Nationals

[Jon (Guest)]

May I wish good luck to everybody taking part in th champs~ But . WHY DO WE NOT ALLOW ROTATING MASTS?

[MattB (Guest)]

I can't answer your question directly but I'm interested in how you would implement a rotating mast. How would you isolate it from to of the forestay, jib halyard and stay the mast back at the hounds to stop the rig falling forward under jib halyard load? Is there a class that has already implemented rotating masts with twop or three sails? how do they do it?

Matt

[David G (Guest)]

Ref. Other Classes

The Firefly had a rotating mast and achieved this by having a wire bridle to support a floating jib halyard block.

But I think we might be more interested in over rotating rigs, in which case we might look to Tasars or Tornado's.

I think that rotating rigs would probably be the most interesting and least contraversial avenue to pursue, since this is all about improving the efficiency of the rig rather than attempting to increase sail area or reduce weight, which would tend to outclass the existing fleet.

However I remain to be convinced that the class has the appetite for change.

Regards,

David
N3461

[Ken (Guest)]

What he said...
Rotating rigs with jibs are proven technology, as David says look to the Tasar, or the NS14. Indeed nip into your local waterstones and sneek a look at Bethwaites 'High Performance Sailing' which covers them in some detail.
The short version is you have a deck stepped mast, and all the usual wires...
I am also in favour of the concept, although the cost of developing a new mast, and new sails, and potentially a bit of rearranging about of the boat might quell enthusiasm.

[Mattb (Guest)]

in principle then - if it could be achieved without having to purchase another mast I'd be happy to vote for a change in the rules. its really the cost involved because I wouldn't want ot encourage an arms race that excules all but the financially secure.

[EmmaW]

For those of us who don't know about these things, could someone explain how a rotating rig would be more efficiant?

Thanks...

[Ken (Guest)]

Using an appropriate wing section mast, the airflow coming off the mast is much cleaner, reducing the turbulence at the front of the sail thus increasing efficiency. A wingsection mast doesn't necessarily have to be an enormous thing from the boeing spare parts bin, as exemplified by the short squareback design seen on the tasar. This increase in efficiency comes with an alteration of the centre of effort for the rig, so if you used the same sized rig in the same place you would probably have to move the centreboard forward, hence my earlier comments about rearranging the boat.

I reserve the right to be shot down in flames though...

[MattB (Guest)]

I think there would be a significant areodynamic benefit of rotating a normal superspars round section mast. Although most of the rotating mast you see have a elipsoid shape at least you would effectively hide the mast track if the standard superspar rotated with the sail.

The problem with circular fixed masts is that when you are off wind the mast becomes much broader and asymetrical in the direction of the wind flow. That causes significant vortices and turbulence over the lifting part of the sail. If you let the mast rotate then it keeps its neat narrow profile to the wind at all points of sail.

[Tim L (Guest)]

Check your bethwaite book Matt, wing masts have to be a fairly critical shape to give any benefit.  If simply rotating a standard rig was more efficient then toppers and lasers would go a lot more quickly!!

[JohnMurrell]

Tim,

quite right, also the main has to be a totally different shape.

I looked into it hard with 3444, Linton was going to make the mast, Frankie the sails,the boat was built for a deck stepped mast and there had been a rules dispensation to allow the development to take place, however as with all things when I wanted to take it up it had become 'time expired'!

John

[Mikey C]

why do you use an Angell mast then Tim? Surely you didnt pay all that extra money for a narrow mast for aesthetic reasons?!

I'm with Matt, it will improve performance on a standard rig, but a proper section has to be the way to go to do it properly...

How do we go about proposing this to the committee? The only way we will find out if the class is willing to move forward or not is to ask them - up untill now we have just thrust more weight reduction under their noses instead of actually making the boat better.

Cheers all

Mike C

[MattB (Guest)]

Well it seems Tim is right in pointing out that circular section masts don't make good wingmasts. I still maintain that rotating my current mast would make some improvement in drag - but making this rule change would allow the next mast commision to have the 'correct' faired shape. That brings with it substantial benefits in lift - primarily in the luff region of the sail. That drives the boat much faster and brings the centre of effort of the sail forward. Consequently all those implementing a rotating mast would indeed have to move their centrebords forward or the mast back by almost a foot. Bouncing Ben is - I think -  the only N12 desiged with that sort of radical flexibility in mind.
Consequently the advantage lies with the commisioners of new N12's and that is why - I suspect - that we don't allow them. Its a pity but we can't have the fleet split between the haves and have-nots just as we've learned to race equitably between the db/admirals cup boats.

[Mikey C]

I think a foot might be a little bit over the top! Bearing in mind that the jib efficiency would not change, the only movement will be in the chord of the mainsail + mast area - probably more like inches, and im sure most people have inches of mast position adjustment available, and if not then a little more rake will compensate.

Mailsail will need to be a bit flatter, but at the end of the day people buy new sails anyway - certainly the sort of people that worry about this sort of thing have a new set at least once every two years...

all boats could be converted pretty easily to a deck stepped mast with a stump to deck level for negligable cost - the likelyhood of the front end of the fleet throwing money at new masts until a new solution has been proven is pretty small, leaving it with the tinkerers to come up with cheap ways of experimenting... Balsa/foam fairings on top of round masts etc etc...

As David says, this is probably the best option for improving the performance without completely burning the rule book, and the class needs to avoid its previous mistakes of sitting on change for too long and avoid single big rule changes

Cheers

Mike

[david g (Guest)]

I think that the centreboard position could be a bit of a red herring, there is still scope to play about with mast rake, jib area and the ability to swing the tip of the centreboard forward, without having to hack the boat about.

My memories about aerohydro make me think that this is about removing the separation bubble aft of the leeward side of the mast and improving attachment on the leeward side of the mainsail.

With regard to moving this on, the fast track route would be to put a proposal to the agm, however it is unlikely to get through without a thorough campaign and class consultation, i.e. article in ratchet, geting the class and committee behind it, and possibly carrying out a trial.

Apart from the initial development costs (which you might be able to pass off onto the sail and sparmakers) I cannot see that the hardware costs woukd be a lot different to now.  The difficulty you might have is persuading people with old boaats and rigs that it is worth voting for a rule which MIGHT limit their competitiveness.

Also if you are going down the route of removing the controls on rotating rigs, it would only make sense to also be considering removing any restrictions on battens.

All the best,

David
3461

[antony (Guest)]

I have just spent the weekend in Salcombe sailing my 12.  I guess that most of you spent the weekend on your PCs.

I am very unlikely to vote in favour of even permitting a trial of rotating rigs in the future.  I am pretty likely to campaign against it.  I am also pretty likely to leave the class if it is approved, after 16  years of active 12 sailiing.  

Salcombe is one of many great 12 venues that are completely unsuitable to a boat with a rotating rig that I enjoy going to.  

Antony
N3484.. for sale if this gets any support.