: I am building a stitch and glue kayak for the first time. I do not
: understand the how to make or use a fillet. As a begginer any simple
: advice will help. Espesualy good places to buy supplies. Thanks

When you join two thin pieces of plywood, edge to edge. You don't get a very big area to glue. This problem is solved by creating a large area of reinforcement at the seam. This reinforcement is usually sandwich of narrow strips of fiberglass cloth on the outside and inside, which surround the joint, and keep the pieces of plywood connected. The thin strips of glass cloth can either be cut from a sheet of glass cloth, or they can be woven to that size.

When the material is woven to size it is called glass tape. The term "tape" can be confusing as there are some tapes which have adhesives on them. This stuff does not.

When the strips are cut from yard-goods they can be cut in three directions: Straight across the width of the cloth, In line with the length of the cloth, or at an angle (usually close to 45 degrees) across the width of the cloth. this last method of cutting is called a "bias" cut.

The first two methods result in the woven threads of glass fibers running straight down the length of the strip. This provides very good strength in that direction. The bias cut fabric, however, consists of relatively short strands of glass fibers that are at an angle. when you use bias cut strips it is easy to give a gentle pull to the strip and force it to curve, and thus follow the curves of the boat seams very neatly.

Puttign ther glass fabric strips over the outer edges of the boat is relatively simple. It just folds over the edge. Getting the galss fabric to follow the inside of the seam is a bit more challenging. The sharp angle at which the two pieces of plywood come together is a difficult place to force the fabric into.

To make things easier, we fill in that joint and produce an area with a wide, gently rounded surface which allows a smooth transition of the glass fabric from one side of the seam to the other. This we call a fillet. ( Think "Fill It" as in fill up the seam)

The material we use for filling the seam is made of plastic resin (usually epoxy or polyester plastics) which are spread onto the seam.

Since the plastic resins are very watery, and would otherwise run out through the gaps in the seams, a variety of materials are mixed in to these resins to make them much thicker and less likely to flow away before they harden.

These same resins are used (without thickening) over the glass cloth to adhere it and strengthen it, so you just buy the one resin mix, and then add your own additions to make tha material for the fillets.

the options for thickeners are many. There are commercially sold materials which include glass globes that are the size of grains of table salt (microspheres), expanded silica (cab-o-sil), finely ground or chopped glass fibers, (scraps from the woven fiberglass cloth) and then there are the home-made thickeners like fine sawdust (dust from a sander is finer than dust from a tablesaw), chopped cellulose from cotton, playground sand (hard to later machine) and common baking flour. There are lots of other options, too.

The material for the fillet is mixed to a thick consistency and spread neatly over the inside of the seams, providing a continuous leakproof filler for the joint, and giving a gluing area well over an inch wide at each seam. The fillet is smoothed and shaped into curved surface joining the plywood pieces.

The initial temptation is to stick your finger on the goo and just run your finger down the length of the joint to smooth it out. Resist this temptation. You don't want your hands all gooey. Instead use a tool cut from a piece of polyethylene plastic ( the hardened resin won't stick to polyethylene) You can cut such a tool from the side of a plastic bottle. Cut a piece about the size of an index card and make one of the corners a wide, rounded corner. Use a bit of fine dandpaper to smooth the rough edge where you have cut, and you are in business.

Depending on the method and instructions you use, this seam filler (or fillet) may be allowed to harden before the glass cloth strip is applied over it, or you may go to putting on that glass cloth strip while the fillet materials are still soft and tacky. Which ever way you work, when the plastic resin hardens it becomes a long plastic strip that runs the length of the boat providing the strength of a wood frame member, and a continuous watertight seal over the length of the seam.

Hope this helps

PGJ