Thursday, March 30, 2017

Shaping the Argie 15 Foils

I said in my previous Argie 15 blog post that Kevin Agee laminated the blanks for the foils from strips of cedar and poplar. Aside from making very attractive foils, it also has the benefit that they can be made from relatively inexpensive wood that can be bought at your local hardware store. Cedar that is available from Lowes or Home Depot is generally of inferior standard that may not be suitable for foils. Laminating strips of timber of differing characteristics can use the one to strengthen the other, at the same time serving a decorative function.
Daggerboard blank, cut to outline shape and sanded smooth, ready for shaping.
I won't go deeply into the shaping process for the foils, I will do that in a separate post on my Boatbuilders Tips blog. That should be posted in the next few weeks. For this post I will show only the basics.

The daggerboard is shaped to an airfoil section below the hull and rectangular where it is inside the daggerboard slot. Similarly, the rudder blade is foil-shaped in the water and rectangular where it is inside the rudder stock. I did this shaping with a hand plane, a belt sander, a Japanese Shinto rasp and hand-sanding with a sanding block.
The shaped daggerboard, foil section over most of its length, rectangular in the hull.
Note all the sanding dust on the floor, which must all be vacuumed up before any glassing starts.
The shaped rudder blade. Holes are for pivot bolt and up- and down-haul lines.
The next stage was to sheathe them in fiberglass fabric, in epoxy resin. The rudder is small enough to clamp in a vice, leading edge upward, then to drape the epoxy-saturated glass fabric over both sides of the blade at the same time. This I did by wetting out the glass with epoxy on a flat sheet of plastic, then moving it to the rudder, which was firmly clamped in the vice fitted with soft jaws. The top of the rudder is in the vice, so can't be glassed at the same time and must be glassed as a separate operation later.
Glass fabric draped over rudder to glass both sides at the same time, meeting at the trailing edge.
The daggerboard is a lot larger then the rudder, so maneuvering a piece of glass fabric large enough to cover both sides and weighed down with epoxy would be very awkward, so I chose to glass that one side at a time. I laid the board on a sheet of plastic to protect my workbench from droplets of epoxy. Doing one side at a time allowed me to lay the dry glass over the whole of one side of the board, wetting it out with epoxy in place. I supported the glass that was projecting past the trailing edge with a spacer under the plastic sheet, to stop the glass from drooping, which would mess up the clean trailing edge that is needed.
First side of the daggerboard glassed.
Some of the edges of the rudder and daggerboard don't have glass covering them after this, so they are covered with glass tape to complete the covering. There is also a lot of sanding going on between these steps, to feather edges of glass fabrics and tapes and to generally make smooth surfaces.
Glass-taping the leading edge and bottom  of the daggerboard. This batch of epoxy went off faster than I expected due to warmer air temperature, so the glass is a bit rough in places, needing more sanding.
I added another two coats of epoxy over all the surfaces, with more sanding between coats and after the final one. As a last step on the rudder blade I blanked off one side of all holes with painters tape then filled those holes with epoxy. I let it stand for about 15 minutes for the epoxy to soak into the timber, then removed the tape to allow the excess to drain out. This step is to prevent (or at least minimise) the absorption of water into the wood.
Daggerboard and rudder after 3 coats of epoxy, before final sanding.
The daggerboard still needs a handle, so I cut this from a poplar plank, in two matching pieces. I glued these to the faces of the board along the top edge.
Shaped timber handle pieces glued to both sides of the daggerboard. The board has been sanded to ready it for finishing with varnish.
I have now sanded and epoxy-coated the handle and the foils are nearly ready for varnish as the final finish.

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