First hand experience for an unconventional rig

Laurent

Super Anarchist
2,264
1,880
Houston
I am looking for first hand experience on rigs that would be similar to the unconventional option detailed below. Does it work well? What are the weaknesses?

First of all, this is for an unconventional new boat, designed by a real naval architect (not me, even if I provide input, of course).

I plan to have a schooner rig with 2 unstayed, rotating carbon fiber masts. For reasons I do not want to detail here, I really would like to decouple the control of the sail twist from the main sheet. I will not be able to have a long main sheet traveler that allows to move the location of the pull down force of the main sheet. The main sheet will pull almost horizontally. So the needed down force on the clew to control the twist has to be generated differently.

I see only 2 options:

- a super-duper vang

Or...

Rrrrrrrrr (drum roll)

 - a wishbone rig...  

Before we go any further, yes, I have seen the Front Page (what's that?) article on the Stephen Warings design. But as far as I know, it is still only vaporware...

Some dimensions:

- each mast I dimension is about 12 m (40ft)

 - the P dimension is just shy of that, around 11.5m (38ft)

 - the E dimension is just shy of 4.5m (just shy of 15 ft)

 - each main sail is fully batten, fat head of 30 sq. m area (320 sq. ft.)

For reference, the maximum righting moment is about 3.4 T.m (24,600 ft.lbs)

I know that there are out there large(ish) sail boats with unstayed wishbone rigs, like the wally cat (spelling?) or the Freedom series.

But all the ones I have seen on the Internet have no fat head, very large E dimensions and are not fully battened mainsails. I suspect (maybe wrongly) that the necessary leech tension to control twist is much less than for the rig I am considering.

So a wishbone arrangement is fine to control the twist on an older sail design but not adequate for a longer span, fully battened, fat head mainsail...

Am I wrong? Am I right?

Do you know of any design which would have a modern sail dimensions/shape, and still use a wishbone successfully?

In advance, thank you for any insightful input!!!
 
 

bpw

Member
455
20
Those aren't very big sails, so a pretty normal vang should be able to handle the loads unless the boom is really low or something. 

Rail vangs are a bit of hassle, but can also work well when you don't have a traveller.

I've seen rigs like that with a gnav too, can't remember the boat though.

 

harryproa

Anarchist
861
109
I am looking for first hand experience on rigs that would be similar to the unconventional option detailed below. Does it work well? What are the weaknesses?

First of all, this is for an unconventional new boat, designed by a real naval architect (not me, even if I provide input, of course).

I plan to have a schooner rig with 2 unstayed, rotating carbon fiber masts. For reasons I do not want to detail here, I really would like to decouple the control of the sail twist from the main sheet. I will not be able to have a long main sheet traveler that allows to move the location of the pull down force of the main sheet. The main sheet will pull almost horizontally. So the needed down force on the clew to control the twist has to be generated differently.

I see only 2 options:

- a super-duper vang

Or...

Rrrrrrrrr (drum roll)

 - a wishbone rig...  

Before we go any further, yes, I have seen the Front Page (what's that?) article on the Stephen Warings design. But as far as I know, it is still only vaporware...

Some dimensions:

- each mast I dimension is about 12 m (40ft)

 - the P dimension is just shy of that, around 11.5m (38ft)

 - the E dimension is just shy of 4.5m (just shy of 15 ft)

 - each main sail is fully batten, fat head of 30 sq. m area (320 sq. ft.)

For reference, the maximum righting moment is about 3.4 T.m (24,600 ft.lbs)

I know that there are out there large(ish) sail boats with unstayed wishbone rigs, like the wally cat (spelling?) or the Freedom series.

But all the ones I have seen on the Internet have no fat head, very large E dimensions and are not fully battened mainsails. I suspect (maybe wrongly) that the necessary leech tension to control twist is much less than for the rig I am considering.

So a wishbone arrangement is fine to control the twist on an older sail design but not adequate for a longer span, fully battened, fat head mainsail...

Am I wrong? Am I right?

Do you know of any design which would have a modern sail dimensions/shape, and still use a wishbone successfully?

In advance, thank you for any insightful input!!!
 
Laurent,

What you have described is standard on the latest Harryproas.  The sail dimensions are close to the EX40, but you have half the righting moment. 

The success of the wishbone at stopping twist depends on how much purchase you can use for leech tension.  For this reason, we prefer an end of boom vang rather than a snotter like the Wylie cats.  And a seperate (though rarely adjusted) boom outhaul with a horizontal boom.  This also makes better storage for the lowered sail 

Once the mast starts to bend, the benefit from increasing leech tension diminishes.  The mast should be either a) engineered and optimally built or built with the expectation that you will be adding laminate.  The bigger the mast diameter, the stiffer/lighter/draggier it is.  

