Heavy vs Light Displacement

THERE HAS NEVER BEEN any general agreement on whether heavy-displacement sailboats are more seaworthy than light-displacement boats. It’s a subject that occupies many hours of beer-drinking time in yacht-club pubs and all too often results in harsh words and broken friendships.

Perhaps the views of K. Adlard Coles will be helpful in this respect. Coles was one of the world’s best-known long-distance racers and cruisers. He was a British publisher and one of a small band of fearless ocean racers who roamed the high seas in tiny boats just after World War II. He was unique in that he kept details of all the storms he nursed his little vessels through.

In his magnum opus, Heavy Weather Sailing, Coles agrees that the extreme shape of the modern ocean racer’s hull, which is designed to reduce drag from the underwater surface with its cut-away fin keel and spade rudder, makes a boat fast and efficient.

But, he points out, the sail area for such boats is critical and must be “exactly right” in relation to the strength of the wind, both to preserve balance and to avoid the rudder’s stalling in the event of excessive heeling or a knock-down in a squall.

 Coles feels that the motion in fin-keelers is much livelier than it is in older-style boats (no arguments from anyone about that) and thus steering a fin-keeler requires greater concentration, so even when you’re cruising, you can’t leave the helm alone for a moment.

He says steering is at its worse when the boat is running in strong winds, particularly with the wind on the quarter. Such a boat needs a constant supply of well-rested crew at the helm. But its livelier motion will put the crew under greater strain than a “conventional” boat would, and it would likely provoke more seasickness among the crew.

In exceptionally rough going, another disadvantage shows its face. The spade rudder is much more vulnerable to being damaged, whether it is attached to a skeg or not.

It’s interesting to note how enthusiastic a fan of light-displacement boats Cole used to be, and how successful he was in campaigning with them.  But, significantly, he was later converted to heavier-displacement ocean racing boats of the same length. He found these to be better sea boats with “immeasurably improved windward performance in really heavy weather” because of their ability to carry more sail and provide more drive.

Today’s Thought

He who will not be ruled by the rudder, must be ruled by the rock.

— Isaac D’Israeli, Curiosities of Literature

Tailpiece

“Frank, please lend me $50.”
“No can do, Charlie. Here’s $25.”
“But I asked for $50.”
“Yeah, I know, Charlie. But this way you lose $25 and I lose $25.”

(Drop by every Monday, Wednesday, Friday for a new Mainly about Boats column.)

The right size boat for you

HOW BIG A BOAT do you need for long-distance cruising in reasonable comfort? I say reasonable comfort because there are those among us, usually the young and adventurous, who will go to sea in almost anything that floats, no matter how small and rudimentary. And good luck to them. I salute them. But them are not me. And I are not they. Not any longer.

To answer the question, though: it depends on three factors: the number of crew, the weight of the stores they need, and the number of days between provisioning stops.

So, to find the minimum required displacement of a cruising sailboat (within 10 percent) start by multiplying the combined weight of crew and stores (including water) by 7.

For planning purposes, use these guidelines:

Crew: Multiply number of crew by 160 pounds.

Stores: Allow 6 pounds per person per day.

Water: Allow 8.5 pounds per person per day.

Safety reserve: Multiply the total of stores and water by 1.5.

Personal gear: Allow 5 pounds per days or a maximum of 120 pounds per person. (For permanent liveaboards, a maximum of 500 to 1,000 pounds is more appropriate.)

Here’s an example:

1. Find the minimum boat displacement for two people with water and provisions for 42 days.

2. Displacement (within 10 percent) = (weight of crew and stores) times 7.

3. Longest time between provisionings = 42 days.

4. Number of crew = 2. Crew weight = 2 times 160 = 320 pounds.

5. Daily stores = 6 pounds times 2 crew times 42 days = 504 pounds.

6. Water = 8.5 pounds times 2 crew times 42 days = 714 pounds.

7. Safety reserve = 504 (stores) + 714 (water) = 1,218; times 1.5 = 1,827.

8. Personal gear = 120 pounds times 2 = 240 pounds.

9. Total weight of stores, water, safety reserve and personal gear = 1,827 + 240 = 2,067 pounds.

10. Displacement = 2,067 times 7 = 14,469 pounds or 6.5 tons.

11. Displacement within 10 percent = 13,000 pounds to 16,000 pounds (5.8 tons to 7 tons.)

A heavy displacement 30-footer, such as circumnavigators Eric and Susan Hiscock’s Wanderer III weighs in at 16,000 pounds but more modern designs could get that displacement down to 12,500 to 13,000 pounds and produce a faster hull with more room down below. And in each case, the boat could easily be handled by a crew of two.

Today’s Thought
It is a pleasure for to sit at ease
Upon the land, and safely for to see
How other folks are tossèd on the seas
That with the blustering winds turmoilèd be.
— Lucretius.

Boaters’ Rules of Thumb, #176
To estimate the sail area a boat needs, take three quarters of the square of the waterline length in feet — that is, multiply the waterline length by itself and take 75 percent of the result. The answer is in square feet. Some boats will vary considerably, of course, but this will give you a general idea.

