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Thread: Polyester resin for plywood boat build

  1. #1
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    Default Polyester resin for plywood boat build

    Hi again,

    Iv been advised that it is possible to do the structural work and adhesion with epoxy and glass fabric, but then to cover the largest areas and seal the boat with polyester resin and glass fabric.
    Just wanted ask if anyone had experience with this or advice either way.

    Thanks

  2. #2
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    Default Re: Polyester resin for plywood boat build

    That is bad advice. Don't do it.

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    Default Re: Polyester resin for plywood boat build

    For more information - use the 'search' function here. It as been amply discussed.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Polyester resin for plywood boat build

    Quote Originally Posted by wizbang 13 View Post
    That is bad advice. Don't do it.
    Agreed.

    Polyester doesn't stick to wood or epoxy nearly as well as epoxy.

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    Default Re: Polyester resin for plywood boat build

    Again, mixed reports.

    Some people on other previous threads have said polyester resin works fine. I think its just a matter of budget versus durability, and a matter of balancing it.

    The epoxy and glass for my design is coming in around €130, and the polyester resin around €50. The 6mm Marine ply is €50/sheet. And the 6mm WBP ply around €14/sheet. so I think if I spend less on polyester resin, AND use WBP ply it will fall apart very quickly.

    So I will buy the highest grade epoxy and glass, and use the cheaper ply.

    Welcome feedback..

    thanks

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    Default Re: Polyester resin for plywood boat build

    Don't be in such a rush Dylan. Earn then spend the money on good products.

    Maybe if you look at it this way it will help. It takes longer to build if you have to spend more time earning in order to afford the proper materials, and you don't want to waste time, right? Building with inferior materials is a waste of time.

    Or, to phrase it differently, if it's worth doing it's worth doing right.

    I've seen a lot of polyester peeling off of plywood, and a lot of cheap plywood delaminating. Even it the glue is good it won't work if it's applied hit and miss.

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    Default Re: Polyester resin for plywood boat build

    "So I will buy the highest grade epoxy and glass, and use the cheaper ply."

    nope, didn't say that

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    Default Re: Polyester resin for plywood boat build

    Polyester is a mistake you don't want to make. It would probably take you a couple of boats just to learn how to use it well, a couple more to figure out a technique to prime the wood for a decent bond, and a few more to really find a particular resin brand and formula which will not delaminate easily. That's the sort of thing we went through back in the early 1970s before boat building epoxy resins came on the market. These days, polyester on wood is simply a dumb choice and a waste of time and money that you will probably regret later. Why trash your boat before you even build it?

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    Default Re: Polyester resin for plywood boat build

    Polyester is definitely out of the window, but the plywood issue is the real killer.
    The thing is I want to get my design built, and usable as soon as I can. Its a fairly simple design, but I expect it will take a bit of time anyway.

    I have had reassurance from some people with experience that if the epoxy is done properly, and carefully, with 2-3 layers of glass, then a plywood boat that is not being left in the water for too long can last years.

    Today I have received quotes for UV resistant epoxy and have factored in extra for fixing and sealing all the joints.

    I know it would be better to use marine ply, but I could buy a boat for the cost of it.

    I will post pictures of the build once it gets underway

    Thanks for all the input

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    Default Re: Polyester resin for plywood boat build

    well, its definely not WBF approved, but it has been done many times over, and it can produce a decent, if not long lasting boat, but it will take experimentation with some pretty nasty chemicals like MEK spirits, catalyst and acetone . it's more of a learning curve and labor intensive and you have a much higher chance of screwing things up if you aren't familiar with the processes.

    you should probably just use epoxy and save yourself the ball-ache. sure epoxy is roughly double the cost, but there is. reason why it is so popular, . as I mentioned in your other thread - look at RAKA epoxy for a more affordable option

    if you're just building a cheap/simple plywood boat I'd use a polyurethane adhesive (like PL premium) to glue up the structure and then use epoxy & glass on the hull exterior (and maybe a barrier coat on the interior)

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    Default Re: Polyester resin for plywood boat build

    Today I have received quotes for UV resistant epoxy
    Your UV resistant epoxy is not resistant enough to build a boat with and leave unprotected. The real UV resistance of anybody's epoxy resin is drastically more a matter of what you cover it with than what is in the resin itself. A couple decent coats of enamel over your epoxy will be easily ten times more UV protection than anything somebody is going to add to their resin, which then becomes little more in real life than advertising hype for the uninformed. You would do well to download a free copy of "The Gougeon Brothers on Boat Construction" and start studying.

