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Thread: Texas Goose

  1. #1
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    Default Texas Goose

    This video from Ian Henehan popped into my inbox this morning

    A Texas Goose with GIS rig and outriggers I think.

    https://youtu.be/lYNNymH7fIQ

    plenty more to watch on his channel including the build

    https://youtu.be/nWPoqvm-7jk

  2. #2
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    Default Re: Texas Goose

    The hull was finished a couple years ago and borrowed the rig and bits from the Blue Canoe. This year, I finally got time to finish up the GIS spars and hiking seats (not outriggers). This was the first sail with the new gear. Not much of a test with the light wind, but I was able to smooth out a few rigging details.

    I'm using the bigger GIS mast as well to handle the increase in righting moment. The goal is two crew hanging out on the seats going for broke when it's blowing. Trying to see what ridiculous extremes we can take a Goose and still not bust the bank.

    Ian

  3. #3
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    Default Re: Texas Goose

    The latest fun from my Goose project.

    https://www.youtube.com/embed/NJMWyVXbtq0
    Last edited by airbiker; 11-12-2018 at 10:09 PM.

  4. #4
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    Default Re: Texas Goose

    "here Bubba hold my beer and WATCH THIS"

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  5. #5
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    Default Re: Texas Goose

    Quote Originally Posted by airbiker View Post
    The latest fun from my Goose project.

    https://www.youtube.com/embed/NJMWyVXbtq0
    On foils?
    Creationists aren't mad - they're possessed of demons.

  6. #6
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    Default Re: Texas Goose

    Yes. The first attempts from Friday.

  7. #7
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    Default Re: Texas Goose

    the broach at 14knts looked exciting!
    Simpler is better, except when complicated looks really cool.

  8. #8
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    Default Re: Texas Goose

    That's great stuff! It's really expensive to make a foiler that can foil across a wide range of conditions. Once you accept that you're only going to foil when reaching in medium winds, taking the cheap option and making a foiling 'Goose is a great idea.

    More info on those foils would be very interesting. Cheers

  9. #9
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    Default Re: Texas Goose

    Thanks. I agree, there will be limits to how far this can go and foiling on a reach is the easiest mode. It was blowing about 20kts with gusts between 25 and 30kts. That's with the 105 sq. ft. GIS sail. That was really too much and it was getting difficult to get upwind. These foils add stability as you gain speed, even without flying the hull, so it would have been more difficult without them. Still, a little less wind probably would have made it easier to get flying earlier and find a little more speed. The hull is launching at around 6kts, which is a pretty easy speed to hit in a Goose, even dragging the foils. I bet it will launch in 10kts and stay up in a little less. Looking forward to figuring out where that line is. There is drag reduction without fully flying the hull, so it may still be faster than stock on those days that are 5-10kts.

    I think there might be a decent upwind mode where the hull isn't quite flying. It will take a lot more sailing to see if that's true. Off the wind is easy and it might even fly through a gibe with practice. I don't think flying tacks are likely with the draggy setup and low ride height.

    The main foils use a USA-35 flat bottom high lift section. Not a section with significant laminar flow expectations, but easy to shape and not as sensitive to deviations as a laminar foil. The T-foil is the symmetrical section used for the rudder and daggerboard on the stock Goose. Wing loadings are about half that of a Moth. I wanted to cheat towards low-speed launches with the trade-off of higher drag. Just trying to fly consistently at this stage. The foils are based on the work behind the Quant 23, so no new ideas there. I have about $100 bucks in all three foils. Mostly pine, a bit of carbon rods for the bending loads and some 6oz. glass. The profiles were shaped first and then the curve added via kerfing the top surface. Slot routed for the carbon spars, much like a foam model airplane wing. Construction is really quick and simple, with no molds or forms. This was the whole goal for this project. I aimed for something just about any amateur boat builder could construct easily. So far, so good. We'll see how they hold up with time.

    There is a lot of room for optimization, so hopefully the next set of foils will launch a little earlier and go a bit faster. This approach won't get anywhere near the Moth foilers, but should be a lot of fun and hopefully better than just a novelty. For now, I'm pretty happy that it worked as expected on the first try. I was prepared for considerably less.
    Last edited by airbiker; 11-12-2018 at 12:31 AM.

  10. #10
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    Default Re: Texas Goose

    Great project.
    Fun to see how it works and where the "sweet" spot is.

