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Surfing vs. Plaining


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1 hour ago, 12 metre said:

I can't find the post by Crash where he states that.  The closest I can find is the post by Borracho below where he states wave making drag is reduced when planing.  I'm not sure about that contention although it may well be true.

I was referring to the last paragraph in the post I quoted

"Planning occurs when hydrodynamic lift results in a reduction of drag, and allows the boat to accelerate well beyond hull speed with no increase in the thrust the engine (sails) is/are providing"

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16 minutes ago, SemiSalt said:

The Cal 40 (1963) was one of the boats that started changing people's minds. By the time of the J-24 (1975), the revolution was complete. It's not a coincidence that was also the era of the shift to fin keels in offshore boats. 

 

Actually the J/24 came out in 1976 or maybe even later - early 1977.  Anyways, the Moore 24 and Santa Cruz 27 both predate the J by several years and are much better examples.  Could probably throw in some of John Spencers work from the 60's - although being kiwi, few people in NA would have been aware of what was going on down there.  Further back you could look at Black Soo by Van De Stadt from the 50's.  black_soo_drawing.jpg

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1 hour ago, 12 metre said:

But I do know that overall drag never goes down when planing.  if it were the case, a boat could be caught in a "Twilight Zone" where it would never come off plane as it would caught in a hollow of the drag curve and it would take more power to push it up the backside of the curve to slow it down. 

I don't think that's correct.

Drag curves of planing hulls (or foilers) can have regions of negative slope, like the case below (from Hoerner's Fliuid Dynamic Drag) and those boats manage to decelerate just fine anyway.

PlaningDrag.jpg.7c0b3db0db3f9cccea4282547017d3a6.jpg

 

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21 minutes ago, Doug Halsey said:

I don't think that's correct.

Drag curves of planing hulls (or foilers) can have regions of negative slope, like the case below (from Hoerner's Fliuid Dynamic Drag) and those boats manage to decelerate just fine anyway.

PlaningDrag.jpg.7c0b3db0db3f9cccea4282547017d3a6.jpg

 

Note that the curve is for a Flying Boat  i.e. an aircraft like the PBY Catalina and Martin Mars (converted to water bombers in Canada and I think a couple of them may be left).  

Note the stepped hull in the drawing that makes it clear this is an aircraft and which changes the whole analysis especially since you're dealing with aeration to break the suction Fastyacht alludes to.  This is not a sailboat hull of any form that I am aware of.

Below is a Martin Mars in action:

MarsWaterBomberfirstImage-600x337.jpg

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2 hours ago, 12 metre said:

IBut I do know that overall drag never goes down when planing.  if it were the case, a boat could be caught in a "Twilight Zone" where it would never come off plane as it would caught in a hollow of the drag curve and it would take more power to push it up the backside of the curve to slow it down. 

I don't think that's quite correct - to say the least. A craft with such a drag curve would just decelerate very quickly as the drag dramatically increased with decreasing speed.  I think its probably unlikely such exists, but it would be kinda dramatic because the boat would take off like a scalded cat when it reached the low drag zone.

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On 6/13/2021 at 12:10 PM, axolotl said:

Doing this is difficult and requires topnotch crew and gear.  Key is the driver, who controls the "snaking" path of the boat, not too low & slow, not too high & fast with a bad VMG, main thing is to stay on the swell as much a possible; really good surfboarders have the knack and patzers like me were never allowed to helm. 

 

2 hours ago, SVArcturus said:

  It might not be good to try to transfer too much of how to catch a shore wave with a surfboard into how to catch an ocean wave with a boat.

Disagree.  Having surfed for 55 years and sailed for 58, I find that much of the surfing skill is transferable to sailing downwind in the ocean.  Timing is everything.  I often look over my shoulder for approaching swells and heat up to catch them, turn down to ride them and giggle like a little girl.  I do this now on my Weta, but in the past I have also done it on lots of OPBs, including an F28, J35, J22, Val31, and on powerboats. In fact, this knowledge has allowed me to safely navigate small powerboats across the Santa Barbara Channel in some pretty nasty afternoon and nighttime blows. So,  knowing when to turn around and paddle to catch a breaking wave on a surfboard and knowing when to heat up and then turn down to catch a swell or whitecap while sailing are very closely related AFAIC.

