Heavy vs Light Displacement

[Paul L]

Originally Posted by sneuman

There's much said about "speed = safety", but little evidence that anyone is able to put it into practice offshore. We had a thread a year or so ago to discuss those who had "outrun" a storm but there were virtually no real-life experiences to talk about, as I recall.
.....

I didn't see any one claiming in this thread that a lighter displacement boat was safer. If you look at the major storms that have occured with modern boats that can be compared, such as the Sydney-Hobart,the Queens Birthday and Fastnet, you wouldn't find evidence that heavy boats (or lighter boats) are safer. Probably the most consistent item that shows safer is longer waterlines.
One thing about heavy boats is that they typically end up motoring a lot. The biggest advantage of lighter boat is that they are just plain easier to sail.

Paul L

[Joli]

The reality is cruisers simply don't push boats. Having a light boat sounds great but is meaningless if you are unwilling to push the boat into a higher S/LR. I forget where it was written but most cruisers sail at about .85 S/LR of the theoretical hull speed (1.34 * the square root LWL).

[Paul L]

Originally Posted by Joli

The reality is cruisers simply don't push boats. Having a light boat sounds great but is meaningless if you are unwilling to push the boat into a higher S/LR. I forget where it was written but most cruisers sail at about .85 S/LR of the theoretical hull speed (1.34 * the square root LWL).

I agree. That is one reason you see so many engine hours ut on the cruisers. There is no need to push the boat. When I cruise my boat I do not push it. I could get a lot more speed if I wanted to. It is just an easy to sail boat that can be made to move with out a lot of work. Hence the ability to sail instead of motor.

Paul L

[barnakiel]

I think one should try not to mix things up.

When I say a light boat I do not mean a fragile boat, quite contrary - would you not accept that carbon is lighter and STRONGER than plain GRP? Of course, an extreme racing machine may be under-specified to make her not only lighter, but actually lighter than the competing boat and, in result, have a critical break-down. But the racing crowd have the money to do so and part of how you develop a boat design has always been from breaking the one you have and building the better one. This is how we got furlers onto our cruising boats, and nylon kites, dacron sails and so on - these things came from racing, from serching for the better material and today nobody says a dacron sail is worse, and unsafe, from a cotton sail, do we. Somehow, many people will say the lighter boat does not follow this general truth.

In normal design conditions (not for Vendee Globe, VOR nor Minitransat), a well designed carbo piece have every reason to be better lighter+stronger) than a GRP piece.

Now, do we stick to wooden masts or have we already agreed that alu is the better material? And so on and so forth, I am sure you can see my drift.

As far as safety from speed is concerned, I can only speak for the boats and oceans I have sailed plus a bit for first hand experiences of fellow cruisers. And my observation is that the lighter, faster boat gets extra safety points from the following:
- the fast boat can dodge the bad weather faster, if sailing within a safe harbour,
- the faster boat drives better running in bad wether,
- the lighter boat will be less prone to damage when a lot of kynetic energy is involved (e.g. hit a by a huge breaker).

For those who say one cannot dodge the weather I suggest having a quick look at a typical Atlantic hurricane size and its speed. Then imagine you are on its track. How much can you move away, in the same time, in a heavy, slow boat vs. a light and fast boat?

I am not talking about light boats build of paper mache, I am talking of things like say the Atlantic the Dashew or the Pogo. Light, strong, fast boats.

I love the heavier boats for their looks. And I say the can be great cruising boats. But the world has moved on and we do not have to go in an oxen pulled carriage if we can get somewhere in a jet plane.

I will probably stick to the classics myself because I love them but I will never say one cannot have a lighter, stronger, faster and safer boat.

And my last word is for those who believe heavy and slow is safe I can recommend the lecture of sailing accidents on the stretch between Tonga and NZ. Have a look at what type of boats got lost there and think of the possible 'why's.

b.

[rustypirate]

How about looking at it this way.

Rather than building a lighter version of a boat that is equally strong out of Kevlar or Carbon fiber, why not build one EXACTLY the same weight and thickness that is many times stronger.

