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Thread: I'm finally building my boat.

  1. #31
    Quote Originally Posted by Malcolm Schweizer View Post
    . Actually it gets glassed below the waterline, and I would probably do extra coats above the waterline, but he wants you to put three coats of epoxy on every surface- inside and out. I think that's overkill when you are also going to paint it. One good coat of epoxy should seal most surfaces. The bilge would get more. That may change when I see how the wood soaks up the epoxy. It may take two and who knows- maybe three coats, but good grief that is going to be a lot of work. I'm hoping one coat will seal things up. She gets taped in all the seams around the seats, and fillets at all the joints in the strakes. Any exposed plywood edges would certainly get three coats, as those tend to absorb a lot, but I don't see the need for three coats on every single surface. I'm spraying it with AwlGrip primer and AwlGrip paint.
    Quality epoxy Gelcoat paint costs 3x-5x what the regular epoxy costs.... You want the bulk of the thickness which you sand off doing the leveling, filleting, and fairing to be the cheaper resin.... Once your cheaper resin is all good and leveled, smooth, and flat - you can paint on a much thinner film of expensive paint without massive waste sanding 75% of it back off to level it....

    Test it out on scrap wood to test out how it works. Include the filleting process...

  2. #32
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    Quote Originally Posted by andy bessette View Post
    No, it isn't and no, it won't. This is where builders get into trouble, thinking they know better than the designer.
    Actually another builder already ran it past him and he said you could go with fewer coats of epoxy and a quality paint, but keep it at 3 for the outside, which is what I'm doing.

    Quote Originally Posted by John C Cox View Post
    Quality epoxy Gelcoat paint costs 3x-5x what the regular epoxy costs.... You want the bulk of the thickness which you sand off doing the leveling, filleting, and fairing to be the cheaper resin.... Once your cheaper resin is all good and leveled, smooth, and flat - you can paint on a much thinner film of expensive paint without massive waste sanding 75% of it back off to level it....

    Test it out on scrap wood to test out how it works. Include the filleting process...
    Now this is actually a better reason for more coats of epoxy. Our local chandlery was letting go of AwlGrip primer for $50 a gallon for part A, which skews the math, but otherwise you are right. I actually didn't believe it until I got to the checkout and he rang it up. I was waiting for the guy to say, "Oh, this is a mistake," and I made sure I quickly paid and ran out of the store before someone said the price was wrong! I will see how it goes after the first and second coat of epoxy. I'm not looking forward to doing three coats of epoxy on the inside with all the frames and stringers to paint around. They are all going to be filleted and/or taped (taped at all the seat box bases and at the lap joints on the bottom, filleted at the stringers) so this isn't a strength issue. I may do two coats and say, "Okay, I was wrong, this needs another coat." I'm hoping no more than two. I love rolling epoxy on smooth kayak hulls or surfboards, but painting in nooks and crannies around ribs and stringers is not my idea of fun.

  3. #33
    Quote Originally Posted by John C Cox View Post
    ... You want the bulk of the thickness which you sand off doing the leveling, filleting, and fairing to be the cheaper resin...
    Not exactly.

    You don't want to sand off ANY of the 3 barrier coats of neat epoxy. Over those coats you would apply an epoxy coat thickened with microballoons and colloidal silica. This, and high-build epoxy primer, is what you can mostly sand off, leaving the barrier coats intact.

    Recommended reading is "The Gougeon Brothers On Boat Construction."
    "Anything seems possible when you don't know what you're doing."

  4. #34
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    Quote Originally Posted by andy bessette View Post
    Not exactly.

    You don't want to sand off ANY of the 3 barrier coats of neat epoxy. Over those coats you would apply an epoxy coat thickened with microballoons and colloidal silica. This, and high-build epoxy primer, is what you can mostly sand off, leaving the barrier coats intact.

