Note: Tom Hamernik has contributed
a custom made spreadsheet which you are free to
download (link at bottom of
page) and use to calculate segments for making foil
section rudders and centerboards. We are very grateful
to Tom for this contribution to boatbuilders everywhere.
Feedback solicited.
Thought you might like to see the spreadsheet I am
using to calculate the strip widths for my Pathfinder's
rudder and centerboard. It's based on the NACA four-digit
foil with no camber (Section type 00XX).
It could easily be adapted for Warren Messer's approach,
(Part-1
& Part-2)
where the plies run forward and aft, as opposed to
athwartships as JW shows.
I have it calculate the width of the strips so that
when assembled, you plane off the corners, rather
than fillet the low spots like in WM's approach.
Screenshot from Spreadsheet
The reason I created it was to:
1. Check/reverse engineer JW's rudder and centerboard
foil designs
2. Calculate the precise widths of strips needed
to buildup the foil in an attempt to lessen the work
needed to shape the foil by eliminating some of the
wood prior to glueing. This information can be scaled
directly off the print. But, it's easy enough for
me to generate a table of values.
3. Educate myself on NACA foils (at least the 4
& 5 digit series)
I dressed up my spreadsheet a bit to share with others.
With it, you can calculate virtually any four- or
five-digit NACA foil with zero camber (symmetrical
NACA foils). In this regard, it may be more user-friendly
relative to the approach WM suggests. But, it would
have to be modified to produce a table of ply sizes
for plies running parallel to the centerline of the
foil, rather than transverse (like JW's foils).
It could also be modified to produce a table of strip
widths to be filled, rather than cut down, if you
really like that approach.
The bottom line - if you think
it's interesting, use it however you like.
Update:
Via the link below, you will find a large (3 MB)
excel file that has the new version of FoilStip. There
are two new tabs to play with - one will calculate
lengthwise strips that will require planing to final
foil shape. The other will calculate lengthwise strips
to be filleted (like the Warren Messer approach; Part-1
& Part-2).
Sorry about the file size. Because the solution to
the lengthwise strips approach requires solving an
eighth-order polynomial, it requires a hell of a lot
of calculations, yielding a large file size.
Screenshot from Updated Spreadsheet
- Ply-Fillet
Screenshot from Updated Spreadsheet
- Ply-Plane
Also by Tom Hamernik:
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