Bond sheet plywood to sheet steel?

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  • 08 Apr 2018 13:36
    Reply # 6052637 on 5996444

    Arne Kverneland wrote:

    Nicholas,

    here is how I made a set of new  cockpit hatches for my Johanna, back in 1999. Johanna was an owner-finished version of the Alo28, so the hatches of this boat had been glued together from thin planks. With the glue failing, all the hatches were about to fall apart, and of course leaked a lot.

    On  taking a closer look, I found that the hatch openings had been well made with a moulded ridge and then a groove around it to drain away water. I therefore made the hatches from plain 15mm plywood. Instead of trying to make them as tight as submarine hatches, I simply skipped fitting gaskets. Instead, I made a simple ‘drip lip’ from Sikaflex, running continuously along the edges. See diagram and photos below.

    Having never seen this in use before, I tested it by laying old newspapers inside the cockpit benches (-trunks?). Paper from newspapers not only tells if it wet. It also tells if it has been wet. The result was perfectly good  -  dry newspapers. Maybe you can pick some ideas from this and use on your boat.

    I don’t claim that this will keep out all the water each time the cockpit is filled up (how often does that happen?), but if strapped down, they should only let in a few drops now and then.

    About making the foot well smaller: What about tailor-making one or two trunks which you secure in the foot-well? These will take up volume there, and in addition they will add storage space. I would of course have made them with the same sort of simple plywood lid as meioned above.

    Good luck!

    Arne

     

    hi Arne

    Thank you for the info. I have concluded that my original plan to line to cockpit and build double coamings for the locker lids is a bad one. I have used the ideas from JRA members to fomulate a revised plan. I am making new lids from ply with the double coaming built into the underside and a foam rubber gasket in the 10 mm gap which the upstand of the apperture fits into. May not be like submarine hatches but the newspaper test is the right way to go. Now, just a question of which tabloid rag to use? See picture and try not to laugh too much at my appaling joinery! Haha.

    I am photographing the making of all 4 lids for upload here that other need not reinvent the wheel....again.

    Nick


  • 04 Apr 2018 09:00
    Reply # 6014582 on 6014204
    Scott Yellig wrote:More than anything I would like to find a way to work when the weather is cold. Here and now on April 3rd it is 35 Deg F (2 Deg C). None of the adhesives or epoxy I have can be used. Pumping and mixing epoxy would be great if it worked in the cold.
    The Gougeon Bros say: "Use WEST SYSTEM 205 Fast Hardener. 205 Hardener has been designed with a polyamine system that cures well at temperatures as low as 35°F. Keep in mind the extended cure time required before removing clamps or sanding.

    "1. Warm the epoxy resin and hardener with heat lamps or keep it in a warm area until you are ready to use it. You can build a small portable hot box out of rigid sheets of foil-backed insulation, with a regular light bulb or an electric heating pad inside to maintain a temperature of 70°F–90°F. This method allows you to keep the warm resin and hardener close to your work and allows less time to cool off between dispensing and application.

    "2. Warm epoxy resin and hardener before using. As mentioned, the warmer the resin and hardener, the lower the viscosity. Thinner resin and hardener will flow through pumps better, cling less to containers and mixing equipment, and mix more thoroughly. The initial chemical reaction will get off to a better start and result in more cross-linking even if the mixture cools after it is applied to a cooler surface. The thinner mixture will initially flow out smoother and wet-out porous surfaces better. Warm the epoxy resin and hardener with heat lamps.

    "3. Dispense epoxy resin and hardener in the proper mixing ratio only. Altering the amount of hardener will seriously compromise the epoxy’s ultimate strength. WEST SYSTEM Mini Pumps are designed and calibrated to dispense the correct ratio—one full pump stroke of hardener for every one full pump stroke of resin. If you are not able to warm the resin and hardener, do not use excessive force when dispensing. Keep steady pressure on each pump and allow each pump head to make a full stroke down and a full stroke up. Remember, the resin and hardener become thicker and more difficult to pump when they are cold.

