Sailing Theory Tutorials - Location of CE CLR and Helm Feel
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- เผยแพร่เมื่อ 31 พ.ค. 2024
- In this video, the idea that a distributed pressure force can be simplified to a single force vector acting on a force centre is introduced. It is also discussed, that two forces separated by a distance will generate a moment or torque, which causes an object to rotate.
The locations of the centres of effort, and lateral resistance are discussed in 3 dimensions on a model sailboat. And an orthographically projected diagram is drawn for the boat.
The fore and aft, as well as the side to side positions of the CE and CLR are related to the conditions of weather, lee, and neutral helm, which are explained by the two forces acting at a distance to create a moment causing the boat to either head up or bear off.
NOTE: It has come to my attention that this video fails to mention the important effect of the shape and area of the boat's hull below the waterline on the amount of Lateral Resistance and the location of the CLR. Please be aware that this is another factor that can play into the position of the CLR.
Hi Everyone,
I made some changes to my channel this winter that resulted in YT deleting all of my comments/replies on these videos. It's really a shame, because I feel like I have answered quite a few theory questions in the comments section over the years. If you have a question, even if it looks like it's been asked before, please don't hesitate to post a comment, I'll do my best to get back to you.
Cheers,
JH
No book could explain this better, thank you for such an amazing video!
Hear hear with the other positive comments, thank you for helping us. 👌
Great Video to explain sailboat balance!
excellent description with very accurate illustrations of sail boat physics..would be extremely useful if these information are compiled in a booklet
Really great pacing and effective explanations of your diagrams. Well done!
Wow. Trigonometry revisited.. well paced session. Thanks.
Amazingly clear and scientific explanation for weather helm. Thank you!
Wonderful video! Thank you for all these clear graphs and explanation!
The centre of lateral resistance is also affected be the underwater profile of the hull, not just the keel.
The underwater profile of the hull changes as the boat heels.
Absolutely, we discussed this at length is some of the deleted comments years ago. The shape of different hulls affects the location of the CLR and heeling (side to side) or even pitching the boat (fore and aft) can also move the CLR around.
Fantastic tutorial, thanks Julian!
Great vid. Nice clear thinking. Thanks
Wonderful video. Thank you very much for making this. Learned a lot.
Excellent video. Very well presented and logical. Great teacher!
Hi Julian, I'm trying to learn sailing by following through your youtube series, but I've never sailed in the water before. So thank you for putting so much work for such comphrehensive videos on such topic. Great work!! I understand most of the of material for this episode, but if you could clarify some of the elementary terms, it'll really reinforce my understanding.
1. From the 3 figures of boats to illustrate Heel and Helm Feel at about 22:36, the wind direction is blowing right to left, correct?
2. the term "windward" means "towards" the wind and leeward just opposite of windward, right?
3. does "bear off" always mean the boat turning counter-clockwise and "head up" always mean boat turning clockwise?
Thank you.
Thank you so much for this great presentation. I have some questions please. When are we going to define the CE ahead, behind or inline with the CLR? what about the side water pressure acting on the hull under the LWL (what is the reason that we focused on the centerboard/ Keel and the rudder only)? Thanking you in advance.
It seems like CLR should point forward not aft. It appears CE and CLR are exact opposites at 18:09 which means the boat would not move if CE and CLR were at same spot fore and aft or the boat would just turn in circles if they were separated.
GREAT VIDEO.
First, let me start by thanking you for putting together such a great tutorial. There are some difficult concepts presented here very well. I do have some critiques that I hope are received as helpful feedback...
1) As Vissam mentioned in another comment, the effect of resistance on the hull is not factored into your CLR estimates. This is a fairly significant oversight, IMHO, as it would likely move the CLR forward on most boats, thus contributing to weather helm.
2) Your last diagram correctly shows the port tacking vessel with a counter-clockwise moment, but then you state that it would cause the boat to bear off and would represent a lee helm. This is not the case, as the wind is coming from the port side, so that is still weather helm, and still making the boat want to head up - its just the opposite direction because the windward is in the opposite direction.
