BIPOLAR

Build logs from members building catamarans, trimarans and other multi-hull variants.
Redreuben
Posts: 27
Joined: Sun Dec 18, 2011 11:19 am
Location: Fremantle W.A.

Re: BIPOLAR

Post by Redreuben » Sun Jun 01, 2014 3:21 pm

groper wrote:Why?

The more I look at them the more complicated they seem. They also look extremely expensive once you consider a full size cruising sail for a +40ft cruising cat instead of a toy day sailer...
I'm not suggesting that this is where all cruisers will end up I'm just saying this is the obvious (to me) area of sail development. The variety of different mast and sail plans don't seem to be providing the performance gain potential than a sorted wingsail.
Whilst there are other hardware costs, sail cost increases ought to be minimal in that sails don't need high tech cloths or sail cutting/shaping technology, they are basically dead flat with pockets.
Once a basic working configuration has been worked out simplicating ought to provide some really good alternatives. (I'm hoping).

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Sun Jun 01, 2014 8:42 pm

I dont buy into it... seems a bit of a gimmick thing to me.

If you look at the lift to drag ratio curves, and max Cl, the is next to nothing in it between a rotating wing mast with fully battened sail VS a double skin wing sail.

There is a big difference between a non rotating mast and sail and both of the above tho.

So my point is - all the added complexity and cost of the double wing sails, is not justified by any significant performance gains over and above that of a rotating wing mast.

The story will change once we are looking at multi element wing sails - the americas cup wings are a 2 element wing. Passenger jets utilise 3 and sometimes 4 element wings when full flaps are deployed. Multi elements allow a much higher effective camber and therefore much higher max Cl. There needs to be a gap to allow pressure recovery between the high and low pressure sides otherwise excessive camber will result in trailing edge stall, as the flow becomes turbulent on the lee side at the critical pressure.

Max Cl, (and therefore max camber) is what we want for downwind and broad reaching. Drag coefficient isnt an issue because the drag in this course happens to be a favorable vector to our VMG on a down wind course. Lift to drag ratio is only important when reaching and beating upwind. Best lift to drag always occurs at a Cl below outright Maximum Cl. So on these points of sail, a moderate amount of camber is ideal and can be achieved without multi elements - hence the passenger jets retract flaps for a clean single element wing when operating at high speed cruise - in our case, high apparent wind ie upwind and reaching. Drag is important now because its acting in an unfavorable vector to our desired upwind VMG.

Dont be fooled into thinking a double skin wing is more efficient than a single skin - the most important thing above all is simply that the lee side has a nice continuous curve right to the leading edge. The lee side, or low pressure side, does all the work. Any discontinuity - such as that of the mast to sail junction of a non rotating mast - will cause a separation bubble and turbulent flow thereafter on the lee side, increasing drag and reducing lift, on any point of sail...

mahnamahna
Posts: 580
Joined: Wed Aug 02, 2006 4:48 pm
Location: Gosford NSW

Re: BIPOLAR

Post by mahnamahna » Mon Jun 02, 2014 12:55 am

No disrespect meant groper but I dont have a clue what most of that mumbo jumbo means. I will take your word for it. I will say this though, I have found this all through my build experience. Experts speaking expertese. Frankly, I dont care to learn it. I just want solutions to my real problems and my perceived problems. (And for me, there is no real distinction, perception is reality). If someone is too scared or disinterested to do something because of design but will if that fear or interest limiting factor is designed out, what is the issue with designing it out?

And what informs my thinking now is that I know Michaels boat sailed across WPB with no-one aboard and he was lucky it found land on a soft mud beach and not a rocky coastline. I fear that now, and I fear having a boat with a rig I can never fully depower. Wing masts with no sail up are still powered. I want a boat I can completely depower. And preferably easily.

One solution is a wing mast with a fold down mast. That is the direction Mick in Perth is taking. I am considering it. But the fold down and restore method would need to be easy.

I find the wing sail on a round mast to be a more practical solution to this problem and it happens to come with another big desire in my sailing requirement, ease of handling. It may also allow me to run with a much smaller rig. All big ticks. So far I am yet to see a negative despite your math.

For now I concede, although that may change when I talk to the actual manufacturers, that cost is probably going to be the prohibiting factor. If it turns out, after I do all of the math mentioned in my previous post that it is not, I am likely to take the wing sail rig course. Unless some other limiting factor arrives to dissuade me. I favoured wing masts for many years until what I think for now is an even better option emerged.

I also still like the idea of the bi rig, 2 smaller sails appeals to me more than 1 larger one even though it is more effort to sail, ie having to trim 2 sails. The fact it makes for a safer rig due to lowering the centre of effort appeals to me and I also like redundancy and knowing if one mast or sail is damaged the other can still get me home.

