Physics of heaving to

[Delfin]

I have found that Delfin, with a 7.5' draft, heaves to perfectly in 20 knots of wind, moving sideways without forereaching, which creates the wave killing slick upwind. From the lines, this is probably because the center of balance of windage is amidships. My question for the experts with experience in heaving to in blue water is whether what works at 20 knots will work with 50 knots of wind. Seems logical that it would, but am I missing something?

[JPA Cate]

The forces are much higher, the force of wind strength goes up as the square of the speed. The waves get much bigger, as well. At some point, being hove to would expose you to beam on seas that could threaten your vessel. Prolonged 50 knot winds, plus higher gusts, can produce really THREATENING seas.

Ann

[Nicholson58]

The answer to the balance question is that the balance point should not change much. Ann’s point is correct as well. You might prefer fore reaching at som point. Read Storm Tactics by Lin and Larry Pardey. This is the best source I know for this and applications to different boat types is presented.

Nice boat! But a lot of windage.

https://www.amazon.com/Storm-Tactics.../dp/B00E1JR3P6

[Amnesia II]

My own experience in a Westsail 32 many yrs ago in the Atlantic, on passage from Gibraltar to Azores. Our course east to west, huge seas marching down from the north, we had only 35knts of wind but the storm was much further north producing these seas. We could sail during daylight, rounding up into breaking waves but at night it was prudent to hove to, not seeing the seas breaking. With full keel we sat reasonably comfortably 60 degrees to the waves and wind, infact in the morning a fix showed we gained ground to the north, incredibly, easing our fear of missing Santa Maria, the most southerly island in this northerly blow. It was great to finally get in.

[Delfin]

Originally Posted by Nicholson58

The answer to the balance question is that the balance point should not change much. Ann’s point is correct as well. You might prefer fore reaching at som point. Read Storm Tactics by Lin and Larry Pardey. This is the best source I know for this and applications to different boat types is presented.

Nice boat! But a lot of windage.

https://www.amazon.com/Storm-Tactics.../dp/B00E1JR3P6

I think that's correct regarding balance. The forces certainly increase, and exponentially, but uniformly on all areas of windage.

Regarding Pardey's advice, as I recall, his objective is to avoid any forereaching in order to generate the turbulent slick to windward that kills breaking waves. That is the point of his bridle arrangement on a para anchor. What I find interesting with this vessel is that she naturally moves slowly 90 degrees downwind in the winds I've experienced. I guess the concern would be that in stronger winds, as Ann suggests, the increased boisterous nature of the waves might push her off that alignment with the result that you did start getting hit by breaking waves. Wind doesn't scare me. Waves do.

[zstine]

The physics involved are not complicated... at least when rough seas are not involved. However, it is a dynamic balance between the sails, keel and rudder and what works at 20knts may not work at 60knts. For instance, at 20knts you can likely heave-to with full sail up, but not at 60knts. You have to reduce sail, but maintain the balance...

The basic physics... With some forward motion the rudder (lashed to turn to windward) turns the boat up into the wind. As forward motion dies, the backed head-sail overcomes the rudder force and turns the bow off (the center of lift also shifts turning the boat, not just rudder forces alone), which causes the main to catch more wind and drive the boat forward. Again as forward motion increases, the rudder turns the boat up into the wind and the boat slows... repeat. When balanced well the oscillation described is nearly imperceptible.

[Delfin]

Originally Posted by zstine

The physics involved are not complicated... at least when rough seas are not involved. However, it is a dynamic balance between the sails, keel and rudder and what works at 20knts may not work at 60knts. For instance, at 20knts you can likely heave-to with full sail up, but not at 60knts. You have to reduce sail, but maintain the balance...

The basic physics... With some forward motion the rudder (lashed to turn to windward) turns the boat up into the wind. As forward motion dies, the backed head-sail overcomes the rudder force and turns the bow off (the center of lift also shifts turning the boat, not just rudder forces alone), which causes the main to catch more wind and drive the boat forward. Again as forward motion increases, the rudder turns the boat up into the wind and the boat slows... repeat. When balanced well the oscillation described is nearly imperceptible.

I believe that what is happening with Delfin is that the North Sea bow acts like a backed headsail, and the pilot house like a reduced main. I hove to many times with my Cape George cutter, which is also a very full keel boat like this one, but could only do so successfully with appropriate sails up. Pardey's bridle on a para anchor is designed to stabilize the vessel with no sails up, which is why he reported it working so well in an Indian Ocean hurricane in Serafyn's Oriental Adventure.

My curiosity is whether the natural balance Delfin displays in modest winds without sails because of where the windage is located on her when canted into the wind will still hold in higher winds. One way to find out, I guess...

[zstine]

Is the OP asking about a motor yacht?? Then he is describing "lying a-hull". Boats not flying sail cannot heave-to by definition. A boat hove-to uses sail to dynamically change the center of lift/balance of the windage and doesn't drift downwind. If the OP is lying a-hull nicely at 20knots without sail, just windage on the boat, then no I would not necessarily expect it to maintain the same angle to the wind at 60knts. I don't think the force balance for topside and submerged appendages will increase proportionally to each other. There's flow induced lift, particularly with submerged foils, that will change the balance, different density and viscosity balancing wind and water, you will move more water so there's inertial effects, etc... I'm not a power boater, but I think a drogue or sea anchor would be a good piece of gear for storm tactics on a power yacht. This equipment would allow him to adjust the angle of the boat relative to the wind so he doesn't get broadsided.

[Cheechako]

Originally Posted by Delfin

I have found that Delfin, with a 7.5' draft, heaves to perfectly in 20 knots of wind, moving sideways without forereaching, which creates the wave killing slick upwind. From the lines, this is probably because the center of balance of windage is amidships. My question for the experts with experience in heaving to in blue water is whether what works at 20 knots will work with 50 knots of wind. Seems logical that it would, but am I missing something?

