Updated:
Original:

# Ask Sail: The Relationship Between A Boat’s Windage and Anchor Load

In your October 2013 Ask SAIL section (“Bigger is Better”), Don Casey states that doubling a boat’s windage increases the load on an anchor approximately fourfold.
Author:

Robert Britson Panama City Beach, Florida

Q: In your October 2013 Ask SAIL section (“Bigger is Better”), Don Casey states that doubling a boat’s windage increases the load on an anchor approximately fourfold. As a professional engineer designing structures to resist wind loads, all building codes I work with indicate that wind pressure is directly proportional to surface area and is proportional to the square of the wind velocity. Applying the equations to a sailboat, doubling windage would double wind pressure, not increase it fourfold. Doubling wind speed is what would increase pressure fourfold. Am I missing something?

Don Casey Replies

A: You are correct. Wind load is more or less directly proportional to area, so doubling a boat’s wind profile essentially doubles the load on the anchor. However, the point I was trying to make is that when you have two boats of the same length, but one presents a much larger profile to the wind, the difference in the load on the anchor is going to increase exponentially as wind strength increases. When the wind goes from 15 knots to 30 knots, a boat with twice the windage will exert four times the pull on the anchor—a reality not accounted for in anchor charts based on boat length.

## Cruising: Miracle On Ice

I was preparing some tea just before heading topside for my watch. Even though it was summertime, the tea was not iced—it was hot. That’s because our boat was in the High Arctic. We were trying to complete a westbound transit of the treacherous Northwest Passage. If we ...read more

## New Monohulls: Hallberg-Rassy 400 & Hanse 460

For all the consolidation in the boatbuilding world in recent years, there remains plenty of variety out there, as can be seen in these two new monohulls. The products of two very different boatbuilders offer two very different takes on performance-cruising, even as they also ...read more

## The Power of Sails

I suppose it isn’t merely a coincidence that I’ve made significant changes to the sailplans of the last three cruising boats I’ve owned. The first project was the biggest. My old Golden Hind 31, Sophie, had lots of charm and character, but her sloop rig was laughably small. ...read more

## Charter the Sea of Cortez

Chartering and the notion of going “off the beaten path” may sound self-contradictory. Charter companies tend to put bases where demand is high and they can turn a profit, so if you’re lucky enough to find an outfit and a destination that gets away from the typical—say yes. To ...read more

## Cruising: Anchoring Skills

Watching charterers make a run for the last mooring in a cove is fun—and weird. I always wonder why so many would rather try to catch a mooring than drop the hook. Maybe charterers don’t trust their anchoring skills, but it’s harder to drive up and grab a buoy than most people ...read more

## 11th Hour Breakdown in the TJV

11th Hour Racing’s Mālama kicked off the second week of the Transat Jaques Vabre with keel problems, forcing co-skippers Charlie Enright and Pascal Bidégorry to adjust for a more conservative approach to the race’s remaining 2000 miles. “We’ve been dealing with a lot of ...read more

## Rolex Nominations Open

Award season is upon us, and US Sailing is looking for the next Yachtsman and Yachtswoman of the Year. Established in 1961 by US Sailing and sponsored by Rolex since 1980, the annual Rolex Yachtsman and Yachtswoman of the Year awards recognize individual male and female sailors ...read more

## Buying a New Main Sail

I’ve always known the importance of having good sails. As a low-budget boat punk, I prioritize making sure I can get where I’m going with the help of the wind, as opposed to under power. It isn’t necessarily my goal to be engineless, or basically engineless. It just happens that ...read more