    Recommended reading is "The Gougeon Brothers On Boat Construction."
    Although it can be done this way, there are issues here in regards to glued lapstrake: (1.) You should not have to skimcoat a well-made lapstrake hull with fairing filler. Fill a few screw holes and fix a few dings, maybe, but if you properly epoxy coat then you don't need to put a fairing coat over the whole boat. (2.) There is no problem with sanding between coats if you let the epoxy cure between coats. In fact, only if hot coating should you not sand between coats. (3.) Why build up an imperfect coat and then spend even more time and money with another coat over that? Sand between coats and if it's not thick enough, add another coat. That said, I do understand the train of thought of wanting to hot coat over green coats of epoxy. It isn't inherently wrong. Hot coats in theory will get a chemical bond, (in theory because there is a short window in many cases where that can happen) but I can tell you from countless builds that it is perfectly fine to let the coat cure and sand between coats. For multiple layers of cloth I put them on while the first layer is still green, but for a sealer coat there is no real need to do hot coats. Sanding between coats will yield a smooth hull without a bulky and complicated fairing coat.

    For cold moulding and strip building the skim coat may be more necessary, depending on how fair you got the hull prior to coating. My above comments are for glued lapstrake hulls with Lloyd's okoume or similar ply.

    Lots of glued lapstrake hulls are bright finished.
    image.jpeg

  5. #35
    I can go for the idea of Kevlar on the bottom, particularly in your area. I wonder though, if you need the carbon fiber in there, as it will not add to the structural integrity of the structure as described but it does add to the cost. One of the axioms of sandwich laminate construction is that you can have the load borne by the skins or by the core but not both. The failure mode of your "laminate" will be dictated by the "core" planking. And it won't add measurably to stiffness, because your "skin' is too thin to afford any stiffening. If you were to apply three or four layers of the Kevlar/Epoxy, you would change things, but you'd also add so much weight that you might well sail like a garbage barge. You may find that Kevlar alone is enough cheaper than the Kevlar/Epoxy to make the change worthwhile.
    Fair winds and following seas,
    Jim Waldron

  6. #36
    Quote Originally Posted by Malcolm Schweizer View Post
    ...There is no problem with sanding between coats if you let the epoxy cure between coats...
    Actually there is no need to sand between coats if you recoat before the epoxy is fully cured. Simply wash off the blush with water. It's OK to lightly scuff up the previous coat using Scotchbrite to knock off any debris. Sanding between coats reduces the thickness and effectiveness of the previous coat, which can be sanded through.

    Recommended reading: "The Gougeon Brothers On Boat Construction"
    "Anything seems possible when you don't know what you're doing."

  7. #37
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    Quote Originally Posted by James Waldron View Post
    I can go for the idea of Kevlar on the bottom, particularly in your area. I wonder though, if you need the carbon fiber in there, as it will not add to the structural integrity of the structure as described but it does add to the cost. One of the axioms of sandwich laminate construction is that you can have the load borne by the skins or by the core but not both. The failure mode of your "laminate" will be dictated by the "core" planking. And it won't add measurably to stiffness, because your "skin' is too thin to afford any stiffening. If you were to apply three or four layers of the Kevlar/Epoxy, you would change things, but you'd also add so much weight that you might well sail like a garbage barge. You may find that Kevlar alone is enough cheaper than the Kevlar/Epoxy to make the change worthwhile.
    I was just doing a single layer of carbon/Kevlar weave where they blend both into one cloth. I do understand that the carbon will be running one way and the Kevlar the other. It is still stronger and more abrasion resistant. I'm not looking for huge increases in strength, but it is nice to get the advantage of abrasion resistance. The other option is to glass it and then put a thin layer of Kevlar felt. This will be smoother, but heavier. The good news is it's weight below the waterline. It is only glassed below the first strake. Plans call for one layer of 6oz glass. I am doing one layer of carbon/Kevlar blend.

    I think I said it before, but for anyone reading this, using carbon fiber doesn't make the boat lighter- it will make it heavier for the same weight of cloth. 6oz carbon cloth is thicker than 6oz fiberglass cloth. It will therefore hold more resin. If building with carbon, you can reduce the cloth weight by 40% and get the same strength if looking to reduce weight. That's not my intention. I just want abrasion resistance of Kevlar and added strength of carbon. I'm using the same weight cloth so I will ultimately have a beavier end result than fiberglass, which I am fine with. I am adding a small cabin and slightly heavier centerboard, so I want the extra strength. I will be beaching in sand a lot and want the abrasion resistance of Kevlar.

