Cutting wood

This is going too slow. Last week I started to mark the plywood and yesterday, after double, triple and quadruple checking (hehe), started to cut out the bottom and lower planks. Quite a few people recommended a circular saw with a plywood blade set shallow just deep enough to make a clean cut. I tried it but didn't like the results, more dangerous, even the subtle curve bogged the saw enough to make me nervous. To be fair I was using a cordless 5 1/2 saw which I've successfully used to cut up to 1 inch stock with no problem; it just didn't work well for plywood. So I went back to my variable jig saw with a fine blade and small rotation, for a slower but very precise cut. 

I've also built a rolling cradle for the boat, mostly to move outside for sanding and to make room in my garage. Below are pictures of the cradle with the bottom piece, initial stitching just enough to see some shape; and of the dry fit stem. So far so good.

A few notes about the design changes. The four pieces of plywood "just" fit. So close that I didn't know if I had enough room to create the transom doublers and other odds and ends pieces--not to mention any room for even the smallest mistake.  My other concern is I wanted to slightly increase the displacement. I ended up increasing the depth to 5" and shorted the length by 10% so it's now 12'6"

Other progress. I had many stem options including just stitch and glue, an inner stem, two part stem or a rabbited stem which is what I'm going to try.

Below shows the stem pattern.

On each side of the stem, I routed a 1/4 deep rabbet and then chiseled a bevel angled for each plank.

I made a few minor changes to the design...but I'll show that next time along with the plywood layout.

I ordered four sheets of 6mm Okoume from Edensaw woods http://www.edensaw.com/ which was about the same cost as other sources but I could pick it up in Tacoma without paying $40 a sheet just for transportation.

I ordered a gallon of Raka resin and its 350 hardener. It gets good reviews and easy to mix 2:1 ratio.To start off, I scarfed the plywood together into 2 4'x8'x16' sheets using 10:1 slope. I used a plane to remove most of the wood and finished with a belt sander and flat vibration sheet sander. As you can see the layers make a nice guideline. 
















I mixed up a couple ounces of epoxy, applied it to the feathered ends, let it soak in a few minutes. Next I mixed in some wood flour until it was like thin peanut butter and used a wooden fork put a thin layer on the plywood before joining the scarfs together. I held down each pair with a line of filled water jugs for two days.

What's it going to weigh?

Freeships will get me part of the way. It allows for input of material density and thickness which it combines with developed surface areas to obtain a total weight as in the table below.

 The rest I'll have to do by hand, or using excel, in this case. The cleats will do on top of the bulkheads to strengthen the plywood edge and give a good gluing surface. The support beams will be spruce or pine crosspieces to support the thin seat plywood--I'm going with a beam every 6 inches which is close to Skene's scantlings. Next is I'm going to cover the plywood with thin fiberglass weave two coats of epoxy and another layer just on the bottom with one coat for traction and to strengthen to bottom. According to my original Gougeon brothers Boat Construction a pound of epoxy covers about 35 sq feet, I've got 52 sq feet in the planking. Add long strips of wood for the inner and outer gunwales. I added a pound for the 4 bronze oarlocks I'm going to canalize off one of my rotted hulls.

Add it all up and wow! I'm at 71 pounds. Of course I haven't added the fiberglass tape on the seams, nor breast hooks and paint of course but 75 to 80 pounds looks realistic. Nice. 

Next time I'm going to show the plywood layout. 

Bulkheads

Added bulkhead, which also serve as the three primary frames. While stitch and glue construction can be done without a frame, it's difficult to control the thin plywood; adding a frame helps. The aft and bow frame will serve as bulkheads for the water tight compartments as well as support the seat. The midship frame will support the mid seat and will be hollowed out to save weight. In Freeship there are several ways to do this. I added transverse planes, copies the intersections with the planks, removed the planes, than built the frames point by point. It's a bit tedious but gives good result. It also gives me good outline from which I can subtract the planking thickness later to get exact frame dimensions.

Freeship allows each layer, which in this case is each part of the boat, to have a set thickness and pounds per cubic foot. I plan to use occume mahogany, with an average density of 27 pounds per cubic foot. I set it as 30 pounds in Freeship with mostly 1/4 inch plywood. That gives me a total on only 49 pounds so far; I'm not done yet, but that's encouraging. This little car-topper looks realistic!

Next I'll add the supporting frames for the seats and start on the developed parts layout on sheet plywood. I hope to order the wood by next week.

Completing the Seat Tops

Decided to double check the hull before trimming the seats because after the seat sides are created, it's very difficult to make any further changes. I tweaked a few things using the scale tool applied to difference layers. I built each layer as a boat part (e.g. shear plant, chine plank etc). Still trying to keep hull weight and the boats purpose for rowing, fishing and photograph in mind, I reduced the bow height to 21", which will be fine for the protected waters where I plan to use this boat. I raised the minimum shear height to 14 inches for good rowing oarlock positions; this required I do some proportional scaling (manually) from the bow to middle of the boat for the sheer and mid planks. Lastly at 4 inches draft the displacement was 260 pounds which was a bit low. Against for rowing without an outrigger, I scaled the overall beam to 41" wide and increased the bottom beam by almost two inches to raise displacement to 300 pounds--a knowing compromise to get better initial stability while probably reducing speed.

I shifted the mid seat aft by a few inches so it was over the center of buoyancy (`6.4' from stern). From prior boats, I know water tends to pool in the end seats so raised the ends by a half inch so they had a gentle slope. Using the point>intersect-layers command identified where each seat intersected the middle plank. Then it was a simple matter of collapsing the points outside the hull so their outside edges fell on the mid plank points.

The results are below:

Next time I'll add bulkheads and the hull weight estimate.

Adding seats

Well I know I've been too busy when I can't get to something I enjoy like messing in boats. Tomorrow Spring starts!

Back to the drawing board (or computer). This time adding seats. I've got two options, build seats as part of watertight bulkheads or if that's too heavy-one with simple seats and canoe floating bags. I'll use freeship to do most of the estimate. I prefer the watertight bulkheads because it's safer because it adds flotation abeam which makes is inherently more stable than float bags or compartments at the end of the boat.  It also serves as storage for dry cloths after recovering the boat.

Most of the advise I see online from Woodenboat (http://www.woodenboatpeople.com) about seats say they need to be at least 7 inches off the floor and about 6 inches below the oarlocks. I've got 14 inch mid ship height, so I'm going to go with 8 inch seats (from baseline). The aft seat will be for my wife, not for rowing so I'll make it the same height so oars can lay flat for short periods. The bow seat shear hieght will be about 16 or 17 inches, so I'm going to make that one 9.5 inches from the baseline. Using the dialog box I chose not to show all the layers (e.g., bottom, sides etc) but leave the control lines so I could continue to see the hull as I placed the seats. Below is the perspective and plan view. Note, I haven't trimmed off the excess where it intercepts the hull. I'll do that next time.

In freeships the easiest way to make seat is add the points away from the boat, select all the points, create a layer/face and finally use transform>move to place it on the hull. I used edge>split to add a curve to the seats; it adds no functional improvement but aesthetically makes for a pretty boat.