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17 minutes ago, JimC said:

I don't think that's quite correct - to say the least. A craft with such a drag curve would just decelerate very quickly as the drag dramatically increased with decreasing speed.  I think its probably unlikely such exists, but it would be kinda dramatic because the boat would take off like a scalded cat when it reached the low drag zone.

Yeah, I don't think I explained that well.    What I should have said was that if such a hollow in the drag curve existed, then if a puff hit (or more power is applied) then the boat wouldn't know whether to speed up or slow down - in theory it could go either way along the curve of increasing drag.

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1 minute ago, 12 metre said:

Yeah, I don't think I explained that well.    What I should have said was that if such a hollow in the drag curve existed, then if a puff hit (or more power is applied) then the boat wouldn't know whether to speed up or slow down - in theory it could go either way along the curve of increasing drag.

No.

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32 minutes ago, JimC said:

I don't think that's quite correct - to say the least. A craft with such a drag curve would just decelerate very quickly as the drag dramatically increased with decreasing speed.  I think its probably unlikely such exists, but it would be kinda dramatic because the boat would take off like a scalded cat when it reached the low drag zone.

Your description is exactly what happens to foiling Moths.

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15 minutes ago, 12 metre said:

Okay, guess I'm missing something here.

You're just overthinking. The only real difficulty would be maintaining a constant speed in the reducing drag zone - say for harbour speed limits. The boat would be wanting to speed up all the time. What also complicates the affair is apparent wind effects.

 

7 minutes ago, Doug Halsey said:

Your description is exactly what happens to foiling Moths.

Yes indeedy, foilers are an excellent example, but for some reason that escapes me now I excluded them from my thinking!

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12 graphs can mess with you.

The hump is drag vs speed. Slowing down, you dont have to add powr---you experience bigger drag and decceleration.. Simple. You slow. You pass through the hum spit out the back side where the curve has same drag at lower speed. In terms of power outpit vs speed there is hysteresis going from slower to faster you have to climb the hill. The  you accelereate down the slope unti you are at the trough or farther.

You dont really ever operate on the downslope. As you observr, that would be kind of impossible. Acceleration occurs there.

 

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57 minutes ago, 12 metre said:

Okay, guess I'm missing something here.

It helps to think of the drag curves as representing perfectly balanced conditions, but with either stable or unstable equilibrium.

When the curves have positive slope, a slight imbalance in thrust and drag results in an acceleration or deceleration that tends to reduce the imbalance.

When the curves have negative slope, the imbalance gets larger until different regions of the curves are reached.

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This is a strange thread.

To me surfing is nothing more than a means of propulsion by the waves, which in a sailboat can result in a burst of speed beyond what could have been provided by the sails alone.

Planing is the act of the boat exceeding displacement speed limits by riding on top of the water, which might be a result of lots of wind in the sails, surfing, or a powerful motor.

Surfing is not the only means to plane, and you can surf without planing too. They are quite different things but might just happen at the same time. 

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1 hour ago, unShirley said:

 

Disagree.  ... on powerboats. In fact, this knowledge has allowed me to safely navigate small powerboats across the Santa Barbara Channel in some pretty nasty afternoon and nighttime blows. So,  knowing when to turn around and paddle to catch a breaking wave on a surfboard and knowing when to heat up and then turn down to catch a swell or whitecap while sailing are very closely related AFAIC.

Radon? Lucky!

I just bought my first powerboat: Parker 2530. Very happy with the strength and performance.

volunteer_on_station.jpg

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^

No, not a Radon....I wish.  I first started crossing the SBC to surf the CI in a UCSB sailing team 1 tonner.  Then I bought a Tremolino and used it for 13 years. Next a 20' cuddy cabin I/O and then finally a 19' center console power cat.  I use to scare the crap out of my surfer buddies crossing the channel after dark (gotta surf that evening glass) in 5' seas and 20+ kts of wind.  Have crossed plenty on a friend's Radon.  Now, that is a cadillac ride!  BTW: Parkers are great boats. You're the lucky one.

