25 January 2010

Dinghy Build

So, as broke college kids, we'll be spending a lot of time at anchor, instead of marinas. As such, we need a method of getting to shore and back with groceries, water, etc. As the inflatable canoe was deemed unacceptable for such matters, we needed a dinghy.

We had two options. Buy or build. After looking at various inflatables and hard dinghies, I decided they did not meet several of my major requirements; inexpensive,
lightweight, and low maintenance. The inflatables had a high initial purchase, questionable durability, and the added hassle of having to inflate it every time we wanted to use it. The hard dinghies were simply too expensive, not to mention the lightest one I found was almost 100 pounds. Just too heavy for Darcy and I to hoist over the side to lash it on deck. So, we build...

Acrux (or Alpha Crux, or Alpha Crucis, depending on who you ask) is a plywood dinghy of stitch and glue construction. This means she's simple plywood panels that are stitched together with wire ties during the initial construction, then later held structurally with epoxy resin. She's modeled after the D4 plans offered free from www.bateau.com, with some slight modifications. Anyway, here's the process of building a dinghy.

The first step: lofting. Here, we take two measurements from different sides, at a 90 degree angle to each other. At the intersection, you place a dot. After you have an entire panel lofted, to simply connect the dots, and cut the panels out.
The second step: cutting out the panels, and drilling for stitches. This part is fairly straight forward. Cut along the lines you just drew in the lofting phase, then drill a hole every 6 inches on the sides being joined for your wire ties. Here we can see the frames and side panels ready for assembly and stitching.
The third step: stitching it all together. Yet another relatively easy part. Simply align the panels and frame, match up the holes you just drilled, and wire tie them together. Her we have the bow and stern transoms in place, along with the center seat frame to give the boat some shape:
And here she's been flipped and the bottom panels stitched on:
Now, on to making it a functional boat: laying epoxy fillets in the seams. This step provides part of the structural strength to the boat. Mix resin, hardener, and filler (in this case cabosil), and push it into all the internal seams. After this hardens, you can remove the stitching, and sand the outside smooth. Once that happens, you can lay out fiberglass tapes on the outside surfaces. These tapes hold resin against the wood, giving the joint its strength. If done properly, these joints are actually stronger than the wood itself. Sorry, no pics for these steps. I was in the process of moving the dinghy from my bedroom in New Bern to Moyock. And yes, up until this point, all construction took place in my bedroom in New Bern. Don't tell the landlord.

Step number five or six: taping the inside. Again, fiberglass tapes are used over the fillets to give the joints strength. After that, the entire thing is coated in resin to seal it. We opted to cover the entire bottom in fiberglass cloth, just for an added measure of strength, and to add some durability for dragging over beaches and the like.
Steps twenty and twenty-seven: Finishing touches. Now that the structural parts are done, we have to 'glass and laminate the finishing touches. Rubrails, skeg, all that sort of stuff goes on.This process took several days. a lot of things needed epoxy laid on, then sanded down, more epoxy, then sanded. A whole boatload of fun...

Step one hundred forty seven: Flotation. We opted to fill all three seat compartments with chopped polystyrene (read as: old electronic and appliance packaging) for emergency flotation. You could break this dinghy in half now and she'd still float.
And now, the big finale: PAINT. And lots of it, at that. Green, black, and blue. And fluorescent pink. Because who doesn't want a fluorescent pink boat? I lay no claim to the beautiful paint job seen in the following pictures. Caleb and Darcy cut out some stencils, and after the paint was purchased, I left the garage, Darcy, and Acrux to their fate. To be continued... (I think I've exceeded the size for a post.)


1 comment:

  1. Hey, this is really cool! I'm making a little boat from a kit right now, but it was expensive and is pretty finicky to assemble. Next time I'll make a plywood boat like yours - it looks less fussy and more fun!

    Just found your blog today from "Make it from Scratch". Sounds like quite the adventure you're embarking on.