    "4. Stir the epoxy resin and hardener thoroughly. Mix the resin and hardener longer than normal (two minutes minimum) and scrape the sides and bottom of the mixing container. Use a mixing stick shaped to reach the corners of the pot. For a given volume of resin and hardener, a smaller diameter mixing pot will improve the chemical activity because the limited surface area will not dissipate heat produced by the chemical reaction.

    "If you are unable to warm the resin and hardener, allow the mixture to stand in the pot for several minutes before using. This induction period will help get the epoxy’s chemical reaction started.

    "5. Warm the epoxy bonding surface as much as possible. The epoxy will thin out as it is applied to a warm surface. It will flow out much smoother and penetrate better, resulting in a stronger bond. Warming can be done by constructing tents around small areas and heating with portable heaters, warming the area with hot air guns, hair dryers or heat lamps. Small components or materials (such as fiberglass cloth) can be warmed before use in a hot box as described in above. Avoid unvented open-flame heaters that burn kerosene or fuel oil. Unburned hydrocarbons have been known to contaminate bonding surfaces, and elevated moisture and CO2 levels may inhibit epoxy’s cure. Catalytic heaters do not appear to pose a problem unless they’re used in a confined space such as a curing tent or box.

    "Another temperature-related problem occurs throughout the year, even in warm climates, when overnight temperatures drop well below daytime temperatures. The daily variation in temperature may cause moisture contamination problems if epoxy is applied to an exposed structure or surface too early in the day. A hull, for example, that has cooled overnight may remain colder than the surrounding air until the afternoon. Water vapor can condense on the cooler surface and affect the adhesion and cure of epoxy applied over it. If the bonding area cannot be heated, allow the surface and the surrounding area to come up to air temperature before applying epoxy.

    "6. Prepare surfaces carefully between epoxy applications. When coating at cold temperatures, the slower cure can result in the formation of an amine blush on the surface. The blush feels like a waxy film on the surface of the cured epoxy. Just before applying subsequent coatings, wash the surface with warm water using a 3-M Scotchbrite™ pad. Before the water evaporates, dry the surface with plain white paper towels and sand any remaining glossy areas with medium grit sandpaper.

    "7. Allow the epoxy additional cure time before removing clamps or stressing joints. As a general rule, double the cure time for every 18°F drop in temperature. Allow extra time for pre-stressed joints and joints that will be subject to high loads.

    "8. Post-cure the epoxy if possible. Post-curing can help to complete the epoxy mixture’s cross-linking and boost the epoxy’s physical properties even after a week or two of cold temperatures. Post-curing simply is the process of applying heat to complete or speed the cure after the epoxy has reached a partial cure at ambient temperature. Elevate the temperature of the epoxy and substrate gradually to avoid thermal shock. Although any temperature elevation will improve cross-linking, try to boost the temperature to room temperature (72°F) or warmer. The time required depends on the hardener used, the post-cure temperature and how much further the cure has to go. Generally, higher post-cure temperatures require shorter post-cure times. Do not exceed 140°F and do not remove clamps or load the joint until after the final cure. CAUTION!—Heating a porous material may cause air within the material to expand and “out-gas.” If an epoxy coating applied over the material has not gelled enough before starting the post-cure, bubbles from the out-gassing material may show up in the cured coating. Allow the epoxy to reach a partial cure before post-curing.

    "A variety of post-cure techniques can be used. In some cases, your shop will naturally warm itself enough to complete the cure during the day, following a cold night. Outdoors, building a plastic tent to trap solar heat can easily boost the temperature enough for post-cure even during cool weather. Turning up the thermostat, using radiant heaters, electric heaters or electric blankets are the most common way to control the post-cure temperature in a shop. It is not necessary to heat the entire structure if you are working on only a small area. Tents of plastic or insulated board are very helpful for confining heat to specific areas and provide greater mobility with a limited heat source, both indoors and outdoors."