As for dodging weather by trying to outrun it, good luck with that.
A faster boat beats itself to hell in rougher weather rather than riding with the swell.
A lighter boat is more prone to roll-over and demasting in extreme weather.

I knew several people who sailed in the '79 Fastnet race, and the lighter boats there were favored, but got smashed when the weather turned bad. The heaver boats were able to ride it out better. I also spent 22 days surfing a Vagabond42 down the face of waves over 50' tall crossing the Indian Ocean. for a hull with a rated top speed of 9.9 knots, we averaged 14.5. If it were not for the heavy displacement design, we woudl have easily been dismasted. When we arrived in Durban, we met with a lighter 60' twin masted schooner that got caught in the same storm and pitch-poled..... TWICE.

Take it for whatever you want, it sounds to me like your mind is made up.

buid your boat how it suits you, but I will stick to mine.

[Paul L]

Originally Posted by rustypirate

....
I knew several people who sailed in the '79 Fastnet race, and the lighter boats there were favored, but got smashed when the weather turned bad. The heaver boats were able to ride it out better. ....

Where do you find this conclusion from the Fastnet race? Here's is the actual inquiry report http://www.yachtingworld.com/fileBan...ce-inquiry.pdf
There is no evidence that heavier boats did better than lighter boats in the Fastnet disaster. There is some evidence that boats that maintained some speed did do better.

Paul L

[barnakiel]

Originally Posted by rustypirate

...

I also spent 22 days surfing a Vagabond42 down the face of waves over 50' tall crossing the Indian Ocean. for a hull with a rated top speed of 9.9 knots, we averaged 14.5. If it were not for the heavy displacement design, we woudl have easily been dismasted. When we arrived in Durban, we met with a lighter 60' twin masted schooner that got caught in the same storm and pitch-poled..... TWICE.

Vagabond 42 has only 34 of LWL, SQRT and times 1.4 would give 8.1 theo hull speed. Are you sure the 9.9 is the correct figure? Are you ceratain you averaged 14.5?

22 days 24 hours 14.5 knots equals 7656. When I sailed Darwin to Durban it was only 5500 miles. I know the continents drift apart but I was not aware of of how fast ;-)

Whatever. You might have had your 14.5 but one can't beat my max speed (see the speedo in the picture attached below - taken in the Indian Ocean, 2006). And going this fast in a 26 footer (25' LWL) we did not pitch-pole once, nor did we surf ...

;-)))
b

[MarkJ]

Originally Posted by barnakiel

picture attached below - taken in the Indian Ocean, 2006). b

Barney, I thought you'd be some ugly old coote! Better watch out for some of the single girls on this forum!



Mark

[bewitched]

Originally Posted by rustypirate

As for dodging weather by trying to outrun it, good luck with that.

We can!!

Light boats can sail away from weather quite easily and the ride is very comfortable. Typically the boat is moving quicker that the wave and when that gets too dangerous (broaching while surfing down a wave)downsize sails to stay on one wave.

The technology has not filtered down into cruising boats yet, but it's only a matter of time I think.

YouTube - Hong Kong to Vietnam Race 08

[sneuman]

Originally Posted by bewitched

We can!!

Light boats can sail away from weather quite easily and the ride is very comfortable. Typically the boat is moving quicker that the wave and when that gets too dangerous (broaching while surfing down a wave)downsize sails to stay on one wave.

The technology has not filtered down into cruising boats yet, but it's only a matter of time I think.

great video. brings back memories for me.

as has been pointed out though, a fully crewed TP52 is not the same as a mom and pop cruiser. No way a cruising couple is doing this no matter the displacement of the boat.

[andreavanduyn]

Originally Posted by barnakiel

I think one should try not to mix things up.

