Making bottom of boat scuff resistent

Discussion in 'Boatbuilding' started by 300wm, Dec 10, 2015.

  1. PAR
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    PAR Yacht Designer/Builder

    Agreed, I haven't seen a table top that was worth a damn. If it's the "Crystal Clear" I think it is, this is a urethane casting resin and not very suitable for your needs.
     
  2. 300wm
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    300wm Junior Member

    What would be a good choice that is friendly on the wallet? Just remember, this boat will never see larger rocks or go down streams where I'd need a fiberglass bottom. It's just to keep from touching up nicks every time I launch from the beach. Paint nicks is ok, but nicks that get to the wood is what I want to try to keep at a low.
     
  3. 300wm
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    300wm Junior Member

    I used to work at a prison where they recoated the mess hall with epoxy that had to be cleaned with acetone (I remember the acetone containers everywhere). After 2 years and 700 inmates going through the doors 3 times a day, the floor had no wear marks. What product would be like this?
     
  4. 300wm
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    300wm Junior Member

    Par, is there any way to determine where the seat of the yak I'm building will go without having to put it in the water to get a 'floats level here' mark? 18' long and dimensions 9' to middle are exactly the same fore and aft. The sides will be 10" high in front of the coaming and the coaming will slant to 8" in the rear, so we're talking 3 lbs lighter from middle to rear, including the 2" shorter bulkheads.
     
  5. PAR
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    PAR Yacht Designer/Builder

    So, you want bullet proof, but cheap.

    No, without a set of lines and hydrostatics for the hull and the loading condition you desire, there's no guessing at where the seat or LWL will be, without launching the puppy and physically moving your butt around, until you find the spot you like.
     
  6. 300wm
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    300wm Junior Member

    Of course...I'm American. ;)

    OK. Float test no big deal.
     
  7. 300wm
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    300wm Junior Member

    Last question (I hope). Would 3M fiberglass resin (sold at Walmart) work for what I'm asking? It has a short pot life, but at this point, I'm willing to do small areas and just overlap, then sand even. $37 for everything I need to do two coats to entire bottom and sides.
     
  8. PAR
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    PAR Yacht Designer/Builder

    I'm fairly sure your looking at polyester resin, not epoxy. Huge difference and not well suited for your needs.

    [​IMG]

    Is this the stuff?

    [​IMG]

    Or is this the stuff, which is a discontinued product. Both are polyester resins and yeah a little cheaper than epoxy, but also grossly weaker in every regard too.
     
  9. 300wm
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    300wm Junior Member

    Yes, the first one.

    Let's get price out of the picture. What can you recommend that will stick to wood and be good to paint over? I'm only doing 38 sq. ft., and that's two coats, so I really don't need a lot of it.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Just get a couple of quarts of RAKA, Marinepoxy, Progressive or other discount goo and apply as many coats as it will permit. Three is the minimum, but without a fabric, you're not going to gain much, but a hard plastic coating, which without the additional toughness of a saturated fabric is limited at best.
     
  11. 300wm
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    300wm Junior Member

    I'm going with a thin resin/slow cure RAKA kit. I liked your articles on epoxy (best out there, BTW, by far...you know your stuff) and how the epoxy won't help wood strength by itself, but with softer wood, it could give 'some' strength. That's EXACTLY what I'm looking for...a tough, thin barrier on the soft wood I'm using that will resist minor abrasions when dragging on the beach sand or in my yard.
     
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  12. PAR
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    PAR Yacht Designer/Builder

    Again, the epoxy will add a modest amount of toughness to most softwoods, but not a lot, if the resin is unthickened. To this end, you can add stuff to the resin, to improve it's toughness, though if you want really tough, without fabric, sanding it smooth will be difficult (understandably). Milled fibers and/or carbon or graphite and/or silica in the mix will make a much tougher coating, but (again) will also be a bear to sand smooth, because of the toughened resin.

    Thin resins are great for wetting out fabrics, but they also apply a skinny coating, so you'll need more to get the film thickness necessary. As an example, a 6 ounce cloth, applied with West System 105/205 will only need a single over coat to fill the weave, but RAKA (comparatively) will need two over coats to fill the weave.

    If it was me, I'd use a modest amount of milled fibers and silica, mixed to a runny cream consistency and I'd smear this all over the boat's bottom with a squeegee. I'd try to get this coating as consistent as possible to ease some of the smoothing and fairing effort later.
     
  13. 300wm
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    300wm Junior Member

    Thanks...I will do a couple test pieces when the RAKA arrives and see if I will really need it. I'm gonna try 3 coats (without the silica) per your suggestion, first, on a piece of the ply glued to the bottom of a cinder block and drag it down the road 20 or 30 yards, after it cures. If nothing gets to the wood, I'll go with that. Not worried about sanding, too much. Was a grunt in a body shop for years, so I have all kinds of sanding equip and fairly hefty compressor.
     
  14. Pericles
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    Pericles Senior Member

    Question on William the Conqueror's day in Anglo Saxon England.

    Which is worse, paying too little or paying too much?
     

  15. Tungsten
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    Tungsten Senior Member

    Raka has 2 kinds of resin,off the top of my head 127 is the laminating resin,631 maybe is a much thicker one.I've tested several brands in the same way, ie dragging weighted ply down a gravel road.

    Un thickened epoxy grinds off pretty quick,wood flour,micro fibers etc greatly increases its toughness.
     
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