Seven Safety Criteria
1 – To dig in instantly
As the anchor is the boat’s most important
piece of safety equipment, it must be quick to deploy and it must set
immediately, The SPADE anchor has only one tip, and it is very sharp. Nearly
50% of the anchor’s total weight is applied directly onto this tip. This
unique characteristic gives the spade anchor a superior ability to penetrate
the sea floor, even into hard sand and through weed.
The sharper the instrument, and the greater
the force (weight), the quicker and more reliably will it penetrate the sea
2 – Deep penetration
Many existing anchors have their preferred
sea bottoms: they are not versatile devices! Many sailors carry several
types of anchor, imagining each will suit its particular type of sea bottom.
This is, at best, an inconvenient solution for the problem of differing sea
floors; but at worst, in an emergency, it can be disastrous. You normally do
not have the time, or the ability, to know what kind of bottom you will meet
– especially in an emergency.
The angle of attack at which an anchor meets
the bottom dictates how well it will penetrate the bottom. The SPADE anchor
has been designed to meet the bottom at an angle similar to that used with a
chisel working wood: it has to penetrate. Many other anchors meet the
bottom at an angle like that used on a spreader pushing filler: they can
only resist penetration. SPADE’s logically optimum angle of attack,
together with its sharp edges and point, explain why the SPADE anchor has
such superior penetration characteristics.
In dense weed the SPADE’s unique design
allows it to penetrate through the weed, before digging deeply into the
The shape of a “cutting tool” is the only one
designed to penetrate.
The SPADE anchor is the only one to have
these design characteristics (patented).
3 – Once
set, the anchor must give the maximum holding power without dragging
An Anchor that digs in but doesn’t hold is
the worse than useless: it is positively dangerous. On arrival your anchor
is set, and everything seems to be in order. But it is a false sense of
security: when the wind gets up, such an anchor lets go, and the boat starts
Over many years, aeronautical engineers have
devised a system to measure the resistance of various profiles to movement
through a fluid medium. This measure is called the coefficient of resistance
of the profile. For engineers, “fluid mediums” include all materials that
can deform to allow an object to pass through: “fluid mediums” include all
materials in the range from air, water and other liquids, to sand, soil, and
The concave profile has the highest
coefficient of resistance (1.7) for moving through any fluid movement.
Strangely, anchors have never been designed with profiles much beyond the
flat profile (coefficient 1.2), and most just used a chevron profile
(coefficient 0.5 – 1.0).
The SPADE anchor is designed around the
concave profile, which ensures that, once buried, it will compact the sea
floor material within its form, rather than sliding through it like a
plough. It must offer much higher resistance to movement that anchors using
The results of Aerospace research prove that
the concave profile is by far the most resistant to movement
through any fluid medium.
4 – If
the traction force exceeds the bottom holding characteristics, the anchor
must offer constant, and maximum, resistance to dragging.
A basic requirement of an anchor is that it
must not let go under strong load. If a strong wind causes the anchor to let
go, the boat will turn side-on to the wind, and soon start moving with
speed. As the boat gains momentum the anchor will never be able to hold
Numerous comparative tests have shown how
conventional anchors work. It appears that few are able to reliably resist
The SPADE anchor, during the same type of
tests, has shown an exceptionally high holding power. Equally importantly,
when tested under loads so high that the anchor must begin through the
bottom, SPADE anchors have consistently offered a very high and fairly
constant resistance to movement.
Typical behaviour of plough anchors, or of flat
anchors without a stabilising strut.
The anchor’s hold is cyclical: dig in,
release, dig in, release … In some cases the anchor will not be able to
dig in again.
Typical behavior of fluke anchors with a
The anchor drags, often at the worst moment, and will never dig in
again: it skates across the bottom on its side.
The SPADE anchor
always remains deeply buried, without
cyclic (or corkscrewing) behaviour, or releasing its hold: it continues
to assure maximum holding power even under extreme load.
5 – The
anchor must keep on holding, regardless of the shift in direction of either
the wind or the current.
With a major change in direction of wind (or
current) most anchors will break free. The anchor then drags, hopefully for
only a few metres, before setting again under the new load direction.
Thanks to its concave profile, and to its
high holding power, SPADE anchors pivot within the bottom, towards the new
direction of load. As the new load comes on, the SPADE anchor just sets in a
little deeper, and keeps on holding.
6 – The
design must not allow the anchor line to become snagged by the anchor
7 – The
anchor must be built strongly enough to withstand very high loads.