No amount of expertese can sway me from what I want or from what will dissuade me from doing what I want because the negatives cannot be designed out. So although you dont buy it, I think many will because it is simple. The math behind it may not be, but the real world application of it seems very simple. We dont need to know how it works, just that it does, any more than we need to be mechanical to drive our cars.

I wonder why Benetau are going to the bother, why dont they just develop a wing mast and sail as you suggest? They may yet abandon the wing sail idea and do just that, but for now, they seem to think this idea has some currency. They claim one of their motivations is to encourage a new generation of otherwise disinterested sailors, disinterested because of the perceived complications of sailing. All of their crews dont feel intimidated by sailing but they are dealing with the perceptions of real customers, who are not interested in learning the complexities of sailing. They are spending a lot of time and effort on something not worth doing according to the max ci, drag coefficients and vectors wouldnt you say?

Anyway, my layperson mind just likes the look of this new solution to old problems.

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Mon Jun 02, 2014 6:57 am

Many sailers can, and do, put rotating masts on their yachts, I'm sure there are plenty of beneteu s out there among them, so what's your point? The fact they are playing with this stuff means little other than they see the possibility of making some money from it, they are in th business of making money above all else.

The large rotating masts like Michaels are a problem, there is too much windage up there for my liking also. Fine for racing yachts but would have to be a concern when long distance cruising and being caught in bad weather. They say if the masts are toed in there's no problem, but having no experience with it myself I'd rather let Michael comment on that.

One thing your forgetting mm, is that whilst these wing rigs may be simple to operate once aloft, they are more complicated mechanically. So what do you do when something breaks or jams in th middle of nowhere in a storm? You probably can't fix it on the spot , and access to anything inside is impossible without destroying th sail. A simple thing could ruin your trip permanently.

It's clear you have no interest in performance and also rather nervous, so for you going with round masts is probably the way to go. Why not consider twin aero rigs like on he be ge bes boat - cactus island? Or forget the headsails on fore booms and just have the 2 mains on short sticks? Cheap, simple, just a bit slower...

michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Mon Jun 02, 2014 9:30 am

Image

The issue of sailing around the mooring or anchor is now a non issue for us. The incident of dragging the mooring was in a large part due to it being a for and aft mooring not allowing the boat to swing into the wind, partly due to us not realising the masts had to be set to counteract each other, and also due to the wings being way too big. I'm still often struck by how stumpy the wings look now, or conversely how tall the were. I think the wings set opposing has a strong stabilizing effect at anchor, the boat wanders about almost not at all on the mooring, unlike other boats around us. To my mind it is like the dihedral effect on a aircraft.

We have just yesterday completed a trip from melbourne to Tweed River 1100nm. Non stop except for a one day stop in Sydney
We had the full range of sailing conditions from a rugged night time rounding of Wilson's Promontory in 35kt wind, a Wild 15kt and up to 20kt sleigh ride through the Bass strait oil fields also at night, a fantastic day long close reach at 10kts under autopilot and flat seas, and quite a few hours of motoring. The rig was great allowing the booms to be sheeted out wide downwind with no spreaders or rigging to worry about.
The only problem we had was gybing at night. We massed up a couple of gybes in the dark mainly due to not having wind direction indication with winds from behind. The forward mounted wind sensor doesn't show following winds well, which I already knew but I hadn't realised the implications for night time gybes. I will mount an additional sensor at the rear and switch them as required.
The boat was easy to handle in strong winds with the sails very deeply reefed giving little loads on the sheets, all the forces taken by the wings
Which are massively strong especially because they were designed to be 25% longer than they now are and for a bigger sail area.

Learnt a few things over the trip. We need a lot more dc power generation, having 400watts solar. We used lots of power with the autopilot going virtually non stop for days at a time, constantly charging electronic devices etc. May be the stronger Queensland sun will alleviate the shortfall .

The biggest lessen was to never, ever ever let the toilet block up. We had a newby join the boat in Sydney and despite serious warnings about the use of boat toilets proceeded to clog up the forward toilet at the first attempt. Luckily for me he was persuaded to take on the job of unclogging which involved dismantling the toilet with me offering support from a safe distance from outside the hatch above. Also luckily the toilet compartments drain into the shower sumps so the whole area could be hosed out when finished.



End of trip so far sailing across a benign Tweed river entrance


mahnamahna
Posts: 580
Joined: Wed Aug 02, 2006 4:48 pm
Location: Gosford NSW

Re: BIPOLAR

Post by mahnamahna » Mon Jun 02, 2014 2:45 pm

Groper I totally agree that benetau are only interested in developing the rig because they think they can make money from it, but that is really my point, they see a market for it. In other words, they think they can sell enough of them to justify the development costs, royalty payments to the inventors etc. They see enough buyers for the rig to make it worth developing.