Tailpiece
“Sorry to hear about your husband. What happened?”
“Well, I asked him to pick a cabbage for supper and he went into the garden and keeled over suddenly and that was that.”
“Wow. What did you do then?”
“Oh, I opened a can of peas instead.”

(Drop by every Monday, Wednesday, Friday, for a new Mainly about Boats column.)

Weight on my mind

I NOTE WITH INTEREST that my boat seems to have sunk deeper in the water every time I happen to look at the boot-top. This has been going on for the seven years I’ve owned my 27-foot sloop, but I’d never stopped to give it serious thought until last weekend when I discovered two dozen cans of Heineken stuffed into a little-used locker, and wondered what they weighed.

My mind drifted back two-and-a-half years to an annual haul-out, when the crane driver leaned out of his cab and yelled over the noise of the diesel engine: “Nine thousand pounds.”

“Nah,” I thought, “can’t be. Her displacement is 7,500 like Mr. Alberg said. As designers go, he was no fool.” I dismissed it as inaccurate instrumentation on the crane, a built-in safety factor to prevent overloading.

But the same thing happened last May when I hauled out. “Exactly 9,000 again,” said the crane driver. I laughed it off. “Sure,” I said. How could she be 1,500 pounds heavier than her design displacement?

Well, I had a good look around last weekend and I must admit to being surprised by the amount of “stuff” on board, stuff that must have crept aboard at nighttime over a period of years, because I sure don’t remember carrying it on.

Take galley equipment, for example. We have mugs for six, about 50 pounds of assorted stainless-steel knives, forks, and spoons from the thrift store, a whistling kettle, heavy skillets that we hardly ever use, saucepans, and a host of gadgets for doing things to food and cans that I suspect were smuggled aboard by the First Mate when I wasn’t looking.

Water is darn heavy, of course. We always have full tanks, plus lord knows how many two-liter bottles of fresh water tucked away up forward, just in case there’s an earthquake and the house falls down and we have to go and live on the boat.

For the same reason, there’s a bunch of food, good heavy long-lasting food, sorted out in plastic bags by meals, all of it left over from a six-week summer cruise. It’s surprising how much it weighs. You wouldn’t suspect it, just to look at it.

Then there are the charts, about 100 of them, that I needed for that cruise. They never got taken home again because, heck, you never know when you might have to flee from an earthquake and head for the Alaskan wilderness. And I swear they absorb water because they seem much heavier now than when I first brought them aboard.

The self-inflating life jackets, combined with safety harnesses and tethers, are quite heavy. They are an example of why small boats suffer more from extra weight than big boats. No matter how big your boat, you only need one life jacket for each person, and a life jacket is a much larger part of a small boat’s displacement than a large boat’s, if you see what I mean. There are many other things like that, including an inflatable dinghy, whose weight would scarcely be noticed on a large yacht.

Did I mention the beer? Okay, but there’s also port. Bottles of port mature particularly well on a small boat. I’m told that the Portuguese used to ballast the Grand Banks fishing fleet with bottles of port. So we carry port also. Nice with cheese and crackers at sunset or after the evening meal. I discovered that we are down to one bottle, though, and now I don’t know whether to get another or not.

Perhaps if I get rid of some of the extra fuel it will balance out. There’s never enough fuel tankage on a small boat, so we always carry another five gallons in plastic jerry cans. I’m not saying it doesn’t weigh anything, but I still think 9,000 pounds is a lot of hogwash. Or maybe I’ll throw out some of the six extra containers of engine oil.

Okay, okay, I’ll grant you that the toolbox has expanded almost exactly as my store of tools in the garage has diminished. I don’t know how that came about, but it sure is nice to have five different-sized screwdrivers and three Vise-Grips, because they fall overboard so easily, you know.

I suppose the boots for hiking ashore weigh something but not as much as the first-aid kit the First Mate keeps adding to every time I turn my back. I swear we could remove an appendix or even carry out a colonoscopy if we had to.

Then there’s the spare sails, the anchor lines, the dedicated tow line, and hundreds of feet of
odd bits and pieces of line no longer than 9 inches long. I can’t bring myself to get rid of them because you just never know when you’ll need an 8-inch line.

I haven’t checked on the engine spare parts yet. The locker is so chock-full that I haven’t had the heart to explore in there. I’m afraid it will probably weigh just as much as the bosun’s spares stuffed into the locker opposite, many of which, I hasten to explain (especially the heavy galvanized shackles and things) were inherited with the boat.

I’ll admit that I was the one who added a self-steering wind vane on the stern that had to be balanced by two large lead bars in the bow anchor locker, but that doesn’t explain everything.
In fact, I can’t find any reasonable explanation for a 1,500-pound increase in displacement. She certainly doesn’t look any fatter from the outside, which I’m sure she would if that crane driver was correct.

Today’s Thought
What difference does it make how much you have? What you do not have amounts to more.
— Seneca

Tailpiece
A sailor with laryngitis knocked on the clinic door. A pretty nurse answered.
“Is the doctor here?” he whispered.
“No,” she whispered back, “come on in.”