Sunday, October 30, 2011

Test Fitting the Cockpit

After finishing the forward decks, I completed the basic assembly of the cockpit box and temporarily fitted some stringers on the ends so I could hang it from the beams and check the alignment and fit of everything.

This is just the basic center section of the cockpit, built to plans with a foam-sandwich floor.  This floor is lightweight and incredibly stiff, with no signs of flexing when walked on.  Hanging it in place allowed me to scribe an accurate line on the inboard sides of the cabins, for the placement of the rails that will support the outboard edges of the seats.  There is clearance on either side of the 4-foot wide cockpit box to accommodate a 12-inch wide under seat storage box on each side.  These will be dry storage areas closed by the hinged seats, and will provide a place for the batteries and other essential gear. 

The extra-long-shaft Nissan outboard sits high and dry in the cockpit well, where it will be well-protected and easily accessible.

The 25-inch shaft length makes it possible to mount it this high and still have the prop deep enough to minimize cavitation in choppy conditions.  You can see here that it will be well under water, yet not deep enough to strike the bottom before the hulls do:

After making sure this fit was good, I then cut out the opening in the aft end of the cockpit that allows the motor to be tilted clear of the water when it is not needed, which hopefully, will be most of the time.

Now the cockpit is back in the shed on saw horses for all the finish work on the fillets and glassing, as well as construction of the seat boxes.  Like every other part of this project, the assembly of the parts is a small percentage of the real work that has to be done before the parts are finished and painted. 

Monday, October 24, 2011

Building the Forward Decks

It's been awhile since my last post here, and a lot has happened in the meantime.  Most significantly, I lost my father two months ago and have been adapting to life without him - a man who was truly my greatest teacher and certainly one of my best friends.  I was fortunate to have lots of time with him right up through his last years, but being so close makes losing him harder still.
Besides that life-changing event, I've had a new book released this month, and I'm right in the middle of writing the next one and about to sign a contract for the one after that.  The current project I'm working on is a novel, and it will prominently feature a Wharram catamaran in the story line.  More on that later.  I've also been working on the Tiki 26 parts mentioned in my last post that I contracted to build for another owner.  These are coming along nicely and the remaining work to be done on the beams, rudders and mast is mainly fiberglassing and fairing.  I'll post some photos of that project soon as well, but for now I wanted to focus on the slatted forward deck, as I have been asked how I was going to build it

Working with the cypress and assembling the decks has been a pleasant job over the last few days, as it has involved little epoxy work and no fiberglassing or fairing.  I've documented the process with photos that show the various stages of construction from layout and design to trimming and sanding. 

First, I laminated four athwart-ship deckbeams from the the same cypress stock the planking was milled from.  The deck beams consist of two 2 1/2-inch by 1-inch thick planks laminated together to form 2 1/2-inch by 2-inch beams set on edge.  These four beams are not strong enough alone to support the deck, since the span is as wide as 8 feet between the hulls at the forward end of the deck.  To prevent them from sagging or breaking in the middle, I also made two fore-and-aft beams of the same dimensions, lag-bolted to the bottoms of the four main beams and hung from under the forward and main crossbeams by lashing cleats.  Here you can see the rough framework clamped into place for alignment and measurement, the two fore-and-aft beams are the middle two.  The extra two near the hulls on each side are temporary for alignment only. 

Next, I made and installed cleats of 18-mm plywood to support the fore-and-aft beams - two on the aft side of the forward crossbeam, and two on the fairing side of the mast beam.  Now that the location of these has been determined, I can glass-sheath the cleats, and finish fairing and painting these two beams. 

After temporarily securing the beams to the cleats so the structure would support my weight, I began working out the plank widths and spacing.  I wanted most of the planks to be 2 1/2-inches wide, as planking much wider than that is subject to cupping, warping or splitting as it cycles through extremes of wet and dry and hot and cold.  After deciding on a gap of 3/4-inch between all planks, I then made the port and starboard margin planks and two middle planks that are in line with the lashing cleats.  The forward ends of the margin planks, of course, have to be quite a bit wider than the standard 2 1/2-inch plank width, as the outer edge is cut to follow the curvature of the hull as it tapers into the bow. 

Once these four planks were secured to the beams with counter-sunk screws, the entire structure was then rigid enough to remove without getting it out of square.  Here you can see it upside-down on the sawhorses.  The longitudinal beams have been shaped and rounded over with the router on the bottom.  The clamps you can see on the ends of the deck beams are for gluing on fitted spacers under the ends of each beam where it rests on the toe rail.  Each spacer is different because of the curvature of the sheer line.  The idea is to distribute the weight evenly across all eight contact points and four beam lashing points.  The result is a very rigid deck that shows no sign of flexing when I jump up and down on it.  I was trying to achieve this with the minimum amount of framing, in order to save as much weigh as possible.

With the finished framework back in position, I then cut and installed all the remaining planking, using spacers made of little blocks of 3/4-inch plywood to maintain a consistent gap.  This spacing is close enough to keep most items on board, but wide enough to allow water to quickly drain off in rough conditions.

The finished planking, with two counter-sunk screws per plank to beam joint, for a total of 8 screws per plank.  Now I had to make 210 cypress plugs to fill all those screw holes.

This went fairly quickly with a 1/2-inch plug cutter chucked in a drill.  I had plenty of scrap cypress to get them out of.

Here, the plugs are all in, dipped in epoxy and tapped in tightly with a hammer:

After the epoxy cured, I cut them flush with a sharp chisel and then did a quick, preliminary sanding to see how it was going to look.  More detailed sanding will be done later.  I think this deck is going to greatly enhance the livability of the Tiki 26 by providing a secure working area to handle ground tackle and sails and more uncluttered deck space at anchor.  There is a weight penalty as opposed to a trampoline, but it's not that significant because of where it's located, as most Tikis need some weight forward of the cockpit to trim out properly. 

Here's some different perspectives of the deck:

Note that with this design, the deck beams are carried nearly as high as the bottoms of the main crossbeams.  The only parts lower are the two fore-and-aft beams.  This will minimize taking wave tops off with the deck beams, though I'm sure that beating into rough seas will be wet.  But it would be wet with a trampoline too.