Sea Anchor versus drogue for multihull

[fxykty]

Originally Posted by Sail Houston

Another point on the use of a drogue of any kind is the intended application of the drogue itself. There are three ways I categorize the use of a drogue on a Cat during heavy weather.



Slow me down

Increase Lateral Stability and Steerage

Reduce Pitching



Each of the above requires a different setup and towed length.



Something also to mention when talking about Storm sailing on a Catamaran is the use of a small wing sail or chute. Think windsurfing sail except much smaller. During a storm. They allow you to change your Center of effort drastically as needed. Can sail at a very high apparent wind angle safely. Place the lift at the bow to prevent pitching(both safe and comfortable), and allow the tandem use of a drogue to give you a very flat ride. The only real downside is if running it from a halyard instead of the sprit depending on the desired effect, I would recommend a running back of some kind.

Please clarify your experience and rationale for your suggestions, as what you are saying is new and AFAIK untested.

Of the three reasons you cite for using a drogue, only the first makes universal sense for catamarans generally. I’m not sure what you mean by lateral stability and steering? I’m also not sure what you mean by reducing pitching?

Regarding the wing sail, do you mean a kite sail (horizontal) or a windsurfer sail (adjustable angle). With either, how does this work in conjunction with an existing rig? And why bother - why not just use a storm jib? Any catamaran that is intended for use in heavy weather (F9 and above) will not be so fine in the ends that you need a special sail to keep from pitching end over end - slowing down will suffice.

[Sail Houston]

Originally Posted by fxykty

Please clarify your experience and rationale for your suggestions, as what you are saying is new and AFAIK untested.

Of the three reasons you cite for using a drogue, only the first makes universal sense for catamarans generally. I’m not sure what you mean by lateral stability and steering? I’m also not sure what you mean by reducing pitching?

Regarding the wing sail, do you mean a kite sail (horizontal) or a windsurfer sail (adjustable angle). With either, how does this work in conjunction with an existing rig? And why bother - why not just use a storm jib? Any catamaran that is intended for use in heavy weather (F9 and above) will not be so fine in the ends that you need a special sail to keep from pitching end over end - slowing down will suffice.

Experience. Unlimited tonnage master with large tonnage sail endorsement. If by new you mean not from a book that previous posters were talking about last published in the early 1900s about dumping oil in the water to break surface tension then yes these are new ideas. However I have used all of the above techniques to deliver many boats across every ocean without issue.

As mentioned lateral stability is the stability of the vessel as it travels through the water and resists a yawing motion. When in large following waves catamarans tend to surf down waves and yaw from side to side. Many people that set a drogue do so only to slow the boat down and not correct for the yawing effect. This tends to make the catamaran start to surf then have the wave pass over the hull then the hull sinks in a trough then do it again. This is very uncomfortable to ride in and can still find you sideways with waves on the beam if you are not careful. Setting the drogue to the proper length as a function of the waveform created by the displacement of the hulls going through the water under different conditions allows you to prevent sinking in the trough altogether. This leads to a much safer ride condition.

Pitching is the motion of the vessel to rock from bow to stern. By dramatically changing your applied center of effort you can effectively make your lever arm so long that you virtually stop pitching altogether during a heavy weather transit. I was never suggesting that you were going to pitch end for end. My point was for long-term ride comfort and reduced rig fatigue in heavy air conditions.

The wing sail as mentioned is not to prevent the bow from plowing heavy seas by lifting or something. The point is to move the center of effort to change the stability of the vessel. The largest complaint most people have against catamarans is that they have TOO much stability. The more stability a vessel has the faster the motion to correct any input. As an example, a cruise ship has very little stability because they are trying to increase the roll period of the vessel for an extremely long time. A cruise ship has a very tiny righting arm. In contrast, a sailing catamaran has a huge amount of stability. One way of safely reducing that stability is running a wing/kite sail solo very high up and forward while running a drogue behind you. In doing so you effectively are creating a huge long lever arm with a roll center very high in the air that is completely adjustable based on the conditions. This acts to greatly slow down the motions on the catamaran in heavy conditions to reduce wear on both vessel and crew.

