I finally post some pictures of the Speed Dailer like fin set I’m making.
The plan is to use it both as a quad and thruster set. The back fins are double foiled so they can be used as a small back fin.
I’m also curious to use the smaller back fin in combination with my favourite FCS H2 large set to loosen it a bit in smaller surf.
The fins are relatively thick since I’m using the 12% thickness to chord length ratio.
The fins will be build using a 1mm glassfibre panel at the inside (front fins) or center (back fins) of the fins. Poplar plywood will be glued to these panels.
Here is the profile as produced by the finFoil application:
Thanks Hans for showing us your method for building fins and the neat software. I like how you stack the pieces to save time grinding and use nails for locating pins. Which glue or resin do you use for combining the layers?
return of the layers approach. awesome. your software makes it possible.
my take from the layers approach was mixed, like most things in life. one, that to fair the fin the way i wanted, i had to mud it up a lot to bridge the contour steps. i wondered how true to form i really was. then i made lots of grinding dust and wondered how little of all that mud was left. in the end, i determined that for simple shapes, one could grind the shape fairly accurately from a solid panel much more quickly, but for complex contours, the step approach was the only way to get your digital form into physical space.
my next thought was to use a solid core and glue stepped “cheeks” onto the core like building up a rudder or centerboard on a sailboat-- the core being the same thickness dimension as the tab and the cheek(s) the meat to fair in the fat parts of the curve. the edge is fragile and easy to grind away, plus you need the core strength, so a hard center (or side for flat-sided twins) is the thing, but the cheek is where you have to do a lot of the foil shaping. it goes from foam to cork to wood to solid glass in terms of density, so perhaps the layered density approach which defined the outline well with a glass panel base, but then stacked smaller outlines from progressively less dense toppings. you get ruggedness and preserved dimension where you need it, and ease of fairing without much mud-slake on the cheek segments. plus your tab just fits without a lot of finicky thicknessing.
well, it looks like you’re onto the same path. thanks for being part of our crowdsourced research group. haha. i’m going to try some layered density fins myself soon for a quad i’m about to glass. great stuff and a great software tool. keep it up.
-cbg
<this post was edited because i was not paying attention to his layered density approach when i first posted.>
The stacked layup is a great idea. And I would imagine having a thin glass panel inbetween the wood will help get that sharp trailing edge nice and, well, sharp.
So I’m trying to understand what cbg has said, you want to layer less dense and more easily shaped materials on the outside layers, while the more dense and solid material will serve as the core. Which is lightly altered in terms of thickness and shape anyway? Cause if so, that sounds like a great idea. Maybe I’ll try that with wood, a more dense wood core and a much lighter species on the outsides for easy shaping.
This technique doesn’t save time compared to a full panel. The cutting and glueing of the layers consumes more time than just grinding the foil.
The reason I use this technique is accuracy.
The glass panel is mainly used for durability. Since the glass layer is the biggest, this layer will get the impact on collision. This way chances are smaller that there will be water intrusion in the wood.
I’m going to use 5 minute epoxy as glue for the layers. There was a sale of this stuff, normally I would use (cheaper) regular epoxy.