    I used epoxy in the winter in Nova Scotia, on an unheated boat, when the Bras d'Or Lakes were frozen to a depth of several inches.  I came to the conclusion that I muc preferred it over Cold Cure.  Drilling a 1mm dia hole in the handle of the containers holding the resin and hardener, is worth while.  This allows the container easily to replace the air taken out when you pump out liquid.  Check the tap on the hardener to ensure that there is no build up in the nozzle.  Did you know that WEST system hardener is water soluble?  This makes the pumps very easy to clean and it is worth doing this every few weeks.  (Generally, it is the hardener pumpt that clogs up, rather than the one in the resin.)

    Good luck!


    Last modified: 04 Apr 2018 09:08 | Anonymous member
  • 04 Apr 2018 02:11
    Reply # 6014204 on 6012427
    David Thatcher wrote:
    Scott Yellig wrote:


    Any thoughts or experience using LN-2000 for screw-and-glue joints below the waterline?

    Scott.


    So, further to this and my previous comments I had a talk today to a very experienced boat building friend of mine. He has built quite a few cruising yachts to his own design, the largest being 15 meters. He said that he has actually built a little boat using liquid nails type adhesives, but it was not intended as a long lived boat. This also reminded me that I have had a couple of liquid nails glue joints fail in building applications, it seemed that the adhesive had dried out within the joint. I hope that is not a characteristic of all these glues because the paneled plywood ceiling in the living area of our house is held up in part by a Liquid Nails adhesive! 

    He also said he has built a dinghy from what we in New Zealand would call a waterproof PVA glue, and apparently with good results. We discussed our Gorilla Glue and decided that would be very good for a large number of boat building applications but maybe not for the exterior. We also talked about the older Resourcinal glues which were a powder mixed with a liquid and were usually quite red in colour. There have been a lot of boats built with these glues and which after 50 years or more are still sound.

    So there are alternatives to Epoxy. Of course the thing of I love the most about Epoxy is it's gap filling characteristics.


    Thank you for the detailed response. It seems like epoxy is still the only 'right' way for a boat that is intended to last for a long time.

    More than anything I would like to find a way to work when the weather is cold. Here and now on April 3rd it is 35 Deg F (2 Deg C). None of the adhesives or epoxy I have can be used. Pumping and mixing epoxy would be great if it worked in the cold.

    I got a response from "Liquid Nails Expert" on lowes.com as well:

    Q: "Is this adhesive suitable for marine use below the waterline?"

    A: "Hi there, If the adhesive will be constantly exposed underwater, unfortunately no."

    The marketing literature says, "Excellent, instant water-resistance". I guess then emphasis should be on the 'resistance' and not on the 'Excellent'.

    Thanks to everyone for the discussion. I think I will still buy some of this Fuze It and see how a joint holds up sitting outside for a year or so.

  • 04 Apr 2018 01:30
    Reply # 6014151 on 6012506
    Annie Hill wrote:
    Darren Bos wrote:Try boiling your test pieces for 30 minutes and then test them to failure again.
    I shouldn't try doing that with epoxy, if I were you!
    I have with West Systems, which is not particularly heat tolerant.  Maybe I should have added more detail to the description.  Boil, let cool and dry a bit, then test.  This is a pretty common test for plywood.  I do it with plywood I use near water.  Some fall apart completely after boiling, others are largely unaffected.  A better test would be to let the samples sit in water for a long time.  However, that test takes......
  • 03 Apr 2018 09:02
    Reply # 6012546 on 6012505
    Annie Hill wrote: As I have found that paint doesn't stick that well to plywood in the long term, unless it has been pre-coated with epoxy, this seems like a drawback for something intended to last many years.  If you are going to seal the wood with epoxy, you may as well glue with it.

