Discussion in 'Smaller Boats' started by Jim Loats, Feb 27, 2018.
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I think it was from an on-line version of one of David Dellenbaugh's 'Speed & Smarts' articles.
I see what Will is saying.. He is saying that if two different boats can only point as high as 45 Apparent, their VMG angle .. assume same wind speed and direction..one boat sails 10 kts at that apparent wind angle the other boat sails at 6 kts at that apparent .. The slower one will have a different heading to achieve 45 degrees apparent than the faster one and its heading will be slightly "higher" .. I haven't done the vector math, but I think that is what would happen.. The thing is that in real life, having both with same VMG angles is not probable..
What a treat! The Good Doctor and Jackdaw explaining sail angles w/ great graphics.
I wasn't looking to get caught up in yet another fight about sailing theory. I really appreciate everyone's involvement, though and if you all are willing to indulge me, I'll happily try to clarify what I was talking about. Really, I don't think we are in disagreement about anything regarding theory. Mostly, I was talking pointing angle in apparent wind verses true wind. My thoughts had nothing to do with optimising speed.
The OP was asking about his ability to point into the wind verses his opponents. He was in a race but his question was about angle not speed, as he asked it
Someone else suggested that a fouled bottom would slow him down and that would make it more difficult to point higher. I don't happen to believe that is true. Of course it would slow the boat down, but it wouldn't make it harder to point higher. In fact, a boat's speed thru the water, air really, is going to have a vector effect on the angles of true versus apparent wind. If true wind, for example, were directly on the beam (90 deg to heading) and the boat moved forward, as one would while sailing, then there appears a second vector component to the wind angle across the deck (apparent wind). This second component is solely speed reliant and becomes an additive vector of head wind to the true wind such that the apparent wind moves forward of the beam. To anyone standing on deck, in the wind, they would feel the wind starting to come from the forward quarter, no longer directly on the beam (true wind is still 90 deg from heading) . The faster the boat goes, the more forward the apparent wind becomes. If, for example, the true wind was twenty knots on the beam and the boat was making 15 knots on her heading of 90 deg to the true wind, that equals 25 knots apparent wind coming from about 30 deg angle forward of true wind. This example is just a 3-4-5 right triangle of vectors. The faster boat would experience a greater angle, the slower boat, a lesser angle. I know 15 knots is not a reasonable boat speed for a 25 foot displacement hull, but it illustrates my point.
Here's where my argument really began: someone said, "You can't point as high as the same boat if you are slower." I could be wrong in this, but that just doesn't work that way with the vector addition. A boat has a limit to how high it can point. There is a maximum angle to windward before the sails will just not hold their shape and lift is lost. This angle is an apparent wind angle. The angle of the wind across the deck. Between two boats, otherwise the same, the faster boat will reach that maximum angle sooner because of the greater apparent wind change, than a slower boat.
If you want to go faster, clean the bottom, lighten the boat, trim good sails effectively, improve ballast to stand up straighter. If you aren't pointing high enough, trim good sails effectively, balance the helm, improve your heel angle with better weight distribution. I'm sure there are other things like leading edge turbulence, but going faster isn't going to enable you to point higher.
I'm sorry if my communication skills are failing here. I know Jackdaw and DrJudy know what they are talking about, certainly a lot more than I do. It just feels like nobody seems to know what I'm talking about.
Oh well. It's still great fun to be involved.
- Will (Dragonfly)
I know that's what he is saying, I said so in my previous post.
My point is that the effect of boat speed on upwind angles in real-life sailing is not a practical consideration. Between a fast 25 footer going 5.5 knots to windward and a slow boat going 5.0, the difference in Apparent Wind Angle cause by the speed change is less than a degree.
we love you Will, keep contributing dude. sharing makes us all think
Well, except for kloudie.
Thanks kloudie. And thanks jon. I know you guys got my back.
- Will (Dragonfly)
Will, your point and your math have had me thinking all day about how to simplify the explanation, so don't beat yourself up about your communication skills.
I think the point is that the exercise is about how to get to the upwind mark (or make the best VMG upwind) which makes the angle irrelevant....even if your original explanation is valid. In real terms, for any boat pointing up wind there is probably only one best angle for each set of variables that results in maximum VMG despite the fact that you can point higher if you go slower, just as you can go faster if you go lower. We didn't even get into the better underwater surface lift from greater speed through the water as a variable.
In the end, I think there are really two different discussions rather than an argument. I have enjoyed the exercise of thinking it through so thanks everybody.
@kloudiel1: I see what you're saying about true wind angles. The math works the way you say it does, but I would analyse the scenario differently and come to a different conclusion that's more useful, I think.
First of all, let's clarify that the apparent wind angle is NOT equivalent to the true wind angle for Max VMG upwind. The two are quite separate and distinct. Maybe that's a typo or you forgot part of the sentence?
I'll do the math for you
But before we continue, let's change the AWA to 30 degrees in your example, to be more realistic. The average cruising boat can sail 28 degrees AWA or higher without pinching. Pinching is defined loosely as "sailing too close to the wind, almost stalling the sail, and therefore sailing too slow with a lot of leeway"
Both boats are sailing at 30 degrees apparent wind angle, in 12 knots of true wind speed.
Boat C is sailing at 6 knots of boatspeed through the water. The true wind angle is TWA= 44.5 degrees and the VMG upwind to the destination is 4.28 kts. We don't know if this is their optimal VMG to windward, but it's probably pretty close.
Boat D is sailing at 10 knots of boatspeed through the water. The TWA = 54.6 Degrees and the VMG upwind is 5.79.