I have not found a boat that will heave to in rough water and strong winds. The reason is simple; Water has more force than wind.
Hove to, your bow is slightly up, when a large wave passes you, the boat ends up in the trough with little wind, the next thing that hits you is a big wave which shoves the bow of the boat down. Even Lin and Larry Pardey with a long keel boat tried to fix this issue with bridles and other attempts etc and wrote a book about it.
At 20 knots of wind my boats hove to fine. At 35-40 with seas, not so.

[MJH]

Originally Posted by Delfin

I have found that Delfin, with a 7.5' draft, heaves to perfectly in 20 knots of wind, moving sideways without forereaching, which creates the wave killing slick upwind. From the lines, this is probably because the center of balance of windage is amidships. My question for the experts with experience in heaving to in blue water is whether what works at 20 knots will work with 50 knots of wind. Seems logical that it would, but am I missing something?

We were returning from Hawaii to Keah Bay, WA and got into a Northerly 35K gale about 100NM off the Washington coast (Graveyard of the Pacific) with a wave coming over the stern breaking the wind vane. I called to hove-to after not being able to hold course but the staysail was on the wrong side for the maneuver. To get the staysail on the proper side we had to do a 360 and catch the staysail luffing midway as the boat would not tack over. It all worked out and we averaged about 2-3K toward the entrance of the Strait of Juan de Fuca on a comfortable ride with one man on duty to watch for traffic on the AIS while the rest of the crew slept. I'm not sure we could have done that maneuver successfully in 50K of wind.

~ ~ _/) ~ ~ MJH

[JPA Cate]

I'll confess, from the first picture, I thought we were dealing with a motor yacht, not a motor-sailer. She looks like she doesn't heel much. One of the deals about heaving to is that the boat will heel to the wind, and since the force goes up with the square of the velocity, even if she sits on an even keel when hove to at 20 knots, she is likely to heel at 50. If she is able to keep her head up to the weather, and you might need the storm jib to help with that-- the ride should be okay. But tiring, noisy (which adds to the fatigue). I wouldn't volunteer to go out and test it.

Ann

[Nicholson58]

When I spoke to Larry Pardey at the Chicago All Sail Boat show about 12 years ago. His book outlines different options depending on the conditions and the type and size of the boat. He was very specific about para-anchors and series drogues for large and heavy boats. He recommends against it.

1. There is not a place on your boat strong enough to secure it.
2. You will likely hurt yourself deploying it.
3. You will not get it back.
4. You will not want to sacrifice the storage space it needs.

Larry also said hove to was very hard on the rig and results in a bad chafe situation depending on your layout. He much prefers fore reaching especially for large boats and full keels.

[Cheechako]

Originally Posted by Nicholson58

When I spoke to Larry Pardey at the Chicago All Sail Boat show about 12 years ago. His book outlines different options depending on the conditions and the type and size of the boat. He was very specific about para-anchors and series drogues for large and heavy boats. He recommends against it.

1. There is not a place on your boat strong enough to secure it.
2. You will likely hurt yourself deploying it.
3. You will not get it back.
4. You will not want to sacrifice the storage space it needs.

Larry also said hove to was very hard on the rig and results in a bad chafe situation depending on your layout. He much prefers fore reaching especially for large boats and full keels.

Yeah, I have to say, I had a Parachute and finally decided I needed to try it in less than survival conditions. So out it went in about 15-20 knots of wind and moderate seas. UGH! Boy... talk about a workout for a couple of hours. It was near impossible to get in, the strain was huge, it was very unmanageable etc. I would hate to be left with that option in rough weather. I think you need to be prepared to just cut it loose when you need to.

[zstine]

It would be interesting to hear how people have actually handled 50knts-80knts sustained winds. Kinda like the "anchoring in 100knts" thread a few weeks ago where people who have actually done it chimed in.


I have sailed in 40kts sustained, 12ft-15ft seas. We sailed to weather under double reef main and stay sail and had no problem making over 5kts through the water. I don't carry a drogue or sea anchor. I believe I could sail in 50-60kts reaching off and with modern weather forecast, I shouldn't ever sail in more than that... I hope. I would not heave to unless there were extenuating circumstances. In fact, I believe keeping-on-going, as long as you can, is the best storm tactic. IMO, heaving to, lying a-hull, drifting with a sea anchor or drogue, etc. are 'Oh Sh!t' tactics used in emergencies... 50kt winds alone does not constitute an emergency.

If a sea anchor is deployed off the bow, why can't you use the main engine to lower tension to retrieve it? Also, Many drogue and parachute style systems can/should be rigged with a trip line on the back side so that they collapse for retrieval and are hauled in backward... though I have no personal experience...

[Delfin]

Originally Posted by Cheechako

I have not found a boat that will heave to in rough water and strong winds. The reason is simple; Water has more force than wind.
Hove to, your bow is slightly up, when a large wave passes you, the boat ends up in the trough with little wind, the next thing that hits you is a big wave which shoves the bow of the boat down. Even Lin and Larry Pardey with a long keel boat tried to fix this issue with bridles and other attempts etc and wrote a book about it.
At 20 knots of wind my boats hove to fine. At 35-40 with seas, not so.

That makes sense, Cheechako. Probably my best option in really nasty conditions is trailing a drogue. We experienced 50-60 knots from a thunderstorm in Alaska this year, but only in bursts. She did heel, but not much more than 15 degrees or so, since the majority of weight is very low. But on the open water the blanketing effect of the kind of waves that go along with 50+ knots of wind would really change the whole dynamic of heaving to, and not in a good way.

Much obliged to all.