Aerorig on a Thunderbird 26?

Discussion in 'Boat Design' started by misanthropicexplore, Jul 22, 2018.

  1. misanthropicexplore
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    misanthropicexplore Junior Member

    How would a newly built Thunderbird 26 do with a purpose built Aerorig (equivalent) ? Would it be better to pay a designer to come up with a similar concept from scratch? (Better here meaning, safer for cruising without an engine).
     
  2. Rurudyne
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    Rurudyne Senior Member

    Coolbeans that you have plans for the Thunderbird.

    I've read about the aerorig and like the idea too. As it's free standing I think the main concern outside of keeping the center of pressure located about the same (not rocket science) will be proper deck reinforcement and you might be well advised to seek out help for that, not because making the deck stronger is hard but because making it strong enough to do the job without being wildly overbuilt may be.
     
  3. Richard Woods
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    Richard Woods Woods Designs

    I am probably the only one on this forum to have sailed both a Thunderbird and also several Aerorigged boats. if you are starting from scratch you would be much better off with a different hull design. The Aerorig has a number of disadvantages, including the fact that its a lot heavier and its difficult to get the rig balance right. As with all rotating masts fitting wind indicators, tricolour masthead lights etc is challenging. You also have to question why it was not a commercial success.

    Richard Woods of Woods Designs
    www.sailingcatamarans.com
     
  4. rob denney
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    rob denney Senior Member

    There is nothing about a Thunderbird (or most other boats) that would make it any more suitable/unsuitable for a ballestron rig than it is for a stayed conventional rig.

    There will be advantages in having the structure looked at, both to ensure the mast support is sufficient and to remove the structure that goes into supporting a stayed rig. The mast heel will need little or none, the deck may need a fore and aft doubler (timber or glass). You should be able to remove any extra material supporting the mainsheet, headsail tracks and winches, chainplates and forestay along with the items themselves. Overall, the boat will be a fair bit lighter and, if you build the mast yourself (no harder than building the rest of the boat), it will be cheaper.

    In my experience (unstayed mast builder and designer for 20+ years) the ballestron mast will not be any heavier than the alloy mast and rigging it replaces. The rig will have a lower cog than the alloy one which will mean less pitching and heeling.

    Getting the balance right is simple. You are not looking for zero mainsheet loads, just much reduced ones, plus no need to trim the headsail or deal with extras. The main reduction is from not having to use the mainsheet to achieve leech tension and mast bending.

    Trivial problems such as the masthead light on a daysailer are far outweighed by the safety that comes with not having a deck sweeping headsail cutting off all vision to leeward and the ease of handling a balanced rig and an unstayed mast.

    Aerorig was the brand name of Carbospar's ballestron rig which was both heavy and expensive. They are no longer in business, although the principals have been heavily involved in mega unstayed rigs for Maltese Falcon and Sailing Yacht A (the Russian 3 masted superyacht).

    Ballestrons are not a commercial success for the same reason unstayed masts aren't. What this is, I have no idea, although designers such as Chris White, John Shuttleworth and others incorrectly denouncing them have not helped. Suffice to say, no one I know who has sailed a cruising boat with an unstayed mast has reverted to a stayed one, so it is probably just a matter of time and critical mass.

    There has been some rubbish written about ballestrons, but their advantages can be summed up by:
    Easy sailing: The sails are always working correctly, whatever point of sail. Maybe it would be better to say the rig works to 95% efficiency all the time. A conventional rig may work to 100% if you're an expert, but only 70% if you're not (ed: or if you are not prepared to trim the sails 100% of the time). A conventional rig needs extra downwind sails, ie spinnakers. The Aerorig doesn't. There are only light loads on the mainsheet and once unrolled there is never a need to adjust the jib sheet. Sailing Catamarans - Balestron or Aerorigs http://www.sailingcatamarans.com/index.php/faqs/19-sailing-and-performance-questions/111-aerorigs
     
  5. Rurudyne
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    Rurudyne Senior Member

    I would suggest one reason for the lack of success that is relevant to a boat of the size in question and which would have a natural consequence as people move to larger boats. I'm sure I've seen this before somewhere even if I can't remember where or who from and I'm just repeating it.

    Boats of the size in question are often meant to be trailerable. The Balestron mast may not be as easy to take down and put up (a small Balestron with a pulpit style folding point should work given modern materials), being more involved than a mast for a junk rig would be.

    Since people's opinions are often shaped by their first love, so to speak, they want more of that. Or less of it I suppose depending on the circumstances of the breakup. Small commercial made or traditional rig boats are how many folks get into sailing and so that logically becomes their comfort zone.
     
  6. misanthropicexplore
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    misanthropicexplore Junior Member

    Well, thank you all for the advice so far.

    Yeah, I should have said Balestron. An Aerorig is a Balestron, but not all Balestrons are Aerorigs, sort of like SUVs and Jeeps.

    I wish I could say I had perfectly logical reason for all this, but it's all feelings. To me there is certain logical "rightness" in a balanced rig on an unstayed mast.. I'll probably put my first on a model, then the next on a PDR, and see how I feel about it.

    The 'Bird is just because well..there's just something lovely about that boat, in a simple, plain way. Something like farmer's daughter, I guess. The first one I make will be in November, and it's going to be cardboard 1:12, then a 1:6 in 1/8" ply and again, see how I feel about it.

