I glued up another board in hopes of trying again, then I decided to try to finish this one anyways.
The mold had 3 coats of PVA. I gave it one coat of wax including the top where I would spill resin. I spent some time getting it in the corners and around the dowel pins and holes and then removed the excess.
I mixed 50g / short 2 oz of Resin Research epoxy but could have gotten by with 30g / 1oz. The cloth is 4oz. I snapped off the wooden screw tab so it could be remade with cloth and resin.
All was going fine until I used a chisel to do the job of a parting wedge, resulting in chips in the mold and a 2 inch / 5cm cut on my thumb.
Pics below. Next steps will be to sand off the machining and molding extras and to glass the foil.
Those photos explain things well. I am assuming that when you glass the foil, you will go down over the base. Is the molded base thinner than what the finished base will be, to allow for the glass that will cover it when glassing the foil? Also, did you put any fiberglass or fin rope or something else in the screw tab, or is the strength solely from the 4oz glass on the sides? I’m curious as to whether that will be strong enough.
I really like the design of your mold; much better than what I came up with. I’m going to make one like it, but out of HDPE.
So after putting two layers of 4oz on the foil, did you also put a couple of layers in your mold? I just put in a bunch of cut up scraps, but think I need a better way.
Thanks Ricky. The left one was molded before the glassing. It had glass in the mold around the sides of the fin base and some glass wadded up in the tab area for the screw and plate. It could have used more organized layers of cloth in the tab and more overlap to the base…but I think I’ll have other problems if I whack the fin hard enough to cause it fail as-is.
I did another one sort-of ‘Rohan style’ http://www.swaylocks.com/forums/wooden-core-single-fin-build-method that has a small bar of FR4 inset for the screw and plate. The FR4 is the lighter green in the pic. I used Superglue to tack the bar to the fin before going into the mold and got some cloth and tinted resin around that too. The big wooden one is going to get a similar treatment.
I am still tuning the mold, hoping to get it to size so that very minimal sanding is required for a nice fit.
If so, are you happy to share the file? I’m looking for a gullwing fin file so that I can try to print a shell of the fin. As in: Print the mould as a less than 1mm thick layer of material, then fill it with resin and leave the 3D printed shell in place as the outside layer of the fin.
The finFoil program is easier than any other CAD or modelling software I have used. A basic fin only takes a couple of minutes to get from idea to STL. Get the desktop version of finFoil, set up the basic parameters, drag in a reference image, and tweak the design until it is ready. Save it. Then run it through the online foil-to-STL converter.
Then I use OpenSCAD to bring in the finFoil STL file, scale it to inches, and add whatever tab or base or mold body needed… Code and picture below.
At this point I normally export another STL file (foil+tab) out of OpenSCAD to be ran through the milling software.
I imagine it would be similar going into the slicing software for 3D printing.
I finaly gave finFoil a go and it is spectacular! Great program
My only gripe is that I had to boot into Windows all day, but that’s because I cannot understand the geek-talk about how to install it in Linux. I’m using Ubuntu, but I barely know the basics.
So, I designed my first fin and I’m 3D printing it at the moment. Of course it’s a “Birdwing-fin”, I call this one ‘Wanderfalke’ (Peregrin Falcon).
Peregrin is designed to fit around the Universal Tough Fin Base (UTFB) I concocted, and to print on my Original Prusa i3 MK2 printer in erect orientation. So it is only 200mm high (without fin base) and 210mm from forward knuckle to aft point. A standard McCoy Gullwing fin would need about 240mm instead of 200mm height.
Anyhow, this fin was designed so I can print a hollow shell of it and then fill it with resin and insert a composite UTFB for strength and fit into the fin box. If this technique turns out to work well, then I’ll build a bigger printer if the fin really needs to be bigger.
