What John Welsford does with mashed potato

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The transom for John Welsford’s new cruising dinghy design, Pilgrim. Read
about this interesting small boat at his Pilgrim Diaries

Well known New Zealand boat designer, builder and cruiser John Welsford has written tell us about a technique he has developed for testing the rot-resisting properties of unknown timber and plywood:

‘Hi Gav,

‘I thought that you might like to put my comment about mashed spuds in connection with rot testing.

‘Just to stir things up a bit you understand!

‘Rot is due to fungus and needs food, moisture and oxygen in order to grow and spread. Cut off one or more of those and you don’t get rot.

‘Also, rot, like most fungi, spreads far more rapidly in warm conditions.

‘My test method involves placing the sample on a dish in the warmth of the kitchen, and covering it with mashed potato. Potatoes are almost all starch, a form of sugar, and mashing it up with milk brings even more sugars. Mashed potatoes also hold moisture and, being light and fluffy (if made properly) they admit oxygen. So a layer of mashed ‘taties accelerates the rate at which rot takes hold and multiply and is a workable if unusual method of testing wood for susceptibilty for fungal decay. You should see what I do with raspberry jam!

‘Yours, John’

Many thanks John. I might try it some time, though I’d be a bit concerned about this as a practical test. Done properly, it would demand not just well made mash, but would also require brewing up quite a number of different samples. It’s a very interesting idea, but could also be a recipe for trouble in the kitchen that could test more than a piece of wood!

I wonder whether it would work if conducted where no-one goes, round the back of the shed in the summer, and under a plastic sheet?

For more intheboatshed.net posts relating to John Welsford’s boat plans, click here.

For more on John’s plans, see his website; also, there’s a nice new weblog about building a small cruising yacht to his Fafnir plans here.

John Welsford starts making sawdust on his Pilgrim cruising dinghy project

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John Welsford cuts out the transom for Pilgrim

It’s always useful to see how the professionals do it, so I’m pleased to link to John Welsford’s diary recording his work on this new cruising dinghy, Pilgrim.

The key points in the latest entry are testing an unknown plywood, including a routine previously unknown to me that involves burying it in mashed potato, marking out using a house-builder’s roofing square (clearly his equivalent of the dry-wall square) and a flexible batten supported by tins of food, and cutting out with an electric saw.

On the latter point, I gather he uses a veneer blade, and I must say the results are impressively free of splintering.

To read the this entry at John’s website, click here.