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Here's how I made a dry bag to use up some of the leftover fabric after making my polytarp crab-claw sail. I probably should point out that I have never made one of these before, or even used one. Nevertheless, the final product seems fairly good.
This sort of bag is great to take boating or to the beach, or to put inside a non-waterproof backpack if you thought it might get wet. It keeps things dry most of the time. You could put some lunch, a towel and some warm clothes in it for winter sailing, or put your wet wetsuit in it to stop your car/bicycle trailer from rusting. It wouldn't survive immersion for long without letting water in, and a few drips could possibly get in anyway. If you need better protection for small, water-sensitive items use a plastic jar with improved gasket or a dedicated boat box.
How can a simple fabric bag with just a rope to close it be waterproof? Read on to find out.
This sort of bag is great to take boating or to the beach, or to put inside a non-waterproof backpack if you thought it might get wet. It keeps things dry most of the time. You could put some lunch, a towel and some warm clothes in it for winter sailing, or put your wet wetsuit in it to stop your car/bicycle trailer from rusting. It wouldn't survive immersion for long without letting water in, and a few drips could possibly get in anyway. If you need better protection for small, water-sensitive items use a plastic jar with improved gasket or a dedicated boat box.
How can a simple fabric bag with just a rope to close it be waterproof? Read on to find out.
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Right, you'll need some stuff.
Some fabric: I used Polyethylene tarp because i had it, but anything waterproof and fairly tough should do it.
Thread: Use polyester, heavier is better for a big bag. More expensive is often better too.
Stiffening material: On commercial bags, they often seem to use a strip of stiff plastic sewn into the hem around the opening. I couldn't find any so I guessed that some soft foam would work. What it lacks in actual stiffness it makes up for in squishness, helping create a reasonable seal.
Mouth closure: Use a webbing strap and a buckle if you want to get fancy, or some strips of non-brand-specific-velcro-like-fastener. I used a chunk of stiff cord, it works well.
Sealant: This depends on your fabric and intelligence. I'm currently trialling a silicone sealant but I don't hold out much hope. I reckon some kind of tape would work better.
- Double sided tape: I bought some stuff intended for laying carpet. It's super sticky and great for holding things in place while you sew, but not essential. I had to cut the roll widthwise with a knife as the stuff I bought was too wide.
To put this all together you need the following tools.
Sewing machine: - Sewing Machine: Someone you know has one they don't use. Older is better generally. When you find a machine spend lots of time sewing samples of your fabric with the thread you'll use. Fiddle with upper and bobbin thread tension until it works reliably. You may need to experiement with different sized meedles too. Things will be easier if you use fairly "normal" fabric, i.e. not to stiff, slippery or tough.
- Scissors: Some heavy shears and some thread nippers are a good combination, but whatever you have is fine.
- Small, sharp knife: Use this for everything.
- Measuring devices like a tape measure and ruler
- Permanent marker.
- I won't even mention an unpicker.
Some fabric: I used Polyethylene tarp because i had it, but anything waterproof and fairly tough should do it.
Thread: Use polyester, heavier is better for a big bag. More expensive is often better too.
Stiffening material: On commercial bags, they often seem to use a strip of stiff plastic sewn into the hem around the opening. I couldn't find any so I guessed that some soft foam would work. What it lacks in actual stiffness it makes up for in squishness, helping create a reasonable seal.
Mouth closure: Use a webbing strap and a buckle if you want to get fancy, or some strips of non-brand-specific-velcro-like-fastener. I used a chunk of stiff cord, it works well.
Sealant: This depends on your fabric and intelligence. I'm currently trialling a silicone sealant but I don't hold out much hope. I reckon some kind of tape would work better.
- Double sided tape: I bought some stuff intended for laying carpet. It's super sticky and great for holding things in place while you sew, but not essential. I had to cut the roll widthwise with a knife as the stuff I bought was too wide.
To put this all together you need the following tools.
Sewing machine: - Sewing Machine: Someone you know has one they don't use. Older is better generally. When you find a machine spend lots of time sewing samples of your fabric with the thread you'll use. Fiddle with upper and bobbin thread tension until it works reliably. You may need to experiement with different sized meedles too. Things will be easier if you use fairly "normal" fabric, i.e. not to stiff, slippery or tough.
- Scissors: Some heavy shears and some thread nippers are a good combination, but whatever you have is fine.
- Small, sharp knife: Use this for everything.
- Measuring devices like a tape measure and ruler
- Permanent marker.
- I won't even mention an unpicker.
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Jul 15, 2009. 7:52 PMmikeus-d-sniper
says:
cool idea. how bout putting epoxy or sealants in the seam before you sew them?
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6
Jul 15, 2009. 11:16 PM
Leon Close (author)
says:
Leon Close (author)
says:
Yeah good idea. I bet there is some sort of double-sided sticky tape that would work.
Reply
11
May 10, 2009. 11:28 PMnotjustsomeone
says:
nice instructable. If the sealent holds up it should be just as good as the "mostly"-dry-bags I bought and use. They're great for whitewater rafting by the way.
Reply
Jan 31, 2009. 2:00 AMjkm
says:
Think I spotted a Bigfoots arm in the 2nd last pic ;-) Great instructable. Can't be much less waterproof than commercially available stuff. Will mail link to girlfriend presently...
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