Since one adjusts the depth of a bottom bouncer by adjusting the line length so that it makes occasional actual bottom contact, using a trolling depth curve is not necessary, but based on study of trolling angles there is a small nugget of information that we can impart.
Advice found on the internet and fishing magazines and other places says that when using a bottom bouncer for example when trolling for walleyes, it’s best to use a boat speed and weight size that gives a 45-degree line angle. We don’t know whether 45 is ever meant to be precise or is the best angle for every different type of bottom bouncer rig. Some of these articles may be using the term 45 degrees generically just to mean an angle somewhat halfway between vertical and horizontal. However, the following concept is the same regardless of the desired angle.
A trolled line, even with a bouncer, is not straight but is curved. When fully deployed, the line angle at the rig’s end is greater, usually significantly greater, than the line angle at the boat.
If the desire is to keep a 45-degree angle at the bottom bouncer’s attachment point, check the angle at the point you first start lowering the rig into the water. Adjust the boat speed or weight to make this angle about 45 degrees. As you let out more line, the boat-side angle will decrease, while the rig-side angle remains at 45 degrees. You should adjust the line length to feel and maintain occasional but not constant bottom contact. Don’t let out too much line, or the bouncer may fall over. Keep boat speed constant, and still know that the angle at the rig is 45 degrees even though the angle of entry is now less.
As the water depth changes, simply adjust your line length. You do not need to adjust your boat speed to maintain 45 degrees at the water surface. As long as the boat speed is the same, your rig will always see the same line angle that was evident when the rig was near the surface.
Probably, many trollers who attempt to use a 45-degree angle have a much steeper angle at the rig than they realize. Which is fine, if they catch fish. The point is that adjusting boat speed just to maintain the angle at the boat is pointless.
