Acorn to Arabella: Testing Epoxies

When we got the call from the Acorn to Arabella boatbuilders about their Resorcinol problems, we wanted to help out. We’ve been supporting the boatbuilding duo since they started by offering supplies and support, so we were, of course, happy to oblige them by shipping them a variety of epoxies to test out.  We know how valuable boatbuilders find our Thixo to be, so we added some of the pre-mixed thickened epoxy tubes to a sampling of traditional epoxies and shipped them off. We were thrilled to learn that their thorough testing pointed to Thixo as the top-performing epoxy for their job.

Their testing led to them switch to using epoxy for the graving pieces, but they are sticking with a fresh batch of Resorcinol for the scarf joints on the planks that they will be bending and twisting into place. Obviously this is not a job they have the luxury of redoing – or not easily – so they are taking the time to do the job right this first time – even if it means taking a step back and rethinking the process. 


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26 responses to “Acorn to Arabella: Testing Epoxies

    1. I have used resorcinol many years ago on a sailboat project and more recently have been using epoxy on fiberglass boat projects. So I am familiar with both glues. Epoxy is far superior in tensile strengths compared to resorcinol and I just don’t understand why you would continue to use it in the scarf joints or any other glue joint in you project. Think of the pounding those planks will have when hitting waves in heavy weather. I would want epoxy holding those boards together. we have

      1. Great testing of the glue joints. Two things I might add to the testing if your concern is about a dry joint holding. Spread the epoxy on both glue surfaces, and allow more time before clamping. This will add more insurance against squeeze out starving the joint. Also, since a scarf joint involves some wicking of the glue in end grain, this will also help.

      2. Brad, seriously consider why this epoxy test is engineered in the manner presented in the video and not as a scarf board is glued together with the resorcinol.
        I am seriously disappointed with Total Boat for doing this. Everyone should do their own extensive testing specific to an application.
        Epoxy and composites (fiberglass) makes sense, wood? not so much. Resorcinol has been around sense 1948, used with wood exclusively in boats, planes, plywood even today. This video would suggest it is not yet ready to take you across an Ocean in a wood boat.

  1. Some info that may be of use
    Phenol-Resorcinol Formaldehyde Resin
    Liquid Hardener & Liquid Resin – NO POWDER
    BS EN 301

    There are various systems within the Casco range to meet varying application method and end user requirements. A typical system is as follows:
    Cascosinol Phenol Rescorcinol Adhesive 1711 with Hardener 2520
    The combination Cascosinol 1711 with hardener 2520 is approved by NTI, Norway, Otto-Graf insitut (FMPA), Germany, SKO/KOMO (DHBC N0. 32389), Holland for the Production of load-bearing timber structures.
    The combination can also be used in door production, lamination, finger jointing and other applications in the wood working industry, where there is demand for high water and weather resistance for the joints. The combination has short pressing times even at lower pressing times.

    Technical Data


    1711 Phenol Resorcinol glue

    Delivery form

    1711 liquid
    2520 liquid


    1711 dark brown
    2520 greyish brown


    Brookfield LVT, sp. 4, 12 r/min, 25°C
    1711 approx. 5000 mPa.s
    2520 approx. 8000 mPa.s


    1711 approx. 1150 kg/m³
    2520 approx. 1220 kg/m³

    Dry solids

    1711 approx. 56%


    1711 approx. 8
    2520 approx. 5

    Flash Point

    1711 70°C
    2520 85°C

    Other Data

    Properties of the bond-line

    Cascosinol 1711 with hardener 2520 fulfils the requirements according to EN 301 (for glue type I and II, service classes 1, 2, 3), EN 391, EN 392 and DIN 68141.

    Storage life

    1711 6 months at 20°C in well closed packaging
    2520 6 months at 20°C in well closed packaging

    If the packaging is left open when not in use the glue is susceptible to skin formation on the surface. To avoid this the packaging should be closed when not in use

    Directions for use

    Application tools

    Roller spreader, ribbon spreader etc

    Mixing ratio

    1711 100 parts by weight
    2520 15 parts by weight

    The accuracy in the hardener amount shall be ± pbw.

    Pot life

    Temperature of glue mix 10°C 15°C 20°C 25°C 30°C
    Pot life in hours 4½ 2¼ 1¼ 2/3 ½

    When preparing large amounts of glue mixture, it is recommended to cool the glue to 10-15°C and after that add the hardener to extend the pot life.

    Wood temperature

    The temperature should not be lower than 20°C.

    Moisture content of the wood

    8 – 14 %. For the production of laminated beams 10 – 12%
    Planing of the wood

    Newly planed surfaces give the best gluing result. For best result at laminated mean production the timber must be smoothly planed. For optimum bonding strength the planing should take place within 24 hours before gluing.