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15 minutes ago, unShirley said:

^

No, not a Radon....I wish.  I first started crossing the SBC to surf the CI in a UCSB sailing team 1 tonner.  Then I bought a Tremolino and used it for 13 years. Next a 20' cuddy cabin I/O and then finally a 19' center console power cat.  I use to scare the crap out of my surfer buddies crossing the channel after dark (gotta surf that evening glass) in 5' seas and 20+ kts of wind.  Have crossed plenty on a friend's Radon.  Now, that is a cadillac ride!  BTW: Parkers are great boats. You're the lucky one.

Do you mean a Francis Kinney Tremolino?

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8 hours ago, Borracho said:

Yes. I think the casual discussions above have confused absolute drag with the slope of the drag curve. The rate of increase in drag is reduced. 

This is what Crash meant to say...not that drag was reduced as a absolute...apologies for not being more accurate with my wording. :( 

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9 hours ago, Borracho said:

Is this terminology creep? A fully planing craft would be a foiling kiteboard.

But can you let the terminology creep to where a planing craft has nothing whatsoever on the surface?  I'm thinking foiling is a whole different animal than planing (unless the foil gets on the water surface, which is generally considered a bad move as I understand it).

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13 minutes ago, SVArcturus said:

But can you let the terminology creep to where a planing craft has nothing whatsoever on the surface?  I'm thinking foiling is a whole different animal than planing (unless the foil gets on the water surface, which is generally considered a bad move as I understand it).

I tend to agree with you - but that is just my view.  When you start bringing subsurface foils (foilers) and supersurface(?) foils (wings on flying boats, kiteboards, even windsurfers) into the discussion, then you have left the realm of what is traditionally viewed (again in my opinion only) as planing.

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7 hours ago, unShirley said:

Disagree.  Having surfed for 55 years and sailed for 58, I find that much of the surfing skill is transferable to sailing downwind in the ocean.

I don't think we really disagree.  I wasn't trying to imply that board surfing skills didn't help sailing surfing.  I've sailed with Mark Soverel who had been a competitive surfer before designing sailboats and was known to be exceptional at surfing the boats he was racing.

I was referring to the fact that the water movement in the breaking shore waves and in the ocean waves is rather different so it seems likely that for some aspects (such as the initial catching of the wave) one has to "adjust" board surfing knowledge to best apply it to sailboats.  Given that I've never surfed, I surely could be wrong, but I'm quite sure about the differences in the underlying hydrodynamics.  Seems like catching a breaking wave has to be somewhat different from catching a non-breaking ocean wave.  Once you are locked in on the face, I can see where riding them might be very similar.

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6 hours ago, fastyacht said:

he hump is drag vs speed. Slowing down, you dont have to add powr---you experience bigger drag and decceleration.

Incidently, the same thing happens at mach 1.  A big energy hump to get over which decreases as flow over more and more bits of your craft go supersonic.  A really nice explanation here:

https://www.quora.com/Why-is-air-drag-the-strongest-at-about-Mach-1-but-significantly-weaker-beyond-that/answer/Kim-Aaron?ch=10&share=702a0f40&srid=uImx8U

Not that you'll ever be getting your melges 24 or cal 40 anywhere near mach 1, but the physics is not dissimilar in that the bow wave is a compression wave that actually starts some distance in front of the bow.  You are ostensibly pushing water forward, and that's what creates the bow wave.  

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In my own little fore brain, I define planing from the perspective of a flat bottom sinker >30 knots over the ground.  Then compare. (Gorge Rat fun) A little brutal, but on an intuitive level, it works.  Keep your head out of the boat!

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58 minutes ago, SVArcturus said:

But can you let the terminology creep to where a planing craft has nothing whatsoever on the surface?  I'm thinking foiling is a whole different animal than planing (unless the foil gets on the water surface, which is generally considered a bad move as I understand it).

Yup. Terminology is always a good way to drag out a discussion. Way up thread it was presented that planing is when the majority of the lifting force is from the dynamic action of the water vs. buoyancy. Foils underwater are providing hydrodynamic lift. So is a planing hull on the surface. Is there some third force keeping boats from sinking? Then whatever “fully planing” means…not even a 747 is fully supported by lift. There is some small amount of buoyancy in the game.

Riding the quarter wave of s bigger boat can be either slow or fast. There has been debate as to whether the following boat is parasitic to the boat creating the wave. 

