Best way to tie knot to rope, fixed bolt snap for dropping a tank in the water?

[SentinelAce]

I got a nylon rope. We are doing some wreck dives. I need to be able to drop my deco bottle on a rope. I have a 50' rope. How long should this be to drop off a boat? I have two fixed bolt snaps so I can just clip this on both ends. What is the best way to tie the knot to the rope?

 

[Caveeagle]

There are probably a hundred ways that would work. And depending on how you are going to rig things some might be better than others. Is this a stage/ deco tank or a single tank/BC package?

One option is to use either an overhand knot, or a figure 8 knot to create a bite. (Loop)

Then you just pull the loop through the closed end of your bolt-snap and loop it over the "G" end so that its captured and can't go anywhere once clipped to something. This makes it easy to replace the bolt-snap if the spring ever fails. *I also would tie off the loose end by the knot just so keep it all clean. Some nylon string or floss works fine for this.

A Large stainless bolt snap or boat hook would work fine, but I would plan on some redundancy if you are tossing gear over the side of deep or rough water. A caribiner with a safety catch might not be a bad idea either.

 

[lowviz]

Suggestion:

Cut it down to 30' and make an eyesplice (that will go over a cleat) on one end. Eyesplice your boltsnap (I prefer a SS ring that will accommodate a W/B) on the other end. Counting the cleat
to water distance (and length lost due to two eyesplices) you should be good.


Don't forget to haul it in as soon as you are done with it, a fouled prop can really piss off a cap...

Edit:
I originally said davit instead of cleat. Two conversations at the same time...

 

[JohnnyC]

Alpine butterfly would be the ideal knot if they will be somewhere down the line. A bowline or a figure 8 would be fine for the end. The best thing to do at the end of the rope would be to splice an eye.

Are you intending on using this to keep your deco bottles secure until you can strap them on, or is your intention to not carry any deco tanks and just leave them hanging on the line?

 

[SentinelAce]

Alpine butterfly would be the ideal knot if they will be somewhere down the line. A bowline or a figure 8 would be fine for the end. The best thing to do at the end of the rope would be to splice an eye.

Are you intending on using this to keep your deco bottles secure until you can strap them on, or is your intention to not carry any deco tanks and just leave them hanging on the line?

I'm going to drop it down, swim over and attach. So it won't be on long. Same thing for ascend

 

[lowviz]

You may find that you want some weight on that line if the boat is tied off in surface current. An 8# (two fours) weight belt makes a nice multi-purpose dead weight. That big loop is easy to hang on to if the deco area is crowded and you want some solitude. It is also a quick fix for anyone going light.

 

[JohnnyC]

Alpine butterfly (for attaching things mid-line)
How to Tie an Alpine Butterfly Knot

Bowline (for attaching things at the end of a line)
Bowline - How to tie a Bowline Knot animated and step by step illustrated

An eye splice would depend on the type of rope.

 

[Akimbo]

It depends on how sloopy the seas are and the roll characteristics of the hull. You can isolate a lot of jerking on the bottle and your decompression line if you tie a small cherry buoy between the boat and tank. It also holds your depth better if the rollers are large since go up and down with the swell. Your ears can really get hammered at a 10' stop, even with a 4' swell.

 

[lowviz]

@Akimbo, you mean this?: Cherry Bomb Buoy, is an automatic, buoy system thatthat will mark a fishing or diving position

Exactly what I was looking for! But for (er, um, aah) another purpose...

 

[Akimbo]

@Akimbo, you mean this?: Cherry Bomb Buoy, is an automatic, buoy system thatthat will mark a fishing or diving position

Exactly what I was looking for! But for (er, um, aah) another purpose...

Any small buoy with the right displacement will do fine but this is what are commonly called cherry buoys.

Red and orange are the most common (thus the name) and come in lots of sizes, from around 8" to 30"+.

Now if you are talking about a buoy for a dive flag, I prefer these. Boats stay a lot farther away: