CNC Plans not Included

Lots of examples both ways. A cats are faster with main only, some dinghies are faster with jibs, probably due to righting moment issues.. The difference between these and cruising cats is the cats can reef. Adding extra sail at the top of the mast will result in faster sailing than adding it at the deck.

We have built several of these (ballestrons). They work well. Launched Boats – Page 2 – Harryproa http://harryproa.com/?paged=2&cat=17

Monos have big overlapping jibs in light air because they cannot get sail area up high. Few cruisers enjoy grinding them in, hoisting and lowering them.
The real performance benefit of an unstayed mast is at night and in unsettled conditions. Most cruisers shorten sail because they are scared of being hit by a squall and having to reduce sail, usually while running square with the main pinned against the shrouds. On an unstayed rig, you dump the sheet and the boat drifts until you pull it back on. No flogging headsails, no spinnakers to douse, no mainsail to reef and no need to get the crew out of bed. When the squall passes, sheet on again. If it doesn't, take in a leisurely reef with the boom pointing dead down wind, regardless of the boats heading.
The other advantage is the cost. Not so much the cost of construction, which will be similar to, if not cheaper than a stayed rig, but that there is nothing to maintain, no need to pull the rig every year to check for cracks etc, no need to go up it before every major voyage and no need to replace the rigging every x years. You step an unstayed mast and forget about it until it needs repainting.

A better question is to ask the doubters if they have ever sailed on one. If you look at forum posts and magazine articles on unstayed rigs and remove those from people who have never sailed one , the overwhelming opinion is that they are pretty good. I know quite a few owners of unstayed masts, they all love them. I also know quite a few owners of stayed masts. They have the problems stayed masts overcome, but are prepared to live with them. Similar to mono and cat owners.

Anther option (and some more terms to look up) for an extension is a gunter rig, a section of mast on a track which is hoisted with the top of the sail attached. Kind of an external telescoping rig.
If you use a wishbone boom, you will not need a traveller, or any mainsheet purchase to keep the leech tight. Wishbones are as much a no brainer in the effort and cost departments as unstayed masts. Be aware that Groper is right about resale value of boats which are different. This becomes an (un)virtuous circle. ie they are not bought because they have poor resale value.

I disagree with Shuttleworth (I have not read the article) about a truss being the best way to support an unstayed mast. As Groper said, all the loads are lateral. Consequently, they only need spreading out into the surrounding boat. The bridgedeck for the bottom bearing and the roof for the top one. Obviously, where these attach to the hulls need to be substantial, but that is not usually an issue. If a truss is required, it should be in all directions as the sail load is rarely directly sideways. Mounting the mast in a nacelle extends the distance between the bearings. The nacelle has to be strong enough to support this, but that is not hard to do. An advantage of mounting the mast on or through the bridgedeck is the halyards can be lead aft. Otherwise, they have to be cleated on the mast so they do not restrict rotation.
A truss is a good shape for a cross beam to hold the hulls together as long as there is a bear beam as well to stop the hulls twisting. this might be what Shuttleworth was referring to.

Definitely talk to designers and engineers, but do not take anything they say as gospel unless they can support it with experience and/or explainable numbers.

 

ROB- dont doubt the twin unstayed wing mast rig - i think its great and almost put it on my other boat. What stopped me was the price tag- nothing more...

I ended up getting a brand new bermudan alum mast rig with dynex fiber stays and diamonds, COMPLETE with boom, halyards, electrical etc Including labour and crame hire fitted on the boat no work for me to do, for $18k- that was on the oram 39C cat. 14.5m mast.

Thats the difference... and the free market forces have spoken on this for years... but hey, if you want to be different and your happy to pay (or build) then go for it i say

 

I'd be happy with a single unstayed mast. With a small nacelle I can get about 9 foot between bearings. The roof can be supported across the beam pretty easy but forward and back, I don't want diagonal supports so that is the challenge. I have high hopes for the column which can be ultra thick cored carbon.

I added bracing in the front as well, the engineers have to see if it's sufficient, this is far as I can go at this time with design. I am going to start checking watermakers, ac units, toilet systems etc...

 

see, so now your back to a full structural roof - you have no choice in that if you wish to have windows to the forward part of the bridgedeck. So now you have to build all that complication cost and weight! AND the sail plan is still too far aft- you need to get the sail plan more longitudunally centered on the hulls.

My suggestion - forget anymore renders on this, ditch the single unstayed mast idea and call Etamax (or rob denny) about the twin unstayed wing masts - they already have the tooling for these 15m wings, bearings and stubs as they produced them for the boat i showed earlier, along with 2 other sister ships. Your dollar is worth 25% more here also. Then you can have a much bigger solar array on your roof, with less shading from the boom and omitted panels for the walkway on your roof, and the roof doesnt need to be UBER strong to take an unstayed mast so its quick and easy to build

Then the deck and hull reinforcement to take the twin masts is very simple and easy and easily accomodated within your 60ft hulls and youve saved a heap of money in custom engineering, and building an enormous roof structure - that top bearing is where it all happens, were talking large numbers of metric tonnes of lateral forces here.

Im not sure if etamax could increase the length of the 15m masts theyve already designed without significant extra tooling - youd have to ask - but what OZONE or BIPOLAR found was that masts equal to length of boat were sufficient - thats why he cut off the top 3m of his masts as he felt 15m was too much for his 12m boat. The rotating wingmast and sail is a very efficient and powerful sail plan. They would probably fit straight on your 18m boat and you would have enough power with a slightly longer boom and higher roach square top sail. No engineering required as its already been done... You have the choice of fabricating yourself - or simply ordering it from Etamax finished ready to bolt on. Now all your rigging problems have evaporated.

 

Twin unstayed wing masts. Seems perfect for charter and party types. All the action is on the deck which now is free and clear. No fore sails to mess with. Wing on wing downwind gybe-free. Certainly would make the boat stand out in the Med.

 

Yep

 

hmmm very good points ... My mast is centered right now, if I use twins, about where would they be located forward of the center point?

I think you might be right, I'm ruining the look and weight of my boat with all this heavy construction!

... also, why are they located forward of center, don't they push the bow down as well?

 

I will email Rob and get an estimate from him, might be easier to have them build it if they already have the tooling.

 

Groper, what do think about assigning 10% sail area to the wing masts?

 

The center of the sail area should be roughly center of the boat. This means the mast is roughly 50% of the sail chord fwd of midship.

UOS- im suggesting that the mast area should be what its already designed by etamax- it saves money in that theybe already engineered and tooled for it vs a new custom design.

You have to save money whereever you can in something like this otherwise it gets real expensive real quick...

 

effective luff length 14m, boom 4m, square top, as there are no back stays full roach.
(15m2 from the mast + 56m2 main sail) x 2 = 142m2 (approx) - a lot more area in the masts than 10%
light weight & fine hulls so should be fast.
much safer in the adiabatic winds common in the Med.

 

That would be 1528 sq feet which should work, maybe masts need to be a bit taller for extra thrill, I will see what he says about tooling on that.

pipe is the centerline ... my forward bath will have to be sized down just a bit, this could work!!!

 

Design wise its most efficient to have the masts in line with a transverse beam

 

That render shows them a bit too far fwd. Remeber its the center of the total area not jist the sail foot. As the sail tapers upward so the area center moves fwd. The center ends up being about 33% of the sail foot.

 

Okay so I will move them back even with the curved part of the bridgedeck and the bath will have to be relocated or people can walk around mast to get to it.

Now that is a solar roof, imagine that at anchor!