Slipper is Building

Designing boats seems just about as addictive as sailing them, but the drawback is that once you’ve designed a boat, you have to build it.

Not everyone feels this way, but as a beginning designer, I couldn’t ask anyone to buy plans for a boat that doesn’t yet exist and so hasn’t been tested. Mostly this is because it’s difficult to predict the sailing characteristics of a boat without having an example in the water; in fact some designers with a lot more training, experience, and talent than me have designed boats that were failures. Those that usually avoid this problem are those who are designing big boats with big budgets– budgets that can extend to tank-testing models. For inexpensive little boats, it’s cheaper to just build one and see how it works.

Admittedly, I can’t quite ignore my suspicion that Slider’s success was a lucky accident. But one major reason I want to build before offering plans of the little cartop cat is that I have a somewhat eccentric way of designing. I start with basic hull forms, and then decide the rest of the boat’s parameters as I go along. This may strike some as a disorganized approach to design, but I think it’s safer and surer than drawing up a boat with all details decided, and then trying to find someone who’s willing to pay for the privilege of testing the design.

At any rate, I based Slipper’s hull forms on Slider’s because I noticed early on that Slider would go to windward quite well without her board. I have to assume that this is due to her hull shapes, since it’s unlikely to have anything to do with the the home-made polytarp mainsail that propelled her for most of her first year. I originally thought to use chine runners on Slider, but chickened out when I realized that the pass to the Gulf was 7 miles to windward of Slider’s home slip on most summer afternoons. I wanted to be sure Slider would be weatherly, since there’s little worse than tacking back and forth and making no progress. So I designed a big daggerboard with a NACA 0009 section. This worked very well; Slider eats up big chunks to windward on each tack. A day soon came when tacking across a sand flat seemed a better choice than sticking to the channel, and when I pulled the board up, I noticed that we didn’t lose a whole lot of pointing ability.

So Slipper represents an inexpensive test bed for such unusual features as chine runners, fixed rudders with skegs and fences, and a free-standing mast.

I bought some cheap lauan underlayment from Lowe’s and laid out my hull panels. I built Slider with the conventional approach to bulkheads, frames, and longitudinals, but with Slipper, I wanted to try stitch-and-glue, because it’s a much smaller and simpler boat. So, taking my panel points from Carlson’s Hulls program, I laid out the panels, and shaped them with a batten. All planking panels came out of 4 sheets of 1/4″ plywood.

I recommend getting or borrowing a sheet-rock T-square– along with a tape measure, this tool makes laying out panels a breeze. I only had to lay out one of each shape, because I could use each panel to lay out its opposite side. I put the good side of the ply inside, in case I wanted to finish the interior bright.

I cut out the panels with a circular saw set slightly deeper than 1/4″ leaving the cutline proud. Then I finished shaping the panels with a sanding block, so that they were as close to perfect as possible.

At this point I had about 4 hours in the build. I spent another 4 hours over a couple of days joining the panel segments into the final panel shapes, ready to drill and wire.

It took me another 3 hours to set up and wire the first hull. I used winding sticks to make sure the hull was not twisted.

As you can see the sheer is still pretty wobbly, but that will improve when the outwales are applied.

Then I tabbed the hull with little strokes of thickened epoxy, let them harden, pulled the wires, and filleted and taped the interior seams. Taping took another couple hours per hull, and there will be sanding to come. I decided to forego the pleasures of beveling an inner stem, and simply joined the panels together at the bows with lots of epoxy and glass. We’ll have to see how that works, but the mantra here is light, simple, cheap, and quick to build.

Today I’ll tape the second hull, and then I can start putting the outwales on them. These were scarfed in the conventional manner, out of 1″ X 3/4″ clear fir, and I’ll try to put up a picture later of the simple jig I used with my table saw to quickly cut perfect scarfs. Ripping, cutting scarfs, and gluing the outwale scarfs took about 3 hours. The panels themselves were scarfed in the Dynamite Payson manner– simply butted together and taped both sides with fiberglass and epoxy. This was how Slider’s panels were done, and they’ve held up just fine.

So today I have to tape the second hull’s interior seams, and both hulls will be 3-D.

Total time spent so far: 21 hours, if my arithmetic is right.

I’ll put updates in as appropriate. I hope I’ll finish the build in a couple months, and when I’m done, I’ll have a safe simple multihull trainer for protected waters– as close to foolproof in its simplicity as possible.

Unfortunately when I was building Slider, I didn’t realize I would be selling plans for the boat someday, so I didn’t take enough pictures during construction. I’m going to try to do better with Slipper.

Ray

March 7, 2009