, into the case, which dicks up the trailing edge. The bottom also gets a beating. There's all sorts of ways to address these issues, from metal strips, to heavily reinforced epoxy (stone dust, polyester rope, etc.) edges, to something as simple as a sacrificial edge that can be easily replaced if bashed excessively enough to warrant it. These "water breaks" act to isolate the rest of the board from moisture intrusion, by separating the main body of the board from the likely areas to get the crap kicked out of them.

    I always preferred the notch back version of that body style Ray.
    [​IMG]
     
  14. tom28571
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    tom28571 Senior Member

    Quite a few years ago, I was faced with a daggerboard that kept getting dinged and worked our a solution that I find better than any that has been suggested.

    I passed it on to some others and, rather than try to describe it in words, here is a very good video of how to protect a foil by my friend Alan Stewart of B&B Yachts.
    https://www.youtube.com/watch?v=xydnwWe9x6w

    Allan has also made other videos on this site that are extremely helpful in building a boat in the stitch & glue method.
    www.youtube.com/user/mralanosauras/videos

    I have used this method to protect keel edges on larger boats that have survived hard hits on submerged stuff like old engine blocks used for mooring anchors in shallow creeks. There has never been any damage of a leading edge protected this way that I am aware of, including bow stems of racing dinghys that tend to hit things..

    One of Alan's videos shows a 44 foot power cat recently completed by B&B that also has the "rope trick" edge on the hull stems.
    https://www.youtube.com/watch?v=xFmf-1vDP1c
     

  15. tom28571
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    tom28571 Senior Member

    Alan does this a bit different from me but either works well. I don't find it necessary to heat the epoxy as it will do that in the cup on its own. Size of the rope depends on size of the job. I fill any gaps around the rope with filler and then sand fair. I also find that a simple flat on the nose of the board works as well as a groove and I like woven rope.

    If you want to know just how tough this epoxy soaked rope is, lay a bit of hardened line on the bench and slam it with a hammer, a big hammer. Its flexible enough to absorb a huge shock without visible damage.
     
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