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Wetted surface area being reduced by the hull form getting on the step reduces drag and changes the amount of force needed to keep the hull at the velocity it attained when achieving the step. If a wave instigates the transition to the step and the wave energy or gravity slide or whatever is necessary to keep the hull on the step then thats surfing. If a hull can stay on the step without wave assistance then that's planing. If a hull goes beyond its hull speed on a wave without reducing its wetted surface area significantly its serging and needs a lemon twist in its espresso.

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All I know, is that in spite of the title of his video - "Surfing a Moore 24"  this Moore 24 is definitely planing.  I'm sure many of you have seen this video, but still pretty cool footage.

 

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19 hours ago, 12 metre said:

Actually the J/24 came out in 1976 or maybe even later - early 1977.  Anyways, the Moore 24 and Santa Cruz 27 both predate the J by several years and are much better examples.  Could probably throw in some of John Spencers work from the 60's - although being kiwi, few people in NA would have been aware of what was going on down there.  Further back you could look at Black Soo by Van De Stadt from the 50's.  black_soo_drawing.jpg

Yeah, yeah, yeah. The question is not who was first. The question was when did it become the usual thing.

Here is a somewhat fuzzy picture of a plaque showing the profile of Kialoa II, best time winner of the 1966 Bermuda Race. You can just make out that she was built in 1964 with an attached keel, and modified in 1967 with a separate rudder. Even with the revision, she's not a fin keel yacht in the modern sense as Black Soo is. Captain Nat built a true fin keeler, but you can't say it became the norm back then, not did Black Soo convince everyone it was the right thing for an offshore yacht.

 

2021-06-15_09-43-53.png

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5 hours ago, fastyacht said:

Remember the old sayijg, "and the spray went to the spreaders!"  Thats it right there!

Spreaders are a bit higher than that.

I used to sail a late IOR 65 footer,  that when really wound up would push the main back to well inside the quarter with the bow wave hitting the back of the main.  I was usually a bit busy to check how close it got to the spreaders though.

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9 hours ago, 12 metre said:

All I know, is that in spite of the title of his video - "Surfing a Moore 24"  this Moore 24 is definitely planing.  I'm sure many of you have seen this video, but still pretty cool footage.

 

I had the luck and pleasure of doing that on an Olsen 40 which had a high performance rudder on it though it was a sunny day and the swells were much bigger. The seasoned drivers who did most of the steering from Half Moon Bay to Santa Cruz would orient the boat about 10 to 20 degrees higher than dead down and when they got the boat on the step and we started going faster than the waves and rig pressure fell by half they would go by the lee to keep close to the rum line and stay there mostly while steering back and forth a bit to try and stay on flatter water. When the wind pressure fell they would power up by steering back up and exposing more chute but if they could not stay on the step and were falling off they would make sure the boat was pointed down again so when the boat went from 18-20 knots of boatspeed down to 8-10 and the rig loaded up the boat would not round up or down.

I tried to steer for a bit and even with lots of time steering in conditions like that on a soling and an X-119, the steering on that Olsen with the hot rudder was so sensitive before I knew it I had gybed the main twice in quick order (at least I didn't crash it) and handed it back with a red face. Those guys had 1000's of miles on that boat. Very impressive. They were getting 20-40 second runs at high speed with 10 second or so regroups waiting for the next puff. I learned a lot on that race watching those guys. The boat was impressively stable by the lee going at its fastest speeds. They could steer the boat 10 degrees each side of DDW to stay on flat water going around the steeper swells. The tricky deal was making sure the boat was pointed at just the right apparent wind angle when it fell off the step and the rig loaded up. Once they got set up we never had to gybe because of all the DDW and by the lee sailing.

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14 hours ago, 12 metre said:

All I know, is that in spite of the title of his video - "Surfing a Moore 24"  this Moore 24 is definitely planing.  I'm sure many of you have seen this video, but still pretty cool footage.

IMHO the key here is the helmsman is doing a really good job picking a path between wave sets.  The concentration is intense.  

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On 6/14/2021 at 1:07 PM, JimC said:

The only real difficulty would be maintaining a constant speed in the reducing drag zone - say for harbour speed limits. The boat would be wanting to speed up all the time.