Low aspect ratio rigs like yours are easier to control, but not as efficient as high AR.  This is mostly noticable upwind in a schooner.

A decision is whether to have the sail rotate independantly of the mast or not:  

If it doesn't and you want to get the best value from the rig (especially the ability to let it weathercock in front of the mast), the halyard, vang, boom, cunningham and probably the sail track/attachment should rotate and all cleats, winches etc are on the mast.  

If it does, you need some decent bearings and some means to rotate the mast apart from the mainsheet. 

When unstayed masts bend, the distance between fixed points for the halyard gets shorter, luff tension reduces and the sail twists.     Reefed, the aft pulling halyard loads will probably pull the sail out of the track at the head of the sail. Harryproa plans include a simple, idiot proof, built from scrap reefable halyard lock to avoid both of these. 

There are several other issues to resolve, but the above will get you started.     ;-)    Harryproas have been using unstayed masts and fixed or wishbone booms for 20+ years.   They make sailing so simple and safe that they are a no brainer for a cruiser, especially a multihull.  They are also easy to build, using the same techniques utilised for the rest of the boat.

An interesting design loop, starting with unstayed rigs:    Once you start thinking about them, different options appear.  Wing masts (scary in a blow), wishbone (big masts for minimum bend) junk (inefficient) are the common ones.     If mast stiffness is important, you quickly arrive at a wing rig which encloses a large diameter mast.  Wings also mean low sheet, vang and outhaul loads.     On most boats, leaving the wing up is not viable, so it needs to be lowerable and reefable.  This implies a flexible leading edge, which dimples in a blow, destroying the shape.     A solution is to make it telescoping, with rigid leading edge.  A large diameter round mast is a lot of windage, so making that telescope as well is a good idea.      This loop lead to the rig we are using on the 24m/80', 3,000 kgs/3 ton cargo proa to service remote villages in the Pacific and elsewhere.  Follow the build and design progress on http://harryproa.com/?p=3788

Rob

 

Laurent

Super Anarchist
2,264
1,880
Houston
From Freedom experience  pointing ability is limited by spar stiffness.  Reaching and running they are fast and efficient  
Tom, thanks for your input.

From your experience, is the limited pointing ability due to the rig being too bendy? Or the sail too full in the first place (and not able to flatten it)? Or maybe a combination of both?

 

Laurent

Super Anarchist
2,264
1,880
Houston
Those aren't very big sails, so a pretty normal vang should be able to handle the loads unless the boom is really low or something. 

Rail vangs are a bit of hassle, but can also work well when you don't have a traveller.

I've seen rigs like that with a gnav too, can't remember the boat though.
The plan is to have the boom really low, indeed. The ratio of boom length to height above deck is around 9:1... So either a very obtuse angle for the vang, and a lot of compression on the boom, or a very long lever between the clew attachment point and the vang attachment on the boom and a lot of bending load on the boom...

I have not found commercially available gnav for this size of sail. I believe Selden has one, but for smaller rigs, from what I recall. I also found someone who had installed a gnav on an unstayed mast, but for a much bigger rig. The gnav was 2 struts, one on each side of the sail, and they were actually hydraulic cylinders to push the boom down. It seems to work really well, but I feel it is too much of a system for me.

 

Laurent

Super Anarchist
2,264
1,880
Houston
Laurent,

What you have described is standard on the latest Harryproas.  The sail dimensions are close to the EX40, but you have half the righting moment. 

The success of the wishbone at stopping twist depends on how much purchase you can use for leech tension.  For this reason, we prefer an end of boom vang rather than a snotter like the Wylie cats.  And a seperate (though rarely adjusted) boom outhaul with a horizontal boom.  This also makes better storage for the lowered sail 
I am not sure I understand what you mean with "end of boom vang". Do you mean a purchase, going from the aft end of the wishbone, to the foot of the mast? If this is it, then if the wishbone is horizontal, once again, this is an almost horizontal pull, to exert a vertical "pull down" force on the aft end of the wishbone; which means that you have to pull many more times than the exerted vertical force. One way to mitigate that it to angle the wishbone with a front end much higher than the aft end, but with added windage, as you have noted.

Did I understand rightly what you meant?

I do not understand the separate boom outhaul with a horizontal boom. Is it on top of the wishbone? or in replacement of the wishbone? It does not show up on the 3D renderings you linked.

Once the mast starts to bend, the benefit from increasing leech tension diminishes.  The mast should be either a) engineered and optimally built or built with the expectation that you will be adding laminate.  The bigger the mast diameter, the stiffer/lighter/draggier it is.  

