There are a few photos to show of how I did the sew but first I have to thank Tony Calvert for his suggestions and photos and a character called Corey Freedman http://nz.youtube.com/watch?v=FYWJANqRUsc for a great set of instructional videos. In the end I followed, as much as possible, the Freedman way and so far the results are good.
Also I started by using a strong polyester cotton thread but found it to weak to handle force I was using. So I did a bike trip and ended up at a fabric shop called Haralds. I have no idea if the young guy who owns Haralds (two shops now) is Harald but he was great to deal with. (Phone number 03 352 6763). From there I spied some polyester thread which has the consistency of unwaxed dental floss. It has great tensile strength though I did still manage to break it the odd time. I started using it as a single thread but soon ended up using it double.
He also has a great range of nylon fabric so that may become the place I purchase from, for the next kayak. Plus he has the imagination to understand what I am doing and make great suggestions.
This is how the day started. Cloth is centred on the keelson. I took care to run one of the fabric ripstop ridges down the centre of the keelson. Why? Because I thought it looked nice. :-)
Now sew the bow, including about 50 mm up the centre stringer.
Now down at the stern. Pull the fabric as hard as possible to stretch it along the length of the kayak. Mark the point where the fabric meets the end of the keelson. Now relax and loosen the fabric. Take the fabric off the bow so that the fabric is loose. Then sew up the stern at the place you marked, as in the photo above.
Re-attach the fabric at the bow. Position yourself at the stern, grab the fabric and with one foot pushing against the stern stretch the fabric so that the stern piece covers the stern. This should give you a very tight fitting skin, over the keelson.
Flip the kayak and pin the sides of the fabric to a very loose join over the centre stringer.
Cut away the waste fabric. This should leave you with something like the above photo.
Starting from the cockpit start sewing forward. This is quite a hard job and requires a lot of strength in your left (assuming you are right handed) hand. The left hand has the job of grasping both sides of the fabric and maintaining continuous tension. Look at the YouTube clip of a good explanation of where to make the seam and why. It is well explained.
I did a much stronger stitch than shown in the video. This was for two reasons. The first was that my thread was thinner than the one he was using. He seemed to get better continuous tension on the sewn fabric than I. The second is that I wanted this seam to be as strong as possible, within reason. In the end, what I achieved worked well. But be warned. This is an area for both practice and experimentation, so work at it.
The photo shows the final forward seam before trimming.
This is the seam after trimming. It is trimmed so that I can role the fabric edges over themselves and create a very tidy centre seam that sit on the centre stringer.
There was also a bit of discussion about the suitability of polystyrene as a floatation device. Two issues were raised. The first was the degree that it would take on water and the second was possible long term deterioration. I tested the floatation of the polystyrene by weighing it dry then fully immersing it for two hours and weighing again. I also observed it's flotation behaviour.
Both before and after immersion the polystyrene floated on top of the water and was hard to submerge. (To submerge it 50 mm, I needed to place a full bucket of water on top of it.) The before and after weight photos are below. Clearly the polystyrene look on some water, though this was minimal and surface based. However its buoyancy was affected only very marginally. Of course we all know this from our experience, year after year, of trying to sit on a flutter board when swimming as kids. :-)
However it is definitely possible that the polystyrene will break down over time and, more importantly, once wet may not dry easily, in the hull. For this reason I will look for a better floatation device next time around.
Before
After. The difference was about 150gm water.
:-)
Tomorrow. Finish sewing. Finish preparing the coaming.
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