[fxykty]

Originally Posted by Sail Houston

Experience. Unlimited tonnage master with large tonnage sail endorsement. If by new you mean not from a book that previous posters were talking about last published in the early 1900s about dumping oil in the water to break surface tension then yes these are new ideas. However I have used all of the above techniques to deliver many boats across every ocean without issue.

You have no history on this forum nor information in your biography so please provide relevant experience so that we all, or perhaps it is just me, can understand the basis for which you are making your suggestions. And by ‘new’ I don’t mean since some published book but rather from accepted modern storm tactics for catamarans - kite sails are not part of that AFAIK.

Originally Posted by Sail Houston

As mentioned lateral stability is the stability of the vessel as it travels through the water and resists a yawing motion. When in large following waves catamarans tend to surf down waves and yaw from side to side. Many people that set a drogue do so only to slow the boat down and not correct for the yawing effect. This tends to make the catamaran start to surf then have the wave pass over the hull then the hull sinks in a trough then do it again. This is very uncomfortable to ride in and can still find you sideways with waves on the beam if you are not careful. Setting the drogue to the proper length as a function of the waveform created by the displacement of the hulls going through the water under different conditions allows you to prevent sinking in the trough altogether. This leads to a much safer ride condition.

I understand that setting a drogue to proper length is based on ensuring it stays in the same relative part of the wave as your boat - further back in long period waves and closer in short period waves. This is less important with a series drogue as long as it is at least as long as one wave period.

Regarding yawing from lack of steerage, that’s avoided by not slowing too much and helped by setting a drogue with a bridle to either stern. That’s standard practice.

But what are you referring to when you write “prevent sinking in the trough altogether”? Do you mean travel at the same speed as the waves to avoid falling into the troughs? Doesn’t that mean travelling at very high speeds to stay on the top of a single wave? If that’s the plan, then why use a drogue? I’m obviously missing something here.

Originally Posted by Sail Houston

Pitching is the motion of the vessel to rock from bow to stern. By dramatically changing your applied center of effort you can effectively make your lever arm so long that you virtually stop pitching altogether during a heavy weather transit. I was never suggesting that you were going to pitch end for end. My point was for long-term ride comfort and reduced rig fatigue in heavy air conditions.



The wing sail as mentioned is not to prevent the bow from plowing heavy seas by lifting or something. The point is to move the center of effort to change the stability of the vessel. The largest complaint most people have against catamarans is that they have TOO much stability. The more stability a vessel has the faster the motion to correct any input. As an example, a cruise ship has very little stability because they are trying to increase the roll period of the vessel for an extremely long time. A cruise ship has a very tiny righting arm. In contrast, a sailing catamaran has a huge amount of stability. One way of safely reducing that stability is running a wing/kite sail solo very high up and forward while running a drogue behind you. In doing so you effectively are creating a huge long lever arm with a roll center very high in the air that is completely adjustable based on the conditions. This acts to greatly slow down the motions on the catamaran in heavy conditions to reduce wear on both vessel and crew.

Intriguing, it sounds like you are suggesting to fly a kite in the middle of a storm. Have you ever done this? I assume so; please provide a description of the catamaran and equipment you used and how it was set up. In a practical sense, having kite boarded and understanding the web of control lines required, how do you manage this amongst the crowded rigging of a catamaran, particularly with 50+ knots blowing across the deck?

Other than the kite, what are you saying is different from the following article?

https://www.sailmagazine.com/multihu...ng-a-catamaran

[Sail Houston]

I understand that setting a drogue to proper length is based on ensuring it stays in the same relative part of the wave as your boat - further back in long period waves and closer in short period waves. This is less important with a series drogue as long as it is at least as long as one wave period.

Regarding yawing from lack of steerage, that’s avoided by not slowing too much and helped by setting a drogue with a bridle to either stern. That’s standard practice.

