Building a stitch & glue boat in Fiji

Discussion in 'Boatbuilding' started by Saqa, Oct 20, 2013.

  1. Saqa
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    Saqa Senior Member

    Does that mean that epoxy bonds better to untreated wood then acrylic impregnated wood? Its hard to reconcile in mind that epoxy is so highly regarded in the boat building world while in other trades its looked upon as a reasonable compromise with ease of use but not long lasting results. To date I have looked at it as a cosmetic product for good initial first impression but something that cracks, peels, lifts, softens...around moisture, humidity and heat especially tropical
     
  2. michael pierzga
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    michael pierzga Senior Member

    As far as I know any contaminant retards the epoxies mechanical properties.

    Dont make things complicated. Follow the advice in the West systems book and you will produce a superior boat.

    There very well may be additional tricks of the trade not outlined in the book.

    Waite until you have built a few more boats and mastered common methods before you test vacuum bagging, resin infusion , post curing....or other techniques that produce superior results.
     
  3. groper
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    groper Senior Member

    And what other trades are you talking about?

    Epoxy resin, is the only thermosetting resin which is considered near enough 100% waterproof. When used correctly and with due care and skill, the timber it protects will stay in perfect condition for longer than the person who built it remains alive on this planet.

    It is superior in this respect, to any other resin used in the composites industry such as polyester and vinylester etc.

    It is uneffected by moisture, is impervious to moisture - unlike the other resins, and has 3x lap shear adhesion mechanical properties, higher elongation to break mechanical properties, and better tensile and compressive strengths to most other resin system youd care to name.

    So this isnt about what a boat building fraternity likes more, its about science and engineering which applies equally to any industry as the physics dont change regardless. Youd undertand all this better if you did some more reading rather than asking 101 elementary questions on here, which illustrates your lack of understanding - and i mean that in a respectful/helpful way. There are many threads which answer your questions and the gougeon bros/west system guide to timber boat building has almost everything you need to know contained within it -as others have already mentioned - and its free.

    IN case you havnt found it yet, here -> http://www.google.com.au/url?sa=t&r...twp8RgXdJDAtieA&bvm=bv.55819444,d.dGI&cad=rja
     
  4. PAR
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    PAR Yacht Designer/Builder

    Don't use a sanding sealer on the wood. What this stuff does is seal the cut cellular tubules of wood fibers. This is great if you want an even finish for your aunt Millie's coffie table, but not at all what you want when building a boat.

    What you want is to seal these wood fiber with epoxy, not the acrylic sealer. The first coat of epoxy will seal the wood. The second coat insures that any dry areas (there's always dry areas) have nearly sufficient film thickness to insure waterproofness. The last coat insures film thickness, which can be applied alone or with a fabric.

    Again, read the User's Guide and Epoxy Book downloads I've previously mentioned, these concerns are covered there and they're a handy reference when you have a question or two.
     
  5. Saqa
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    Saqa Senior Member

    Groper you shouldnt assume my level of knowledge or experience. I am the first to admit that I this is my first proper boat build but I have used epoxy in its many forms in auto body, fishing tackle, electronics, joinery and carpentering for very many years and a couple of those as a profession! There is certainly lack of understanding which I am trying to correct by understanding the "whys" and looking beyond the "just do these steps"

    I can read all the product brochures published and become another one keyboard warrior quoting quotes. I feel instead that I am presenting intelligent questions to an experienced audience who can relate and reply based on experience!