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    Default Re: Polyester resin for plywood boat build

    How about, use good ply and do not glass it?

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    Default Re: Polyester resin for plywood boat build

    Well that is a controversial suggestion.

    Even marine ply will de-laminate if its left standing in water. it would still need to be coated in epoxy, and the seams still need to be reinforced with glass fiber tape and epoxy.
    Marine ply can be around €75 per sheet, The WBP plywood which is rated for external use in extremes of temperature and moisture is only €14 euros per sheet.
    and glass cloth is about 65 euros to cover the whole boat. and the epoxy is about €65.


    Quote Originally Posted by wizbang 13 View Post
    How about, use good ply and do not glass it?

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    Quote Originally Posted by DylanL View Post
    Again, mixed reports.

    Some people on other previous threads have said polyester resin works fine. I think its just a matter of budget versus durability, and a matter of balancing it.

    The epoxy and glass for my design is coming in around €130, and the polyester resin around €50. The 6mm Marine ply is €50/sheet. And the 6mm WBP ply around €14/sheet. so I think if I spend less on polyester resin, AND use WBP ply it will fall apart very quickly.

    So I will buy the highest grade epoxy and glass, and use the cheaper ply.

    Welcome feedback..

    thanks


    My skiff is made with good ply. Its only glasses on the bottom. A good paint job and she's rot free.

    I'd pick better ply and no resin / glass before cheap ply and lots of resin.

    Kevin


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    Default Re: Polyester resin for plywood boat build

    Did you pay €75 or $90 U.S dollars per sheet for your ply?

    Quote Originally Posted by Breakaway View Post
    My skiff is made with good ply. Its only glasses on the bottom. A good paint job and she's rot free.

    I'd pick better ply and no resin / glass before cheap ply and lots of resin.

    Kevin


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    Default Re: Polyester resin for plywood boat build

    I think the thing people are not taking into account is that I live in Ireland.

    Everything is very expensive and it rains 300-340 days a year. marine ply will still need to be epoxy coated, and glassed. So the investment of several hundred euros in plywood is pointless.

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    Default Re: Polyester resin for plywood boat build

    We are talking about a small rowboat here right?
    Will it be left in the water , in the sun and rain, or kept mostly under a roof or upside down?
    Maybe the boat needs to be planked with timber, or strip planked?

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    Default Re: Polyester resin for plywood boat build

    If you just want a boat, you are dead right, it's cheaper to buy one. And you might as well get a fibreglass one. If you want to build a boat, you'll get no satisfaction in doing a half @@ssed job of it. You are going to spend a lot of hours on it. Bight the bullet and treat yourself to decent materials. About a gazzillion ply boats have been built with decent ply, epoxy joins, and either epoxy/glass taped seams, or no glass at all and just painted. Mostly they last OK. Lots of boats are glassed inside and out. One layer of glass is usually enough. They last well too, so long as water doesn't get in under the glass anywhere. Don't waste your money on UV epoxy. Put something on over the epoxy, either a clear fi ish with UV filters, or some sort of paint. Try to be a bit more open minded. To be honest, you seem to have picked up some pretty bad ideas and seem to want to hold onto them. Advice from people like Todd is very, very good advice.

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    Quote Originally Posted by DylanL View Post
    Did you pay €75 or $90 U.S dollars per sheet for your ply?


    More. $110 per sheet. Six years ago.

    Now, price out the quantity of resin and glass to make cheap ply " boat worthy."
    If you do, I believe you will find using resin-slathered cheap ply false economy.



