I Love to Eat Crab Claws - Here's Another Reason to Love them

Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
Another great feature of the crab claw, the simplicity and ease of working.

Moving right along:

-Will (Dragonfly)
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
This is a fantastic Website about rigging a crab claw: http://econscience.org/tiki/2016/05/04/crab-claw-sails-the-mast-to-tack-connection/
Here, the author discusses the advantages of connecting the tack at the base/aft of the mast
instead of, like the sailfish, to one side with the tack forward.

While there are other answers to the problem of interrupted airflow by a mast deforming the sail on one tack or the other, the aft tack connection is a simple solution.

This next site is a brief analysis of some wind tunnel tests done with the crab claw sail. The change in orientation (angle) of the sail's line of symmetry as well as the hauling of the boom to the boat's centerline, makes for more versatile trim options in various winds and points of sail. http://econscience.org/tiki/2016/05/12/bernard-slotbooms-windtunnel-tests-of-the-crab-claw-sail/


-Will (Dragonfly)
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
@rgranger,
I just came across this picture while looking up something completely unrelated. Thought you would appreciate it most of all.

Not a crab claw rig, but you described a version of this, I think.

- Will (Dragonfly)
 
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Jan 19, 2010
12,553
Hobie 16 & Rhodes 22 Skeeter Charleston
@rgranger,
I just came across this picture while looking up something completely unrelated. Thought you would appreciate it most of all.

Not a crab claw rig, but you described a version of this, I think.

- Will (Dragonfly)
Amazing!


Thanks,
 
Jan 19, 2010
12,553
Hobie 16 & Rhodes 22 Skeeter Charleston
I wonder why he has his sail on the windward side of the mast. That is generally considered the less efficient tack for that type of sail.

But that sail looked well trimmed
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
I wonder why he has his sail on the windward side of the mast. That is generally considered the less efficient tack for that type of sail.
No. I don't see that. Did you see him tack around the buoy? He changes directions by moving the tack from one end to the other. Sail is on the leeward side the whole time.

-Will (Dragonfly)
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,820
CAL 35 Cruiser #21 moored EVERETT WA
Did you see him tack around the buoy?
What I saw, he did not really tack around the bouy. He went beyond it then moved the sail and went in the opposite direction over the top of the bouy. The sail moves along one side of the boat. From bow to stern. Wind stays on the same side of the boat. The stern now becomes the bow and he heads back in the direction he came from. Not sure of his method for steering his craft but guess it is a paddle. The sail stays attached to one side. Appears stable. Suspect it is a mono hull with an ama.
 
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Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
Suspect it is a mono hull with an ama.
The hull looks a look like a Mad River canoe, to me.
And yes, he never turned through the wind. Just switched bow and stern.
"Hand me my jacket, I left it in the stern. Hey! How'd it get to the bow?"

He did run over the buoy, didn't he?

-Will (Dragonfly)
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
I can't see any steering paddle, oar or rudder. You don't suppose he steers with weight and sail trim?

-Will (Dragonfly)
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,820
CAL 35 Cruiser #21 moored EVERETT WA
No. Not enough control. Unless he is really Crash Gorden in native costume then all bets are off.
Just look a Moana... She steered across an ocean to Tahiti...
 
Jan 19, 2010
12,553
Hobie 16 & Rhodes 22 Skeeter Charleston
What I saw, he did not really tack around the bouy. He went beyond it then moved the sail and went in the opposite direction over the top of the bouy. The sail moves along one side of the boat. From bow to stern. Wind stays on the same side of the boat. The stern now becomes the bow and he heads back in the direction he came from. Not sure of his method for steering his craft but guess it is a paddle. The sail stays attached to one side. Appears stable. Suspect it is a mono hull with an ama.
This type of tacking is called shunting... but look again. The sail is in front of the mast and to the windward side of the mast. On most proas the crab claw sail is behind the mast (on the leeward side of the mast). I have several books on proa designs and have purchased the plans to one called the wa'apa. It looks like it would be a tone of fun to sail. My daughter and I also built a strip planked canoe two summers ago... so I have it in the back of my mind to build a working proa someday. Just need time and space. Right now I have no time...:(
 
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Likes: Will Gilmore
Jan 19, 2010
12,553
Hobie 16 & Rhodes 22 Skeeter Charleston
Don't misunderstand, I'm not being critical. It is just curious to me. This one seems to sail just fine.
 
Oct 19, 2017
7,946
O'Day Mariner 19 Littleton, NH
look again. The sail is in front of the mast and to the windward side of the mast.
I'm afraid I don't see that at all.
It looks to me like the mast is stepped midship or even on the pontoon side of the canoe-like hull. The tack of the sail is fast to the bow, ahead of the mast in relationship to the boat. However, the sail's camber curves out on the leeward side of the mast. No part of the sail is too windward, that I see. Are you using different reference points? Maybe we are not talking about the same thing. The wind is coming across the pontoon before meeting the sail.

-Will (Dragonfly)
 

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,820
CAL 35 Cruiser #21 moored EVERETT WA
@rgranger I can see how you might reach that conclusion. I think it is an illusion based not he way the light is hitting the sail. Look not at the sail but at the water. The camera is positioned so that the boat is upwind of the camera (look at the waves). And is therefore reaching left and right in front of the camera. This puts the sail down wind from the Mast (which is hidden behind the sail).

Not sure how close tot he wind this boat can sail. It looks pretty good at 90 degrees to the wind and down wind, but It appear to be weak at sailing up wind. Perhaps the skipper would need to wait until the wind was going in a favorable direction before venturing out on the water. It does look like fund.