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Thread: Advice Needed: Finishing Stitch & Glue Hull

  1. #1
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    Default Advice Needed: Finishing Stitch & Glue Hull

    Howdy folks. I'm just about at the point on my Pelicano 23CC build where I need to order the materials to finish the hull. I'm looking for some advice on both the order of steps and recommended materials - primer / paint / etc.

    First up is the order of steps. I've been sanding and fairing and sanding for days (using TotalBoat fairing compound, torture boards, power tools, beer, and swearing), and I've got the exterior about as smooth as I'm likely to get it. I think the next steps are to clean the hull, apply fiberglass & epoxy, then prime / sand / paint. Obviously that's a very generalized summary, but I'd like some feedback to make sure I've got the order of steps correct.

    Next is material recommendations. I watched a video online recently of a guy applying an Alexseal product that turned out really well - but I have no opinions one way or the other about marine paint brands. I'm planning to brush / roll myself, and I'm not a professional by any stretch. I don't expect things to turn out like a yacht, but I do take pride in what I do. All of which goes to say, I'd like opinions on what to use that's likely to give a reasonable finished product considering it's built and painted by an amateur in an oversized garage working solo. My plan is to paint a light color, since I've read that dark colors tend to show blemishes more, and I have no illusions about my sanding/fairing skills. Boat will spend most of its life in fresh water (at least as long as I own it), likely on a trailer or in a sling, but possibly in the water year-round.

    Thanks in advance for your input.

  2. #2
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    You seem to be missing a course of sanding between "apply fiberglass and epoxy" and "prime/sand/paint". Epoxy is not paint and does not go on as smoothly as paint does. If you just prime and paint over it without filling the cloth weave and sanding that smooth first, it ends up looking awful.

  3. #3
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    There's a million different ways to do it, and here's my thoughts....

    I'd use peel ply when you glass the hull, makes the final sanding so much easier before you paint. Any amine blush sits on top of the fabric, which you peel off and throw away once the epoxy has cured. You've then got the choice of single pack, or two pack paints. Single pack is cheaper and easier to apply, but less hard-wearing than 2 pack.

    Most manufacturers I've seen suggest 3 coats of primer below the waterline, and 2 above. Follow this with 2 coats of topcoat. If you're keeping the boat in the water you may need to antifoul, if you do then I'd put a tie coat between the primer and antifouling.

    Supplier wise- depends where you are. In the UK we have the big names such as International, Jotun, Hempel etc and smaller firms such as Teamac, SML etc.

    On my own boat, I'm going for 2 pack on the hull, and single pack on the rest. Below the waterline will be 3 coats of 2 pack primer, a tie coat, then antifouling.

  4. #4
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Quote Originally Posted by Todd Bradshaw View Post
    You seem to be missing a course of sanding between "apply fiberglass and epoxy" and "prime/sand/paint". Epoxy is not paint and does not go on as smoothly as paint does. If you just prime and paint over it without filling the cloth weave and sanding that smooth first, it ends up looking awful.
    Thanks, Todd - that's actually what I meant when I mentioned "a very generalized summary." I know I left a few steps out - was just trying to keep the post short.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Personally, I never prime over sanded epoxy. If it is properly applied and sanded, epoxy resin should be very smooth and fair and it is probably going to be a better primer all by itself than most primers.

  6. #6
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Quote Originally Posted by Todd Bradshaw View Post
    Personally, I never prime over sanded epoxy. If it is properly applied and sanded, epoxy resin should be very smooth and fair and it is probably going to be a better primer all by itself than most primers.
    That's interesting. What got me started down this rabbit hole was reading the various manufacturers' application instructions for their products; they all talk about how well their stuff prevents gelcoat blisters by keeping water from getting between the resin and the hull. I thought exactly what you just said, more or less: "I thought epoxy was supposed to be waterproof? What am I missing here?" Couldn't find much info on prepping and painting a bare wood hull that had been epoxied and glassed. I'm sure it's out there, but I haven't found it yet.

  7. #7
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Gelcoat blisters have nothing to do with epoxy resin. They are found on hulls made with polyester or occasionally vinylester resins - a very different kettle of fish. I originally quit messing with primer on epoxy at a recommendation from the techs at Gougeon Brothers, also mentioned in their book. It's hard to find anybody on the planet with more experience using epoxy on boats than the guys who developed WEST Epoxy and most of the techniques used for wood/epoxy boatbuilding.