Low aspect ratio rigs like yours are easier to control, but not as efficient as high AR.  This is mostly noticable upwind in a schooner.

A decision is whether to have the sail rotate independantly of the mast or not:  

If it doesn't and you want to get the best value from the rig (especially the ability to let it weathercock in front of the mast), the halyard, vang, boom, cunningham and probably the sail track/attachment should rotate and all cleats, winches etc are on the mast.  

If it does, you need some decent bearings and some means to rotate the mast apart from the mainsheet. 
Understood on the compromise to be found on the mast characteristics.

I am considering to have the mast and sail to rotate independently. It is not fully finalized yet.

When unstayed masts bend, the distance between fixed points for the halyard gets shorter, luff tension reduces and the sail twists.
True, but only if you run external halyards. Right? If you run internal halyards, they follow the bend of the mast, and therefore the variation of length should be minimal. Correct?

Reefed, the aft pulling halyard loads will probably pull the sail out of the track at the head of the sail. Harryproa plans include a simple, idiot proof, built from scrap reefable halyard lock to avoid both of these. 
I do not understand why once reefed, the halyard is pulling the top of the sail aft... I am interested to see you reefable halyard lock, if you are willing to share; I would understand if you are not...

There are several other issues to resolve, but the above will get you started.     ;-)    Harryproas have been using unstayed masts and fixed or wishbone booms for 20+ years.   They make sailing so simple and safe that they are a no brainer for a cruiser, especially a multihull.  They are also easy to build, using the same techniques utilised for the rest of the boat.

An interesting design loop, starting with unstayed rigs:    Once you start thinking about them, different options appear.  Wing masts (scary in a blow), wishbone (big masts for minimum bend) junk (inefficient) are the common ones.     If mast stiffness is important, you quickly arrive at a wing rig which encloses a large diameter mast.  Wings also mean low sheet, vang and outhaul loads.     On most boats, leaving the wing up is not viable, so it needs to be lowerable and reefable.  This implies a flexible leading edge, which dimples in a blow, destroying the shape.     A solution is to make it telescoping, with rigid leading edge.  A large diameter round mast is a lot of windage, so making that telescope as well is a good idea.      This loop lead to the rig we are using on the 24m/80', 3,000 kgs/3 ton cargo proa to service remote villages in the Pacific and elsewhere.  Follow the build and design progress on http://harryproa.com/?p=3788

Rob
I know that you have been working on the telescoping mast and wingsail for some time. I hope it works, but it is a lot of complication, moving parts, close tolerances, etc to consider for my project.

Thanks for the input. Also, I would like to see some wishbone rigs, like the 3D rendering of the EX40 "in the flesh", actual sailing rigs. Has any of the sailing Harryproas been equipped with such a rig?

 

boots

New member
5
0
Sydney AU
If you want professional advice in relation to mast bend in a wishbone rig to suit a boat with a known righting moment contact Composite Engineering in Boston - composite-eng.com.

We have a wishbone rig from them … and it works.

 

10thTonner

Hazard to Navigation
1,519
530
South of Spandau
You could rig the vang to a semi-circular track on the deck like the Starboats do it, but I don’t know if that is scalable to the size of your rig. 

 

harryproa

Anarchist
861
109
I am not sure I understand what you mean with "end of boom vang". Do you mean a purchase, going from the aft end of the wishbone, to the foot of the mast? If this is it, then if the wishbone is horizontal, once again, this is an almost horizontal pull, to exert a vertical "pull down" force on the aft end of the wishbone; which means that you have to pull many more times than the exerted vertical force. One way to mitigate that it to angle the wishbone with a front end much higher than the aft end, but with added windage, as you have noted.

Did I understand rightly what you meant?
More or less.  The boom can be higher with a curved foot on the sail.  The loss of sail area is minimal.  Or a diagonal batten like the A class if you are serious about the end plate effect.   Diagonal works, but as the vang is tightened, the foot will need adjusting, and the air flow over the bottom of the sail is disrupted, making it pretty ineffective.

I do not understand the separate boom outhaul with a horizontal boom. Is it on top of the wishbone? or in replacement of the wishbone? It does not show up on the 3D renderings you linked.
On top/inside/under.  It adjusts the tension of the foot of the sail relative to the boom.

True, but only if you run external halyards. Right? If you run internal halyards, they follow the bend of the mast, and therefore the variation of length should be minimal. Correct?
No.  Bend the mast, the halyard will go slack and the leech open up.  Tension the leech, straighten the mast and it will hook to windward.  Worse with an unrestrained external halyard, but still happens if it goes through retainers on the front of the mast.  My explanation may not be correct, but it definitely occurs, markedly more wjhen reefed..   

