New boats are wider...

lustyd

lustyd

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Following the recent thread on new vs old, I have a question on design. I was under the impression that new designs are wider at the stern due to enhancements in boat design and following race boat design to make them more stable etc. This then leads to the interior being wider and more roomy.

From the other thread, it seems popular opinion is that boats are wider to make them more comfortable and therefore less good at actual sailing.

Anyone know which is correct? I'd assumed the first would be right because race boats which go "to sea" are very wide indeed at the stern but I may be wrong of course :)
Cheers
Dave
 
I would imagine it's got a lot to do with surfing downwind - those puppies can shift, after all. Canting keels and pumping water between ballast tanks do the job of a crew on the side to keep it under control upwind, so I'd imagine with that level of technology you could sacrifice some of the traditional narrowness for outright speed on the reach or further off the wind.

However, design is an evolutionary thing, so it must work pretty well. I'm sure that one can look at a pattern and see how these innovations have been made to "improve the breed".

Hang about, don't these new ones look a bit like Lasers? Errr...
 
Wide doesn't necessarily mean slower, you just have to avoid sailing them on their ear. The Open 60s have hugely wide flat transoms that allow them to plane which is how you can get 25 knots out of a 60 foot boat.

The down side of broad beam is in ultimate stability, they tend to have a wide range of angles where they are stable inverted.

What really affects performance is when the wide beam is accompanied by high topsides to give lots of internal volume. The consequence is lots of external windage.
 
I might be talking complete rollocks, so bear with me. As I understand it, a wide stern gives you form stability (keeping the CoG 'inside' the boat) meaning you can push a bit harder, but the increased surface area causes drag... the biggest issue with a wide stern is if you go over they are more likely to be stable in the inverted position.

Edit: must type faster... like what SL said ^^^^^^
 
Cruising boats you see around have wide sterns to accommodate generous cabins below. A wide stern is more likely to round up when healed, because the shape of the boat tends to lift the rudder which in turn looses grip and so the boat rounds up (weather helm). A boat with more balance proportions, a narrow stern (like my Etap 35i) tends to sail better to windward, because it is less likely to round up.

I cannot answer as to how the ocean 60's with their big fat, flat rear sections cope, it may be the canting keels keep them more upright, together with the form stability, plus of course they tend to have two rudders, so one will always be deep in the water.
 
Could it be something to do with people getting bigger?
There is probably a correlation between the width of the boat and the square of the average person’s waistline. Hence we get bigger flatter bottoms and instability at various angles.
 
RTW race boats such as the open 60s and the Volvo 70s are wide and shallow. Trading upwind "bite" for off the wind power - especially reaching. However this added wetted surface area is a pain in light winds. I have rolled right over the top of a class 40 in a production 37 footer in 6 knots of breeze. I've also seen a 40.7 do the same to a volvo 70 in the light. Very different story in 20....

Inshore race boats tend to be much narrower on the waterline, and slightly deeper. With more emphasis on upwind performance - especially in smaller sizes. This also helps offer a more rounded performance - less pain in light winds.

Cruising boats are much more like the second, they're narrow and very heavy in comparison to open 60s etc, so don't benefit from being able to plane. Their "fat" is basically just drag. Better off the wind than their 70s and 80s counterparts, as the fat backside does help a bit, but there's a reason why the first 40 is lot narrower and sleaker than the Oceanis of the same size.
 
Many boat designs in the 70's and 80's evolved around the IOR rule which tended to give narrow sterns and bumps in the hulls, great for upwind sailing but poor downward (when pushed they could easily get out of control). Wider sterns started in racer/cruisers and then cruising boats in the late 80's and 90's without the constraints of the IOR rule (that rule died away!) giving hulls cleaner runs aft.

The cost of marina berths (they charged for length and not width - unless a multihull) and growth in chartering have pushed the designs even further whereby they sterns can be almost the widest point on a cruising boat which as stated about requires twin rudders to allow grip.

Modern ocean going racers are like modern dinghies (with about as much protection) - designed to plane fast and straight, and the reason the weather routers are probably the most important people on board to put the boat in the correct place to get the max speed. They will try not to sail to windward if at all possible!
 
lustyd said:
Following the recent thread on new vs old, I have a question on design. I was under the impression that new designs are wider at the stern due to enhancements in boat design and following race boat design to make them more stable etc. This then leads to the interior being wider and more roomy.

From the other thread, it seems popular opinion is that boats are wider to make them more comfortable and therefore less good at actual sailing.

Anyone know which is correct? I'd assumed the first would be right because race boats which go "to sea" are very wide indeed at the stern but I may be wrong of course :)
Cheers
Dave
Click to expand...