    From their book (possibly with a couple of strange little bits tossed into the type by the text copy program)

    Primers
    We find that we rarely need primer paints when we
    coat hulls with WEST SYSTEM epoxy. Primers can’t, of
    course, be used on naturally finished hulls, but even on
    painted surfaces, they don’t seem to result in any particular saving in finishing time.
    Primers are not usually needed to help bond a paint
    film to cured WEST SYSTEM epoxy. Most finish coatings
    readily adhere to a clean and well-sanded epoxy-coated
    surface, although interfacing primers are required with
    some specialized bottom paints. If the instructions on
    your paint or varnish recommend a specially primed
    surface, sand your epoxy coating until it is no longebr /> glossy or shiny and follow the directions given for fiberglass preparation.

    Test the product in an inconspicuous
    area to be sure that it will bond to epoxy. If any product
    fails to dry within the period specified on its packaging,
    try a different brand or use a primer.
    Primers are sometimes used to make sanding quicker.
    The theory is that they are easier to sand than epoxy;
    while this may be true in some situations, you must
    weigh the benefit against the time needed to apply the
    paint and to achieve an even surface. Since primers are
    difficult to apply evenly with a roller or brush—because
    of the safety issues involved, we can automatically rule
    out spraying primer paints—application time may well
    exceed any extra epoxy sanding time. Primers definitely
    do not flow as well as WEST SYSTEM epoxy, so you need
    a good deal of sanding just to get the primer as smooth
    as the original rough-sanded epoxy surface.
    A colored base coat will facilitate final fairing by serving
    as a guide to prevent over sanding and will also, to some
    extent, reduce the number of coats of paint needed to
    cover an unpainted surface. When we plan to paint a
    hull, we therefore often add WEST SYSTEM pigment to
    our final coat of epoxy and use this instead of primebr /> as a tracer coat.


    Nothing is absolutely waterproof forever, but epoxy is pretty close for all practical purposes. As for examples of wood plus epoxy plus a finish with no primer, how about the thousands of wood strip/fiberglass canoes with varnish or paint over the epoxy? No primer in use.

  8. #8
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    You can, however, use epoxy resin for the repair of gelcoat blisters on fiberglass boats. This old gal had lots of them, as well as holes in the hull where the support pads had broken through the bottom from years of sitting on the trailer full of water. I patched the holes, sanded down the gelcoat and coated the hull with one coat of plain WEST Epoxy, followed by five more coats of epoxy mixed with barrier coat aluminum flake powder, which resists water intrusion even more. Then it got sanded smooth and painted with Brightside enamel, rolled and tipped, and Hydrocoat ablative bottom paint below the waterline. When this pic was taken it had been sitting out for three years and had spent the previous season out on a mooring buoy. It was in for spring clean-up.

    nordica.jpg

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Quote Originally Posted by Todd Bradshaw View Post
    Personally, I never prime over sanded epoxy. If it is properly applied and sanded, epoxy resin should be very smooth and fair and it is probably going to be a better primer all by itself than most primers.
    That probably depends on the paint being used as well.... There were a few spots I didn't prime as thick on my son's canoe and the red awlgrip paint I used was very translucent and ended up taking a lot more coats than it should have to hide the thin spots in the primer, I imagine that the variance in epoxy/glass/core/fairing compound would be even worse for the translucent colors than the couple of thin spots of primer were for me.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    You said you intentionally left out some details, but a few that I didn't quite realize at first:

    1. Unless you really can't do it, you want to get the fill coat on after the initial coat that wets out the glass within the chemical bond window -- that varies by epoxy manufacturer, but is on the order of a day or so (some say you can still get a chemical cure within a few days, I think). The problem is, if you go beyond that, you're in a bit of a pickle: in all other situations, you'd just wash (if needed, for amines) and sand (to create a rougher surface for the next layer to make a physical, not chemical, bond), and go about your way. But if you sand before you've filled the weave of glass, you're going to cut into the weave, weakening it. For that fill coat, adding a little bit of lightweight thickener (glass bubbles, etc) can make it a little easier -- the strength is from the glass, you really just want to get _above_ it, and it'll make it run less and be easier to sand later. There's no reason why there can't be a _single_ fill coat (something I didn't realize at first).

    2. Between finishing the epoxy and starting the paint, you really want to give it a bit of time. Again, this probably varies by manufacturer, but if it hasn't fully cured, you're likely going to be in for a bad time. I _think_ a week (given ideal curing conditions) is probably safe? Others with more experience would know better, but it's a bit of time.
    Daniel

    Building a Campion Apple 16.

  11. #11
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Yes, it is very wise to plan your glassing day to be a long one, and to get at least two or three filler coats rolled on top of the cloth to yield at least a minimally textured surface before you call it a day.

