Daggerboards: profiles, planforms, paranoia

Originally posted by Medway Maniac

I was told "slow and steady wins the race", so our Farr 3.7 build is happily crawling along towards what I can only hope is victory (which in this case means it sails). Looking for something to do over the colder months, I have begun to approach the foils. The class rules are somewhere between brief and nonexistent when it comes to foils, so we have nearly all the freedom in the world. On boatdesign.net I read the very useful observation that any foil you build, no matter how bad, will be better than the one you don't build. Still, my paranoia (of the subject) of making a bad decision goes on.
I am looking for input and comments from people with more experience in this and I suspect this might be a good place to get just that.

The first question is that of profiles:
The consensus seems to be that the NACA 4-digit series won't be perfect, but it definitely not be bad. At the same time at least the 3.7 class seems to find that thin profiles tend to go the best. So I would suspect that a NACA 0010 or 0008 would be the best start for a first dagger board and a NACA 0012 for the rudder.
On the other hand, Frank Bethwaite (in HPS1) doesn't even consider using such a turbulent flow section, assuming that laminar flow sections are the only way to go, at least for dagger/center boards. The question here is what the leeway of a performance dinghy will be. If it remains under around 3˚, a laminar section such as a NACA 63012 (possibly scaled thinner?) would be running within it's drag 'bucket', and out performing any turbulent section. If the leeway is any larger, the section pops out of this optimum flow and should have higher drag than a good turbulent section (NACA 0008).
So ultimately the question boils down to: is it worth trying a laminar flow section, or just start with a basic, turbulent flow section and then see?

The second question is that of planforms:
Much has been written on this. I've gathered that an elliptical force distribution is ideal and that such a distribution can be quite well approximated by using a straight edged, tapered board with a taper ratio of 0.45. I have also gathered that it is a good idea to have the tip close to square at the leading edge with some rounding towards the trailing edge, to further reduce drag at the tip.
At the moment my plan is to make a board with leading and trailing edge running parallel for about a third of the length and only start the taper from there on. I would taper from both edges so as to allow the thickest part of the section to remain at a constant fraction of the board (1/3 for the NACA 00XX profiles). I intend to round the corners where the taper starts (just taking the hard edge off) as well as the bottom corner of the trailing edge (with a larger radius).

The rudder should be similar, but smaller (about a 1/3 of the area).

I am also trying to get hold of some designs for foils in the Contender and possibly Merlin Rocket for comparison purposes. People have suggested using Musto Skiff foils as a guide, but given the much higher speed the MPS achieves, I suspect that there will be some differences.
Does this sound at least somewhat reasonable or is it completely flawed? 

As mentioned above: any input or comments (positive and negative) are welcome! 

Edited by ChrisB14 - 11 Oct 14 at 7:08pm