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Old 08-10-2011, 10:14   #1
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The A-Fame 'Mast'

Inverted V attached to sides of boat, supporting stays that hold the sails. In fact, a vertical stay to apex of V to which sail luff is attached, could be moved at deck attachment point to cant sail into wind, just like a windsurfer.

By the way, I just patented that concept...see

SAILFAST
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Old 08-10-2011, 10:47   #2
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Re: The "A" frame "mast"

Quote:
Originally Posted by rpeebles View Post
Inverted V attached to sides of boat, supporting stays that hold the sails. In fact, a vertical stay to apex of V to which sail luff is attached, could be moved at deck attachment point to cant sail into wind, just like a windsurfer.

By the way, I just patented that concept...see

SAILFAST
It's been done before. Theres been a boat with that concept in Shilshole marina for 20 years. Maybe didnt have the canting mechanism though...
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Old 08-10-2011, 12:33   #3
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Re: The "A" frame "mast"

The best example of the A-frame mast I have see is Procyon, the famous 65 Windship. It came with a wishbone boom like on a windsurfer. The rig did not cant although the keel did. The rig got a bad reputation when it fell over dockside on a gusty day. It is still hard to say what the Harken brothers were smoking when they came up the design. They sure made a unique yacht. Best of luck with yours.

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Old 08-10-2011, 13:05   #4
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Re: The "A" frame "mast"

Sorry to dissapoint you but Greenpeace is building a boat with a few of these masts as we speak...

BBC News - Rainbow Warrior and the launch of direct green action
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Old 08-10-2011, 13:54   #5
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Re: The "A" frame "mast"

Curious, if other boats as shown or referred to in three posts above already exist, what did you patent?
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Old 08-10-2011, 14:34   #6
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Re: The "A" frame "mast"

Seen this rig twice. Imagine plenty of drag, plenty. And a heavy rig. The jib cannot be flown between the arms due to the spreaders. This leaves you with max 100% jib or else very wide sheeting angles. The main works in very dirty air anywhere from beating to beam reach.

Alas, in cruising aspect and on a cat, I would give it a try, especially if the masts were carbon and the spreaders could be omitted. (???)

What I like very much about this set up is the main can be reefed just like a jib - furled to any size you like with a regular furler.

Wondering if with today's technology we could built the frames stiff enough to avoid the spreaders.

?

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Old 09-10-2011, 09:15   #7
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Re: The A-Fame 'Mast'

The A-Frame design was first conjured up in the 1950's as a possible solution to the effects of a mast on the flow of air over the main sail which, in reaching conditions, creates a large "dead zone" on the leeward side of the sail aft of the mast. The idea was to create a system that allowed the luff of the main to behave in the same manner as the luff of the jib giving greater effective area on the sail before the leeward flow separates from the sail. The system worked but the rigging is complicated and difficult to tune and more labor intensive than most recreational sailors are prepared for and could not be commercialized economically. Moreover, a slight over-lap between the head-sail and the main and the resulting "slot effect" mitigates, to some extent, the dead-zone/separation issue on the main. See C.A. Marchaj "Sailing Theory and Practice" for more details.

FWIW...
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Old 09-10-2011, 15:04   #8
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Re: The A-Fame 'Mast'

An additional advantage is that the stays are not trying their best to push the mast through the hull, especially when sail is loaded. A frame on catamaran could carry floats part way up to provide a small chance of righting in a knock over.
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Old 09-10-2011, 15:07   #9
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Re: The A-Fame 'Mast'

Regarding the jib, it flies just fine off a forestay, just as if you have a mast holding the forestay.
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Old 09-10-2011, 17:39   #10
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Quote:
Originally Posted by rpeebles View Post
Inverted V attached to sides of boat, supporting stays that hold the sails. In fact, a vertical stay to apex of V to which sail luff is attached, could be moved at deck attachment point to cant sail into wind, just like a windsurfer.

By the way, I just patented that concept...see

SAILFAST
Do you mean something like this idea patented by Chris White?
WishBone Sailing Rig - Page 5 - Boat Design Forums

Tilting Rig Catamaran Design by Chris White
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Old 09-10-2011, 18:00   #11
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Re: The A-Fame 'Mast'

Patents are a dime a dozen, it's defense of patents that are expensive and have meaning.
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Old 09-10-2011, 19:55   #12
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Procyon...a BOLD experiment

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The best example of the A-frame mast I have see is Procyon, the famous 65 Windship. It came with a wishbone boom like on a windsurfer. The rig did not cant although the keel did. The rig got a bad reputation when it fell over dockside on a gusty day. It is still hard to say what the Harken brothers were smoking when they came up the design. They sure made a unique yacht. Best of luck with yours.

I don't think they were 'smoking' anything, but rather were bold enough to go outside the box with their thinking.

Procyon...a BOLD experiment
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Old 09-10-2011, 20:26   #13
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Quote:
Originally Posted by svHyLyte View Post
The A-Frame design was first conjured up in the 1950's as a possible solution to the effects of a mast on the flow of air over the main sail which, in reaching conditions, creates a large "dead zone" on the leeward side of the sail aft of the mast. The idea was to create a system that allowed the luff of the main to behave in the same manner as the luff of the jib giving greater effective area on the sail before the leeward flow separates from the sail. The system worked but the rigging is complicated and difficult to tune and more labor intensive than most recreational sailors are prepared for and could not be commercialized economically. Moreover, a slight over-lap between the head-sail and the main and the resulting "slot effect" mitigates, to some extent, the dead-zone/separation issue on the main. See C.A. Marchaj "Sailing Theory and Practice" for more details.

FWIW...
This one worked out pretty good.
Sail the difference
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Old 09-10-2011, 21:15   #14
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A-frame Rig on 63' Cat

More out-of-the-box thinking:

Somehow I missed ever seeing or knowing of this vessel, but here is a gentleman who is not affraid to experiement. Just happened across this vessel this afternoon. Perhaps we'll encourage the owner to add some comments to this forum.

DAMSL — Catbird Suite

The rig was completed in December, 2006. It works very well, is quite efficient upwind, is especially good reaching and running, and is easy to handle because all sails furl and there are other advantages as well........."[/I]


After I posted this reference to this vessel I made a hard copy of his 'Explaination of the A-frame Rig', and reread it several times. It is quite interesting. He makes a good argument for his configuration:
1) that allows for variable tack (sail) locations across the beam of the vessel
2) that might well be called a cutter arrangement
3) all roller-furling sails with no mast interference with leading edge of sails
I thought it deserved being printed out here,...or you could go to his website and see it along with the photos.
http://www.damsl.com/
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Old 09-10-2011, 21:45   #15
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Re: The A-Fame 'Mast'

Quote:
Originally Posted by rpeebles View Post
Inverted V attached to sides of boat, supporting stays that hold the sails. In fact, a vertical stay to apex of V to which sail luff is attached, could be moved at deck attachment point to cant sail into wind, just like a windsurfer.

By the way, I just patented that concept...see

SAILFAST
Wth,
Not sure what you just said, it looks like English but....must be over my head. Maybe a little intro might help. I guess good luck with the patent.
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