The sky is bright blue, the temperature is in a comfortable range, and perhaps most importantly, the wind is blowing nicely. Up goes the main and you are sailing. Off goes the engine. The genoa unfurls nicely and begins fill. All you can hear is the sound of water rushing past the hull. The lee rail is getting perilously close to the water, but the boat is in a groove. You feel like you are flying. Sailing doesn't get any better than this. Taking your eyes off the sails for a moment, you look at the knotmeter and it's reading 7 kts -- or about the speed you jog. How can this be? You know this is about as fast as your boat can go, yet it feels like you are cutting through the water much faster. Later that night you pick up one your many sailing magazines and read about how someone clocked a few 200+ mile days on a recent cruise -- an average speed of 8-1/2 knots or so. A few pages later, an article shows Group Finot racers surfing along at 12-15 kts in some exotic race. And you haven't even gotten to the story about those experimental multihulls doing 25 knots. What's been your experience with speed? Tell us how you pegged the knot meter, and how you did it. And don't forget to take the Quick Quiz on the home page. (Discussion topic and quiz submitted by Warren Milberg)
- Status
Speed freak(Oh Yeah)
It was an overnight distance race a few years ago. The breeze had built to about 25kts. The seas had developed into long rollers, quite unusual for LIS. We were on the leg home at about 0300hrs. Broad reaching with a chute up. Boat speed at this point is totally dependent on the driver surfing down the backside of rollers and mantaining it for as long as possible. As the bow starts to lift, you head down and prepare for the next one. The crew was watching the boat speed repeater on the bulkhead, 8.7...9.3..10.6 then back down into the high 7's. Here comes the next this time to 11.5 and someone said "com'on 12". A couple later and 12.1. The boat was flying, it was outragous, what a sensation. The miles flew by and we were across the finish line in record time.
It was an overnight distance race a few years ago. The breeze had built to about 25kts. The seas had developed into long rollers, quite unusual for LIS. We were on the leg home at about 0300hrs. Broad reaching with a chute up. Boat speed at this point is totally dependent on the driver surfing down the backside of rollers and mantaining it for as long as possible. As the bow starts to lift, you head down and prepare for the next one. The crew was watching the boat speed repeater on the bulkhead, 8.7...9.3..10.6 then back down into the high 7's. Here comes the next this time to 11.5 and someone said "com'on 12". A couple later and 12.1. The boat was flying, it was outragous, what a sensation. The miles flew by and we were across the finish line in record time.
I'm with Alan
Now our finish time in the Mac wasn't the best, but we had some great spinnaker runs on Sunday and Monday. Just as he described, chute up, just over 20 knots, 3-5 footers rolling in from behind. My wife had asked earlier what 'hull speed' was on the boat, and now was asking "How can we be doing 10.6?" I only answered with a grin! It does feel great with the water passing by that fast as you head down the face of the wave. But when they are coming in just at an angle, a 4 hour watch at the wheel can be exhausting as well as exhilirating. T J
Now our finish time in the Mac wasn't the best, but we had some great spinnaker runs on Sunday and Monday. Just as he described, chute up, just over 20 knots, 3-5 footers rolling in from behind. My wife had asked earlier what 'hull speed' was on the boat, and now was asking "How can we be doing 10.6?" I only answered with a grin! It does feel great with the water passing by that fast as you head down the face of the wave. But when they are coming in just at an angle, a 4 hour watch at the wheel can be exhausting as well as exhilirating. T J
Neverending confusion about what "hull speed" is
I'm sure this topic is going to fill up with a lot of comments from people believing that the "hull speed" calculated for their keelboat is some kind of ceiling. My understanding is that "hull speed" is the speed at which the hull is travelling at its maximal level of efficiency through the water; if you are travelling faster than hull speed, assuming the movement is not an "over ground" effect measured by gps as you travel with current, it means a greater amount of energy is required to sustain that speed than was required to get you to the hull speed. There is a zone between the "hull speed" and broaching where the boat can move if a great deal more energy is added to the system (such as gale force wind or being towed by a fast-moving tug...) So if your hull speed is calculated at 6 knots and you're travelling at 8 or even 12, it means a lot more wind power is being used to move your hull than was required to get you to 6. It doesn't mean you're doing the impossible or that your knotmeter is broken...
