Sunday, December 11, 2016

Argie 15 Hull Glued together

The stitch-&-glue boatbuilding method is also known as stitch-&-tape. Our Argie 15 build being done by Kevin Agee has now reached that stage where both of these names can be seen in the process.

The hull skin has been stitched together with electrical ties, with a few copper wire ties at high-load points where the electrical ties are not strong enough to hold the panels close together. In the photo below, the bulkheads have been secured in their correct positions, changing the floppy panels into a hull shell of the proper shape. At this stage it is still somewhat flexible and can still be adjusted to remove any twist that may have occurred when tying the panels together. Get behind the boat and sight over the top of the transom, lining up the tops of the bulkheads with the top of the transom in your sight-line. Any twist will be obvious and must be pulled out before starting on the gluing process. You can see the ties holding the joints together.
The next step is to glue the outside joints of the panels between the ties. For this boat we are using MAS Epoxy products throughout and the glue that we are using is MAS Gluzilla in the 185ml cartridges, applied with a standard caulking gun. The glue comes out pre-mixed from the mixing nozzle and can be applied directly into the V-shaped joints between the panels, filling the joints flush between the ties. In the photo below the ties have been left in place to hold the joints until the epoxy has cured. Epoxy can stretch for days after it has hardened, so don't be in a rush to pull the ties out.

While the epoxy in the joints is curing you can glue the bulkheads in place. This is done with epoxy fillets, which we have chosen to also do with the MAS Gluzilla. It is applied in a large bead on each side along the perimeter of each bulkhead against the hull. They are finished smooth to a cove-shape using a tongue depressor or similar tool. In the photo below, there are two semi-circular cutouts in the bottom edge of the aft bulkhead of the middle seat. There is a matching pair in the forward bulkhead of that seat. These are to take PVC half-pipe drains that bring water from the forward compartment of the cockpit into the aft area where crew can bail it more easily or it can be drained through dinghy self-bailers.
 Next step is to pull out the ties and fibreglass the insides of the joints. The epoxy glue on the outside will hold the joint while the inside of the joint is taped. All of the seams must be taped, taking care to finish neatly against the bulkheads. When the epoxy has set and started to cure you can feather the edges with a small block plane with a very sharp blade set fine. If the epoxy has already cured then it may be better to feather the edges with a small finishing sander.
Close-up of taped seam before feathering the edges
Taped seams in the bow. The centreline seam has first been epoxy-filleted to form a good surface to receive the glass tape.
In areas where the taped seams won't be seen, like inside the seats, they don't have to be feathered but must be sanded smooth and the weave filled with epoxy to give a smooth surface. If you don't do this then there will be rough surfaces and jagged edges that will rip your knuckles when cleaning those places in the completed boat.

When that has all been done, lightly sand all of the internal surfaces of the boat and remove all dust, then apply three coats of low viscosity epoxy. The first coat will soak into the wood to create a good bond. By the third coat you should have a full coating of epoxy that can be sanded smooth to prepare for paint. Try not to leave more than 12 hours between epoxy coats, so that they can bond chemically to each other. If more than 12 hours has passed then lightly sand the epoxy before applying the next coat.
Three coats of epoxy on all inside surfaces.
To see more of this and our other designs, go to our main website, mobile website and Flickr photo albums.