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Overlapped sail area per crew on rail?


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Hi folks,  

Is there is a back of the envelope calculation for overlapped sail area vs crew weight?  My 70s racing boat was designed for 8 on the rail, and I cruise double or singlehanded.  In over 12 we are on our ear compared to our prior cruising boat so I sail with a 100% jib and it works great. 

 But I am curious about the math.  Does 180 lbs of rail meat per crew equal roughly  X square feet of power in overlapped Genoa?  If I wanted to fine tune this boat for racing short handed, can I calculate roughly how large a headsail to stay even em with fully crewed boats in medium air.  
 

Mainsail area is staying the same.  The smaller headsail has not affected helm much.  If anything it’s a bit more neutral where I would think I should have more weather helm, but I don’t. 

Ranger 37 is the boat. 

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Obviously,  a VPP could do this. 

With a little digging, you can find the force on one sq ft of sail area at a given wind velocity. Then you have the simple relationship: 

Sail force times height above waterline = crew weight times beam.

 

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Ok so let me try to do the math and completely screw this up….

Looking it up I see in some old graph I found I see that at 14 knots breeze the pressure on a sail is is about  1 lb per sf.  

With a 43 foot Luff length on my mainsail and a center of effort on the sail roughly 1/3 of the way up (read that somewhere) that gives me about 14 feet from boom to the center of effort of the mainsail.   Add about 7 feet height from the bottom of sail (boom) to the waterline (my best guess) that’s makes a 21 foot lever for the sail. 

if I remove 50sf of sail…

Force removed = 21 feet x 50 lbs  = a 1050 lbs of force removed 

1050 lbs force divided by a 5.5 foot lever arm (measured from the mast to the rail) = about 190 lbs 

So a 50 sf reduced sail area roughly allows the same heel at 14 knots as with the original full sail area with one more grown man on the rail because the force is the same?

Can it be that simple? 

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1 hour ago, beezer said:

Can it be that simple? 

It's bit more complex than that, because when you reef that main you also lower its centre of effort.   So if the first reef on your main say 4 foot deep, you lower the centre of effort by 2 feet. That's a bonus you haven't factored in.

And in lighter winds, there may be a significant difference between wind speed at deck level and wind speed at masthead.  So the reef gives you less sail, at a lower centre of effort, and at a lower average windspeed.

Also, reefing may alter the draught of the sail, which may have an impact of the heeling force.

But in general, it seems to me that you are right in broad principle.

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Not checking beezers math but 1 crew = 50 sq ft sail sounds too much. A 150 on a Ranger 37 might be 500 ft2. Remove 8 guys x 50 ft2 = 400 ft2 less. That would give you a pretty small jib...

Why don't you do a Wed night race and sail with the jib 2 handed and see how you do? 

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10 hours ago, TwoLegged said:

It's bit more complex than that, because when you reef that main you also lower its centre of effort.   So if the first reef on your main say 4 foot deep, you lower the centre of effort by 2 feet. That's a bonus you haven't factored in.

And in lighter winds, there may be a significant difference between wind speed at deck level and wind speed at masthead.  So the reef gives you less sail, at a lower centre of effort, and at a lower average windspeed.

Also, reefing may alter the draught of the sail, which may have an impact of the heeling force.

But in general, it seems to me that you are right in broad principle.

Not to mention the fact that increase in wind force is not linear to increase in wind velocity.

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This thread started with the question of being competitive while short handed against similar fully crewed boats. 

I don’t think you can really do it across all wind ranges.  The RM from weight on the rail is really significant.  
 

I wish it weren’t true because it turns out that I really like racing short handed, but my boat is designed for crew on the rail.  We re-rated with a smaller jib, by the 9 phrf points don’t go far. 

I’m still having fun going out, but we’ve had our worst years (in results) by far since Covid started. Lack of practice doesn’t help either (a lot less racing and a lot more family sailing). 

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3 hours ago, Alex W said:

This thread started with the question of being competitive while short handed against similar fully crewed boats. 

I don’t think you can really do it across all wind ranges.  The RM from weight on the rail is really significant.  
 

I wish it weren’t true because it turns out that I really like racing short handed, but my boat is designed for crew on the rail.  We re-rated with a smaller jib, by the 9 phrf points don’t go far. 

