Plywood Decking -Sole replacing questions.

Discussion in 'Boating Discussion' started by willit float, Sep 18, 2016.

  1. willit float

    willit float Member

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    Sweet...
     
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  2. willit float

    willit float Member

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    Thanks I'll use all this info and others. Appreciate it!
     
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  3. willit float

    willit float Member

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    I was told some years ago that the deck-floor has to have a thin gap all the way around to allow for flex and movement without hard vibration or binding. Reading info on line I see the edge embedded with a rigid mix as discussed here. The original floor in this boat had the long "grain" side running bow to stern with the direction of the stringers and risers-joists for the deck foundation. I did some testing and figured that with foam under for support it would be fine.
     
  4. willit float

    willit float Member

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    I've decided to go with marine grade 3/4". I did some testing with 3/4 exterior and 3/4 marine grade. The marine grade smokes the standard acx. Then installing screws the marine grade seemed better by then I was convinced.
     
  5. willit float

    willit float Member

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    Like this ... Thanks
     
  6. willit float

    willit float Member

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    Thanks for the great info. Question on the screws.. Many people say to use stainless steel screws on boats not left in water like a slip. The boat was built originally using bronze wood screws.
    The info I see online has sheet metal screws in stainless steel as the all purpose screw. Does it really make a difference on wood screw with the shank or threaded to the head?
     
  7. Normslanding

    Normslanding I've posted enough I should edit this section

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    A couple of things........... Marine Plywood is worth the price. And Stainless Steel screws that are encapsulated (sealed up) behind resin/paint will turn to black goo when there is moisture and no air. Proper installation of Marine grade Bronze screws is a little more frustrating due to striped heads, but gives great longevity, and no goo.
     
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  8. undone

    undone Member

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    You need to be careful buying "Marine plywood" it isn't one type of wood or construction, and much of it on the market is very low grade. Not all are that rot resistant either, nor are they free of voids.

    This type of application isn't one that requires the strongest wood possible, rot resistance is more important, that's why builders now use (and have for a decade or two) PT plywood designed for the marine industry. This type of ply is normally fairly good, quality hasn't been an issue.
     
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  9. willit float

    willit float Member

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    Bronze it is. Thanks
     
  10. willit float

    willit float Member

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    I'll check that out. Thanks
     
  11. knot keely

    knot keely Well-Known "Member"

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    Don't many boat builders remove the screws prior glassing to avoid the screw corrosion issue all together??

    I could swear I saw the Andersons talk about that at some point.
     
  12. sickcat

    sickcat Silverback

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    If you glass both sides of that 3/4 it will be rock solid.

    Lots of ways to do it well. For example I have a 16; Glaspar Avalon That I am going to chop 2 feet out of so I can tie up at the docks at Catalina. It originally had a 3/16 deck glassed on top on it that only had about 1 squarre foot of rot and it is a 1966. Other than the bad spot it was very solid. The boat has 5 fiberglass stringers (no wood) so that certainly helped.

    I will use a good quality 1/2 ply and glass both sides with 8oz cloth. Not marine grade but a much better quality than the HD CDX crap. It will be more solid than ever and certainly outlive me.
     
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  13. undone

    undone Member

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    Yes, the wood/glass floors are frequenlty glued in place, they either weight the floor down or put some screws in it until the glue dries, then remove them. Others just leave the screws in place.

    More modern designs bond the liner/stringer system in place and use weights until it cures.
     
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  14. MATTANZA

    MATTANZA old man of the sea, in training.

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    best marine plywood is hydrotek. used it to recore the deck panels on my boat. it's a dream to work with, but you'll need to used epoxy to seal it. if you are using chopped strand matt, you'll need both poly , and epoxy. csm, is made with polyester resin, epoxy will not saturate the csm.here's some relevant info.....
    Epoxy Resin vs. Vinylesters and Polyester



    [​IMG]
























    Here is some technical data that you may find interesting regarding the differences between Epoxy Resin and Vinylester or Poyester Resins.