    Pity the jib is sheeted to the boom, it looks like it will choke out the slot.
    Perhaps a small sideways extension on the boom to free up the slot?

    How about a picture from the side and the fwd quarter if you get a chance?

  11. #11
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    Default Re: Texas Goose

    Thanks. I don't think I have any good pictures of the boat all rigged up, but this video shows it pretty well in spots. No jib. Just a balance lug rig. This is before the foils went in.


  12. #12
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    Default Re: Texas Goose

    From experience in sailing a couple of foilers, I'd be very, very surprised if the Goose could foil upwind. Rig drag becomes critical when you start foiling fast or going upwind, which is why the foiling Lasers only foil on a reach and normally use a fully-flattened Radial rig instead of a standard rig. The drag of the standard rig is too high for good foiling at speed, and the rig/hull drag and righting moment are wrong to allow the boat to foil upwind.

    The Moth gets around these issues remarkably well because even before they foiled they were extremely low-drag hulls with high righting moment and large, very flat and very low drag rigs.

    I still reckon she's a great boat and thanks for the information.

  13. #13
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    Default Re: Texas Goose

    You're right about the high drag rig. By itself, flying upwind at any decent angle isn't going to happen. I can get upwind a bit on the foils, but just barely.

    Pretty sure I have the righting moment. The beam with the wings is eight feet. The main foils reach almost three feet out from the hull, so once up on the leeward foil, I'm sitting about seven feet away from the center of lift. This is useful for carrying the 105 sq. ft. of sail, but not the right formula for flying upwind in any significant way.

    The foils start reducing wetted surface before flying the hull, like a DSS foil. So hopefully, there is an upwind mode where the foils do more good than not, even though the boat is not flying clear of the water. We'll see. It will be fun finding out.

  14. #14
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    Default Re: Texas Goose

    Since your apparent wind will be from the front, even on a reach, it would be a good idea to design with "going upwind" in mind.

    Without knowing the exact angles and forces, the following may or may not be applicable:
    One possible improvement might be to swap your foils port to starboard, so that the horizontal foot points inboard. Like America's Cup cats. That way the low pressure from the foot occurs on the windward side of the vertical leg, which will eliminate the need for a dagger-board. As you have it now, the high pressure on the leeward side of the leg might be limiting your lift on the foot, besides throwing off a vortex where it changes from high to low. The latter effectively results in two short, low aspect wings with high induced drag.
    For the same righting moment you would have to mount the foils on some form of outrigger.
    If you add dihedral on the foils as swapped above, such that the bend is at or above the surface, you would have the something similar to Hydroptere to experiment with.

  15. #15
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    Default Re: Texas Goose

    Sure, get going fast enough and every direction is "upwind". I think the limits will be set by the balance lug drag and inability to de-power/flatten past a certain point. It is the biggest compromise in the system, but I'd like to see how far it can go. Maybe not far. Don't entirely know yet. I can switch to a more modern rig later, if the lug falls too far short.

    Foil swap - That's a good point and has been taken into consideration. Care was taken to make sure the vertical part of the leeward foil isn't creating lift to windward. Specifically so that the direction of lift doesn't swap as you go around the corner on the foil. That would be a mess of intersection drag and weird vortices. That's also why there is still a daggerboard. In the video, I've got both foils fully down, so the windward foil probably is contributing lift to windward, but even in that case, the lift direction doesn't change as you go around the corner. Ideally, that foil will be retracted in the future and contribute little in any sense other than a bit of windage. I don't know yet if that will even work on this boat. It will be tried soon.

    The Moth isn't the best comparison to this project. They've been developed through racing for bleeding edge performance. This boat is intended to be easy to foil (seems that way), cheap to build (accomplished) and use the foils favorably upwind and down, even if not flying the hull (big question mark). The philosophy is more aligned to the work that led to the Quant 23 and 17. If I intended to replicate the performance and efficiency of a Moth, I would have built something very similar. This project is not that. This is just entertainment.

  16. #16
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    Default Re: Texas Goose

    Quote Originally Posted by airbiker View Post
    This is just entertainment.
    Entertaining indeed, and a good source of motivation.
    What are the main areas, dimensions and lift produced by the foils?