I’m still having fun going out, but we’ve had our worst years (in results) by far since Covid started. Lack of practice doesn’t help either (a lot less racing and a lot more family sailing). 

This^^^

Lets say your particular boat is fully powered up at 15 degrees of heel (assuming perfect sail trim).  With a crew of 10, you can have say 7 on the rail (helm, main trimmer and jib trimmer not on the rail), or 1400lbs (200lbs per crew) x 5ft (from centerline) = 7000lbs of extra righting moment, allowing you to carry your 155 jenny and a fully powered up main.  With 4 crew, you have 1 on the rail so 200lbs X 5 ft = 1000lbs of extra righting moment, which means you need to have the the #3 jib (say a 105%) and a fully bladed out main.  So you have 6000lbs less righting moment, and a sail plan generating significantly less power.  The fully crewed boat will sail away from you. To be equal to it, you'd need to add weight at the bottom of the keel (or depth, or both) to add back the missing 6000lb of righting moment.

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7 hours ago, Crash said:

you'd need to add weight at the bottom of the keel (or depth, or both) to add back the missing 6000lb of righting moment.

Or add water ballast.  A lot of under-ballasted IOR boats appear to have hull shapes which would lend themselves well to a decent dose of water ballast, if you didn't mind some chainsaw action to the cabin when retrofitting the tanks and pipes.

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14 hours ago, bridhb said:

Also, when heeled, the lever arm for the rail meat is reduced.

I'm not sure about this.  True, the horizontal distance to the centerline will shorten as the windward side tips upwards.  But I think the center of buoyancy also moves out to leeward as more of the leeward side of the hull is in the water.  How these two balance out to affect the lever arm is beyond my capabilities to figure out.

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2 hours ago, Corryvreckan said:

I'm not sure about this.  True, the horizontal distance to the centerline will shorten as the windward side tips upwards.  But I think the center of buoyancy also moves out to leeward as more of the leeward side of the hull is in the water.  How these two balance out to affect the lever arm is beyond my capabilities to figure out.

I think you are correct tat the CB moves to leeward and also, the keel ballast becomes more effective as the boat heels, but lever arm of the rail meat decreases with increased angle of heel.

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1 hour ago, bridhb said:

I think you are correct tat the CB moves to leeward and also, the keel ballast becomes more effective as the boat heels, but lever arm of the rail meat decreases with increased angle of heel.

Though not that much at "normal" angles of heel.  For example at 15 degrees, (cos 15) you retain .966 of your righting arm, or in my earlier example of 7000 lbs of extra righting moment, its really 6761 lbs at 15 degrees.  And as someone else said, you pick up rm from the keel as you heel.  Even at 45 degress, you still have .707 of your extra righting moment or 4950 lbs of extra RM.  So a crewed boat with bodies hiking always has an advantage (upwind) over a shorthanded boat of same design, except in light air..

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4 hours ago, Crash said:

Though not that much at "normal" angles of heel.  For example at 15 degrees, (cos 15) you retain .966 of your righting arm, or in my earlier example of 7000 lbs of extra righting moment, its really 6761 lbs at 15 degrees.  And as someone else said, you pick up rm from the keel as you heel.  Even at 45 degress, you still have .707 of your extra righting moment or 4950 lbs of extra RM.  So a crewed boat with bodies hiking always has an advantage (upwind) over a shorthanded boat of same design, except in light air..

Crash, your calcs appear to assume that the crew are on the same horizontal plane as the centre of buoyancy.  They are not, because that would place them underwater.

The fact that they are significantly higher then the centre of buoyancy significantly diminishes their right moment as the boat heels. 

Take for example a modern 36ft LOA boat with 12ft beam.  The railmeat are 6ft from the centreline, and their CoG is probably 4ft above the waterline.   So a line from the meatCoG to the pivot point is at a 34-degree elevation to the horizontal.

If we heel the boat another 56 degrees on the same CoG, the meat therefore ends up directly above the centre of buoyancy, giving zero righting movement.

Obviously, we won't heel that far in normal use, and if we did heel that far then the centre of buoyancy would move further outboard.   So the calcs are not straightforward, but any non-zero freeboard means that the meat are moved inboard a the boat heels.  To picture this, take an extreme exaggeration: suppose that this 12ft beam boat had an insane 40 feet of freeboard: if it heeled 5.7 degrees, the meat would be over the centre of buoyancy.

