Biplane AeroRig Cat?

Discussion in 'Multihulls' started by spidennis, Mar 3, 2012.

  1. spidennis
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    spidennis Chief Sawdust Sweeper

    So I run across this Aero Rig idea and I see this example of something of interest that I might like to explore further and possibly use on my 16 to 18 foot adventure racing beach cat.

    What is the story behind this wind tunnel testing model? Is there a biplane rigged Aero Rig out there?

    Can I somehow adapt this rig to fit my biplane rigged beach cat?
     

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  2. Doug Lord
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    Doug Lord Flight Ready

  3. spidennis
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    spidennis Chief Sawdust Sweeper

    thanks, and that led me to:
    http://www.geocities.ws/jp_br/Prestudy/Cat-Prestudy.html
    though he dropped the idea of the aero rig when carbonspar went under.
    his model is pretty cool,
    and as I understand it RC models like the aero rig.
    I did like that he tried out the asymmetric sail plan,
    as I too had thought of trying it out when I had to reef deep.
    but ..... the trail seems to go cold with his boat.

    though it did led me to freewing masts:
    that too seems like an old site .....
    http://www.freewingmasts.co.uk/
     
  4. Sand crab
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    Sand crab Junior Member

    cruiser

    There was a twin aero-rigged cruiser cat on yachtworld. The cat was probably in the 40' to 50' size. I remember the "booms" as being made of a diagonal braced structure like what radio towers are made of. They were not solid like all the others I've seen. I wondered if this was a homebuilt aero-rig. Of course there was also the Cat2Fold and others with twin windsurfer rigs.
     
  5. dstgean
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    dstgean Senior Member

    Didn't Rafi test the cat2fold idea on a Tornado platform? You might email him for some details. Additionally, the designer of the Harry proas builds versions of the aero rig.

    Dan
     
  6. redreuben
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    redreuben redreuben

    I have a question on Balestron rigs, if the main is forward of the mast and you want to gybe it, do you need like a separate mainsheet for the front end of the boat ?
     
  7. spidennis
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    spidennis Chief Sawdust Sweeper

  8. mydauphin
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    mydauphin Senior Member

    Very interesting, though I believe the horizontal bar, would/should not replace some stays to the hull.
     
  9. Sand crab
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    Sand crab Junior Member

    Huh? What bar in what post?
     
  10. Richard Woods
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    Richard Woods Woods Designs

    To Redrueben

    You are right, the balestron rig is a bit like a semibalanced rudder. You cannot have more than about 20% of total area in front of the pivot.

    That means when you reef the mainsail you first have to roll up the jib otherwise the rig becomes unbalanced.

    The balestrom setup is a lot heavier than a conventional boom. So to put two such rigs on a small boat would probably make it overweight. And on bigger boats you need to work out how to step the mast without a crane

    You can see more comments on the Aerorig on my FAQs page (I have sailed a couple of thousand miles with Aerorigs on three different boats)

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  11. rob denney
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    rob denney Senior Member

    Easily. But unless the mast location is fixed and you need some more sail area forward, it will be a lot easier to sail without the jibs. The ballestron is a great cruising rig, but the advantages diminish as you get smaller. There is also the added weight and the possibility of a snafu if the booms hit each other in grim conditions. On a small weight sensitive go fast boat, I would have a single sail rig, in the windward hull of a proa. Not easy to learn to sail, but once you did, you would be very hard to beat.

    No idea about that wind tunnel test, but the Wolfson Institute did some tests and the aerorig performed very well, as it did in fullscale boat on boat tests run by various yachting magazines.

    Red Reuben,
    If you want to gybe the main (maybe you don't want to accelerate) by letting it round the front of the mast, you need to rig another sheet. Otherwise, just pull it in, gybe and let it run.

    Unstayed masts are finally catching on for multihulls. Apart from a dozen harryproas that use them successfully, we are currently building 6 unstayed, folding wing masts for 3 x 40' biplane cats and a ballestron rig for a 45'ter.

    rob
     
  12. rob denney
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    rob denney Senior Member

    Richard, while your web page FAQ's may be correct for aerorigs (none of which have been built for over 10 years) it is wrong on ballestrons.

    "The disadvantages are the rig is very heavy, leading to more pitching and less load carrying. "

    A ballestron rig is about the same weight as a stayed alloy/ss wire rig once you include all the equipoment the stayed rig requires, such as seagull striker, mainsheet traveller, chainplates, jib tracks and winches. The boom is heavier than a standard boom, but the rig centre of gravity is much lower, so there is less pitching, not more.

