I want to try to foil wood fins. Looked around here a bit and found some good stuff, but was hoping to get some more input as far as tools, technique, materials, any help would be great.
I'm a neophyte at wood fins, but what I've found works for me is leaving lots of excess wood above the fin makes for handy clamping / holding room. The first ones I did were cut to final shape, and what a bear to work with! My favorite tool for foiling is a 4" angle grinder with a rough grit sanding disc, to be handled with a very light touch.
Working with plywood makes for good practise because you can visually see your consistency of foil as you work your way through the layers. As I work, I try to keep in mind the foil runs parallel to the board, its easy to forget as you work the foil down into the curved bottom of the fin.
I'm sure more experienced foilers can add / correct what I've written, but thats the little I have to offer!
An angle grinder/hard disc is best tool for roughing. Soft pads to blend, but it's easy to catch edge and tear up pad. Make ''passes'' with grinder, like rail bands in a blank. Most foilers take meat out of rear first, one big cut to establish most of the foil. Another ''band'' to trailing edge, then one forward to blend into locus of thickness. Base-to-tip thickness taper at this point, unless you just want to rely on intersection of bands to accomplish this. In wood you could do this with a block. Leading edge last, a primary 45 degree cut, then blend. Again, in wood, this could be done with block.
Every fin thread I go on, I advise people to cut their blanks a little oversized at base. Continue the outline of fin, foil it, then cut base off last. It makes the corners on base come out much cleaner. I learned that one from Jim Phillips 30 years ago.
Marking tools and scrapers.
Huck mentioned using plywood because the thickness topography of the foil is revealed as you work through the layers.
However, fairing out the foil - especially on the trailing edge - will lead to longer seperations which is fine if you have a good eye but…
Rough your blank using any of the above mentioned methods including also a good set of bastard files.
If you really want to dial in the foil match both sides using something like an adjustable T-square, accuscribe, multiscribe, calipers etc. to measure from the edge into the fin and marking to deliniate thickness lines (which are akin to topographic lines on a map).
If you don’t use marking tools, you might want to make a set of foil gauges which are cross section templates of the fin foil at fixed points. Rough the fin then dial in each side using the foil gauge. If you use a flate scraper plate and grind the foil gauge to fit the widest point of the fin you can draw-scrape down the fin after roughing leaving a near finished surface in the process of foiling the fin.
Scrapers are such underrated tools these days and whipping up custom profiles is a breeze. Viva La Burr!
Mcclamped, dig through some of these Google Search results:
Google Search on Swaylocks for wood fin foil
Mark your max thickness on the fin. 25-30% of chord is a good rough number. This gives you a visual reference of where the high point is and where to blend the leading edge foil with the trailing edge foil.
finally finished this one
Sweet looking fin Huck! It looks like it has a nice foil.
Here's my latest wood fin. I haven't glassed it yet.
Here's the link to the build thread.
http://www2.swaylocks.com/forums/fin-building-project
the hidrodynamic e aerodynamic foils used for fins are the NACA 008, 007, 006 in yachting
here´s the place to get the coordinates of each one:
....ae.illinois.edu/m-selig/ads/coord_database.html