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prop shape needs to be flat on windward side? | 24 comments (24 topical, editorial)

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#17)
by bob g on Thu May 15th, 2008 at 03:02:43 PM MST
(User Info)

some years ago nasa iirc had a simulator so one could generate different
profiles and then test them showing the pressure points (or lack thereof)

what is interesting is when you increase camber you move the low pressure region forward and the high pressure rearward, thus increasing the speed of the blade
and the power.

the problem is hand carving a concave windward side to a piece of wood
far easier to leave it flat on the windward side, and do a convex profile on the back

i made up some cambered fiberglass blades and did some simple windflow tests with
a smoke trail from my cigar, what the simulator illustrated i could then see quite clearly.

most if not all the commercial profiles are cambered to some extent, some dramatically so.

i would really like to see someone carve a set of heavily cambered blades
even if it were a small set to compare real world against the more standard clarkY
and other flat sided blades.

maybe one day :)

bob g

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#18)
by Norm (peppysue@suite224.net) on Thu May 15th, 2008 at 09:10:59 PM MST
(User Info)

the problem is hand carving a concave windward side to a piece of wood

Bob....No problem there...you just make a hand
tool ...scraper blade from an old handsaw grind the
tool to whatever radius you want.
( :>) Norm
[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#19)
by elvin1949 (elvin1949@yahoo.com) on Thu May 15th, 2008 at 11:48:30 PM MST
(User Info)

Norm
You took the words right out of my mouth.
I make scrapers all the time for different things when working with wood.
later
Elvin

[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#20)
by Norm (peppysue@suite224.net) on Sat May 17th, 2008 at 08:26:45 AM MST
(User Info)

Watch it Elvin usually only old timers know about
stuff like custom hand woodworking tools !
BTW liked that Billion thing in the E-Mail !
( :>) Norm
[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#21)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Sat May 17th, 2008 at 12:16:27 PM MST
(User Info)

A useful search term is "draw knife"

http://www.endtimesreport.com/pictures/draw_knife.jpg

You could make one with a perfect size of handles and frame for your size of projects, and make the blades separate, so they could be changed to different shapes, or easily replaced when sharpening wears them down too low.

[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#23)
by elvin1949 (elvin1949@yahoo.com) on Sat May 17th, 2008 at 03:35:25 PM MST
(User Info)

HF sells draw knifes and spokeshaves.
Both good woodworking tools.
later
Elvin

[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#22)
by elvin1949 (elvin1949@yahoo.com) on Sat May 17th, 2008 at 03:33:01 PM MST
(User Info)

Norm
I thought you would.My sister is always sending me junk.Most of the time i through it away.
Have fun
later
Elvin

[ Parent ]

Re: prop shape needs to be flat on windward side? (3.00 / 0) (#24)
by Dave B on Mon May 19th, 2008 at 02:58:22 AM MST
(User Info) http://www.madbbs.com/users/bruggelog

Hi Bob,
Take a look here at http://www.royalfabrication.com/index.htm That's me standing next to my 18' hybrid Wincharger. Dave Moller carves these Gottigen 222 profile blades on his custom carving machine and like one would expect, they really perform. No twist, no taper, constant pitch very similar to the Bergey machines. It's no coincidence a blade profile similar to that used for decades continues to run on the most popular commercial machine today. Dave B.

[ Parent ]

prop shape needs to be flat on windward side? | 24 comments (24 topical, 0 editorial)

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