What is the definition of PLANING?
Charlie Fly,282-6812,Unisys
part or all of the weight of the boat. This is distinct from the hydrostatic pressure
due to depth that causes the bouyancy effect. Dynamic pressure results from the
relative motion between the boat and the water.
A hydrofoil driven hard enough to rise to the surface would plane on its bottom surface
for example.
One of the heavy gurus in this area is Peter R. Payne who has published a number of
articles and books on the subject. He came up with what he calls the supercritical
planing surface (SPC). The SPC can achieve lift to drag ratios on par with hydrofoils.
Look at his stuff if you want more info. But some reasonably hefty math is presented.
cfly
Pierre McAlpine
planing has come up quite alot. Yes, I would consider myself a "novice
sailer/racer" so no sarcasm please. What exactly does it mean? Does
it mean that you are surfing on a wave, going faster than the waves,
keeping up with the waves...or what?
Also what is meant by a planing hull? Or a "planing boat" i.e. a boat
that is prone to planing. What characteristic of the hull would make it
a planing one? Would it be a hull which is flat-like (ex: fireball,
y-flyer)?
Thanks for your help,
Pierre
Rod Mc Innis
Here is a rather simplified explanation, although it may not be entirely
correct.
As the boat moves forward at slow speed, the bow parts the water
in front of it. This water will then flow off to the sides in a
wave that is known as the wake.
As the boat speed increases, the water must be moved aside at a
greated rate. Since the only way the wave can move faster is to
have more height, the size of the wake increases.
As the boat speed increases still more, the size of this wave,
which is developing under the bow, creates a "hill" directly in
front of the boat. Soon, the boat is trying to climb up this hill
that it is pushing in front of it. The term "hull speed" is the
approximate maximum rate at which a given size hull can proceed
through the water before the hill that it is creating in front of
it becomes such an obstacle that adding additional power only
suceeds in pushing a higher hill of water.
Planing is the result of the boat actually climbing over that
hill and riding on top of it. It can take a lot of power to climb
the hill, but then very little to remain on top (at even faster
speeds).
A planing hull is one that is made to easily climb up this hill.
The hull will be flater than a displacement hull so that it will
get more lift. A full flat bottom is perhaps the extream case, but
there are a variety of V shaped hulls that will plane nicely.
Rod McInnis
Douglas F. Gibbs
rmci...@mv.us.adobe.com writes:
> Planing is the result of the boat actually climbing over that
>hill and riding on top of it. It can take a lot of power to climb
>the hill, but then very little to remain on top (at even faster
>speeds).
Not that Rod is "wrong", but I see room for misunderstanding.
To clarify, the essential thing about planing is not that it
is somehow 'balancing on the hill', but rather that it has
ceased to part (displace...push out of the way) the water, and
is now, more or less, skimming along the surface. The
resultant decrease in wetted surface, drag, and the reduced
mass of water which is displaced, means more of the power
driving the boat goes into velocity. :-)
Question of the day: Why is 'climbing out of the hole' NOT
analogous to 'breaking the sound barrier'?
(along the same lines: What would the 'sound barrier' be
for water at 22!C and 1 atmosphere, and what variables
determine this answer?)
DFG
______
e-mail: Douglas...@um.cc.umich.edu
"Air is easier to displace than liquid, hence so many drinking
problems." ;-)
Rick Emerson
S5> Message-ID: <32dib3$7...@csi0.csi.UOttawa.CA>
S5> Newsgroup: rec.boats
S5> From: s56...@aix2.uottawa.ca (Pierre McAlpine)
S5> Organization: Department of Computer Science, University of Ottawa
S5>
S5> I have been reading this newsgroup for quite a while now and the word
S5> planing has come up quite alot. Yes, I would consider myself a "novice
S5> sailer/racer" so no sarcasm please. What exactly does it mean? Does
S5> it mean that you are surfing on a wave, going faster than the waves,
S5> keeping up with the waves...or what?
S5> Also what is meant by a planing hull? Or a "planing boat" i.e. a boat
S5> that is prone to planing. What characteristic of the hull would make it
S5> a planing one? Would it be a hull which is flat-like (ex: fireball,
S5> y-flyer)?
