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Fiberglassing question

Discussion in 'Strippers, Stitch-n-Glue, and Other Wood Composite' started by Rob Learmont, May 17, 2019.

  1. Rob Learmont

    Rob Learmont Curious about Wooden Canoes

    I am getting ready to start the fiberglass and epoxy on my cedar strip canoe.
    I have been reading every article and watching every video I can find since this will be my first attempt at fiberglass and epoxy.
    Since I got the plans from Northwest Canoe company, I chose to order the glass and epoxy from them. I will be using 6oz cloth and MAS epoxy with slow hardener.
    I plan on doing a seal coat first before wetting the fiberglass.
    Now for the question....
    After wetting the glass doing the fill coats I may need to scuff the surface depending on the timing. However I am thinking that the fiberglass has depressions (between the weave) that won't be touched by the scuffing.
    Has this issue been addressed or does the bond on the scuffed high spots make up for not scuffing the spaces between the weave of the cloth?
    I've put so much work in on my first build, I am trying to eliminate any possible problems.

    Thanks for any insights from your own personal experience.
  2. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Define exactly what you mean by "scuffing" and what purpose you intend for it to have. You are correct that you will not be able to get down into the depressions between the yarns of the cloth with any sort of abrasive. It is not OK to ignore those spots. By far, the best way to glass is to plan for a more or less continuous session, working around the clock and adding a layer as soon as the previous layer has hardened enough that you won't disturb it. Most of that time is spent waiting for epoxy to harden, especially with slow hardener. That way, there is never any need for any scuffing or sanding between coats and you avoid any problems with contaminants or amine blush. Getting the cloth installed and saturated and at least one good additional filler coat on the weave will pretty much take care of most of the weave texture, and it is worth getting to at least that point in one long session. Filling won't be complete yet, but the differences between the high and low spots in the weave texture will be greatly reduced.
  3. Mark Heinrich

    Mark Heinrich Curious about Wooden Canoes

    If you have a slower curing resin don't sweat it - and don't overwork it either.

    1. Wet out the boat with water and deal with any glue spots you might have missed and do one last sanding.
    2. Are you happy with all your smoothing and fairing? Remember not to focus on a spot - use a fairing board and orbital sand in a continuous sweeping motion. Once you put it under glass you can't do much leveling.
    3. The epoxy will actually cure/thicken more slowly spread out on the boat than in the cup
    4. Watch videos of people doing (Nick Schade and others)
    5. You're not going to fill the weave in the first coat. The first coat is to put an even bubble free bond of the cloth to the hull
    6. With a long time between coats you want to lightly sand before a fill coat - but don't chew into the cloth
    7. Finally my hard learned lesson. When all your epoxy is on clean the hull with a scotchbrite pad and cleanser - the epoxy releases a waxy film that sanding will spread around but not remove. That film is called amine blush and will prevent varnish from curing. I spent a horrible weekend with nasty solvents removing a beautiful looking expensive varnish that was still sticky after 5 days!
  4. Todd Bradshaw

    Todd Bradshaw Sailmaker

    It takes epoxy resin a week or better to cure enough that the risk of skin sensitization from sanding dust goes down to a reasonable level. Sanding resin which hasn't cured enough is a clear health hazard, and if you do develop the epoxy sensitivity/allergy problem, your days of working with epoxy are over immediately and for good. Any and all sanding on a stripper can, and should, be done 7-10 days or more after the resin has been applied and allowed to cure.

    There is no cleanser needed to remove amine blush. Plain water and a Scotchbrite pad works fine, and without introducing more chemicals to the project, which is more often a mistake than a help due to chemical contamination of the surface. Amine blush can do a lot more harm than just affecting the cure time of the varnish. It will also prevent layers of resin from sticking properly to previous layers. Blush is not that hard to understand or to deal with, but you do want to be aware of the concept and how to deal with it properly.
  5. OP
    Rob Learmont

    Rob Learmont Curious about Wooden Canoes

    Thanks for all of the tips!
    I am still sanding the bare wood right now and I am using a fairing board and RO sander.
    I hope to get to the glass and epoxy within the next couple of weekends.
    With the slow epoxy I'm planning on doing the seal coat late Friday evening, wet the glass early Saturday morning and get as many fill coats done Saturday afternoon/evening and all day Sunday.
    Hopefully I can time out the coats properly depending on the weather since I really don't have any way of controlling the temperature in my workspaces.
  6. Jim Dodd

    Jim Dodd LOVES Wooden Canoes

    Both Todd and Mark have given good advise ! I'd follow it !

