Buying Second hand gear...Especially PFD's

[mrcog]

In short, is it ok to buy secondhand PFD's where you don't know it's history. I come from a climbing background where it's pretty much not ok to buy used harnesses, ropes e.t.c. But in this new world of kayaking, is ok to buy a used P.F.D. or could something have happened to it to stop it from working?

[ol]

You need to check all the stitching on shoulder straps and harness points etc, that the general condition looks good, and importantly you need to assess the flotation offered by the pfd as this can reduce with age.

What flotation it states it gives for a certain bodyweight may have diminished. There is a way of doing this I believe which someone else on here will probably be able to tell you.

If you have any doubts, steer clear, not worth it.

I have had two 2nd hand BA's including my current one, I have not tested the flotation apart from actually taking a swim, but its worth doing properly.

[kernel]

As regards testing buoyancy, a 50N jacket should float a 5.5kg lead weight. Note the weight would differ for different materials, e.g. 5.7kg for iron or steel.

[mrcog]

Cheers, I'l probably buy new.

[Fatboy]

Kernel, why does the weight differ for different materials?

[frostie]

Kernel, why does the weight differ for different materials?

Different materials have different densities.

E.G. Lead has a higher density than wood, so of 2 identically shaped pieces, one made of lead and one made of wood, the lead one will be heavier due to higher density.

[Tildmeister (Mr. T)]

Different densities, maybe, but 5.5 Kilos, regardless of material is still 5.5 kilos. Only the volume of the piece will change.

[chud]

The extra mass is there to cancel out the buoyancy of the extra volume.

[naefearjustbeer]

Wood floats so I guess it doesnt matter how heavy it is it would not sink your BA.

[kernel]

Buoyancy is the upward force exerted by water on an object floating in (or submerged) in it. The force of the buoyancy is equal to the weight of water displaced by the object.

The object will only sink if it is denser than water. So you can't really test the value of a buoyancy aid by attaching it to a piece of wood and checking that it floats.

There's also a bit of mix up over mass and weight. Kilogram is a unit of mass, whereas Newton is a unit of weight, which is a force.

To find the buoyancy (force) multiply the mass of the displaced water by the force exerted due to gravity by 1kg on earth (9.8N).

So, in the above example 5.5kg x 9.8 N/kg = 53.9N.

Cheers,
Ross

[Adrian Cooper]

Probably, for the non-physicists out there, there is one small issue which has not been clearly explained. A lead weight of a given mass will be a different size to a weight of a similar mass but a different material. The wood example is a bit unfortunate. Let's say lead compared with a sack of coal. Both weights will have an element of buoyancy (uplift from water) as described above which will reduce their effective downward force. Yoy will therefore need a heavier sack of coal (out of the water) than lead since the coal will have more buoyancy.

[chicklechives]

Or use a spring balance and none of this need worry you.

[Randy Fandango]

Wood floats.....

http://www.maryrose.org/ ;-)
Giles

[Tom_Laws]

http://youtube.com/watch?v=zrzMhU_4m-g&feature=related

Compare it to a witch. Obviously.

[mpooleman]

To find the buoyancy (force) multiply the mass of the displaced water by the force exerted due to gravity by 1kg on earth (9.8N).

So, in the above example 5.5kg x 9.8 N/kg = 53.9N.

Along the right lines, but in this calculation you have not considered the density of water, unless you are assuming it is the same as the lead displacing it.

For a 50N BA, you will need 5.6Kg (so 5.5 is near enough, I know you said approx), but the calc is:

x Kg = (50/9.8)/(1-1000/11340) = 5.6Kg

(assuming density of lead is 11340 Kg/m3 from a quick google)

Feel free to disagree with me, but from a few scribbles I think I can prove it mathematically if anyone wanted to see it.

I know we only need rough estimates to test a BA, something I've actually covered in my degree is relevant!

Regards

Mark

[kernel]

Yep, that's right. Cheers.

[ol]

Wood floats so I guess it doesnt matter how heavy it is it would not sink your BA.

Ebony doesn't...........apparently, particularly when its still attached to the piano...

[minty]

From a climbing background as well. The difference with buying second hand ropes, harnesses etc is that if you need it there is likely to be a high force/load being applied because the harnesses and ropes are only for protection in a fall situation. If you don't fall climbing the harness and rope aren't really doing anything they are only for protection when needed (but if needed they really need to work). Kayaking you want the bouyancy from a pfd but I would imagine unless you are tying yourself to something by the webbing/harness in a rescue it could have a bit more wear about it as long as the bouyancy is there. I would never buy a used climbing rope or harness, in fact I would never lend out my own ropes or harness because I want to know its history.

[itsallgood]

I will only buy second hand gear that I can check the performance of myself. So, for example I would not buy a second hand helmet, just because I feel you cannot be absolutely sure that the thing is OK on a visual inspection, and I like my head.

The tests with BA's are fairly straightforward to do and understand, you can see if the webbing and other stuff is working (or in place still). The only only thing I would be weary of is the harness system, which if you are new to the sport - I would avoid for now, and get some rescue training that covers BA / harness use when you are the point where you may need a BA with harness.

I am correct in thinking that the BCU produced guidance on how to check a BA? Is it still valid?

[Twix]

I don't know, but I would think that a visual/physical check is a good start. After checking all the straps etc as mentioned before, does the foam still feel firm? Does it still fill out the fabric or does it seem loose like it has shrunk? Does the fabric look in good condition, and not faded? How old is it?

[peterH]

One other thing to note is that, after throwing your test BA + weight in the river, you need to wait for all of the air to work its way out of the fabric before you can assess the actual flotation of the BA. 90 seconds is usually enough.

[Kayak-Girl83]

As regards testing buoyancy, a 50N jacket should float a 5.5kg lead weight. Note the weight would differ for different materials, e.g. 5.7kg for iron or steel.

How many kilos would a bag of feathers need to be?

[kernel]

Loads.

[chriscw]

Second hand gear or indeed your own gear you bought new 10 years ago may have deteriorated due to age. The issue of testing buoyancy for second hand PFDs has been discussed a bit, what about other kit?

I have known a paddle with and aluminium shaft to corrode through. Some plastics deteriorate with age, and in the past old plastic boats have been known to split in colder weather.

So what you use old gear for needs to be determined by a bit of common sense. For park and play at a weir where escape from the water is not an issue and the car is nearby failure of a boat may have less severe consequences than on a multi day wilderness trip. Introducing beginners to paddling on placid water is not likely to break kit, running grade 1 and above rivers is more likely to break kit etc.

Not quite like climbing where failure of a rope 10 feet up a face may be just as fatal as failure half a mile up.

So if you are new to paddling and have not quite decided that you are going to go totally medieval with it then by all means buy or borrow older kit to learn with then get some better stuff later. You should be able to offload much of the kit you started with to someone else if you no longer need it, after all you bought it...

[mrcog]

Ok, thanks everyone. Now to raise the funds...