??? I've been in bays and even channels and the local authorities ignore your boatspeed as long as you seem under control whether racing or not.  The 5kn nighttime speed limit is waived for small harbor finish lines; you can rage in @ 15kn with a kite under observation and if you don't dump the kite, turn upwind and stow the main & meekly power to your slip they may come alongside and ask if you need assistance.

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1 hour ago, Spoonie said:

IMHO the key here is the helmsman is doing a really good job picking a path between wave sets.  The concentration is intense.  

Dodging short period waves by active steering is a completely different skill set and is effective even in light air upwind or downwind if it's choppy.  In big DW swells and high winds with benign wave patterns  the "surfing" possibilities arise and a good helmsman with the help of trimmers can really rage by "carving" on the swell.

Note the vid showed no active trim; in the vid conditions helm  reaction times are so short trimming is out of the question.  Hopefully some big time transoceanic racers can chime in about how to ride big swells when it's windy.

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7 hours ago, unShirley said:

No, a Dick Newick and John Olin Tremolino

Tremolino

It is a trimaran with a 23' main hull and a Hobie 16 mast, sails and hulls used for amas.

I really admired those when they came out. The idea of owning a Newick at such an affordable price was very enticing! Especially as I already owned a Hobie 16 in more-than-serviceable shape. My neighbor and I considered shipping to Spain and boat-bumming around the Med but I pointed out that the accommodations were seriously spartan. You tell me: can you even fuck in one? Certainly the females would be somewhat less than impressed...

As it was, we did several trips from Long Beach to Parson's Landing on the Hobie with a Davis hand-bearing compass taped to the side-beam and parts of a chart sandwiched between some mylar.

It pleases me that your boat fared well in between the Channel Islands and the mainland.

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6 hours ago, axolotl said:

Note the vid showed no active trim; in the vid conditions helm  reaction times are so short trimming is out of the question.  Hopefully some big time transoceanic racers can chime in about how to ride big swells when it's windy.

Hold on and hope? 

Judging by the volvo videos, the same way any of us ride big swells.  There's not a lot of active trim.  Occasionally one or two guys on the grinder ready but no apparent active trimming.

At a much smaller scale there's a nice video of Brendan Casey talking through the technique in a Laser. I like the laser videos because everything is over emphasised.  Here is Chris Nicholson talking through the technique on for a volvo 65 though. There's not lot of active trimming on any of the volvo videos even though Chris talks about it.  It's all helm.   It is worth noting though that Chris is an ex 18' skiff sailor.   I do wonder if it's that dinghy experience which really hones this skill because momentum isn't your friend.

The video of Brendan Casey is here:

I've only steered up to 47' in waves (a beach ball and coastal).  The technique on that was just the same; finding the flat spots and steering between them.  Keep the average speed up and you can buy more depth.  My (admittedly limited) experience has been the bigger the boat, the more subtle and forward thinking you need to be.

You know, IMHO it's like a lot of things in life.  Always have an exit plan... don't go into things without know how you're going to get out of them

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17 hours ago, Somebody Else said:

I really admired those when they came out. The idea of owning a Newick at such an affordable price was very enticing! Especially as I already owned a Hobie 16 in more-than-serviceable shape. My neighbor and I considered shipping to Spain and boat-bumming around the Med but I pointed out that the accommodations were seriously spartan. You tell me: can you even fuck in one? Certainly the females would be somewhat less than impressed...

As it was, we did several trips from Long Beach to Parson's Landing on the Hobie with a Davis hand-bearing compass taped to the side-beam and parts of a chart sandwiched between some mylar.

It pleases me that your boat fared well in between the Channel Islands and the mainland.

Nope. In fact, we nicknamed the boat the "coffin" because one had to pull all of your stuff out of the main hull in order to climb in and sleep.  And even then, one is restricted to sleeping on your back, you can't sleep on your side in the fetal position.  Even though I had a seriously sexy, adventurous and horny girlfriend, inside the main hull is one of the few places we never did it.

