And for the people that have semi-displacement hulls, do you ever really use the extra speed or do you run in the 8 knot range most of the time anyway?
Grand Banks are semi-planing hulls (the term semi-displacement, while commonly used, is actually inaccurate. It's sort of like saying semi-dead
A boat is either displacement or it's not, whereas there are varying degrees of being on a plane). If we had engines that could do it, we would cruise our boat at 9 or 10 knots, maybe more. But the engines in our boat can't do that so we cruise at about 8 knots and hate it despite the economy. Slow sucks, is our motto.
But we've met a number of boaters who rountinely cruise their higher-powered, semi-planing boats much faster than hull speed. In fact it is the large market of people like this that led Grand Banks and others to start putting larger and larger engines into their boats sarting in the later 80s. The buyers, many of whom have limited time for boating, want to get to their destinations as fast as possible, then cruise around at a slower pace, and then blast home again, thus maximizing their time in the waters they want to visit and minimizing the time it takes to get there and back.
A classic example in this area is Desolation Sound. People with high-power GBs can get there from the northern end of Puget Sound at 15-16 knots in a day and a half to two, where it takes us four days at 8 knots if the weather cooperates. This is running a reasonable amount of time each day, not running sunrise to sunset or all day and all night.
Everything is relative but fuel remains one of the smallest costs of boating. To people who can afford new or newish GBs, Flemings, etc, fuel is the next thing to being free. They believe their time is far more valuable than fuel, so they are willing to run for a few days at 23-30 gph to maximize their vacation time in the waters they want to be in, like Desolation Sound. Once there they're happy to plod around at 8 or 9 knots burning 7 or 8 gph. The semi-planing hull can provide the means to do both.
We would definitely use it that way if we had a boat that could take advantage of the hull design. Unfortunately, we have the hull but we don't have the power. If we end up reworking the boat we have now, we will install somewhat more powerful engines so we can climb out of the 8 knot primordial ooze and "zip" along at 10 or 12.
