Hull designs range the gamut, from absolutely flat to those with 24.5 degree transom deadrise V-hulls. So, how are you supposed to know just how much V is right, when you’re choosing a boat?
There are a lot of variables to consider, so let’s look at them one by one. For starters, think about the seakeeping vs. stability trade-off. All other things being equal, more V in the hull gives you the ability to chop through big seas with less impact, making for a more comfortable rough-water ride. But that V also reduces stability, so you can expect more rocking and rolling when those same waves hit you on the beam. It’s a pretty straightforward give and take. Now, put chines, weight distribution, and beam into the mix; all will affect just how well a hull runs, as well as how stable it is.
Next, you’ll need to consider draft. Generally speaking a flatter hull will require less water to float in, while a deeper V needs deeper water under the keel. Again, this is if all other things remain equal. Also note that weight loads have a less dramatic effect on flat bottom boats, since their footprint has more buoyant area contacting the water.
Now handling also needs to be brought into the picture. A deep-V tends to bank into turns, while a flatter hull slides through them. Some hull designs also seem to encourage props to blow-out in turns, while others maintain a tight grip on the water no matter how hard you spin the wheel. And remember that flatter hulls often get “squirrely” and difficult to handle, at high rates of speed.
Efficiency is yet another aspect of this argument which deserves examination. Boats with flatter hulls often require less horsepower to attain the same speed, since they plane easier. That also means they go faster, but only up to a point; deep-V’s can often reach higher top-end speeds (though they require more horses to do so) because of those handling traits mentioned above.
So, back to the question at hand: just how much V do you need? Here it in, in a nut-shell: People most concerned with maximum efficiency and stability, minimum draft, and maximum load-bearing capability should opt for a flat bottom. Those more likely to need rough-water ability, tight handling, and fast speeds, will be better served with more V under their feet. And anyone who cares about all of these factors will probably want a hull that lies somewhere in-between flat-bottom and deep-V, hence the popularity of versitile craft like bay boats, with 12 to 18 degree deadrise bottoms, which make a nice compromise on all of the above factors. Of course, there’s only one way to judge a particular hull, and find out if it delivers what you want: take it for a sea trial. Awww, shucks – there’s another reason you need to go for a boat ride!