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Thread: Vixen (Antonio Dias) design ideas

  1. #1
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    Default Vixen (Antonio Dias) design ideas

    Hi,
    Some time I have come across Antonio Dias Vixen design (https://antoniodiasdesign.wordpress....rtfolio/vixen/) and now and then I go back to the web page to look at the design.
    Vixen2.jpg
    I like lines of the boat and philosophy behind design. But some ideas raise questions about applicability, for example:
    1. No engine. The idea of maneuvering only with sails is great, but in reality ports require boats to have engines (for example, https://www.google.com/maps/search/k.../data=!3m1!4b1).
    2. Winged rudder. Probably it would improve performance. But also would catch everything that is under water: plants, nets, etc. especially in shallow waters.
    3. Not self-bailing cockpit. Should be comfortable to sail only in sunny climate?

    What do you think?
    Jonas

  2. #2
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    Default Re: Vixen (Antonio Dias) design ideas

    Hi Jonas.
    I don't think a self bailing cockpit is essential in a 20' boat, it's probably rare. Few boats get take solid water onboard in normal sailing unless they capsize.
    Having sailed two boats for years without an engine, I agree that it's challenging and limiting. I don't think I would tack through that long entrance channel. Perhaps a small outboard, even electric could be mounted on a bracket? I used a 55# thrust trolling motor on a 20' sloop weighing one ton. Mostly I sailed her, but occasionally in a calm I would motor.
    I've never had a winged rudder, but it's a concern. Perhaps you should write to the designer and ask if the boat will perform with a standard rudder.
    Good luck, keep us posted.

  3. #3
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    Default Re: Vixen (Antonio Dias) design ideas

    If you're not already in communication with Mr. Dias about these questions/issues... you should be.
    David G
    Harbor Woodworks
    https://www.facebook.com/HarborWoodworks/

    "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

  4. #4
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    Default Re: Vixen (Antonio Dias) design ideas

    I'm baffled by Dias' claim that the video of the Arey's Pond Daysailer "shows (the (winged rudders) astonishing effect on performance". The vid shows a boat sailing alone, in what appears to be a misty day which affects our vision and perception of wind strength. It doesn't turn particularly fast, it doesn't seem to sail particularly fast, it doesn't go past any other boat, it shows nothing that can provide any indication of performance.

    As a comparison, adding carbon semi-circular foil centreboards and wings on the rudders of an ultralight, ultra-fast 75kg (fully rigged) 18 foot A Class catamaran adds about 2% to their speed. It is extremely unlikely that adding a rudder foil on a heavy high-drag daysailer will have anything like the same effect as adding rudder wings and C-shaped centreboards (which can actually lift the entire boat out of the water) do to an A Class.

    However, if by some fantastic chance chucking one wing on an Arey's Pond has the same effect as adding four lifting "wings" on a carbon fibre wingmasted racing cat, then the Arey's Pond will go about 0.08 knots faster. That is hardly an "astonishing effect".

    Secondly, the video doesn't provide the proof that Dias claims. I have been lucky enough to sail with and against many Olympians, America's Cup sailors and world champs. I'm sure that none of these people, whose livelihood depends on assessing speed, would pretend that they can look at a one-off displacement boat in a short video, with no boats around to compare the speed, with sail trim of unknown quality, with a bottom finish of unknown quality, in wind with strength, shear and density of unknown quantity, and say "oh yes, that is clearly sailing at 4.08 knots when without the rudder it would go 4.00 knots".

    Without trying to be hyper-critical, that sort of over the top claim could mean that everything else the designer said would have to be taken with several grains of salt.

  5. #5
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    Default Re: Vixen (Antonio Dias) design ideas

    Having listened to Mr Dias speak about his boats and designs, I came away unimpressed in some respects although he designs some very pretty boats.
    Tom L

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    Default Re: Vixen (Antonio Dias) design ideas

    Yes, I've just done some more digging and am now unimpressed. I see his pretty 29 footer is rated as half-way between a J/24 and Catalina 25 in speed. It's a lovely boat but with respect, not particularly quick for its size (not that there is anything wrong with that at all). Dias also claims that his heavy 23 foot cutter BitterSweet is "the fastest mono-hull her size I've ever sailed on" and that it "walks away from high-performance Marconi rigged boats and refuses to be run down by anything under around forty feet".

