Setting the Anchor and Wind Speed

[Sid at SailAway]

Here's a question and some food for thought. We pulled into Tarpon Basin, that would be in Key Largo, Florida Keys and dropped the hook. Tarpon offers pretty good protection from the wind depending on where you drop. That's why we stopped, to duck out from the front that is coming through and the associated 25-30 knot winds. While sitting here I got to thinking about setting the hook. We always use both engines to set the hook. We start out in slow reverse until the hook grabs, then almost full reverse to set.

Here's the question I pondered. At almost full reverse, what wind speed would equal the same amount of force on the anchor? Could something like this be calculated or just guestimated? Any thoughts on this? I imagine there are many variables involved, so for the sake of simplicity, let's say the boat is like mine, a forty foot catamaran with a new gen anchor and 30hp engines.

[Panope]

Sid, you can test this yourself by motoring in reverse into strong wind. In flat water, your boat will have similar windage from astern as forward.

With my 34 foot monohull, 40 horse engine, and fixed three blade prop, reverse engine trust equals about 30 to 35 knots. I have also measured my reverse thrust at 300+ Pounds. A feathering propeller like a Maxprop would double this value.

Difficult to test or predict are the jerks, and surges that come from waves and the boat sailing at anchor.

Steve

[CSY Man]

I am guessing my Twin Yamaha 150s at full reverse would equal 110-120 knot wind.

Tried it once as the windlass had jammed the nylon anchor rode and I attempted to un-jam it in reverse.
The anchor held in the bottom, (60' chain, 30' nylon, 15' depth, 30# Rocna)
Lots of strain on the gear, like at CAT 2 hurricane.
Again, it is a guess.
A good engineer may be able to calculate it...?

[MarkJ]

If it's 25 knots or more I don't use the engine to dig the anchor in as I feel the wind on the boat will do it fine.

Then I keep a careful watch for an hour. And am unlikely to go ashore on a first night over 25 knots.

But I am on a mono. A cat must have more windage.