    Richard, what did you think of the Thunderbird 26 in general, and why do suggest a different boat when starting from scratch? To me, an older, somewhat heavy, somewhat overbuilt design seemed like a good match for a somewhat heavier rig.
     
  7. misanthropicexplore
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    misanthropicexplore Junior Member

    Unrelated to anything I've said here, can I just say that large trailerable boats scare the crap out of me? I know it's unreasonable and totally born out of a lack of experience, but of I'm out some nasty weather in boat that weighs as much as a small house could it PLEASE not be designed to fold up into a smaller, more buoyant package, because that sounds like a bad time.
     
  8. Rurudyne
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    Rurudyne Senior Member

    My bad, the mast ... not the hull ... folds. That's what I meant to suggest.

    That said, most folding masts I've ever seen were stayed. Not sure how well an unstayed folding mast would work. Maybe, instread of the mast folding the whole footing could pivot around a single point at or just above the deck and clamp down tight at the base when straight up? Put some sort of giant waterproof boot around it like the on a car's stick shift maybe?
     
  9. Richard Woods
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    Richard Woods Woods Designs

    The cockpit was horrible, very un comfortable, boat is quite tender until the big keel starts to work. Lots of room below though, but not sure about big sliding hatch and keeping it watertight in bad weather. I always assume developments improve products over time. You wouldn't buy a 1950's TV or car or washing machine. because newer ones are better. Same with boats

    The key for safe mast raising is keeping it in line, and that essentially mean stays or halyards led to the sides. And of course a deck stepped mast makes it all much, much simpler

    Richard Woods
     
  10. rob denney
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    rob denney Senior Member

    Unstayed masts fold easily as long as the hinge is correctly engineered. If the hinge is above the top of the lowered sail, the lowered section is short and light, there is no need to remove the sail or the boom, fiddle with stay lengths, worry about furlers, rig up booms or spi poles for leverage or risk dropping the mast. No problem to drop it forwards, backwards or sideways if required. There is no winching, hard work or stress. Remove a pin, lower the mast using a block and tackle on the overlapping section, pull it back up and replace the pin. The entire operation takes about as long as it takes to loosen the stays enough to remove the forestay prior to dropping a stayed rig.

    There are not many 20' lwl monos that aren't "tender before the keel starts to work". Not many that fufill the original requirements for a T'Bird either. If those are your requirements, it is a good choice.
     
  11. CT249
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    CT249 Senior Member

    On the other hand, many (perhaps most) sailors put very different rigs on their yachts than those of their first love. Most people start off sailing with unstayed cat sprit rigs (Optimists) or stayed cat rigs (Sabot, etc). Many people who bought yachts during the yachting boom got into sailing in classes like Sunfish, Hobies or windsurfers.

    One thing that makes me wonder about a balestron rig on a T-Bird is that the very full entry means they need a lot of power to get upwind in light airs and a chop. I'm not an aero expert but in those conditions, big genoas seem to provide a lot of lift and are quite hard to stall if trimmed correctly. Whether a balestron rig can develop that sort of lift would be an interesting question.

    I quite enjoyed my Thunderbox sailing time, but for me it was the rig itself that was part of the attraction. The fractional sloop with jumpers is a lovely setup IMHO.
     
  12. rob denney
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    rob denney Senior Member

    Interesting indeed. Are you saying an overlapping genoa is a better light air/choppy upwind rig than an equal area (ie, taller) non overlapping rig?
     
  13. CT249
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    CT249 Senior Member

    Cutting headsail overlap from 150% to 105% in a cruiser/racer mono seems to reduce overall speed by about 1.5 to 2%. Obviously most of that loss is in light upwind conditions, since a short overlap is just as fast in a breeze and downwind most of the time under spinnaker. So the speed advantage of an overlap is very significant and, in such conditions, could well be greater than the speed advantage of a taller rig. There's been a lot of discussion over this since many people have moved to short overlaps to reduce ratings.

    When I have seen side by side comparisons of the same hull with overlapping and non overlapping rigs, the difference has been very significant in light air upwind conditions with chop. That's for a cruiser/racer like a Thunderbird with its very full bow; other boats would be different. Of course, a taller rig has heeling moment issues.
     
  14. Richard Woods
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    Richard Woods Woods Designs

    I agree with CT249, there is lots of data both theory and practice to show masthead big genoas are better in light winds and/or a slop. In strong winds its reversed and of course offwind the big genoa has no benefit if you have a spi, and the smaller-mainsail rig is slower. Using a screecher on a multihull is not just to increase area nor for rating reasons

    RW
     

  15. misanthropicexplore
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    misanthropicexplore Junior Member

    Basically, light winds and chop are a "low, continuous power under alternating light to medium load" problem. So are options in response would either be (1.) "increase the continuous power", (2.) "decrease the load", or (3.) Decrease the alternation, corresponding to:

    (1.) Overlapping genoa.
    (2.) Finer entry with less buoyancy.
    (3.) Heavier boat, holding more momentum in troughs.

    Right?

    There is a balanced sail rig I hadn't heard of called an Autares rig here, on page 22 http://www.nsrsail.eu/wp-content/uploads/2015/11/SAIL_FinalReport_Engineering.pdf It looks like it could be rigged for overlap, if needed.
     
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