[MHml] DynaRig, Mast-Aft, Bi-Plane sailing rigs

[brian eiland]

Brian had written:
> The email I sent out on the Dynarig was meant to show how the Falcon's
> Dynarig could be brought down in complexity, price, and weight. Certainly
it
> is still a 'square rigger', a very modern version at that, and will never
> compete with a free-standing unirig in expense nor weight aloft. But it has
shown its capabilities in performance, and on all 3 points of sail.
____________________________________________
Here is that email I had sent out. I don't believe I posted this here before.
Excuse me if I did.

In reference to our phone conversation last week about a 40-ish multihull for
your charter business, and your inquiry about my Dynarig vessel, I offer a few
quick observations. 

Unlike my 'single-masted ketch' design that I feel is not necessarily
appropriate for a vessel of less than 45 feet, the DynaRig is appropriate for
this smaller size vessel. In fact a '3-panel' dynarig might be considered
rather than the 4 panels of my new 63 foot DynaRig cat design, or the 5 panels
of Falcon. However, I would still favor the 4 panel configuration, as it
offers more variation in reef-able sail areas. And with my simplified sail
furling mechanisms, it doesn't add that much weight or complication to the
overall rig. 

Falcon's dynarig was complicated by requiring the sails to be furled up inside
the mast thru a hollow slot on one side; 

1)       the mast itself needed a slot in itself all the way down one side of
the already weaker side of an elliptical cross-section. This necessitated an
internal structure be built into the carbon mast section to reinforce it at
the slot area 

2)       the furling mechanism then needed to be built inside the mast
section, and a complicated track mechanism was required to guide the edges of
the sails out onto the bridges to the yardarms & the yardarms themselves 

  

I am proposing a much simpler furling and track mechanism for this modern
square-rigger concept: 

1)       The mast will not have internal stowage of the sails, so no slot is
required, nor internal support structure. It will be a simple elliptical
section that will taper at either end to a smaller section at the top and a
circular section at the bottom...not that much more complicated than an
ordinary carbon mast for a sloop rigged vessel with a mainsail attached. It
might also be a 'sealed unit' for ultimate flotation purposes. 

2)       Each rectangular sail will furl around a 'wire' (PBO, Kevlar,
Spectra, carbon, etc) sewn across its mid-girth, and having eyes at both ends
that clevis pin into 'continuous line furling drums' as you might find on
'Code' type reaching sails. The sails are constructed of low-tech,
light-weight ordinary Dacron, and are of such relatively small dimensions that
when furled around a very small diameter 'wire', they present a very small
diameter package to the elements when 'stowed away'. Each individual sail
panel can be quickly and easily replaced, and inexpensively as well. 

3)       The furling drums are incorporated into the leading edges of the
yardarms/bridges so as to present less windage, and they are 'stacked' up
vertically end to end in a line such that they 'share' bearings at either end.
One small electric motor drives each panel for furling. For each panel of sail
there are two (top & bottom) additional motors to unfurl the sail. 

4)       The yardarm 'bridges' can be shorter in length than Falcon's with
many inherent advantages including the more readily usable 'forestay
arrangement' with or without a 'code' type reaching sail. Shorter lever arms
requires less power to rotate the rig as a whole. 

5)       Three of the yardarms are of equal length thus less production
cost...in fact probably these three would be only slightly more expensive than
the elaborate furling/stowing booms now found on many 'ordinary', modern,
short-handed sloop rigs.   

6)       The low-tech, Dacron sails of this rig should present some
considerable savings over those modern sails for Bermudan rigs, and help
offset the other initial extra cost of the Dynarig. 

7)       The sealed mast and yardarms could offer the flotation for the
ultimate non-capsizing protection. 

  

These proposed changes to the original Falcon's interpretation of the DynaRig
concept should result in a less expensive version, which is just as viable in
sailing characteristics as the Maltese Falcon is proving to be.