Dave Clark

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About Dave Clark

  • Rank
    Anarchist

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  • Website URL
    http://fulcrumspeedworks.com/

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  • Location
    Rhode Island
  • Interests
    UFO, International Canoe, C-Class

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  1. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    We've tried to keep all changes to a bare minimum for the sake of preserving the strict one design nature of the boat. However, some parts wore down or were found to fail and have needed to change. Usually this is a matter of "more glue here/add some carbon or a bolt there" to keep these things budget neutral we have worked hard to reduce wasted process materials (peel ply, tape, vacuum bag, wasted resin). To keep it weight neutral, we've worked to match any beefing up with minor weight savings in obvious places. Besides replacing the metal brackets which flatly didn't last (we're still getting those handed out to people in the field. We can only make so many), the most profound change has been the addition of a more potent righting handle system. This doesn't sound like a big deal, as the other system worked, but being able to right the boat from a turtle five times faster is the difference between taking big risks on foil gybes and playing things conservatively. See attached picture. DRC
  2. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Essentially since the system is decoupled from pitch almost entirely, there is very limited control over overall flightpath. You're driving an oscillator. As a result you can't really play any sort of rhythm where you consistently gain altitude and cash it in as gain to weather. That's always been my experience with the foil following wands. They're gentler but their sense of where they are relative to the water and where the boat is going next is far duller. If you were blind, you would want to put your walking stick out in front of you, not behind you. Now I must get back to digging my turnips. DRC
  3. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Re: "sail like a 12meter" this means adopt a yachtsmanlike mentality and focus almost exclusively on pointing as high as the boat will go. Forget about speed altogether and just point 30 degrees higher. Re: "climbing the stairs". I'm almost certain you can't do this on the whisper, the F101 or the glide free foil package because the wand is aft of the foil and is apparently decoupled from pitch. DRC
  4. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Another worthwhile note from nearly a full week on the water as much as 12 hours a day: The bungee/spectra strop over the top of the mainfoil adjusters is a way too variable answer for keeping the gates closed. What you want is a horizontal strap rather than a vertical one. I put a whole new replacement gate system on 73 for the trip down to Baltimore and it was jumping out on day 1. GRRRRRRR. Day 2, I tried wrapping the outside with electrical tape. 100% better. It hasn't popped open or slid forward since. The pin itself has slid out of one side, which did facilitate a slide forward a couple times on the bouncy side of shelter, but in general, it constituted a huge improvement. I'm now on the hunt for the right velcro to glue to the gates on future production boats, so the wrapping strap can be built in. DRC
  5. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Nope, it's pretty canine in non-foiling conditions. However, I will say if you sail it upwind like a 12meter in light air you do seem to cut your losses a lot more. I didn't lose any more trees on the 16's once I figured that out. It's not moving fast but you can feel in the rudder that the induced drag on the foils is WAY down. Where I got killed on the first leg upwind was when the breeze climbed to 6 gusting 8 in the rollimng swells. I blew a whole bunch off ground bearing off and trying to fly, flying for a bit, coming down and trying to do it again. During that period my progress to weather was dwarfed by the 16's holding the same angle and simply seeing higher speeds. Once I was consistently foiling I was doing far better and seemed to be gaining ground quite steadily. However, what's got me very interested is a technique I started using that kept me on the foils (so going no slower than 8/8.5) but got my net angle even higher. Sit aft so that the control system is actually unstable. As opposed to sitting forward enough so the wand can dial back the lift and stop the boat from coming out of the surface, make it so that if you get up to enough speed, you're guaranteed to crash. Now point it upwind and build speed. Whenever the wand breaks free of the surface, pinch and lose speed but gain height. The bow will come back down and the wand will regain contact, bear back off to your true foiling angle and repeat. Skiffies call a trick like this "squirts", but I started calling it "climbing stairs". I'm not sure if it's always a good idea and I've only ever done it for one leg in specific conditions, but it sure did seem to yield some fearsome upwind VMG. Off the wind in waves, I learned to be a lot less fearful about pointing it deep downwind once my speed was up. Grow up and bear off and let your speed take you to the mark. What a huge learning experience! Thank you, southold yacht club! DRC
  6. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Elapsed time seems not to have been documented at all in the results. Notice how the corrected time and the elapsed are exactly the same but there is a handicap involved in the fleet. Fun race and I learned a lot. I appear to have stumbled into yet more upwind technique for pointing on the foils which was a lot of fun coming back to overtake half of the hobie 16s in the second segment of upwind climb on the south side of the island. Portsmouth ratings are based on polars, essentially on an open course, and don't ever account for times when there's a no-go zone on footing to take off on the foils etc etc which happens constantly in near shore distance races. Immensely broadening experience. I also need to get a lot more literate in flying downwind through multiple intersecting motor yacht wakes in a the mixing swirl of two tidal funnels. DRC
  7. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    5200 appears to be the winner of the "world's stickiest" trophy. Try that DRC
  8. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Pull the axel pins out of both bell cranks. Disconnect the pin between bell crank B and the pushrod. Pull the A-pull rod-B assembly out from the front of the sprit and tighten or loosen the threads on the end of the pull rod in the barrel nuts by rotating your bell cranks clockwise or counter clockwise depending on your need. I am continually stunned by water in the hulls. Our leak testing protocol is overwhelmingly thorough and we put a small vent hole in the hull in the one spot that is never submerged in water regardless of how upside down you are. Conventional practices are leading me no closer to an answer. Next step: witchcraft. DRC
  9. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    I think I caught lightning in a bottle the first time I rigged this system on the water in Ottowa. It killed the problem on a very worn out set of gates for three more races of very hard foiling and quite some hard landings. Attempts to replicate it here have consistently failed, so I have nearly zero faith in a written description of what I did being able to produce the same results from home rigging. The elastic tension must have been just right the first time I did it. Still working on this system. Did the top of the strut manage to make its way out of the top guide in the rudderhead and fall down, even though there's a washer there? I've seen that happen three times now and finally figured out that it's due to an oversized radius on the top trailing edge corner of the rudder strut. I firmed up the radius spec with mario to prevent that from ever happening again. If this is happening, the short term fix is to wrap electrical tape around the las 25mm of vertical strut, creating a big fat stopper. This will arrest any further plunging. Okay, terminology. See below picture. The trailing edge of the flap at the center has 1cm of range. The pushrod has 1cm of range. To get the foil working optimally, the pull rod must be threaded shorter (or longer depending on how its set up) so that it makes light contact with the aft tab on the back of the flap when the wand is fully unloaded. Therefore all aft motion on the wand will yield increased lifting force from the foil. The Push-pull systems on moths require very free flaps so that you don't overload the barrel nut and threaded end connection at the trailing edge. It's also susceptible to jamming throughout the system if you, say, fill it with sand and neglect if for 5 years by using it as a resort boat. We wanted to make a foil that's easier to build, maintain and more reliable. We also wanted to gain efficiency at the tips by forcing twist into the flap. So our flap is a driven by a push-push system. The flaps are cast at -6 degrees flap angle with 4.25 inches of sikaflex in each end. This forms a rough rubber spring which biases the flap towards the most negative part of its range. The pushrod deflects the flap down to +8 at the maximum end of thew range. This flap angling tapers towards the tips and the tips actually remain negative, achieving washout even in the most high lift mode available. To do this without the risk of hydrostatic forces (propeller wakes etc) seizing control of the flap and crashing the boat, we made the spring in the tip VERY strong and the cranks that push it VERY strong. So the signals that drive the system are far louder (figure of speech) than any other noise found in the surrounding environment. I've never found sand to be capable of jamming the system, or even bent pushrods. The power on the whole thing just crushes any drag in the way. DRC
  10. Dave Clark

