.... The boat's weight is still largely
supported by displacement rather than dynamic lift, hence the hole in
the water which the wake is closing up.

Short Wave Sportfishing wrote:
Good point.

I think most people overlook the real meaning of "planing" and prefer to
think of it as much faster than when it really begins to happen. But it
also effects steering, so it's important to know about.



I commend you for taking the time & effort to put some observation on
the wake. Far too many people pretend it's not there.


This boat has always interested me in that, as I've mentioned about a
zillion times, it has no bow lift and it's theoretical top speed is
about fifteen mph above what it actually gets (40 vs 55). It doesn't
act like it's supposed to. :)

No bow lift is nice, I bet the steering is well balanced through the
transition as well. Hull design has come a long way in the past 20
years, but then engineering costs money and most boat companies know
they can sell the same old same-old.

I'm curious about the top speed issue- have you gone into the prop
question? Is your motor getting up to rated RPM? Is the boat over weight?




Somewhere floating around I have some pictures taken astern from the
Johnson 18 when it's planing, when close-hauled and under spinnaker.
When "fully planing" there's no wave train at all, just a flat swath of
white water. Of course the hull shape is much more efficient....


I'd like to see those.

I'll hunt around for them. The shots were taken with a throwaway camera
and I never scanned them. The only reason I took them at all is that we
were in a race with the boats too spread out to be much excitement, and
I was concentrating on getting some shots of wife with the spinnaker.
The wake shots were kind of an afterthought

... I'm not sure I could agree about efficiency -
the Ranger hull is pretty efficient if only because of it's odd
performance.

heh heh look at the difference in horsepower. The Johnson 18 carries
about 600# total at 25 knots on about 10 or 12 horsepower. I'm sure your
boat is much heavier but if you wanted to plot both boats on a
power/speed/per pound graph, I'd bet a *lot* that the Johnson 18 is far
more efficient.

For one thing, the hull of a saliboat is shaped for much less drag than
a planing motorboat... it has to be, sailboats spend too much of their
time not planing and with too little horsepower available, so to shape a
sailboat for planing only cripples it. To get it to plane at all
requires more lift from the little power available... actually there are
exceptions to this, such as the unlimited skiffs. Secondly, things like
spray strakes add drag (they also stiffen the hull) and cost a lot,
efficiency-wise. It's like the difference between a jet & a glider. The
glider is more efficient, but then the jet doesn't need to be
efficient... but it does have other critical performance parameters.

Fair Skies
Doug King