    Kevin


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    Quote Originally Posted by DylanL View Post
    I think the thing people are not taking into account is that I live in Ireland.

    Everything is very expensive and it rains 300-340 days a year. marine ply will still need to be epoxy coated, and glassed. So the investment of several hundred euros in plywood is pointless.



    A good paint job on good ply is all you need for rot resistance. And you are going to paint it anyway, yes?

    Kevin


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    Default Re: Polyester resin for plywood boat build

    Ok well this has become too heated.

    I'm here asking for advise.

    Thanks to all contributors.

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    Default Re: Polyester resin for plywood boat build

    Quote Originally Posted by DylanL View Post
    I think the thing people are not taking into account is that I live in Ireland.
    Aye, and there's not a hope for ya then at all, at all.

    Quote Originally Posted by DylanL View Post
    Ok well this has become too heated.

    I'm here asking for advise.

    Thanks to all contributors.
    Too heated? Man... you ain't seen the half of it.

    You're getting good advice.
    David G
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    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Polyester resin for plywood boat build

    Hi Phil

    I appreciate the advise about the uv epoxy, Because this is my first build. Basically the design is completely my own, as in the shape and how it is joined is a combination of boat shapes i have used here on the lake, and construction methods I have learned about, from books, from advise on this forum and from experienced boat builders.

    As it is untested I am going to use 6mm WBP ply. If i mess up I can buy another sheet.
    Its basically a prototype.
    WBP ply, glass cloth, epoxy and tools is coming in under 200 euros.
    Its not about holding onto bad ideas, its about doing the best within your means.

    The next build will be an improvement and will be worth investing more in.

    The other factor is I want to get out on the lake and get some pike as soon as I can.

    My gratitude for all advice received.

    Quote Originally Posted by Phil Y View Post
    If you just want a boat, you are dead right, it's cheaper to buy one. And you might as well get a fibreglass one. If you want to build a boat, you'll get no satisfaction in doing a half @@ssed job of it. You are going to spend a lot of hours on it. Bight the bullet and treat yourself to decent materials. About a gazzillion ply boats have been built with decent ply, epoxy joins, and either epoxy/glass taped seams, or no glass at all and just painted. Mostly they last OK. Lots of boats are glassed inside and out. One layer of glass is usually enough. They last well too, so long as water doesn't get in under the glass anywhere. Don't waste your money on UV epoxy. Put something on over the epoxy, either a clear fi ish with UV filters, or some sort of paint. Try to be a bit more open minded. To be honest, you seem to have picked up some pretty bad ideas and seem to want to hold onto them. Advice from people like Todd is very, very good advice.

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    Default Re: Polyester resin for plywood boat build

    I''m sorry .. was that, "at all, at all" like an Irish accent, at all at all,, you want to see heated I'll report your ass for racist comments,
    I'm asking for advice and I'm grateful for it.

    Advice is great, if you can take it. otherwise you do your best. you get me.

    I think The anonymity inherent in forums like this can all too easily allow the very worst aspects of human nature to be amplified without fear of repercussion that exists in a physical confrontation.

    This just got boring.

    Thanks for the advice, no thanks for the attitude.


    Quote Originally Posted by David G View Post
    Aye, and there's not a hope for ya then at all, at all.



    Too heated? Man... you ain't seen the half of it.

    You're getting good advice.

  25. #25
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    Default Re: Polyester resin for plywood boat build

    I'll report your ass for racist comments,

    HAHAHAHAHAHAHAHAHA

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    Default Re: Polyester resin for plywood boat build

    You might consider sealing the boat with epoxy resin before paining it, rather than coats and coats of glass. Fiberglass is not pleasant to work with, adds weight, and really, its the resin and the paint you put over it that keep the ply from delaminating. Just work full-strength resin into the wood by spreading it with a plastic spatula, no need for a thick coat, most of the seal is the paint.

    And if you don't like heated exchanges, never, ever, bring up clear penetrating epoxy sealer. It's like discussing religion!

