Use of Sea Anchor

[Smourt]

Hi

I was wondering about using a sea anchor in a wind over tide situation.

In the Mozambique channel you can get up to 6 knots of current, if you were to deploy a sea anchor at say 30 knots of wind from the opposite direction I am assuming that there may be some sort of issue. I suppose the stronger the wind the more effective it will be.

Thoughts?

[GordMay]

A sea anchor is deployed off the bow, and is a (sort of) “brake”, used to keep a drifting (sails down) boat’s head to the wind and waves, so that it may ride rough seas more comfortably. The drag created by a sea anchor can keep a drifting boat in more or less one place, or at least prevent it from drifting too far too fast.

[sailormed]

Smourt if I understand it correctly you want to deploy your sea anchor in this situation so you are “drifting” your boat against the prevailing wind and get Speed over Ground against the wind by using the 6 knots current?
So your distination is upwind but down the current.

[Smourt]

Yes, that is correct.

I was wondering how a cat or mono would behave in these conditions.

[hpeer]

Originally Posted by sailormed

Smourt if I understand it correctly you want to deploy your sea anchor in this situation so you are “drifting” your boat against the prevailing wind and get Speed over Ground against the wind by using the 6 knots current?
So your distination is upwind but down the current.

Thanks for that clarification.

The other thing to clarify exactly what the OP means by “sea anchor” as he could mean one of 3 things:
1-a true sea anchor -being something like a parachute that is deployed off the bow and essential holds the boat still in the water column.
2- a high resistance drogue like a Jordan Series Drogue which is normal deployed off the stern and provides a LOT of resistance but won’t stop you in the water
3- a low resistance drogue like a Gale Rider or SeaBrake, normal deployed off the stern which is designed to slow you down in the water column to keep a safe speed.

I think the answer would be different for each of these devices.

1 would give you the most connection to the current, it’s a huge light weight thing, would likely be very difficult to retrieve.
2 ????
3 would give you less forward speed, you would get some traction if the current velocity but would be easier to retrieve.

I was in a strong wind against current situation once, 6knots against about 20 knots of headwind. Motoring right along. But the standing waves were awesome, i was more hanging on than steering as we pounded through. Bow up to the sky, now down in the trough, it’s a wonder I didn’t throw the stick out.

IMHO best to avoid that situation all together. I would only do this if I really screwed up.

[Monte Cresto]

Wrong application for tide but read the book by Capt John Voss
on the "Tlikum". He explains all uses for a sea anchor (A good read).

[EmeraldCoastSailor]

Interested in seeing responses to this one.

[roland stockham]

Interesting though, in theory you may get about 4kn up current and a corresponding 4kn increase in wind speed. May work better if you use a brace to to bare off some and effectively use the sea anchor as the 'motor' as in motor sailing. Never head of anyone doing this so may be a trial and effort job. Let us know what happens if you try it.

[Hardhead]

Strictly speaking, wouldn't it be that the sea anchor is pulled in the direction of the current at 6 knots, and the boat is downwind, the opposite direction, being blown downwind with 36 knots of force? In my experience though, a sea anchor often winds up holding the boat at an angle to both the wind, and the current, in a sort of cockeyed equilibrium that's not obvious to predict. Once you see how it develops, you can shift the sea anchor attachment point to effect how the boat is hitting the waves.

[Paul Howard]

When we sailed around South Africa, from Richard's Bay to Capetown, there was a 35ft monohull, headed south and around to Capetown, who told us he got caught in a southerly gale on the Indian Ocean side of S.A. and deployed a sea anchor from the bow.
He told us the sea anchor in the current towed him upwind at a rate of about three knots.
I don't know the rate of current at the time, but it does flow strong when offshore.
The general rule, though is to go inshore, on soundings (600ft or less) and heave-to on the offshore tack if you get caught by a southerly buster on the Indian Ocean side of South Africa. The waves are less steep and not as high in the shallower water where there is less current.

[Clivevon]

Interesting. I read somewhere that sea water is 700 times denser than air, meaning that tides & currents normally have more impact than drag from windage. Of course the sea only affects the underwater area, which will be much less usually than the total area of the hull, masts & rigging exposed to the wind, so the 700 factor is much reduced - but not eliminated.
Ignoring the sea anchor for a moment, & assuming no sails set, the boat will drift at 6 knots with the current, slowed down by the drag of the 30 knots of true wind. So it might drift at (say) 4 knots into the wind, with 34 knots of apparent wind over the deck. Sea state is going to be rough with 36 knots of apparent surface wind, so deploying a sea anchor from the bow should IN THEORY hold the bow up into the waves, & reduce the drag from the wind, while increasing the surface area exposed to the current, thus possibly increasing the drift rate INTO the wind - maybe to 5 knots...??

What does the tide do in that area?

[waterman46]

Wind against current can sometimes raise bigger seas than you would expect, depends on your relative windspeed vs true windspeed. But other than that you will only notice the current of 6 knots if you read your boatspeed with GPS. You could find yourself doing 2 knots to weather without using motor or sails!

[Mike Banks]

Sea anchors are too big for your purpose--what you need is an inexpensive drogue which will keep your vessel heading into the current, or if the wind is really it will lie at an angle to directly downwind but with less moving about.

[waterman46]

Originally Posted by Mike Banks

Sea anchors are too big for your purpose--what you need is an inexpensive drogue which will keep your vessel heading into the current, or if the wind is really it will lie at an angle to directly downwind but with less moving about.

Mike, I just misinterpreted the meaning of your first sentence. You have experience with this so my only point was that any drag device cannot orient the boat to the current, only to the wind direction.

[waterman46]

Boat and any drag device are in the same current, so it cannot align boat with current. Drag device only affects alignment of boat to forces of relative wind and seas. Any device steamed from bow will cause boat to try to head into wind and waces but boat will move backwards. So you want a device that will not allow much reverse speed to avoid stress on rudder. Sea anchor is better for this than a drogue.