One cubic foot will displace about 64 pounds of water. So, you'll need about 8 cubic feet to lift it out. Don't mess around with home made lift bags to do this unless you really know your stuff. Lifting objects out of the water is very dangerous.
need help with a DIY Liftbag...
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Charlie99
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BTW, a crude indicator of whether something you want to use as a lift bag is rugged enough is to see if you can safely fill it with water while on land, while supsended from the attachment point. As best that I can tell, the force and weight distribution of water pulling down will be the same as the air pulling up when using it as a liftbag underwater.
Bob3
Contributor
A 35 gallon drum should be enough to get the snowmobile off the bottom.
I have a pile of 1500 lb bags here if ya need one.
I have a pile of 1500 lb bags here if ya need one.
Indeed, take into account the displacement of the snow mobile. I was obviously slipping on that. Are you sure it doesn't weigh a lil more than that too? That seems kinda light....
bottom_sucker
Contributor
the driver isn't still sitting on it?
munkispank
Contributor
to add to the comments from seanrollins, the fabric used can be difficult to get hold of- another option if you don't mind a bit of extra sewing is to make the liner from pond liner(available from most garden centres) and then cover it with couloured nylon (availble from most fabric stores)
the stuff is tough as mails and easy to sew.
the stuff is tough as mails and easy to sew.
Go look for a Big-Bag in a construction yard. it's the big bags they bring construction materials such as sand and gravel and they hold waight over 1.5 ton. They allready have strong straps attached to them, and personaly I used to cut the straps and make a DIY snapling hurness for clif hanging so trust me - this things are STRONG.
You can probably get it for free.
Glue sume thick PVC nylon from the inside to make it hold the air, and as mentiond, fill it with water to see it does not leak.
I suggest to use RTV/Silicon based glue for this as they are both cheap and will not "melt" the PVC/Nylon like some other glue types will do. this type of glue also tend to be flexible when the pressure will rise and the shape of the bag will change. (and it will). So don't use a glue that get's hard such as apoxy.
Now only thing you need is a air relese system to take air out when the bag go up. Best is to take one from a old BCD, so ask your local LDS for one....
If you deside to make somthing such as this yourself,
make sute you construct it properly.
make sure to use good roaps to tie whatever you want to lift to the bag.
make sure there is someone who know what he is doing.
make sure you have a way to lift the object from the surfes onto the boat....
Don't forget it takes lot's of air to fill the bag, so make sure to use big tanks such as 18L 200PSI if you don't have a dedicated tank just for the bag.
If you didn't allready done that - look for a basic course for the subject. In lot's of cases it's done during courses such as dive master together with the UW navegation.
Don't do it in blue water. make sure you have a strong anchor line to give you an extra referance when you go up.
That's about all the tip's I can remember for the last time I had to lift stuff from 30m.
You can probably get it for free.
Glue sume thick PVC nylon from the inside to make it hold the air, and as mentiond, fill it with water to see it does not leak.
I suggest to use RTV/Silicon based glue for this as they are both cheap and will not "melt" the PVC/Nylon like some other glue types will do. this type of glue also tend to be flexible when the pressure will rise and the shape of the bag will change. (and it will). So don't use a glue that get's hard such as apoxy.
Now only thing you need is a air relese system to take air out when the bag go up. Best is to take one from a old BCD, so ask your local LDS for one....
If you deside to make somthing such as this yourself,
make sute you construct it properly.
make sure to use good roaps to tie whatever you want to lift to the bag.
make sure there is someone who know what he is doing.
make sure you have a way to lift the object from the surfes onto the boat....
Don't forget it takes lot's of air to fill the bag, so make sure to use big tanks such as 18L 200PSI if you don't have a dedicated tank just for the bag.
If you didn't allready done that - look for a basic course for the subject. In lot's of cases it's done during courses such as dive master together with the UW navegation.
Don't do it in blue water. make sure you have a strong anchor line to give you an extra referance when you go up.
That's about all the tip's I can remember for the last time I had to lift stuff from 30m.
Charlie99
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The one other good tip that I've seen is that it is easier to control the lift if you have the lift bags just a few feet from the surface. Rig the lift lines, fill the bags and the item will just go up only until the lift bags get to the surface. Then you swim or tow the item to shallower water and repeat. On the second lift you probably won't need as much lift since the item won't be stuck in the mud.
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