I'm looking at this bow cap (see the three attached photos). It's a little difficult to calculate exactly what the bow angle is because it is shaped more like a "U" than a "V". The curvature of the "U" makes it difficult to determine exactly where the angle should be measured.
Here are some details:
If you draw a line from one end of the U to the other (I believe the geometric term for this is a "chord"), the chord is 9" long. In other words, the ends of the "U" are 9" apart.
If you draw a line from the center of the curve of the "U" up to the chord, and perpendicular to the chord, that line is 5" long. In other words, the inside of the "U" is about 5" tall. (However, there is a lip on the "U" which I expect is designed to wrap around the hull-to-deck joint. The lip gets in the way if you just stand it up on a table, but if you measure it like that the piece is 7" tall.)
If you do some trigonometry that suggests that a "V" inscribed in the "U" would have an angle of about 84 degrees. (84 degrees = arctan(4.5/5) * 2).
However, that's not the same as suggesting that the bow on which this would fit would be an 84 degree angle. I guess if you were to measure a point 5" aft of the bow, and found that the edge of the boat where the cap should go was about 4.5" to port and to starboard of that point 5" back, this would be the cap for you.