Thursday, May 1, 2008

Building a small double paddle pack canoe Part 1: Design and Building Form

So here goes...

I decided to start my own blog, mostly to document the building of various boats, but also to blow off steam about the situation in the world today and what I feel is wrong with it and my existence in it. I'll try when I can to post photos of the boats and relevant building info/tips. The other stuff I'll warn you about ahead of time (orange alert) so you can skip on through. It's for my own cathartic benefit that I include it so I won't feel offended if you don't want to read about my opinions on politics, kids, illness, money etc. I do hope you will appreciate the boat related stuff at any rate because boats are what it's all about, isn't that right? Finally, this blog is a work in progress, so I expect it to evolve over time and possibly give rise to an entirely different species. Through it all, I invite you to sit down with your coffee and bagel (or what have you) and enjoy breakfast with BK.


Last summer Lady BK and I went to the WoodenBoat sponsored boat show in Mystic, CT. As we walked past kayak builder/designer Nick Schade's booth, Lady BK noticed a small pack canoe on display. It was like a little jewel: 10' LOA, basswood with a walnut shouldered tumblehome and Kevlar/carbon fiber hybrid cloth on the inside, giving it the look of an old tweed-covered Fender guitar amplifier. Total weight with seat and backrest: 16#.

Lady BK was instantly in love and asked me to make one for her. Unfortunately, Nick did not have plans for sale at the time. The boat was a prototype and formal plans were still in the works. So we left with my promise to her to pursue the project later in the year when the plans were made available.

The summer went on and I ended up taking a class with traditional lapstrake boat builder Geoff Burke and built a small cedar lapstrake canoe which was raffled off at the end of the class. For the first time in my life, I won a drawing. The next day the boat was strapped to my car for the journey home. One week to the day after I got back, I nearly put my right eye out in a table saw accident.


Warning, rock in the stream dead ahead...

Funny thing about eyes, you rarely look at them because you are always looking out of them. For most guys, the only time we look at our eyes in a mirror is when we do something wrong to them. So imagine my shock when I looked in the mirror to see the extent of the damage and my right eye just looked dead. The brown iris was all gray and cloudy and I had no control over any movement. There was a huge cut on the side where the block of wood hit me but no obvious cut or punture to the eye itself. No matter, all I could see out of it was a bright reddish-orange glow.

A block of pine about 2"x2"x4" weighs next to nothing, but when it comes off the top of a spinning table saw blade at about 175 MPH it has an incredible amount of energy. Yes, I was wearing impact resistant glasses, but the chunk had so much force behind it that it just slapped them off my head and carried on through on its mission of destruction: lacerated cornea and conjunctiva, torn iris, ruptured artery (traumatic hyphema), torn lens capsule, dislocated lens, damaged trabecular meshwork (regulates internal pressure), traumatic cataract, ruptured arteries on retina... I was in a lot of trouble.

You know this right away somehow, just like in the war movies when your buddy says to hang on, you're gonna make it, but you know better and just fade away into oblivion. This was no ordinary poke in the eye. In fact, I was surprised it didn't hurt more, at least right away. I've had punches to the eye that sent me down to the ground and hurt like hell, but in this type of injury it is the combo of extreme speed and mass that do the work. It is called a coup-countrecoup injury, where the eye is violently compressed and then decompressed. Same thing happens inside a race car driver's head when he gets in an accident and dies even though he had no visible injuries, or what happens to a baby in "shaken baby" syndrome. Only in this case the baby was my eye.

Turns out that the second part is the part that causes most of the damage. The energy that was stored during the instant of impact is just as instantly released, causing a mini-tsunami inside the eye, tearing things apart and wreaking general havoc. The immediate danger to vision was posed by the hyphema. 40% of the anterior chamber of the eye was filled with blood and the risk of re-rupture was great. This was to be avoided at all costs as it would likely mean the end of sight for the eye. To prevent further injury, I was instructed to lie motionless in the recliner for three weeks, only moving to go to the bathroom and to see the ophthalmologist once a day. No driving, reading, bending, lifting, grunting or even getting angry. I was put on a pharmacy's worth of drops and pills to try to get the pressure down before it destroyed my optic nerve.