Internal halyards will wear against the mast.  Almost certainly not an issue until 3 am on a wet night.

I do not understand why once reefed, the halyard is pulling the top of the sail aft... I am interested to see you reefable halyard lock, if you are willing to share; I would understand if you are not...

I know that you have been working on the telescoping mast and wingsail for some time. I hope it works, but it is a lot of complication, moving parts, close tolerances, etc to consider for my project.

Thanks for the input. Also, I would like to see some wishbone rigs, like the 3D rendering of the EX40 "in the flesh", actual sailing rigs. Has any of the sailing Harryproas been equipped with such a rig?
The top of the bent mast is further aft than the top of the sail.  It pulls against the track. The lock is only available with the plans.  

I was not suggesting a wing rig, not even sure it is right for the cargo proa yet.

The renderings are all out of date or deliberately simplified.  A couple are/were sailing, but I don't have pictures or videos.  Not sure I would post them if I did.  Too often, things like this are copied, badly.  When they don't work I get the flak.  

The Wylie boats are brilliant, the masts a work of art, but expensive.

boots,

Thanks for the supplier info.  What size rig and how much did it cost, and weigh?  Is it in bearings, or fixed?

 

Tom O'Keefe

Super Anarchist
Tom, thanks for your input.

From your experience, is the limited pointing ability due to the rig being too bendy? Or the sail too full in the first place (and not able to flatten it)? Or maybe a combination of both?
On the Freedom and the Sparrow Hawk I sailed on it was mast bend. Now, having sailed on a TP52 and IRC 51 the shroud and stay tensions involved in getting their close pointing abilities, I understand why the unstayed spars would need phenomenal stiffness to get close to the numbers modern stayed masts can achieve. 

Our MacGregor 65 has never had great ability to go to weather. We could only put 1.8 tons of backstay tension before  boat started bending. The new carbonfiber stayed rigs are putting 8 to 9 tons of running backstay on when fully wicked up.

On catamarans we used vertical end boom mainsheets on semicircular travelers to get leech tension. But, there's a lot more beam to accommodate that. On 12 meters we used to do the same with vertical vangs.

 

nota

Anarchist
I have a kat ketch mono hull two stick free standing rotating alloy tapered round masts with wishbone booms likely intended to be flag poles on a 22 ft water line C/B inspired by a presto

two odd ideas used on my boat are the sails are screwed to the masts with a alloy strip used spread the loads at the mast

and reefing is by rolling up the sail on the masts so no battens so no way to add upper sail area like the modern fat head

so has anyone seen a gaff shaped sail using a upper wish bone to allow roll up reefing and extra upper sail area ?

why an upper gaff like wish bone to control twist by extra lines

one idea is the bit that is in-front of the mast is used to limited the position of the rear end or a direct line from the rear of the upper boom is run to the mizzen top to control twist yes this is for lite air under 10knot winds NOT a off shore  rig

 

Laurent

Super Anarchist
2,264
1,880
Houston
If you want professional advice in relation to mast bend in a wishbone rig to suit a boat with a known righting moment contact Composite Engineering in Boston - composite-eng.com.

We have a wishbone rig from them … and it works.
Boots, I sent you a Private Message.

 
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harryproa

Anarchist
861
109
On the Freedom and the Sparrow Hawk I sailed on it was mast bend. Now, having sailed on a TP52 and IRC 51 the shroud and stay tensions involved in getting their close pointing abilities, I understand why the unstayed spars would need phenomenal stiffness to get close to the numbers modern stayed masts can achieve. 

Our MacGregor 65 has never had great ability to go to weather. We could only put 1.8 tons of backstay tension before  boat started bending. The new carbonfiber stayed rigs are putting 8 to 9 tons of running backstay on when fully wicked up.

On catamarans we used vertical end boom mainsheets on semicircular travelers to get leech tension. But, there's a lot more beam to accommodate that. On 12 meters we used to do the same with vertical vangs.
Interesting.  Thanks. If the Freedom and Sparrow Hawk had similar foils, crew, preparation, weight reduction, etc as the TP52, and the time and money spent on developing the TP 52's rigs had been spent on unstayed rigs, do you think the results would/could be similar?  

Nota,

The Indo rig has a roll up sail with a gaff.  

A sheet on a gaff boom solves the twist problem at the top of the sail, but not for the rest of it.  See the pics of Rainbow Warrior sailing on the web page.   An improvement for sure, but not ideal.  Whether the weight and complexity justifies the extra area is a moot point.  

 
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