Cool video, thanks! I am working on a design for a 36 ft catamaran with two carbon spar tacking crabclaw claw sails. I believe in their efficiency but couldn't live with shunting.
@markpalmquist
3 жыл бұрын
Tacking is easier than shunting, I agree.
@markaridgway
3 жыл бұрын
One of the most unscientific experiments I've seen.. but entertaining. Thanks.
@erefayn6492
2 ай бұрын
The experimental constant was chosen incorrectly. If you want to compare sailing performance, the experimental constant should be the bare hull. In this experiment, the bermuda sail could easily have 2 times more sail area, but this was kept limited. The main advantage of the Bermuda sail is that it provides more sail area for the same ship. When you repeat the experiment with the largest sails they can both take, it won't be surprising why the bermuda is the most popular.
@markpalmquist
2 ай бұрын
It is what it is. I agree Bermuda is better but I was doing this test before building a small sailboat that would only have 1 sail and 1 crew. I have since learned that testing with scale models is extremely hard to produce accurate results.
@EscapeePrisoner
3 жыл бұрын
Now that is interesting. Thank you for going to the effort of doing that.
@markpalmquist
3 жыл бұрын
Thanks! I tried a fluid dynamics modeling software and it was too complicated, so I am sticking with something that I know how to do which is make scale models and run multiple tests. You can learn a lot from a scale model if you only have 1 variable.
@harveylorenzedejesus2383
Ай бұрын
Hey mark, for a crab sail to perform better than a bermuda sail, you have to make sure that the leading edge is 30* sharp (the more vertical the less thrust) the sail should occupy the entire length of the boat, also the sail must not have any camber or conical shape. (the flatter the better) Crab sail produces thrust the same way delta wings produces thrust. I'm telling you this because I also thought crab sails should be oriented vertically. I pirated research papers as well as academic books about sails/sailing (that's where I learned all that).
@markpalmquist
Ай бұрын
I always thought it was a combination of lift and dual swirling vortices, no just 1 or the other. Did you read Marchaj?
@harveylorenzedejesus2383
Ай бұрын
@@markpalmquist I did, and read some other russian and norwegian guy that based their research off of his.
@markpalmquist
Ай бұрын
@@harveylorenzedejesus2383 I have not tried the configuration that you are describing but it is probably worth testing. One thing to note, a bermuda rig will point higher but on beam reach the crab claw is quite comparable.
@kevinhutchinson1835
2 жыл бұрын
10 years ago I tested the crab claw against a lug sail .I used an old sunfish as my test hull. I made a lug sail and crab claw with identical sail areas. I then I sailed the same sunfish through a coarse three times using each sail. I checked windward ability and speed. Results were the crab claw was considerably worse in speed and especially windward ability than the lug. In fact with the lug sail I was usually a full knot faster . Unfortunate I have no photos or videos to show my results. The crab claw does not form a airfoil shape except perhaps longitudinally. Therefore it can never sail very well..it sure is cool looking I admit!
@markpalmquist
2 жыл бұрын
I have not tried a lug sail. I agree that the crab claw does not point as well. My boats were sailing on a beam reach. Regarding the airfoil shape I agree the crab claw does not have an airfoil shape however they work by creating dual spinning vortices along the leeward edges similar to a delta shaped paper airplane. Paper airplanes are flat, no curvature. So there are 2 ways to generate low pressure. The Bermuda rig is better tight to wind but worse downwind, that’s why they require a kite down wind.
@markpalmquist
2 жыл бұрын
We also have 2 sunfish sailboats. Maybe I will repeat your experiment and race my wife using 2 different sail rigs. She is a sunfish racing champion so she will have an advantage either way over me. I spent 90% of my time sailing windsurfers and 10% on a beach cat. I've only sailed our sunfish 3 times so far.
@OkieBobby
10 ай бұрын
Mark, I enjoyed the experiment. Thanks for sharing! You must have dialed in things well to get both to cross the pond. Wish I could dial in my real boats that well.
@markpalmquist
10 ай бұрын
Thanks! It's nice to have the ability to shift either the sail or the dagger board slightly to find the perfect balance. It's easier with scale models sometimes.
@markandoyo2204
8 ай бұрын
As yet that clarifies these small-scale experiments can ratifies full-scale concept directions as only thing with full-scale nuances were regarding about the retraction logistics but I see here a full-scale small-craft can be practically Crab-rig sails with outrigger boats which having naturally Keel displacements and yet it is fundamentally works under the lowprofile sail materials and yet non-graded small sail area but it is practically workable in the Visayas Philippines as yet Paraw Sailor inspired these concept under the non-mathematical graded Regatta setup👍
@FlatlandMando
3 жыл бұрын
Kind of a wacky experiment. Public pond instead of an expensive wave tank for testing...a guy wants to know these things if pursuing design issues...
@markpalmquist
3 жыл бұрын
I don't have access to a water tank. My models were identical except for the rig. It is quite possible that I did not have the slot positioned correctly, or that the diameter of the mast was too large. I tried improving the slot and it never beat the crab claw, at least not on this scale. It is quite possible that on a larger scale, the physics is different.
@FlatlandMando
3 жыл бұрын
@@markpalmquist Excellent. Thanks for adding more detail
@bobcornwell403
3 жыл бұрын
The 'crab claw' has the bigger portion of its Sail Area higher up than the sloop. This does not mean it necessarily has a higher Center of Area, but that it's Sail Area is more concetrated higher up than that of the sloop. Also, the sloop has a metal main sail which is bent at an angle instead of formed into an airfoil cross section. To make this a fair comparison, the crab-claw sail would need to be formed in the same manner.