    Another thing to keep in mind is that some epoxy-based fairing compounds and some high-build primers contain microballoons as one or all of the thickening agents. So, you apply them, let them cure/dry/harden and sand the surface to a nice fair, ready to paint smoothness. However, when you sand microballoon fillers or primers the process tends to cut some of the balloons on the surface open, leaving extremely tiny (basically invisible) air-filled craters. Then when you paint the boat, the paint will usually bridge the open craters and look just fine. But.....depending on the paint used, it is not uncommon for the surface to heat up in the summer sun, expand the air inside the craters and cover your hull with little (and visible) pinholes in your formerly lovely paint job. I even had one canoe with a two-color paint job and a fair amount of microballoon filler where one color pinholed like crazy and the other did not at all. I assume the density difference between the two pigments was the reason, as they were the same brand of paint, just different colors.

    The lesson learned was that after fairing with microballoon/epoxy mixtures, the best procedure is to roll on one more coat of plain epoxy to cover the craters, give that a quick final sanding and then paint. The resin is strong enough to prevent the surface from pinholing.

  12. #12
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Daniel - thanks for the tips. As I mentioned, I'm mostly working solo, so I do have to plan my epoxy work carefully. I can recruit a teenager from time to time, but they make me pay for it. Gotta use them sparingly. The plans call for several layers of FG tape at the joints, all installed wet-on-wet, followed by the wide cloth over the entire hull. I'd love to get all that done - including the subsequent fill coats - in one go, but I doubt I can pull it off. It'll probably end up being a two-day deal where I can work all day Saturday, putting the last coat on late in the day, and all day Sunday starting first thing in the morning. Per my epoxy supplier, I've only got between 4-8 hours to re-coat - so I may be applying at midnight and again at 8am .

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    I guess I could limit day 1 to installing the layers of tape at the seams wet-on-wet. Then I'd only have to sand & wash the seams prior to installing the remaining glass cloth, which I should be able to install and fill-coat all on the same day.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    And waiting a week or more to paint is no problem. After two or three straight days of epoxy and fiberglass I'm going to be ready to take a nice long break.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Have a look at using peel ply- not saying its magic but it saved me a load of work . WEST have videos on youtube on its use. I used it on mine - basically you wet out the glass cloth as you normally would. You then apply a layer of peel ply which you then wet out. This fills the weave if the glass cloth, and because of the texture of the fabric, leaves a surface ready for finishing, no (or very little) sanding required. Once the epoxy has cured- you rip off the peel ply and you're ready to go. I had a few spots of filling/fairing, but not a significant job.

  16. #16
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    I put on a coat of primer in large part because it shows all the flaws that are invisible in clear epoxy/glass. I'm always astonished at all the nasties that pop into view.
    -Dave

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    I was taught that primers are not just about adhesion, which they do, in some situations, not necessarily in others, but more so they are about getting a uniform undercoat. This helps the top coat maintain a consistant color.
    If your undercoat is a consistent color, you'll need fewer top coats to cover it...?
    Just another 2 cents.

  18. #18
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Per my epoxy supplier, I've only got between 4-8 hours to re-coat
    What is the context of this? I think your supplier is full of it. I'm not an epoxy supplier, but I did go to college to learn how to use it (sculpture major working with both epoxy and polyester resins followed by a lot of work on boats) and have 50 years of experience using the stuff.

    If it has to do with amine blush, blush can be removed with nothing more than plain old water and a Scotchbrite pad if you had to wait long enough between coats for blush to form. As we mentioned above though, you want at least enough filler coats on the fresh cloth weave to smooth the texture out at least somewhat (the more, the better) as it's hard to remove blush from down inside the weave. The Scotchbrite and water wash down is a pretty good idea any time the resin has been sitting for an extended period between coats. Whether it blushed or not, there may be something that settled on there that you don't want on the boat.

    If the context has to do with maintaining a good chemical bond, don't sweat it. First of all, additional epoxy sticks to pretty fresh epoxy very well whether there is a chemical bond or not. You just need to keep it clean and remove blush if there is any. If you just do that, delamination between epoxy layers is extremely rare, even on impact. Secondly, most epoxy resins can still achieve some sort of chemical bond up to a week after the first coat was applied.

    It is also seldom required to sand epoxy between coats - as well as being not good for your health. It is a very good idea to give epoxy about a week to fully cure before sanding it. Otherwise you are risking getting sensitized (allergic to it) and at that point you would likely be done working with epoxy for life.

    One thing I always suggest for large epoxy projects like glassing a hull is to find somebody who can count, measure out, and mix you a steady stream of batches of resin. That is their only job, and your job is the application. The number of epoxy application failures we have seen on this forum over the last twenty years is quite substantial and most of them were due to mixing errors where one person was trying to mix resin and apply it at the same time alone. Fixing those mistakes is an absolute pain in the ass and also very expensive. Cloth saturation is also easier with freshly mixed small batches of resin, as it will already be in the process of thickening up in the pan as you work. The thicker it gets, the harder the job is to do properly.

