Re: end plates on oars?
You would want the "end plates" on the sides of the oars, I think, as if
I recall correctly there is or can be significant motion endwise thru
the water and even some lift. (Think about the geometry of the oar's
motion.) As an undergrad I participated in an experiment on oar blade
shapes, but I'm d!@#$$d if I can remember what we found. Certainly
nothing very surprising. I once used a set of oars whose blades were a
bit wider than normal, and no longer than they were wide. Felt funny,
but worked fine on an Alden Ocean Shell. (Ocean shell my a$%, they can
hold an awful lot of water when swamped. A regular scull can be (fairly)
easily reboarded if the oars are still in the locks.) Aspect ratio much
higher than normal oars. Perhaps this is why the hatchet oars are
popular also. I'm guessing that most of the force is from drag, tho.
Keep in mind that anything that gives your oars less slip in the water
may give them more drag in the air, although I suppose a really serious
pulling boat might have a set of shorter oars for upwind slogs.
But it's probably an easy experiment to do. Maybe not so easy to measure
the results if they turn out to be subtle.
I recall correctly there is or can be significant motion endwise thru
the water and even some lift. (Think about the geometry of the oar's
motion.) As an undergrad I participated in an experiment on oar blade
shapes, but I'm d!@#$$d if I can remember what we found. Certainly
nothing very surprising. I once used a set of oars whose blades were a
bit wider than normal, and no longer than they were wide. Felt funny,
but worked fine on an Alden Ocean Shell. (Ocean shell my a$%, they can
hold an awful lot of water when swamped. A regular scull can be (fairly)
easily reboarded if the oars are still in the locks.) Aspect ratio much
higher than normal oars. Perhaps this is why the hatchet oars are
popular also. I'm guessing that most of the force is from drag, tho.
Keep in mind that anything that gives your oars less slip in the water
may give them more drag in the air, although I suppose a really serious
pulling boat might have a set of shorter oars for upwind slogs.
But it's probably an easy experiment to do. Maybe not so easy to measure
the results if they turn out to be subtle.
>Bruce Hector wrote:snip
>snip
>It occured to me, that if end plates on shallow rudders, as Phil
>Bolger draws on Bobcat, Micro, Chebacco, etc. reduced slipping and
>made them more effective.
>
>That, well, perhaps tiny end plates epoxied to the end of my oars
>would also reduce blade slip and make them more efficient also.
>
>
>
Finally, a topic I have some knowledge of, rather than just an opinion,
which is the usual state of affairs.
While end plates on oars would undoubtedly make it harder to get them in
and out of the water gracefully, the big problem would be the way an end
plate would interact with the blade as it moves away from the side of the
boat and then back in during the stroke. Imagine yourself looking down on
a rowing boat from a bridge, ignore the boat and just look at the blade of
the oar. You will see that the blade is quite a lot closer to the hull at
the catch and at the finish than in the middle of the stroke (this is
particularly true in a sliding seat boat because of the longer reach it
allows). The blade also swings through almost 90 degrees while it is in
the water. A spoon blade with a moderate curve allows all that slipping
sideways and turning to happen smoothly while still having a good "bite" on
the water. I suspect the end plate would cause a lot of turbulence in the
course of the stroke.
Racers in shells and flatwater canoes seem to use very "chunky"
blades--very low aspect ratio--with quite a lot of spoon shape. By
comparison, northern seal hunters and traditional boat enthusiasts with
relatively heavy boats and heavy loads, long voyages at moderate levels of
effort in a wide variety of conditions, seem to favor long slender straight
blades. I would be inclined to believe they all know what they are doing,
even if they are not able to explain why.
Best,
George
At 03:46 AM Tuesday 2/10/2004, you wrote:
which is the usual state of affairs.
While end plates on oars would undoubtedly make it harder to get them in
and out of the water gracefully, the big problem would be the way an end
plate would interact with the blade as it moves away from the side of the
boat and then back in during the stroke. Imagine yourself looking down on
a rowing boat from a bridge, ignore the boat and just look at the blade of
the oar. You will see that the blade is quite a lot closer to the hull at
the catch and at the finish than in the middle of the stroke (this is
particularly true in a sliding seat boat because of the longer reach it
allows). The blade also swings through almost 90 degrees while it is in
the water. A spoon blade with a moderate curve allows all that slipping
sideways and turning to happen smoothly while still having a good "bite" on
the water. I suspect the end plate would cause a lot of turbulence in the
course of the stroke.
Racers in shells and flatwater canoes seem to use very "chunky"
blades--very low aspect ratio--with quite a lot of spoon shape. By
comparison, northern seal hunters and traditional boat enthusiasts with
relatively heavy boats and heavy loads, long voyages at moderate levels of
effort in a wide variety of conditions, seem to favor long slender straight
blades. I would be inclined to believe they all know what they are doing,
even if they are not able to explain why.
Best,
George
At 03:46 AM Tuesday 2/10/2004, you wrote:
>Message: 15
> Date: Mon, 9 Feb 2004 17:04:46 -0500
> From: "John Bell" <smallboatdesigner@...>
>Subject: Re: end plates on oars?
>
>You gotta be careful. The tricky part is when the oars enter and leave the
>water. Splashing on entry and digging up a lot of water on exit is really
>hard on a rowers efficiency. I think it's safe to say if you don't see them
>on racing shells and sculls, then they are proabably not a good idea.