    I have seen epoxy scuff, chip, lift, peel, go soft, rot the substrate by trapping moisture and more. I have seen countless fishing rod guides rust when epoxy doesn't match the flex in the blank and cracks allowing salt water in. I have seen epoxy lifting and peeling on guide wraps and label sections. I have seen epoxy going soft with heat and failing. I have seen salt crystals sitting on epoxy in the sun damage the surface. I have seen what happens when a car or covered boat is left in the Australian sun day in day out. What happens to things inside that contain epoxy somewhere. I have seen heavy weight fibreglass rods break when bent a bit to fit in a car and parked in the sun for a day. I have a Silstar Powertip with a clear tip section here that did just that parked in the Fijian sun. The wraps on this rod are renowned as absolute PIA to remove for repairs to rusted and broken guides. Guess what this is epoxy and not onlyh the rod is broken but the epoxy encapsulation on the wraps can be easily damaged. One tech I use to take apart old epoxy joints in various other things not including boat building is a steamer or a heat gun or a pot of hot water

    How does silicon affect epoxy? What about oils? Do you know what the ply or glass fabric has seen before its made it to your hands? I have seen epoxy that appears to have attached and cured to timber and other substrates but months later has lifted and trapped water

    Do you really dispute any of those shortfalls in real life use and assign irrelevance to any related implications for boat building? Or are you saying that wading through 100s of pages of printed media hoping to run across an excerpt on an issue in ones mind is an option but asking questions on a forum with field experience is not?!!!
     
  6. Saqa
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    Saqa Senior Member

    Thanks Par for an attempt at outlining some of the whys. Will I find what makes the acrylic not as good as the epoxy as a sealer in any of those documents though? It is a familiar item from on of my interests and something I always have on hand in good quantities, I think its ok for me to wonder about its use here and ask others that might know about it
     
  7. michael pierzga
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    michael pierzga Senior Member

    Actually rusting metal buried in epoxy has nothing to do with the epoxy. When you deprive stainless steel of oxygen it rusts.

    Epoxy also has very poor endurance when exposed to sunlight..uv.

    And yes indeed...epoxy goes soft when you heat it. Its a good way to clean off cured epoxy from tools

    dont bake you boat !!

    Even painting your boat black can effect the epoxy
     
  8. Saqa
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    Saqa Senior Member

    Maybe but when you cut up a wrap with cracked epoxy its usually wet inside and the guide foot rusted to buggery. I use an alternative to epoxy on rods that I do not want to suffer any of epoxies short comings. Dont know if you familiar with U40 Permagloss. Its a fairly volatile solvent based clear liquid that sets better then epoxy in my opinion. It saturates fibres better then epoxy, pushes out air easier, etches the surface, has better adhesion then epoxy, lot lower build, doesn't crack like epoxy, I haven't seen it lift yet, not even off plastic. Problem is this thing can only be bought in tiny lil bottles. I changed to using that on wood too. When it cures in a medicine cup it cures clear and handles heat a lot better then epoxy. I use it on small wood surfaces too like wooden handles for rods. Doesn't need to abrade previous application when applying a following layer, self etching

    Yeah some of the probs with epoxy are a worry for me
     
  9. michael pierzga
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    michael pierzga Senior Member

    Gee...when I was a kid we all made our own fishing rods. Epoxy was unknown... normal varnish was used. Those rods lasted for many years.

    As for boat construction...no worries. Epoxy is the most versatile, durable material for the marine environment. You must only know is physical properties to avoid its defects.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Saga, you are confusing epoxy with other thermo set plastics. Such as typical fishing rods and auto body fillers, which are usually polyester, not epoxy. Polyester does let moisture get underneith it, epoxy not so much if applied correctly.

    There is no acrylic sanding sealer that can remotely come close, to the ability of epoxy to seal wood.

    The product you're describing (U40 Permagloss) is a single part polyurethane and it's a surface finish, commonly used on fishing rods and other polyester and vinylester products. It has limited peel strength, though as a coating on a fishing rod, fairly well suited (an LPU would be better). It's not even close to the physical properties of epoxy. It lacks in every way you can measure the two, except in heat tolerance and UV resistance, in which it is superior. Heat resistance can be improved over straight epoxy, with aluminum oxide, as well as other filler materials.

    As a mater of fact, even U-40 doesn't recommend it as an adhesive or for wetout of sheathing fabrics (lousy peel strength). What they (U-40) does recommend for this application is their own epoxy!

