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Thread: fiberglassing hull

  1. #1
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    Default fiberglassing hull

    A boat is fifteen by six ft. How much weight and expense to glass the exterior of the hull with 4 Oz cloth?

  2. #2
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    Default Re: fiberglassing hull

    A couple of hundred bucks for material and maybe 40 lbs. or so. What is the boat and what sort of construction? That's going to make a big difference also. If the hull needs a lot of prep, that'll add to the cost.
    I was born on a wooden boat that I built myself.

  3. #3
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    Default Re: fiberglassing hull

    4 oz cloth isn't going to give you much strength, but you may be glassing to make the hull waterproof, not to strengthen it. 4 oz cloth weighs 4 oz per sq. yard. Your boat is going to take no more than 10 sq. yards to glass it. In a good layup the glass:resin ratio is about 50%, so you are looking at 8 oz per sq. yard so 5 lbs for glass and resin. You will likely almost triple that weight by the time you fill the weave and fair the surface out unless you vacuum bag the layup and use peel ply. So the glass ought to weigh about 15 lbs tops. As far as cost goes, my local chandler will sell you 10 yards of 38" width 6 oz cloth for $48. You will need about a gallon of resin so figure an additional $40 for polyeste and $120 for epoxy. The cost ought to come in under $100 for ployester resin and under $200 for epoxy. If you vacuum bag the bagging supplies will about double the cost, but you will save on resin.

  4. #4
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    Default Re: fiberglassing hull

    The boat is a stitch and glue multi chine dinghy. It already will weigh in around 130 lbs and I want to keep it around 160 at the most. My reason for glassing would be to protect the hull -- durability. Will simply painting epoxy on the hull do that anyway?

  5. #5
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    Default Re: fiberglassing hull

    Sure, epoxy is enough but why not lay some glass in it while you are at it?

  6. #6
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    Default Re: fiberglassing hull

    If I were going to glass it, I'd use 6 oz, not 4. The 6 will provide some durability; 4 is real light and will wear through pretty easily.( good for watertightness or to make a smoother finish though).

    My Two Cents

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  7. #7
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    Default Re: fiberglassing hull

    You're right, 6 oz doesn't add a whole lot of weight overall, but it sounds like it provides a lot more strength. If you glass over the exterior with 6 oz, do you have to worry about the 2-inch wide 6 oz tape at the exterior seams bulging?

  8. #8
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    Default Re: fiberglassing hull

    How about some glass on the bilgestrakes for abrasion resistance if you're going to be dragging it around, and leave it at that if you're really concerned about it? Do you really want to spend the money and wrastle your boat around with extra poundage?

    Below, neither boat has glassed bottoms. The one on the left has glassed chines with 2" tape since they are hard chines, and the ply is epoxy coated, and the lapstrake one on the right has no glass nor epoxy coating. The one on the left has been beaten up, beaten down, beaten onto rocky shores, and so far, so good. The one on the right will probably get a UHC shoe for the keelson, other than that, lap ply with some tension on them are quite strong.



    Edit: This sandy beach is not common around heres

    Edited to add again: Not only will it be $$$ and extra weight you will also be dealing with more epoxy exposure, dust from fairing and sanding after epoxy has cured, etc etc. Just increased hazards. Your mileage on your opinion to this last point may vary depending on your personal outlook.
    Last edited by callsign222; 10-22-2012 at 10:40 AM.

  9. #9
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    Default Re: fiberglassing hull

    Quote Originally Posted by capefox View Post
    You're right, 6 oz doesn't add a whole lot of weight overall, but it sounds like it provides a lot more strength. If you glass over the exterior with 6 oz, do you have to worry about the 2-inch wide 6 oz tape at the exterior seams bulging?
    Fair the tape before glassing the hull... you would need to fair it anyway, even without glassing the rest of the hull.

  10. #10
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    Default Re: fiberglassing hull

    This may be fodder for another thread, but will an epoxy-soaked finish topsides deteriorate and then crack up due to UV damage?

  11. #11
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    Default Re: fiberglassing hull

    If a good 1 part (or better-2 part) varnish is used over the epoxy and IF that varnish is maintained on a yearly or every 2 years maintenance schedule then it should last for the life of the boat. The good marine varnishes contain UV inhibitors which help to maintain the integrity of the varnish and as an added bonus, helps the epoxy coating underneath the varnish. I assume we are talking a "bright" finish, ie, exposed wood grain that takes the beauty of the wood boat and elevates it to another level where passers-by stop to gawk at your craftsmanship!

    West System has an epoxy used expressly for the purpose of bright finished wood. Even at that, this epoxy must be maintained with a good UV inhibiting varnish.

