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Archive for June, 2011

PLEASE NOTE: I am publishing this post unfinished because I will be out of town for a week and unable to work on it while away. I will clean up the writing and add some more when I return. Until then, please enjoy the pictures.

Its been a busy couple of weeks since I got the ribs in and my skin on frame kayak is really taking shape. I am also pleased to be able to say that I think there will be enough room for my feet. With the ribs and keel stringer installed, I put it on the ground and shuffled my feet forward against the deck frame which doubles as a foot rest and found that my heels fit nicely between the ribs, while my toes did not go so far above the deck frame as I had worried they might. With that being said, allow me to outline the steps I have completed.

The ribs have all been pegged into place with 1/8th inch dowels, but there were some final touches to be completed before final installation. All the ribs were sanded smooth and corners rounded over, particularly near where my feet will go and where I will sit for comfort. With the ribs sanded, I placed the keel stringer across the top of the ribs to see which ones needed to be trimmed. I trimmed the ends of the ribs that sat high to allow the stringer to follow a more natural curve, while also anticipating that a certain amount of shimming would be done when the stinger would be installed. When I was happy with how the stringer curved over the ribs, I drilled through the outside of the gunwale and through the rib but without going through the inside of the gunwale. The dowels were inserted without glue, and when the skin is installed, it will prevent the dowels from coming out.

With the ribs installed, I started working on fitting and shaping the stems. I used the the simple method discussed in the Cunningham book for making a pattern and fitting the gunnwales to the stems on each end of the boat, and it worked quickly and accurately for me. With the keel stringer clamped in place but slightly off of center, I flexed it into the profile I wanted it to follow at each end and traced its inner edge on the side of the stem. I cut the stems to follow that profile, and then had to figure out the profile for the front and back of the boat. I drew multiple lines, cut profiles which I knew would be more generous than I would want in the end, mulled things over and cut the final profiles. I think I am happy with how they turned out, but I suppose I wont really know until I get the boat out on the water. At some point I just decided to commit to it.   With a few adjustments to ensure that the stems sat perpendicular to the width of the boat, I lashed them in place using the lashing method used in the Morris book.

After putting the first coaming around my body and also on the boat I decided it was too large. I have since bent a narrower cockpit coaming which I think will look much better and should also work better while rolling.

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Long story short, I got the deck beam lashings in and the ribs steam bent into place. This update will be a bit long, as its been a while since I have written an update on this project, but if you don’t check anything else out, check out the video of me bending a rib into place. Steam bending may be one of my new favorite things to do.

About a month and a half ago I finished lashing the deck beams to the gunwales, and would have liked to start working on cutting rib stock down to size, but I don’t have any green oak yet. The Cunningham book in particular recommends procuring a source of green bending stock early on, but I didn’t think the project would proceed so quickly, so the need for it snuck up on me.

Sure enough the oak was harder to find than I expected. I e-mailed some of the local folks who build greenland kayaks and some of whom teach classes building them to see if I could buy some from them, and they did not have enough to sell me any. I e-mailed a family friend with a sustainable forestry project, and he did not have any, but he was able to recommend another family run mill outside of Salem which might have some wood. Sure enough, I called the guy and it sounded like he had a lot of material in stock. Unfortunately, its a long enough drive that I wasn’t able to get down there until a few weeks later.

Getting down there was its own little adventure. It was down highways and side roads I don’t know, and pretty soon I came to the “pavement ends” sign. And that was before I had even reached the driveway to this place. I got to the red mailbox he had described and realised it was probably red more due to rust than to any paint. I found the place most of 2 miles down a gravel road which rolled up, down and around the rolling hills west of Salem. The first thing that really took my notice when I parked was the large timber framed barn which houses all the oak which is being prepared for the two kilns. Ben Deumling, the owner of the forest and mill told me the frame of the building is entirely put together without metal. All pins, mortises and tenons. Ben was very helpful, helping me find the boards I needed and selling them to me at a very reasonable price. He also said that with a little lead time, he would gladly specially saw boards in dimensions and grain orientations that I or other boatbuilders might need. Pretty cool. If you find yourself needing oak for flooring or boatbuilding, check them out: Zena Forest Products.

