Working with Weather: Applying Epoxy in Winter Conditions

While sailing on Malua, I watch the weather forecast every morning and evening as they are produced by our local Bureau of Meteorology.  In addition, I look at Windy with their different forecast models from data around the world.  Using the wind data, I plan my route, departure time, and develop a sailing plan.  There is very little one can do to modify the prediction—only modify one's plans.

That is exactly what I had to do when planning to apply epoxy resin and fibreglass cloth to the hull and deck of the kayak.  I had finished the sanding, separated the two sections of the kayak, and placed them on trestles ready to apply the epoxy, only the weather forecasts for the next two weeks did not look good.  They showed rain, frost, and only moderately warm days. I resigned myself to a long delay in the construction, BUT...

Industrial space heater

My neighbour built a very large house with a 6-car garage at ground level next to us—thankfully while we were sailing in Europe.  I went to talk to him, and he volunteered to lend me his industrial diesel-powered space heater to heat my 2-car garage where I am building the kayak.

Plan B had just fallen into place.  I could modify at least the temperature and, to some extent, the humidity of the build environment.  It was then only a question of choosing days with adequate daytime temperature which I could increase to above 20°C and nights that did not drop below freezing.

Now, the Australian winter officially starts on 1 June, and the forecast indicated there would be three days thereafter that would have daytime temperatures of 17°C  and nights of 4°C to 5°C.

Time to swing into action and get everything ready for the epoxy day.

I placed the 200gm fibreglass cloth on the upturned hull and cut a skirt around the sides, then started to brush it smooth for the next day's wet-out.  It looked good.  That night, I took the two West System containers into the house and put them next to the house heater output ducts so they would warm to increase their viscosity.  I also got out a large cooking pot and my portable induction plate and put them ready with a grid to keep the containers out of a layer of water.  During the wetting-out, the containers would stand in the pot over boiling water to keep them hot.  I checked the dispensing pumps on the 105 Resin and 207 slow clear hardener and found the hardener pump did not always give the correct volume—keep that in mind.  Squeegees and rubber gloves were at the ready, plus a small high-density foam paint roller and tray.

Start of day foggy but no rain

The day dawned, and I checked the forecast. The temperature was just above 5°C but would reach a high of 17°C at about 2:00 in the afternoon, then drop at 7:00 towards 5°C.  Unfortunately, there was a thick fog that blanketed the area.

Temperature range

I started the industrial space heater and set it at the end of the carport.  It soon became obvious that the hot air was heating the immediate surroundings, but the sides of the carport being marginally open permitted cold air to replace the warm air as it rose.  Off to the stack of blue plastic tarpaulins I had used in the construction of Malua, and I started to hang them from the gutter beams right down to the floor on the open side of the carport.  One could immediately feel the temperature rise, although there were enough holes for the heater to struggle to get the environment above 22°C.

Start of day Heater in background Epoxy foreground

At 10:00, I started the first epoxy wet-out of the fibreglass cloth.  I built my first fibreglass surfboard in 1964 and have played with polyester and vinylester resins ever since, including building the hard dogger for Malua.  Furthermore, in the previous month I had assisted my friend Jim to epoxy his diagonal-planked freighter canoe, so the epoxy system was not new to me.

Wetting out cloth with squeegee

There are some golden rules to follow in using the epoxy system, namely: Keep the temperature above 10°C and the humidity low—no rain.  Measure the components exactly—preferably using the supplied pumps.  Mix the two components for at least one minute before applying.  Use a new mixing cup with every new batch.  Don't keep the volume of mixed material in the cup for longer than necessary—it gets hot.  Finally, use a good plastic squeegee or short-haired brush to apply the resin onto the cloth.

Go!  I started in the middle of the hull and worked towards the stern and bow with each new batch of resin.  Pour the cup over an appropriate area and work the squeegee and brush to wet-out the cloth.  It turns from white to clear transparent when it is correct.  Do this in small areas, making sure you don't leave an island of dry cloth or leave an excess of resin to form a teardrop.

I used 20 pumps of resin for the complete hull with the appropriate amount of hardener.  The next phase is to ensure that the cloth does not float on a bed of resin but adheres to the wood beneath.  The best way is to use the squeegee to move the excess away from the area.  Catch this excess from the squeegee in a cup with a slit in the side as you brush off the excess.  If you press too hard, the cloth turns white, so be careful and never reuse the excess resin because it is full of bubbles.  In this case, work from keelson down the sides of the kayak.  You will start to see the grain of the wood and also the texture of the cloth.  Do not leave too much resin at this critical stage.

