Thoughts on the Gantry

The posting of Adam's picture of me swimming in at the Gorge (above), recent blog posts by Nat and by MARKLA, and last week's sailing at the HHPDO in Rye, have all got me thinking about gantry forces.

When I built my first rudder/gantry system I was most influenced by Bill's comment that the back of his rudder cassette had blown out during a heavy air day. To prevent the same thing from happening to my boat I made a cassette that was probably overbuilt, but didn't fail. That first rudder and horizontal were serviceable (they're what I'm using in the photo on the right sidebar) but I was sure that the whole sytem was less than optimal, due to the size of the horizontal; and to the thickness of the strut.


In building a second rudder for the Worlds, I wanted to accomplish four things: (1) reduce drag by using John Z's thinner strut section and a much smaller horizontal (eventually a Beiker section built by Bora,) (2) reduce weight by eliminating the rudder cassette concept and instead pin the rudder directly to the gantry (and using a rudder with a hollow tube head and removable tiller/hiking stick to make the system managable,) (3) improve the worm gear set-up to make the adjustments more positive and easier to accomplish, and (4) incorporate a five degree forward cant similar to the Mach2 design to help prevent ventilation.



After an unfortunate sail/break/repair cycle the current product can be seen in the above photo of me sailing in the Heineken regatta last weekend. I'm generally pleased with the rudder, tiller, and forward cant, but am still worried about the strength of the lower gudgeon and the gantry attachment points. Looking at pictures of the rudder when sailing in heavy air, it became obvious to me that there is a huge amount force applied to the lower gudgeon, and that at speed, while the amount of force decreases linearly with the ride height, it increases quadratically (not exponentially, Karl) with the speed through the water. The best way to reduce straight line drag would be to fly higher and to incorporate thinner strut and foil sections, with very fine surface finishes (maybe even with a SLIP coating?) all of which I'm well on to way to accomplishing. The dynamic drag force is high with erratic steering, something that I may have to deal with for a while until I get my helmsmanship skills up to par. All of these drag forces are trying to rip the gantry off the boat, or the rudder out of the back of the cassette, if so equipped, or the lower gudgeon off the leading edge of the rudder.

When I went to the Gorge Worlds I brought my new rudder and gantry, neither of which had ever been used before (BIG MISTAKE!) Adam's photo was taken after the gantry lower tension tube separated. The plug that attached the bottle screw to the carbon tube came out causing a cascade of failures (how appropriate?) with the gantry's upper attachment points ripping off at the hull connection. It's too bad that I didn't get seamanship points for nursing the boat back to the beach without the rudder. Additional style points could have been awarded for allowing the rudder's horizontal to appear as a shark's fin cutting the surface behind me! I repaired these failures with a rather agricultural-looking aluminum plate and through bolts for all the tube plugs and eventually managed to get in some racing, even recording a 20.3 knot 10 second average speed on the afternoon of the speed challenge. On the second-to-last day of racing, however, I again had a rudder failure, this time with the lower gudgeon popping off the rudder.



In preparation for last weekend's regatta I replaced the lower gudgeon, reinforced it with ten layers of carbon cloth, and bolted the fitting through the rudder, in addition to the glued attachment. Things held up for the racing (the only failure that occured was not rudder related, but at the other end of the boat at the wand pivot.) But close inspection of the joint reveals stress that caused the primer paint to crack. Obviously, I need to re-engineer this lower rudder fitting! Again. Stay tuned for the winter project that will include a whole new gantry with different hull attachment points the will reduce play in the whole system. The work of the home builder is never completely "sorted."



Sailing photos by Allen and Daniela Clark from The Photoboat.com

Heineken HPDO

I'm almost recovered from the long weekend. It's about a 7 hour drive from Norfolk, VA to Rye, NY not counting the needed stops for gas, food, stretch the legs, and the always present traffic on I-95 around the NYC area's George Washington bridge and Cross-Bronx expressway. Leaving after work on Friday resulted in an 11:30 p.m. arrival at Peter Becker's house, just a mile or so from the American Yacht Club. Susan and I crashed in a soft bed then woke early Saturday morning to the smell of coffee and eggs whipped up by our excellent hosts Peter and Adrianne.

Saturday consisted of finishing the registration process, picking up the nice polo shirt and freebie packet, confirming the dinner buffet reservations then rigging up for the planned 10:00 a.m. gun. Besides Peter and me, there was Chris Williams (the eventual winner,) Matt Knowles, Jamie Gilman, and Ethan Brown. We had a nice floating dock to rig on and launch from, so no need to wade out and get wet (yeah, right.) The forecast called for about 10-12 knots with slightly overcast skies. I hit the water first and sailed out. Not more than 5 minutes from the club my wand plate popped off the hull and I had to return to the dock. Obviously I was out of commission until the afternoon races. Peter provided me with the his basement workshop and necessary repair materials and I got to work gluing and screwing. So I had no first-hand knowledge of the first couple of races, but the score sheet shows Chris, Matt, and Peter finishing 1-2-3 respectively in both races.

