Wednesday, March 28, 2007

Sanding... drudgery or sculpture?

Warmer weather and sunny days bring forth promises of spring here in the northeast. This encourages me while I undertake the less than glamorous task of sanding the interior of the hull again, and again, and again. Actually, I have become one of those rather odd individuals who enjoys sanding. Using the proper equipment and supplies for the job makes all the difference between drudgery and creating a work of art. The first order of business is to equip yourself for safety with a good respirator, ear plugs, and latex or nitrile gloves. The fine epoxy dust is an irritant at best, and potentially hazardous. I also found that leaning the hull against a wall while on the saw horses made the task much more pleasant in terms of avoiding lower back pain from bending over for long periods of time.

I use a number of different sanders and methods depending on what I am working on. I begin with the 5" random orbital sander on the flat areas, and then a 'mouse' detail sander to get into the corners and narrow spots. For the inside curves of the fillets, I wrap sandpaper around a sponge sanding block, and I also use a rubber hand sanding block in a number of situations. When I finished on one side of the hull, I moved it over and leaned it up against the other side so that I did not have to work upside down at all.

The CLC Jimmy Skiff ™ plans call for adding a block of solid wood to the inside of the transom as a support for the rudder attachment. I decided to combine this with the addition of a rail to span the top edge of the transom for even more support. I liked the look of how it continues the line of the inwale around the aft end of the hull. It also gives the added advantage of providing hand holds to lift the stern. I cut this out of a solid oak plank on my bandsaw, leaving the top edge proud of the line, to be sanded down to the transom edge after the epoxy cured. This shaping was done with a belt sander, and then the edge rounded over with the hand sanding block.

Here is the interior transom view after the shaping, sanding and another coat of epoxy. I am planning to finish the oak with varnish, and paint the interior walls and floor with a light solid color marine paint. Clicking on this or any of the photos will provide a better look. Just use your browser's 'Back' button to return to this page after viewing the photo, unless you are using tabbed browsing in Firefox or IE7, in which case you can click between the tabs that open. Next I'll complete the mast and boom, fit the mast step and add the rub rails. It's feeling more like sailing weather and everything seems to be coming together nicely. Life is good.

Sunday, March 11, 2007

Compound curve lamination, mast step and rudder

In my previous post, I mentioned a couple of small cosmetic customizations to the design of the Jimmy Skiff ™ I am building. The most visible result of my 'straying' from the published plans is shown in this entry. I thought that with all of the nicely curved lines on this boat, the splash rail/deck support beam would look better if it curved in a way that would compliment the curve of the aft seat. Since the deck has camber which is determined by the shape of the top of the forward bulkhead, the deck rail curves to follow the profile of the deck. The CLC plans show the deck rail with this curve, but as straight across from sheer to sheer. I decided that I wanted the aft edge of the deck to have a compound curve as shown in the photos on this page.

I knew that laminating the deck rail in a compound curve would be challenging at best, and I don't mind saying that I went through more than one scrap wood 'prototype' before getting it right. In the end, the solution really turned out to be rather simple, yet elegant, much like the Jimmy Skiff ™ itself. Since wood of any thickness and width beyond a few millimeters is not favorable to bending in more than one direction at a time, I realized that the way to do this was to laminate thin strips of wood that were wide enough to allow cutting the shape of the second curvature from the laminated stock. I started by taking a length of 4"x4" Douglas Fir and marking it with the curve which matched the fore/aft curve in the deck, then I cut it in half on my band saw. This would be the laminating form. Then I sliced another section of the same straight-grained, knot free beam into six thicknesses of about 3mm each. These were glued together with a generous amount of silica thickened epoxy and wrapped in plastic wrap before getting clamped in the form.

