Archive for March, 2010

Treadle Lathe – Gams Mortises and Tenons

Sunday, March 28th, 2010

We’ve had plans and lams. Now we have gams. OK, legs … and maybe some feet too.

Before I get started showing how I made rather big mortise and tenon joints, let me preempt a question. Someone is bound to ask why I didn’t make much easier half-lap cuts in some pieces before I laminated them. They would be so much easier than cutting big mortises. Simple answer: when I started laminating parts, I had a good idea of general dimensions, but had not yet decided on which style of lathe to make. Should it be one with the wheel sitting back behind the ways, or one with the wheel centered on the headstock? They have completely different construction.

I’ve decided. The lathe will have the wheel centered on the headstock, similar to those by Steve Schmeck and Stephen Sheppard (see the Plans and Lams entry). This makes the contraption a bit more compact while simplifying construction.

photo of drill bits, chisels, and hammerThis part of the work started several months ago with tool acquisition. No, I don’t think I’ll ever need huge mortising chisels more than once, so I didn’t look for them. I did look for, and took a good long time watching the market, a set of Russell Jennings double spur auger bits. A set of these pops up on eBay about every 4 days. A set is 13 bits ranging from 3/16 to 16/16. They are packaged in either a 3 tier wooden box or a canvas roll and date to sometime prior to 1944 when Stanley bought out Russell Jennings. The eBay offerings are often missing one bit and range from mediocre to almost unused condition. Prices vary accordingly and are remarkably predictable if you watch for a while. I waited until I found a complete set that needed only a little cleaning and was lingering around with no bids. My one bid brought it to me at a price I clearly liked. Overnight in some white vinegar cleaned the bits up to near new condition. All were sharp. The smallest was a bit bowed but easily straightened. The chisels in the photo are Narex bench chisels, great value at an affordable price. The mallet is shopmade from black locust.

The uprights / legs are 5 inches by 3 inches in cross section. The feet are 3 inches by 3 inches in cross section. I’m not a tenon engineer and don’t know the optimal size for this application, but I decided to make the tenons 1 inch by 3 inches in cross section, and of course three inches long. Mortises first, or tenons first? I did the mortises first. If one were to do a lot of these, a great big 1 inch mortise chisel would be the tool of choice. a photo collage of drilling and chopping mortises.I don’t think I’ll be making many more, so drills were my choice. Layout was easy since the centers could be placed on the lamination line. Just find the center of the workpiece and layout the 3 inch extent of the mortise. Drilling by hand, without a drill press, needs a bit of practice and several sighting references. It’s really not too hard to make holes that are vertical within the precision needed. Drilling by hand does have some limitations. One cannot overlap holes as can be done with a drill press. Even getting two holes close together can let the bit cut through a thin wall into the nearby hole and “drift” astray. I drilled two one inch holes, one at either end of the mortise and a 3/4 inch hole in between. When working with spur bit augers, the practice is to drill until just the spur starts to exit the far side of the workpiece. Then, turn the piece over and complete the hole from the other side. This technique makes a nice clean hole with no blow out. Waste removal was now a small enough job for bench chisels. Mark a very clean outline. Chisel away waste until half way through. Turn the workpiece and repeat.

The last large tenons I made were for the stretchers for my workbench. They are serviceable, but not pretty. My sawing skill is slowly improving and I think I can make better tenons than before. Yet, I decided to try a technique that I saw on Steve Branam’s “Close Grain” blog. He did a riff on a Chris Schwarz technique using a simple jig and a ryoba saw. It works well, as the picture shows. I varied from the technique Steve shows by using the reflection technique to make the absolutely square shoulder cuts. Note how the edge of the workpiece reflects in a straight line on the saw plate. I added a blue line in the photo to highlight what to look for.

This cut, by the way, is a first class cut and needs to be very clean. Although I don’t show it in the pictures, I marked the cut with my wonderful Czeck Edge marking knife and then reinforced that marked line with a shallow chiseled “V.” That provides a starting notch for the saw while keeping the edge very crisp.

photo of three legs joined to their feetThe ryoba saw is a simple one from the BORG, inexpensive and useful. I saw a question posted in a forum recently from a guy with analysis paralysis on how to best spend $100 for a new ryoba saw. He got no answers while the rest of us are busy cutting up lumber.

The joints fit together very nicely, snug, not sloppy. They will be completed with hot hide glue and drawboring. Lot’s of people have written about drawboring, so I won’t repeat all that here. It’s simple and it works.

Eva Too – Hull Structure & Seat Parts

Friday, March 26th, 2010

photo of hull interior showing bulkheads, carlin knees and carlinsThe MAS epoxy I am using is a bit thinner than the West System epoxy I used on the previous boat. It’s low viscosity and absence of amine blush (have to dig deep into epoxy chemistry for that one) make it the preferred choice for sealing and coating, and there’s a lot of that with this type of boat construction.

Progress on the hull interior is moving along nicely. The bulkheads are now completely fitted, and glued with fillets that make them watertight. The carlin knees are installed. All of the interior surfaces have received two rolled on coats of epoxy as a surface sealant. Short, 4 inch, foam rollers make this coating activity almost enjoyable, and rolling lets me make the coating really thin. Many areas will get two more coats of clear or paint finish and it all adds up to weight that must be carried. The photo shows the carlins being fitted. These are the structural members which support the inner edges of the deck. The “interesting” pair of clamps, sticks, and strings near the far end were used to twist the carlins into “verticality” at that point, a temporary measure while fitting them.

photo of a chiseling operationWhile epoxy cures, there are plenty of small things needing attention. The drawings for this boat include plans for a slatted seat which is made largely from plywood. There are enough plywood cutoffs for this, so it makes good sense. Yet, the design is not one I find appealing. I like traditional cane seats and have purchased yet another from Ed’s Canoe. It’s both a comfortable and beautiful seat. Fitting it is a matter of cutting off the arms which might normally be used for a hanging type mount, and fitting rails to the bottom. The rails get glued to the boat’s bottom and the seat screwed to the rails.

photo of the seat backA lightweight traditional style of seat back consists of two curved slats fixed to a yoke shaped cross piece. Again, this is similar to the previous boat. The thin pieces are 1/4 inch thick, resawed left overs. They are shaped by boiling and then clamping to the curved back of some chairs. The yoke is made eight sided and will be cut to the correct length after the deck and coaming parts are done. We’ll see more of it later.