    "The minimum "immersion" of mast into cabin is about 1 in 7 ie a 35' high mast needs 5' of bury. Also the cabin has to be wide enough to spread the load. Its usually OK with a conventional bridgedeck cabin (although you may need to add a nacelle). Impossible to fit on an open boat and a bit awkward on a boat with a cuddy like the Savannah."

    We installed a ballestron on Taywun, a Simpson open deck 11m/37' cat about 6 years ago. The 14m/45' mast has 750mm/2'6" bury which is 18:1 bury. Taywun is, as far as I know, sailing well. http://harryproa.com/MASTS/Taywun/Taywun.htm

    "A smaller sail area, especially in light winds and certainly when sailing downwind. That's because the jib is very small (only 20% of the total area) to maintain the correct balance. "

    We have had jibs as big as 40% of the main, which worked. The 20% only applies to pin head mains, which are very rare these days. The one on the 15m/50'ter at http://www.youtube.com/watch?v=8chR6DAFjGA has 33%. It is no more hassle to hoist down wind sails than it is on a stayed rig. However, if neither rig has extras, the ballestron will perform much better as the headsail works from upwind to dead down wind, as well as being much easier to handle.

    "You can't motorsail safely to windward with both sails unfurled. "

    This is a very peculiar statement. Sheet the rig on and it will motorsail upwind with no problem.

    "It is possible to sail an Aerorigged boat backwards. A nice party trick but about as useful as reverse on a motorbike. But I discovered the hard way that the boat could sail backwards in a strong wind when I thought I was motoring forward. After a narrow shave when going under a bridge I always rolled up the jib before motoring. When reefing the jib must be furled first or the rig unbalances"

    Nobody is surprised when a genoa caught aback takes control, why would you be with a balanced rig? Again, sheet it in correctly and it won't be a problem.

    "It's a very expensive rig. "
    A ballestron rig cost is in the same ball park as an alloy mast/ss wires rig, once all the components are included. Rig cost is not just what you pay for it. On a ballestron there is almost nothing to wear out, chafe or corrode, the sail slides can be much lower spec as the main is only ever raised/lowered/reefed pointing head to wind (no stays to get in the way) and the rig does not need to be removed for inspection every year. A ballestron rig can be easily built by any amateur builder who knows how to use a jig saw, string line and vacuum pump. This will be a lot lower cost than an alloy mast.

    "This information is now largely academic as Carbospars have ceased trading, hence Aerorigs are no longer available."

    Academic for the Aerorig, but not for ballestrons generally.

    The main benefits of the ballestron are safety (no deck sweeping genoas blocking 40% of the horizon, automatic depowering in a gust, ability to totally depower and stop the boat on any point of sail), reliability (almost nothing to go wrong) and ease of use (low sheet loads from the balanced rig, no stays to get in the way, easy gybes). Plus, as Richard sasys, they work at 95% efficiency most of the time, whereas a conventional cruising rig will be way lower than this.

    rob
     
  13. spidennis
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    spidennis Chief Sawdust Sweeper

    Rob,
    so what do you think of that windtunnel model I posted? I can see that the aerorig/ballestrons could be quite useful in a biggerboat but on a 16 to 18 foot beach cat like a modified F16 or A class?

    What I'm looking for is exactly what this rig is all about, a balanced rig that's easy to handle with very little lines on the deck to get tangled in. With two sails it could get messy!

    I'm also concerned about quickly setting up the mast and storage. This will be aimed at the Ultimate Florida Challenge, lot's of tricky waterways to get thru, bridges to go under, pilings to get around and thru, narrow river sections, and overgrown everglades backwaters. One of the reasons for the biplane, and there are a bunch of them, is that the rigs don't need to be as tall and large, more in the windsurfing range which being a windsurfer I find handling that gear in the nastiest conditions easy. I have to be able to demast quickly when necessary and stow it compactly, especially on the 40 mile road hike. I'm aiming at no more that a total of 3 feet wide when my boat is folded, maybe a bit less for the portage.

    Rob, I've been to your website, your work is impressive. I haven't seen anyone as active with the aerorig/ballestrom rig as you. I'm glad you found this thread, I believe I'm going to learn plenty from your experience, and whether or not this type of rig is good for my application.

    ..... and is "Aerorig" just a brand name by Carbospar? and should I be now referring to this as the Ballestrom Rig?
     
  14. Sand crab
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    Sand crab Junior Member

    I thought th A rig and B rig are the same. What's the diff?
     

  15. rob denney
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    rob denney Senior Member

     
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