Raft / Art Project by Novice!

[sarawales]

Hi there.
I'm new to the forum and new to raft-building. I'm an artist based in Wales, UK, and I'm making a raft as an artwork for an exhibition in 5 weeks. Yikes!The piece is about climate change and is made from recycled materials (or as much as is possible)
The raft is planned to be 3metres wide by 6 metres long. I don't know what to make it out of so that it's flotation is strong enough to support everything that will be on it, which is the following:
A cabin made from a 3x2inch timber frame, walled with plywood, and roofed with corrugated steel and plastic. Its dimensions are 180cm x 180cm x 140 height rising to 210cm at the front. Inside it will be a bed, table, chair, shelves, cooker etc.
On the front of the raft will be a large pile of plastic, and on the back a bench and a 'garden' made from los of plastic flowers (I know - it sounds a bit wierd, it's art . Occassionally a person may have to go on it.
I would really appreciate any advice about how i should make the raft. I have done some internet research and understand that there are several possibilities but I need to know it's a sure thing because when it get's put in the water it has to float first time, and stay afloat for 30 days. It will be lifted and lowered into the water by a hoist so it also needs to be strong anough to withstand that. What design should it be? What materials should I use? Please help! Sara, Wales

[grob]

If it only has to float, and not be sailed, then you are really just looking at a method of providing floatation from recycled materials, the first thing you need to do is to estimate how much weight it needs to carry. i.e. weight of the people, furniture etc, when you have figured that out you will have an idea of the volume of floatation material you will need. i.e a 1000kg payload will need 1000 litres of floatation,

Then you want to add a safetly factor say 2 so maybe 1000kg payload will want 2000 litres of floatation. Try and pack the floatation into the four conrners for stability.

Gareth

[Tim B]

ummm... yes... 3metres beam by 6 metres length is about the size of a sailing Catamaran, but you sound like you'll be carrying quite a bit more weight.

When you say recyclable do you mean plastics (polythene?, ABS etc.) or bio-degrable materials (ie. wood), or materials that can be re-forged (ie. metals). You tend to find that an awful lot of materials are recyclable. You're really only cutting out some fibre reinforced plastics.

Have a look at big plastic pipes, as they are easy to work, and when sealed at each end become totally water-tight. then build the cross-beams(you'll probably need 4) and some longitudinals (about 4) to give you something to nail the deck to. Once that is done, you can carry on from there.

The secret to keeping it floating is to make sure EVERYTHING that is in the water is sealed. I assume that it will be floating in fresh water, so you can use 1 m^3 Water = 1 Tonne. It is normal practice to ensure some free-board (ie. make sure the deck is above the water), so you'll want to use pontoons (to give them thier correct name) that provide sufficient bouyancy when not totally immersed.

On the point of global warming and sea-level rise, the worrying thing isn't raw materials, it's close-quaters propulsion, for which we've all become so dependant on engines. If you think about it, a wooden yacht is not carrying anything (except fuel) that is "non-renewable", or non-recyclable. And how about running the engine in that yacht on rape-seed oil? How hard would that be?

Tim B.

[RAWRF]

What on earth are you talking about? This is a boat design forum, I am not a snob by any stretch, but this is the wrong forum. I don't think there is a floating junk platform forum, but if there is you may find better advice there. what you are talking about is a big floating parade junker, maybe a Mardi Gras float expert is more what you are looking for.

[Tim B]

RAWRF,

I think it's a reasonably legitimate question. Ok, it's for an art project, not a fishing platform (say), but the principles involved are the same.

I don't see a problem,

Tim B.

[sarawales]

Thank you guys for your help, I really appreciate it.

[SamSam]

Try here for ideas and links... Sam
http://www.floatingneutrinos.com/

[Poida]

Sara

You don't have to put 2 of every kind of animal on it do you?
I think it needs to float for 40 days.

[djwkd]

Originally Posted by Tim B

use 1 m^3 Water = 1 Tonne.

Tim B.

isnt it 1 mtre cubed =1 tonne?

[Rusty Bucket]

Hi, TRy building a wooden frame 3 meters by 6 meters , put some used plastic drums under it for flotation and a used plywood deck to stand on. I think you've got the rest figured out. Bon Voyage, rusty

[djwkd]

Yh,rusty has a good plan.but when i started to build my raft (haven't finished yet)i was going to use 55 gal drums,something like that but they were about Twenty pounds sterling!so i decided to use plastic bottles inside a wodden case (the hull together) and it (hopefully) will float.

[djwkd]

I mean wooden-not wodden!

[djwkd]

Aint someone going to post anything else now?

[sarawales]

I've almost finished building my raft. In the end I made 2 pontoons with 2 x 50 gallon barrels in each, attached together with 2x4 timber. By my calculation that gives me flotation for about 2400 lbs, and the total weight is 1800lbs. So, i think i'm ok. One question though - do i need to seal the timber that will be in or under the water?
I need the raft to be in the water for 30 days - in this time, will the wood soak up the water and get heavier and heavier til it sinks?

[Tim B]

A bit of wood preserver, or very thin epoxy won't hurt, but You've got a fair reserve of bouyancy and I don't think it'll fail structurally in a month.

When (and where?) will this be on display?

Tim B.