    In the marine industry, liquid plastics, namely epoxies, polyesters, and vinylesters are used to saturate (wet out) the fibers of wood, glass, kevlar amarid, or carbon to form a fiber reinforced plastic (FRP). To create a quality part, adhesion to the fibers is the most important factor. Not all resins keep their grip on fibers equally.



    Epoxy resin is known in the marine industry for its incredible toughness and bonding strength. Quality epoxy resins stick to other materials with 2,000-p.s.i. vs. only 500-p.s.i. for vinylester resins and less for polyesters. In areas that must be able to flex and strain WITH the fibers without micro-fracturing, epoxy resins offer much greater capability. Cured epoxy tends to be very resistant to moisture absorption. Epoxy resin will bond dissimilar or already-cured materials which makes repair work that is very reliable and strong. Epoxy actually bonds to all sorts of fibers very well and also offers excellent results in repair-ability when it is used to bond two different materials together.



    Vinylester resins are stronger than polyester resins and cheaper than epoxy resins. Vinylester resins utilize a polyester resin type of cross-linking molecules in the bonding process. Vinylester is a hybrid form of polyester resin which has been toughened with epoxy molecules within the main moleculer structure. Vinyester resins offer better resistance to moisture absorption than polyester resins but it's downside is in the use of liquid styrene to thin it out (not god to breath that stuff) and its sensitivity to atmospheric moisture and temperature. Sometimes it won't cure if the atmospheric conditions are not right. It also has difficulty in bonding dissimilar and already-cured materials. It is not unusual for repair patches on vinylester resin canoes to delaminate or peel off. As vinylester resin ages, it becomes a different resin so new vinylester resin sometimes resists bonding to your older canoe. It is also known that vinylester resins bond very well to fiberglass, but offer a poor bond to kevlar and carbon fibers. Do to the touchy nature of vinylester resin, careful surface preparation is necessary if reasonable adhesion is desired for any repair work.



    Polyester resin is the cheapest resin available in the marine industry and offers the poorest adhesion, has the highest water absorption, highest shrinkage, and high VOC's. Polyester resin is only compatible with fiberglass fibers and is best suited to building things that are not weight sensitive. It is also not tough and fractures easily. Polyesters tend to end up with micro-cracks and are tough to re-bond and suffer from osmotic blistering when untreated by an epoxy resin barrier to water. This is really cheap stuff.



    Summary - Epoxy resin has far more to offer in its ability to flex, prevent delamination, and ease of use for repairwork. Using epoxy resin leads to better quality products.
     
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  15. undone

    undone Member

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    Interesting, but it sounds like an advertising campaign made by an epoxy supplier.

    After more than 45 years of working with all these resins and building just about every product you can imagine out of them, plus the last 20 years doing tech service for them, I can tell you that unless the product has been highly engineered you aren't taking advantage of the superior properties the epoxy has to offer.

    Let's use the bond strength claims, we can use the ones they supplied. It shows epoxy at 4 times the PSI of VE, then it just says less for polyester. Since the vast majority of boats are built with polyetser, and you don't see delamination as a huge problem, then it must be up to the job. Let's say the max load experienced by the bond is 200 psi, and polyester is 300 PSI, it means none of the resins will fail in normal use. And since polyester is used about 99% of the time, it must work. Exceeding the bond strength by almost 7 fold will have little benefit. ( I wouldn't doubt the numbers were cherry picked to show the widest gap possible)

    Yes VE is an upgrade, and many builders use it as a skin in the hull to help prevent the possibility of blisters, it's a very good idea, but the thin skin doesn't really add anything to the strength of the hull. Very few boat builders use VE for the entire build.

    Yes, glass is about the only fiber that should be used with polyetser, it doesn't have the physical properties to take advantage of the other fibers. VE does a better job, epoxy is the way to go if you really want the strength though, but it needs to be engineered correctly or you're wasting money.