    As far as fishing rod go, they aren't really very highly loaded, nor do they experience anything like the abrasion a hull might, so surface treatments can be a lesser grade of product.

    Michael, if metal or any time is buried in epoxy (assuming no breaches) it can't rust. Not even stainless, even though technically it should, but it doesn't because not only do your need moisture, you need air and if you deny one, the other can't occur.

    Saga, the epoxy on those rods failed because of poor protection. Epoxy needs to be protected from UV damage. If you use epoxy in the direct sun without UV protection, it doesn't last long (months), so comparing poorly prepped epoxy jobs, with other products isn't a fair comparison.

    Epoxy is hands down the preferred coating, sealing and gluing material used on wooden/composite boats. There's no debate, once you compare the respective competitors fairly. Again and quite simply, there's no one or two part polyurethane, polyester or vinylester that can come close to epoxy. This isn't a debate or argument, as frankly the testing and long term durability studies have been in for many decades and epoxy literally is the bee's knees.
     
  11. groper
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    groper Senior Member

    Ok saqa, ill give you some more info- which might help explain the problems youve seen with epoxy...

    Epoxy is not magic, it does have its limitations - like everything.
    The limitations with epoxy are as follows;

    1. General purpose epoxies are generally not UV stable - it breaksdown under UV radiation from the sun. This means it must be over coated with something that doesnt pass the UV radiation and protects it, such as a paint coating for example. The best i know of, is a 2 part linear polyester urethane coating, which is a very hard paint so its durable, and shields the epoxy from the UV perfectly.

    If its not protected from the UV, it will crack, yellow, breakdown etc, and exhibit all the problems you described earlier...

    2. General purpose Epoxy resins usually have a very low HDT or Tg, these are published in the data sheets from the manufacturer of your particular resin. Heat Distortion Temperature, or Tg, is the temperature at which the resin starts to soften and become plastic again. You cannot allow this temperature to be exceeded or the laminate can change shape, distort, suffer dramatic loss in mechanical properties etc. When it cools down again, it will set with whatever distorted shape it was forced into.

    The HDT increases with a post cure of the resin at elevated temperatures, and without post cure it slowly rises over time as the resin becomes more completely cured, this can take several months depending on ambient temperatures etc. When the resin is only 24hours room temp cured, the HDT will still be very low, most epoxies probably around 40deg C or thereabouts.

    The HDT varies between manufacturers of different epoxies, need to connsult the data sheets to know what it is for your resin.

    Because of this low HDT, you should not paint most general purpose epoxies with a dark colour paint or coating, as just the sun will heat the surface to beyond the ultimate HDT of most GP epoxies - then you have the problem. So only paint it a light colour unless you found a formulation of epoxy which has a high HDT and you have the capacity to post cure your boat in an oven.

    Epoxy resin may not be the be all and end all of all resins, there may be others out there which are superior but are not generally used for boat building because they are just too expensive to consider. Im sure NASA has some pretty cool resin systems for extreme applications, but last i checked they dont sell to the public and even if they did, youd need very deep pockets to afford it.

    Epoxy resins are very strong whilst still being affordable, hence their use in high tech composites industry - such as carbon fiber wing spars in the airbus A380, carbon fiber masts in racing yachts, racing yacht hulls, formula 1 components, and much more. You wont find polyester, acrylic, polyurethane, whatever, type resins here, as they are not strong enough to be used with carbon fiber - the resin matrix breaks down before the fibers reach their limit.

    Epoxy also has the lowest porosity of all common resin systems, so its immune to osmosis and water immersion. The only reason you will see water damage in a boat built with epoxy, is because of poor workmanship. Great care must be taken to ensure not even 1 pinhole exists whereby water can pass through it and enter the timber beneath. Attention to detail, workmanship skill, experience and procedures all contribute in this respect. This part is all on you in other words...

    You cant blame epoxy for all the problems youve seen, but rather how it was used and by whom, and their level of understanding...
     