I'm sure this topic is going to fill up with a lot of comments from people believing that the "hull speed" calculated for their keelboat is some kind of ceiling. My understanding is that "hull speed" is the speed at which the hull is travelling at its maximal level of efficiency through the water; if you are travelling faster than hull speed, assuming the movement is not an "over ground" effect measured by gps as you travel with current, it means a greater amount of energy is required to sustain that speed than was required to get you to the hull speed. There is a zone between the "hull speed" and broaching where the boat can move if a great deal more energy is added to the system (such as gale force wind or being towed by a fast-moving tug...) So if your hull speed is calculated at 6 knots and you're travelling at 8 or even 12, it means a lot more wind power is being used to move your hull than was required to get you to 6. It doesn't mean you're doing the impossible or that your knotmeter is broken...
Heeling Can increase Hull Speed
With overhangs heeling increases waterline length. But hull speed is real especially in flat water. Surfing down waves you can escape hull speed as long as the wave lasts. But with the turbulance associated with waves I take my indicated speed with a grain of salt. Supposedly we have briefly hit over 9 knots in our pearson 323. The fastest that I've ever sailed was on my windsurfer. It was more like flying than sailing as my body weight was completely supported by the sail and I used my feet only for steering. A close second was on my Laser. Both of these "sailboats?" have pllanning hulls so they have no hull speed. The biggest problem that I had with the Laser was that it would bury it's bow into the back of a wave and pitchpole. I could usually avoid this problem but every now and then inattention of a weird wave pattern would put me into the water. Beam reaching in 25 knots on a laser or sailboard has got to be some of the most exciting sailing possible. Tom
With overhangs heeling increases waterline length. But hull speed is real especially in flat water. Surfing down waves you can escape hull speed as long as the wave lasts. But with the turbulance associated with waves I take my indicated speed with a grain of salt. Supposedly we have briefly hit over 9 knots in our pearson 323. The fastest that I've ever sailed was on my windsurfer. It was more like flying than sailing as my body weight was completely supported by the sail and I used my feet only for steering. A close second was on my Laser. Both of these "sailboats?" have pllanning hulls so they have no hull speed. The biggest problem that I had with the Laser was that it would bury it's bow into the back of a wave and pitchpole. I could usually avoid this problem but every now and then inattention of a weird wave pattern would put me into the water. Beam reaching in 25 knots on a laser or sailboard has got to be some of the most exciting sailing possible. Tom
Hull speed etc.
Here's how it all works. Heavy displacement keelboats usually can't get their noses out of the water. In that case: their maximum speed relative to the water is limited by the speed of a standing wave that begins at their bow and ends at their stern. The formula for that speed - called hull speed - is 1.34 * sqrt(length of boat at the waterline). So a boat that's 25 feet at the waterline has a maximum speed of 6.7 knots. At that speed, she's sitting in a big wave that begins at her bow and ends at her stern and she can't 'jump' out of it. (Usually, 25 feet at the waterline is a boat that's longer than 25 feet overall - the bow slants aft towards the water.) If a boat is longer at the waterline, she can go faster. That's why you see racing boats whose bows go almost vertically down into the water, and whose transoms slant backwards. They're a little longer at the waterline: they can go a little faster. This is speed relative to the water. If the current's flowing with you, you're going faster relative to the ground, for example relative to the shore (add the speed of the current). If the current's against you, subtract the speed of the current. All this began with the assumption that you can't get your nose out of the water. A lot of sailboats can - via either planing (bow coming