Back to this thread, the tremolino is a seriously fun surfing machine as are other Newicks that I have sailed on.  The tremolino also has a hard chined, flat section in the bottom under the cockpit.  One time, crossing from Pelican to SB in a small craft warning, at times it would get on top of a swell/whitecap and get up on a short plane on the flat section with both amas out of the water and a very fine spray coming off the main hull.  My crew and I would just look at each other and start laughing.  I have no idea how fast we were going, it was 1980 and the only nav equip I had was a compass and a wrist watch. We didn't even have a VHF radio. But I am guessing we were getting very close to the proverbial 20 kts? We made that trip in 2 hours, and the wind calmed down dramatically  inside the oil platforms.

Young, stupid good times.

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13 hours ago, Spoonie said:

Hold on and hope? 

Judging by the volvo videos, the same way any of us ride big swells.  There's not a lot of active trim.  Occasionally one or two guys on the grinder ready but no apparent active trimming.

At a much smaller scale there's a nice video of Brendan Casey talking through the technique in a Laser. I like the laser videos because everything is over emphasised.  Here is Chris Nicholson talking through the technique on for a volvo 65 though. There's not lot of active trimming on any of the volvo videos even though Chris talks about it.  It's all helm.   It is worth noting though that Chris is an ex 18' skiff sailor.   I do wonder if it's that dinghy experience which really hones this skill because momentum isn't your friend.

The video of Brendan Casey is here:

I've only steered up to 47' in waves (a beach ball and coastal).  The technique on that was just the same; finding the flat spots and steering between them.  Keep the average speed up and you can buy more depth.  My (admittedly limited) experience has been the bigger the boat, the more subtle and forward thinking you need to be.

You know, IMHO it's like a lot of things in life.  Always have an exit plan... don't go into things without know how you're going to get out of them

Nicholson's comment about not looking for the best single ride, but maintaining speed and looking for the best exit is solid advice.  I've always tried to look for the "low spot" ahead and use it.  I wish I was better at that. 

The primary driving goal is to not get loaded up in a trough and struggle to not round up on the wave you just slid down, keeping the boat under the rig.  Balancing the helm and setting up the trim for 15° arcs in either direction is the key.   The ultimate goal for decently fast offshore boats is to jump over the crest of the wave in front.  Every wave is different and finding the low spot or the flat spot is the way to do that.  Jumping a wave train is a gain that you never lose.

The real magic drivers figure out how to steadily take opportunities to work low a few degrees at a time without losing speed and getting stuck in a trough.  I have a tendency to work too deep too often and VMG suffers.  

 

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20 hours ago, Spoonie said:

 

 

The video of Brendan Casey is here:

 

 

The second video is very cool for me. My very first sail was in a Laser just to the right of where the screen ends. The location the video was taken, off Drano Lake, is where I'd take my Santana 22 to surf past Swell City on the way back to Hood River.

 

Common Columbia Gorge condition.

river-swell_orig.jpg

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On 6/10/2021 at 8:55 PM, Borracho said:

Have them watch for kelp patches while back there. I recall a collision with kelp ahead of a very rare black squall was the demise of the Hotfoot down in Monterey. Still on the bottom I assume. Many years ago. 

Yes, nobody likes pitchpoling.

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Sooo... We now get to throw swell into the mix. Unless I missed any earlier posts, most of us have been relating our past experiences, mathematical knowledge, formulas & whatnot.  There have been references to three dimensional thought, however many of us are thinking in two dimensional terms, flatwater or implied one directional swells that rarely exist in open/larger waters. If we consider multiple underlying swell directions, size, and make note of tides and currents,.... Bingo!! (Rise & Fall). we bring at least a significant element of gravity into play. 

I'm interested in what ways sea state, in reasonable to good conditions helps, hurts, surfing planing on a keelboat.

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1 hour ago, Moore Play said:

Sooo... We now get to throw swell into the mix. Unless I missed any earlier posts, most of us have been relating our past experiences, mathematical knowledge, formulas & whatnot.  There have been references to three dimensional thought, however many of us are thinking in two dimensional terms, flatwater or implied one directional swells that rarely exist in open/larger waters. If we consider multiple underlying swell directions, size, and make note of tides and currents,.... Bingo!! (Rise & Fall). we bring at least a significant element of gravity into play. 

I'm interested in what ways sea state, in reasonable to good conditions helps, hurts, surfing planing on a keelboat.

