Wing Sail rig for the Mac

[mastreb]

Another update. We're building a 6' wing section to prove out the theory, rigging, and confirm that the math matches the results. We picked this size for testing because it will fit in San Diego's public wind tunnel that is operated by the Aerospace museum. The full rig for the Hobie Trimaran will be 18' wings on 20' masts, but the same chord (width) as this shorter prototype.

The construction method we're using looks to work perfectly fine, so we will stick with it for the full scale prototype. We're making the ribs out of 12mm marine plywood and stapling 4 oz. dacron sailcloth to them. When tensioned, the assembly takes on a perfect wing shape as I'd hoped. We're finishing the top and bottom of the wing by stapling the overlapping sailcloth to the top rib and then bolting another rib to that above it, which will clamp the sailcloth between the two ribs and give it a finished look.


Wingsail under construction by mastreb, on Flickr

We do have to tension both the leading and trailing edges in order to keep them in perfect shape. The leading edge is easy, but the trailing edge I have to do some thinking about because it's so thin.

The mast and rigging is also working great. We're using 1.5" aluminum pipe made for speedrail, and using their fittings as the masthead and mast foot.

The wing goes up and down better than I'd hoped:

http://www.flickr.com/photos/68241682@N ... hotostream

It's considerably easier to raise and lower than a typical mainsail. We had thought we would need to use UHMW bearings but simply having slightly oversized holes for the mast in the ribs work great. The dacron does have to be "crunched down" a bit by hand when lowered to the bottom, but that's okay.

So far, everything is working great so it's full speed ahead.

[Catigale]

You picked the right colour at least, Matt.

I'm on the Shinkansen to Osaka and can't help noticing all the bullet trains are white, and the slower regional JRs are blue ....

Just sayin'

[Crikey]

Do you think the tension will be enough to prevent the leading edge blowing inward, without a stiffener similar to the bolt rope on a regular sail?

R.

[K9Kampers]

[quote="mastreb"]We do have to tension both the leading and trailing edges in order to keep them in perfect shape. The leading edge is easy, but the trailing edge I have to do some thinking about because it's so thin.quote]

For the prototype, ever consider using shrink wrap for the sail material? It would be shrunk to drum-tight for little if any flexing.

[Don T]

Seems like reefing this rig would be as easy as a 2 step hoist. Lines led through from below would allow hoisting only the upper part to half way. The lower ribs would stack at the bottom with the extra cloth. Simple with very little added rigging.

[mastreb]

Seems like reefing this rig would be as easy as a 2 step hoist. Lines led through from below would allow hoisting only the upper part to half way. The lower ribs would stack at the bottom with the extra cloth. Simple with very little added rigging.

That's exactly the idea. Essentially, we're going to have a separate reef-line stop-knotted at each of the three lower ribs. Untension the rig, pull the reef-line you want, cleat it off, and re-tension. Easy peasy lemon breezy.