upwards - which you can influence, for example, by having the crew sit at the transom) or surfing (riding on top of the waves). When the bow is out of the water, the hull speed limitation vanishes and there is no theoretical limit to speed (governed instead by boat design and consequent friction vs forward thrust). Modern sailboats often have their foreward hulls designed to come up and ride over the water (like speedboats do). Another way to avoid the hull speed limitation is to have a boat that sits on the water rather than in it. This is what multihulls do: essentially, they're skimming over the water and again the hull speed limitation does not apply. What a lot of annoying theoretical stuff. That should make me thoroughly unpopular! Better to sail and enjoy the knotmeter: better yet, just sail and listen to the sound of the water as you drive through it, than think about all these equations. But I guess I'm a nerd at heart. Dick
Here's how it all works. Heavy displacement keelboats usually can't get their noses out of the water. In that case: their maximum speed relative to the water is limited by the speed of a standing wave that begins at their bow and ends at their stern. The formula for that speed - called hull speed - is 1.34 * sqrt(length of boat at the waterline). So a boat that's 25 feet at the waterline has a maximum speed of 6.7 knots. At that speed, she's sitting in a big wave that begins at her bow and ends at her stern and she can't 'jump' out of it. (Usually, 25 feet at the waterline is a boat that's longer than 25 feet overall - the bow slants aft towards the water.) If a boat is longer at the waterline, she can go faster. That's why you see racing boats whose bows go almost vertically down into the water, and whose transoms slant backwards. They're a little longer at the waterline: they can go a little faster. This is speed relative to the water. If the current's flowing with you, you're going faster relative to the ground, for example relative to the shore (add the speed of the current). If the current's against you, subtract the speed of the current. All this began with the assumption that you can't get your nose out of the water. A lot of sailboats can - via either planing (bow coming upwards - which you can influence, for example, by having the crew sit at the transom) or surfing (riding on top of the waves). When the bow is out of the water, the hull speed limitation vanishes and there is no theoretical limit to speed (governed instead by boat design and consequent friction vs forward thrust). Modern sailboats often have their foreward hulls designed to come up and ride over the water (like speedboats do). Another way to avoid the hull speed limitation is to have a boat that sits on the water rather than in it. This is what multihulls do: essentially, they're skimming over the water and again the hull speed limitation does not apply. What a lot of annoying theoretical stuff. That should make me thoroughly unpopular! Better to sail and enjoy the knotmeter: better yet, just sail and listen to the sound of the water as you drive through it, than think about all these equations. But I guess I'm a nerd at heart. Dick
Dick I have to disagree
with the multi hull portion of your explanation. I sailed small cats in the past (Hobies, Sea Sprays etc) and not one of then planed no matter how much speed or how much wind was at play. There was simply not enough surface area on one hull to support the weight of the boat and crew plus whatever other forces were at play. If you look at the hulls on a Hobie 16 for example, they are essentially knife edged on the bottom. Ther is no way those babies are gonna plane. If someone here has had a Hobie 16 on a plane I would love to hear the details.
with the multi hull portion of your explanation. I sailed small cats in the past (Hobies, Sea Sprays etc) and not one of then planed no matter how much speed or how much wind was at play. There was simply not enough surface area on one hull to support the weight of the boat and crew plus whatever other forces were at play. If you look at the hulls on a Hobie 16 for example, they are essentially knife edged on the bottom. Ther is no way those babies are gonna plane. If someone here has had a Hobie 16 on a plane I would love to hear the details.