S5> Thanks for your help,
S5>
S5> Pierre
I'm not a hydrodynamicist (if it weren't for ispell, I couldn't even
spell it!) but I think planing is the waterborne version of going
supersonic. When a boat's on plane, it's begun to get out ahead of
its bow (and quarter) wave or it's moving faster the speed its wake
moves through the water. Moving with the waves would be
"trans-sonic".
Planing can occur while surfing but planing is not surfing. My boat,
which displaces roughly 10 tons, can surf down a wave (sort of like a
kid on a sled surfs down a snowy hill... well, a sled with a real big
kid...) but I rather doubt she's ever going to plane.
As you suggest, planing is more likely to happen in a flatter hull
form than a deeply vee-ed hull form although, given enough horsepower
(no longer in sail country), a vee hull can plane.
Rick (who'd rather plane the surf in Spain in the rain than surf the
plain in the rain in Spain... now once again...)
...
* ATP/Linux 1.42 * It is easy to propose impossible remedies.
Lindsay Hughes
planing have to do with a boundry layer and not with a body immersed in its
medium. A planing vessel is essentially flying (did anybody catch the
hydroplane races in Seattle last weekend?)
Enough physics....my poor brain is stretched to the limit.
Rod Mc Innis
>In article <1994Aug12.0...@adobe.com> Rod Mc Innis,
>rmci...@mv.us.adobe.com writes:
>> Planing is the result of the boat actually climbing over that
>>hill and riding on top of it. It can take a lot of power to climb
>>the hill, but then very little to remain on top (at even faster
>>speeds).
>
>Not that Rod is "wrong", but I see room for misunderstanding.
>
>To clarify, the essential thing about planing is not that it
>is somehow 'balancing on the hill', but rather that it has
>ceased to part (displace...push out of the way) the water, and
>is now, more or less, skimming along the surface. The
>resultant decrease in wetted surface, drag, and the reduced
>mass of water which is displaced, means more of the power
>driving the boat goes into velocity. :-)
>
>Question of the day: Why is 'climbing out of the hole' NOT
>analogous to 'breaking the sound barrier'?
>
>(along the same lines: What would the 'sound barrier' be
>for water at 22!C and 1 atmosphere, and what variables
>determine this answer?)
>
>DFG
OK, I have no idea what I am talking about here, but I can't resist
a good techno-thread.
Isn't the sound barrier the shock wave that is created in front of
an aircraft? This shock wave creates a zone of compressed air, thus
creating the "barrier".
With 'climbing out of the hole' you are battling the mountain of
water that you are actually moving with force, not shock (sound). You
are also working at the exchange of two mediums; air and water. You
can climb on top of the water, you can't climb on top of the
compressed air.
AS for the sound barrier in water: If my above assumptions are
correct, then I would say water doesn't have one, since it is
essentially incompressable. If my assumptions are not correct, then I
would guess it would simply be the speed of sound through the water,
which I don't recall right now (except that it is faster than in air).
Rod McInnis
kevin weber
Its rather simple in english, probably a lot more complex in physics /
fluid dynamics. A displacement hull moves through the water by displacing
the water to either side of the hull. Such hulls are typically sharp nosed
in the horizontal and blunt in the vertical (a V from the top and more or
less straight up and down from the side). Think of a battleship or
aircraft carrier. A planning hull is designed to effectively lift the hull
on top of the water, in fact some high performance hydrofoils operate best
if almost completely in air, utilizing the the cushion of air between the
hull and the water for lift. The less contact with water the better.
Planning hulls are best characterized by highly curved front ends when
viewed from the side, with the front slopping to a flat, or nearly flat
botton.
Almost all sport powerboats are made with planning hulls. Planning
requires time to achieve, in smaller boats its a matter of seconds whereas
in larger boats, say 25 footers, it can take upwards of 20 seconds to get
to planning speed. All of which depends on hull weight, design, trim, sea
conditions and speed, among other factors. When planning speed is
attained, speed increases dramatically. For example, in my 16 footer at
3500 rpm I'll prbably chunk around at maybe 10 mph, mostly in displacement
mode. But I can increase to 4000 rpm, reach a plane, slow her back down to
3500 rpm and maintain about 15 mph. By planning I can gain about 5 mph at
3500 rpm. Not all hulls can be planning hulls, so its not just a matter of
speed. When on plane the hull must remain stable. Planning hulls usually
have a much larger beam to length ratio than non-planning hulls, for added
stability.
Does this help?
kw