    The new sailing twin skin setup

    Additionally, what information has been shared with me indicates that the theoretical soft wing can't achieve anywhere near as high lift coefficients as the hard wing, mainly as a function of the slot. Something tells me this hull and foil configuration are going to want TONS of power at takeoff and getting out of maneuvers. A hard wing usually helps with that. The normal "when you're foiling you don't need as much power" argument is intuitively invalidated to me by my experience with the difficulty of getting foiling and staying foiling. These systems need thrust. DRC
  11. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    I was actually just out in similar stuff on Bristol Harbor to beat up the J22s yesterday. In really heavy air, keep the shrouds relatively tight. NAIL. THE. OUTHAUL. Cunningham to taste. Keep the endplate sealed. About six inches of wand sticking out the top is nearly the healthy limit on ride height. Push it much higher and you'll be able to go faster at times but you can suck bubbles of air down the leeward tip of the mainfoil (stunning amount of ventilation) and if you're not heeled to weather you can really overload the mainfoil and vent the foil. Neither will cause you to crash but neither are fast or very directionally stable. Foils. Mainfoil set to minimum angle of attack. You don't need the extra lift. You need control. So biasing the control range of the foil as negative as possible is a big plus. Also you're cutting a lot of drag. Rudder to taste. Don't fly nose up, for god's sake don't. Usually this means so far down that the tiller is nearly hitting the hand wheel, which is the natural lowest rudder AoA attainable. Going for peak speed. Try to hold about 7 degrees of weather heel and just stay laser focused on one point you're steering towards. Try not to touch the tiller at all. Steering is slow and unstable. The boat is a missile and you are the guidance system. DRC
  12. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Smart. Keep those landing gear close to the runway and you'll never dig the wing.
  13. Dave Clark

    Steve and Dave Clarks Unidentified Foiling Object

    Big ocean swells are easy and fun. Sort of like skiing on a big groomed hill. You go gently up, you go gently down, repeat. Short chop is a tougher scenario. 1.5 to 2 foot steep chop, you can simply punch through. The wand just finds the average and keeps moving. Once you get into 3 foot range, while the boat will track fine on the foils upwind, you need to navigate the mogul field downwind. Basically work on plotting a route through the troughs. The worst conditions are in (Big Breeze)+(Outgoing tide)+(Shallow waterway). There you need to be a jedi, which is a rewarding learning curve in itself, but a bit wet along that curve. Regarding improvement over time, we've taken each opportunity to make obvious fixes to what I've seen as legitimate issues and bugs and I'm both happy to say and depressed to admit that #151 is significantly better than #15. But I'm not holding back a slew of improvements in order to release some sort of Mk2 version. All changes have been reverse compatible and released as quickly as feasible. The objective has never been to incentivize new sales with existing owners half as much as to fix errors as quickly as they're discovered. When people ask me "what's the new version going to look like" or "what's the next design going to be" I reply "exactly like this" and "what new design?". I'm nailing my balls to the mast on this and I suppose that's reassuring from a customer's perspective. Don't worry. It's figurative. DRC
  14. Dave Clark

    Backwards Skiffs?

    A Cherub?
  15. Dave Clark

    Backwards Skiffs?

    That flipside off the wind and most importantly on oceans is the one that scares the Bujeezus out of me. "Naw dood. It's fine to have waves the size of freight trains going right over the deck every 200 seconds. It'll make monohulls powered by lead cool again!". Meanwhile the Dali foil boats just bounce around on top of the swell and actual wave piercing multi don't ask crew to venture onto the hull that's doing the piercing. Edit. Clearly I'm a bit opinionated about this. Didn't mean to drift the thread. It just intersects with one of my pet design peeves. DRC