  8. #38
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    Quote Originally Posted by andy bessette View Post
    Actually there is no need to sand between coats if you recoat before the epoxy is fully cured. Simply wash off the blush with water. It's OK to lightly scuff up the previous coat using Scotchbrite to knock off any debris. Sanding between coats reduces the thickness and effectiveness of the previous coat, which can be sanded through.

    Recommended reading: "The Gougeon Brothers On Boat Construction"
    That is what I meant by "hot coating"- recoating before it is fully cured. That is fine. I'm not being argumentive here, but I have over time gravitated to letting it cure and sanding between coats. It gives you a glass smooth finish. Yes- you have to be careful not to sand through, but sanding should just be a quick hand sanding with 220. If you feel it took too much off, add another coat.

    There are as many camps on this as there are on sharpening.

  9. #39
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    Ok my percentages are way off, I'm not surprised, I had little to go on, never having built a boat, (just a canoe). And I am not planning to, furniture is my thing. Was just hoping to help you plan. So yours looks more like;

    60% hull, mast and spars (including for some materials you already have)

    20% sails and rigging (I'm thinking you will want a little more than you estimate now; spare, stowage, lines etc.)

    20% engine and electrical (Allowing for some electrical and maybe fire protection)

    0% communications and tech (you already have a cell phone and will sail by eye)

    Getting the financial issue in view and hopefully within reach is a big step. Now, back to the shop!

  10. #40
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    Quote Originally Posted by Tom Bender View Post
    Ok my percentages are way off, I'm not surprised, I had little to go on, never having built a boat, (just a canoe). And I am not planning to, furniture is my thing. Was just hoping to help you plan. So yours looks more like;

    60% hull, mast and spars (including for some materials you already have)

    20% sails and rigging (I'm thinking you will want a little more than you estimate now; spare, stowage, lines etc.)

    20% engine and electrical (Allowing for some electrical and maybe fire protection)

    0% communications and tech (you already have a cell phone and will sail by eye)

    Getting the financial issue in view and hopefully within reach is a big step. Now, back to the shop!
    I would say somewhere along those lines. I got a great price on the centerboard so far, and I know the cost of sails and engine. I delayed buying the sheet goods because I've made some changes as far as what will be bright finished and what won't (bright finished will be ribbon stripe sapele, painted will be Oakoume). I'm also strongly considering changing the floorboards to solid wood planks instead of ply. I have to sit down and calculate the weight change there, but on this hull the floorboards are actually a few inches below DWL, so although weight addition isn't a good thing, at least it's not above DWL. Asking designer for feedback before I finalize my order.

    This is the dilemma of building boats on an island- you can't just run to the store and get more of what you need, because most of the materials have to be shipped. They only stock doug fir marine ply on island. Actually, part of my thoughts on switching to a planked floor is because I can get cumuru locally, and in fact my friend just gifted me enough to do the floors in this boat. It's heavy stuff, and I have to do some math and see how much weight that will add versus sheet ply. There isn't much floorboard in this boat, so I don't really think it's a huge deal, but since I'm adding a cabin and raising the coaming, it all adds up. Floorboards are loose and not structural in this design. Shipping sheet goods and long lumber is not cheap, so I want to be sure I ship everything in one go. I am going to intentionally order a few extra sheets of ply and a good bit more spruce than I need. I can always use spruce.

    As for communications and tech, I'm putting a very good DSC VHF tied to the GPS, and am leaning towards the Raymarine Dragonfly Pro 7 with the new CHIRP sonar. The main reason for wanting a chartplotter is marking my secret treasure hunting spots, and will also use it to log speed and other data. I want the CHIRP for exploring dive sites- just to play with it mainly- but I do want some sort of sounder for places like Anegada where a boat like this is perfect for exploring wrecks on the reef, and you want to keep an eye on your depth even in a small boat like this when the centerboard is down. LOTS of old wrecks there that are yet to give up their treasure!!!! I will have a small flexible solar panel to top off the battery and the Tohatsu 6 propane outboard has a charging circuit if needed, although I doubt it will be needed. I am waiting until the whole hull is built to determine where and how much space I can put a solar panel, but just a small flexible panel or two, like 50 watts.

