Bonding your Kayak: The Magic of Methyl Methacrylate
When bonding your kayak we use Methyl Methacrylate Adhesive (MMA) for several steps of our building process. We use one type to tack in our foot brace studs, another to bond in our seats and coaming, and a third to bond the deck and hull together. One of the reasons we have chosen to use MMA is its strength. When we bond two parts together with MMA, it will take 3,000 pounds for every square inch of bonded area to pull them apart again. In most instances, this means the bonded area is stronger than the surrounding laminate.
Installing the Coaming
One of the first things we bond into the kayak is the coaming. We use jigs and spacers to fit the coaming into the deck. Once it is clamped in place, we add MMA between the deck and coaming. We then add trim to the inside of the coaming so that the edge is covered. Finally, we add more MMA to fill any gaps and smooth the joint with a seal spoon.
For the next step, we bond the seat to the underside of the deck. We do this in a couple of steps because the MMA cures exothermically. We fill a lot of space around the seat so there are no gaps. If we use too much MMA at once, it gets very hot and it can cause problems. By bonding the seat in small increments, we can better control the temperature as it cures.
Putting it all Together
After the seat and coaming are installed, we sand the inside of the deck. We also seal the backside of the fittings and hatches. Once that is done, we are ready to bond the deck to the hull.
We add seal to the tops of the bulkheads and a bead of MMA around the flange on the hull. One of us then brings the deck over and slowly lowers it onto the hull while the other uses an alignment tool to guide the deck into place. We then clamp the deck flange to the hull flange. Once the MMA has cured, we are ready to begin our finishing work. At this point it is technically a kayak, but it is rough. It doesn’t look good yet. In our next post I will talk about the finishing process and the detail work we do with every kayak we make.