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    Default Re: Polyester resin for plywood boat build

    Quote Originally Posted by DylanL View Post
    I''m sorry .. was that, "at all, at all" like an Irish accent, at all at all,, you want to see heated I'll report your ass for racist comments,
    I'm asking for advice and I'm grateful for it.

    Advice is great, if you can take it. otherwise you do your best. you get me.

    I think The anonymity inherent in forums like this can all too easily allow the very worst aspects of human nature to be amplified without fear of repercussion that exists in a physical confrontation.

    This just got boring.

    Thanks for the advice, no thanks for the attitude.
    My apologies for fomenting a misunderstanding. I was not poking fun at your Irish heritage. I was simply trying to get a point across in language you'd grok. At the same time, let me suggest that your 'taking offense' button seems to be a bit hair-triggered. If you spend more time on internet forums... I suspect you'll learn that the medium leads to potential misunderstandings, and that it's best to confirm such impressions before taking umbrage.

    You're getting good advise. Take it.

    If you didn't actually want it, and simply wanted your pre-conceived notions (however apt... or not... they might be) validated? You came to the wrong place.
    Last edited by David G; 07-04-2018 at 11:28 AM.
    David G
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    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

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    Default Re: Polyester resin for plywood boat build

    Seriously dude, retract your elbows. You came here seeking advice and then get your undies in a knot when the advice doesn't confirm your biases? This forum is an incredible resource which allows anyone with an internet connection to tap the deep knowledge of some genuine boatbuilding savants. What you make of it is up to you but 'twer it me, I'd be quiet and listen. Humility goes a long way when trying to learn something. I've been schooled a couple times here and not ashamed to admit I'm the better for it.
    Last edited by Dusty Yevsky; 07-03-2018 at 11:01 PM.

  29. #29
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    Default Re: Polyester resin for plywood boat build

    What are you building?
    If if it is a mad idea you want to test go cheap
    If it is a boat you want to last, have great memories pas on to the family get the good stuff

    I sincerely believe that many dinghy designs could be tweaked slightly to reduce the materials required - see the work of flo-mo (http://flo-mo.weebly.com/)

    He has some nice 11 - 12 ft dinghies from two sheets of ply

    Why do you want to cover it in glass a anyway. We have plenty of plywood dinghies built forty years ago that still hold up - good wood of the correct thickness is a better solution. One thickness thicker than what you propose to use know would probably save cash and certainly time

    If you’re wanting protection so you gain drag it up the beach just glass the bottom, uses stout runners, use graphite powder.

    If what you built takes 100 hours and only lasts 3 years it is false economy

    Build a slightly smaller boat, change your expections - the smaller the boat the more use it gets.

    I am sure better advice can be given with more details of the project

  30. #30
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    Default Re: Polyester resin for plywood boat build

    Now this is why I joined the forum, Thank you for the link to the work of flo-mo, fantastic stuff.

    I'm an architect so I absolutely love everything on that web page, the hundertwasser models are amazing.

    But back to boat building.

    I have designed a boat, by building models, sketching and experimenting, that is going to be used on inland freshwater lakes here in Ireland.
    It is quit similar to the west mersea duck punt on the link you sent. But set up for a motor.

    The idea is that I use 6mm ply for the hull, stitch and glue the seams and reinforce with glass tape and epoxy resin. reinforce the hull with lateral ribs made of Douglas fir with plywood webs. 2 sets of these will form the seats. and one will become structural reinforcement for the rowlocks.
    Then to coat the outer surface with epoxy resin and glass fiber woven roving, and paint. ( might just ask a professional for advice on that) Cover the whole inside also with epoxy, and again seal all joints and edges with glass tape and epoxy resin.
    It will be left in the water with a cover on for a few months each year, Hopefully, depending on the weight, as the ramp I will be using would require a trailer and a 4x4 to launch and take the boat out of the water every time.

    I have priced all materials now at under 200 euros, with 3 sheets WBP ply at €14/sheet, and I got a quote this morning for 6mm Marine ply at€38/sheet, so all in all I will probably get marine ply anyway. which might bring it up to €300 ish.