    Epoxy is typically harder to use, especially by a rookie, it's one of the main reasons more boats aren't made with epoxy. The other is health related, while it has little to no odor, some (most) common epoxies can cause severe health issues, once sensitized there's not much you can do, even minor contact can cause extreme reactions.
    Styrene (what you smell with polyetser) has a very obnoxious odor even at very low concentrations, this is a very good thing. Your nose can detect styrene at such low levels that the average person wouldn't stay in the room for more than a minute at levels far lower than what's allowed in the workplace. So the chances of someone having health issues from using it for a one time repair are so low I'm not sure it would be much of a concern.

    In many applications using epoxy is like buying a 1 ton diesel duely to tow a 14' aluminum boat, it'll do a fantastic job, but so may a Ford Escape.
     
    Last edited: Sep 26, 2016
  16. jigstrike

    jigstrike SCUBA Spearing Daddy

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    Stainless screw are great, but as noted they have an issue when completely covered in the absence of oxygen. Alternately, you may try coated deck screws. The real bond of this repair is the resin glueing the floor to the stringers and cross pieces. The screws are function more like clamps to pull things tight untill the glue sets. Coated screws ahould survive well under wvwrything and cost less than bronze and may be self tapping
     
  17. MATTANZA

    MATTANZA old man of the sea, in training.

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    RICK
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    boat building, and repairing are 2 different animals. boats are built in molds, so the laminating process is totally different then repairing a deck. i'd go the west system or systems three {laminating epoxy}. i'd use vinlyester if you're using csm as a stiffener and cover or you can use woven roving , much stronger, with epoxy. epoxy is the way to go. been around boat builders my whole life and I've seen a lot of failures , and it's due to cutting corners and misinformation. I used mahogany plywood , so epoxy was a must. I used ve for the lam process with csm to cloth/plywood , and epoxy as the final coats. the panels , way stiffer than oem, and are both bullet proof, and going strong for 4+ years, and my boat gets run hard. no issues. I would use nothing less than ve, and only where I had to. I've found it's a lot easier to work with epoxies, 3:1 or 1:1 is a lot easier to mix than a 1% ratio. epoxies also have various hardners to off set temp , and set up times , {pot life}, comparing epoxies to poly's is like comparing a cell phone to 2 tin cans , lol! to each his own, I prefer overkill to a possibility of failure, you can also tow an aluminum boat with a Yugo .......
     
  18. undone

    undone Member

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    I sell West System products, I know the people, been to their week long training classes in their lab, they make great products. I also know and have worked for, the major VE and polyetser manufacturers, I do training classes for the builders and repair shops on how to use the products correctly. Failures are rarely the fault of the actual resin, that is unless someone chose a resin (epoxy or polyester) that was not the correct one for the job, there are hundreds of different formulas of each. The failures occur from lack of knowledge and poor workmanship, not the inability of the product to hold up if used correctly. Repair shops and and others love to blame something other than their ability to do the job correctly when something fails.
     
    Last edited: Sep 27, 2016
  19. undone

    undone Member

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    Here is something I posted several years ago on another site, but it was covering the same subject.



    I deal with many different markets in the composites industry, not just the marine end of it and for the most part I agree with XstreamViking.

    Since I don't see bond failure as an issue in anything I've built or repaired with polyester or VE over the last 40+ years, and it isn't really an issue for my customers, which have built many thousands of boats themselves, it seems the bond issue is more a case of poor workmanship or bad design. The prep needed for either type of resin is the same, epoxy may let you do a poor job with a little better chance of success though.

    When I see bond failures it’s typically when a rookie decides to do a F/G repair on his boat (you can insert any item in place of a boat) and heads down the hardware store. They buy whatever resin it is that has been sitting on the shelf for a couple of years and some cloth (no mat), no sand paper, acetone, or any other needed items. They pull the boat out from under a tree in the side yard, use a damp cloth to move some of the leaves away and make a feeble attempt to wipe off the green and brown slime that has accumulated on the surface for the last 10 years.

    At this point they remember they should sand the surface, so they go back in the garage and find an old piece of fairly fine grit sand paper that has been used many times on other projects. Now he makes a couple of half hearted passes over the surface with the sand paper, which instantly clogs up with the damp green gunk still on the surface. It gets one more wipe with an old rag that was last used to check the oil on his truck and he now feels he’s ready to catalyze some resin.