    Glue spread

    For production of laminated beams a minimum glue spread of 400-450 g/m² single-sided is recommended. A reduction of the glue spread, e.g. at very short assembly times, is only allowed to be done together with the Casco Products Technical Advisors, depending on the production parameters for the production line in question. This optimization implies that the set parameters are followed and that a continuous control of the adhesion quality is made by means of delamination tests. At HF gluing a glue spread of 250-350 g/m² single-sided is recommended. At other applications: 150-300 g/m².

    Difficult-to-glue wood or hardwood may require double spreading in amounts of 150-200 g/m² on each side.

    Pressing temperature

    Soft wood can be glued at a joint temperature of 20°C. To be sure to obtain a good result heating of the glue joint to 30°C is recommended. When gluing hard wood the temperature of the glue joint must be at least 40°C. Constructions with tensions and hard woods require at least 60°C to obtain adequate strength. Lowest pressing temperature has to be tried out. After the pressure is applied the heating can start.


    Minimum 0,5 MPa for soft wood
    Minimum 1,0 MPa for hard wood

    In laminated beam production:
    Minimum 0,7 MPa for 33mm lamellas
    Minimum 0,9 MPa for 45mm lamellas

    According to DIN 1052/1-A1 the maximum allowed thickness of lamellae is 42mm.

    Pressing time

    The pressing time depends on the temperature, the distance to the innermost glue joint, the glue spread, etc. The table below may be used as a guideline.

    Glue joint temperature

    Minimum time for curing at indicated glue joint temperature


    4 hours
    2 hours
    45 min
    12 min
    3 min
    1 min

  2. You were spreading very COLD and therefore very THICK epoxies so when they warmed up they dripped out a bit… that’s why the clamps were ready to fall off. You timbers DID NOT shrink.

    In real life you would want to scrape/trim off the excess while the epoxy is “green” and avoid having to grind it the next day.

    Your Resorcinol video a few weeks ago showed lumpy glue coming out of the jug… a possible red flag for too old.

    I use WEST system resin; for decades. West stands for Wood Epoxy Saturation Technique, from 1979 or so.

  3. There’s lots of scuttlebutt out there to the effect that epoxy doesn’t work well with oak. These experiments appear to blow those theories out of the water, UNLESS, perhaps, the joints start out strong but somehow deteriorate and fail over time…

    1. I saw the scuttlebutt and debates too when I was looking for a way to replace white oak steam bent frames on my 70 year old 33′ cabin cruiser. I had used a lot of West Systems epoxy and thought I could laminate the frames in place since they have to be snaked in between stringers and cabins sides. The epoxy held fine until the boat sat in the water and the bottom ends of the frames saturated with water. Both of the frames I replaces delaminated below the water line. The next year I tried Resorcinol on another frame. Although it was harder to work with since it cured faster, the results were better. The frame laminations held even in wet cycling. I believe the people who were using epoxy on white oak on a boat that was stored out of the water and only set in the water when used occasionally (i.e. without saturating the wood) had good success. Those who used it where the wood was saturated and wet cycled did not have good success. Just my experience and take away from the debates I read.

    2. Welp,I can tell you all my WEST was chipping off in credit card pieces..BUT I can tell you ALSO my wood was pretty saturated due to..A leaky rudder stuffing or a leaky rear deck hatch so there was always water in the bilge..I also believe that the wood needs to breathe and the WEST system holds it All in..This boat of mine was West systemed on the entire outside..and about 50% of the inside (Bulkheads) and Keel..as well as a few ribs in the last 8-9 foot..Where the water laid due to this leak and the bilge pump not evacuating the entire amount. So I have about 6 soft ribs & a inch or so of Rotton wood on top of the OAK keel…Now after chipping the West off and getting SOFT fibers out. Next I’m using SMITH’s CPES the whole deal..Then maybe on a few of the ribs I’ll put some of that Flexing WEST on a few of those compromised ribs..Just for some extra strength.

      1. @ Patrick Palmer. Classic case of hype meeting reality in real world conditions. The best coating for oak in a bilge situation is the old active oil based red lead primer or white lead primer. Now it’s not allowed to be sold in the USA in case some parent allows their little goat to graze in the bilges of their live-aboard.

  4. I have used resorcinol many years ago on a sailboat project and more recently have been using epoxy on fiberglass boat projects. So I am familiar with both glues. Epoxy is far superior in tensile strengths compared to resorcinol and I just don’t understand why you would continue to use it in the scarf joints or any other glue joint in you project. Think of the pounding those planks will have when hitting waves in heavy weather. I would want epoxy holding those boards together.