A couple weeks ago I got the rib stock planed down to thickness and jointed on one edge at my old high school woodshop. I cut the boards into the strips that would become ribs at home. Figuring out the length of the ribs out was a bit of a process. For the ribs I am using the methods discussed in the Cunningham book. The book talks about using the measurement across your fingers with your hands held flat and your index fingers touching. It talks about using a the length you would measure closer to your finger tips for a lower volume kayak and the longer measurement towards your palms for a higher volume boat with more freeboard. This all seemed fine except that I also had to take into account the fact that my gunwales are wider than the ones discussed in the book. After much debate the compromise I settled on was adding 6 inches to the length at the bow and 2/5 of that length at the stern. This takes into account the width at the base of my fingers at about 7 inches and a 1 inch decrease in length for the depth of the gunwales.

With this dimension figured out, I had to make the rib length gauge. Each rib has a certain amount of material added to the width of the bottom of the gunnels at its set of mortises. The rib gauge provides these distances, starting with the full measurement of 6 inches at the bow and tapering to two fifths of that length at the stern. Between these two lengths, 24 equal increments need to be created so that each of the 25 ribs would receive its own unique length. The Cunningham book has an elegant method for creating these increments without complicated decimals or fractions. Without going into the method here, suffice it to say it was fairly quick and elegant.

With the gauge created I started going through my rib stock to find the best long sections of high quality oak, and started cutting ribs to length, starting at the middle and moving towards each end. This process went very quickly and it was satisfying to start working on significant parts of the boat again. With all the ribs cut to length, I used my tablesaw to cut a sixteenth of an inch off of the thickness of what would be the inside of the ribs for the last 6 inches of their length. Thinning the ends allows the location of curves in the ribs to be focused more towards the gunwales. The transitions from thicker to thinner portions of the ribs were smoothed with a 4 in 1 rasp with blocks held under the ends to act as height guides. Ribs were sanded before being soaked and steamed, though since the combination of soaking and steaming raises the grain and makes the wood feel rough, I would skip sanding before steaming in the future. When I was almost ready to steam the ribs, I put the ribs into water to soak for 24 hours.

While I was getting the ribs ready to bend I was also working on the apparatus I would use for steaming them, and I approached this process with the goal of spending the least amount of money possible. I was able to create the whole assembly for less than $15, so I feel it was a success. For the boiler I bought an old 4 liter pot from a local thrift shop. To transport the steam from the pot to the chamber I bought a threaded barb fitting and 4 feet of 5/8 inch radiator hose. The steam box I made from rigid foam insulation I was able to get for free. I taped the insulation together with duct tape and put a few dowels in it to hold the ribs off the bottom of the chamber. I used a candy thermometer from the kitchen to monitor the temperature within the chamber. I used part of an old t-shirt as the door to the chamber.

With the apparatus ready and the ribs soaked, I was ready to steam them into place. I clamped my bending jig to a work table near the steam chamber. I filled the pot most of the way up with water, and put it on my MSR Whisperlite stove. I waited and watched the temperature gauge. It struck me how long it took to see any change in the temperature within the chamber. When the temperature finally did begin to increase it did so quickly, but it stopped increasing at a lower temperature than I wanted. I raised the height of the steam chamber so the hose would follow a straighter path from the pot and that seemed to allow the steam to flow more easily. The thermometer did not indicate as high a temperature as I would have liked, but seemed high enough to begin.

I put the first 4 ribs in and started my stopwatch. After about 12 minutes I pulled the first one out and gently bent one end with the bending jig, turned it around and bent the other end. I walked over to the boat, slotted the end closer to me into its mortise and gently bent it down to slot the other end in. It went in easily without any drama. I continued and was able to get all but two of the ribs into place. Two of the ribs with the tightest bends broke as I tried to slot the second side in. Throughout the process adjustments were made to how the ribs were bent. They stayed pliable for several minutes after they had been put in. I had Joseph’s help with this aspect of the process and it was very helpful to have someones help so one person could sight along the length of the boat and call out instructions while the other made adjustments.

A few days later I made three replacements for each rib to allow for multiple breakages. I broke one rib before I was able to successfully bend one into one position, and the other rib went in first try.

The steam bending was great fun. Its really incredible to make oak do things it just doesn’t seem like it should be able to do. I have already gotten started on the next steps which seem like they will go quickly and be satisfying as the silhouette of the boat really takes shape. Stay tuned, I will try and additional updates up soon as the next steps proceed.

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