    Next, how much catalyst to add…..was that 2%, 20%, 50%...and how do you know what 2% is…or did they say 2 drops per quart…oh well, it’s not that important, I’ll just poor a little in…oops…too much (I think). Now where's that old paint brush I used to paint the trim on the windows a couple of years ago…..there it is…wow, maybe I should have cleaned it better…sort of stiff. OK, now I just pour some resin on the surface and lay this 1’x1’ piece of cloth on it, I only “prepped” a 6”x6” square, but it should be fine…maybe even stronger. Let’s see, what do I do with all this extra resin…it sure took a lot less to wet out that piece of cloth than I thought. I think I’ll just pour the rest of it around on some of the other cracks to strengthen other areas too…don’t want to waste it. Looks like rain…good thing I’m done…now I’ll go in and have a beer.

    A week later he heads to the lake puts the boat in the water and it doesn’t leak, it was a successful repair. Two weeks later he runs over a big wake while pulling a tuber and the repair starts to leak, he reaches down and grabs a corner of the cloth that is sticking up, the part he couldn’t get to lay down, must have been because it was folded over. He pulls and the cloth comes right off with little effort , and he's shocked. That night he goes online and asks on a boat forum why it failed, he tells them he did everything according the directions but it still failed. He's told that polyester resin is very weak, won’t stick to anything and that he needs to use epoxy, so he orders some online the next day. While waiting for the epoxy to arrive he starts to clean off the “failed” polyester resin and finds it is sticking very well in some areas and won’t chip off. This time the neighbor sees what he's doing and offers him the use of a small grinder, this speeds things up dramatically and he removes all of the old resin and green slime that was still on the surface. The epoxy is delivered and so is some of the correct glass, he also ordered the roller and squeegee the guys online said he would need, plus he picked up some new brushes.

    This time he remembers its a 1 to 1 mix (and with a little work he can figure how much of each that is), stirs it well and from his experience before, plus the advise from the forum, he uses the correct amount of resin to wet out the several layers of glass to build the surface back up and works all the bubbles out.

    This time the repair holds up, he goes back online to the forum, he’s one of the experts on the forum now because he’s done a repair before, and tells everyone how bad polyester is and that they should never use it and epoxy is the only thing that works. Sound familiar.


    Back to the other stuff.

    If properly designed an epoxy hull will be no stronger than a polyester or VE hull designed for the same use, only lighter, this is where the DIYer comes up short. They tend to use about the same laminate schedule as they would with polyester or VE, so they have the same weight with a much higher cost and an over built part, or repair, this results in no advantage or benefits from using epoxy. I hear people frequently say that you will save weight by doing an epoxy repair, well it would need to be a very large repair to make a meaningful difference in the weight savings. You may save the weight of a six pack on a large repair...and well….that may be very important to some people…more beer.

    As for strength, most epoxies list their physical properties after being post cured, if you don't post cure it don't expect to get close to them. Also any medium to slow cure epoxy really needs to be post cured, they fall well short of the listed properties without this step.

    The other issue with strength is when using low viscosity epoxy infusion resins is they tend to be much weaker than higher viscosity resins. This has to do with how they reduce the viscosity. What can happen is the physical properties can drop to a level equal to, or below those of a VE resin.

    Even the many thousands of low quality ski boats built to a very low price point with the cheapest polyester resin available rarely have an actual resin/glass failure, the wood rots and they tend to hold up OK until the wood is nothing more than pulp. And even then the owner has no clue there is an issue until his foot falls through the deck.

    As for high end custom or semi custom boats, why not use epoxy, it’s a great product and will allow you to build a much lighter craft. These tend to be purchased in relatively small numbers by people that can afford this type of toy, not the every day guy.

    As for the type of boats repaired or modified on this site, epoxy may be a good choice for them, that is if your plan is to put the largest outboard on it you can and then push it to the limit. Although a VE is easily up to the job. For the many more that just want their ski or fishing boat back on the water, I can’t see a good reason for using epoxy.
     
    Last edited: Sep 30, 2016

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