According to their own press releases, their consultations with sailing clubs is telling them that young people are not entering the sport in anywhere near the replacement rate of baby boomers leaving it, and this leads them to believe the market for their product is diminishing. Their research has indicated that people find sailing too complicated. Just take a look at your average boat, there are ropes leading off everywhere. I am somewhat interested and I am daunted by them all. So simplifying the rig is a big priority to attract otherwise disinterested people.

But at the same time, the rig has to perform to a reasonable level. Wouldnt you agree that the wing sail seems to do that?

As for complexity of internals of the rig, take a look at this pic. Does it look complicated to you? I know there are some very complicated versions out there, not least the first one I posted about, but this one and the home made junk rig one on a link posted earlier seem very simple, as does benetaus although not as simple looking as this. Of course things can and usually do break, but sail cars jam, furlers refuse to furl, sheets and halyards jam, etc etc. All this seems to be is a series of ring bearings that rotate around the mast and join to the 2 sets of battens that keep the sails apart and give it its shape. There is a lever that adjusts the camber from one side to the other and that is about it. It is pretty simple wouldnt you agree?

I have initiated discussions with onesails and will report what I find. My initial impression is that it is very early in the development process and it could be some time before they are ready to release to market. My build has seriously stalled as many of you know, but is slowly progressing, sometimes I feel I am getting there others not so much. Who knows, maybe I get a rattle on and end up with the same rig as Michael, or I continue this snail pace and all of these wings become viable options in the meantime.

One way or another I will keep you informed. Its all good.

So glad to hear from you Michael, please give us more info when you can. What was the issue with the Jibes? Did you just stall or was there damage etc.

I wish I had known you were in town, would have been great to video you coming through Sydney heads!
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he b gb
Posts: 34
Joined: Wed Mar 20, 2013 11:05 am

Re: BIPOLAR

Post by he b gb » Tue Jun 03, 2014 9:42 am

Hi Michael,welcome to Qld(well almost there!).Glad to see that you're out there doing it after the years of hard labour.It sounds like you are heading north,I'd be stoked if you called into the Elliott river on you're way so I can check out that boat of yours.It's a nice spot to visit with an easy entrance and is only a days sail from the reef. Just send me an email(gbarrink@hotmail.com)and I can give you any info you might need and anything else you might like to know about other spots up this way. Hi Mahnamahna, Sounds like your boat is getting close to splash down time.All my boats that I've built I have launched with basic fitouts, then got sailing first and adding sections of fitout as time goes by. It's actually quite nice having different newly added luxuries each time we go for a cruise. If I was in your position regarding rigs I would go down the path of soft wing on non tapered fixed tube like you have been describing. By sticking to bi rigs (you were mentioning one central rig?) the engineering and construction become much easier. Two small rigs are definately much easier to sail than one large rig,and much safer also. Cheers Gerald.

44c
Posts: 1148
Joined: Tue Aug 08, 2006 5:08 am
Location: Hervey Bay, Qld

Re: BIPOLAR

Post by 44c » Wed Jun 04, 2014 6:48 am

Damn, looks like you've capsized it already! Bloody catamarans. It gets better with practise. We're down to a couple of hundred capsizes a day now. Hardly even notice them.

With a bit of luck we might catch up in Moreton bay?

Smooth Cruiser
Posts: 583
Joined: Thu May 11, 2006 1:51 am
Location: Brisbane

Re: BIPOLAR

Post by Smooth Cruiser » Wed Jun 04, 2014 9:58 am

Good to see you up this way Michael - if you are in Moreton Bay at all and need a hand with anything let me know by PM. I can run you round by car or whatever in return for a good look over your boat!

For the night time gybe issues - do you fly a flag at all off the stern or side rail? I find this to be a great visual aid for where the wind is and often sail to the flag when running DDW or goose winged rather than sail to the wind instruments - which I can't always see clearly at night and are complicated by the fact that I have a rotating mast. Just a thought - sometimes old school can be just as good as more instruments!

Hope your trip continues to be enjoyable.

michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Wed Jun 04, 2014 8:36 pm

Thanks for the kind offers, guys. We will be leaving the boat here at the Gold Coast and returning to melbourne and coming back up in July . . Unfortunately we can only get away for a week or two at a time so it means
coming up for some short cruises before having a more leisurely cruise back south than we had on the way up.
It would be good to catch up with other forum members at some stage.

We did try using some streamers from a fishing rod off the stern for wind indication, it was a help but only up to a point, the cockpit roof got in the way, so more thought needed on that one.

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