Homemade Tarp Boat

[rwatson]

Yes, the previous advice is correct - that cheap blue tarp will be useless! To hard to fasten to wood frames without tearing badly, and it will rot in the sun. If you want to prove it, nail a small piece of the blue rubbish to a wooden plank, and watch it rip as you pull it.

The painters drop sheets are an excellent idea, but you can get heavy calico from fabric shops cheaper, I believe.

That hull drawing is very unsatisfatory. Why have those ugly sharp angles at both ends? Its easier and cheaper to have a smooth flowing, bent timber hull than the weak and fragile arrow shape.

Carefully study the picture of the boat frame provided before

[ancient kayaker]

I am surprised to read tarp rots in the sun; it is made for protecting things like trailers that are stored outdoors. It made an adequate sail, mine lasted several years and died in a fire, but it was awful noisy. Unless you stretch it tight you'll never catch fish from this boat ...

What is your object, low cost (a short life but a merry one) or low weight or just ugly for the hell of it. I read somewhere about an adhesive tape for tarp that becomes permanent when exposed to sunlight, although I would want to test it before I used it. Tarp is hard to glue, been there, tried to do that. It sows well but the seams will leak. Nailing won't last long but you can try screws and battens. It'll probably work for a while; guys have even used food wrap for skin boats although it is usually only good for an hour or so.

As for me, I'm cheap and want low weight. I use marine ply now but my first few boats were made with door skin (1/8 luan) at $11 per sheet, good for a few seasons only but it allowed me to learn by doing and I never fancied skin boats. If you're the "can't learn from a book" type like me maybe that would be the way to go but inspect each sheet carefully as some of it is punk.

[rwatson]

The experience I had with that cheap blue tarp "rotting in the sun" was a length of it laid over a boat. I think the fact that it wasnt tied tightly meant that the wind was constantly flicking it about, and that result in frayed edges and where it contacted hard surfaces.
As a result, the "blue stuff" peeled off the white fibres, and the UV seemed to turned the white fibres into white fluff.
I think the "blue stuff" is UV imprevious, because there is still lots of it floating around the back yard, and it hasnt rotted!
Whatever the "white stuff" is, it doesnt seem to like UV.
In any case, I just dont bother buying it any more, as it is such rubbish.

[PAR]

All these plastic, loose weave type of tarps will de-polymerize in time, usually in about a year of continuous sunlight (here in Florida). The silver ones last about twice as long, but these too will break down from UV and after a single year, clearly show signs of breaking down. It doesn't matter if it's pulled taunt or left slack. If allowed to flog, of course fatigue will enter the mix, but UV will break down the polymer chains into the shreds we're accustomed to seeing.

[alan white]

I remember when you could only buy heavy cotton canvas tarps which had been treated with some concoction of cupric oxide (copper).
This is basically your common painters drop cloth, except heavier and with grommets along the edges.
I had one and it lasted for years. Holes were self-healing and they were heavy enough not to flog (which is what really kills plastic tarps, and what makes me wonder WHY anyone uses them for sails).
Now, despite the fact that China could easily bring back these high quality tarps, I don't see them in the big chain stores. I'm sure they do exist all over, but where are they?
I guess this diverges from the use of tarps for sheathing a boat, having more to do with covering a boat perhaps, but those plastic tarps are abyssmal excuses for what our grandfathers used all the time.

Alan

[dragonjbynight]

probably just cheaper to make and have a higher profit ratio.

[ancient kayaker]

I use tarp for small sails on smaller boats like a kayak because it's waterproof. Typically when sailing a kayak I spend half the time paddling and it's nice to be able to lower the sail, mast and other accoutrements and clear the deck. It's hard to keep the sail out of the water.

When you're that low in the water a sail that doesn't get soaked is a big advantage. I tried nylon, it set nicely and was quiet but weighed a ton after it ended up in the drink. Tarp is incredibly cheap and very light, however I like to have it all packed away before I get back to the marina so the real sailors don't get embarrassed.

Other than being noisy, the main problem with a tarp sail is the material won't stretch. I have to allow for that in the design so it will set OK.

[juiceclark]

Sorry I'm late:
I built a boat bunker using a fantastic tarp that was very cheap. People often use them for pond liners. You can buy used billboard signs on Ebay (guy sold me one from Texas). For $40 plus shipping I received a 15'x50' sign that is incredibly puncture and UV proof. This one has been under my boat in a FL canal for three years without a puncture.
The absence of flowing water under my boat prevents any growth. The tarp has a very slight positive buoyancy.
Tony in Sw FL