But what are you referring to when you write “prevent sinking in the trough altogether”? Do you mean travel at the same speed as the waves to avoid falling into the troughs? Doesn’t that mean travelling at very high speeds to stay on the top of a single wave? If that’s the plan, then why use a drogue? I’m obviously missing something here.

I personally disagree entirely with what you are considering standard practice. You are describing again the context of how you know how to use a drogue to slow a boat down. You are just creating drag with the drogue.

I do not use a drogue in that fashion at all. I use a drogue to steer as mentioned previously and to increase my speed without surfing. Hull speed is a without getting super complicated is the square of the waterline x 1.34. You calculate the speed of the waves you are in then set the length of the leeward drogue to the calculated speed. adjust the windward drogue to length based on rudder angle until it goes completely neutral. When taking waves closer to a beam it may be necessary to set up planes (towed fish) to ensure proper roll stability.


Intriguing, it sounds like you are suggesting to fly a kite in the middle of a storm. Have you ever done this? I assume so; please provide a description of the catamaran and equipment you used and how it was set up. In a practical sense, having kite boarded and understanding the web of control lines required, how do you manage this amongst the crowded rigging of a catamaran, particularly with 50+ knots blowing across the deck?

Other than the kite, what are you saying is different from the following article?

https://www.sailmagazine.com/multihu...ng-a-catamaran[/QUOTE]

After you have the drogue setup you launch the kite. The kite requires only two lines not a web of lines. You need an attachment line and a trip line to take it down that's it. You run an adjustable pennant from the bowsprit where you would launch your code zero from and attach your code zero halyard to it. your attachment point for the kite goes at the intersection of the pennant and the halyard. This allows you to adjust the height of the center of effort upon which the sail is pulling. The kite flies way in front of the boat, self-trims and allows apparent wind angles up to about 100 degrees on either side. I also rig separate running backs or run a Dyneema bridle from the topping lift back to the code zero winches to create the same. With the kite, there is no trimming, no sail adjustment, no gybing, and no luffing ever. You are only ever changing the center of effort based on your conditions and sea state.

All of the mentioned techniques can be implemented on any cat, however, I have mostly used it on 40-52 foot charter cats being delivered for use as such to their destinations. Obtaining 20+ knots in this configuration is pretty normal. Sailing like this would not be possible typically because of the amount of turbulent water passing the rudders making the rudders virtually useless on this type of boat. Hence the need and my comment making it necessary to control lateral stability and steering by the use of the drogue setup you are using.

[fxykty]

Originally Posted by Sail Houston

I understand that setting a drogue to proper length is based on ensuring it stays in the same relative part of the wave as your boat - further back in long period waves and closer in short period waves. This is less important with a series drogue as long as it is at least as long as one wave period.



Regarding yawing from lack of steerage, that’s avoided by not slowing too much and helped by setting a drogue with a bridle to either stern. That’s standard practice.



But what are you referring to when you write “prevent sinking in the trough altogether”? Do you mean travel at the same speed as the waves to avoid falling into the troughs? Doesn’t that mean travelling at very high speeds to stay on the top of a single wave? If that’s the plan, then why use a drogue? I’m obviously missing something here.



I personally disagree entirely with what you are considering standard practice. You are describing again the context of how you know how to use a drogue to slow a boat down. You are just creating drag with the drogue.



I do not use a drogue in that fashion at all. I use a drogue to steer as mentioned previously and to increase my speed without surfing. Hull speed is a without getting super complicated is the square of the waterline x 1.34. You calculate the speed of the waves you are in then set the length of the leeward drogue to the calculated speed. adjust the windward drogue to length based on rudder angle until it goes completely neutral. When taking waves closer to a beam it may be necessary to set up planes (towed fish) to ensure proper roll stability.





Intriguing, it sounds like you are suggesting to fly a kite in the middle of a storm. Have you ever done this? I assume so; please provide a description of the catamaran and equipment you used and how it was set up. In a practical sense, having kite boarded and understanding the web of control lines required, how do you manage this amongst the crowded rigging of a catamaran, particularly with 50+ knots blowing across the deck?



