2016.12.28 - Runner Bearing Surfaces
The last task of the day was to glue the bearing surfaces onto the capping piece on the top of the runners. This is the surface upon which the hatch will slide. The idea is that this is made of something that is both tough and slippery. Tough so that the hatch running up and down does not wear it away and slippery so that the hatch slides easily.
Traditionally this is made of two strips of brass each side, one on the runners and one on the hatch. However, the cost of two 42" lengths of brass 1/8" thick and 30mm wide is prohibitive so I looked around for an alternative and found that Tufnol is a good substitute at a fraction of the cost of brass.
I bought a sheet 600mm x 300mm x 3mm at a cost of £24.16 including shipping and tax and this afternoon I cut four lengths from this sheet 30mm wide. It cuts easily using the band saw. Amazing stuff. You can reading some of the history about it on the Tufnol we site which may be found at http://www.tufnol.com/company/company_development.aspx.
This is how the boat looks at the moment. The cramps are being used to weigh down the piece of plywood which is slightly too narrow to fit across the runners, so several strips of the cedar battens have been used to spread the load of the cramps across the runners.
Underneath the cedar strips are two lengths of pine, one either side resting on the Tufnol strips that have been epoxied to the runners. You can see the piece of plastic used to cover the join in the Tufnol so that any epoxy that oozes through the join does not stick to the pine.
You can see the Tufnol strips here, it's the thin strip directly underneath the piece of pine.
Whale brand is the type of Tufnol used. These two off cuts maybe used on the main hatch. The trouble is that you do not want the hatch to be too easy to move or it will open and close by itself every time you hit a wave. I'll see how it goes with just the epoxied wood on the Tufnol and if that is too stiff then I'll glue a piece of Tufnol on the hatch as well.