Most production cruiser designs seem to start with putting a two metre square double berth into a computer then fitting a boat onto the front of it. Nothing wrong with that - I own one. But the broad stern does compromise heavy weather handling, unless you also spend lots off money on very deep, preferably canting, keels, and twin rudders, in which case you have a win-win in that the boat can also plane. But the cost of this is huge, so most modern cruisers sail well in light to moderate winds, and are abolute pigs in heavy weather, when if you give them enough sail to drive them, the broad stern lifts the rudder out of the water and the boat rounds up out of control.

Like most modern production boat owners, I try to avoid heavy weather, though when I had to the boat came back west with F7 on the nose. was not pleasant sailing though - crash, bang,slam etc. In an old design (eg Contessa 32/Rival 34) it would have still been wet, but much more comfortable at sea. 99% of the time modern boats are better.
 
Although cruiser design has tended to follow racing lines, it is my guess that we have about as far as practicable in widening cruiser sterns, for the kinds of reasons given. Another factor giving better performance is a fine entry, with a narrow waterline beam. Many cruising boats are tending to do this, but with a very shallow forefoot which can make life uncomfortable going to windward.

I have found it interesting to note the difference between my 20 yr old design and its current replacement. The new boat has more freeboard (presumably giving better complance with the RCD but a nuisance in marinas), slightly wider stern, and a bigger sail area. The new boat is reportedly not so steady on the helm and although definitely faster downwind, appears to be slower and less comfortable to windward in a blow
 
We sailed many different types of Beneteaus (wide stern) and Jeanneaus (less wide) when we were chartering and they were noticeably different in performance.

Beneteaus were good offwind and easy to surf but not good upwind. Jenneaus were the opposite.

As I said in the other thread big aft cabins sold many more boats (women). Wide stern racing designs are designed for passages which are over 50% offwind, which is the fastest point of sail. Obviously they lose out a bit upwind particuarly heading back up the Atlantic, albeit they are still going quickly.
 
When I first saw my Fulmar on the had I thought I'd made a mistake in buying her.I'd come from an IOR racy design that had pinched ends that went to windward like a wich.The Fulmar has a much fuller profile which made me think she wouldn't sail as well.I was wrong.The hull is indeed fuller and the stern wider but not to the same extent as the new designs.It never lifts the rudder out of the water and given the right conditions, surfs nicely.I wouldn't go as far as as saying that she planes.And a heavy weather beat is no problem.I avoid it because I'm a gentleman not because the boat can't handle it.
To me the Fulmar shape is a very good compromise between a wide hull and good performance.There's enough room for an aft cabin as well. The modern designs notabley the french ones have been taken over the top in search of living space.
There are some moderate, good modern designs though.The Dufour 34 and 40 and the First 40.7 spring to mind.
 
lustyd said:
Following the recent thread on new vs old, I have a question on design. I was under the impression that new designs are wider at the stern due to enhancements in boat design and following race boat design to make them more stable etc. This then leads to the interior being wider and more roomy.

From the other thread, it seems popular opinion is that boats are wider to make them more comfortable and therefore less good at actual sailing.

Anyone know which is correct? I'd assumed the first would be right because race boats which go "to sea" are very wide indeed at the stern but I may be wrong of course :)
Cheers
Dave
Click to expand...

I'm sure that race boat builders try to build what will win. Bendytoy will build an Oceanis to sell which generally means interior accommodation to please SWMBO.
 
trapezeartist said:
Interesting, but I fail to see the practical significance of inversion testing a sailing boat without the rig.
Click to expand...

Especially given weight aloft (even a little) can make a significant difference to the angle of vanishing stability - normally reducing it so if they're raising the boat by pumping water into a tank on one side, they'll need to pump in more if the rig attached - i.e. create more of a perturbation.

Unless I'm missing something...
 
KellysEye said:
We sailed many different types of Beneteaus (wide stern) and Jeanneaus (less wide) when we were chartering and they were noticeably different in performance.

Beneteaus were good offwind and easy to surf but not good upwind. Jenneaus were the opposite.
Click to expand...

Agreed. I notice that my 1998 Jeanneau 45.2 is narrower at the stern than the current 45, and it is very good upwind despite being a beamy boat with 4.53m maximum beam on a 14.15m LOA. It does struggle downwind in light winds, mainly I think due to having the shorter rig, with a mast about the same height as a lot of 40 footers, and being fitted with a slightly smaller than standard genoa.
 
Another consideration in heavy weather and particulaly waves that are 'overtaking' the boat, a broad stern is more likely to be lifted as the wave passes, potentially resulting in broaching (and coming beam-on to waves) or even pitch-poling (sp?). Pinched sterns or even better canoe sterns will tend to part the waves.
 
trapezeartist said:
Interesting, but I fail to see the practical significance of inversion testing a sailing boat without the rig.
Click to expand...

How many places do you think there are with crane access and 20+ metres depth to do that test with the rig in place?

I agree it's not the full picture, but it's a test that the boat has to pass that is actually possible to perform!
 
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