If you look carefully, you will see short bits of red wool attached at various places around the aft end of Wind Horse. We are using these to give an indication of air flow when apparent wind is on the bow, and to see if the air flow can be modified by angling the solar array. Although we were using woolies 40 years ago on our sails and superstructure as flow indicators, and more recently on glider wings, we didn’t think about this for the boat until last week.

Check the woolie on the angled pipe in the middle bottom of the photo. It is blowing forward, right into the air intake for the engine room. This could create a problem with sucking in our own exhaust, except that now that we have the swim step extension and the underwater exhaust, this is no longer an issue.

Angling the panels up in front does have a minor impact on air flow, as you can see here with the same woolie noted in the previous photo now tending aft.

More important is the finding that in these conditions at the aft end of the swim step extension, there does not appear to be any station wagon effect (reversal of flow).

Woolies can also be helpful in optimizing awning and hatch placement to augment ventilation. A piece of low-stick masking tape can be used to attach the woolies on a temporary basis.