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  #31  
Old 02-14-2008, 05:47 AM
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It's very innovative for 2002. It seems it could get some lift from the bow wave being swallowed by the amas/floats, in a manner similar to the Landau 20 cruiser.

http://www.selectyachts.co.uk/landauhome.asp?ArtID=261

Although the A frame mast may have more drag, the main sail running up the vertical wire luff will not suffer the 30% wind shadow effect of a conventional mast and better performance from the sail area should be the result.

http://www.runningtideyachts.com/

Thanks for showing.

Pericles
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  #32  
Old 02-14-2008, 08:09 AM
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That is an interesting rig, fully self tacking and easily reefed/furled.
The A-frame seems very strong, perhaps could be made lighter in composites???

Would be good to hear from the owner or someone who has sailed it.
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  #33  
Old 02-14-2008, 09:24 AM
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ZA001 A-Frame rig

I just found this rig pretty new from S.Africa.
The full set of pictures are here:
Where have I seen that writing on the sail before?
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Main-less rig-za001-frame-rig.jpg  Main-less rig-za001-front-view.jpg  Main-less rig-za001-under-spi2.jpg  

Main-less rig-za001-under-spi.jpg  Main-less rig-za001-fore-cockpit2.jpg  
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  #34  
Old 02-14-2008, 03:28 PM
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Stefano.

I went looking!

http://www.skywalk.org/

http://parasail.skywalk.org/?set=yes Difficult to access.

http://www.seateach.com/parasail.asp Good video.

It's getting so there is too much choice!!

Pericles
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  #35  
Old 02-14-2008, 11:45 PM
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brian eiland brian eiland is offline
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Garry Hoyt's Manta sailboat

Quote:
Originally Posted by deepsix View Post
Interesting pics of an A frame rig on a narrow tri. It appears to have a rollerfurling self tacking jib and a rollerfurling mainsail on a vertical luff wire, with a boom. I could be mistaken, the pictures are not too clear.
Congradulations Deepsix,
You have just found some photos of Gary Hoyt's Manta sailboat project that I was asking for info about over here:
http://www.boatdesign.net/forums/sho...20&postcount=8
http://www.boatdesign.net/forums/sho...20&postcount=9

Lets see if anyone else comes up with some addition info and photos. I'm still busy in Thailand
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  #36  
Old 02-15-2008, 02:21 AM
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Gary Hoyt's Manta

Brian,

On Serge's site, he lists http://www.multihullbuilder.com/ , so I've sent them an email about your request for more information. It's an interesting site with links to a number of building projects.

PS
Very good projects. A mountain of reading. One example. http://lydiusmarius.blogspot.com/

Good luck,

Pericles

Last edited by Pericles : 02-15-2008 at 02:45 AM. Reason: PS added.
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  #37  
Old 02-15-2008, 09:13 AM
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witcheverway, i see benefits on a Main-less rig, who say's otherwise ?
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  #38  
Old 02-15-2008, 09:14 AM
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wishbone mast V3