    Either way, brightwork means more owner maintenance. But it sure looks pretty when done right. Other then that, epoxy should never be allowed to stand alone on a boat exposed to the sun.......it must be covered with a good marine primer and paint or a good varnish with uv inhibitors. Sorry for the long winded response!

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    Last edited by M. J. Notigan; 10-22-2012 at 06:39 PM.

  12. #12
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    Default Re: fiberglassing hull

    I tried that on a wooden Tornado catamaran. Didn't work well, I was fixing the surface almost every outing and I tried to protect the boat when bringing it in to the trailer. Plain epoxy has very little abrasion resistance, glass is tough.
    It would be a waste of your money to just Epoxy cause you will be doing it again. Use 6oz as said before. Sand the edges of the 6oz tape at the chines before you laminate the entire surface to avoid seeing the ridges. Probably if you laminate over a ridge you will sand thru the outer layer trying to make it smooth, costing you some of the strength you paid for in time and material.

    Keep the weight of the coating down by learning to use a squeege, especially on the inside. When laying down the glass with the epoxy you should clearly be able to see the weave sticking up but no whitish areas meaning a lack of epoxy. You can add 10's of #s in epoxy if you don't squeege and remove the excess.

    If you want to save yourself a lots of time and anger, don't make your first boat brite. Paint it. A perfectly good glass lamination may not be very pretty the first time you do it.

    Quote Originally Posted by capefox View Post
    The boat is a stitch and glue multi chine dinghy. It already will weigh in around 130 lbs and I want to keep it around 160 at the most. My reason for glassing would be to protect the hull -- durability. Will simply painting epoxy on the hull do that anyway?

  13. #13
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    Default Re: fiberglassing hull

    I agree with "upchurch" in #12- the resin is one part of the composite structure, the fiber is the other. Using one without the other gets you much less than half of what you get with the composite.

  14. #14
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    Default Re: fiberglassing hull

    One thing you should keep in mind is that increasing the glass from 4oz to 6oz will add more than the weight of the cloth. 6oz is thicker, and will use more resin to saturate it.

  15. #15
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    Default Re: fiberglassing hull

    A fifteen foot long "multi-chine dinghy" with a six foot beam? Oh...kay... This will be the dinghy for your 70' schooner? (Naw, can't be.) I gather you aren't planning on rowing or sailing it. So we're talking about an outboard on a planing hull. Got it.

    I don't know where this recent fetish for slathering googe all over the bottom of small boats for "abrasion resistance" got started, but it's making the epoxy and glass fabric manufacturers rich men and sucking that money out of the pockets of honest boaters. I guess if epoxy and glass is all that holds the boat together, you're "in for a penny, in for a pouind," but if your concern is tearing up the bottom, 1) don't run the boat onto the rocks and 2) install proper rubbing strakes, sacrificial if need be, to address pulling the boat up on the beach, and be done with it. The way things seem to be going these days, one wonders how anybody ever managed to get anywhere in a boat in the days before epoxy and fibreglass were invented.
    Last edited by Bob Cleek; 12-01-2012 at 07:15 PM.

  16. #16
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    Default Re: fiberglassing hull

    Bob,

    There are a lot of wooden boats built before goo.
    The vast majority of them have rotted away. Most of those left are on their way. A very few are kept up by the knowledgeable, dedicated guys with a love for the type.

    And you know it very well.

    I agree it doesn't have to be that way. Very few will spend the time or take the care to keep them alive. Most of those boats alive are just like "my grandpa's hatchet" original except for replacing 3 handles and 2 heads.

    We see fascinating threads here regularly about the 2 year long replacement of 50% of the boat.

  17. #17
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    Default Re: fiberglassing hull

    [QUOTE=Bob Cleek;3613057]A fifteen foot long "multi-chine dinghy" with a six foot beam? Oh...kay... This will be the dinghy for your 70' schooner? (Naw, can't be.) I gather you aren't planning on rowing or sailing it. So we're talking about an outboard on a planing hull. Got it.

    Bob, it is the Argi comfortable
    e 15, which is best described as a multi purpose dinghy -sails very well, rows decently, and takes up to a 5 HP outboard

  18. #18
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    Default Re: fiberglassing hull

    on all my dinghies, i have timber rubbing strakes to take the ground at landings. otherwise they are just painted. i do take care with them however. nothing is too difficult to look after if you take your time when out in the dinghy. and some people who do not own timber boats or dinghies just need a little instruction and guidance when and if they are near or in your boat!

    if you are going to leave her long term in the water, just antifoul the bottom.

  19. #19
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    Default Re: fiberglassing hull

    Personally I would just paint it and if it gets scuffed, paint it some more.

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