Some good prop articles here as well as the pop bottle prop form
;
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http://www.pensacolafreeflight.org/page5/page5.html_
(
http://www.pensacolafreeflight.org/page5/page5.html)
Rick Pangell
Editor of "The Max-Out" Newsletter of
The Magnificent Mountain Men FF Club of Colorado
In a message dated 3/5/2011 1:48:35 A.M. Mountain Standard Time,
hermanna_at_hotmail.com writes:
In 1987 I wrote an article showing how to generate the centerline for a
helical pitch distributuion on a cylindrical or conical form. Saw little
use for it as it lacked the stiffness of the 3D shell with the helical form.
Also included an equation for camber useful for selecting the form:
Camber = Chord / 4 Diameter
Don Lindley raked me over the coals for not saying it was an
approximation, but he liked the 2D of the cylinder for flaring on LPP.
The article included an isometric view of different pitches. It appeared
in the Phoenix MAC newsletter & I think Model Builder picked it up. Home
fire wiped out any copies I may have had.
Is very simple. Y-axis = Pitch/ 2 pi X-axis = Prop Radius ( 0, 25%,
50%, 75%, 100% )
Connect apex to all Radii to show all angles.
Center the form Dia on the apex and the intersection w/angle lines shows
where Centerline goes. Centerline is curved in scimitar fashion and results
in interesting design.
Helical forms are so easy with hot wire foam or fanned strips + an
undercamber form & is my preference.
Jim Richmond used the same helical form for all his props, including
Atrium Insect (AROG) and Starwalker (90 cm F1D).
He moved the small blade closer to the hub to get more twist. Seemed to
work as both set records.
Good luck,
H
Received on Sat Mar 05 2011 - 15:36:57 CET