@markpalmquist
3 жыл бұрын
I tried improving the sloop sail shape a few times with the same results. It could be that my sloop mast was too thick but I made sure it was attached to the windward side not the leeward. I am not claiming the crab claw is better than the sloop in all cases just in this case with 2 boats sailing across the wind on a boat that has no adjustable sheets. I also tried opening up the sloop sail a bit and it never beat the crab claw. More testing at a larger scale and with cloth sails may give different results.
@onanysundrymule3144
3 жыл бұрын
Excellent work Sir.
@Antipodean33
Жыл бұрын
No ballast also lets see a sloop rig and a crab claw compete beating into a hard blow and steep chop. On a proper sized yacht a crab claw would lose to a sloop rig on every point of sail I'd gamble on that
@markpalmquist
Жыл бұрын
If you keep the sail area the same then the crab claw will win on all points of sail off 40 degrees to the wind. So yes, Bermuda points better but to compete off wind you need to add a spinnaker.
@burkk4166
2 жыл бұрын
Mark, can you try the crab claw in a more vertical position instead of mounted at an angle. I think you will find this provides a higher aspect ratio and its upwind performance will improve... anyway an idea
@markpalmquist
2 жыл бұрын
I agree
@kenwebster5053
2 жыл бұрын
There are a lot of complexities to sailing which you clearly have no idea about. Perhaps read Frank Bethwaites high performance sailing to find out how sloop rigs actually work. The crab claw rig generally cannot point as high upwind as a sloop rig. However it is very fast off the wind most particularly because it provides more sail camber off wind, generating higher force for area which also has a lifting component as well. So, the crab claw is ideal for ocean voyaging on the trade winds, but not so great tacking into headwinds. Basically, there are advantages and disadvantages to both rigs & sails are flexible responsive membranes that require tuning to exploit their true potential.
@markpalmquist
2 жыл бұрын
I agree with you. I also have Frank Bethwaites book along with 2 books by Marchaj. I ran the experiment out of personal curiosity. The results speak for themselves. I agree the crab claw is better on a beam reach and running. The sloop is better at pointing. Boats that travel at high speeds should have a sloop rig, boats that do not can have a crab claw or lug.
@kenwebster5053
2 жыл бұрын
@@markpalmquist OK then, my mistake. I didn't understand your conclusion because it seemed to me that the sloop mostly just spun about going nowhere. I thought that was a helm balance issue with the model & inconclusive of performance.
@markpalmquist
2 жыл бұрын
@@kenwebster5053 if I could run the experiment again I would move the sloop rig 10% forward. Of course I learned an important lesson that different rigs will create different levels of rotation to windward (weather helm) even if they have the same area.
@doyouwanttogivemelekiss3097
2 жыл бұрын
@@markpalmquist instead of moving the rig (or the rudder/fin) to compensate for the weather helm, you could you install a servo and helm yourself via r/c 😅
@jamesaron1967
Жыл бұрын
Interesting experiment but the scale of the test boats is too small. I doubt the same aerodynamic effects are experienced at this scale that occur with full-size sailboats, even if everything else was reproduced accurately. For example, the aerodynamics of small flying insects is very different from that of birds.
@markpalmquist
Жыл бұрын
I agree, the scale has some effect. Also, these were sailing mostly on a beam reach in which the crab claw does well at. A close hulled course would favor the Bermuda sloop.
@jamesaron1967
Жыл бұрын
@@markpalmquist True, but I'll admit I was hoping for the crab claw to be faster ; )
@mboyer68
2 жыл бұрын
Tube sailoats?
@bunyipdan
3 жыл бұрын
Cool......have you considered the Romy Rig (sort of a boomless lateen Rig) instead of the crab claw
@johnstarkie9948
3 жыл бұрын
The lateen is boomless. If it has a boom, it’s not a lateen.
@bunyipdan
3 жыл бұрын
@@johnstarkie9948 Yes John......you are technically correct, I guess including 'boomless' in my description was a bit redundant.....however in my defence, I was using it more to emphasise the difference between the crab claw and describe a little known lateen style 'boomless' rig - the Romy, my apologies for any confusion.
@johnstarkie9948
3 жыл бұрын
@@bunyipdan I understand; no problem. Again, to be pedantic, the crab-claw has no boom. The two spars have equal status in holding the sail open and, if you read Tony Marchaj, the axis of the wind should pass along an imaginary line halfway between the two spars so that the vortices roll equally from both. This is what makes the crab-claw so powerful, and so fundamentally different from all other sails except, perhaps, the lateen. Tony Marchaj analysed the lateen as being half a crab-claw; The wind flows along the foot of the sail and flows from the yard as rolling vortices.
@johnstarkie9948
3 жыл бұрын
@@bunyipdan The Romy is interesting in being a lateen with a twin, or double, mast. It is capable of being tacked much more easily than a traditional lateen with a spar or pole mast, but I imagine that the two masts would inhibit downwind sailing.
@bunyipdan
3 жыл бұрын
@@johnstarkie9948 as to your previous comment.......yes John you are correct again 'spars' ...... I'm not particularly interested in the 'technically correct terminology', my comment was simply a question regarding a different option other than Bermudian and Crab claw rigged sails, again my apologies if the original very short comment has triggered some sort of need to correct a rather innocent interaction (I was not claiming any sort of superior knowledge on sailing terminology just attempting to communicate an idea). As for downwind performance of a Romy rig, yes, as with all things there are compromises, I think if one desperately wanted to increase the downwind performance potential of a Romy rig ...... then you could consider double 'skinning' (not a technical term) with independent clews, so you could separate the sail to form a 'butterfly'/'goose wing' type arrangement. I think the biggest hurdle for the Romy rig design is reducing sail area (reefing).....but that is a whole other discussion.
Пікірлер: 49