Sunday, January 6, 2008

Closing the Place Down

With a big storm rolling through over the past two days we had a very nice breeze from the usual direction in Long Beach today, but the skies were overcast and it was raining. Not exactly your stereotypical California Dreamin' weather, but perfect for some high speed mothing.

As my wetsuit just seems to keep getting thinner and now has a few holes in some rather stragegic locations, making for an anxiety-ridden wade into the surf, I decided to break out the polar bear suit and stay dry. A fleece suit under a drysuit kicks so much thermal ass that it isn't even funny, and it's more comfortable than a wetsuit. I was actually hot a couple of times, despite repeated swims, clouds, and 53 degree air and 53 degree water temp.

Something possessed me to finally implement a wand improvement I had been thinking about for some time, removing a degree of freedom from the thing and moving the pivot a bit, which in turn required manufacturing a new daggerboard cam. I swung big, moving the cable attachment almost 2 cm from its previous position (18mm to be precise), and creating a proportionately taller DB cam to take the throw on the other end with the same DB flap deflection range. I didn't have time to fine tune the new wand pivot before sailing today, as the glue kicked overnight and I was running late as it was, but this is what it looked like after some sanding with 36 grit to get the most offensive globs of epoxy off:

Basically, I just made the whole thing about 5/8" thick to remove the propensity to pivot axially. It tends to do this under load because the end of the ball fitting is actually over an inch outboard of the point where the original pivot arm attaches to the hull. So in its original configuration, the wand can move significantly aft without the ball moving aft at all, because the whole works just pivots around the ball, resulting in less fidelity between what the wand is doing and what the flap is doing.

To combat this, I glued a chunk of 1/2" G10 onto the top portion of the pivot arm, then ran a 1/8" sheet of black G10 down over this block and the adjacent original mounting block for the ball fitting. Then I moved the pivot point down a bit, because the bolt head was preventing me from jamming various rods into the receiver. I mean, what's the point of having a receiver if you can't jam rods into it? Anyway, this allows me to use an overlength rod and have it protrude out the top beyond the pivot in case I want to revert to Maystick mode, which I'm not sure I do, but options are always nice:

Right so now the bolt needed to be about 2cm longer, so I added that to the McMaster list on Saturday (recently discovered that their LA shop is local to me - this could be dangerous) and came home with five 8-18 stainless 70mm M6 hex shoulder head partially threaded bolts for the low low price of a gazillion dollars - the standard McMaster price. But they have everything, and if you call before you go the order will be in a box by the time you get there. That place is worthy of a PhD thesis in logistics. I came home with lots of other things, too, like metric drill bits and tons of tiny taps and dies that will come into play at a later date.

But back to the pivot - oh yes - always check your new cable length and wand ROM (range of motion) after messing with anything - small changes can make big differences. In this case, the new DB cam is so much taller than the old one...

that it forces the cable to take a rather acute bend at the deck bracket, increasing the friction a bit. The bow alterations didn't cause too much problem otherwise; the bolt was a bit overtight so the friction was higher but nothing some extra shock cord couldn't handle (shock cord setup not shown in photo):

Anyway, off to the races. Or rather, off to an empty beach with a huge line of flotsam at the high tide mark from the recent storm and nobody sailing except one kiteboarder. I mean, what is it with those guys? Usually they don't sail because there isn't enough wind. Then, when the wind is ripping, they stay home because it's cloudy and rainy. My theory is that they don't sail when it rains because they aren't trying to win anything - someone told me recently that they are starting to race kiteboards around the buoys, but they are going to have to go hydrofoil to get upwind very well from what I have seen. Apparently at least one person around here is doing that and the windward performance is startlingly superior to a regular kiteboard.

When I put the foil in at the beach, it became apparent that we were dealing with a bit too much cable length, resulting in too much flap down at just about any altitude. Lacking a Dremel cutoff wheel and a 10-32 die to re-establish threads on the rod, I opted to just hook the sucker up and go sailing.

And what a sail it was. The wind graph, courtesy of iWindsurf, and the passing weather system:

I started sailing at about 2pm, after micropressing some little copper gizmos onto my shrouds to keep the prodder from exploding, and talking to yet another guy about how I should join Alamitos Bay Yacht Club. OK OK - you guys are right. Just be sure to have some Portsmouth races while we wait for the Moth fleet to build up a bit.

The basic surf and sea outlook was this:

Though there are no whitecaps, that is only because this is Long Beach, and you have to go way out to get those. It is probably blowing 15-17 in this photo, and there is quite a bit more surf than normal. I didn't really think about it beforehand, but launching through this surf was challenging with the onshore breeze. Between waves the water was too shallow to sail, and when a wave came along, I was about two feet from touching the bottom, so I would shuffle like mad (stingray shuffle) with the boat in tow between sets and try to right it before getting set ashore by the next set of waves and the wind. Took me a few tries before I got away with a sensible waterstart instead of wasting all that time standing on the daggerboard and waiting for the mast to come up. Much quicker to start with the mast in the air if there is breeze.

