Ashcroft and Chappelle – are their dinghies related?

Tom Dunderdale’s Iota

Tom Dunderdale’s Iota

I have been intrigued by Tom Dunderdale’s commentary relating to his Iota dinghy design for some weeks (see it here), not least because I am in the happy position of being able to test Tom’s suggestion that the 10ft dinghy design Howard Chappelle gives in his classic work Boatbuilding may have been inspired by an earlier design by Herbert J Ashcroft.

Being a book nut, I happen to own the Chappelle book, and another first published by Ashcroft in 1927. Ashcroft, I should explain, spent much of his life developing a then-novel method of boatbuilding he felt would be particularly suitable for home boatbuilders, and his book has the title Boat Building Simplified. He was very successful in his project, for various versions of the Ashcroft method have been used over many years and his book was reprinted many times.

I thought readers might like to compare the lines drawings and offsets of the two dinghies. Although Chappelle suggested that his boat might be built using the Ashcroft method, I’ve come to the conclusion that Chappelle’s design has significantly more flare forward, and softer bilges forward and harder bilges aft compared with the Ashcroft design, and also has a very attractive tumblehome in the stern. If the two boats were related at the beginning of Chappelle’s design process, by the end the Chappelle boat was quite different and some ways more sophisticated.

What do you think?

Ashcroft 10ft dinghy Chappelle 10ft dinghy Ashcroft completed dinghy

Ashcroft 10ft dinghy; Chappelle 10ft dinghy; completed Ashcroft dinghy

I’ve had various interesting items of correspondence on this post. Always quick to spot an opportunity to make good use of an image editing software, Ed Bachmann had the excellent idea of colouring the Ashcroft lines and superimposing them on the Chappelle lines, which makes the comparison clear. The result below reveals some differences in sheerline I had not previously noticed, but also a striking similarity – to all intents and purposes the central moulds of the two boats are identical.

Superimposed 10ft dinghies

Ashcroft lines in red, Chappelle lines in black

Tom Dunderdale wrote to point out that while Ashcroft’s book presents some photos showing a 9ft pram dinghy with a short foredeck, Chappelle’s boatbuilding provides a set of lines and offsets for a very similar boat that he says would be suitable for bulding using the Ashcroft method, and also remarked that both authors had provided identical specifications for an Ashcroft-built 18-footer; I can find no mention of an 18-footer in the editions I have, so no doubt they exist elsewhere.

It would be very interesting to know more about the correspondence that these two giants of boat design and boatbuilding might have had with each other!

By the way, I’m also struck that Iota is so good looking, and manages to be an excellent sailing performer (that comparison with the Topper small modern sailing scow of the same length is impressive) as well as a good small rower. For more on Tom Dunderdale’s boats, see:

PS On re-reading Thomas Firth Jones book Boats to Go, I notice that he also discusses Chappelle’s dinghy, and uses it for the basis of a small boat design.

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