Wetting out underway

This is the critical environmental stage of the chemical process.  Unlike polyester resin where the styrene evaporates, the epoxy is a pure chemical process.  Applying heat will only make the resin more viscous and may increase the set time a little if the resin is concentrated.

With the space heater going full bore, I was able to keep the temperature around 20°C and the humidity low.  Now, wait for the process to occur.

After about 2 hours, you test the surface to see if it is ready for the first fill coat.  The resin should be touch dry, and if one applies a ball of cotton wool, the strands will just stick to the surface.  OK, we can start the next step.

The fill coat is a coat of clear epoxy resin used to fill in the texture of the cloth to give it a smooth surface for the final product.  There are many ways to apply the fill coat—from brush and squeegee to a paint roller. Depending on the application, area, and how many coats you want, you choose the correct tool.  In my case, I wanted to get a number of thin coats of resin so that they adhered to the layer below and the thickness was uniform across all sections. It had the consequence that I could only apply one coat every two or so hours and needed to keep the carport around 20°C, knowing that the outside temperature would start to drop significantly at about 4:00 in the afternoon.

I mixed the resin and hardener in a new cup every time and then transferred it to the paint tray and continued to use the same roller until the total hull was coated.  This works well.  I started to mix the resin for the obligatory one minute and noticed that I was introducing air bubbles to the mixture.  Tipping it into the tray and using it immediately transferred the bubbles onto the kayak surface—not good.

First fill coat

To ensure all bubbles were removed, I used my best long-haired paint brush to tip the still-wet surface free of bubbles and to ensure it was level.  This takes skill and practice to get it right but is essential.  As stated above, heat increases the viscosity of the resin, so I got out the heat gun and moved over the surface of the kayak with gun in one hand and brush in the other to smooth the surface and for any trapped air bubbles to come to the surface.  One can apply quite a lot of heat to a spot without any detrimental effect, except the resin runs.

I applied three fill coats after the wet-out and in most areas obtained a smooth surface with no cloth texture showing.  I was limited by the outside temperature, or I would have applied a fifth coat on the sides to completely fill the cloth.  That can come later.

The heater ran for two hours after the last roller and brush stroke.

The next morning, I started the heater soon after dawn and ran it for three hours, but it was not necessary as the resin was hard and smooth all over the kayak.  This day had a very poor temperature forecast, so I decided to wait a day and start the deck the next day, which had an improved temperature range.

The deck, which I had set up on a second strongback, went according to plan.  Its surface area is less than the hull, and therefore I used less resin—34 pumps to 43 pumps, excluding hardener, which is in a ratio of 1:3 (105:207).

Hull and deck epoxy with fill coats

The weather cooperated and the space heater assisted, and everything went to plan.  It dried during the night to a smooth surface with only a few imperfections such as dust and small bubbles.  Those will sand out after I clean and epoxy the insides of the kayak.  This stage is full of dust and is not enjoyable.

Final Strip and Parting

The recommended approach to building a kayak is to start with the lower hull and complete that first.  The advantage of this method is that you'll build your skill level, iron out any difficulties, and see how the process works.  Having learnt from your mistakes—or rather, having built some experience—you can then move on to the deck of the kayak.  That's the area you'll view all the time, so naturally, you want it to be perfect.

In my case, this was a very wise move.  Not only did I reject the use of cove and bead strips, but I also perfected the sequence of adding strips so I could add more strips in a day.

Turning the Kayak

To turn a kayak with an internal strongback, one has to remember to knock the hot glue spots away from the forms and strips before you start to cover the deck.  At some point, you will have created a complete shell and you need to remove the strongback and the forms.  The first strip on the deck after turning the kayak to start the deck is not glued to the hull strip, and therefore when you have finished the deck, you can part the two pieces and remove the internal structure.

On the Micro Bootlegger Solo, the inner stem and stern are, during the build process, still in one piece, and the strips are glued to this piece as they terminate at each end.  So to part the kayak, you knock the forms away from the strips on the hull and, using the thinnest blade saw, cut the inner stem and stern into two pieces—hull and deck.

Modifying the Design

Having loosened the forms, they have to be returned to their correct locations and made rigid to take the deck strips in the correct shape.  I had decided early on in the build process that I didn't like Nick Schade's design with the very hard chines between the side deck and the curve of the aft and fore deck, so I had rounded the forms into a shape I thought looked more natural and smooth.

With the section around the cockpit especially—as I had also decided to markedly reduce the size of the solo cockpit—the modifications were compounded, and the natural flow of the foredeck meeting the cockpit side did require some ongoing building of the forms to take the strips.  This is very noticeable along the aft deck.  I had also decided that the aft deck, while having round sides, would look good being quite flat.  It's a feature of this design and has some advantages I'll reveal later in the build.