Anyway sailing with too much mainfoil lift is an art. Basically, the boat was just flying a bit too high all the time, and I did various things to compensate, all contributing to less AOA on the mainfoil. First, I sat farther forward than I have ever sat. It didn't make much difference going to windward, but on any other point of sail the speeds were high enough that I just had to get rid of some lift. I wasn't in front of the DB case, but that's only because there is no tramp up there! Of course I was using a fair amount of rudder flap also, but there is only so much of that to go round, so I wound on another couple turns of gantry.

All this scrubbed enough lift to make for some ludicrously fast reaching. The wand was so sensitive that the boat would pretty much leap back to ride height if the nose went too low, but the rest of the time it just sat on height and went like a bat out of hell.

Until it came to running, that is. Offwind the whole works was simply flying too high for me to gybe. I did make it around once in relatively competent fashion, but nothing like I was hoping for based upon last week's ride. Serves me right for screwing around with a perfectly good setup. The ride altitude was simply a bit too high, and the flap was very sensitive, so I would achieve level flight sitting ultra-far forward, but then had to scoot back a bit to get around the mainsheet while initiating the turn. That tiny shift of weight alone, in combination with my overdriven flap setting, was enough to induce too much lift and start the whole works hobby horsing, which at the speeds I was going is really some mad sailing, and no way to set up for a gybe. I would move back a foot and into the center, and all hell would break loose, as the bow rose a bit and the wand finally clocked through its final 25 degrees, causing too much flap up and a consequent descent nearly to the surface, at which point the flap overdrive and speed would launch me skyward again, only to repeat the process until stacking it in one way or another. All this didn't keep me from trying many, many gybes, but reaching was going so well I eventually decided to give up on the gybes for the afternoon and blast around instead.

Probably not the best day for it in the end, given the recent rains, which scooped all the trash from the five county area into the LA river, where it descends toward the sea in a veritable avalanche of shit until it hits the trash booms at the mouth of the river - just next to my sailing area. Booms catch probably 95+ percent of the detritus, but I did have several interesting sightings: one mostly-submerged dark green plastic Wal Mart garden chair, several tree branches, plywood, lots of palm fronds, and various other potentially foil-killing pieces of junk. Caught a couple of plastic bags but ripped right through at least two after a brief stumble. Caught one on a run near the tip of the main foil and it got torn to absolute shreds by the time I slowed down enough to take it off. Amazing forces at work down there - bags feel a lot like solid objects when you hit them full on.

I suppose it is time to mount the Velocitek. I have been putting it off as most of the time I really don't care what my speed is - bragging about that crap is so gauche. Fundamentally the foils have a certain amount of drag and I think various Moth sailors have explored the upper limit of the current setup pretty well by now. But today I was going consistently way faster on the reaches than I have ever sailed this boat before, and it made me wonder how close to the limit I was getting. I mean, it was really fast. Ridiculously fast. I was way forward on the wing bar, basically even with the DB or a shade toward the back, and if I got a bit high I would just sheet in a bit and drive the nose down, which is really easy with weight that far forward. If I went too far down, the hyperactive wand would bring it back up instantly, and I would sheet in and drive lower. Again, and again, and again, hiking harder and harder and harder, steering through the wave sets to stay at about the same height. Keeping the nose down by sitting so far forward was critical, again with lots of gantry on and a fair amount of rudder flap. The overall ride height was actually pretty low and I only ventilated the rudder a couple of times.

At one point I was near the beach and decided to buzz a big cruising boat some distance off that was headed away from me, downwind under sail. It was probably a mile or more distant. Fortunately, the point of sail to get there was a deepening reach, and the wind built progressively the further out toward him I got. All this made for a really quick trip. I have done 18 knots on a canoe, and this was just a huge amount faster. It may have been 25 - I have no idea. It would be nice to have some sort of official number - to gauge my progress by if nothing else - ergo the sudden interest in mounting the V-tek.

I probably had five or six very long reaches like that before the sight of a tree trunk bobbing merrily along made me realize I was playing some pretty high stakes roulette, so I did some tacking around near shore. Finally I was so knackered that I was actually getting worse with more practice, so I did my best to get in through the surf without getting pulverized. I only had the waves flip the boat over its nose from one wing bar to the other one time, which was interesting and had never happened before. Fortunately there was no damage to anything.

I may take some height off the DB cam and move the forward cable attachment point back toward the pivot a bit to reduce the bend on the cable. The system has plenty of power in it to move the flap, so giving some power away to lower the frictive loads is probably a good idea. After doing that I'll recheck the cable length and trim or extend ends to suit. I have been doing some kicking around on the net to find alternatives to these sloppy little quick-release, off-axis-load balls and I have found some good options to reduce play and friction. So there will likely be more changes to the cable ends and/or a new wand receiver/pivot to suit. Apart from the cable length issue and shortening the cable cams a bit, I'm pretty happy with the new setup and I'm confident that with a bit less flap down the boat will be back to her old self on the next outing.

Long term there is a lot to do to make this whole height control thing better. I have lots of non-sinusoidal ideas about flap response that I may implement on this boat, but for the moment the goal is just to make simple changes to the current equipment to get it functioning reliably enough to improve my offwind boathandling while I finish the new foils. If I can learn to sail this boat reasonably well then I will have a good basis of comparison for the new system as we develop that, not to mention a huge amount of fun.

My best Wallace and Gromit/Wrong Trousers "Cheese" impression

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