28 Jun 2004 00:20:57
Mel Harbour
Wind Correction Factors

Just wondering whether anyone had any decent data on how to correct
times for pieces done in different wind conditions. Clearly head
winds slow you down and tail winds speed you up, but by how much? If
you know the boat type, weight of rower/boat, strength of the wind and
speed of the boat, surely it must be possible to calculate at least an
estimate of the correction factor required?

Mel


28 Jun 2004 12:36:22
Richard Packer
Re: Wind Correction Factors

On 28 Jun 2004 00:20:57 -0700, melvynharbour@hotmail.com (Mel Harbour)
wrote:

>Just wondering whether anyone had any decent data on how to correct
>times for pieces done in different wind conditions. Clearly head
>winds slow you down and tail winds speed you up, but by how much? If
>you know the boat type, weight of rower/boat, strength of the wind and
>speed of the boat, surely it must be possible to calculate at least an
>estimate of the correction factor required?

There's some info here http://www.vierzonder.nl/correctlftenboot.html
that might be useful - designed to calculate time corection factors
for boat types, sex and age, but includes an addidtional wind
correction factor for the smaller boats.

Richard


28 Jun 2004 07:42:28
Mark Ruscoe
Re: Wind Correction Factors

melvynharbour@hotmail.com (Mel Harbour) wrote in message news:<b7e65403.0406272320.553b8ad2@posting.google.com >...
> Just wondering whether anyone had any decent data on how to correct
> times for pieces done in different wind conditions. Clearly head
> winds slow you down and tail winds speed you up, but by how much?

I think I've got some notes from a lecture by Klaus Filter a few years
ago which include some graphs showing effects of windspeed,
presumeably from some old GDR reseach, but it's buried in a pile of
rowing stuff somewhere. Perhaps I should have had a sort-out before
buying half a dozen or so books in Henley at the weekend. Doubt I'll
have time to have look for it until after HRR.


29 Jun 2004 10:07:56
Bill Atkinson
Re: Wind Correction Factors

melvynharbour@hotmail.com (Mel Harbour) wrote in message news:<b7e65403.0406272320.553b8ad2@posting.google.com >...
> Just wondering whether anyone had any decent data on how to correct
> times for pieces done in different wind conditions. Clearly head
> winds slow you down and tail winds speed you up, but by how much? If
> you know the boat type, weight of rower/boat, strength of the wind and
> speed of the boat, surely it must be possible to calculate at least an
> estimate of the correction factor required?
>
> Mel

Mel:
See my new page <http://www.atkinsopht.com/row/windfact.htmcolor=#0000FF> > which
seeks to encourage someone to determine the air resistance of shells.
Something I believe never to have been done.
Once resistance factors for various shell configurations are known
corrections can easily be estimated by using the computer model
ROWING.
Regards,
Bill


29 Jun 2004 14:16:40
William R. Platt
Re: Wind Correction Factors


"Bill Atkinson" <watkinson@compuserve.com > wrote in message
news:4d4dec30.0406290907.11590d06@posting.google.com...
> melvynharbour@hotmail.com (Mel Harbour) wrote in message
news:<b7e65403.0406272320.553b8ad2@posting.google.com >...
> > Just wondering whether anyone had any decent data on how to correct
> > times for pieces done in different wind conditions. Clearly head
> > winds slow you down and tail winds speed you up, but by how much? If
> > you know the boat type, weight of rower/boat, strength of the wind and
> > speed of the boat, surely it must be possible to calculate at least an
> > estimate of the correction factor required?
> >
> > Mel
>
> Mel:
> See my new page <http://www.atkinsopht.com/row/windfact.htm>which
> seeks to encourage someone to determine the air resistance of shells.
> Something I believe never to have been done.
> Once resistance factors for various shell configurations are known
> corrections can easily be estimated by using the computer model
> ROWING.
> Regards,
> Bill

I estimated the air drag coefficient of a pair of oarsmen a few years
ago---but it turned out that I underestimated the effect---they went even
slower than I predicted :-(


regards,


Bill Platt




29 Jun 2004 12:01:55
O. Korol
Re: Wind Correction Factors

Richard Packer < > wrote in message
<snip >
> There's some info here http://www.vierzonder.nl/correctlftenboot.html
> that might be useful - designed to calculate time corection factors
> for boat types, sex and age, but includes an addidtional wind
> correction factor for the smaller boats.
<end >

The table has wind correction factor for small boats but not big
boats. Is it because the experiment was not done with big boats? Or
because the big boats are less affected by the wind?


29 Jun 2004 20:41:53
Carl Douglas
Re: Wind Correction Factors

Mel Harbour <melvynharbour@hotmail.com > writes
>Just wondering whether anyone had any decent data on how to correct
>times for pieces done in different wind conditions. Clearly head
>winds slow you down and tail winds speed you up, but by how much? If
>you know the boat type, weight of rower/boat, strength of the wind and
>speed of the boat, surely it must be possible to calculate at least an
>estimate of the correction factor required?
>
>Mel

This is a $64,000 question. It is under-researched and hard to assess.