    I have been doing the math to see what will be required to get my solar kayak flying. As expected a longer span, all else being equal, produced better results. It was still sobering to see by just how much. Increasing the span of an already high aspect 8ft wing to 10ft reduced the power required for take-off by 30%. This translates into much better tolerance for changes in available power once up and foiling.

  17. #17
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    Default Re: Texas Goose

    You're nuts! I love it.

    Thanks for sharing.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  18. #18
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    Default Re: Texas Goose

    Quote Originally Posted by whiskeyfox View Post
    Entertaining indeed, and a good source of motivation.
    What are the main areas, dimensions and lift produced by the foils?

    I have been doing the math to see what will be required to get my solar kayak flying. As expected a longer span, all else being equal, produced better results. It was still sobering to see by just how much. Increasing the span of an already high aspect 8ft wing to 10ft reduced the power required for take-off by 30%. This translates into much better tolerance for changes in available power once up and foiling.
    Did you just add span or keep the area constant? Wing area to set take-off speed and AR to set induced drag at that speed (keeping area constant). Will be interested in seeing your progress.

    The main and rudder foils have a 9 inch chord. Effective horizontal span is about 37 inches on the mains for an AR of only about 4.1 to 1. The rudder foil is 36", so the AR is about the same. Very chunky and high induced drag. Running low angles of attack (about 2 deg) helps, but an AR of over 8:1 would be much more efficient. With this type of wing area, 8:1 would be close to a 6.5" chord with 51" span. It would take quite a bit more carbon in the spars, but do-able. All-up weight is about 350-360lbs, including the crew (me).

  19. #19
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    Default Re: Texas Goose

    Quote Originally Posted by airbiker View Post
    Did you just add span or keep the area constant?
    Area kept constant in the quoted example. If span is added without changing chord then take-off power is around 25% less.

    I plugged in your numbers with some simplifying assumptions.
    Worst case for take-off is when no lift is produced by rudder foil and main foils are producing maximum induced drag. By simply extending each foil by 6" the take-off at 6kts required around 20% less power. You might get lift-off 1/5kt sooner at original lift coefficient.
    As speed increases and induced drag becomes less, the benefit of the additional span gets progressively less. From 11kts the lower area of your original foils outperform the longer foils.

  20. #20
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    Default Re: Texas Goose

    Quote Originally Posted by whiskeyfox View Post
    Area kept constant in the quoted example. If span is added without changing chord then take-off power is around 25% less.

    I plugged in your numbers with some simplifying assumptions.
    Worst case for take-off is when no lift is produced by rudder foil and main foils are producing maximum induced drag. By simply extending each foil by 6" the take-off at 6kts required around 20% less power. You might get lift-off 1/5kt sooner at original lift coefficient.
    As speed increases and induced drag becomes less, the benefit of the additional span gets progressively less. From 11kts the lower area of your original foils outperform the longer foils.
    That sounds about right. The penalty for a lower AR is definitely at launch and lower foiling speeds. Wing area alone will only tell you what speed you need to generate a specific amount of lift (depending on AOA and CL). It doesn't help figure out the power required. That requires understanding the two drag curves and induced drag is the big one at low speeds. This is where higher ARs shine. I learned all of this from flying airplanes and playing with design in that realm. Wings are wings, but the concerns are different in a sailboat. I think it makes things clearer to talk about required power as you do, than just raw speeds. Airplanes do the same thing. They design for target speeds. If that is far enough away from their take-off speed, the wings can tolerate a lower AR and make it easier to build. If enough power is available and helped out with flaps, a high speed design can still have reasonable low speed performance. It just takes a lot more power to do it.

    It's possible for a very efficient foiler to require more speed to launch, but with less power than a less efficient foiler. Two obvious examples would be a Moth (very efficient for most factors) and mine (not terribly efficient in any regard). Current Moths can launch in pretty light wind. Less than 8 kts. I don't know the boat speed needed to launch, but they're getting there on a modest power budget. I probably need 10+kts to launch, even though the boat speed is around 6 kts. Lots more power required. Mine might be able to fly slower (don't know for sure), but it definitely isn't going to fly at the minimum wind speed required for a Moth.

    My goals and requirements are very different than a Moth, so it's not necessarily a problem, but it's good to understand what's going on. I expect to build many sets of foils by the end of this experiment. For sailboats, the wind required to launch is more interesting than the actual boat speed at launch. That makes it all about required power.

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