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Leggs,

You are, of course right!  Though I didn’t assume it, I was just trying to simplify and focus only on the effect of extra crew on the rail.  But I should have added a disclaimer to highlight that. There are, as I’m sure you know, many other factors that enter into the conversation (keel COG, center of buoyancy of heeled hull, weight of rig and sails, etc, etc.)

Crash

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2 minutes ago, Zonker said:

Windage of crew on the rail...

You need skinny guys who swallow condoms full of lead shot right before a race. Totally within the spirit of the rules I think.

Hey, please be inclusive.  Catholics aren't allowed to use condoms, so they should swallow the lead without a cover.

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2 minutes ago, TwoLegged said:

Hey, please be inclusive.  Catholics aren't allowed to use condoms, so they should swallow the lead without a cover.

Have some heart, lead is bad for the bod. Maybe put the lead (or even better, mercury) into a Freezer Ziploc.

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Reminds me when I was a lad, crewing on a Flying Dutchman. At 175 lbs (wish I was that now) I was a bit light on the trapeze, so the skipper had me wear a water-filled weight vest. It did not decrease my windage but I didn't sink like like a stone in a capsize either...

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On 11/6/2021 at 2:06 AM, Zonker said:

Not checking beezers math but 1 crew = 50 sq ft sail sounds too much. A 150 on a Ranger 37 might be 500 ft2. Remove 8 guys x 50 ft2 = 400 ft2 less. That would give you a pretty small jib...

Why don't you do a Wed night race and sail with the jib 2 handed and see how you 


Reasonable but then there’s nothing to mull over  on the couch when it’s 40 degrees outside and my race to Nassau just got cancelled.

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22 hours ago, Zonker said:

Windage of crew on the rail...

You need skinny guys who swallow condoms full of lead shot right before a race. Totally within the spirit of the rules I think.

More importantly (for lighter boats), is weight. Sport boats will struggle to plane in marginal conditions with too much crew. Even a displacement boat will be pushing more water. You may gain a few seconds up wind, only to lose them downwind.

This is actually complicated and boat-specific.

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On 11/5/2021 at 10:57 PM, beezer said:

Mainsail area is staying the same.  The smaller headsail has not affected helm much.  If anything it’s a bit more neutral where I would think I should have more weather helm, but I don’t. 

The least efficient sail area on a boat is foresail overlap. Get rid of the overlap area first, making sure that you maintain full foresail luff length.

A short footed jib also makes for faster, easier tacking, especially short handed. And you don’t have to change foresails so much either. Reefing the mainsail is faster and easier short handed.

If you can, rake the mast aft if you need more weather helm, and/or work on mainsail trim.

Extra (internal) ballast is also helpful, especially in terms of rating.

All of this is still no substitute for the right amount of rail meat, but helps to reduce the difference.

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For displacement boats, on a typical windward - leeward race course, windward speed is all important because you spent much MORE TIME tacking upwind. 

So the extra RM of the rail meat is usually very helpful in carrying more sail and going faster.

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3 hours ago, Sidecar said:

The least efficient sail area on a boat is foresail overlap. Get rid of the overlap area first, making sure that you maintain full foresail luff length.

A short footed jib also makes for faster, easier tacking, especially short handed. And you don’t have to change foresails so much either. Reefing the mainsail is faster and easier short handed.

If you can, rake the mast aft if you need more weather helm, and/or work on mainsail trim.

Extra (internal) ballast is also helpful, especially in terms of rating.

All of this is still no substitute for the right amount of rail meat, but helps to reduce the difference.

This was along the lines of what I was thinking.  There is also a rating bump of 15 points to help balance things out when sail area is removed.  Windward leeward is not really the venue I am thinking of.  I have one design racing on others boats for that.  This would mostly be distance racing point to point.  

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It depends on the specific geometry of each boat.

A beamy boat with low freeboard will benefit much more from weight on the rail.  A narrow boat may not benefit from weight on the rail at all.  My boat is actually faster with fewer people onboard than stacking the rail because it is so narrow.  Yes I have run the vpp to figure it out.

