The George Blog – Cut Knees and Deben 4-Tonners & Comments

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Cut Knees and Deben 4-Tonners

A while back, helping our daughter to move apartments, I cut my knee quite badly, kneeling on a glass-topped table, which is of course a fundamentally stupid thing to do. Some number of hours later, after having negotiated the US emergency care system, and now the proud possessor of a considerable number of internal and external stitches, I was forced to reconsider my current (non-boat design) work program – which included re-building the garden shed, changing the location of the entry door to our apartment, installing a wood stove etc. What was I going to do with the extra enforced sitting down (albeit with leg stretched out) time? Even exercise (indoor rowing) time was forfeit!

I decided to use the time to do something that I have been wanting to do for a long time – transcribe the original Deben 4-Tonner drawings to a modern format. The original (1936) tracings are very fragile now and I have considerable doubts that they could be printed off, even if I could find someone with a old Diazo machine.

So I transcribed the original Table of Offsets into Prefit (part of the MaxSurf suite of programs) and then created the hull surface in MaxSurf itself (a 3D naval architecture design program). Then I tweaked the resulting "lines" until they fitted as closely as possible, to the original Offsets. This is pretty much what would have happened in 1936 on the laying-off loft floor at the boatyard; the lines were set off and faired full size.

From this I created two drawings: "Table of Offsets" and "Lines", which are a close facsimile of the original tracings. I will be posting these on the website in the next day or so. They will be a free download.

From these two drawings it is not so big a job to recreate the original Sail Plan and Construction Plan – which pretty much completes the original working drawings! I hope to do this in the next few weeks. The knee however is recovering, so other spare time projects are looming ...

Be advised also, that these are not the drawings that exactly represent the Deben 4-Tonners as built. Boatbuilders being boatbuilders, my father added an extra plank to the topsides (essentially making the original "Top of Rail" into "Underside of Deck". And he changed the original coachroof cambers, which are, to say the least, somewhat eccentric on the original drawings, together with various other practical changes.

Anyone downloading the facsimile original drawing may be a little confused by the Table of Offsets, which is not entirely in the format we are used to seeing today. I will be adding some explanatory notes.

I hope that Members, Deben 4-Tonner owners or not, enjoy these drawings.



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