@westcoastguy
I was having issues with the trailing edges of the bsplines as well and being the lazy knuckle dragging chimp that I am, I decided to stick with d-wires, so I never really resolved the trailing edge issue myself. But good to see the experts on this forum leading the charge.
Designing the dolphin style fins is a bit tricky. There are two ways I do it.
1. Just using FreeCAD (and Inkscape)
1. I use Inkscape to design the outline as an SVG and then import that into FreeCAD.
2. I scale the outline to the fin depth that I want.
3. I then pick a point on the fin base that corresponds to the furtherest (is that a word) point of the fin tip and draw a number of lines from this point to past the leading edge of the fin. Think of dividing a pie into pieces using lines from the pie centre. Where each of these lines intersects the leading and trailing edge of the fin, I use the measure utility to determine the length of the foil over that line. The line is just used for measuring purposes. I import the foil using the macro with the measurement and position it over the line between the leading and training edges over the line. The reason I use this method is so that the thickness of the fin tapers gradually to the tip without any thick spots.
4. I repeat this for each line.
5. Loft the foils.
6. Add the fin tabs.
I have been using D-wires and machining the fins on my CNC. The surface finish is good.
2. Use Finfoil to design the fin and import that STL into FreeCAD to add the fin tabs and scale.
Hope this makes sense. If it doesn't drop me a PM on
woodbuddha1@gmail.com
WB