Re: Sucking back your stern
- From: bookie <emily_booker@xxxxxxxxxxx>
- Date: Tue, 22 Jul 2008 05:38:53 -0700 (PDT)
On Jul 22, 12:23 am, wmart...@xxxxxxxxx wrote:
On Jul 21, 10:54 pm, "Alistair Potts" <alistair.potts
+use...@xxxxxxxxx> wrote:
I think this may have been answered before but I can't find it.
Anyway, periodically Umpires declare that they're going to impede a boat
that's not doing as it's told by driving really close behind it. This, they
say, will cause some sort of sucky effect on the water and the boat won't be
able to row as fast. Boat Race umpires are particularly prone to sternly
claiming they'll resort to this draconian measure, repeated and reported by
the press without question.
There was also a letter to the Times a few years ago saying that Boat Race
crews were effectively rowing 'uphill' because the following Armada created
the above effect.
At the various pre-race briefings where umpires would talk to us like
wayward school-children and threaten us with this sanction I would nod
sympathetically. But I never considered it any more than utter bollocks..
From my observation of leaning over the front of a launch, the effect on the
water in front of the launch is about six inches, even going quite quickly.
And while driving a launch very close to crews while coaching I've never
noticed anything. The biggest bow-wave from the biggest boats in the world
surely doesn't extend more than a couple of metres in front of the vessel -
it seems to me there's not much going on beyond that.
But who knows, maybe I was completely wrong... Maybe I should have paid more
attention. Is suck-back a) bona fide Newtonian hydrodynamics or b) hocus
pocus?
AJP
Thinking about this - wouldn't a big enough power boat, going at the
(rather sluggish) speeds of racing shells (after all, a men's 8+ only
runs at about 6 HP for a 2000 m race) create a swell off the bow,
giving the crew a wave to surf down?
What's the term - Codswallop?
W- Hide quoted text -
- Show quoted text -
would this bow wave off the launch actually build up and effectively
'push' the boat it is behind further away form it and hence make it
faster by giving it a sort of 'shove' from behind? i understand the
bit about the vacuum behind the stern of the racing shell and the
general water disturbance not being allowed to dissipate and the
vacuum closeup behind the shell again before the bow wave form the
launch gets there to disturb ti agian but surely the launch is far too
far away fromthe stern of the shell to have any effect on that water
disturbance caused by the shell as it moves along?
i don't know, just thinking out loud really
I am more concerned now with how this slipstreaming effect works on
racing snails now
bookie
.
- References:
- Sucking back your stern
- From: Alistair Potts
- Re: Sucking back your stern
- From: wmartind
- Sucking back your stern
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