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

Sat May 26 17:37:48 EST 2007

G'day,

How on earth can you tell how well MF is doing from 3 photos?  Looks to me
like it is heeling a lot (not surprising with all that weight aloft) and is
pushing a lot of water out of the way which may or may not be because it is
going fast.  Any boat will look good from a distance on a reach in the trade
winds.

Even if it is performing well, there is no reason whatsoever to believe a
cheaper, less complex version will work on a smallish cat.  Instead of
trying to sell it to some poor unsuspecting mug, build one and prove it
works.  Do the same with your other rig, and you will be able to use facts,
rather than glossy pictures of distant boats to make your points.

There will always be a point of sail on which the leeward biplane rig is
blanketed.  Does not matter whether it is a fast or a slow boat.  However,
the solution is very simple.  Head 15 degrees high for half the time, and 15
lower for the other half. Means sailing 3.5% further, which is no big deal.
Compare this with stayed rigs where sailing anything much broader than a
beam reach means the headsail is blanketed by the main so is flapping around
and useless, and the main cannot be eased without hitting the spreaders or
diamonds, which is expensive, slow and dangerous.

General consensus, (and my experience) is that on a reach, biplane rigs are
unbeatable, even allowing for the course changes.  Should point out that my
experience is limited to a  beach cat with two windsurfer rigs.  Very heavy,
very rough and the sails had seen better days.  Lousy upwind for these
reasons, but on a reach, it went past a Paper Tiger (longer, racier,
lighter, bit less sail area) with ease.

Set up the unstayed rig's lines properly, and there is no need to do
anything dangerous.  Unlike a stayed rig with flogging sheets and sails,
winches and travellers all just waiting to damage unsuspecting crew.

Peter was not comparing biplanes and bimarans, but pointing out that your
mysterious Mr XXXX would be better off with a bimaran than a dynarig.

regards,
Rob

----- Original Message ----- 
From: "brian eiland" <beiland at usa.net>
To: "Informed discussion of multihull issues" <multihulls at steamradio.com>
Sent: Friday, May 25, 2007 9:42 AM
Subject: Re: [MHml] DynaRig, Mast-Aft, Bi-Plane sailing rigs

>
>
> 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.
>
> Rob replied:
> > You could have added that not only is it vastly more expensive and many
> > times heavier than the unstayed biplane, it is also much less safe,
> > unreliable, hard to handle, with very high maintenance and will not
perform
> > as well on any point of sail, including reaching.
>
> Brian replied:
> The Dynarig appears to be doing very well in the St Barts trade winds
> <http://boatdesign.net/forums/showpost.php?p=142295&postcount=94>
> (I belive that 3rd photo might be a power reach). I could probably find a
few
> more such photos as well.
>
> On the other hand here are a few observations on the bi-plane rig:
> ___________________________________________________________
> <http://www.boatdesign.net/forums/showpost.php?p=89886&postcount=20>
> Biplane rig
> Thomas Firth jones tried such a rig on his coastal cruising catamaran
named
> Dandy, but after two seasons gave up on it. Apparently it works best on
very
> fast cats because, along with the faster speed comes an aparent wind that
is
> further forward. This may explane why it is given so much praise in the
faster
> sailing multi community.
>
> The boat in question will not be nearly that fast. Most likely it will be
a
> D/L 100 boat or damn near. Especially when all the long voyaging stores
are
> loaded aboard. Although it will most certainly be faster than a mono
pocket
> cruiser of the same length, it will probably be too slow to benifit from
the
> biplane rig.
>
> Mr. Jones reports in his book MULTIHULL VOYAGING: "...On a reach, the
leeward
> sail flopped idly about, and we were driving the boat with only half her
sail
> area..."
>
> And there was much more after that. And most of it wasn't flattering. The
only
> good thing he said about the rig was how few times he had to reef it.
>
> Its best point of sailing was dead down wind, because the two side by side
> mains could be flown wing and wing.
> Bob
> ________________________________________________________
> <http://www.boatdesign.net/forums/showpost.php?p=93221&postcount=22>
> Biplane rig
> This rig seems appealing in theory, but as Tom Jones discovered, it has
> certain drawbacks in practice. I don't think faster boats can entirely
sail
> away from the lee blanketing problems on a reach. I've read correspondence
> from a person in Thailand who built a Radical Bay (Schionning design) and
> still acknowledged that the problem occurred. They were overall very happy
> with the design, however, and felt that this inefficiency was a tradeoff
that
> could be endured to get the other advantages of the rig.
>
> One big disadvantage for a cruiser is that when the lee sail is outboard,
> there is very little deck underneath it to work at the boom, for reefing
and
> sail shape controls. A great advantage of cats in general is that you can
> stand by the boom in the middle of a wide deck and do this work in
security
> and comfort, and that is a big advantage to give up.
> Ray
> ____________________________________________________________
>
> ...and finally
>
> > Peter Nice: I designed and built W, the prototype bimaran.  It is a cat
> with
> > the rig in one hull,  not an ama less tri.  For what it is, it is an
> > interesting concept, which taken to it's logical conclusion, becomes a
> harry
> > proa.
>
> 'Nuff said. Rob
>
> Brian replied:
> Lets not confuse the 'biplane rig, with the 'bimaran'...two different
subjects
>
>
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