After the lamination cured, I took the blank out of the form, sanded off the excess epoxy, and marked the curve of the deck camber on it. I did this by holding the blank up against the aft edge of the deck and running a pencil along the length of the rail with a 1¼" thick block riding along the top of the deck, under the pencil. Then I just traced the bottom of the deck from underneath to mark the bottom of the rail. Taking the lamination back to the band saw, I cut along the lines for the top and bottom of the deck rail. A little more shaping with the sander, and I had a perfect fit! The next challenge was to figure out a way to clamp the rail in place on the aft edge of the deck. I found that I could place half of the laminating form on top of the deck, and clamp it down to the sawhorse. Then I could clamp between the rail and this block. I also clamped the center of the rail to the deck where the mast hole was. Then I clamped both ends of the rail down to the inwales.

The plans specify the deck material as 6mm marine plywood, and when I was cutting all of the parts for the hull, I cut the deck out of the 6mm okoume with the shape shown in the plans. Later, when I decided that I wanted to extend the sides of the deck back a little to get the curve I wanted, I didn't have any 6mm ply left. I did have ½ sheet of 9mm okoume left, so that's what I used for the deck. Since 9mm plywood does not bend as easily as a 6mm panel over the bulkhead, I set my circular saw to cut several kerfs lengthwise on the bottom of the deck to make it easier to bend. Then to reinforce the deck, I filled the kerfs with wood flour thickened epoxy just prior to putting the deck in place and temporarily screwing it down. I made the mistake of removing the screws the next morning after I glued the deck on, because I thought the epoxy was sufficiently hardened. I went away for the weekend, and when I returned, the edges of the deck had begun to lift. By now, the epoxy had hardened, and there was no way to just screw it back down. I had to remove the hardened epoxy from between the deck and the inwales, using a handsaw and RotoZip ™ tool. Then I was able to re-pack the gap with a fresh mix of silica thickened epoxy and drive the screws back in. The screws will be removed when everything is fully cured, and the holes will be filled prior to sanding and painting the deck.

Here is a view of the deck that also shows the placement of the mast step. I decided not to install the mast step until I have the mast ready to test a trial fit. This will allow me to make sure that I have it placed correctly in relation to the hole that runs through the deck.

Here is a better look at the mast step. This will be sealed, sanded, and painted the same color as the floor.

These rails support the aft seat. They are glued in, and held with screws.

The aft seat is finally glued to the rails and then a fillet is formed around the perimeter, including under the front lip of the seat. This will make the space under the seat a sealed floatation chamber when the hatch plate is added. The toolbox and bench vise are there as weight to assist the clamp in holding the seat top down while the epoxy cures.

This is the rudder attachment. I made the rudder based on the templates and directions in the plans. The lower portion will flip up when beaching or in shallow water. The attachment is accomplished using a 12" bronze rod, fitted through stainless steel eye-bolts. I had read somewhere that the one thing that a particular Jimmy Skiff owner did not like about this arrangement was that it was noisy due to the 'play' between the rod and the eyes. I decided that I would attempt to solve this by buying oversize eye-bolts and filling the eyes with epoxy. Then I drilled a hole through the cured epoxy which the rod fit through without any play. This resulted in a very smooth and quiet steering mechanism. I still need to make the tiller and attach it to the top of the rudder.

Here is a better view of the rudder attachment hardware. If you click on the photo and look at the eye-bolts on the bottom, you can see the epoxy fill that I was talking about. You will also get a better look at the ring clip at the top of the rod, and the pin clip retainer at the bottom. With this set-up, I can be confident that the rod will not slip out, while it is still easy to remove the lower pin and pull the rod upwards to remove the rudder.

I welcome your comments or questions. If you click on the Comments link at the bottom of this page, you will be able to leave a message.

Thursday, March 1, 2007

Installing the 'furniture'

Jimmy Skiff interior during constuctionLast night was very productive in terms of the visible progress on the Jimmy Skiff ™ project. I find it interesting that most projects seem to have periods where the apparent progress is much faster than other times when the same level of effort is expended. I was having so much fun, I totally lost track of time, and only realized that it was almost 2:00 AM when I finally turned off the shop lights and headed into the house. All of the work I did in building parts last week is what made everything come together last night. These pictures show that I finally got the bulkheads, seats, and dagger-board trunk installed. Pay no attention to the epoxy and filler mess here-and-there. This will all be cleaned up (sanded) before applying paint or varnish.

