LONG_KEELER
Well-known member
and excluding going on the plane , what defines an easily driven hull ?
and excluding going on the plane , what defines an easily driven hull ?
Low wetted area reduces resistance. This is predominantly an issue at lower speeds where it makes up a significant portion of total resistance. The added resistance due to wetted area is easily overcome by a modest increase in sail area.
The short answer is accommodation.and excluding going on the plane , what defines an easily driven hull ?
Except the sail area needs more ballast, so you need more buoyancy to support that, so you get more wave drag as well.Interesting stuff above - thanks!
Hang on a minute - so although you always hear 'all that wetted surface area' is a negative in relation to long-keelers, this makes virtually no difference given a little bit of a breeze and a decent amount of sail area?
The opposite situation is where you have limited power (sail area) and so want to minimise drag. In this case you build an easily driven hull which is very long and narrow, with hydrodynamically optical lines. The classic examples are the Scandinavian square meter classes.
Of course cruisers don't want to pay for a marina berth to hold all that length, nor do we want the cramped accommodation or wet ride, so tend to go for boats that fall somewhere in the middle.
I wouldn't want a very old-fashioned boat with over 50% ballast and limited sail area, but nor would I want a beamy racer with next to no forefoot that broached to every puff of wind. For cruising comfort and decent performance I look for a fine entry and moderation in other respects. My boat is twenty years old, and therefore a '90s design but it can still outperform many new boats in all winds, though its shorter waterline puts it at a disadvantage at higher speeds downwind. If I were starting again I might go for something more modern, but sparkling performance in light airs is not a cruising necessity.
Racers are certainly very weatherly, but reading reviews of AWBs suggests that early reefing and a tendency to broach are not uncommon in cruising designs. Size is a significant factor in stability, and today's 40-footers are inherently better able to stay upright than yesterday's more common 32s. As I understand it, wetted area accounts for a significant proportion of drag up to five knots or more, which I always find surprising.The stereotype of the broaching racer is not really accurate any more... The drive towards shorthanded sailing has resulted in a lot of designs that are designed to spend a lot of time under autopilot. A broach happy boat would be no good at all. Sailed even remotely sensibly the modern designs with a fair amount of beam forward, twin rudders and moderate fin keels from Sunfast, JPK, Pogo etc go upwind and downwind as if they are on rails.
It's the previous generation of skinny IRC designs with big bulbs on the bottom of skinny foils and deep skinny rudders, the Corby, Summit, King etc that are more broach happy.
We went from a pretty traditional C/R, an Elan, to a JPK. My stress levels (I'm the helm) have reduced dramatically. It's so, so much easier to drive in gusty conditions.
The point about wetted surface area is that it depends what it's doing. If it's principally in beam and providing righting moment and allowing you to either set more sail or specify a lighter keel, then overall you're increasing the performance potential of your boat in everything but very light winds. If it's just bulk in the water and your cross section is pretty rounded and not providing much form stability then it's just load carrying ability.
Just depends on what type of boat you want...
We've covered this subject frequently in many threads... There was one recently where the reviewers talked about a boat broaching, and described what they were doing sailing it. And I just thought, "well it will broach if you sail it like that." The techniques used to keep a more traditional boat on its feet, and those used to keep a more modern boat on its feet are a little different. So it's of no great surprise that testers who sail every boat as if it's a Contessa 32 find that more modern boats react differently. And that's more to do with rig than hull, principally that the jib is more important on a modern fractional rig to stopping the boat spinning out upwind than it was on older masthead rigs. But the reviewers in question hadn't touched the jib and were just dumping main in the gusts and complaining that the boat wasn't reacting as their older boats would.Racers are certainly very weatherly, but reading reviews of AWBs suggests that early reefing and a tendency to broach are not uncommon in cruising designs. Size is a significant factor in stability, and today's 40-footers are inherently better able to stay upright than yesterday's more common 32s. As I understand it, wetted area accounts for a significant proportion of drag up to five knots or more, which I always find surprising.