Does anyone use a formula to calculate an optimal grip diameter? I've heard of using the measurement of an open hand from wrist to tip of middle finger multiplied by ???

RodMaker Volume 10 #3 has all that information. A bit too much to go into here. Way too much, actually. Studies done by the military show that distance multiplied by .19 for a diameter that is optimum for use in tool or equipment handles. This will turn out to be unusually large (although still very sound) for conventional rod handles. Without going into all the detail (it's in the magazine article) try .11 for your factor.

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While I admit I have little data, I believe that the optimum size for a spinning rod grip is larger than the optimal diameter for a castring rod grip. I made two casting rods to a large diameter consistent with the guidelines and found them hard to control. They seemed to slip easily out of the hand. I altered them to reduce the diameter and found them more comfortable and easier to control. I really like the larger diameters for spinning rods and developed a retrofit for pipe type small reel seats to make them more comfortable, so it's not that I totally disagree with the guidelines. I believe the casting rod grip that tapers to the rear is the best shape for me, for bait casting. I think you need to try some different shapes and diameters.

Mike,

I, like Tom K, use the measurement times .135 for most of my handles. For someone with an 8 inch measurement from finger tip to wrist crease that would make a final handle size of 1.08 inches.

Sam

Guys this sounds like a very interesting topic. Just one problem Tom. You are not distributing RM to my country. Can someone please just give a brief description of what is involved? Or scan the article to pdf for the library?

Regarding casting grip ergonomics, no one seems to be talking about shape, and I've found that to be very important in addition to diameter. I was in a store recently looking over their high quality rods and noticed the casting grips that taper to the rear from the diameter of the reel seat to a diameter almost the same as the blank, in about 5 inches. I believe that shape is the right way to make a casting grip-it tends to put the hand into a solid contact with the grip, almost "trapping" it between the trigger and the taper. If you havn't tried that shape for casting, you may be missing something. Not sure why it took so long for me to discover it, but it shows the importance of keeping an open mind in this craft.