Dick I think that you are wrong
About multihulls. They are two monohulls built together. A multihull is fast because it is light. The lighter a boat (all things being equal) the faster it can go especially in lighter winds. My Pearson has 2 tons of lead in the keel to provide stability. A cat doesn't need any ballast for stability. In my experience conditions where hull speed is the limiting factor are relatively rare. Wetted surface area is usually the limiting factor. The more weight the more wetted surface the more drag. Thats why a full keeled boat is usually much slower than a fin keeled boat. A full keel has so much wetted area that it takes a pretty good breeze to overcome the drag. Tom
About multihulls. They are two monohulls built together. A multihull is fast because it is light. The lighter a boat (all things being equal) the faster it can go especially in lighter winds. My Pearson has 2 tons of lead in the keel to provide stability. A cat doesn't need any ballast for stability. In my experience conditions where hull speed is the limiting factor are relatively rare. Wetted surface area is usually the limiting factor. The more weight the more wetted surface the more drag. Thats why a full keeled boat is usually much slower than a fin keeled boat. A full keel has so much wetted area that it takes a pretty good breeze to overcome the drag. Tom
Twice, two different ways
We pegged an old Kenyon analog speedo at 12knots on a wooden Sparkman & Stevens 40' sloop racing to Halifax. The course was dead downwind in about 25 knots of breeze, and the rollers had built to about 10 to 12 feet. A wave would lift the stern and we'd roar down its face almost dipping the boom as the speedo would zip to the max - twelve knots - and stay there for about ten to fifteen seconds until the wave passed under us or we reached the trough. Then the spinnaker pole would dip down (but not in) as we rolled the other way to catch the next one. We did this for what must have been at least a day (24hours) or more. We managed to run over a sleeping seagull in the dark- quite a spluttering, flapping, suprised squawk. Olin Sevens seemed a bit skeptical about it when I mentioned our speed to him, but we did win that race. The second episode involves another race about three years ago. This annual club race is about 80 miles long, and starts after sundown. A 30-knot Northerly was clearing the remnants of a tropical storm. For us, this meant an offshore breeze with no waves to speak of. After rounding the first mark, the course was a broad reach for about 35 miles. We were trying to keep up with a relatively new and well-equipped J/120, so we put up the genoa. Not enough. We set the 1.5 oz spinnaker, and started to fly through the flat water. We couldn't see it in the dark, (no moon) but we could hear the bow wave shooting out near the end of the boom. We kept the genoa up, since the boat seemed to balance well, and we didn't want to lose power if we had to douse the 'chute. The GPS showed us doing 13.1 knots for about an hour. Our prime competitor blew out his asymetcical, but set another one before we could catch him. Maybe next time~!
We pegged an old Kenyon analog speedo at 12knots on a wooden Sparkman & Stevens 40' sloop racing to Halifax. The course was dead downwind in about 25 knots of breeze, and the rollers had built to about 10 to 12 feet. A wave would lift the stern and we'd roar down its face almost dipping the boom as the speedo would zip to the max - twelve knots - and stay there for about ten to fifteen seconds until the wave passed under us or we reached the trough. Then the spinnaker pole would dip down (but not in) as we rolled the other way to catch the next one. We did this for what must have been at least a day (24hours) or more. We managed to run over a sleeping seagull in the dark- quite a spluttering, flapping, suprised squawk. Olin Sevens seemed a bit skeptical about it when I mentioned our speed to him, but we did win that race. The second episode involves another race about three years ago. This annual club race is about 80 miles long, and starts after sundown. A 30-knot Northerly was clearing the remnants of a tropical storm. For us, this meant an offshore breeze with no waves to speak of. After rounding the first mark, the course was a broad reach for about 35 miles. We were trying to keep up with a relatively new and well-equipped J/120, so we put up the genoa. Not enough. We set the 1.5 oz spinnaker, and started to fly through the flat water. We couldn't see it in the dark, (no moon) but we could hear the bow wave shooting out near the end of the boom. We kept the genoa up, since the boat seemed to balance well, and we didn't want to lose power if we had to douse the 'chute. The GPS showed us doing 13.1 knots for about an hour. Our prime competitor blew out his asymetcical, but set another one before we could catch him. Maybe next time~!
Speed?
Who really cares about speed on a sailboat. If speed was your concern then you would have joined the PB's. I am always amazed and thrilled any time I am over 6kt and sailing. My goal is to always get out of the river, shut down the engine and enjoy the peace. I am not in a hurry and feel that my boat and I are one when we sail. I have held 8-9 knts with a lot of work and that is not what sailing is about in my book. But to each his own since we will be out there sailing when the last power boat runs out of fuel.