    Of course, if Dias' claims are true, his 23 foot cruising cutter would be (1) probably the fastest gaffer of around its size in the entire world, therefore faster than the German lake dinghies, the big-rigged Falmouth Working Boats and Couta Boats, the NZ Mullet Boats, the reproduction gaff-rigged Stars, the Sydney Harbour Historical Skiffs, the lighter Herreshoff Buzzards Bay 15, and many others; (2) be as fast as a carbon-fibre assymetric spinnaker bulb-keel 23 foot sportsboat or Melges 24; and (3) be dramatically faster than Dias' 29 foot bulb keel sloop rigged cruiser/racer design. And, for that matter, faster than an International 6 Metre, a Star, a J/35, an Alerion Express 38, an Etchells or a Shields. Really?

    If Dias' 23 footer is all those things, then it is the world's greatest miracle of boat design. It also indicates that he is a very erratic designer, since a designer of skill would not turn out a 23 foot cruiser that is enormously faster than a 29 foot cruiser/racer. It sounds more like he makes (ahem) extravagant claims, and if one makes such claims about a quantifiable subject such as speed then how can one rely on claims about more subjective areas?
    Last edited by Chris249; 03-24-2019 at 09:00 PM.

  7. #7
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    Default Re: Vixen (Antonio Dias) design ideas

    Looking for winged rudder I found a page about National 12: https://www.national12.org/hints/winged_rudder_guide/

    Seem like the effect is felt at speeds starting from 2 knots; the trimming at different speeds is required, for upwind example:


    • Very light; wings slightly off the max position. Your aim is to set them in the lowest drag position
    • Light to Moderate; wings hard on for maximum lift
    • Windy / Choppy; wings steadily go off to reduce drag (more lift not required).


    Overall it seems that winged rudder ads to performance, but also some tricks have to be learned. So I guess it makes more sense to use it on sport boat than on family weekender.

  8. #8
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    Default Re: Vixen (Antonio Dias) design ideas

    Yes, they've been used in N12s and Int 14s for some time. Before that they were in Moths. A Class cats, as noted, use tiny ones. Most of those classes are quite short boats (in terms of DLR, SA/L ratio, BMax/L ratio etc) and many of the top designers say that the wings are mainly used to overcome the problems caused by short high-powered boats with narrow waterline beam being driven hard. In the As they were mainly to stop nosediving. These are not problems in a daysailer.

    The wings also tend to be scarily expensive. To be efficient they are normally carbon. One of our A Class skippers noted how worried he was when his winged rudder hit a submerged object last week, and he's a pro and Olympic medallist and (I think) sponsored by the manufacturer so it would be even more of a problem for amateurs. A thick cheap foil may well have far more downsides than the beautifully shaped carbon ones used on racing boats.

    Finally, winged dinghies and A Cats are sailed fairly flat. In my limited experience, and from what others say as in the N12 piece, winged rudders don't work well on boats that sail at an angle like ballasted monos.

  9. #9
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    Default Re: Vixen (Antonio Dias) design ideas

    Not hugely relevant to the boat at the heart of this thread but the rudder foils on International 14's are getting close to having a 4 foot span.

  10. #10
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    Default Re: Vixen (Antonio Dias) design ideas

    Surely the rudder end plate on Vixen is just to reduce end plate tip spiral vortex losses and help draw laminar flow over the rudder sat aft of the keel. It's a shoal draft boat and improving rudder efficiency helps to keep the size smaller, and so it can be launched off the trailer without it knocking since he's chosen to put it under the boat for his chosen aesthetic. It will also reduce pitching at the expense of some wetted area (but he's cut away the keel aft - so thats a wash) and turbulence. She's a beautiful boat, a nice mix of old, recent and new for the right person. Dias seems to be able to combine engineering and aesthetics very well. Phil Bolger used rudder end plates on many of his shoal draft boats, more recently Welsford's Pilgrim, most aircraft wings and just look at F1. It's just a detail, a talking point but no biggie.
    Last edited by Edward Pearson; 03-26-2019 at 06:15 AM.

  11. #11
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    Default Re: Vixen (Antonio Dias) design ideas

    Good point Edward, and well said.