Quote:
Brian Said:
I would not want to attach the mainstaysail forestay to a horizontal member as there just would be no way to maintain any tension in it. Likewise keep a tight forestay on the leading Genoa sail would mean hi-loads in the 'backstay' that goes over the aft-jumper. That aft jumper pushes the mast forward at the same location as the staysail forestay attaches. This must be combated by the 'traditional' split-jumpers up forward of the mast.
OK, so lets see if we can come up with a better idea:
  1. A rear set of spreaders (jumpers??) to which the mainstaysail is connected, as you said they tend to bend the masts, so if that load cannot be absorbed easily by the mast, then we could shift the backstays to the side of the masts.
  2. I did not draw the mizzensail, if we cannot use it, than we could shift the topmast aft a little to shift the CE aft.
  3. Two poles at the mast hinge point will transfer the load aft, be used as a lever to lower the mast and one could rig a bimini on them as well as use them to lift the tender.
Even though I am answering to Brian, anybody's comments would be much appreciated.
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  #39  
Old 02-15-2008, 10:54 AM
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Quote:
Originally Posted by Spiv View Post
anybody's comments would be much appreciated.
here is somebody, i drew some dotted lines in your drawing, and here my thoughts:
i like the idea but find the house is in the way keeping that masthead swinging aloft
hinging from the hulls may be stronger and better fitting
when also going with bi sails the masts can be shorter, lichter etc
like the davids must, the bi-masts may be coupled to raise and strike parralel
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  #40  
Old 02-16-2008, 06:02 AM
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waikikin waikikin is offline
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Stefano, thnx for the pm, I reckon the A frame rig has some merit, theres some discussion on multihull.net on a Wharram cat with one too. It's a lot like some "shearlegs" a simple kind of crane a mate & I put on a mooring service lighter so is well proven for dealing with compression loads in that regards. I,m not sure about the aft mast setup, maybe some extra reading on my part will help but the more extreme rake combined with the aft shroud angle will increase compression compared to a slightly raked option I think. Maybe an extra set of sheerlegs kind of like a gaff but kinda triangular intersecting at a cross member of the A will be better for when a "main" or aft staysail is required but the result will be the same once moments are consdered & must be countered with some backstays at the intersection. An extra set too at the lower end will enhance the easy lowering of the main masts. Hope that makes sense but its "late" here & at the wrong end of some refreshment for "clear" analysis. All the best from Jeff.
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  #41  
Old 02-16-2008, 09:24 AM
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Quote:
Yipster said:
i like the idea but find the house is in the way keeping that masthead swinging aloft, hinging from the hulls may be stronger and better fitting
The hull shape and the wheelhouse are just my weird results of having drawn that boat in Word, sorry.
I thought of hinging the masts from the decks, but prefer to have clear decks for easy walking around, also the two posts drawn will be part of the main bulkhead and part of the sides of the house and protrude over the roof just enough to allow the mast to swing forward.
Once lowered, the mast will rest on a cradle on the forebeam only for as long as it is needed to go under the bridges.

Quote:
Waikikin said:
I,m not sure about the aft mast setup, ......... but the more extreme rake combined with the aft shroud angle will increase compression compared to a slightly raked option I think.
You're right, the position and rake of the mast is only going to be dictated by where we want to topmast to be and that is going to be determined by the size and shape of the sails to have a balanced rig.
The only design feature i would stipulate is that the forestays must be parallel to have a good slot effect.
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  #42  
Old 02-16-2008, 09:57 PM
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Mapping of Rig Forces

Quote:
Originally Posted by Spiv View Post
....Even though I am answering to Brian, anybody's comments would be much appreciated.
Sorry Spiv, haven't had time to review your proposal yet, but i will get to it.

Meantime I did post a reply to a few postings on another subject thread I had started:
Sail Loading on the Rig, Rig Loading on the Vessel
http://www.boatdesign.net/forums/showthread.php?t=2293



Hi Spiv,
If you were to go to several postings on this tread including two of mine, # 38 & 45;
http://www.boatdesign.net/forums/sho...9&postcount=45

...you will find my desire to employ the consultancy of this gentleman Chris Mitchell of NZ to help in this mapping of the rig forces in determining the optimum configuration for a particular new rig design. Granted it is more 'stactic oriented' rather than dynamic, but it could be an excellent indicator. If I remember correctly his prices were reasonable, and possibly he is less busy with the American's Cup no longer in NZ. I really liked the fact that some of college studies were based on this very subject of mapping the rig forces.
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  #43  
Old 02-16-2008, 10:07 PM
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Main-Sail-Less

...some encoragement to continue with project. Here is a letter I received last summer, '07


Hi Brian, my name is alan smith...I am looking at an Ian Farrier Design 39 foot trimaran....I have enough sailing experience both in chartering and racing to know that what you have postulated in your article on aftmast propulsion to be exactly what I have been looking for....I am 56 years old and with that comes loss of muscle mass and flexability.

