need help with a DIY Liftbag...

[ssdiver2003]

anyone here has an idea on how to build or construct a good liftbag for next to no cost ?? THANK YOU :)

[Big-n-Buoyant]

don't risk it! gravity still takes control under God's ocean.

[Bob3]

What are you trying to lift?

[Cave Diver]

Considering the relative inexpense of a lift bag, I'm not sure why you'd want to try constructing one on your own, especially given the safety issues involved.

That being said, the first known lift bag that I recall hearing about was not much more than a pillowcase lined with a plastic bag. Doesnt get much simpler than that...

[divermasterB]

Cave Diver once bubbled...
Considering the relative inexpense of a lift bag, I'm not sure why you'd want to try constructing one on your own, especially given the safety issues involved.

That being said, the first known lift bag that I recall hearing about was not much more than a pillowcase lined with a plastic bag. Doesnt get much simpler than that...

@ $220 for a 500 lb lift bag, I would hardly call them inexpensive

[jonnythan]

divermasterB once bubbled...


@ $220 for a 500 lb lift bag, I would hardly call them inexpensive

Putting together a bag that can lift 500 lbs is no easy task. That's not exactly a trash bag with some cave line tied onto it.

Consider the techniques, gear, and thought that goes into rigging a rappel line for a *150 pound* person... and you're going to be putting a *500 pound* load onto a system? That's certainly not a trivial solution and requires some fairly serious materials and construction.

You might want to think this through some more :)

BTW, LP has 500 lb lift bags for $159 and 100 lb bags for $45.

[DA Aquamaster]

In a real pinch where I was one lift bag short of being able to make a lift, I used a large nylon mesh lobster bag with a 30 gallon plastic hefty trash bag in it for a liner. It was well made but still made me nervous as steel wire rim and handles were not made for that type of use.

That's as close as I want to get to a simple do it yourself liftbag and that was pushing it.

Sewing a small 50 or 100 lb lift bag is not overly hard assuming you can find suitable fabric. The simplest design is a bag with a lift strap made of nylon webbing that goes from the lift ring or bolt snap up over the top of the bag and back down to the lift ring so that the strap carries the weight, not the fabric of the bag. The strap is sewn to the lower rim of the bag and also to the top seam to keep it in place on the bag. The seams in the bag need to be glued and then sewn or sewn and then taped to prevent leaks. Unless you need a lot of bags it's a lot easier and not much more expensive to just to buy on at the LDS

More complex bags will use a heavy nylon strap sewn into the seams around the perimeter of a bag made of heavy fabric and these are a little beyond what can be done with the average home sewing machine.

[Tommygun53]

I wouldnt do this myself,but I have seen a guy raise a steel hulled pontoon boat with 2 55 gal drums. He strapped the drums to the deck of the boat.Then filled them with air.

I watched from the shore as he proceeded to tow this hunk-o-junk in with a cable hooked to his truck.Now what to do with it? He cut it up.Why he just didnt leave it 40ft down ill never know.It was used as a dive platform and didnt even have a motor!

But theres no way I would attempt to make a lift BAG. Have you ever felt the force that is on one?


Tom

[seanrollins]

I have to agree with the other responses about making your own heavy weight lift bag. Don't attempt it man, it's not worth the risks. However, if you want to make a 50 lb lift bag, I just constructed two for $30. One red, one yellow. Check out my webpage.

http://www.victoriascuba.com/doItYourselfFrame.htm

[Tommygun53]

Sean,
Nice Job on both the lift bag and the reel, it looks like you did your homework on both of them. You cant beat 4 bags for 25 bucks! Have you used them yet? While were on the subject of lifting, does anyone know approx how much lift one might need to raise a newer model snowmobile weighing about 500 lbs out of water?

[seanrollins]

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.

[Selvar]

seanrollins once bubbled...
..... So, you'll need about 8 cubic feet to lift it out. ......

Not really. What about the water displaced by the snowmobile? My guess is that it displaces at least 2 - 3 cubic feet of water.

[Charlie99]

seanrollins once bubbled...
I have to agree with the other responses about making your own heavy weight lift bag. Don't attempt it man, it's not worth the risks. However, if you want to make a 50 lb lift bag, I just constructed two for $30. One red, one yellow. Check out my webpage.

http://www.victoriascuba.com/doItYourselfFrame.htm 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]

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.

[seanrollins]

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]

the driver isn't still sitting on it?
:D


seanrollins once bubbled...
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....

[munkispank]

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.

[DJ69]

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.

[Charlie99]

DJ69 once bubbled...
That's about all the tip's I can remember for the last time I had to lift stuff from 30m. 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.