How to make cardboard water-proof?
 

So I was thinking of making a front air dam out of coroplast, but I'm afraid I might not have enough.

How could you make a cardboard mod water-proof? I'm sure there are several ways.

The way you make it waterproof is to buy coroplast instead.

You can make it damp proof by spraying the right paint on it (or oil) but the cost of the paint likely exceeds the cost of coroplast and also water can still seep in through the sides of ruin it anyway.

Cheers
Ryan

exactly what i was going to say

Sorry I don't have a definitive answer right now, but recently a cardboard bicycle was in the news and it is waterproofed- if anyone can find out what that process is.

And a while back I posted about a cardboard and plywood car students built- perhaps there is info online about that somewhere. http://ecomodder.com/forum/showthrea...ign-22627.html

Google "waterproofing cardboard"- there's plenty of hits, including this: http://ecomodder.com/forum/showthrea...oard-4455.html

Also I wonder how well cardboard holds up if it's soaked with polyester or epoxy resin as commonly used in fiberglass projects.

Not all cardboard is created equal.
 

I use cardboard for rapid and low cost "prototyping". Once the shape and configuration are ironed out, a "one off" using the cardboard, polyester resin with monomer thinner and some fiberglass can result in an effective and durable part.

However, the paper the cardboard is made of comes in a variety of wood pulp, clay fillers and wax additives for processing and gloss. Cardboard that has little clay and no wax makes the best core for polyester layup as it readily absorbs the thinned resin. A quick and ready test is to wet the cardboard. If it becomes soggy and limp in a minute or two then you have the low clay, low wax paper that is desirable.

There was a fellow up Jack McCornacks way who built aircraft using cardboard as the base material. I bought one of his books and it is buried in my library somewhere. But, the main thing I remember well is the choice of cardboard.

I built a cardboard canoe that held over 500 lbs (3 heavy people). Did not take any water. Was in the water with us 3 for a 1/2 hour. And in the water longer with just 2 people. The paddles were also cardboard and duct tape. I am also making a front bumper prototype out of cardboard and duct tape.
I will post a diy w/ pics after completion/testing.

I used duct tape to seal my boat.
Other things that would work: Shrink wrap, marine vinyl, clear packing tape, epoxy, poly
+1 for duct tape. 2 layers for front, 1 layer in back.

note: if using epoxy or poly you need to make sure the object is resistant to deformation.

I was going to suggest using a product like "Thompsons Water Seal "

The sides of the cardboard would then have to be sealed shut. This could be done in one of several ways - clear packaging tape, duct tape, a thick coat of paint that gets into the crevices ...etc etc .

The idea of using cardboard seems ridiculous at first, but i must admit that cardboard is a readily available source of cheap material that is more flexible than Coroplast.

Coroplast isn't good for compound curves, but thin cardboard can be shaped into just about any shape.

One drawback : Cardboard is heavier than Coroplast and will become even heavier with a few layers of water seal.

It's an interesting idea none-the-less.
I would like to see how it turns out !

your in Nor CAL....are you near sacramento?
I bought 4ft x 8ft sheets wholesale at a place near arco arena.

When i'm not obsessing over my 93 Festiva or attempting to upgrade my employment status to something resembling 'Stable', I build homemade guitars and Ukuleles out of cigar boxes, tennis rackets, cookie tins etc (teaching myself to PLAY them is another matter entirely as my neighbors and their pets can attest... :rolleyes: ) Of course these instruments are of rather..unique measurements and don't fit into any standard case or gig bag.

The solution? My local music store throws away the shipping boxes whenever the new stock comes in, and with permission I nick a few. After using a razor blade and stapler to chop down or expand the box to fit its instrument, a thin layer of polyester resin (left over from last year's bodywork on the Festiva) seals and hardens the cardboard. Thin strips of bent cardstock can be epoxied into reinforcing ribs if needed for almost no extra weight-then the outside is covered in thin cloth (usually some leftover worn out T-shirts or a former summer curtain) and wetted. One the top and bottom are finished, holes are drilled for two surplus belts-the buckles for fasteners and the rest for leather hinges-the results are plain but functional, lightweight and strong.

Last month I was asked to make and ship a cookie-tin Tenor banjo cross-country, so after making a case for it using the techniques listed above, I glued in the foam I wanted for travel-then filled the box with 10 lbs of old cans and taped an egg in each corner. I then proceeded to climb to the top of my barn and toss the package 30 feet to the asphalt road below.

Result? Minor scuff on the case, three unbroken eggs. I packed the banjo and mailed it with complete confidence, and had an omelet for lunch. :D

If I can ever get this property sold and move out to the coast, i'm considering prototyping a boat out this stuff-with more layers and greater thicknesses of course...