    My questions on this forum were for advice on the epoxy resin. (big mistake)

    I have had advice from a boat builder here and have chosen a supplier.

    I might start a new thread to discuss the build and upload images as a bit of hostility has cropped up on this one.


    Again thanks for the information.


    Quote Originally Posted by tink View Post
    What are you building?
    If if it is a mad idea you want to test go cheap
    If it is a boat you want to last, have great memories pas on to the family get the good stuff

    I sincerely believe that many dinghy designs could be tweaked slightly to reduce the materials required - see the work of flo-mo (http://flo-mo.weebly.com/)

    He has some nice 11 - 12 ft dinghies from two sheets of ply

    Why do you want to cover it in glass a anyway. We have plenty of plywood dinghies built forty years ago that still hold up - good wood of the correct thickness is a better solution. One thickness thicker than what you propose to use know would probably save cash and certainly time

    If you’re wanting protection so you gain drag it up the beach just glass the bottom, uses stout runners, use graphite powder.

    If what you built takes 100 hours and only lasts 3 years it is false economy

    Build a slightly smaller boat, change your expections - the smaller the boat the more use it gets.

    I am sure better advice can be given with more details of the project

  31. #31
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    Default Re: Polyester resin for plywood boat build

    Is it the same size as a duck punt?

    if so a would just go heavy, lots of timber, chine logs and Titebond III glue and paint - no resin anywhere.

    See the pictures here https://www.facebook.com/pg/Mersea-D...=page_internal

    This uses 10mm? Ply so probably 9mm

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    Default Re: Polyester resin for plywood boat build

    I hope the build goes well. As a self designed experiment, it may have some glitches, but thats OK, learn and move on. You probably do need to chill a bit, folks here do tend to have a slightly wry sense of humour. But as long as you stay out of the Bilge political threads its mostly pretty civil and friendly. Hang around for a bit, you have stumbled on a great resource.

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    Default Re: Polyester resin for plywood boat build

    Thanks. I'll post progress as it happens.
    Yeah, each to their own with the wry sense of humour I suppose, even trump supporters have rights...

    Yeah its invaluable, the hive mind of boat building knowledge.
    Internet forums are a strange phenomenon of our age, and I generally loath them, for reasons I won't get into.

    Its all about the boat build.

    Quote Originally Posted by Phil Y View Post
    I hope the build goes well. As a self designed experiment, it may have some glitches, but thats OK, learn and move on. You probably do need to chill a bit, folks here do tend to have a slightly wry sense of humour. But as long as you stay out of the Bilge political threads its mostly pretty civil and friendly. Hang around for a bit, you have stumbled on a great resource.

  34. #34
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    Default Re: Polyester resin for plywood boat build

    Not wanting to stir anything up, I built a ply dinghy in 1988 and taped the seams using polyester resin. The boat has been outdoors ever since, and is still in service. Some of the fg tape came loose on the transom, I cut and pulled it off pretty easily. The tape was not structural, but abrasion resistance. That boat was built on oak stringers using other methods now frowned upon: resorcinol glue and galvanized screws through douglas fir plywood. If that tape had been applied with epoxy it would have stuck tightly to the transom. Everywhere else it still adheres, I don't know why it stuck in some places and not others. The fir ply has checks on the inside where it was only painted, on the outside I rolled polyester resin and it is intact. I think you should use the best materials that you can reasonably afford, but not refrain from building if you can't afford the best.
    Good luck, keep us posted.

  35. #35
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    Default Re: Polyester resin for plywood boat build

    Looking forward to seeing pics Dylan I understand about the humidity problem on Erin (although last time we went over there we came back sunburned!?!) as we live in the Northwest of the US...very similar climate. You mentioned a motor? What power range and how heavy? That will considerably affect your strength requirements. You also mentioned a steep ramp requiring a 4X4 for launching, but you might consider that if the boat's light enough, you could easily carry it to the trailer (OK...with a couple of chums...beer's cheaper than a 4X4). Food for thought

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