  5. I yuse epoxy wen timber does nod fit or djuste completly ell and in that case I can not use resorcinol that need a very thin layer of glue because it braks wen wood is working by flexion and the water can came in .
    António Cardoso

  6. I am physicist/woodworker with minors in chemistry/EE. A large part of my career involved working with surfaces in the semiconductor and defense industries. People’s lives and national security were involved.
    Adhesion is roughly adhesive ( glue-surface) and cohesive ( within glue). The adhesive energies vary from very weak (eg Van Der Waal) to very strong polar hydrogen bonding or chemical bonding involving actual electron transfer. Optical contact bonding between two clean and polished glass surfaces is an example of polar type. Moly-manganese furnace bonding of inert ceramics involves both surface diffusion and chemical reaction with surface.
    Cohesive failure usually involves over stressing glues that have become embrittled or stressors due to poor joint design. Since the resorcinol glue was outdated, I am not sure jumping to epoxy and significant testing was warranted. Both glue types (and others) have necessary structural strengths.
    Lastly, I found clamping and “strength” testing questionable. Real world testing might involve repeated wet/dry cycles in salt water.

    1. “Adhesion is roughly adhesive ( glue-surface) and cohesive ( within glue). The adhesive energies vary from very weak (eg Van Der Waal) to very strong polar hydrogen bonding or chemical bonding involving actual electron transfer.”

      Thank you for this comment as it serves to put the focus on the very real advantage that resorcinol brings to the table in boatbuilding and boat repair

      With resorcinol glue, a chemical bond is possible if laminars or scarf joints surfaces are very smooth and near perfect. With epoxies, the best that can be achieved is a mechanical bond subject to the degradation of the plastic glue line. The electron bonding is the desired result and will not occur if the glue line is too thick. Clamping pressure must remain throughout the specified time period/ambient curing temperature. Moisture content of both surfaces must be within the specified range for the manufacturer’s glue. The laminated result will be stronger than the parent material used for the joint. The joint will not be affected by wet or dry cycles, fungus, UV, or stress. It just has to be done correctly, gentlemen.
      Note to crew: Great job on the videos and wonderful craftsmanship on Arabella.

      1. Re: Timothy E. Tucker’s reply
        I have heard/seen somewhere that resorcinol is capable of “chemical bonding” with wood. However, realize that epoxies get their adhesive properties from being highly polar in nature, and adhesion theories predict that strong chemical bonding is not necessarily a requirement for a strong joint. However, the real world complication has to do with the most important chemical on earth – water. Water has the unique property of being both highly polar and very small. Therefore, it has the ability to displace the glue/substrate interface over time. In terms of total adhesive surface energy the water/substrate is larger than the glue/substrate. Epoxies also have low intrinsic water permeability and can penetrate wood to some extent. These factors help minimize the water displacement reaction that may occur in saturated environment.
        So, epoxies are not strictly just mechanically bonded, and the adhesive nature of the surface bonding is independent of glue line thickness. However, many structural glues are somewhat brittle in nature, and can give the appearance of poor surface bonding because of stress concentration during testing. Under close inspection the glue surface will exhibit wood fibers ripped from wood surface.

        1. See my previous real world comment, based on 30+ years of boat repair/boat building experience with resorcinol, epoxies, and urethane adhesives.
          I would secure all installed below waterline planking scarfs with a close fitting, properly edge beveled and scuppered, through bolted and urethane sealant bedded, white oak Butt Block! Consider it insurance.

  7. I’m sure you guys will figure it out. Even cheap epoxies will work the way the expensive ones do on wood. But what happens when the wood is soaking wet? Will the epoxies peal off. Does the Resorcinol soak in a little deeper and bite in a little harder? I’ve sanded a plywood surface glued with a Resorcinol colored glue and found the coloring deep in the grain of the wood. Never tried that with a hardwood. Hmmm.

  8. Very disappointed with Total Boat for publishing this. It does reflect a lack of integrity toward other videos and products.

    1. Re: Brian Johnson’s “Integrity”

      As stated, your statement is a real head scratcher. Maybe you also object to seeing the U.S. flag on all that foreign aid.
      Go Jamestown.

      1. No, the test is carefully engineered for appearances. It has no relevance to any application. But, logically that would be where they started (gluing the scarf boards with Epoxy). The test loads the epoxy in sheer, with the grain so the oak splits. Notice the angle of the long v cut, just deep enough to accommodate the top of the bottle jack. It is plausible, similar results could be achieved with Elmer’s, white school glue. (tested in the same manner)
        The video makes it clear “fresh” Resorcinol is still appropriate for scarf joints and there is good reason the epoxy was not used/tested in that manner.

  9. Pingback: Acorn to Arabella: Planking with a Twist - TotalBoat

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