Pitlamp
Well-known member
Fulk raises a very good point about understanding the physics of floatation / swimming. I reckon it all boils down to whether you - and each item of your gear - is negatively buoyant or positively buoyant. Whether you actually sink or float is the overall effect of the the bouyancies of everything combined.
Two main forces act on a floating object; weight (a downwards force) and upthrust (an upwards force). If the upthrust is greater than the weight, you float. If the reverse is the case, you sink. Anything negatively buoyant attached to you contributes to weight in the water and everything positively buoyant in the water contributes to the upthrust stopping you sinking.
It follows that blaming a single item (e.g. wellies) is unhelpful - a better approach is to try to minimise the number of negatively buoyant items and increase the number of positively buoyant items, such that the overall effect is that upthrust beats weight. If the nature of the trip dictates that items of gear attached whilst you're swimming results in weight being greater than upthrust then you have two choices:
1. Don't do the swim.
2. Wear a buoyancy aid to uncrease the upthrust, thus counteracting the weight.
It's worth aiming for overkill on upthrust because it's not just a case of sink or float - it's a case of how far your mouth and nose are out of the water (the greater the buoyancy the higher you'll float in the water). So my advice would be - unless you've previously tested a particular combination of kit in safe water - WEAR A FLOATATION DEVICE.
You can, of course, contribute to upthrust by making swimming movements - but this is tiring and if you become very fatigued (which can happen alarmingly fast in the wrong circumstances) then the default is that you sink, sooner or later - which is never a good outcome.
Just to answer a point Dunc raised above in a bit more detail - If you go to Leck Beck Head you'll find a large depression in the valley just behind the flood risings. This is probably a large truncated entrance, now filled with vast volumes of boulder clay, from when the Ease Gill river resurged at a higher level (probably before the last glaciation). This drops straight into the present day active flow. I used the term "drops in" deliberately because the resulting hanging choke regularly collapses in massively, hence the arrival of many new boulders all of a sudden. It was this enormous hanging choke which defeated us in the underwater section of Leck Beck Head and I reckon this could, at least in part, explain why the water level rose so alarmingly fast in Lancaster at the weekend.
Just as a matter of interest, exactly the same situation exists at Brants Gill Head on Penyghent, where a similarly large shakehole connects via a choke with the submerged passage not far in from the dive base. So take care in wet weather if you're ever in the lower parts of Penyghent Pot!
Two main forces act on a floating object; weight (a downwards force) and upthrust (an upwards force). If the upthrust is greater than the weight, you float. If the reverse is the case, you sink. Anything negatively buoyant attached to you contributes to weight in the water and everything positively buoyant in the water contributes to the upthrust stopping you sinking.
It follows that blaming a single item (e.g. wellies) is unhelpful - a better approach is to try to minimise the number of negatively buoyant items and increase the number of positively buoyant items, such that the overall effect is that upthrust beats weight. If the nature of the trip dictates that items of gear attached whilst you're swimming results in weight being greater than upthrust then you have two choices:
1. Don't do the swim.
2. Wear a buoyancy aid to uncrease the upthrust, thus counteracting the weight.
It's worth aiming for overkill on upthrust because it's not just a case of sink or float - it's a case of how far your mouth and nose are out of the water (the greater the buoyancy the higher you'll float in the water). So my advice would be - unless you've previously tested a particular combination of kit in safe water - WEAR A FLOATATION DEVICE.
You can, of course, contribute to upthrust by making swimming movements - but this is tiring and if you become very fatigued (which can happen alarmingly fast in the wrong circumstances) then the default is that you sink, sooner or later - which is never a good outcome.
Just to answer a point Dunc raised above in a bit more detail - If you go to Leck Beck Head you'll find a large depression in the valley just behind the flood risings. This is probably a large truncated entrance, now filled with vast volumes of boulder clay, from when the Ease Gill river resurged at a higher level (probably before the last glaciation). This drops straight into the present day active flow. I used the term "drops in" deliberately because the resulting hanging choke regularly collapses in massively, hence the arrival of many new boulders all of a sudden. It was this enormous hanging choke which defeated us in the underwater section of Leck Beck Head and I reckon this could, at least in part, explain why the water level rose so alarmingly fast in Lancaster at the weekend.
Just as a matter of interest, exactly the same situation exists at Brants Gill Head on Penyghent, where a similarly large shakehole connects via a choke with the submerged passage not far in from the dive base. So take care in wet weather if you're ever in the lower parts of Penyghent Pot!