Practical, hands-on notes on filling plank seams with MAS FLAG and Workshop Mix — the technique we use, and the mistakes worth avoiding.
Preparing the seam
When filling seams with epoxy, get sandpaper right into the seam first — you want the wood as clean and dry as it can possibly be. Spend real time on this prep work; have everything to hand, and take your time.
Don't be too greedy about how much you take on in one session. If you've got a whole boat to do, work it in small sections spread across the hull — a seam on the port side by the gunwale, then the same seam to starboard, then three planks further up. This spreads the strength through the hull evenly as you go, so if you lean on it, or a friend comes in and pokes and pulls at it, there's already enough strength in place that it won't go out of shape.
Stopping the epoxy falling through
Once the area is clean and clear, I use one of a few methods to stop epoxy running straight through and out of the seam:
- Good old masking tape
- Plastic
- A few prayers and a steady hand
Watch the first part of the prep.
For most people it's easier to work from the outside in, since the seam is bigger on the outside due to the natural curve of the hull — though you can work either way. It's worth remembering it's easier to sand and clean up the outside of a hull than the inside.
Watch the second part of the prep.
When I use plastic, I usually use a pillow inside a black rubbish bag as padding, since it takes up the shape of the hull well. It's a personal choice, and depends on how much work you're planning to do in one session.
Watch the technique in action.
Mixing and applying the epoxy
I tend to use MAS FLAG with medium hardener for this — it stays creamy and holds in place. I find some other epoxies get too hot, don't give you enough time to work, and can cause chemical burns on the skin.
Workshop Mix is one of our own products, and I like it for a number of reasons: it's easy to mix, it retains MAS epoxy's good stretch and workability, and it doesn't smell. When mixing the powders in, make sure you don't lose the shine on the mix, or it'll end up too dry and brittle.
A simple trick using freezer bags.
When filling a bag, open it up and stand it in a jug or similar container first — it makes filling much easier. You'll normally get three or four fills from one bag before you need to throw it away.
Make the hole a lot smaller than you think you need. It lets you apply real pressure and squirt the mix into the back of nooks and crannies — you can always make the hole bigger later, but you can't make it smaller.
Take your time
Then it's simply a matter of giving yourself time. Good luck — and if you need help, just ask.