  19. #19
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    I completely agree with Todd on having a second person to mix and feed you epoxy. I had this when I did mine - an 18' x 8' beam motorboat took 2 of us about 7 hours. As soon as I had a batch in my hand - the next batch was starting to be mixed. I hadn't glassed a hull before, but it went fine. I had the cloths cut to size as well, which saved time on glassing day.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    you have not BEGUN to sand

  21. #21
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    wizbang - yep, I know. I knew when I started that I'd give up on sanding long before I pro would.
    biglad - I agree. I have a teenage daughter who makes epoxy jewelry, so I'm sure she's capable of performing the mixing task.
    Todd - good info, thanks for sharing. I thought 4-8 hours seemed like an awful short window, but what do I know?
    Jbradym - makes sense that a similar-colored undercoat would make topcoating easier.
    Woxbox - that's one of my goals, too - to make it easier to spot areas that need more fairing/sanding. I have a hard time seeing those areas on bare wood, plus which the hull takes up most of my shop, meaning I can't get far enough away to see the whole thing at once. It just seems like a white or light gray coat would make it easier to see high & low spots.

    Thanks again to all of you for your input.

  22. #22
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    So far, I haven't had any problems with color consistency when painting enamel over sanded epoxy with no primer - and some of them were very irregular in color underneath, with areas of new wood, old wood and various fillers all showing. I suppose you could always try a test spot or on scrap to see if there is going to be a problem. This one was one of the most "multicolored" examples (6 oz. cloth over old wood and a lot of filler with WEST 105/205 epoxy). The paint is Ace Hardware polyurethane floor enamel, two rolled and tipped coats. If any colors would be likely to have show-through irregularity problems, I would think this pale yellow would be among them.

    guide 007.jpg



    The Star also had six ounce cloth and WEST Epoxy over sanded old wood on the bottom and the iron keel was "primed" by disk grinding, then "wet-sanding" it using WEST 105/205 for the wet component (not a particularly fun project, but it gets the stuff on before it can start to oxidize) then coating and fairing with more epoxy and microballoon filler mixtures. Then both bottom and keel got two coats of Brightside enamel.

    star.jpg

    No noticeable color variations in the white paint.

    This one was Home Depot concrete floor enamel over fiberglass on wood (two coats rolled and tipped) with no primer used. I actually had to add the color variations (desirable in this case) myself with a spray gun.

    DSCF238a1.jpg

  23. #23
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    AndrewT, I presume this is a Devlin design, right? I wanted to put flat chines on the Surf Runner I'm presently building, which he highly recommended too, and he sent me a bunch of pictures of a Pelicano build that they put flat chines on and he said it greatly improved performance. Do you plan to do that?

    The reason I ask, is that the flat chines, and also the keel, go on after the first layer of fiberglass. The keel is filleted with a thickened epoxy fillet, 2 layers of biax, and 1 layer of woven, all done wet at same time (I'll use peel ply on top of that). Same on each side of keel. After the flat chines are shaped and the keel and everything is re-faired, then he recommends a layer of dynel on top of everything.

    Is your keel already on?
    Do you plan on flat chines?
    Are you planning on using Dynel? (by the way, I already bought the material and am committed, but honestly nervous about using it - I don't want to hijack this thread with the discussion, but had planned to get more advice on that in my Surfrunner thread soon.)

    I'm just getting to these steps on my build too, but have been slowed due to cold weather and epoxy not flowing out well. Am starting to think about primer too, so am following this thread closely.

    Good luck with your Pelicano!

  24. #24
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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    Russell Brown has series of videos on Off Center Harbor that seem to be a master class in applying glass and epoxy. It’s nice to see someone apply the techniques.

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    Default Re: Advice Needed: Finishing Stitch & Glue Hull

    garyb - Yep, it's a Devlin design. I hadn't heard anything about flat chines, but now I'm curious. I haven't added keel or chines yet, as they go on after fiberglass sheathing. I'd be interested to hear more about it.

    I googled "Dynel" when I started work, mostly because I already had a roll of 6- or 8-oz 'glass cloth leftover from another project and didn't want to have to buy a roll of different material if I didn't have to. From what I've read, I don't think I want to mess with Dynel, either.

    Frankly, this boat isn't a long-term goal; I'm having fun building it, but I'm ready to get it finished up so I can give it to my son, get it out of my workshop, and move on to the next project (a 14' Riva outboard runabout). I want it to last, but it doesn't need to last forever, and it doesn't need to be bulletproof, and it doesn't need to be indistinguishable from a factory-made boat. It needs to float right-side-up, and look decent, and perform okay. Lofty goals, I know .

    ESP71 - I've watched all of those videos, and you're right - it IS like a master class. Very informative and highly recommended.

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