Jimmy Skiff dagger-board TrunkI was pleased with how the dagger-board and trunk turned-out, and cutting the hole in the hull was not nearly as traumatic as I imagined it would be. I started by marking the location for the trunk, after making sure that I had it centered in the correct location. Then I used a 1" forstner drill bit to drill out either end of the slot I was preparing to cut in the hull. Then I used a Japanese style hand saw to cut the slot between the two holes. This Mini Dozuki Panel Saw is now one of my favorite tools, and especially so because it was a gift from my son last year.

Jimmy Skiff dagger-board Trunk with daggerThe dagger-board trunk is made by sandwiching a 1" wide hardwood spacer on either end, between the two 9mm okoume panels that were cut out using the template in the Chesapeake Light Craft plan set. Then I added the mahogany trunk logs, which are the strips along the bottom of the sides . Next was milling and fitting the trunk cap, which I made out of hard maple. I chose this wood because I thought the contrast would look good, I had it on-hand, and it will be very durable in a place that will likely take some 'hard' use. I cut the center slot out of the cap by drilling the ends of the slot with the 1" forstner bit, and then set the fence of my table saw to the distance between the outside of the cap and the edge of where the slot would be. Then I positioned the piece over the blade and cut from the hole on one end to the hole on the other end, flipped the board and repeated the cut on the other side of the slot. The trunk is attached to the hull by bedding it in silica-thickened epoxy and screwing in eight 1 ½" bronze screws, up through the bottom of the hull and into the trunk logs.

The dagger board is made by gluing two 9mm okoume panels together with thickened epoxy, and then the profile is cut out based on the template in the plans. The leading edge of the dagger-board is rounded over, and the trailing edge is tapered. I added the mahogany stop blocks on either side, up near the handle hole, using epoxy and bronze screws. I was also sure to round over everything to prevent any injuries by banging into any sharp edges or corners. The dagger board can easily be positioned anywhere along its length by using a small wedge at the top of the aft edge. I have also seen where some people use a bungee cord to apply a little directional pressure to hold the board in place. I suppose another alternative would be to drill a series of holes in the dagger-board and use a belaying pin to hold the board partially up.

After I attached the dagger-board trunk to the hull, the next phase was to attach the bulkheads and seats. In order to simplify making the smaller fillets for these attachment points, I used a caulking gun loaded with a West System's tube which I filled with the epoxy fillet mix. The empty tubes are sold in pairs, and using slow cure epoxy, I had time to mix it up, fill the tube, make most of the fillets, mix up another smaller batch, fill the same tube again, and then finish making the rest of the fillets. All of this without having the epoxy cure before I could get it out of the tube. The tubes are available where West System products are sold and online from Hamilton Marine. One nice aspect of the tubes are that the tips are tapered and you simply cut them at the point which gives you the size hole you need. I found that a 'stiffer' mix of epoxy and filler is a little easier to control in terms of starting and stopping the flow.

When deciding between buying the CLC Jimmy Skiff ™ kit or building from plans, I found that it is not a good idea to go the plans route simply to save money. In fact, it would have cost less to buy the kit than what I have spent, and that includes the additional shipping costs. So why build from plans? I chose this path primarily because I wanted the entire experience of building a boat vs assembling a kit. Not that I think building from the kit is just assembly, like gluing together a Revell model. But to me, it's still not the same as taking stock boards and plywood panels and turning them into a beautiful boat. I have enjoyed being able to use remnants of hardwood from other projects around my house when building the various parts of the boat. It also allowed me to make a few small customizations along the way. One of these was to step-back the seat supports by about ¼", leaving a slight overhang. Another was to extend the dagger-board trunk cap down to the center seat (thwart).

Next I will add the deck, mast step, and rear seat top (which is shown in the top photo, but is really only sitting there, unattached).