Who really cares about speed on a sailboat. If speed was your concern then you would have joined the PB's. I am always amazed and thrilled any time I am over 6kt and sailing. My goal is to always get out of the river, shut down the engine and enjoy the peace. I am not in a hurry and feel that my boat and I are one when we sail. I have held 8-9 knts with a lot of work and that is not what sailing is about in my book. But to each his own since we will be out there sailing when the last power boat runs out of fuel.
13 knots
...on a Hobie 16 this weekend. (This according to my cousin following in his runabout.) So what's the hull speed for a 16 foot waterline? Do catamarans plane? Not sure. The Hobie 16 hull does have flat sides, and with couple degrees of heel, there *may* be a slight upward force generated. On the other hand, it definitely slices thru the waves as opposed to riding over them, which is what a planing boat does. As far as hull speed is concerned: As I understand, it's only a "practical limit" for some boats. The power required to achieve each unit of speed above hull speed increases exponentially. Fitting that source of power onto the boat is the problem. If enough propulsive force can be applied, any solid shape can be made to skim across the water surface. Put a rocket on a full keel displacement hull. (Of course, control is another "practical limit". It'd take some pretty sophisticated controls to keep the diplacement hull going straight and upright.)
...on a Hobie 16 this weekend. (This according to my cousin following in his runabout.) So what's the hull speed for a 16 foot waterline? Do catamarans plane? Not sure. The Hobie 16 hull does have flat sides, and with couple degrees of heel, there *may* be a slight upward force generated. On the other hand, it definitely slices thru the waves as opposed to riding over them, which is what a planing boat does. As far as hull speed is concerned: As I understand, it's only a "practical limit" for some boats. The power required to achieve each unit of speed above hull speed increases exponentially. Fitting that source of power onto the boat is the problem. If enough propulsive force can be applied, any solid shape can be made to skim across the water surface. Put a rocket on a full keel displacement hull. (Of course, control is another "practical limit". It'd take some pretty sophisticated controls to keep the diplacement hull going straight and upright.)
13 on a Hobie
Well, hull speed for a 16 foot boat is around 5 knots so there's no question about it: if you're doing 13 knots, you're planing. I've attached a link that's pretty interesting on the history and theory regarding multihulls. Yes, you could have a rocket powered boat and it would go faster than the hull speed. If it did, though, it would bounce in and out of the standing wave. (If you tow a dinghy, you'll see it doing exactly that when your sailboat gets up to speed. Or try towing a flat piece of wood behind your boat: same thing) You'd need a heck of a lot of sail power to make a keelboat bounce through the water like a speedboat! Dick
Well, hull speed for a 16 foot boat is around 5 knots so there's no question about it: if you're doing 13 knots, you're planing. I've attached a link that's pretty interesting on the history and theory regarding multihulls. Yes, you could have a rocket powered boat and it would go faster than the hull speed. If it did, though, it would bounce in and out of the standing wave. (If you tow a dinghy, you'll see it doing exactly that when your sailboat gets up to speed. Or try towing a flat piece of wood behind your boat: same thing) You'd need a heck of a lot of sail power to make a keelboat bounce through the water like a speedboat! Dick
12.6 Knots
We had a 50' Beneteau chartered out of Annapolis. WQE sailed South, rail in the water, beating ourself to death, then when we trurned out of the bay towards St Michaels we were on a beam reach, 20 plus knots of wind and man did we take off. A very steady 12.4 to 12.6. Smooth and fairly flat. What a thrill. am
We had a 50' Beneteau chartered out of Annapolis. WQE sailed South, rail in the water, beating ourself to death, then when we trurned out of the bay towards St Michaels we were on a beam reach, 20 plus knots of wind and man did we take off. A very steady 12.4 to 12.6. Smooth and fairly flat. What a thrill. am
You Might be Right about a Hobie
I was thinking about a cruising catamaran on my dock when talking about a catamarn being two monohulls conected. Hobie's have asymetric hulls so they might plane. Plus there isn't much to a Hobie except the sails and hulls so light weight.