Wind drag comes from sum of the individual contributions from the
obstruction of the flow around & over the boat, blades, riggers & crew -
in short, everything above waterline. Put simply, the net crew power
(roughly 2/3 of the actual power applied, but depending significantly
upon technique), divided by the sum of wind & water resistances, gives
you the boat speed. However, calculating this is highly complex
iterative process.

The stuff we stick above water (listed above) is mostly far from
aerodynamically slick, unlike the underwater stuff. We know that
head-winds & wave impacts slow us down, but we tend to ignore these
factors as mere side-issues.

It is more complex to calculate wind drag for an eight than for a single
because this has to take account of the effect of one body
wind-shielding the next, & the effects of wind swirling inside the hull.
So a dead-ahead wind may actually cause less drag than one which is just
a few degrees to the side.

The consequences of wind drag depend not only on the added resistance
due to the causes described above, but further drag may also be induced
by the tendency of a side or quartering wind, whether head or tail, to
push the boat sideways, increasing the normal level of drag in the water
at that speed.

So, there are no simple answers.

Cheers -
carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)



29 Jun 2004 18:05:23
William R. Platt
Re: Wind Correction Factors


"Carl Douglas" <Carl@carldouglas.co.uk > wrote in message
news:rdmYn2BBYc4AFw$v@rowing-cdrs.demon.co.uk...

<SNIP >
>
> So, there are no simple answers.
>
>
Amen.

Regards,

Bill




30 Jun 2004 09:34:20
Neil Wallace
Re: Wind Correction Factors

Carl Douglas wrote:
> So, there are no simple answers.

how about http://www.newswire.ca/images/rtphotos/Photo-3505.jpg ??





30 Jun 2004 11:24:55
Jay
Re: Wind Correction Factors

Neil Wallace wrote:
> Carl Douglas wrote:
>
>>So, there are no simple answers.
>
>
> how about http://www.newswire.ca/images/rtphotos/Photo-3505.jpg ??
>
>
>
Are those the "rip strips" (as far as I can recall) on the loom of the
blades? Or is it a similar drag reduction device? Interesting to see if
it works... (Still doesn't help spotting crews on the outside :) )

Jay


30 Jun 2004 12:34:23
Neil Wallace
Re: Wind Correction Factors

Jay wrote:
> Neil Wallace wrote:
>> Carl Douglas wrote:
>>
>>> So, there are no simple answers.
>>
>>
>> how about http://www.newswire.ca/images/rtphotos/Photo-3505.jpg ??
>>
>>
>>
> Are those the "rip strips" (as far as I can recall) on the loom of the
> blades? Or is it a similar drag reduction device? Interesting to see
> if it works... (Still doesn't help spotting crews on the outside :) )
>
> Jay

no, it's the Canadians who have anounced their plan to race in wind cheating
lyrca hoods.
Perhaps they haven't read that the smart money's on a tailwind.




30 Jun 2004 08:02:39
PaulS
Re: Wind Correction Factors

melvynharbour@hotmail.com (Mel Harbour) wrote in message news:<b7e65403.0406272320.553b8ad2@posting.google.com >...
> Just wondering whether anyone had any decent data on how to correct
> times for pieces done in different wind conditions. Clearly head
> winds slow you down and tail winds speed you up, but by how much? If
> you know the boat type, weight of rower/boat, strength of the wind and
> speed of the boat, surely it must be possible to calculate at least an
> estimate of the correction factor required?
>
> Mel

See, now I was simply going to say, "No.", but then probably get
attacked for not using more words to say the same thing. [;o)

Although it sounds reasonable, I'm not sure that a tailwind will speed
everyone up, a lot depends on how the individual reacts to it.

Howz work life treating you BTW?

- Paul Smith


30 Jun 2004 15:42:19
Red and White
Re: Wind Correction Factors

"Neil Wallace" <rowing.golfer*NOSPAM*@virgin.net > wrote in message news:<2kfmptF1mf5tU1@uni-berlin.de>...
> Jay wrote:
> > Are those the "rip strips" (as far as I can recall) on the loom of the
> > blades? Or is it a similar drag reduction device? Interesting to see
> > if it works... (Still doesn't help spotting crews on the outside :) )
> >
> > Jay
>
> no, it's the Canadians who have anounced their plan to race in wind cheating
> lyrca hoods.
> Perhaps they haven't read that the smart money's on a tailwind.

Did anyone read Yoda's comments regarding the suits in:
http://www.theglobeandmail.com/servlet/ArticleNews/TPStory/LAC/20040624/ROWING24/TPSports/Other

Reading between the lines it seems that he is not a big fan. And if
the Dutch (?) tried them and rejected them a few years ago it begs the
question: Are the Canadians really going to use them in Athens?

Alternatively, maybe the hoods puff up with a tailwind, effectively
becoming a mini spinnaker?

Red.


01 Jul 2004 13:22:12
Ewoud Dronkert
Re: Wind Correction Factors

On 30 Jun 2004 15:42:19 -0700, Red and White wrote:
> the Dutch (?) tried them and rejected them a few years ago

I don't think they rejected them, at least not the crew (LM4-) that
tried them, but the problem was (and is I suppose) that the entire
national team must row in the same uniform (hence the name uniform).
Other crews weren't prepared to use them, so the 4- abandoned them too.
That, and I heard they found them quite warm.

http://www.nlroei.nl/displayarticle-1120.html