As of early 2021 it seems WindPaddle.com are no longer in business
Adding a rudder to the Seawave inspired me to drag out my cheapo disc sail. I last tried it three years ago on the Amigo (below) when it worked OK, even without a rudder. But of course, a rudder is much better for keeping the boat on the wind while sitting back with the paddle on your lap and your hands on the sail lines.
Pulling the sail out the 3mm fibreglass rod or ‘batten’ broke. I bought some more which, if anything, felt more pliable than the original but before I took it out it was broken in two places. Long sections of fibreglass rod in greater diameters can’t be sent bent so incur much higher postage charges which made reviving my KnockOffPaddle uneconomical. Worse still, removing the splintered rod from the sail (before I decided to ditch it) filled my hands with glass splinters for days. Nasty stuff.
I looked again at the original WindPaddle whose prices have dropped in the UK. Their Adventure II model is up by 13cm to 119cm or 47″ in diametre, making a claimed area of 1.42m (as usual π x r2. doesn’t add up to ‘1.42’ but never mind). It folds down to 42cm or 16 inches and weighs just 400g.
I asked about the cheaper Scout sail and why it’s rated at 4–15 knots when the new Adventure II is rated at 6–30kn. It’s not just the bigger area; the Adv II has a significantly stiffer composite batten to help hold its shape.
A problem with all sails is that they can start swinging from side to side in a recirculating frenzy before either settling down, collapsing or diving for the drink, possibly when the wind is more than they can handle. I recall with previous V and disc sails that lot of your time is spent managing that motion, rather than galloping across the waves like a flying fish, but the promise of achieving that is why I’m persevering.
When the £116 sail arrived, it certainly had a better quality feel than my smaller knock-off which went for under £20 on eBay. The sail fabric feels thicker and the key perimetre batten isn’t a regular GRP rod-like in a tent, but a flat flexible composite band about 8mm by 1mm. It takes significantly more effort to fold the Adventure II three times into its 16-inch hoop, but that should result in a more stable sail in action. Sea trials here.