When I say a light boat I do not mean a fragile boat, quite contrary - would you not accept that carbon is lighter and STRONGER than plain GRP? Of course, an extreme racing machine may be under-specified to make her not only lighter, but actually lighter than the competing boat and, in result, have a critical break-down. But the racing crowd have the money to do so and part of how you develop a boat design has always been from breaking the one you have and building the better one. This is how we got furlers onto our cruising boats, and nylon kites, dacron sails and so on - these things came from racing, from serching for the better material and today nobody says a dacron sail is worse, and unsafe, from a cotton sail, do we. Somehow, many people will say the lighter boat does not follow this general truth.

In normal design conditions (not for Vendee Globe, VOR nor Minitransat), a well designed carbo piece have every reason to be better lighter+stronger) than a GRP piece.

Now, do we stick to wooden masts or have we already agreed that alu is the better material? And so on and so forth, I am sure you can see my drift.

As far as safety from speed is concerned, I can only speak for the boats and oceans I have sailed plus a bit for first hand experiences of fellow cruisers. And my observation is that the lighter, faster boat gets extra safety points from the following:
- the fast boat can dodge the bad weather faster, if sailing within a safe harbour,
- the faster boat drives better running in bad wether,
- the lighter boat will be less prone to damage when a lot of kynetic energy is involved (e.g. hit a by a huge breaker).

For those who say one cannot dodge the weather I suggest having a quick look at a typical Atlantic hurricane size and its speed. Then imagine you are on its track. How much can you move away, in the same time, in a heavy, slow boat vs. a light and fast boat?

I am not talking about light boats build of paper mache, I am talking of things like say the Atlantic the Dashew or the Pogo. Light, strong, fast boats.

I love the heavier boats for their looks. And I say the can be great cruising boats. But the world has moved on and we do not have to go in an oxen pulled carriage if we can get somewhere in a jet plane.

I will probably stick to the classics myself because I love them but I will never say one cannot have a lighter, stronger, faster and safer boat.

And my last word is for those who believe heavy and slow is safe I can recommend the lecture of sailing accidents on the stretch between Tonga and NZ. Have a look at what type of boats got lost there and think of the possible 'why's.

b.

100 AGREE ; answer to my original question; thank you.

[bobfnbw]

If I wanted to go fast, I would get a trimarian.
But I want a CRUISING BOAT, which means to me, a boat that can handle all the stores, spares, people, ground tackle, extra sails, water, fuel, and on and on that I feel I would need going out into the oceans of the world.
Maybe a lighter boat of 60 or 80 feet like Dashewes Beowulf, or a sundeer would be ok, but I don't have a couple of million in change lying around, So I guess I will stick with my Endeavour. Might not get much over 7 knots, but think of all the money I saved. Hell I could trash a bunch of them for the same amount of money a sundeer would cost me. Just leave a string of them on reefs around the world, and still be ahead... lol.

The thing is about going fast, is you have to concentrate on whats happening all the time. Go slow, not so much. One is exhilarating, one is relaxing. So again, If I want exhilarating, I will get a tri. But don't dare add any weight...

[bewitched]

Originally Posted by sneuman

great video. brings back memories for me.

as has been pointed out though, a fully crewed TP52 is not the same as a mom and pop cruiser. No way a cruising couple is doing this no matter the displacement of the boat.

I agree entirely - there is no comparison between a TP52 and cruising, But i do believe that design and technology, that is developed in the race end of sailing does have applications that can filter down into cruising. It is a whole different mindset to the build it strong, heavy, and slow approach.

Perhaps a Class 40 boat would have been a better example; designed for fast, short-handed off-shore sailing. These boats don't use 'exotic' materials - the class rules forbid it - but they are easily capable of maintaining 15kts + offwind and on autopilot.

It's another option - it won't suit everyone

[S&S]

Originally Posted by barnakiel

How much can you move away, in the same time, in a heavy, slow boat vs. a light and fast boat?

How about a heavy and fast boat? Not being facetious but, at least with non-planeing boats, we're generally talking single digit speeds- and that mostly based on waterline length.

[sneuman]

here's a nice video of a Tayana 37 running in 25 footers. Smooth sailing:

YouTube - Dead downwind in a gale 1