You gotta figure the actual righting moment curve for a given boat, there's no simple rule of thumb.  

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1 hour ago, bgytr said:

It depends on the specific geometry of each boat.

A beamy boat with low freeboard will benefit much more from weight on the rail.  A narrow boat may not benefit from weight on the rail at all.  My boat is actually faster with fewer people onboard than stacking the rail because it is so narrow.  Yes I have run the vpp to figure it out.

You gotta figure the actual righting moment curve for a given boat, there's no simple rule of thumb.  

How did you get some of the measures for you boat? Did you measure it? It seems that some of the measures aren't on ORC certificates.  

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1 hour ago, beezer said:

This was along the lines of what I was thinking.  There is also a rating bump of 15 points to help balance things out when sail area is removed.  Windward leeward is not really the venue I am thinking of.  I have one design racing on others boats for that.  This would mostly be distance racing point to point.  

The advantage of over lap is on close reaching courses, not windward and too close (or strong) for a reacher. It's not just the area, it is also better airflow around the main. The difference can be considerable. So point-to-point is different from windward leeward, which in the real world, is rather arbitrary.   VMG to windward matters, but so does speed on every reach.

I quit racing decades ago, but I still like speed and passing boats.

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Funny, someone forget to tell IOR boats that foresail overlap is least efficient.  Most IOR masthead rigs went to weather just great. All of them carried overlapping number 1 genoas.  The main was just a trim tab.

Given today's sail technology, and deep bulbed keels, etc., I would agree on a modern boat overlap is not efficient.  Back in the day, overlap and a ribbon main was pretty good at driving a boat upwind.

 

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28 minutes ago, Crash said:

Funny, someone forget to tell IOR boats that foresail overlap is least efficient.  Most IOR masthead rigs went to weather just great. All of them carried overlapping number 1 genoas.  The main was just a trim tab.

The IOR rule was relatively favourable to Genoa overlap because of a hangover to earlier rating systems (CCA and RORC) where overlap area was effectively free. And the mainsail had effectively only a trim/balance role. With the advent of IRC, which measures area, wherever it is, pretty much equally, the increasing trend has been to (almost) non overlapping jibs.

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2 hours ago, thinwater said:

The advantage of over lap is on close reaching courses, not windward and too close (or strong) for a reacher. It's not just the area, it is also better airflow around the main. The difference can be considerable. So point-to-point is different from windward leeward, which in the real world, is rather arbitrary.   VMG to windward matters, but so does speed on every reach.

Area for area it is unlikely to be faster, but sheeting angle and leech control becomes more critical for tall narrower foresails. Get it wrong, and you lose a lot.

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6 hours ago, Sidecar said:

Area for area it is unlikely to be faster, but sheeting angle and leech control becomes more critical for tall narrower foresails. Get it wrong, and you lose a lot.

Area for area, no. But there is more area. And like the IOR rule, when it comes down to ratings it all gets silly again. Obviously, you can carry more sail off the wind, and ballast is where the thread started.

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9 hours ago, Sidecar said:

The IOR rule was relatively favourable to Genoa overlap because of a hangover to earlier rating systems (CCA and RORC) where overlap area was effectively free. And the mainsail had effectively only a trim/balance role. With the advent of IRC, which measures area, wherever it is, pretty much equally, the increasing trend has been to (almost) non overlapping jibs.

I think the development of, and routine use by, even the racer/cruiser of carbon rigs, bulbed keels, and high tech (light weight/low stretch) sails and cordage, has also allowed that trend.  Back in the IOR days, SA/D could be as low as 17, now even the new First 36 by Beneslow is talking a SA/D of 29...

Also, though the trend for pure on the wind work is a non-overlapping jib, the recent development of code sails for use when reaching shows (as you point out) that there is still an advantage to overlapping sails as soon as one cracks off the wind some...

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13 hours ago, Elegua said:

How did you get some of the measures for you boat? Did you measure it? It seems that some of the measures aren't on ORC certificates.  

My boat is in the boat database shared by ORR  and ORC.  I've done some work with ORR in the past- honestly I was surprised at the results showing that my boat is actually a tad slower with more weight on the rail upwind, so I did some hand calc estimates on my own.  Sure enough that's the way it works out.