I sat in that recliner and played the guitar for three weeks, re-learning every song I ever knew and playing them all until I couldn't stand them any more. Little by little, some sight returned... and then came the dreaded cataract.

I was told on the first doctor visit what the outcome might be. At best, seriously impaired vision in the eye, at worst, total blindness. A traumatic cataract isn't like an ordinary growing-old variety of cataract. Cataract surgery involves the removal of the entire natural lens in the eye and the replacement with an artificial one. In my case, the pressure inside the back of the eye pushed the gel-like fluid (vitreous humor) right on through the lens capsule and into the front chamber of the eye. Not supposed to happen. Ever. This left a gaping hole along the lens capsule that prevents the chambers from staying separated. When they pulverize the damaged lens to suck it out, there is a high risk of fragments falling back irretrievably into the posterior chamber. My doctor told me I had a 50/50 chance of developing a cataract (but I really think he knew for sure it would happen in my case) and that they would hope it progressed slowly and correct with glasses for as long as they could. He said he would not operate on the eye.

So when last November my vision started to deteriorate, I knew what was happening. My next visit confirmed it. The bad news was that is wasn't progressing slowly but was quickly leading toward blindness. A new prescription helped a bit for a while, but it kept getting worse. Since my iris was torn, it is now "blown" and won't constrict in bright light. The cloudiness of the natural lens is like looking through milky water and the blown pupil makes it look like shining a flashlight through milky water. Then there is the profound double vision and the flare around edges. What does it look like? Take two plastic sandwich bags, the ones with the textured surface, and put them over your eye. Then shine a flashlight into the eye and look around. When I do this with my left eye, things look similar to how they do in the right eye. Now add in double, triple and sometimes quadruple vision and you've just about got it.

Then there is the loss of depth perception. Not total yet because I still have some sight in the eye. The brain can do amazing things when it has to, and one of the things it can do is to take an extremely blurry image and extract info from it that I can use to perceive depth without adding all the blurriness to the image. Spooky.

The good news is that I found a guy in Philadelphia that can do a procedure to reinforce the lens capsule enough for cataract surgery to take place. I am seeing him on May 6 (six hour drive) to find out if I am a candidate. Looks very good from what I've read, but he hasn't examined me yet so I don't want to get my hopes up too high.

Well, that's off my chest. I've been wanting to tell this little tale for a while now. Not to invite you into my little pity party, but just to let you know what I've faced as I try to make this boat.


Here is a photo of the body plan of the boat. It is a drawing of the shapes of the section molds that the boat will be built around:

Each point represents a set of coordinates given by the designer. In this case, they came from a table of "offsets" given in an article that Nick Schade had published in WoodenBoat magazine. The boat is the same canoe we saw at the show and is named Nymph by the designer.

After the points are all plotted out on a 1" grid, the paper is taped securely to a piece of 3/4" plywood and small finishing nails are driven through the paper and into the plywood. A thin, flexible strip of wood (I used wood, Plexiglass and Lexan) called a "batten" is pushed against the nails until it achieves a smooth "fair" curve and then a line is struck against the strip. This proceeds for all of the section molds. We were originally excited to see that Nick used a 1" grid instead of a traditional 2" grid as we assumed it would lead to greater accuracy. In reality, it only served to make the job of fairing out all the points harder, and we had to pull so many nails to get the batten to lie fair that we weren't sure which points were correct. In the end, we went for curves that seemed right and were fair to the eye. They were only small discrepancies so we weren't worried about it. We know that Nick's offsets are designed to be entered into a spreadsheet and drawn out on a plotter printer. I'm sure that the extra points fit that purpose admirable, but we felt they were unnecessary to traditional lofting (boat "lines" drawings).

