There are 2 sets of frames on Cherokee that are beefier than the others. These support the area of the boat right around the mast, and you can imagine that there's a lot of stress on the boat right there. The original plans called for "grown frames" or laminated frames. Grown frames are just what they sound like; they're chunks of wood that grew in the shape that we need them. All we have to do with them is cut them to size and fit them to the boat. Since the grain of a grown frame naturally follows the curve of the boat, they are exceptionally strong.
In the old days, grown parts were far more common on boats than they are today. There were more trees to choose from, as well as more time to go searching for just the right limb. Nowadays, we tend to glue up thin strips of wood, or laminations, in place of grown frames. The thin strips bend readily, so the grain ends up following the shape of the boat just like a grown frame. The biggest problem with laminations is that they can come apart if the glue fails.
We've decided to laminate a number of parts on Cherokee. We're laminating the stem, keel, stern post, horn timber and those big honkin' frames near the mast. We're using a newer type of epoxy made by West Systems called G/flex. It has a very good record for remaining strongly bonded to wood even when it shrinks and swells, so we're not worried about glue failure.
Here's the glue up for one of the frames:
Most of what you see here is the light, pine wood form that the laminations are glued against. The laminations are the darker strips of wood on the right. Remember the body plan lofting that we were working on for so long? This thing:
We can get the exact shape of the frame that we need to laminate up by drawing it on this lofting board, and then copy the shape onto the pine wood mold in the previous photo. I told you that thing would come in handy...
The glue up for the stern post doesn't look quite so elegant.
All we need here is to get enough thickness to make a good stern post. Later on, we'll plane and cut it to shape. There's piles of milled stem & keel stock under that tarp in the background, also waiting to be glued up.
Our experiment with steam bending the wana showed us that wana likes to spring back in a major way. Here's a board that had been steamed and bent onto the stem / fore keel jig, and then left that way overnight.
Now that's some serious spring back. I think what we'll do is kerf the ends of these laminations to make them more amenable to bending. Kerfing means that we'll slice the wood side to side for a foot or so back from the end, essentially making 2 thinner laminations where there was only one before. It will look like this:
The thinner sections will flex more readily than the thicker one, and we'll coat the inside of the kerf with glue to hold it in place once it's bent to shape.
While all that work has been going on, other folks have been exercising their brains to make drawings like this:
And this:
Trust me, every line you see has a purpose, and has been put there after lots of thinking and measuring, testing, erasing, and trying again. It can make your brain hurt as it tries to wrap itself around viewing curving three-dimensional surfaces in two-dimensional planes. We're trying to work out the exact location of the rabbet in these photos.
No, not that rabbet. We know his location. He's on the couch.
The rabbet on a boat is the groove that the planks fit into along the backbone of the boat.
And if you're interested, the upper photo is the area where the horn timber sweeps down to the stern post. The circles are expansions of the rudder tube as it goes up through the horn timber and along the along the aft edge of the stern post. The lower photo is the area just aft of the stem where the rabbet sweeps back from the top of the stem to the bottom of the keel. And yep, both of these photos are taken from the top of the lofting; in other words, they're upside down.
So, if our heads don't explode, we'll be finishing up that particular chapter of construction drawing work soon.