> I am currently building my second CLC yare with an eye towards racing in
> several local races. I am considering using aircraft dacron for the deck
> instead of 3mm okume. So far i am finding limited infromation on this
> topic. My current plan is to layup custom carbon fiber deck beams that
> will support the dacron. As well as custom fitted "knees" at the
> bow and stern to give a little extra support as well as an aditional
> fastening point for the dacron. Any thought or tips would be appreciated.

In my opinion, carbon fiber deck beams would not only be overkill, but they would be more expensive, time-consuming, and more difficult to work with than using wood. I would not waste my time and money on them.

Look at the basic concept of what you are building and you should be able to identify a lightweight, round bottom boat with a covered deck. It is not much different from a fabric-decked canoe. A canoe (U.S. use of the word) does not usually have a deck, so it does not rely on the deck to add any structural strength. A kayak *might* need the structural strength that a deck provides, kind of like how an arch needs a keystone. With most molded fiberglass or polyethylene, or woodstrip-built kayaks the deck and hull combine to create a solid, rigid entity, where the `skin' carries all the forces. With skin on frame boats the rib structure provides the strength, and the skin just keeps out the ocean.

What you are doing is building a bottom ( hull) where the composite `skin' takes the forces, and a top ( deck) where you will need ribs to carry the forces. This is really a lot like a canoe which uses thwarts and gunwales to provide linear rigidity and strength, and to keep the hull shape from collapsing.

The Yare uses a sheer chine for attaching the deck. This is in the same place, and looks ( structurally) like the inner gunwale on a canoe. The deck is attached over formed deckbeams, which look, and probably function, like thwarts on a canoe. These happen to be arched, though. I suspect the deck ties these things together very strongly. Chris Kulczycki's book shows a few ways to make nice, curved deck beams from thin strips of wood. This is rapid, cheap, and the result is both strong and light. The wood deck beams will also accept staples for holding the dacron cloth in place. From what I have seen of carbon fiber parts, I don't think you would be able to use staples, so attaching the dacron would be more of a challenge.

I think what I would do if I were building something like this is to build the Yare with the sheer clamp strip on the outside of the hull, and not on the inside. Since the ends would meet outside the boat the wood for these wold have to be about 6 or 8 inches longer than the normal design calls for, but this is not such a big deal. When the two hull panels are wired together you'll make a joint at bow and stern for these sheer chines. If you don't want a really pointy end ( and you probably don't) cut these pieces off about an inch past the end of the plywood and use a rasp or a sander with coarse sandpaper to round the end.

look at the design for skin-on-frame kayaks and you wil see that there is a strip (or 3) running the length of the fore deck, and also one, two or more running the length of the aft deck. These either sit on top of the ribs, or are inset so they are level with the tops of the ribs. In your case you will have deck beams instead of ribs. (Just think of the deck beams as being the upper half of ribs). In addition to the deck beams that define the front and back of the cockpit you will probably need at least one more deck beam between the cockpit and each end of the boat. I'd space two in front and one in back, giving me a total of 5 deckbeams. You might want to just use a single deckbeam between the cockpit and the bow, and just have 4 deckbeams.

To secure the deckbeams to the sheer chine I would use small pieces of wood as cleats, or make metal brackets from brass or aluminum and secure them with bronze or stainless steel bolts. That would be the esy way. The more difficult way would be to fit the ends of the deckbeams over the sheer chine in such a way that I could hold them on with a single, long, bolt.

The strips that sit on top of the deck beams are held in place with ringshank nails or small screws, or you could just use a few drops of epoxy cement.

By having the sheer chine on the outside I can use it as an anchoring area for the dacron top. Just stretch the fabric over the top of the boat, wrap it onto the sheer chine and use some staples. You can cover the staples with a thin, varnished strip of wood ( a rubbing strip) held on with ringshank nails or small screws. This can be made of several short lengths, and it can be easily replaced when it gets beat up and scratched. The alternative is to risk a small nick or tear at the edge of your cover every time your boat comes near a dock. Those little rips greatly weaken the fabric and easily turn into bigger tears, which will force you to replace the fabric.

For an idea on fabric canoe decks look at David Hazen's book on stripbuilding canoes and kayaks. (www.amazon.com). He shows a method for attaching the fabric top that is lightweight, neat, and efficient, and does not use staples.

Hope this helps. Good luck with your building.

Paul G. Jacobson