After the lines were all drawn out, it was time to transfer them onto another sheet of paper. Each line represents a half-template for that particular station mold. We used pencil carbon and a marking wheel to transfer the lines onto the new sheet and then flipped it over to trace the other side. I was less than happy with the wheel method as it seemed to wander a bit. Next time I will use my light table. When each station was drawn out, it was time to glue them onto the actual plywood that the station molds were to be made from. Since this is a symmetrical design, every station but the center would be repeated fore and aft on the boat. This allowed us to nail two sheets of plywood together and cut them out simultaneously. Not only does this cut the time in half, it ensures that each end of the boat will be a perfect mirror image of the other.

In this photo, Lady BK cuts out the basic shapes from the plywood sandwich. She left them a bit shy of the line so I could finish them on the sander:

I used my oscillating spindle sander to get close to the line and Lady BK finished them off with a sharp cabinet rasp and sandpaper. We used spray adhesive to glue them onto the plywood and the upward motion of the sander lifted the edges and created a misleading fuzzy trailer of paper on the edge which we noticed in time to prevent catastrophe. I saturated the edges with cyanoacrylate glue to harden the paper at the edge. It worked well, but next time I will use hot hide glue to hold the paper down.

Here is a shot of all the station molds stacked up so you can get an idea of the boat shape to come:

The next step is to take all of the station molds and fasten them to a long box called a strongback. The box is made of 3/4" plywood and is set rigidly onto legs and then fastidiously leveled. Any subsequent operations or measurements that are done with plumbness as a reference point are dependent on getting the strongback level and secure in place. We spent quite a bit of time leveling the strongback and then placed 50# bags of landscaping stone at either end. After we were satisfied, we set about the task of measuring and marking the positions for the station molds. Nick's design calls for a 10" spacing between molds. We knew ahead of time that we wanted to make the boat a little longer for the slight increase in speed and carrying capacity that would bring. I wanted to just make an extra "0" station (the one in the middle) and leave the spacing at 10", giving an 10' 10" finished boat. This is an extremely lightweight design that calls for 1/8" planking and I wanted the molds to be close enough together that the planking would remain fair (no bumps or hollows) in between the molds. Alas, after we took the time to do make the extra mold and attach and align all the molds onto the strongback, we discovered that there was more to it than just adding the extra station. The other molds pulled the trial battens away from the center molds. We would have to adjust all the molds spacings by trial and error in order for the planking to lay flat and fair on all the molds - more trouble than it was worth. Instead, we opted for an 11" spacing that would yield an 11' boat. We chose to step up the plank thickness by 1/32" to 5/32" to compensate for the wider spacing.

Here is the clamping method we used to get the support blocks for the station molds to be screwed on tightly:

All of the support blocks have been screwed in place and await the attachment of the station molds themselves. Unfortunately, there are no photos of the initial setup but in the next sections you can clearly see the purpose of the molds as we slowly build the canoe around them.

Here I am thicknessing the eight pine strips that were to become the laminated stems. They finished out at 1/8" thick.

As you can see, all but two of them broke when we test clamped them dry over the stem mold.

At is time we made a decision to steam the wood, but we didn't have more pine on hand. Then I remembered some oversized western red cedar blocks I had on hand for classical guitar tops. I lopped off a 3" section of the outer portion of one of the chunks (leaving plenty enough width for the guitars) and Presto!... instant stem stock. These strips practically melted onto the stem forms after 5 minutes of steaming. The next day they were set and we took apart the lamination, added Titebond glue and re-clamped them.

The resulting laminated stems, after trimming to shape, weigh only 3 oz. apiece.


In Part 2 we will cover stock preparation and final mold setup.


1 comment:

Jim said...

I am interested purchasing either a nymph, or a very light weight canoe for my wife and I to paddle together.