  12. #12
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    Default Re: Vixen (Antonio Dias) design ideas

    Quote Originally Posted by Edward Pearson View Post
    Surely the rudder end plate on Vixen is just to reduce end plate tip spiral vortex losses and help draw laminar flow over the rudder sat aft of the keel. It's a shoal draft boat and improving rudder efficiency helps to keep the size smaller, and so it can be launched off the trailer without it knocking since he's chosen to put it under the boat for his chosen aesthetic. It will also reduce pitching at the expense of some wetted area (but he's cut away the keel aft - so thats a wash) and turbulence. She's a beautiful boat, a nice mix of old, recent and new for the right person. Dias seems to be able to combine engineering and aesthetics very well. Phil Bolger used rudder end plates on many of his shoal draft boats, more recently Welsford's Pilgrim, most aircraft wings and just look at F1. It's just a detail, a talking point but no biggie.
    Sure, but it's odd that the designer claims that it makes a difference that can be seen in a video, which is an extremely improbable claim. And given that endplates come with plenty of downsides (wetted surface, heel effects, junction drag) it may hinder efficiency rather than enhancing it - particularly when Dias's wings are radically different to those used by the guys who develop them through CFD and running through endless trials.

    Personally I wouldn't believe much from a designer who claims that his 23 foot cruising cutter "refuses to be run down by anything under about forty feet". If that was true, his 23 footer must be faster than the famous and immaculately handled and kept S&S 53 Dorade; the Herreshoff New York 40; the Melges 24; the International Eight Metre (modern and classic) the International Six Metre (modern and classic); the International One Design; the Herreshoff Buzzards Bay 15 and 25; the Alerion Express range, including the 38 footer; the Concordia Yawl; the 30 Square Metre; the New Zealand classic 22 foot Mullet Boats, which carry several times the sail of the Dias design. All of those craft are regularly run down by typical modern production 40 foot cruiser/racers.

    Either Dias exaggerates enormously, or he has succeeded in breaking the laws of naval architecture when Herreshoff, Farr, Reichel/Pugh, Bjarne Aas, Fife, Watson, Reimers, Hunt and Olin Stephens couldn't. I know which of those alternatives is more sensible, and I just can't work out why some designers expect us to swallow such a load of (censored).
    Last edited by Chris249; 03-26-2019 at 09:26 PM.

  13. #13
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    Default Re: Vixen (Antonio Dias) design ideas

    I have no reason to believe an end plate on a rudder even on a slow boat is not effective. The other claims, sadly, are a bit stretched beyond reasonable doubt. A pity the artistry of some of his designs can lose attraction when such claims are made.

  14. #14
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    Default Re: Vixen (Antonio Dias) design ideas

    Nigel Irens put an end plate on the rudder of my Romilly. Shallow draft effectiveness.
    Ben Fuller
    Ran Tan, Liten Kuhling, Tipsy, Tippy, Josef W., Merry Mouth, Imp, Macavity, Look Far, Flash and a quiver of other 'yaks.
    "Bound fast is boatless man."

  15. #15
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    Default Re: Vixen (Antonio Dias) design ideas

    Unless you regularly transit a canal where an engine is mandated, some practice and the use of the sweep Dias shows will get you around just fine. You might explore mounting oar locks on each side (even with a sweep there will be times you want to sweep from the other side) but also one on the stern so you can scull in places too narrow to get the sweep out over the side.

    The rudder wings look very well considered as real wings, not just tip vortex plates. The Ayres Pond Daysailors find that the rudder wings allow better speed and control than a conventional rudder and that at much shallower draft. They love them. No tangle issues and that's a shallow bay with very weedy bottom.

    If you're not crossing the Atlantic, you really don't need a self-bailing cockpit. It's generally good to have a 1-1/2" diaphram pump located such that either crew can pump or the solo sailor can pump and steer. You won't use it much but you'll feel better. It's virtually impossible for rain to sink a boat unless you leave her utterly unattended for a month of rainy season. However, eyeballing the boat's rainwater collection ability - basicly the surface area looking down at everything inside the cockpit coamings - seats and sole - you could collect 4 cubic feet of water for every inch or rainfall. A common manual pump available here can pump a maximum of about 15 gallons per minute so in theory you could clear an inch or rainfall in about 2 minutes but nothing ever works that well. Figure five minutes of pumping if you had rain during the week and if you don't up up a boom tent. Hardly the end of the world.

    Great boat. G'luck

  16. #16
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    Default Re: Vixen (Antonio Dias) design ideas

    Thank you for the interesting discussion!
    Best regards,
    Jonas

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