They probably aren't making the best progress to windward that they could. They will get to the upwind destination faster if they trimmed tighter and headed up to around TWA of 45 degrees, whilst keeping the AWA at 30 degrees. That would be sailing faster to the upwind destination, and they would be saing closer to their Max VMG.
In this example, I would guess that practical "take home message" is that the fast boat is sailing low and slow to get the same AWA as the slow boat. The fast boat is capable of pointing higher, even if it goes a little bit slower through the water, whilst getting to the windward destination sooner.
Jumping right in here, your question went completely ignored and I happen to have an opinion. NOOOO! The fact that it is a CB should make no difference to the pointing ability of the boat. CB boats don't typically have the same righting moment as fixed keel boats and standing up straighter makes a difference. CBs have an advantage, however. They can change the center of lateral resistance and balance the helm under more types of sail, when well designed and used right. They also have the advantage of reducing wetted surface on the downwind runs by retracting where a fixed keel can't.
In a race between the one-designs of fixed keel or CB, such as the mariners, it is my understanding that CBs are given less handicap, if I have that concept right, than the fixed keel boats. They are lighter and definitely have the downwind advantage.
In higher winds, the fixed keel is stiffer and therefore, more efficient, but that doesn't have to be true
However, there is no inherent issue with pointing with a CB.
- Will (Dragonfly)
OK, time to clean up some more misconceptions.
First, a clean bottom will absolutely help the boat point better. Water will stay attached to the foils better, that generates more lift, better pointing.
Second the type/shape of the keel absolutely effects pointing. Efficient, high aspect foils generate more lift. An already fast First 36.7 shoal draft (6 feet) is 9 seconds/mile slower than a deep keel (7.25 feet) version. That’s all about the keel, and upwind ability.
Third, in particular when talking about racing, pointing is just as much about speed as it is angle. The name of the game is VMG. My boat can sail into 30 degrees true wind, it’s just not as fast.
For clarity sake, does your H26 have a keel/centerboard configuration or a swing keel? These are often used interchangably but are two different things. Keel/centerboard means a shallow fixed keel with a lightweight centerboard while a swing keel is a heavy keel that is raised and lowered with a cable and winch. I think the swing keel configuration would point better in general. What is your beam?
I was sort of looking at the H26 for a future boat but it wasnt because the boat is a rocket ship.. Lots of theory here but Im curious about how well the H26 is going to do even if sailed perfectly. The OP said the sails are original which would mean they are about 20 years old. That boat has no traveler so you can not center the boom for upwind and it also has no backstay which I find also useful for upwind.
I sailed only one time on a friends boat (Capri 25) racing at Chatsfield Colorado and it was a mix including a Merrit 25, some Capri 25's, J24, J22, Ultimate 20.. etc. Ie, a lot of the boats that were racing there were just going to point fairly well. And of course everything that was faster is harder to launch and way less comfortable. I dont own a H26 but I am wondering from people who do, is the issue here simply 20 year old sails, no traveler etc and a boat designed more for comfort, easy launch and trailering?
Hey Walt, you bring up a a great and valid point.
I’m going to assume that the OP cannot get his boat to sail to its PHRF rating. If he was he would be doing OK in races and unlikely to post. Because a j/24 will torch it upwind, but if well sailed the h26 should be able to come close corrected.
The trick is, 90% of the times I see cases like this, it’s due to the boat simply be outsailed. Racing is a hard taskmaster.
Walt, why do you find the backstay useful for going up wind? Is that a sail form thing, bending the mast to pull the luff out, or something more?
- Will (Dragonfly)
I have an old 1990 Mac 26S with a 3/4 fractional rig and I find that I can use the adjustable backstay tension to keep the main sail flow better attached especially upwind and in higher winds. I am watching this on the tell tails that are just aft of the mast and maybe 3/4 up from the bottom and I seem to be able to influence them better flowing straight back with the backstay among other things. My main is now about 10 years old and has been used a fair amount every year so I think I may be also compensating for a somewhat worn out main. Just my observation and could be off.
Before I run up the white flag on the speed/pointing issue I will say that from my real experience driving sailboats is that you cannot simply point the bow at a pointing angle to the wind, trim the sails in, and expect to go in a point mode. Vector this or vector that but if you want a boat to point you have to first develop boat speed. Pinching is a whole other topic.
Anyway the question wasn't how to sail the best VMG upwind - although that is a great discussion. It was why doesn't my boat point with the rest of the fleet. I will add to my original suggestions for a clean bottom and good sails, a serious diet plan for the boat to lighten it as much as practical (For casual racing) and to an impractical amount when seriously racing. For me those are the 3 R's of boat speed. If you are inclined to sail slow so that you can point better, you might enjoy a race on a Cape Dory 25 with my very good friend who over stands lay lines to "Set up a nice reach."
Sorry about the bitchiness. I enjoy these threads even when they expose weaknesses in my opinions.
- Will (Dragonfly)
I don't normally chime in when such experts like Jack, Judy et al. speak...
But the OP mentioned Hunter boats.
What I have noticed is the same thing on my Hunter, but @Crazy Dave Condon might know more about Hunter's pointing.
I thought it is the Mast Position relative to Center of Mass of Hunters. [more cruiser than racer]
Different than 8 Model boats I have sailed...
When pointing, my Hunter, it tends to nose down and thus rudder up.[OEM sail area]
I find that pointing slightly off wind does improve VMG.
PS: We bought our boat for mainly cruising, but I am PHRF registered.
Come flying in. Like a BOSS.
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