I want to world cruise and my biggest seagoing dilema is the mainsail. As you mentioned the full batten mainsail is a beast. i had considered putting a power wench near the mainsail for aid in lifting it....but when you are at sea and singlehanding...it can be so frightening ...when in the middle of the night
some weather blows up quickly...your thoughts are muddled and you are trying to figure out your best course of survival...ha ha ...even on a rotating mast getting the slides to cooperate, the battens not to get hung up on the jiffy sail lines is no laughing matter.

Recently while on a 41 foot Lagoon cat in Greece we went from 15 knot breeze to over 40 knots in a channel between islands. Now mind you, there were 8 of us board this monster of a boat. It took one steering into the wind, one on the mainsheet traveller, one on the mainsheet rope clutch and wench, two handling the mainsail...clawing like hell to pull the slides down, and one lookout watching the battens didn't get hung up in the jiffy lines...which happened several times...up a little...no, down a little,,,,no damnit...up a little you idiots...and so it went.

With your idea we would have just furled the jenny half way and struck the mizzen and we would have been fine...It is a brilliant idea. Just fricking marvelous brilliant....

Now I have a few questions for you....Sailing downwind....dead downwind....of course a spinnaker is completely out of the question for a singlhander...too bloody much work and nervous work at that..Ian Farrier has a good set up with the screecher on a bow pole...you can wing and wing the main and screecher if you get lucky with course desired and wind direction...but I am interested in what you would recommend for a 3/4 wind or full aft wind?

Is the narrow hull of a trimaran going to present in back stay problems for the forward leaning mast? Does the mizzen need some sort of boom? What percentage decrease in mast height will effect the same capacity of sail area with the 3 sails versus two sails of a bermuda rig....

Thank you Brian....I am hoping that you will take a few minutes to answer my questions...it is so refreshing for me to have found this article....your idea hit home like the truth of god...ha ha ...well, fair winds to you...alan smith
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  #44  
Old 02-17-2008, 02:52 PM
catsketcher catsketcher is offline
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My last word

Hell all,

I hope you won't take this badly but it is always easier to develop something well proven than to totally develop something brand new. If you want to pull the main down on a square run use good slides and no diamonds. Sail downwind most of the time with a screecher and it will furl beautifully and will pull the boat downwind by its nose.

The planform of a large genoa has lots of induced drag due to its triangular shape so along with headstay sag the benefits of having no mast in front of the luff will be nullified. Especially if you can't enjoy the extra roach a main gives you - increasing sail area and planform efficiency.

Many boats that rely on performance to sell - Melges, J boats, skiffs have large mains behind non rotating masts and do well. Even boats with rotating masts and free design rules like the NS14 and 18ft skiffs usually end with 3/4 of the sail area in the main - it has been proven to be the fastest by huge amounts of trial and error.

The large genoa monos of the 70's (S and S, Peterson, Frers) have given way to short overlap blade jibs running larger mains. Mains are easy to tune, keep their shape in a blow, sail fast and make the boat nimble in tacking. If the main was slow then the monos would still have small main rigs but they accept the loss of unmeasured sail area and make mains bigger.

You can make mainsails more manageable and I feel that your energy and talents could be better spent down this road. As stated before a wishbone boom tames a mainsail to a compliant helper and makes the rig cheaper with no traveller and large winches required.

These commments are not designed to inflame or cast aspersions on your desires. Good luck in your endeavours.

cheers

Phil Thompson
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  #45  
Old 02-17-2008, 03:15 PM
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Phil, you've got to be kiddin. If nothing changes (or changed) we would still battle it out in the 1650's baoting rigs.

Maybe in the future we could look back (since some of us will still be around in a few hundered years) and think the same of todays boats than we did compared to the 1650's. Check ?
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