Wednesday, November 26, 2014

Proa float or ama

Summer doesn't start for another five days yet there is a fly in the kitchen; therefore summer is here. A fly has a short lifespan without interference from six inches of rubber band stretched to two feet and thereafter released with a terminal velocity of 270 feet per second and a hasty wiping of alizarin splotches from the wall. Nevertheless and notwithstanding my vegan friends' compassion flies entering the kitchen need to vacate it swiftly because our kitchen is a dipteran war zone. And like Afghanistan, one that I never win. I offer to the world Middleton's Razor (like Hanlon's, only completely different): "There is always one fly left in the kitchen".

Summer is here and therefore I have no excuse to not glue plywood. I found a 6 metre windsurfer sail at the town dump with the boom and the mast foot but not the mast. I think 6 metres is square metres. It's 2m wide at the widest bit and fifteen feet long and that's about 47 square feet which is, I daresay, near enough for North Sails to call it 6 square metres. Here's a scale model:

The metaphorical Next Bit is the float, or ama as Mr. Dierking calls it. I have the plywood already sawn into four four-foot lengths and four eight-foot lengths and to make the float they need turning into four twelve-foot lengths. Mr. Dierking's book recommends a plywood float of six inches square cross-section. I did some calculations.

6x6=36 square inches x 12 foot = 5184 cubic inches ÷ 61023.37795 = 0.084951049 cubic metres x 1,000 litres x 2.20462 = 187 lbs 4 ½ ounces worth of floatation.

7x7 of all that = 255 lbs floatation.

8x8 of all that = 333 lbs floatation.

But I need to minus a chunk for the pointy ends. There are two pointy ends. A cone has a third the volume of a cylinder. (I think.) (Don't you wish you were a kid again and Cudgy Sims was teaching you geometry with frequent diversions into wind drift and the resultant flight of an aeroplane, he having flown Spitfires in the war, and Boyce's trouser leg was hitched just to the point where his ankle was perfectly exposed to the attack of a carefully folded 11-grain paper pellet which you knew would evoke a satisfyingly high-pitched anguished yelp when it struck home with the kinetic energy of two foot-pounds?) -

So we have to assume - for ease of calculation - that the middle three feet are a square box and the two ends are a third each of what I've calculated and therefore a six-inch square float will hold 104 lbs out of the water, a seven-inch float will hold up 142 lbs, and an eight-inch float will hold up 185 lbs. (I bet I got the maths wrong. I usually do.)

I weigh 146 lbs. I have suddenly realised that I could have made a far simpler 12-foot catamaran of two of these floats and stuck a windsurfer sail up and it would have weighed hardly anything and I could have been sailing all last summer. Damn.

A heap of 4mm plywood. Ends staggered 32mm apart. Sanded with a belt sander into a smooth slope.

First plank G-clamped to a length of smooth chipboard to stop it slipping. Merry besmearment of epoxy on the sloping edge. Second plank, similarly epoxied, placed so the scarfed joints overlap. Clamped in place likewise, and unclamped, and clamped again lots of times until the two planks are in line with the right amount of overlap. Plastic bag under and over joint for the epoxy to harden without attaching surplus bits of junk. Finally, piece of plywood clamped over the joint itself. Everything left for 24 hours.

 All disassembled. Two of four perfect scarfed joints. Me = smug.

And here's the scale model showing what an eight-inch float will be like:

 And I expect it will be like that too, all capsized and me wet and sploshing about in the water.

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