Monday, June 11, 2012

Problems and solutions...

Well, one does not become a scarfing master with one successful example. In fact, usually one becomes skillful at something by making mistakes and learning from them. I should be well on my way then because my second attempt at scarfing for making the bottom panels of the hull was, shall we say...less elegant. I think only having two panels in line rather than the four I had last time makes it much harder to keep your scarf in registration and cut a clean angle. It was ugly but I patched it up, sanded the heck out of it, and all is well that ends well. At least in scarfing.

I made some good progress today, and learned some more things to boot. The bow and stern were epoxied and screwed onto their respective posts. I was happy to take this step because it meant I no longer was going to be moving those side panels around and was actually going to start building this darn thing! 

The bow, screwed and glued. No turning back now!

The stern, also screwed and glued, and showing the saw kerf which allows the stern plank to fan out. Yes, I realize the epoxy looks hideous. Trust me, it will sand out and look fine.

When stepping back to admire my work I could see something which gave me pause. In fact, it gave me fits! The side panels pulled away from the frames and I could not figure out why. I finally discerned that I needed (once the epoxy had set up) to unscrew the bow and stern posts from the jig so the sides of the boat could relax into their final shape. This led me to discover that the boat needed to be flexed upward a bit to essentially pull the sides back in to the frames. Hard to describe, and hard to discover, but I did finally get the side panels fitting smoothly, and fairly, against the frames without having them forced into place, by wedging a 2X4 under the middle frame, lifting the center of the boat and flexing in the sides. Thank goodness for that thinking chair I spoke of before. It is getting good use!

Using my trusty batten to check the fairness of the side plank as it lies against the frames. There is a very tiny gap at the bow and stern but I would say this is pretty good!

The next step was to drive a single screw top and bottom at each frame to hold the side panels in shape. Then I was able to lay the bottom panel  on top of the side panels and scribe around the entire boat, leaving and inch or so to be trimmed during final fitting of the bottom. My trusty Festool jigsaw made short work of cutting to the line and the result is...
I have built a coffin.
I hope this is not a harbinger of things to come! ;-) 

And that is plenty for this installment. Next, when I get a free day, I will reference screw the bottom panel to the frames, and using a pattern bit in my router trim the bottom panel flush with the side panels. Then epoxy tape the bottom to the sides and I can turn the boat over and start framing the interior! 
Thanks for following along. More updates to come as soon as I can get some more time to work!

Saturday, June 2, 2012

Me as a boat builder is side splitting!

Well, it has been a week of crappy weather and busy times with playing music and work leaving me with little time left to work on the Punt. I managed to get quite a bit done today though so here are the updates.

If you remember at the end of the last post I was preparing to do "scarf" joints on the side planks, joining two 8 foot long planks into one long 16 foot plank to make each side of the Punt. While daunting for a first timer on expensive marine plywood, it turned out to be relatively simple, although a lot of work using only hand tools. (Perhaps I see a Festool power planer in my future...) The process is just marking back from the edge a ratio of at least 8 to 1, which in my case turned out to be 48 millimeters since I am using 6mm ply. So, 48mm is close enough to 5 centimeters so I marked back on each board 5cm and then staggered them back so each edge lined up with the mark beneath it. Then it is simply a matter of cutting, sanding, grinding, routing, or planing at the angle shown and connecting the top line to the bottom front edge as you see below. The plies really give you a nice point of reference so you know where you are at with the scarf. Borrowing my friends jointer plane helped a lot but if I had to do a lot of these I think I would find a quicker way.

Of course, the next step is the glue up. I have a lot of experience with this from furniture making and it is still always stressful. I used a slow set epoxy to give me plenty of time to get things placed just where I wanted. Unfortunately, it was colder than I would have liked and I worried that the epoxy was not going to fully cure but mother nature supplied me with one warm day and so glue up happened. You have to make sure you don't clamp so hard that you starve the joint but hard enough to get things flat. a large rock, two clamps, and a 2X4 does the trick. Wax paper keeps the squeeze-out from gluing the planks to the table!

I did use packing tape along the joint so squeeze out would peel off easily but...forgot to put it on both sides of the seam. I won't make that mistake again! Still, the squeeze out is not too bad, and leads us to the next inevitable step....

Sanding. And sanding, and sanding, and sanding. Propping the joint up a bit insures I am only sanding the epoxy and not the plywood. Once the hard edge disappears, you know you are flush. When seen on edge (I wasn't able to get a decent picture) the joint is invisible. So cool!

Now it is back to using those ever so useful battens. There are several possibilities for how to hold the side panels in place while doing this but rope works for me. The side panels are cut a bit over size and the batten is clamped inside along the top (or bottom depending on how you look at it) of the frames. Then I strike a pencil line along the underside of the batten to mark the actual chine, which is the bottom edge of the boat. I guess technically the chine will be on the bottom panel but you get the idea.

Here is another view of the batten clamped in place. Hey, wait a minute! That is starting to look like a boat!!! Once the line is struck, I stacked both side panels together and using my trusty circular saw cut both at the same time to the line. A little fairing with the jointer plane and the chine is cut. Hmmmm, that little triangle area at the back is looking kinda weird...

I cut the side planks to match the angle of the bow post and beveled the post to match the angle of the planks as they come into it. And now back to that stern piece. 

The stern plank is split (side splitting, get it?) and made ready to mold to the stern post, giving it that characteristic Duck Punt stern. My dozuki japanese saw leaves an almost invisible kerf, perfect for this cut. 

The next step will be bevelling the stern post to match the angle that the stern planks come into it at, scarfing the bottom panels together, and then I can attach the bottom to the sides! More to come so please stay tuned, and your comments are welcome!