Update:
Ok, I just did a little comparative work with various sharpening angles.
EU-17 Magnum: 18 degrees per side
SFNO: 21 degrees per side
HOG FSH: 24 degrees per side
Each knife was used to chop through ten 2.5 inch deck nails, each of these were about 3 mm thick. These were full power chops into the nail.
The following details what happened to each after the impacts.
EU-17 Magnum:
After some of the impacts, the only result was a blunted edge. However, where two or more impacts occured close together, the result was a rolled edge. Most of these were about half milimeter into the edge and one of them was about three quartres of a milimeter into the edge. Most of the nails ended up looking like "L"s after the impact but fa few were chopped right in two.
SFNO:
Not all of the impacts resulted in a rolled edge, most just blunted it. The edge on the SFNO proved to be more durable than on the above. The rolled over sections of steel were all about half a milimeter into the edge.
HOG FSH:
The edge on this piece was only blunted, although the thick edge impaired performance in other areas: the thick edge required more force to slice through rope, newspaper and card board. This may also be because of the thickness of the spine.
So, I am looking for a sharpening angle somewhere between 21 and 24 degrees. The nails (hopefully) are pretty close in hardness to rocks so this is a fair test to see the results of accidental hard contacts with rock. Another thing, this test was not done to find a universal sharpening angle, just which angl is best in a purpose built chopper.
I am going to try and take some pics of the knives and the nails when I get home and have access to a camera.
Comments, suggestions?
Bryan, I have only sharpened V ground knives so far. Someone with more experience can better answer that question. For a convex edge, you can use the polishing tapes (they come with 1000 and 3000 grits and they really work well).