Other than the kite, what are you saying is different from the following article?



https://www.sailmagazine.com/multihu...ng-a-catamaran

After you have the drogue setup you launch the kite. The kite requires only two lines not a web of lines. You need an attachment line and a trip line to take it down that's it. You run an adjustable pennant from the bowsprit where you would launch your code zero from and attach your code zero halyard to it. your attachment point for the kite goes at the intersection of the pennant and the halyard. This allows you to adjust the height of the center of effort upon which the sail is pulling. The kite flies way in front of the boat, self-trims and allows apparent wind angles up to about 100 degrees on either side. I also rig separate running backs or run a Dyneema bridle from the topping lift back to the code zero winches to create the same. With the kite, there is no trimming, no sail adjustment, no gybing, and no luffing ever. You are only ever changing the center of effort based on your conditions and sea state.



All of the mentioned techniques can be implemented on any cat, however, I have mostly used it on 40-52 foot charter cats being delivered for use as such to their destinations. Obtaining 20+ knots in this configuration is pretty normal. Sailing like this would not be possible typically because of the amount of turbulent water passing the rudders making the rudders virtually useless on this type of boat. Hence the need and my comment making it necessary to control lateral stability and steering by the use of the drogue setup you are using.[/QUOTE]


OK, more specific information is helping me understand your suggestions. Thanks.

What are you using as a drogue? You are using 2 right, one from each stern? What are the drogues exactly? Please provide details.

Regarding going faster by setting a drogue, I think I understand but your language is strange. Can’t you just write that you set a drogue’s drag (how exactly do you vary the drag?) such that it limits surfing but still allows the boat to travel the same speed as the waves?

What exactly is the kite that you use? Please provide specifications.

Your mention of hull speed and of turbulent water at the sterns making rudders useless and causing yawing is a definite characteristic of charter cats and doesn’t apply to more performance oriented cats. But still applicable I expect in extreme storm conditions.

Finally, ‘standard practice’ for heavy weather handling for both monos and cats does include using a speed limiting drogue to prevent surfing and steady the steering. Some prefer sea anchors instead or in addition, and lying hove-to or a-hull are also within standard practice.

What you are suggesting is different as you are using two drogues, not limiting speed, and using a kite rather than storm sails or bare poles. Unless you’re planning to sell your suggestions, please educate me. As the owner of a catamaran I’m very interested in learning a variety of methods of storm management.

[thinwater]

I'm struggling with what type of drogue is even remotely stable at 20 knots. Most surface and become unstable at 5-6 knots--this is well known and accounts for most single-drogue failures in storms. The Galerider goes faster, up to 10-12 knots, but at 20 knots practically anything is going to start skimming. At high speed, a weighted warp is probably as stable as it gets, but it is going to pull out of wave faces under load. I've watched it.

The wave length thing is also troubling. I've never been in conditions where the length was stable enough to keep the drogue in the same part consistently, certainly not for steady pull at that speed.

I also get the impression we are talking about stabilizing fast running, not storm management. While these definitions vary a lot with size of the boat, A drogue that will let you go 20 knots is not protecting you from surfing, it's allowing surfing.

[mikereed100]

Originally Posted by Sail Houston

I do not use a drogue in that fashion at all. I use a drogue to steer as mentioned previously and to increase my speed without surfing. Hull speed is a without getting super complicated is the square of the waterline x 1.34. You calculate the speed of the waves you are in then set the length of the leeward drogue to the calculated speed. adjust the windward drogue to length based on rudder angle until it goes completely neutral. When taking waves closer to a beam it may be necessary to set up planes (towed fish) to ensure proper roll stability.

Wait, what? You are flying a kite, trailing 2 drogues, one off of each hull, the length of the leeward set to match wave speed (how does speed relate to length?) and the windward set to achieve a neutral rudder angle? In addition to the drogues you are towing fish to control roll? In a cat?
You mention a hull speed calculation for displacement monohulls as a target speed then mention that you routinely achieve 20 knots without surfing using this setup?