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51 minutes ago, bgytr said:

My boat is in the boat database shared by ORR  and ORC.  I've done some work with ORR in the past- honestly I was surprised at the results showing that my boat is actually a tad slower with more weight on the rail upwind, so I did some hand calc estimates on my own.  Sure enough that's the way it works out.

The paid data-base or the "free" certificates? 

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On 11/5/2021 at 11:06 PM, Zonker said:

Not checking beezers math but 1 crew = 50 sq ft sail sounds too much. A 150 on a Ranger 37 might be 500 ft2. Remove 8 guys x 50 ft2 = 400 ft2 less. That would give you a pretty small jib...

Why don't you do a Wed night race and sail with the jib 2 handed and see how you do? 

This is a very reasonable approach on classic 1970s IORish mast head boats. The #2 jib works well short handed on my half tonner with more lead than most. I use the blade when I am sailing by myself or when it is over 16kts.  mainsheet controls, vang and sail foil shape will give you the right amount of heel for waterline once you get it dialed in. 

 

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How do you find pointing with a #2? Most folks can't sheet it tight enough due to spreader/shrouds but because of shorter foot than #1 the deep part of the curve is...

Really bad sketch of this:

Thats why you jump from a 1 to a 3 which is just fwd of the spreaders.

 

image.png.87524337a9c9ea92e204e85e6b2d84b3.png

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8 hours ago, Crash said:

I think the development of, and routine use by, even the racer/cruiser of carbon rigs, bulbed keels, and high tech (light weight/low stretch) sails and cordage, has also allowed that trend.  Back in the IOR days, SA/D could be as low as 17, now even the new First 36 by Beneslow is talking a SA/D of 29...

Also, though the trend for pure on the wind work is a non-overlapping jib, the recent development of code sails for use when reaching shows (as you point out) that there is still an advantage to overlapping sails as soon as one cracks off the wind some...

See I’ve always had a problem with old boats vs new boats in the sail area to displacement ratio. It’s all based on a 100% jib.  So an ior boat that runs a 150 looks like a cruising boat compared to a boat with the same overall sail area when more of it is in the main.  It’s apples and oranges.  For instance compare the calculator for a cape fear 38 to the old Ranger.  Cape fear 38 is showing around 748 sf of sail vs the piddly 628 for the Ranger. But jib overlap actually gives you around 500sf Genoa and 250 in the mainsail.  So sail area is pretty much identical.  Displacement is around 11k for the cape fear and 15.5k for the Ranger.  So calculated sa/d for the cape fear is a whopping 23.2 vs 16.5 for the Ranger.  On paper.  It’s bogus because actual sail area to displacement for the Ranger is about 20.6.  That SA to displacement number only works like for like imo.  Ranger is still much much slower but not as much as the ratio implies. 

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6 hours ago, Zonker said:

How do you find pointing with a #2? Most folks can't sheet it tight enough due to spreader/shrouds but because of shorter foot than #1 the deep part of the curve is...

Really bad sketch of this:

Thats why you jump from a 1 to a 3 which is just fwd of the spreaders.

 

image.png.87524337a9c9ea92e204e85e6b2d84b3.png

There is the rub ;) as you point out. The number 2 is really hard to sheet tightly and as quickly as smaller jib is when double handing. If the boats are kept close to original design - the spreaders, strouds and life lines more often block the tighter sheet angles that would be ideal.  I have been playing with moving the jib cars when flying the 2 forward a notch and getting a fuller sail with some noticeable performance differences that suggesting fuller maybe better when caught in a boxed wind range of less than 14 when trying to climb uphill. These ladies aren't not going to be able to point as high as with an inside blade (i get within 24.5 degrees) or 100 percent but the power is there to sail a slight fatter faster attack angles. Sailing faster over slightly more distance without putting the trimmer on the rails has some real merit.  A couple of key things I do that help when the #2 is used is I take some bend out of the mast, making it stand straighter, travel up slightly beyond center and relieve the outhaul a little causing lower 1/3 of mainsail to begin show some slight bagging while holding its good shape are some things i recommend others try.  