  12. Saqa
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    Saqa Senior Member

    I think my experience with epoxy has pretty much always been its use as a finish and to a lesser extent an adhesive. tech specs for epoxy may well be superior to permagloss but its negatives of UV, heat, brittleness and adhesion combine to make it a lot less durable in the uses I have mentioned

    That scenario also needs to take into account that the blank composite of various ratios of CF, FG and polyester resin and steel or titanium frame guide and epoxy encapsulated wrap have differing rates of elasticity and a bending rod often results in cracks in the epoxy. Wraps done with PG outlast epoxy

    Loads are relative, while a bass rod in US might not see the outright forces a hull would, is the hull subject to any similar degree of bends? My rods here are often loaded to 40lbs of drag at a parabolic bend

    Thats where my lower regard and concern for epoxy comes from that and I think from my exposure to it so far it is legitimate and prolly wont be alleviated till I see the boat not having any such probs over the long run

    I haven't seen adhesion abilities of epoxy addressed apart from tech specs and positive sentiments expressed by various folks. I have mentioned it previously here that its another cause of worry for me and why it makes alternate adhesives look tempting to me. A resort here in Rakiraki Fiji coated their beer bench tops with epoxy and this was exposed to the weather. And it looked good for a few weeks and then went to buggery. I found it didn't stick to the timber properly due to the presence of surface oil residues. It breaks of in large flakes with a smooth under surface. Its just one example of swearing at the product in disgust. My recommendation for that had been decking oil but the resort owner had chosen epoxy. I have had a number of previous issues with epoxy pulling away and or lifting from various parts of timber and other surfaces due to the presence of silicone and oil contaminants

    My only experience with epoxy failing under paint has been on a panel fixed on the Volvo. The repainted the car to change color to red hot. When I first rubbed it down to metal. I found one area of rot where rust had gone through the steel nest to the windscreen rubber molding. I cut dremeled that out and rebuilt it using a knead-able epoxy putty. I am certain I took all rust out and preped the surface with enough abrasion. Well after a couple of weeks when I was finally at the cutting and polishing stage that bit of painted epoxy popped out. It had gone rubbery and gritty type brittle. Let go cleanly off the steel It had been under the primer coat for most of that time

    These are the kinds of experiences that makes its use unsettling with a labor of love project like this boat and read these boat building forums with a mild disbelief thots of 'are they talking about the same epoxy'
     
  13. Saqa
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    Saqa Senior Member

    And leads to lots of overthinking!! :D
     
  14. upchurchmr
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    upchurchmr Senior Member

    Saqa,

    There are about 1000 different epoxies.
    There are 10,000 more ways to not use it properly.

    Were the beer bench tops coated with spar varnish after the epoxy?
    Any clear epoxy in the sunlight will be killed relatively quickly, although that's faster than I would expect.

    I left a kayak with only epoxy out in the sun for about 3 years (system 3) before it began to disbond from the plywood. That's pretty long for something that is known to break down in the sun.

    Good thing you are trying to learn and won't make those mistakes, right?
    I expect you have thoroughly read the West system book. You might also look at their shop notes they publish. Lots of different uses shown there.

    I do hope you are not going to use that crappy knead-able epoxy putty stuff for your boat.

    BTW, what makes you think your fishing rods are made from epoxy? Did the manufacturer say so?
     

  15. Saqa
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    Saqa Senior Member

    The rod wraps mate, yes the manufacturer says so. Flex Coat is the most common brand and I prefer Pacific Bay for the way it wicks. U40 LS Supreme is supposed to be another good one. The rod blanks are polyester as I have mentioned previously

    All of the publications base projects on good clean wood but the real life scenario is a lot filthy. Silicone and oils are a common contaminant around timber yards and hardware stores. Isn't it ever a worry as to the handling and storage prior to your purchase? You can sand right through ply without removing some of this crap and while epoxy may look like its adhered it lets go down the road? Any way, I think at the end of the day its all hoping for the best rather then knowing exactly how it will last
     
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