>Spooned blades are almost certainly a better solution.
>
>Although it seems like there would be more power from a cupped blade, in
>reality the best shape is dead flat or a slight dihedral across the narrow
>dimension and slightly curved in the long dimension. Also, the shape of the
>back of the blade makes a huge difference.
>
>
>
>
>----- Original Message -----
>From: "Bruce Hector" <bruce_hector@...>
>To: <bolger@yahoogroups.com>
>Sent: Monday, February 09, 2004 4:28 PM
>Subject: [bolger] end plates on oars?
>
>
> > Just got back from a nice two hour pull on the tropical waters of the
> > Intracoast Waterway here at Indian Rocks Beach, (eat yer' heart out
> > Peter Lenihan) Florida in my Welsford Seagull. I was rowing my Mommy
> > about, wonderful.
> >
> > It occured to me, that if end plates on shallow rudders, as Phil
> > Bolger draws on Bobcat, Micro, Chebacco, etc. reduced slipping and
> > made them more effective.
> >
> > That, well, perhaps tiny end plates epoxied to the end of my oars
> > would also reduce blade slip and make them more efficient also.
> >
> > Has anyone tried such a thing?
> >
> > If it didn't help, it would be easy to saw them off, and end up with a
> > set of oars 1/2 inch less than you started out with.
> >
> > Bruce Hector
> >http://groups.yahoo.com/group/SunCoastRowingClub/
> > A recreational rowing club that meets every Wednesday eve at a local
> > pub with excellent small boat facilities.
You gotta be careful. The tricky part is when the oars enter and leave the
water. Splashing on entry and digging up a lot of water on exit is really
hard on a rowers efficiency. I think it's safe to say if you don't see them
on racing shells and sculls, then they are proabably not a good idea.
Spooned blades are almost certainly a better solution.
Although it seems like there would be more power from a cupped blade, in
reality the best shape is dead flat or a slight dihedral across the narrow
dimension and slightly curved in the long dimension. Also, the shape of the
back of the blade makes a huge difference.
water. Splashing on entry and digging up a lot of water on exit is really
hard on a rowers efficiency. I think it's safe to say if you don't see them
on racing shells and sculls, then they are proabably not a good idea.
Spooned blades are almost certainly a better solution.
Although it seems like there would be more power from a cupped blade, in
reality the best shape is dead flat or a slight dihedral across the narrow
dimension and slightly curved in the long dimension. Also, the shape of the
back of the blade makes a huge difference.
----- Original Message -----
From: "Bruce Hector" <bruce_hector@...>
To: <bolger@yahoogroups.com>
Sent: Monday, February 09, 2004 4:28 PM
Subject: [bolger] end plates on oars?
> Just got back from a nice two hour pull on the tropical waters of the
> Intracoast Waterway here at Indian Rocks Beach, (eat yer' heart out
> Peter Lenihan) Florida in my Welsford Seagull. I was rowing my Mommy
> about, wonderful.
>
> It occured to me, that if end plates on shallow rudders, as Phil
> Bolger draws on Bobcat, Micro, Chebacco, etc. reduced slipping and
> made them more effective.
>
> That, well, perhaps tiny end plates epoxied to the end of my oars
> would also reduce blade slip and make them more efficient also.
>
> Has anyone tried such a thing?
>
> If it didn't help, it would be easy to saw them off, and end up with a
> set of oars 1/2 inch less than you started out with.
>
> Bruce Hector
>http://groups.yahoo.com/group/SunCoastRowingClub/
> A recreational rowing club that meets every Wednesday eve at a local
> pub with excellent small boat facilities.
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax:
(978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
>
>
>
>
Just got back from a nice two hour pull on the tropical waters of the
Intracoast Waterway here at Indian Rocks Beach, (eat yer' heart out
Peter Lenihan) Florida in my Welsford Seagull. I was rowing my Mommy
about, wonderful.
It occured to me, that if end plates on shallow rudders, as Phil
Bolger draws on Bobcat, Micro, Chebacco, etc. reduced slipping and
made them more effective.
That, well, perhaps tiny end plates epoxied to the end of my oars
would also reduce blade slip and make them more efficient also.
Has anyone tried such a thing?
If it didn't help, it would be easy to saw them off, and end up with a
set of oars 1/2 inch less than you started out with.
Bruce Hector
http://groups.yahoo.com/group/SunCoastRowingClub/
A recreational rowing club that meets every Wednesday eve at a local
pub with excellent small boat facilities.
Intracoast Waterway here at Indian Rocks Beach, (eat yer' heart out
Peter Lenihan) Florida in my Welsford Seagull. I was rowing my Mommy
about, wonderful.
It occured to me, that if end plates on shallow rudders, as Phil
Bolger draws on Bobcat, Micro, Chebacco, etc. reduced slipping and
made them more effective.
That, well, perhaps tiny end plates epoxied to the end of my oars
would also reduce blade slip and make them more efficient also.
Has anyone tried such a thing?
If it didn't help, it would be easy to saw them off, and end up with a
set of oars 1/2 inch less than you started out with.
Bruce Hector
http://groups.yahoo.com/group/SunCoastRowingClub/
A recreational rowing club that meets every Wednesday eve at a local
pub with excellent small boat facilities.