Most narrow boat bottom boards are 3” (75mm) thick when they start their working life, whether on a wooden boat or a composite one. There is a built in understanding that by working on our shallow British canals at least 1” is going to be worn away by simply rubbing along the bottom. There’s even more wear on the chine; the corner between bottom and side planking, especially if it is not kept well protected with some steel shoeing plate.

So, it was a slight surprise when it was rumoured that Saturn was originally built with bottom boards only 2½” thick. Could this be true? Why the difference to the accepted norm?

A bit of thought and research gave us some possible answers. With a big, square sectioned, full capacity narrow boat carrying 25 tons or so, most of the bottom boards are nearly as long as the full width of the hull, almost 7’O”, and the thickness of the bottom is integral to the transverse strength of the boat.

Any thing less than 3” (or 2½” after a few year’s wear) is likely to be getting rather weak.

However, with a smaller barrel sided fly-boat like Saturn few of the boards are longer than 6’O” anyway, and then only for a short length in the middle, so the strength is not so critical. Add to that the expectation that the lighter high value cargoes would only rarely push it down to the bottom of the canal and we’ve got a good Shropshire Union boat builder’s reason for using thinner timber to save both money and tonnage.

Then we re-read the S.U. boat building specification in the archives in Gloucester again and sure enough it says:
“Bottoms. English Elm. Sided 3” for 16’0” from stem. Remainder 2½”...

Why only 16’0” at full thickness? Presumably because you always try and load a canal boat down by the head slightly, so that is where it is going to wear most.

Why didn’t we just measure Saturn’s bottom board thickness ages ago and have done with it? Well, with an old boat that’s seen a bit of canal life it is really quite difficult to tell. The boards have all worn a lot, and the original spikes were all deeply countersunk precisely because of this expected wear.

The only places that the proper thickness is likely to have been preserved is under the stem post where a short section of bottom board has been protected by a continuation of the heavy iron stem bar, and right at the stern, where an iron skeg plate projects out under the rudder.

So we have had to wait for the final pulling out before Malcolm Webster could investigate properly. Now it has been done, and there was the evidence - 2½” thick.

When Saturn’s rebuilding specification was put out to tender we conceded that the boat builder might have to choose something other than the traditional elm for the bottom boards. The general understanding was - post Dutch Elm Disease- that elm trees of sufficient quality and size were virtually impossible to obtain in this country.

Happily however, Ian Kemp, another notoriously finicky restoration boat builder in the Midlands, has recently managed to source sufficient high quality elm to re-bottom the steamer President, and with that recommendation to hand, Malcolm has now placed our order for Saturn’s new bottom boards in elm with the same timber merchant. We now await delivery. Meanwhile all the other timber is seasoning quite satisfactorily.

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