One of my first lessons regarding vmg and swells and surging, surfing etc was you had to throw the polar charts out the window when on a sausage leg. If you tried to stay on polar wind angles you would be spanked by those working down when they had pressure and a swell. Sometimes you can work the whole sail plan. Pole forward, sheet in, pump the main once, get on the swell, pole back, sheet out, steer down and ride as long as you can. Rinse, repeat. One boat doing this down an entire leg will crush a boat not doing it in borderline conditions especially. Some think you can help get the boat surfing or on the step sooner with a rudder pump. Certainly feels that way to me. 

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1 hour ago, Moore Play said:

Sooo... We now get to throw swell into the mix. Unless I missed any earlier posts, most of us have been relating our past experiences, mathematical knowledge, formulas & whatnot.  There have been references to three dimensional thought, however many of us are thinking in two dimensional terms, flatwater or implied one directional swells that rarely exist in open/larger waters. If we consider multiple underlying swell directions, size, and make note of tides and currents,.... Bingo!! (Rise & Fall). we bring at least a significant element of gravity into play. 

I'm interested in what ways sea state, in reasonable to good conditions helps, hurts, surfing planing on a keelboat.

So... I've somewhat found this thread painful to read.  I don't know why I'm still reading it. But here we go...

There are three fundamental hydrostatic forces on a sailboat you need to worry about.  The amount of water it pushes downwards, the amount of water it pushes forward, and the surface friction of the water across the hull surface. 

Newtons third law, any water the boat pushes, will push back in the opposite direction.  To which We basically have two vectors: One pushing up, and one pushing backwards.  If the one pushing up reduces the one pushing backwards (through hull design or whatever), the boat (likely) accelerates. The boat will start to plane

Regardless of how that water gets to be pushing upwards (because the boat is falling or through relative velocity) the impact is the same. All these discussions of surfing, planning, waves, swells, currents or whatever doesn't matter. Forget about how a boat got into whatever state it is in, and look very purely at that exact instance what are those two vectors.  Everything else you might want to know about surfing, planing, or sailing in waves can be derived from this little thought experiment.

The question then purely becomes, is there enough upwards force to reduce the backwards force.  If you stuff your nose into the back of a wave, the answer will invariably be no.  In the discussion on wave technique, the fundamental principal there isn't about maximising your time falling off waves, it's about minimising the time you spend stuffing your nose into them.

Partly why I posted that hobie cat doing 25knots, because hobie cats don't plane.  There is a little, but virtually no upward force due to velocity on a hobie cat hull.  You sure as nuts know about it when you stick your leeward nose into the trough though. 

 

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15 hours ago, Chris in Santa Cruz, CA said:

One of my first lessons regarding vmg and swells and surging, surfing etc was you had to throw the polar charts out the window when on a sausage leg. If you tried to stay on polar wind angles you would be spanked by those working down when they had pressure and a swell. Sometimes you can work the whole sail plan. Pole forward, sheet in, pump the main once, get on the swell, pole back, sheet out, steer down and ride as long as you can. Rinse, repeat. One boat doing this down an entire leg will crush a boat not doing it in borderline conditions especially. Some think you can help get the boat surfing or on the step sooner with a rudder pump. Certainly feels that way to me. 

What's a "pole"?

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Thank you all!! 

I've heard  surfing and planing, thrown around for a long time, big grey area for me, and I figured if anybody had or knew of actual/measurable, distinction between the two, you or they they might be here.

I guess it's like porn,.. You can't really define it,...But, you know it when you see it!! :D Thanks Again for all your responses.

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8 hours ago, Moore Play said:

Thank you all!! 

I've heard  surfing and planing, thrown around for a long time, big grey area for me, and I figured if anybody had or knew of actual/measurable, distinction between the two, you or they they might be here.

I guess it's like porn,.. You can't really define it,...But, you know it when you see it!! :D Thanks Again for all your responses.

Actually, it is really easy to define. 
 

surfing is the act of falling forwards off a wave.  Planing is a hydrodynamic state.  
 

The point is not to get hung up on it.  A boat that is planing is planing, regardless of how it got into that state, including whether it got there by surfing.  It is perfectly reasonable for a boat to fall off the plane when it stops surfing.  That doesn't mean it wasn't planing.
 

where the confusion lies is when you try to make it an either/or thing when it isn't.  They are two seperate things that may happen to overlap through consequence or coincidence.

clear as mud?

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