Did you know that epoxy has nearly infinite open time at 40 degrees? Spring squeaked open for a few days and is now squeaking closed again. The forecast for the next few days predicts very slow epoxy curing.

Eva Too – Taped

Saturday, March 20th, 2010

photo of two people mud wrestlingThese folks look experienced with the glue part of stitch-n-glue boatbuilding.

It’s time to fully fill the seams with thickened epoxy and add fiberglass tape for strength. As an aside, the “tape” is simply fiberglass fabric that is 4 inches wide, finished on each edge to avoid fraying. Filling the seams is the same as I did with “tabbing” in the previous post, spreading thickened epoxy with a rounded stick about 1 inch wide. Affixing the tape is with unthickened epoxy, regular stuff that’s slightly less viscous than molasses. CLC’s instructions suggest painting on a coat of epoxy, pressing the cloth in place, and then painting on more epoxy to saturate the cloth. Another fellow I read suggests soaking the cloth strip in epoxy to saturate it, then placing it in the boat and spreading out the excess with a gloved hand.

photo of inside of hull showing taped seamsI tried both ways, always with gloves. Both methods work, but one feels like you’re retrieving your waffle from a vat of syrup chocolate.

The interior of this boat will get no more fiberglass. A few people glass both the exterior and interior of their boats. I think those are the people who don’t mind the extra weight and want the extra strength for extreme canoeing adventures. This boat will get two very thin coats of epoxy as a sealer. Another finish will be added later for UV protection (epoxy has very little). The first coat is on, applied with a short nap foam roller which really spreads the epoxy thin, helping minimize weight.

Eva Too – Glue Tabs and Salad Dressing

Wednesday, March 17th, 2010

Would you like to see a picture of the stitches in my arm? No, I didn’t think so. Actually, they are almost gone, the self-dissolving kind left from a very minor surgery some time ago.

Some stitch-n-glue builders leave the stitches in the boat. They cover the seams with a thick fillet of epoxy, then epoxy soaked fiberglass cloth, all in one pass. One might follow this approach for either of two reasons, to get a good solid seam by applying everything at once, or to build the boat quickly (Build a boat in a week!). Once the epoxy sets around the wires, they’re there to stay. All that can be done is to snip the tails off on the outside, and deal with the detritus in all the rest of the finishing steps.

photo of intermittent seam gluingThe more persnickety builders do the seams in two steps. The first is “tabbing,” securing the spaces between the wires with thin epoxy fillets. Then the wires can be removed and the full length of the seams reinforced. Guess which camp I’m in. Right! Persickety. You win today’s prize.

Even this, I did in two stages. I mixed epoxy straight out of the pumps with no fillers. I brushed this onto the seams to allow the raw edges to soak up some glue. Then, I mixed in “wood flour” to thicken the epoxy to a consistency midway between mustard (Dijon, not yellow) and peanut butter.  I pressed that into the seams fairing them with a rounded stick (think tongue depressor). I was persnickety about making these extra clean so they won’t need sanding before the cloth layer.

Denatured alcohol (not the drinkable kind) is a good clean up agent for removing epoxy from places it does not belong, such as the handles of my pliers and clamps. Recent reading suggested trying simple white vinegar. Dang! It works better than alcohol. It’s pretty amazing that the stuff we splash on our veggies can remove rust from tools and cut this industrial adhesive. Or, maybe it’s amazing that our digestive pipes handle the solvent?

Well, I won’t be completing this boat in a week, but it will end up prettier than my arm.

Eva Too – Stem Fillers

Tuesday, March 16th, 2010

The stems of most boats are designed to take the abuse of collision, accidental of course, and are often made of hardwood, oak, ash, or something similar. The ends of these stitch-n-glue boats are not hardwood, but simply the join of two 3/16″ thick pieces of plywood. They are made stronger by the addition of fiberglass cloth and by an “end pour” of epoxy resin. The “end pour” can be done by standing boat on end and pouring a puddle of epoxy resin about an inch deep into the end of the boat. a photo collage shows a bare stem, some cardboard patterns, shaping the parts with a spokeshave, and one of the fillers in placeWhile I know that hundreds of these boats have been built that way, it does not appeal to me. I would rather reinforce that area with the traditional material, wood. Well fitted, it will be just as durable, maybe more shock absorbent, and certainly much lighter.

My wooden stem fillers are made from spruce retrieved from the (good lumber) cutoffs pile. Shaping them now before the hull is glued closed makes it easy to get them right. They’ll be glued in place after initial hull glue-up.

As always, click on the photo for a larger version.

Treadle Lathe – Feet

Sunday, March 14th, 2010

photo of three foot piecesWork on something else while epoxy cures on the boat, or while waiting for the shop to be warm enough for epoxy work.

Bookmatched laminated Douglas Fir construction lumber can be made to look reasonably decent. The bookmatching here is the result of ripping a 2×8 directly along a center line and folding it in upon itself to laminate. The top surfaces of these feet are the new edges exposed by the rip.

Yes, same curves on the other ends.