@@howarthsailing I had the exact same reaction as Steve for point 2. Not until your reply and a re-view of the video did I see that you are correct. I know that re-doing the video would be a pain, but I at least two of us mistook the information. It stands to reason that others did as well. Mentioning how a weather heel could be achieved (and avoided) as well as the effect of the hull on CLR, would enhance your efforts in educating those of us who do seek optimum understanding our crafts. Thank you. I really do appreciate your work.
the part at the end about lack of rotation for flat boats makes proas seem very OP
so Help me : in weather helm the captain gets everyone to sit on the windward rail , this helps the CLR to be more vertically in line with the CE .....I get that part .... now in weather helm the CE is aft of the CLR ,,,pulling up the daggerboard will move the clr aft , ( correct me if I am wrong ) so question is , what sail trim adjustments of jib and main would move the CE forward ? appreciate your help and thanks for this great video
How can you have a windward heeling boat in the last bit of video at 26:54? Or is this just theoretical?
you could simply put weight (like all the crew) on the windward side of the boat.
Hi, firstly, thank you for the instruction. Only at the very last part that I find at odd with. Both heeling should head up to wind, given that the case scenerio where you put the CE and CLR together for simplified explanation of the effect of heeling and the resultant moments. I may be wrong. Appreciate your reply. Thanks again for the great effort instructing.
@@howarthsailing Oh, I see. I didn't catch that. Now I understand. I was thinking in keelboat mode. Thank you so much for clarifying.
Great video, thanks. Did you get round to doing one on moving the ce/clr?
I second this request! Keen to understand that part too.
@@howarthsailing link us if you do. Cheers. Thanks for explaining...
other than weather helm, does moving the CE too far aft also cause excess heeling? I know heeling causes weather helm but But i am just curious how the affects of the CE being aft affect the performance of the boat
Hi Josh, That's sort-of a different, but related effect. Pulling in the mainsail moves the CE aft, which can cause weather helm. Pulling in the mainsail also increases the healing moment (the lateral force on the sail x the distance up from the center of rotation of the boat), which causes the boat to heel more, but that's not because of the CE being aft, it's because the forces are stronger when the sail is sheeted in further.
Thanks for the informative videos! Any chance you could share what drawing app you are using?
The old videos were recorded on my Samsung Galaxy Note 10.4 tablet and the stock SNote app was what I used. I haven't found anything that I like for annotation on my newer Microsoft surface pro.
@@howarthsailing Thanks!!!
Could you explain how the underwater slipstream affects how the boat holds it's course?
For instance, on the Lee side of the hull/fin the water is experiencing high pressure and naturally the windward underwater side of the hull and fin are experiencing low pressure.
The opposite of what is happening to the mast and sails.
I think that the other video I have called "Sailing Theory Tutorials - Forces on Sails and Foils" goes through this. Basically, the hull, keel (or centerboard as the case may be) and rudder have a flow over them, and because the boat makes a small amount of leeway as it travels through the water, there is a small angle of attack between the foils and the flow, this results in lift being generated in a direction that opposes the force of the sails.
@@howarthsailing what effect will that have on the rudder?
@@mikecritchlow1114 I don't think of it as having an effect on the rudder, more that the rudder takes some of the resistance forces, which should factor into where you consider the CLR to be. An interesting point though, is that you can stall your rudder by steering too hard, essentially, creating too large of an angle of attack at the rudder and causing flow to detach.
@@howarthsailing HS... as I see it, the streamline from the hull and fin will have a sideways effect on the rudder inducing a turn downstream... hope that makes sense.
i.e. if the boat is heeling to port, the slip stream will curve up and push against the port side of the rudder causing the boat to turn to port, or lee helm. This in turn will require the helmsman to have to keep adjusting to starboard if he/she wants to stay close hauled.
@@mikecritchlow1114 I'd say that's possible.
Most often the helm is out of balance in the other direction though, because the mainsail is often overpowering and the CE is roo far aft, so I think you'll find most helms people are used to having to fight to bear off.
Hi Julian! I learned a lot from this video. im planning to build a boat and this is one of our major issue.
The positioning of the mast and keel :D
Can you help me as soon as we finish the design?
Whoa! thanks for this!
Will look for it :D
But still. will share you our design as soon as its finished
26:07 why you drew CE toward and leeward on top right diagram? Isn't it towards starboard at an angle?
The force arrow points roughly in the same direction regardless of the heel, it's the location where it acts that changes.
@@howarthsailing hm.. can you explain? if boat is tilted right that means wind is pushing on sail also right
@@vasiliibogdan1291 We're used to seeing the boat only heel away form the wind, but it is quite possible to heel a boat against the wind using body weight or movable ballast. This is especially true in dinghy sailing. At 26:07, the sails are full from right-to-left in all 3 of the cases presented. The boat is heeling to windward, so the force on the sails is represented as a arrow from right-to left, however, because the Centre of Effort is moved to windward by the heel of the boat, there will be a steering moment that causes the boat to bear off. This condition is called "Lee Helm". If you read an advanced dinghy handling book, you'll see that it's common to heel the boat to windward to aid with bearing off, especially at a windward mark. The technique applies to small keelboats as well where body weight has a strong effect on the heel of the boat.
@@howarthsailing Thanks for your replies! Have a great day!
Is there any CLR from the hull itself? or it's only on the boards and rudder?
There is definitely a contribution of the hull. In fact this os why moving forward and backward in the boat can also affect the help. I left it out in this video but it was a topic of hot debate in the comments section years ago before they were erased.
@@howarthsailing thanks for the quick reply!
This surprised me. The video shows that, if you look in the direction from the stern, the force on the sails is to the left, but the force on the keel is to the right. Doesn't this create a moment (torque) that wants to capsize the ship????? So what, other than shifting weight by the crew, keeps the ship upright? (I always thought that the CLR force on the keel is pointing to the same side of the ship as the CE force, but I must be wrong)
Definitely creates a heeling moment (which would capsize the boat if not balanced). There is a "righting moment" which acts in the opposite direction due to crew weight, ballast (think of the keel as a pendulum) and the static and dynamic forces on the hull add to stability as well.
@@howarthsailing Yes, thank you for replying. And to add, I also realized that the center of gravity acting with the center of buoyancy, which is moving when the ship is heeling, are also creating a moment that is righting the ship, in a nice negative feedback loop.
How does mast rake affect the C/E?
If you rake the mast forward, the CE moves forward. If you rake the mast aft, the CE moves aft.
22 min heel
I do have a problem with understanding your conclusion. Perhaps you can clarify it for me and others, please! The problem is that you are referring to Lee Helm and Weather Helm on your drawings without considering that both of the boats are on opposite tacks! Therefore your conclusion on the right drawing is wrong as it is Leeward heel as the boat is on port tack and the heel is to Leeward; therefore, it is Weather Helm also! Well, I hope I explained it clearly, but need to add that scientifically, you explained this fairly clearly, but CE and its relations to the CLR while sailing is not about the boat's heel instead, it is about the position of CE versus CLR in Forward or Aft position, which will establish whether it is beneficial or not beneficial for sailing!
Hi Chris, I think you are mistaken, both ot the boats are on the same tack in the renderings (notice the direction that the sail is filled by the wind. The boat that is heeled yo windward is not being tipped by the wind, but rather by the crew weight, which might be placed on the windward side, either on purpose or by accident.
CE and CLR can move fore and aft, and side to side, and both dimensions will have effects on the helm of the boat.
@@howarthsailing Then it is not clearly stated so, and that creates confusion. Also, heel of the boat if the sails are set properly has no effect on the helm as it becomes automatically a part of the steering due to necessary and beneficial heel associated with theory of sailing in general (5-12 degrees on monohull). There is more to it but I don’t want to create debate (example; luck of CG in the presentation). Anyway, I like the animations in your presentation! 😏
@@chriskaminski4642 this was all discussed in a series of comments that got purged in 2020 by youtube. I think that the whole CE/CLR topic is re-treated in a more recent video with clearer diagrams.
Thanks for watching.
17 min. CE is ahead of CLR
Is this wrong?
Drawing “digitally” if you will, i’m curious on your age, I have to guess young? The amount of time you could save on a whiteboard for example, it is mind boggling to my age.