Lead Core dive curve explanation?

Gus Pratte

Setting the stage. I'm a freshwater recreational fisherman (with limited technical background) and we use a lead core line to get the fishing lure down to where the fish are. Problem; the lead is 0.02 dia. and is incased with a woven fiber that makes a total dia. of 0.03. The weight of the lead core is 0.75 oz per 10 yrds. The lead core sinks at a rate of 7 ft. for every 10 yrds. up to 70 yrds paid out, then the rate decreases, the final value of the sinking rate is 6 ft for 100 yrds paid out at a forward constant speed of 2 mph. At 70 yrds and greater the dive curve goes asymptotic. Question: it would appear that the drag factor is uniform to 70 yrds and increases after that, is that due to the forces of water pressure at 49 ft range and greater is creating additional drag on the lead core that is greater and increasing, than the force of the weight of the lead core which is constant due to the forward speed of the boat? Question #2: knowing the dive curve for 2 mph, does the following relationship apply for different speeds; the dive curve at X speed can be predicted by the premise that the force on the lead core has the relationship of the square of the speed? Thank You Gus