Thursday, April 13, 2017

Argie 15 - Fitting the Daggerboard Casing & Rub-Rails

Moving on with the Argie 15 project, I covered the bottom runners in my previous post. The runners serve multiple purposes, which I forgot to explain. The runners give some protection to the bottom when beaching the boat, by lifting it a bit when pulled onto rough beaches. They strengthen the bottom by serving as stringers but, being on the outside of the boat, they keep the bottom of the cockpit clean for a more comfortable sleeping space when camp-cruising. They also help to improve the efficiency of the planing surface by channeling the water parallel to centreline rather than losing energy by moving off to each side.

At this stage we also checked the fit of the daggerboard. It slid nicely through the slot in the hull. Kevin had glued the end spacers to the one side of the daggerboard casing but the second side was still loose. When we checked the fit, the board wouldn't go through. Checking the sides for straightness showed that they bowed inwards a few millimeters, enough to jam the board. That gave warning that care had to be taken when gluing it all together to ensure that the sides remained straight throughout the height of the casing.
The daggerboard casing glued up, including the top and bottom framing. The blue pieces at the top are spacers to force the sides against the framing, to ensure that there is no curvature in the surfaces to reduce the width and jam the board.
The casing glued in place. The blue spacers were left in place until the glue had cured, so that there would be no chance of the casing distorting and reducing the width of the slot.
Next on the "to do" list is the rub-rails. These are laminated to the outside of the hull, at the gunwales. They stiffen the hull, changing a fairly flexible plywood edge into a robust gunwale that is capable of taking a knock if needed. Some builders of the Argie 15 don't use this detail from our drawings, instead changing it to an internal scuppered inwale detail. That is a very pretty detail that is well-suited to traditional rowing boats and similar craft, adding the benefit of tie-off points anywhere that you want along the gunwales but is more difficult to do. For the Argie 15, which will be sailed with the crew sitting along the sides of the cockpit, the inwale creates an uncomfortable surface to lean against instead of the clean surface of the original design.

Kevin called on me to assist with fitting the rub-rails. The laminations are fitted in single lengths (scarphed from short pieces), so are awkward for one person to handle in a confined space. Getting them correctly positioned on the wet glue while also working with clamps calls for some ingenuity if working by yourself. It is simpler to call in a pair of extra hands.

This job calls for lots and lots of clamps. We did both sides in one evening, which needed all of Kevin's clamps as well as all of mine. If you are brave and short of time then you might want to laminate all layers at the same time. This is risky because it needs slow-setting glue that won't set before you are able to wet-out all strips, get them into place, manipulate three or fours slippery lengths into proper alignment and get all the clamps in place and correctly tensioned.

We chose instead to do one layer at a time. Rather than four layers of equal thickness, Kevin prepared inner and outer layers of poplar and a middle layer of cedar of double-thickness. This gives a nice stiff gunwale with a tougher outer surface than if all layers were cedar. It is also very pretty.
Kevin with the Argie 15 after clamping the first layer of the gunwale.
Two days later we also glued the second layer of the rub-rail. We managed to break one of the scarphs even before starting with the gluing. The epoxy was not fully cured yet so the epoxy was well short of final strength. We were able to still laminate it onto the  first layer by carefully clamping at the joint to hold it closed against the bending loads applied by the curvature to which it had to comply.

When gluing all laminations after the first one, it is best to get the bottom completely flush and let the top look after itself. The reason is that it is very easy to clean up and neatly finish the top  but much more difficult to do the same to the bottom of the rail because of the adjacent plywood.

That's all for now. To see more of this and our other designs, go to our main website or our mobile website.

Monday, April 3, 2017

Finishing the Bottom of the Argie 15

My last post was about making the rudder and daggerboards for the Argie 15. While I was doing that work, Kevin Agee was making good progress on the bottom. He has glassed all of the outside seams, sanded, filled and faired them so that the chines are smooth and fair curves, cut the daggerboard slot and installed the bottom runners and skeg.

This work all needs to be nicely done because the hard chine edges are what defines a hull like this. Unfair and wavy edges with lumps and bumps catch the eye very quickly and also cast odd shadow lines, spoiling the overall look of the finished boat. It is worthwhile taking this work slowly and being very happy with your own work before moving on to the next step.
The tapes have been sanded smooth and the tape edges have been feathered. 

If this boat was to be clear-finished then sanding and feathering the tape edges is about as far as fairing can go before final epoxy coats and varnish are applied. Our boat will be painted, so fairing can be more conventional and more extensive. This photo shows epoxy fairing compound  that has been applied then sanded down to fair it into the surface, making it completely disappear.
A closer view of a chine after fairing. It fills the slight hollow alongside the tape because of the two thicknesses of glass sitting on the surface of the plywood.
Runners glued to bottom. They are being held by temporary screws, assisted by a ratchet strap at the bow.
A sliding bar clamp in the daggerboard slot helps to keep the end of the centre runner in contact while the glue cures.
Sliding bar clamps secure the aft ends of the runners and skeg at the transom. The runners will be trimmed off flush.
Junction of the centre runner with the skeg.
The final coat of epoxy resin before turning the hull back upright for deck finishing.
The next post will likely be about laminating the rubbing strakes to the gunwales and other finishing work on the decks and transom.

To see more of this and our other designs, go to our main website or our mobile website.

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.

To see more of this and our other designs, go to our main website or our mobile website.