    Centerboard was taken to Tropical Shipping yesterday, and hopefully will arrive in a week. I have upcoming travels, so don't expect a lot of progress too soon. I will work on shaping the centerboard a bit at a time, and will be building the rudder components while I wait for the ply to arrive.... which I'm ordering tomorrow... or maybe the day after tomorrow. :-) Also the spruce for the spars will come from the same place- Boulter Plywood in MA. When it all arrives, things will move along much faster. Plans already lofted to plywood patterns, so I will quickly be able to trace and cut the station moulds.

  11. #41
    I'm sure you already know that the cumuru is not only very heavy, it's also very, very stiff and very, very strong. If it doesn't have to span a ridiculous length in your cockpit, I'd suggest you look into thinning it down to 5/8 inch, maybe less. That would save a lot of weight - and look good in the process.

    Remember, you've got to keep the weight down enough to handle the burden of all that gold on the sail back from Anegada.

    Bon voyage indeed!
    Last edited by James Waldron; 08-29-2018 at 1:35 PM.
    Fair winds and following seas,
    Jim Waldron

  12. #42
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    Quote Originally Posted by James Waldron View Post
    I'm sure you already know that the cumuru is not only very heavy, it's also very, very stiff and very, very strong. If it doesn't have to span a ridiculous length in your cockpit, I'd suggest you look into thinning it down to 5/8 inch, maybe less. That would save a lot of weight - and look good in the process.

    Remember, you've got to keep the weight down enough to handle the burden of all that gold on the sail back from Anegada.

    Bon voyage indeed!
    Funny you mention it- I posted on the John Welsford page for input, and someone reminded me that Cumuru doesn't float. Although I doubt I would get into a situation where the floorboards would be falling out, I may want to rethink cumuru. I did some rough math and got about 20 to 25 pounds added weight, but that didn't factor in the gap between boards. I may do some tests and see how flexy it is at various thicknesses. The other option locally available is mahogany.

    I would gladly toss the floorboards if needed to make room for the gold. :-) One of the criteria when I was searching for a boat design was it had to be a good platform for wreck diving- obviously on a very small scale- something that wouldn't be too tippy with a diver and gear sitting on the gunwales. It's one of the wonderful things about living here- lots of history, and lots of cool stuff to find, although by "cool stuff" I mean things like pottery shards, cannon balls, pewter spoons, and things with little monetary value, but just cool to think about the history of, and fun when you find one.

  13. #43
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    John Welsford (the designer) responded that there would be no issue with using cumuru- negative buoyancy would be minimal compared to plywood. Here is an image of a similar sized boat by David Tolan showing what I'm wanting to do, except I want to copper rivet the longitudinal boards to the crossmembers... just because I like copper rivets for looks and function. The 6M Whaler has bouyancy chambers under the seats, but is a similar sized boat to this one. I'm leaning towards cumuru over mahogany because of rot resistance and strength.

    Wood Floorboards.JPG


    By the way, I share all this stuff for the person who may be considering building a small boat so you can see my whole process and my reason for any changes. In this case the reasons are: Materials available locally (and in this case gifted to me at no cost), better traction, any water easily drains to the bilge, and it looks nice.

  14. #44
    You'll already be overweight for the design. It is not too soon to become weight conscious.
    "Anything seems possible when you don't know what you're doing."

  15. #45
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    Quote Originally Posted by andy bessette View Post
    You'll already be overweight for the design. It is not too soon to become weight conscious.
    I do not disagree at all. If I were not adding the cabin and raising the coaming, I wouldn't have even thought twice about the added weight in the floor. That's why I ran this one by the designer, who knows my plans. I'm making a birdsmouth spar that will save some weight aloft (also approved by the designer- in fact, he gave me the recommendations for thickness of the staves). Certainly things add up quickly in this process even in such a small boat.

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