I was thinking about a cruising catamaran on my dock when talking about a catamarn being two monohulls conected. Hobie's have asymetric hulls so they might plane. Plus there isn't much to a Hobie except the sails and hulls so light weight.
cats do sail fast
With my Benteau 331 I considered 7.5 knots as top speed unless surfing where I might see a moment at 8.5. Having switched to a PDQ32 catamaran I now see 9 and 10 knots routinely however it doesn't feel fast as you don't feel the speed in a cat the way you do in a mono. When the wind gets up in the high teens or better the cat will continue to climb however I prefer to reef before things get too exciting so I usually top out around 12 knots.
With my Benteau 331 I considered 7.5 knots as top speed unless surfing where I might see a moment at 8.5. Having switched to a PDQ32 catamaran I now see 9 and 10 knots routinely however it doesn't feel fast as you don't feel the speed in a cat the way you do in a mono. When the wind gets up in the high teens or better the cat will continue to climb however I prefer to reef before things get too exciting so I usually top out around 12 knots.
Just a week ago....
We clocked 7.55 on my GPS in San Francisco Bay. I have a 79 Mac 25. We were flyin' Two of us, and hardly any gear. Winds were blowing about 14-15 knots. What a ride!!!
We clocked 7.55 on my GPS in San Francisco Bay. I have a 79 Mac 25. We were flyin' Two of us, and hardly any gear. Winds were blowing about 14-15 knots. What a ride!!!
Dave W.
I had a Hobie back in the 80s. Yes, they can and do "plane", to a certain extent. If a hull is actually displacing less water than the weight of the boat, then is is "planing", which is to say that is is not, at that point, a displacement hull, but a "planing hull", and it may be what you might call a semi-plane, not necessarily a fully planing hull like a speedboat has. As for the Hobie and the hull shape, what you are missing is that when at full speed, and/or flying a hull, the angle of attack for the hull on the water is not with that knife edge down, but with the side of the pontoon down in the water, a flat surface, that due to the design and the way that the boat rides when "heeled over" like that, does in fact give a lot of "lift" to the hull. Hobies, and other cats have been clocked at over 30 mph, and believe me, they are planing. Here is the latest boat from them. Background: When was the last time you went 35 MPH or more in a sailboat? With the Hobie TriFoiler, your wildest dreams of speed can come true. The TriFoiler is quite simply, the most amazing sailing machine on the water today. Take the pilot's seat in the center cockpit with all the sail and foil adjustments on the control panel in front of you and you're off. All it takes is 12 knots of wind for the three self-adjusting hydrofoils to lift off and you're flying! Check your speed on the built-in speedometer as you streak past everything else on the water while controlling your course with the steering pedals.
I had a Hobie back in the 80s. Yes, they can and do "plane", to a certain extent. If a hull is actually displacing less water than the weight of the boat, then is is "planing", which is to say that is is not, at that point, a displacement hull, but a "planing hull", and it may be what you might call a semi-plane, not necessarily a fully planing hull like a speedboat has. As for the Hobie and the hull shape, what you are missing is that when at full speed, and/or flying a hull, the angle of attack for the hull on the water is not with that knife edge down, but with the side of the pontoon down in the water, a flat surface, that due to the design and the way that the boat rides when "heeled over" like that, does in fact give a lot of "lift" to the hull. Hobies, and other cats have been clocked at over 30 mph, and believe me, they are planing. Here is the latest boat from them. Background: When was the last time you went 35 MPH or more in a sailboat? With the Hobie TriFoiler, your wildest dreams of speed can come true. The TriFoiler is quite simply, the most amazing sailing machine on the water today. Take the pilot's seat in the center cockpit with all the sail and foil adjustments on the control panel in front of you and you're off. All it takes is 12 knots of wind for the three self-adjusting hydrofoils to lift off and you're flying! Check your speed on the built-in speedometer as you streak past everything else on the water while controlling your course with the steering pedals.
- Status