Jon lines

[Braunbehrens]

Regarding current and cold. Boil 3 eggs. Put them in a bowl under the cold water tap. Fill the bowl with cold water. Wait 1 minute and take the eggs out.

Now do the same, but let the water run the whole time.

Which eggs do you think will be warmer?

Cold was brought up as a reason FOR using a jon line. I'm just saying that if anything, you'll be colder hanging on the line than drifting in the same water.

Now hopefully you are well insulated and it's not that big a deal, but you certainly will be cooler hanging than drifting. How much cooler, I don't know, but I'd be happy to study the matter if you'd all be so kind as to pay for my research ;-)

Bridge, you really think that wearing a windbreaker you will not feel windchill at all? Most of the heat is lost through the head, which usually is in a wet hood. Current increases water circulation in the hood and over the face.

I can't believe you guys would argue something that is a) so obvious and b) such a minor point in the whole jon line thing.

If you really wanted to argue it just say that whatever the conditions are on the jon line you'll be prepared for it with proper exposure protection. Period end of story. Just don't tell me that cold is a reason why it's better to hang on to a jon line.

O-ring, your question is pretty complicated. How many chase boats, how many teams, how far from shore etc.?

I do most of my diving off a small anchored boat with no one on board, and we come up the anchor. However, I don't dive far enough from shore so that swimming back would be a real problem.

Whenever possible we live boat.

If I feel that the current will be a problem then I won't do a dive requiring real deco.

(as opposed to fake deco, which everyone knows means doing just a few 1 mn stops on the way up ;-)

 

[Scubaroo]

Braunbehrens once bubbled...
If I really wanted to do it I might take a waterproof GPS, a waterproof VHS and an EPIRB, stuff them in a watertight tube and carry them as a stage....

Hey O-ring! Still got that AUL canister handy?

You could probably stuff a bottle of Aquafina and some Clif bars in there as well

 

[Charlie99]

Braunbehrens once bubbled...
Regarding current and cold. Boil 3 eggs. Put them in a bowl under the cold water tap. Fill the bowl with cold water. Wait 1 minute and take the eggs out.

Now do the same, but let the water run the whole time.

Which eggs do you think will be warmer?

Now do the experiment that more closely matches the drysuit dive:
boil 3 eggs, put them in a THERMOS BOTTLE, then run your experiment.

The outside of the drysuit is at the water temperature whether or not there is current.

Charlie

 

[MikeFerrara]

Paul is right about heat transfer. Divers loose most heat through convection and conduction. Water can't pass through a dry suit but heat can. Every one knows that scootering is colder than swimming. If you don't believe me as the OCDA guys. They're doing long scooter dives in cold caves.

Next subject...

I haven't done a lot of wreck diving in strong current. Most of our Great Lakes dives have little or no current though that isn't true everywhere in the Lakes.

I can see the advantage to drifting deco. Simple enough you're not being battered by the current. My question is if you are going to drift is a bag the best way to do it or would you be better off with a drifting decompression station that you cut loose when you start deco. Isn't there a concern of the boat loosing track of a little bag in rough seas especially if there are multiple teams?

 

[O-ring]

Scubaroo once bubbled...
Hey O-ring! Still got that AUL canister handy?

You could probably stuff a bottle of Aquafina and some Clif bars in there as well

Yeah, that would make a handy waterproof, emergency kit... Can't do that right now...it is serving as primary light since my Halcyon was defective..

 

[Pez de Diablo]

Mike,

I agree that you lose heat through convection and conduction, but I would think that the difference in the situation described would be negligible and would not weigh heavy when planning the dive.

Maybe the guys doing the long scootering are colder because they are not as active

 

[runvus4]

filtered once bubbled...
Can someone explain how to use the spool as a jon line?

Basicly you:
1) Achieve neutral bouyency
2) Loop the spool or reel around the ascent line
2a) Tie off the spool or reel around the ascent line
3) Roll out to the distance you want to stand off the line
4) Clip the double ender on the spool so that the line won't unspooll any further or screw down the reel so it won't unreel anymore
5) Hold onto the spool/reel
5a) Use the other end of the double ender and clip it off.

The a) options are IMHO less desirable as they make a connection that is harder to release, but can have their uses, and it's always nice to have both hands free.

IMHO, being clipped off and having the water pass over you WILL be colder than drifting. The difference however should be unnoticable/negligable in term of comfort or hypothermia risk if you were using proper exposure protection.

Braunbehrens is expressing his opinion, not a statement of fact. In some ways I agree with him, but in practice that would make many wreck diving sites undivable. I personally think that the increased risk of a "Jon line" used by capable divers when is the line is not hard attached is negligable compared to other common "local practice" dive activities, such as cave diving, ice diving, wreck penetration, deco diving, etc. As he said, it's all about personal tolerance and assumption of risk for the diving youare doing, and for me, that means that Jon lines are acceptable when properly used.

 

[Braunbehrens]

Charlie99 once bubbled...
Now do the experiment that more closely matches the drysuit dive:
boil 3 eggs, put them in a THERMOS BOTTLE

Charlie, I want the name of your suit! I freeze my @$$ off even with thinsulate. Thermos? I wish.

;-)

 

[Braunbehrens]

Ok, so you're doing this wreck dive with deco etc., and you're hanging on the anchor line with your jon line. Let's say that there are 4 teams at different depths.

What do you do if 2 teams don't make it or get blown off?

What do you do if the boat has to leave, and puts a float on the anchor? Typically this will lower the anchor line quite a bit, possibly causing people at the 70 and 20 ft stops to tox?

It just seems like a lot of stuff could go wrong!

BTW, I really think the cold issue is totally minor. I'd much rather explore the risks of jon lines an what you guys do to minimize them.

 

[bridgediver]

Braunbehrens once bubbled...
Regarding current and cold. Boil 3 eggs. Put them in a bowl under the cold water tap. Fill the bowl with cold water. Wait 1 minute and take the eggs out.

Now do the same, but let the water run the whole time.

Which eggs do you think will be warmer?

The eggs that you ran the water over will be colder because they aren't insulated. Not them same situation as a diver in a suit.

Braunbehrens once bubbled...
Bridge, you really think that wearing a windbreaker you will not feel windchill at all? Most of the heat is lost through the head, which usually is in a wet hood. Current increases water circulation in the hood and over the face.

[/B]

No, I would not say that. But if the person had a complete wind barrier, e.g. hood, pants, mitts, mask etc. then I would. You are correct that most of a person's heat is lost through the head. Windchill causes problems to exposed skin or areas of clothing that wind is able to penetrate. So, in the case of a diver with his mouth exposed I suppose that it could make you colder but insignificantly so from a physiological stand point. I would consider a wet hood to still be a good insulator though because water doesn't circulate inside of it - so you effectively still have a barrier and an insulator (admitably not as good as a dry suit).

Braunbehrens once bubbled...
I can't believe you guys would argue something that is a) so obvious and b) such a minor point in the whole jon line thing.

Just don't tell me that cold is a reason why it's better to hang on to a jon line.

[/B]

I agree that it is a minor point, just joining in the discussion (I think that you brought it up though?). I confess that I don't know squat about jonlines but I do know LOTS about windchill having spent a fair amount of time in the northern latitudes so I'm only speaking about what I know... didn't mean to detract from the intent of the thread. I think cold is cold. Whether you're drifting or hanging it won't make any difference.

friends?