Incredible information, thank you so much for posting this. We'll make this required coursework for the race boat crew The models do an incredible job at picking up where The Science Behind Sailing leaves off.

@wilfdarr

2 жыл бұрын

There's an android app called "sail flow analysis" that let's you play with different adjustments, I highly recommend that. It's got some glitches so don't take it as scripture, but it's a really good start to wrap your brain around what's happening in real time.

@jamesconger8509

2 жыл бұрын

Thank you.

I simply love it!

Awesome video!

thx for the info !

Hello James, Fantastic video, well done sir!

@jamesconger8509

Жыл бұрын

Thanks!

@mr.morgan5643

Жыл бұрын

Never stop learning! Hope to be sailing soon!!

It would be interesting to compare your two foil model to a single large foil at the corrected angle and see how much bigger a single foil has to be to generate exactly the same force.

@jamesconger8509

4 ай бұрын

It has been a decade, but I remember doing that comparison for the upwind case. The result was a small advantage for the two sail configuration, on the order of 2%. I think versatility in varying wind conditions is the larger factor in why the sloop is so popular, not outright performance.

Did you take a close look at the Reynolds numbers and boundary layer conditions? Does the BL remain laminar or does it quickly go turbulent? I would hope it goes turbulent so we can get max AoA. But curious what you have found on that.

@jamesconger8509

Жыл бұрын

These are (technically) all in the turbulent regime, Re way above turbulent transition. Using the word 'laminar' a bit more loosely, like P51 people like to do, boundary layer detachment is put off for quite a while. I think you can see this in the velocity profile 2D slices. That is one of the key effects of the jib on the mainsail, delaying detachment. Pretty cool tech for something developed way back when!

Love to learn more about the backwind main. I get back winding in 15 knots but can’t trim the main in more without going above centerline. So do I ease the jib an point lower? Or live with the drag? Second question. You had the wind coming from the beam at the jib luff near deck level. But this is counter to twist in the jib which anticipates winders angles up the mast. Great videos!

@jamesconger8509

2 жыл бұрын

Thanks! On your first point, are you having this problem with the traveler all the way to windward? In any case, don't relax the jib to make the main happy. On your second point, I need to move the jib car aft to get the best jib sail shape when sailing downwind. That is particularly true when I have the whisker pole deployed.

thanks james for your really interesting and informative videos. I am a small catamaran sailor, 8m l x4m w. I am interested to know how your simulation would show the implications of a multihull underwater shape?

@jamesconger8509

2 жыл бұрын

The short answer is that I have no idea! I've spent very little time on a cat, and never even considered simulating one. Calibrating the models requires that you spend a lot of time sailing and collecting specific data to compare against predictions, so this is something I won't get to in this lifetime.

SUGGESTION: you touched every so briefly right at the end, the destination at 160 degrees using two tacks, my question is this: using a polar I understand how to get the fastest heading directly upwind and downwind, there's numerous articles on that point (follow the perpendicular of 0 or 180 to the tangent you find your "no go zones"), but what if your destination is outside the upwind and downwind "no go zone", how do I read the polar to find out what the two fastest headings should be as in your example where wing on wing combined with broad reach is the correct answer? I tried to apply the same logic as the upwind/downwind problem and ended up with really funny answers!

@jamesconger8509

2 жыл бұрын

I probably don't understand your question. If the destination is outside the "no go zone", it would seem that you just sail directly to that heading. The problem would then reduce to the best sail trim for that heading/apparent wind angle. What am I missing?

@wilfdarr

2 жыл бұрын

25:10 you say (and I agree) "So if I want to get someplace that isn't straight down wind, the fastest way to get there is to do part of the journey wing on wing and do the other part [broad reach]." If we were going straight down wind, we'd sail the "bump" on the polar at ~160° to the wind for half and then Jibe and sail the rest at ~200° to the wind (wing on wing for both). But if the destination is at 140, reading the polar, it looks like I should be steering ~120° (broad reach) to the wind to get the best VMG and then tack back at some point (wing wing), but I don't understand how to get this answer from the polar.

@jamesconger8509

2 жыл бұрын

I think you can only get one leg at a time of the polar. If yours shows wing on wing, then theoretically you would need to iterate between WoW and different broad reach angles to find the combination that has the shortest time to reach a given destination. A shortcut would be to find the broad reach wind angle on your polar that gives you the best downwind VMG, and then use that plus WoW to make up the composite course. (The published polar for my boat doesn't even show wing-on-wing, as it assumes that I would always put up the spinnaker downwind. )

@wilfdarr

2 жыл бұрын

@@jamesconger8509 I was afraid you might say something like this. I thought there might be away around it that i was missing, especially where only one wind angle is involved. I know that where multiple wind conditions are forecast navigation apps just "brute force" it, trying hundreds of routes with different sailing angles until they get to the best one.

Would it make sense to a few tell tales to where the slot is on the jib and main to ensure that air is flowing properly? My boat has a very small non-overlapping jib and because of where the clew comes in just an eyeball looks like it is hooking back in to the main. I've been curious if it is a performance issue

@wilfdarr

2 жыл бұрын

Are you saying "add more tell tales to my jib" or " add tell tales to a jib that doesn't have any"? My opinion is that sails should aways have an abundance of tell tales! Yarn doesn't significantly slow a boat down, but not understanding what the sail is doing well definitely slow you down!

@bcardarella

2 жыл бұрын

@@wilfdarr I guess more to the jib, as I have the usual ones closer to the luff. Right now I don't have a good way to visualize the flow of the slot. James' videos have really highlighted the performance benefit of getting the slot tuned

@jamesconger8509

2 жыл бұрын

I too find it difficult to really see the shape of the slot while sailing. Seems like I want to be off the windward stern about 10 feet past the rail to get the right perspective. It's wet over there!

@wilfdarr

2 жыл бұрын

@@bcardarella Don't get too hung up on "the slot", think of it more as "the air approaching the mainsail", especially if I understand you correctly and you're main is the driving sail, then the jib is really there more to turn and smooth the air in approach to the main. As for telltale on the leech, Quantum says "Telltales can be used on the leech to indicate flow on a non-overlapping jib. As usual, it is the top telltale that counts. Usually there is only a single telltale in the upper 25% of the leech. Trim too hard or pull the lead too far down (or too far forward) for conditions and that telltale will stall. Twist is essential in a non-overlapping sail so you always want the telltale flying."

"The simulation suggests that... it's optimum to have more curvature on the sails as you let the sails out... but with my mainsail I've got full battons and no matter what I do the sail just doesn't bent that much, so it's not optimum..." Absolutely true, but I'd point out that Though it's not optimum for beam reach sailing, the battons ARE optimized for upwind sailing, which is the worst kind of sailing. Most people don't want to spend all day beating too windward and are therefore OK sacrificing a knot or two on the reach or downwind to get better performance on the upwind.

@jamesconger8509

2 жыл бұрын

You are completely right. In general the jib and mainsail design is driven by the close hauled case, which is the most critical. You don't give up much performance using those same sails off the wind. I just found it interesting to see what the "perfect" sail shape would be in all cases.