Cave Line for Diver Alert Marker Deployment. Less than Ideal?

[cbrich]

But failing that, I'd still like to have the option of shooting the bag and tying off to the wreck and I'd regard #24 as the minimum line weight. You've cited a 250 pound breaking strength, but 230 is a more common figure and I've seen #24 rated as low as 170 pounds. Worse that will be reduced by age and by knots in the line. So with a 100 pound SMB in a strong current and a diver or two hanging off that like a kite, #24 may not be adequate. #36 gives you another 100 or so pounds of tensile strength and is not a bad idea, but going lighter than #24 is a sure fire way to find your self on the wrong end of a broken line. The handling qualities also start to suffer with smaller diameter line and you really do not want to have an entanglement issue as you bag is launched.

I understand the concern. However, an important phrase comes to mind "Anyone can abort a dive for Any reason."

I am not even going to get into a argument with you on the line test strength. Because I too have seen #24 line rated all over the place, just like you said. That is why my spools are filled with Dacron line that DGE sells, and my reels are filled with #36. This is how I was taught, and I will not change from that.

My training and your training are completely different. You mention hanging on the line with 2 divers, I guess that is how you were trained. I was taught to never "hang" on a down line, only to use it as a visual reference. The worse current I have been in was 2-3 knots, and we ended up aborting the dive; again to each his own, that was horrible dive for me.

With regards to the handling qualities of the smaller line, I completely agree you. I personally would never go too anything smaller than a #24, on my spools or reels, but I was just answer the OP's questions, that is all. This is an internet forum, the OP needs to take responsibility for his own decisions. He should also be following what his instructor taught him. If I have a question, I will send my instructor an email with it, not go post it on an internet forum.

When I do a 200' dive, do I leave my reel behind, HELL NO. Just because I have not needed to deploy a bag from depth, does not mean I never will. When that time comes, I will make that decision on when to do it (or my buddy/team will make that decision.)

 

[rakpix]

But failing that, I'd still like to have the option of shooting the bag and tying off to the wreck and I'd regard #24 as the minimum line weight. You've cited a 250 pound breaking strength, but 230 is a more common figure and I've seen #24 rated as low as 170 pounds. Worse that will be reduced by age and by knots in the line. So with a 100 pound SMB in a strong current and a diver or two hanging off that like a kite, #24 may not be adequate. #36 gives you another 100 or so pounds of tensile strength and is not a bad idea, but going lighter than #24 is a sure fire way to find your self on the wrong end of a broken line. The handling qualities also start to suffer with smaller diameter line and you really do not want to have an entanglement issue as you bag is launched.

so this gets to the root of my question. first off ... wow ... i thought my 52 pound marker was huge. second, if the lift bag can only apply 100 pounds of buoyant force then a line would only need to have 100 pounds test (after accounting for knots.) no matter how many divers hang on that line, there will be no more than 100 pounds of force acting on the line. if you were to put ten divers on the line, each applying ten pounds of force downwards on the line then the bag will remain at the surface by applying 100 pounds of force upwards on the line. the line has a tension of 100 pounds. if you were to add an eleventh diver to the line - applying another 10 pounds downward - the line will maintain 100 pounds of tension and will drag the marker underwater. the line strength never needs to exceed the buoyant force of the marker. so in my case, why would i need 230 pound test line?

 

[ajduplessis]

I replaced the 24#nylon on my 150ft spool with 220ft of orange Dacron.

 

[Stoo]

I use the "fluorescent" orange line and find it shows very well. Regarding the breaking line due to current, I would think that if there is that much force on the line, it will just drag the diver up, rather than break. I suppose that alone is reason to take a lot more line than you expect to use...