I arrived back to the club with my repair completed (but not fully cured) around 11:30 to see Jamie sailing in. The breeze had built to around 15 knts and he was having problems controlling the boat. He offered me the chance to sail his boat (a new BR RX and so I jumped at the opportunity.) When I headed out for the third race, I passed Ethan who was heading in, also with control problems. I managed a flyby of the Photoboat in Jamie's RX.


This was the first time I had ever sailed a production foiler and I quickly was impressed with the firm steering (I love the aluminum gantry) but found my height control to be problematic. I quickly discovered why Jamie was having problems. His set-up was less than optimum: even with full lift on the rudder and me sitting on the front wing bar, in some of the bigger waves I couldn't keep the mainfoil in the water off the wind, resulting in some spectacular crashes. His gearing was not providing sufficient down lift to prevent ventilation. I managed to start the third race with Peter but couldn't finish due to handling problems off the wind. After the start of the fourth race the sky cleared with the frontal passage and the breeze really started to pick up.

I decided then and there to head in, basically upwind about a couple of miles. So I bailed out at the weather mark and struggled to make it in. The breeze had some monster gusts and also some pretty violent shifts. I chatted with a J-109 sailor later in the day who was sailing on an adjacent course. He claimed one monster puff showed 39 on their wind gauge and caused four J-109s to broach simultaneously. I can't say I ever saw that much, but I'm pretty sure there were some gusts to 30. With the added waves, the sail in was interesting to say the least. The best picture of the day is Chris sailing ealier. Believe me, the wind was much higher than this around 2:00 p.m.


Saturday dinner featured a buffet and a talk by Mark Lindsay. I left with a full draughtkeg of Heineken to take home (a 5 liter mini-keg,) and some nice memories of 5o5 sailing back in the day. Back at Peter's house Susan and I hit the pillow around 10:00 p.m and slept the sleep of the dead.

Sunday had three more races, sailed in breezes of about 5-15. I heard the infamous phrase "the race committee has established your position," a couple of times but did enjoy some close racing at times. My speed was impressive in spurts, but I still need to work on boat-handling. Being tired from the day before didn't help.

All-in-all it was a great experience. The venue, the hospitality of Peter and Adrianne, the take home goodies, and the opportunity to get some professionial on-the-water pictures all will encourage me to come back next year. Even with the loooooooooong drive home.

Sailing photos by Allen and Daniela Clark from The Photoboat.com

The Cost of Development

All mothists are privileged to enjoy the thrill and excitement of the modern foiler. Most have no idea of the cost in time and $$$ that a small number of developers have spent to make it all possible. Preeminent among those is John Ilett. As the first to realize the concept of a wand-controlled flap, he has seen his idea blossom with first the ubiquitous Bladerider and now the Mach2, while his Fastacraft Prowlers have been relegated to the small minority of active race boats. Recently John attempted to regain the cutting edge with a new generation of foils that featured a 48” (122 cm) wide mainfoil and a nearly seamless flap mechanism. This was also his first attempt at the two-piece foil, having seen the writing on the wall with the predominance of the BR and M2 bulbed foils. I was the recipient of one of the first of these “gen3” foils, as described in this post, having received it shortly before the Gorge Worlds. The story was not a happy one. On the first outing, the foil collapsed and repeated attempts at repairing it failed. If it wasn’t for Andy Mills loaning me his spare foil, an older one-piece FC daggerboard, I would have spent a couple of weeks at the Gorge watching from the beach.

As it was, I also had problems with a never before tested gantry, so all of the time on the beach (and in the rescue boat) can not be laid at John’s feet. But the one thing that I thought would bring me close to the front of the fleet ended up being a complete failure. John has since attempted to make the gen3 design work, and has temporarily given up with it, and has gone back to his 2nd generation design, albeit with a bulbed attachment. I just got the new “gen2b” mainfoil, at no cost to me other than shipping, as a “warranty replacement.” Such after-the-sale-service is remarkable. I can’t imagine John’s cost of the design and creation of the steel mold that he used for the gen3 foil, that now is but a bucket of $$$ out of the bank account with nothing to show for it except the lessons learned.

Not all development moves forward. Surely the advances are what we all look for, but it takes those with the guts to try something new to make anything happen at all.