Saturday, April 21, 2012

Spring Theory



Recently finished some rudder tooling so I should be on the water again soon. Have also been spending some time with CAD looking at foil shapes, which one might convincingly argue is a waste of time, especially as things drawn on backs of napkins seem to have less drag than their full-on professionally designed CFD counterparts.

Latest numbers from the tank suggest the foil I put together with Greg in 2007 is still some distance ahead of anything else upwind; hard to know about the top end performance but if I had to choose a high camber section vs. a reflexed flap, well, I guess the answer to that question is pretty obvious by now.

Rudder tooling being done I'm on to a new mainfoil, for which purpose I put together a parametric Rhino file to define the lifting surface so I can tweak it until the last possible moment. Perhaps by then Nick Flutter will have the poor man's CFD figured out enough to give it a whirl, but frankly if the accepted math is at all representative of the real world it should be a big leap forward from what I'm sailing (or not sailing) at the moment.

This all leaves much to be desired on the boathandling front, and sailing is certainly enjoyable. I look forward to getting back on the water soon, but in the interim I have to say designing and building my own stuff is a fascinating counterpart, and one of the greatest things about Mothing.

Sunday, August 14, 2011

Boom of Doom

Some wind today in Long Beach made for interesting test piloting on the new incidence control program:


San Pedro Bay is a decent place to sail in these conditions as there are a couple of long breakwaters. But the end of the channel is somewhat unprotected, has a fair bit of tide sweeping past it, and can be a real handful if everything isn't going according to program.

My plan was pretty straightforward. First, get thrown out of the protected harbor by the cops for speeding. Take a deep breath, sail outside to end of channel where I know it is blowing reasonably hard, find some protected water to play around in, and hope the boat behaves itself. Richard said be careful if you go outside, showing me his 27.9 kt GPS max, so I didn't take it lightly. Would have much preferred to bomb around inside frankly, as per my normal sort-the-crazy-ass-new-foilsystem routine. But I digress.

Thankfully the boat decided to behave, mostly. The new gizmos have pretty much taken care of the wand loading issue, and it is cool to zip along with less load out there. Need to trim the ski way down, and add a bit more gain, but no matter. May still be hanging up a bit on starboard tack, but nothing the air grinder and a bit of carbon won't take care of.

Capsized next to the Lifeguard boat in the lee of the oil island to adjust the wand linkage. They came over to check, and asked the fateful question: "So you're not going to need any assistance at all then?" I wanted to give my pat answer, which is that none of us has a crystal ball, thereby warding off evil spirits with circumspection. Clearly this would have been a better answer than "No", in retrospect!

Headed in as it was getting late. Foiling low to avoid surprises in the substantial lumpiness between the oil island and the end of the channel jetty, my practically new, sailed three times, heavy-duty-so-you-won't-have-to-worry-about-it boom decided to fold in half at the vang. Death roll, fiddle around with alternate sheeting systems off the back rack, get cold and a bit seasick from all the lumpiness. Finally realizing there was no way to sheet effectively and get upwind to the beach, or downwind through the worse water between me and where I needed to go, or in fact anywhere at all except drift up on the jetty itself, I waved the Big Red Boat over.

The BRB is not a RIB, but a 35ft twin diesel screw fire boat that will fit a capsized moth quite comfortably on the aft deck, provided the rig is removed. Which mine wasn't. Bringing me to the day's main lesson: if it is pseudo-nuking and you are sailing in lumpy water when you lose the boom, take the mast down right away and get the sail off, because you aren't sailing home and it isn't going to be any easier to do it with a huge red fire boat standing by after you have developed a case of mild hypothermia.

I'm probably tempting fate by saying it, but the things I expect to break, like all the dodgy parts and contraptions I make in the garage, don't seem to break. Similarly, the original Prowler stuff doesn't seem to break, unless it gets broken onshore or trailering. But anything I pay retail money for in the name of "improvement", like new masts and booms, is doomed!

Not sure I like the filament wound spars at all; I think the next boom will be a nice rolled bit of autoclaved prepreg - like the first boom that lasted me four years and has yet to cash it in. I have enough on without fretting over the possibility of random spar failures.