What's the "Welch Axis?"

[Earl Boebert]

In a December 1968 article, the noted UK model yacht designer Stan Witty said:

"... I came to the conclusion long ago that it is the straightness or otherwise of the 'Welch Axis' at any particular angle of heel that determines whether the canoe body stays in balance."

"Balance," in this context, means the ability to sail straight in varying winds.

None of my books, nor Google, has the term.

Thanks,

Earl

[MikeJohns]

Earl
Never heard the term before. He means the major axis and how it trims relative to the angle of heel. Nothing new just whether she trims down by the bow much as she heels.

Hope this helps.

[Earl Boebert]

Thanks. Glad to know my puzzlement wasn't just me :-) Since he talked about curved/straight I thought it might be a variation on the metacentric shelf.

Cheers,

Earl

[Earl Boebert]

Finally found it. Frank Welch was the designer and owner of "Fidelis," the first full sized boat built to Admiral Turner's metacentric shelf theory (Turner was a model yachtsman.) He wrote an article on the metacentric shelf idea in Yachting Magazine for November 1933. Even though that article was signed only by his initials, "Welch Axis" somehow became a synonym for "metacentric shelf," the plan of the line drawn through the centers of area of the heeled underwater sections."

Cheers,

Earl

[Guillermo]

Something else on Turner's metacentric shelf theory:
http://www.onemetre.net/Design/Balance/MetaCent.htm

Cheers.
(Attached: lines for "Rip Tide", mentioned in the text)

[messabout]

The Welch axis concept makes all kinds of sense. I fear there have been many boat designs that have ignored this postulate.

Having built many models and several full sized boats I can attest to the wisdom (or luck) of considering this scheme.

On a similar note I suggest that a design be examined for centroid alignment at various angles of heel. The method consists of connecting the centroids of the immersed sections and viewed in plan and elevation views. Most frequently the plan view line will curve outward at the ends when heeled at low angles. At some angle the line will become straight and at increased angles it will become curved inward at the ends. Simplisticly, this may be blamed for lee helm/weather helm tendencies at different heel angles. If one believes in Newtons second law then he can become stoked about the necessity to get it right.. The Welch Axis thing adds to the fun because that surely must come into play as well. Canoe and kayak paddlers use these phenomena to turn the boats by leaning (artificial heeling). Must be something going on here.