Every year in Penryn, Cornwall there is a raft race organised jointly between the Student Union and the Town Council. The brief is to build a raft out of reused materials that will float at least 3 people and race it to a buoy in the harbour and back to shore. It's such a fun day, and if you like making stuff and getting wet (spoiler) and feeling like you're part of the community, it's exactly the sort of event for you.

This year, to promote our business (packaging reuse website packshare.org) we thought we'd enter a raft made entirely out of local businesses' mail-order packaging. The original theory was that we'd get it in the water, it would sink and we could run a campaign about it being a lousy way to reuse packaging, but honestly we're kind of competitive people and the raft turned out awesome.

Here's how we did it:

Supplies

1 Pallet
5 cardboard bike boxes
Other cardboard boxes for capping (we used about 8 x a4 paper boxes)
Reused bubblewrap
Approx 200m of gaffer tape

Step 1: The Hulls

I think that any good packaging raft starts with a pallet. We were really lucky that we found a huge, lightweight one behind a local businesses's bins and they said we could have it. In my experience, pallets are generally useless to most businesses once their deliveries have arrived, so they are happy for people to take them.

The cardboard we got was 5 old bike boxes from a bike shop. We folded 4 of them into triangular prisms and cut the 5th up to make strengthening supports inside.

Because the cardboard overlapped we made sure to gaffer tape the edges to increase the strength.

The support struts were folded sheets of cardboard running from the bottom point of the hull and taped into the middle of the opposite side. Shaped a bit like the Deathly Hallows from Harry Potter.

We made four of these open ended hulls and checked that they took the pallet's weight.

Step 2: Waterproofing the Hulls

So now we had 4 open ended hulls, and the shape of the raft was pretty clear. I sent a picture of it to my brother and he nicknamed it The Cantamaran, which I guess was fair at this point.

So our next step was to make those hulls watertight.

First we capped them with the printer paper boxes, but really any firm cardboard would have done it. This made them much stronger and less resistant to losing their shape.

*In retrospect, by this point I think we'd already made our fatal mistake by not fully testing the amount of weight the hulls could take. In fact I sat on one end up and it held brilliantly, but really we should have spent more time reinforcing inside each hull.

We had managed to source loads of scraps of old bubblewrap from various businesses around Falmouth, and we waterproofed the hulls by entirely covering them with bubblewrap.

This used a lot of gaffer tape, but by the end I was satisfied that each individual hull would float, and no cardboard would get wet.

Step 3: The Deck

The plan was to race with 4 of us in rows of two. The logic was that we'd each have weight on one hull.

We reinforced our sitting positions with more bubblewrap and cardboard for comfort and so we weren't actually sitting on the hulls.

I don't have a picture of exactly what we did, but this shows us doing some research into how comfortable it was.

As it was a racing raft, we didn't worry about a proper deck, just suspended seats. It made it feel like it should be faster somehow.

Step 4: Assembly and Launch

We had to transport it in pieces to the race, so we couldn't assemble it until we arrived which was quite stressful.

But once it all arrived we gaffer taped the hulls to the deck and hey presto.

The rest of the crew made a Packshare flag and we drilled a hole to mount the very wobbly flagpole.

There was a lot of breath-holding as we launched it, followed by utter hysteria as it floated better than we'd imagined.

We even worried that it was floating so well that we wouldn't be able to reach the water with our paddles...

Step 5: The Race

So really that's the end of the Instructable.

The raft floated really well for a while. The race was out around a buoy about 300 meters out, and was divided into heats. We actually won our heat, but as soon as we sat on it I think the cardboard hulls couldn't hold our combined weight, and as they changed shape it created holes in the gaffer tape seams which started bubbling underwater.

By the end of the final we were - as shown - waist deep and moving very slowly.

For more photos and more story I wrote a whole blog over at https://packshareapp.wixsite.com/blog

I'm convinced that the general idea of the raft was good, but doing it again I would massively reinforce the hulls inside, either with folded cardboard struts or just pack them full of bubblewrap. Next year we're intending to enter a boat that is entirely bubblewrap which I will share on here

Final Note: yes we are all dressed as Power Rangers. I can't really explain why but it did seem to make us go faster.