[MHml] Reducing weight

[Tom Speer]

Brian Southwood wrote:
> 
> I have no personal experience with Fortress anchors, but the tip loading must be
> very small for the anchor size, which will reduce the ability to dig in easily
> on a relatively smooth hard bottom. ...

For the Danforth-type anchors, one of the problems in loading up
the tip is that the shank is free to pivot, so the shank does not
contribute to the tip load. Yet the pivoting action is essential
to the anchor's easy stowing and to making it immaterial which
side is up when the anchor lands on the bottom.  

Suppose one were to add a spring between shank and flukes, such
that the force on the spring were a maximum when the shank and
flukes were in line, and a minimum when the flukes were extended
on either side - in other words, an over-center arrangement that
would cause the flukes to snap to one side or the other.  The
strength of the spring could be sized so that it would not
prevent the shank from flipping through if the anchor landed
upside down.  A weak spring that would not support the weight of
the flukes would be one solution.  A somewhat stronger spring
would support the flukes upside down temporarily, but a sharp
jerk on the anchor rode after the anchor hits bottom could ensure
that it snapped through to the right position.

This would allow the shank weight to contribute to the tip load
and would raise the effective center of gravity of the mass
supported by the tip which would significantly add to the tip
load, up to the moment provided by strength of the spring.  Given
that the anchor has to work reliably on each side, this may not
be much, but it could give the anchor a signficant edge in
marginal conditions. Right now, the only tip load is provided by
the short flared pieces extending behind the pivot.  Compared to
that moment, the spring could be a significant addition.

Cheers,

-- 
Tom Speer
tspeer at gte.net
http://home1.gte.net/tspeer
fax: +1 206 878 5269