    Having built a plywood boat that's intended to stay afloat, the only sensible thing is to sheath it outside, and preferably in the bilge as well, with epoxy and glass or Dynel. But that may not entirely preclude glued and screwed construction with something that is gap-filling, as epoxy is, but one-part. Sadly, resorcinol requires very close-fitting joints, or we'd all still be using it.
  • 03 Apr 2018 08:35
    Reply # 6012524 on 5995742

    Something that might be worth testing is Bostik's Simson MSR Construction Adhesive. It is recommended for bonding and sealing hull to deck joints, and other above water uses, but whether it would work well underwater, I don't know.

    FEATURES

    - Solvent and isocyanate free.

    - Very good UV resistance and ageing properties; long time resistance against fresh and salt water.

    - Good adhesion on commonly used materials without the use of a primer.

    - Elastic in a temperature range of -40°C to +100°C.

    - Application temperature range +5˚ C to +35˚ C
    Last modified: 03 Apr 2018 09:05 | Anonymous member
  • 03 Apr 2018 08:33
    Reply # 6012523 on 6012506
    Annie Hill wrote:
    Darren Bos wrote:Try boiling your test pieces for 30 minutes and then test them to failure again.
    I shouldn't try doing that with epoxy, if I were you!
    Yes, Because as I once found out when I tried to repair a car radiator with epoxy, this material does not stand up well to heat. Needless to say the epoxy softened and the reapair failed after 30 minutes of driving.
  • 03 Apr 2018 08:09
    Reply # 6012506 on 6012303
    Darren Bos wrote:Try boiling your test pieces for 30 minutes and then test them to failure again.
    I shouldn't try doing that with epoxy, if I were you!
  • 03 Apr 2018 08:07
    Reply # 6012505 on 6010531
    David Thatcher wrote:

    We have an adhesive here in New Zealand called Gorilla Glue, which I imagine is available in other countries. I know that is used a lot in boatbuilding and seems to have properties which allows it to expand into the wood fibers for an effective bond. It also involves no mixing of different parts the way epoxy does. However I do not know if anyone has used it in hull construction such as gluing on the exterior hull planking. 

    Marcus used Gorilla on Freebie, to try it out.  He reckons that while the plywood appears to stay stuck, the solid wood to plywood joints are much less reliable and wood to wood scarfs tend eventually to open up.  It would probably be OK if you maintained it varefully, ensuring that the paint film never gave way. As I have found that paint doesn't stick that well to plywood in the long term, unless it has been pre-coated with epoxy, this seems like a drawback for something intended to last many years.  If you are going to seal the wood with epoxy, you may as well glue with it.
  • 03 Apr 2018 06:42
    Reply # 6012427 on 6010378
    Scott Yellig wrote:


    Any thoughts or experience using LN-2000 for screw-and-glue joints below the waterline?

    Scott.


    So, further to this and my previous comments I had a talk today to a very experienced boat building friend of mine. He has built quite a few cruising yachts to his own design, the largest being 15 meters. He said that he has actually built a little boat using liquid nails type adhesives, but it was not intended as a long lived boat. This also reminded me that I have had a couple of liquid nails glue joints fail in building applications, it seemed that the adhesive had dried out within the joint. I hope that is not a characteristic of all these glues because the paneled plywood ceiling in the living area of our house is held up in part by a Liquid Nails adhesive! 

    He also said he has built a dinghy from what we in New Zealand would call a waterproof PVA glue, and apparently with good results. We discussed our Gorilla Glue and decided that would be very good for a large number of boat building applications but maybe not for the exterior. We also talked about the older Resourcinal glues which were a powder mixed with a liquid and were usually quite red in colour. There have been a lot of boats built with these glues and which after 50 years or more are still sound.

    So there are alternatives to Epoxy. Of course the thing of I love the most about Epoxy is it's gap filling characteristics.

    Last modified: 03 Apr 2018 06:44 | Anonymous member
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