[Pete7]

Originally Posted by mikereed100

Wait, what? You are flying a kite, trailing 2 drogues, one off of each hull, the length of the leeward set to match wave speed (how does speed relate to length?) and the windward set to achieve a neutral rudder angle? In addition to the drogues you are towing fish to control roll? In a cat?
You mention a hull speed calculation for displacement monohulls as a target speed then mention that you routinely achieve 20 knots without surfing using this setup?

I look forward to watching the YT video of this, from the safety of my arm chair, in front of the wood burner with a single malt.

Personally I can't imagine being in conditions that required the use of a drogue; that I would deploy 2, plus a fish and fly a kite. Yee gods what happened to keep it simple, KISS.

[thinwater]

Originally Posted by Pete7

I look forward to watching the YT video of this, from the safety of my arm chair, in front of the wood burner with a single malt.

Personally I can't imagine being in conditions that required the use of a drogue; that I would deploy 2, plus a fish and fly a kite. Yee gods what happened to keep it simple, KISS.

Yup, without pictures, this is a struggle. There are several places where the math is a problem. He has reinvented sailing.

[StuM]

Originally Posted by mikereed100

set to match wave speed (how does speed relate to length?)

That is about the only thing that is understandable with the described techniques

For deep ocean waves, wave propogation speed (celerity or c) in metres per second can be taken as c = sqrt(1.56 x Wavelength in metres).


That is derived from the more general wave formula:

c = sqrt( (g x l)/(2 x pi) x tanh( (2 x pi x d / l) )

where g = acceleration due to gravity, l = wavelength and d = depth of water.

[fxykty]

Originally Posted by StuM

That is about the only thing that is understandable with the described techniques

For deep ocean waves, wave propogation speed (celerity or c) in metres per second can be taken as c = sqrt(1.56 x Wavelength in metres).


That is derived from the more general wave formula:

c = sqrt( (g x l)/(2 x pi) x tanh( (2 x pi x d / l) )

where g = acceleration due to gravity, l = wavelength and d = depth of water.

Wow, phenomenally fast. I cross referenced this with https://manoa.hawaii.edu/exploringou...ves/sea-states and for fully developed waves (1,000 nm fetch and duration of 120 hrs). At 50 knots windspeed fully developed waves are 13m high and travel at 43 knots and have a wave length of 310m. For not fully developed waves half the wave length you still get a wave speed of 33 knots.

How the hell would a cruising boat come anywhere close to that speed on average to stay in the same position on a wave?

The OP needs to clarify how his system works.

[Barra]

i reckon you guys have been trolled...

[rabbi]

Originally Posted by Sail Houston

All of the mentioned techniques can be implemented on any cat, however, I have mostly used it on 40-52 foot charter cats being delivered for use as such to their destinations. Obtaining 20+ knots in this configuration is pretty normal.

I have never seen kites used as a sail on any cat at all, and somehow can't understand how it could be self-adjusting / controlling. I don't kitesurf, but from my memories as a kid all kites with steering lines required constant attention or they would fall out of the sky in an instant.

You mention an attachment line and a trip line. That to me sounds not like a kite used in kitesurfing but more like a parachute sail.

Adjusting the height of the attachment point sounds scary to me. Who would want to bring the center of effort higher than required, maybe to the top of the mast?
The forces required to drive a boat 20kn would be enormous and most likely damage the rig if the attachment point was too high.


But since you have done this multiple times on large cats I would love to see a pic or better yet a vid of a kite flying from a cat in winds of 40+ kn.
Please!!

[mikereed100]

Originally Posted by Barra

i reckon you guys have been trolled...

I reckon so, but it was fun while it lasted. Looking forward to future posts by Mr Houston.

[rabbi]

Originally Posted by mikereed100

I reckon so, but it was fun while it lasted. Looking forward to future posts by Mr Houston.

if we are lucky he is busy looking photos / videos or busy faking one.