If the wind is a constant true 13-14kts over a short course with the mark requiring close hauled sails and multiple quick tacks, the blade may be better as distance sailed is less but the your boat better be ready to do a good problem free symmetrical spin run back as the other, newer, lighter boats will surely begin to reel you in. 

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7 hours ago, Elegua said:

The paid data-base or the "free" certificates? 

The hull offsets and rig dimensions are fully implemented in the data sets from a long time ago during MHS days.  The only other measurements that might vary are sails, displacements and inclining data.  The sails are explicitly input for my sails, and the incline and displacement are from the class average for my boat, which was quite consistent with minimal variation with our sisterships back in the day which were all fully measured.

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38 minutes ago, Black Jack said:

There is the rub ;) as you point out. The number 2 is really hard to sheet tightly and as quickly as smaller jib is when double handing. If the boats are kept close to original design - the spreaders, strouds and life lines more often block the tighter sheet angles that would be ideal.  I have been playing with moving the jib cars when flying the 2 forward a notch and getting a fuller sail with some noticeable performance differences that suggesting fuller maybe better when caught in a boxed wind range of less than 14 when trying to climb uphill. These ladies aren't not going to be able to point as high as with an inside blade (i get within 24.5 degrees) or 100 percent but the power is there to sail a slight fatter faster attack angles. Sailing faster over slightly more distance without putting the trimmer on the rails has some real merit.  A couple of key things I do that help when the #2 is used is I take some bend out of the mast, making it stand straighter, travel up slightly beyond center and relieve the outhaul a little causing lower 1/3 of mainsail to begin show some slight bagging while holding its good shape are some things i recommend others try.  

If the wind is a constant true 13-14kts over a short course with the mark requiring close hauled sails and multiple quick tacks, the blade may be better as distance sailed is less but the your boat better be ready to do a good problem free symmetrical spin run back as the other, newer, lighter boats will surely begin to reel you in. 

That’s really awesome feedback. Thx for posting

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3 hours ago, beezer said:

See I’ve always had a problem with old boats vs new boats in the sail area to displacement ratio. It’s all based on a 100% jib.  So an ior boat that runs a 150 looks like a cruising boat compared to a boat with the same overall sail area when more of it is in the main.  It’s apples and oranges.  For instance compare the calculator for a cape fear 38 to the old Ranger.  Cape fear 38 is showing around 748 sf of sail vs the piddly 628 for the Ranger. But jib overlap actually gives you around 500sf Genoa and 250 in the mainsail.  So sail area is pretty much identical.  Displacement is around 11k for the cape fear and 15.5k for the Ranger.  So calculated sa/d for the cape fear is a whopping 23.2 vs 16.5 for the Ranger.  On paper.  It’s bogus because actual sail area to displacement for the Ranger is about 20.6.  That SA to displacement number only works like for like imo.  Ranger is still much much slower but not as much as the ratio implies. 

beezer, see the pic above your post.  No IOR boat, or a Ranger 37 could sheet a jib to the 4 degree line that jib is sheeted to.  You need modern laminates to allow that kind of tensions.  You'd rip the clew right out of any IOR era sail cloth...

While overlap adds power, it is a less efficient way to do it.  Just like with keel (or sailplane wings), you are much better off, from a lift/drag ratio perspective, with a long span/short chord airfoil, (tall rig, no overlap) than you are with a shorter span, longer chord airfoil (shorter rig, overlapping genoa).  And that what overlap is.  A shorter rig, with a longer LP means more drag for the amount of lift it can generate.

But a boat like a Ranger 37, with its "Peterson-esque" trapezoidal keel, and (heavy) aluminum rig, can't carry a long span (tall) rig, as it doesn't have enough stability to have a rig with such a high CoE.

And OBTW, the Ranger 37 is way slower than a Cape Fear 38, at least until the Cape Fear has a keel issue...B) 

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21 hours ago, Crash said:

beezer, see the pic above your post.  No IOR boat, or a Ranger 37 could sheet a jib to the 4 degree line that jib is sheeted to.  You need modern laminates to allow that kind of tensions.  You'd rip the clew right out of any IOR era sail cloth...

While overlap adds power, it is a less efficient way to do it.  Just like with keel (or sailplane wings), you are much better off, from a lift/drag ratio perspective, with a long span/short chord airfoil, (tall rig, no overlap) than you are with a shorter span, longer chord airfoil (shorter rig, overlapping genoa).  And that what overlap is.  A shorter rig, with a longer LP means more drag for the amount of lift it can generate.

