Sadly WindPaddle.com went bust but now Anfibio make something similar

Packboat sailing

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 diameter, 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 diameter but with squidge some more (ovalise) to tuck securely into the floor of your boat, and weighs just 400g (+30g for a control line).
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. That’s important and why ships don’t have rubber masts.

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 persevere.
Update 2021: After having much better results with a AirSail on a packraft, I think some of this swinging could be down to clipping the sail to slack decklines, and not directly to mounts on the boat’s hull. I will try that next time.

When the £116 sail arrived, it certainly had a better quality feel than my smaller knock-off which went for under £20 on eBay and are now under a tenner. The sail fabric feels thicker and the crucual perimeter 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.