To get the accurate shape that you can replicate at will, you have to make a mold. Once you have a plug that is the foil shape and thickness you want, you laminate it on a very flat surface large enough so there is extra room on all sides so that you can vacuum bag. I used 1/4 inch thick plate glass glued with the 3M boat glue on to a very flat and true frame made out of 3/4 X 2 inch hardwood.

Next, take a piece of plywood and cut the foil planform shape out of it, leaving about 1/4 inch extra space all around the foil so the plywood will lay flat on top of the layup. If it is too close to the foil shape, the plywood cannot get down to the glass, and you will have to start over. Make sure that the foil plug is waxed good, and has mold release on it, and then lay up 6 to 10 layers of fiberglass cloth on top of the rudder plug, and then put the plywood over the whole affair and vac bag it. You will get a very nice mold that you will be able to duplicate foils from over and over. I did not fill in the back of my rudder mold with anything, but if you use foam, then you can vac bag to some other surface other than the mold. My mold wound up warping a bit, so I had to clamp it down to a flat surface anyway, but I had left about 2 inches around the mold as a vac bagging flange. I would recommend 4 inches actually. If you e-mail Phil at Phils foils, he will make you a mold out of whatever material you specify that is accurate to the coordinates that you chose the whole way down the legnth of the foil for very little money. I think that is what I would do now.

I used foam core for my rudders. Once you have the mold, you will be able to use foam that is shaped close to the correct foil shape to use as a core. It will bend to fit. Some people recommend cedar core for the top half of the foil core... I found it heavy and akward to fit in place. I just used more layers of uni carbon to stiffen it.

I found out that if you try to lay up lots of layers of uni carbon on top of a perfect shaped foam blank, you get a thick foil. That is when I decided to make my blanks with cedar, and one 3 oz layer of glass. Then the mold was a lot closer to correct. Plus you need to use an extra layer of uni near the top of the foil so that it braces the area where the foil goes through the hulls, or just under the rudder bracket, so that would leave a hump under the top layer of the layup. I guess you can use another full layer of uni the whole legnth, but that is not needed for stregnth, and it iwll add extra thickness if you are laminating on top of a blank that is already at proper thickness...

The last few foils I made, I laid up the carbon first, and then glued in the foam once the carbon was cured. Plus I used more layers, I think 3 layers of 9 oz uni carbon, 1 of 5.7 oz kevlar on the inside, and 1 of carbon cloth covering the whole deal. Plus I added another layer of uni that extended down to about 6 inches below the hull or the rudder housing. For my daggerboards, I used 4 full layers of uni.

This Eppler 184 shape has been made symetrical. I did not check out the drag charachteristics. It may be junk for all I know, but seems to work okay. These coordinates are for the rudder thickness... 9.14% thick. I used 8.32 on the daggerboards. The rudders have only stalled on me once in real light air when I had the daggerboards too far forward.

Table
x y
0 1 0
1 0.99683 0.000115494
2 0.98765 0.000573575
3 0.97313 0.001439918
4 0.95362 0.002625577
5 0.92911 0.004159835
6 0.89973 0.006194461
7 0.86584 0.008779829
8 0.82782 0.01189228
9 0.78612 0.015479569
10 0.74122 0.01948562
11 0.69362 0.023805694
12 0.64387 0.02831204
13 0.59253 0.032792143
14 0.5402 0.036928659
15 0.48747 0.040461195
16 0.43492 0.043184139
17 0.38317 0.044960773
18 0.3328 0.04571328
19 0.28437 0.045484214
20 0.23841 0.044402896
21 0.19544 0.042516787
22 0.1559 0.039869581
23 0.1202 0.036447137
24 0.08869 0.032327963
25 0.06166 0.027555898
26 0.03935 0.022198573
27 0.02188 0.016351074
28 0.00938 0.01020189
29 0.00189 0.003696
30 0.0001 0.0005005

When I was deciding, I made a few copies of the different foil shapes one on top of the other for comparison. If you do that, make it fairly long so that you can compare better. I made mine 10 inches long, but would make them longer next time.... like 20 inches. It is easier to get a better idea of shapes if they are larger.

One thing to consider is that thick foils ventilate sooner than thin ones. There was an artical in Tank Talk on a 505 website that recommended a 12 % thick foil.... Other stuff recommends a thinner foil, like 10%. I figure that with the elongated tail on the Eppler, the front part of the foil is very close to a NACA 64010 with the elongation added. Check it out for yourself.