But a boat like a Ranger 37, with its "Peterson-esque" trapezoidal keel, and (heavy) aluminum rig, can't carry a long span (tall) rig, as it doesn't have enough stability to have a rig with such a high CoE.

And OBTW, the Ranger 37 is way slower than a Cape Fear 38, at least until the Cape Fear has a keel issue...B) 

Fun conversation.  

I agree the Ranger is much slower, which is why I said “. Ranger is still much much slower but not as much as the ratio implies”. The way they calculate the ratio just favors big mainsails.  Some manufacturers now apparently use working sail area when publishing ratios for just this reason.  Better off looking at phrf base ratings to judge speed potential. Sa/d is not much use unless comparing like with like. 

Re spars… The Ranger already has a taller mast, with a half foot longer I and almost a foot longer P than the CF.  That’s not even the tall mast version!   That big heavy aluminum mast is part of the heeling problem short-handed. Power is not a problem on the Ranger, turning that power into speed and not heeling is!

Re the modern sails thing, In not sure what you are trying to say?  I run a blade on an inside track that is Dacron.  I have the exact sheeting angles that the j120 run on their inside tracks and with that blade we point really high.  It’s not 4 degrees, but how many boats run 4 degree sheeting angles?  We are definitely limited by the keel shape, but this thing goes upwind very very well, even with old Dacron sails. 

 

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Going back to the seat of the pants calculations,  keep in mind that the boat is fastest upwind heeling at the point of maximum power, assuming there is enough wind to get you there. It's usually at about 25-30 degrees angle of heel. The designer would be very aware of this and arrange to have max effective LWL and best water flow at that angle. 

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6 hours ago, SemiSalt said:

Going back to the seat of the pants calculations,  keep in mind that the boat is fastest upwind heeling at the point of maximum power, assuming there is enough wind to get you there. It's usually at about 25-30 degrees angle of heel. The designer would be very aware of this and arrange to have max effective LWL and best water flow at that angle. 

Hmm ok that seems pretty far over, no?  All I ever seem to hear is flat is fast and to keep things no more than 15 degrees or so.  Is that advice more pertinent to more modern hull forms?  Even the j30 which is just about as old seems to like flatter angles of heel, or at least that’s what they tell me.  15 degrees is what I’m shooting for to keep the cruising comfortable.  At 30 decrees I’m fighting the wheel and it’s a pita. That might just be the old sails though. 

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1 hour ago, beezer said:

Hmm ok that seems pretty far over, no?  All I ever seem to hear is flat is fast and to keep things no more than 15 degrees or so.  Is that advice more pertinent to more modern hull forms?  Even the j30 which is just about as old seems to like flatter angles of heel, or at least that’s what they tell me.  15 degrees is what I’m shooting for to keep the cruising comfortable.  At 30 decrees I’m fighting the wheel and it’s a pita. That might just be the old sails though. 

I could be wrong. Any particular boat could be different. At 15 deg, you aren't getting a lot of help from the keel.

I got to wondering at what angle of heel the leech of the jib is vertical?  Or to put it a bit differently,  when is the head of the jib over the rail?

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1 hour ago, SemiSalt said:

I got to wondering at what angle of heel the leech of the jib is vertical?  Or to put it a bit differently,  when is the head of the jib over the rail?

That's a fairy easy calculation.

https://sailboatdata.com/sailboat/j30 says the J/30 I dimension is 34.19 ft.  Beam is 11.18ft, so if the jib is sheeted to the beam at Bmax, the the head needs to tilt 5.6ft to make the leech vertical (assuming that it's sheeted to the rail).

The angle at which that happens is the arctan (5.6/34.19) = 9.3 degrees.   If the jib is sheeted inboard of Bmax, the angle will be lower

 

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23 hours ago, SemiSalt said:

Going back to the seat of the pants calculations,  keep in mind that the boat is fastest upwind heeling at the point of maximum power, assuming there is enough wind to get you there. It's usually at about 25-30 degrees angle of heel. The designer would be very aware of this and arrange to have max effective LWL and best water flow at that angle. 

