On Monday, 2 November 2020 at 05:37:52 UTC-7, carl wrote:
I take your point on weeds, but don't understand why fins should be getting deeper - which is what James says is happening.
A more sweptback shape, without the sharpening (it's pointless - it doesn't reduce drag but does impair performance) of the leading edge, would be better at shedding weeds, not to mention the polythene bags & other detritus
I recall one day on the Avon in Christchurch, NZ, when one 8+, rowed by the OURC men, shredded three coxswains' hands right to the tendons when they reached under the boat to clear weeds off the sharpened fin. Not my program but I went over with a fileand took the edge off the fin. Oddly nobody else cut their hands. The crew still won their race if I remember correctly (it was pre-2000). One of the stupidest things I've ever seen is people sharpening a fin on a boat.
No serious water vehicle should ever have a flat plate fin, and
definitely not a flat plate rudder
On Wed, 06 Jan 2021 12:45:57 -0800, Jake Frith wrote:
No serious water vehicle should ever have a flat plate fin, andBut if the boat is yellow all that scientific malarkey is rendered null
definitely not a flat plate rudder
and void. With your considerable knowledge of fluid dynamics you must
surely realise that?
--
Henry Law n e w s @ l a w s h o u s e . o r g
Manchester, England
No serious water vehicle should ever have a flat plate fin, and
definitely not a flat plate rudder
On 08/01/2021 15:31, Jake Frith wrote:
No serious water vehicle should ever have a flat plate fin, andHi Jake -
definitely not a flat plate rudder
Might I respectfully disagree with your first point?
A (non-steering) fin - as on a 1x - serves to prevent the boat from
yawing between strokes. (Yawing is a shell's tendency to swing
off-course due to its centre of drag being ahead of its centre of mass.)
Over a rather narrow range of angles of attack a flat plate is as
effective as any aerofoil-section fin in generating lateral lift. But
once that limited range of attack (maybe +/- ~2 degrees) is exceeded it stalls, progressively losing lift.
This is just what you want with an oar-steered boat - a system that
stops resisting when you need to change direction where an
aerofoil-section fin keeps resisting all efforts to turn or manoeuvre.
For any steering element, then I do agree that you need a
properly-shaped thick foil, the last thing you need being for your
rudder to stall. And for the flat fin (say 2mm thick) you should still
have a radiused leading edge & a sharpened trailing edge.
Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: ca...@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells
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