    I often work into the wee hours of the morning putting that Final fill coat on.
    If you are planning a Seal Coat, let it cure just until it is no longer tacky ! Before laying the cloth on this, be sure to remove any regularities (dust particles) that might prevent your cloth from laying tight to the hull !! Use a gloved hand and go over the hull.

    Once the cloth is on, trim the edges to about 2" below the hull.
    Wet out the cloth.

    Are you adding an extra layer of cloth to the bottom ?
    If so, again wait until the epoxy has cured Just past tacky. Lay on the extra layer and glass.

    I'd wait about 4 - 6 hours and start fill coats. I keep adding fill coats about 2 hrs apart, until I'm sure the weave has been Fully filled. Then I go to sleep !

    I use RAKA's Non Blushing Hardener and their 127 Resin. Never a problem with blush.
    Is the MAS a non blushing epoxy ?

    Good Luck !
  7. OP
    Rob Learmont

    Rob Learmont Curious about Wooden Canoes

    Thanks Jim,
    Yes, the MAS epoxy and slow hardener is supposed to be "Non-blushing".
    Right now I am only planning on one layer of 6oz cloth for the exterior and interior, I plan on adding some bias strips on the stems and the first foot of the bottom (where I see most of the scratches on other canoes)
    A lot will depend on the weather when I finally get around to doing the fiberglass and epoxy, I'm hoping for a warm (80 degrees) weekend so I can do the seal coat Friday evening (as the temps drop to help with outgassing) then first this Saturday morning wet the glass and do the fill coats all in one day.
    Today I mixed my epoxy with wood flour to fill in the tiny gaps between a few of the strips. I have the hull pretty much faired already, so next week I'll hopefully finish the sanding.

    I found a mistake today as well that I had to remedy......I read and watched videos about how to attach the outer stems and I understood that I needed to counter sink some screws to hold it in place while the glue dried and put plugs in the holes. Luckily today I figured out the my screws were actually screwed all the way into the stem forms!!! So I drilled out the plugs and removed the screws and replaced new plugs in the holes. I am sure glad I figured that out now, imagine what it would have been like after the fiberglass and epoxy was done and I was trying to get the stem forms out, with screws in them????? Maybe I misunderstood the instructions for the outer stem screws and I should have used shorter screws that would only secure it to the inner stem.

    I'm not rushing through any part of this build, I'm setting a goal of getting done by the spring of NEXT year.
    I know sanding the interior is going to take a long time, I milled my own strips and they are not exactly uniform thickness. so it should be "fun" to fair the inside. Plus I used maple and walnut for accents, so they sand at a different rate than the soft cedar, so I will have to be extra careful.

    I am doing a lot of custom work, including bulkheads for floatation and dry storage, I am going to hand cane the seats once I get the frames built, make scuppered inwhales, and I still haven't decided on what woods and designs I'm going to make for the decks.
    Plus I'm going to make my own paddles.

    I am really enjoying every part of the building process (including the sanding, I have been looking forward to it for many, many years and I want to get everything out of it that I can.

    "Anything worth building is worth over-building"

    Attached Files:

    Last edited: May 18, 2019
  8. Jim Dodd

    Jim Dodd LOVES Wooden Canoes


    It sounds like a good plan !

    Funny when I used to seal coat, Friday night is when I started.

    Yes the inside is a bugger, ROS makes it a lot easier ! I started with a 1/4 sheet palm sander. I add carpet foam between the sander and the paper, for those inside curves ! The Memory still Haunts me ! Ha !

    Enjoy !

    Just noticed the SOS in your decorative strip ! Hope you won't need it !

  9. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Be aware that if you are using a saturation coat of epoxy and letting it harden before you apply the cloth, that it will usually raise the grain a bit. It doesn't hurt anything, but those tiny little stickers on the surface can make it difficult to slide or move the cloth around (especially while it is dry) as you begin the fiberglassing process. You sort of want to lift the fabric a bit in order to move it, rather than just pulling on it and expecting it to slide. Not a big deal, but worth being aware of before you start.
  10. OP
    Rob Learmont

    Rob Learmont Curious about Wooden Canoes

    Just noticed the SOS in your decorative strip ! Hope you won't need it !


    Thanks Jim. The accent strip is my attempt at humor, it took almost a full month to cut and glue up.
    The salted maple and walnut really stand out when finished.
  11. Mark Heinrich

    Mark Heinrich Curious about Wooden Canoes

    To fair the inside look up Nick Schade's videos. He gives a lot of good advice on scrapers that would have saved me a lot of sweat and tears (maybe even a little blood too).
    Jim Dodd likes this.

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