I have a very tender boat by todays standards, plus it is a very full keel one, so being inclined is a bit less horrible for leeway. Apart from the fact that everything is a struggle at 20°, even with the full keel we start to go seriously sideways when heeling more that 25°. I would agree that with higher winds and some waves 20 to 25° is ok when you dont pinch with an old full keeled raceboat, with anything having some beam or a fin keel you are probably faster in between 10 to 15 degrees. 

Almost everyone reefs at 15 to 20 degrees, most designers might be aware of this. Real raceboats might be different, bit there you would have some advice on optimal heeling angles from desinger etc.

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17 hours ago, beezer said:

Hmm ok that seems pretty far over, no?  All I ever seem to hear is flat is fast and to keep things no more than 15 degrees or so.  Is that advice more pertinent to more modern hull forms?  Even the j30 which is just about as old seems to like flatter angles of heel, or at least that’s what they tell me.  15 degrees is what I’m shooting for to keep the cruising comfortable.  At 30 decrees I’m fighting the wheel and it’s a pita. That might just be the old sails though. 

15 to 20 degrees seems to be the max optimum heel for most keelboats nowadays, especially if they are wide and fat for their length.

Another factor is rudder effectiveness, and again, wide and fat, particularly at the stern means the rudder starts to lose significant efficiency at ~ 20+degrees.

The other factor is the transverse CE/CLR relationship. Whilst a boat theoretically might seem balanced longitudinally, The more the heel, the more the CE is to leeward of CLR, the more the turning moment into the wind.

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Good topic. My boat is designed to carry an overlapping genoa but the main is the big dog. Last year, because of Covid, a lot of races were held with crew limited to family members. We did quite well in 10 kts or more with our #3 while keeping the main pretty full. This was against similar boats with similar crew numbers (3 or less) carrying larger genoas. That's purely subjective but we always finished middle of the pack or better in our fleet and it was the upwind legs where we did the most damage with our tighter sheeting angles. I wish there were more events like that but we seem back to rail meat racing now exclusively.

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On 11/13/2021 at 2:02 PM, Sidecar said:

15 to 20 degrees seems to be the max optimum heel for most keelboats nowadays, especially if they are wide and fat for their length.

Another factor is rudder effectiveness, and again, wide and fat, particularly at the stern means the rudder starts to lose significant efficiency at ~ 20+degrees.

AIUI, this doesn't apply to twin-ruddered fat boats such as the Pogos.

Their rudders are designed to work just fine at well over 20 degrees of heel, and their hull shape is optimised to significantly reduce wetted surface at those heel angles.   @shaggybaxter described a race in his Pogo 12.50 where they were doing poorly upwind until he handed over the helm to a pal who increased the heel and gained a lot of speed.

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4 hours ago, TwoLegged said:

AIUI, this doesn't apply to twin-ruddered fat boats such as the Pogos.

100% Correct. Heel the boat just enough and you halve the rudder drag and have more control.

I was referencing older style boats such as the OP’s.

I also used to own a fat arsed boat with a single rudder, (Beneteau 27.7) and it was not OK at much more than 20%. It would have been a faster boat with two rudders, and with no IRC penalty.

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11 hours ago, TwoLegged said:

AIUI, this doesn't apply to twin-ruddered fat boats such as the Pogos.

Their rudders are designed to work just fine at well over 20 degrees of heel, and their hull shape is optimised to significantly reduce wetted surface at those heel angles.   @shaggybaxter described a race in his Pogo 12.50 where they were doing poorly upwind until he handed over the helm to a pal who increased the heel and gained a lot of speed.

Ayup. Like when Mr Trimmer extraordinaire, whom we shall call Stig, would park down on the low side and grunt either " lift" or 'press'. At least I think it was 'lift' as all I ever heard was 'press...................press.............................press.................there, that's better'.

IMHO, the best thing about the heel was the immersed rudder getting vertical at speed. The rudder went from 4' to 10' in draft, developed sports car like grip, gave you loads of feel and a linear response to any helm inputs. I got into a bad habit of not calling for trim as I was having too much of a fat time just screaming all over the ocean watching the forestay angle and playing the gusts.

Shithouse idea of course when you're racing, but man...so much fun.      

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