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Hi, I need to make a cardboard boat for a river race that will hold 3 large boys. We are only allowed to use cardboard, gaffa tape and crucially PVA glue. I think the key to a functional and original design is to make some kind of cardboard/PVA pulp and use it to line a waterproof gaffa tape exterior but not sure if this will work/if it is feasible.
Does anyone have any ideas or advice?
If you look through the subjects in this Forum, there has been a lot of discussion on making boats. Also if you check Youtube on using cardboard to make furniture, you are likely to find some useful ideas. I hope those three large boys are very good swimmers!
There's actually a book on the subject that I own.
http://www.amazon.com/Cardboard-Boat-Bo … amp;sr=8-1
I haven't built a boat yet, but wanted to own the book, so I have it when I'm ready. : )
The author also has a website ...
The design of the boat is important, so the book is helpful. He uses contact cement and paper drywall tape in his boat construction. It sounds like your assignment is taken from a similar idea. If you're using PVA glue, use the most waterproof you can, I think Titebond III is a common choice here -- you'll find it with the wood glues in Home Depot, etc.
On the website there are lots of pictures of the design successfully being used in water.
Gaffa Tape is called Duct Tape in the U.S.
It is not waterproof, just water resistant, to a point. From my experience, if you use it to tape cardboard and the cardboard gets damp or wet, the combination will come apart.
PVA is the same, not waterproof.
In fact, none of the listed materials are waterproof.
You don't mention who is sponsoring this project -- are they a responsible group, or a bunch of dunderheads?
Be sure everyone wears life vests.
I'd suggest a few simple experiments first. Find a source of strong cardboard - suppliers of large domestic electrical appliances are usually good for this. Get a couple of sheets first of all.
Cutting is easier if you have a jigsaw. A serrated knife works but can distort the cardboard. Cut a few pieces (e.g. 4, say 30cm x 30cm), paste PVA in between and weight them until dry. Test the strength. You'll probably be amazed. Decide what thickness you need for your boat panels.
Next you need a hot glue gun (usually quite cheap in craft shops). Take two similar pieces of card which you are going to join at right angles. Dribble PVA along the edge of one, leaving gaps every 10cm. Apply hot glue to the gaps, press quickly into place and leave until the PVA is set. Again, test the strength. Imagine what a laminate of four board would be like.
If you are happy with this, get a large quantity of cardboard and make up panels to use in your construction. Make box units to connect across the boat to help rigidity. There are engineering principles to take into account here.
Construct the boat. You could seal the joins with silicone sealant and then paint the whole - check out Jackie Hall's article about waterproofing. I assume that this is only to be a short term measure. Presumably you can't surround it with a skin of plastic? Of course a longer term would be to apply a skin of fibreglass but I guess this is going beyond your brief or need.
I would say don't even begin to consider pulp, it will soften the cardboard, absorb water like fury and take yonks to dry.
You could laminate the outside with strong paper - a couple of layers would be enough - provided it is VERY well waterproofed.
When you laminate carboard, lay one at right angles to the sheet underneath for maximum strength.
From the referenced cardboard boat site:
David W. Friant: "This supplement provides an explanation of the waterproof coating that I use to waterproof cardboard boats. I have 2 boats that are over 23 years old that are still used to this day due to the excellent waterproofing properties of the coatings discussed here.
Acrylic Elastomeric Roof Coating
"The recommended waterproofing material for cardboard boats is an acrylic base elastomeric roof coating. Elastomeric coatings can also be purchased with solvent bases. The acrylic base coating is the most desirable for waterproofing cardboard boats as this type of coating is environmentally-friendly. There are numerous manufacturers of acrylic elastomeric roof coatings. Elastomeric coatings can be purchased from local home improvement stores as well as purchased online.
"Due to the number of acrylic elastomeric roof coatings available on the market today, and the fact that new products are constantly being developed, I have chosen not to specify any particular manufacturer. Instead I am providing a definition of the product, the properties that make it superior for waterproofing cardboard boats, and suggestions for how to find these products.
"An acrylic base elastomeric roof coating is a â€śrubber-likeâ€ coating that provides the following benefits/properties for waterproofing cardboard boats.
Dries to a â€śrubber-likeâ€ film.
10 times the thickness of paint.
Wonâ€™t crack, peel, flake, chip or blister.
Long term exterior waterproof protection.
Fungus and mildew resistant.
Excellent UV protection.
Easy to use, non-toxic, and low VOC content.
Superior adhesion to cardboard.
Bridges hairline cracks."