On Sept 20th, Lee wrote - "I was told that (the distance of the rod above the water does affect the diving depth of a crankbait) but I'm not sure it's true."
Mark replies - Lee, The answer to your question is yes and no. It depends on how a person is trolling and with what accessory items. For example, if you’re trolling with a mast system that attaches a large planer board and tether line to a planer board mast, the lines closest to the boat are positioned several feet off the water surface. This indeed reduces the diving depth of the trailing crankbaits. I compensate by adding about 10% to 20% to the trolling lead in this situation.
If you were fishing an in-line planer board like the Off Shore Tackle Side-Planer, the board and line are at the water level and the diving depth of the crankbait is not impacted even if the rods tips are positioned straight up in the air.
For flat line trolling situations, the higher the rod is positioned off the water, the shallower the bait will run. This ratio is about 1 to 1 or in other words if you raise the rod tip one foot, you are reducing the diving depth of the lure about the same. For flat line fishing, I recommend positioning your rod tips just a couple inches above the water.
Great question Lee, I hope my answer helps you catch a few more fish. Thanks for writing.