The Aft Deck Challenge

The aft deck didn't quite go according to plan because as I tried to get the strips to conform to the increased curve from side to deck with it being flat, the side strips started to part from the forms.  I had to use a strap around the whole kayak with wedges to get them back into shape and add some hot glue blobs to keep them together.  A further cause of this issue was that the tape I had used to attach to the forms started to come away from the form along with the hot glue drops.  This wouldn't have occurred if I had used staples.

The result came out OK, but it had me worried for a few hours. I  overcame the rounded chines and then set about filling the flat deck between them—from the central Marbo dark highlight strip out to the side deck.  As you progress outwards parallel to the central strip, the added strips have a more acute angle towards the stern. Finally, you're adding short, narrow-ended strips until you've covered the aft deck right up to the back end of the cockpit.

Take a break and review the process.

The Foredeck

The final stretch of the strip build process is the foredeck.  A beautiful feature of this design is the straight up-and-down bow, the big bold fore section of the kayak, and the round shape of the deck as it expands from the sharp bow out and up to the cockpit. It has all the attributes of a surf ski or seagoing surf kayak but with a sit-in cockpit.

With the high side of the hull completed—these strips extend from bow to stern—it was only a question of stripping in the foredeck.  I had selected a few planks with interesting grain and stripped them, setting them aside for the foredeck.  Again, the ends of the strips, which are set parallel to the highlight strip down the middle, get shorter and sharper as you fill the space.

With every strip you select, you match it to its place, lay it in position, then mark the cut to fit the sharp end.  I use a Fein vibrating saw with a circular blade and very fine teeth.  Having marked the strip, I cut it.  If I concentrate and have a steady hand, I can almost cut a perfect fit for the end of the strip.  It's only a case of a few strokes with the small hand plane or 80-grit sandpaper and the strip fits.  Remember, near enough is not good enough.  So test, test, and then retest until the strip fits all along its entire length.  Apply glue to the correct side and then tap the strip into place after a quick application of hot glue in the correct places on the forms.  Use masking tape to hold against the previous strip and clamps to ensure they stay down and alongside.

I initially tried to use a wooden wedge between the new strip and the outer side strip and found, to my dismay, that a strip end—while dry-fitted perfectly—had gaps at the end when glue was applied.  Only after two attempts did I realise my error: without the wedge, the gap between strip and deck was normal, but with a wedge, it pushed the deck strip away from the centre line and increased the gap of the previously fitted sharp-end strip. Silly me.

The Final Whisky Strip

I finally came to fit the final strip in the kayak—a short strip on the starboard foredeck.  Measured, fitted, tested, retested, dry-fitted, glued, and finally fitted the last strip.

At this point, the shipwrights of old, mostly from North America, would celebrate with a nip of their local brew.  But having many ancestors born and raised in Scotland, I went to the cupboard and got out an Edinburgh Crystal Thistle Whisky Glass Tumbler and toasted the final strip planked on my kayak.

Parting the Hull and Deck

Now came the parting of the two pieces to epoxy the hull and deck and to remove the strongback and work on the interior.

I cut the bow and stern inner pieces and used soft, wide wood wedges to drive the two-part strips apart and separate the hull from the deck.  It started to come away from the hull where I had previously separated the forms from the strips, but the end pieces remained stuck.  A few more wedges and a gentle lift of the bow, and the two pieces came away in my hands.  Success.

I turned the deck over on a set of trestles and removed the form distance separators, then firmly tapped the forms away from the end towards a wider part of the kayak.  Thankfully, the forms came away and I was able to lift the forms and strongback out of the kayak.

In parting the hull, a few strips sprang where the glue had taken to the forms and not been cleanly released.  It was a quick and easy task to apply glue to the gap, push the strip back into place, and apply some masking tape—or in one case, a 10kg piece of lead—to keep it down and in place.

Preparing for the Next Phase

I had kept the excess length of square aluminium tube I'd secured for the strongback and used it to make a second strongback.  I used every second form on the hull section and created two strongbacks for hull and deck.  The kayak now rests on the forms and hopefully won't lose its shape during the final sanding and application of glass cloth and epoxy fibreglass.

I am in Canberra, Australia, where we are entering winter—officially on 1st June—and we have during our winter many nights falling below freezing, but then the day temperature rises to about 15 to 18 degrees C (65°F).

The question now is: will I have a day temperatures long enough to apply the epoxy, and how long will I have to wait for the temperature to rise?