Those with longer memories may remember a discussion about the viability of putting wings at the masthead to reduce drag from the rollover vortex at the top of the rig etc.
I did think of putting some on 3497 but (due to a distinct aversion practical tasks) convinced myself that as America's Cup boats didn't use them they probably wouldn't work... So what do I find surfing the spanish AC team site on another quiet shift? An overhead shot of the boat with a set of wings (with mini-winglets on the ends) right at the masthead. A bit more digging finds that Oracle are also using them. Can't find anything to confirm that they're there for drag reducing purposes but that's the best guess.
Question is would it scale down to 12 size? Would the wings have to be proportionally larger on the 12 to get the same effect??
where are the wings: I can't find any link except...
http://www.americascup.com/en/galleries/index.php?idIndex=263&idPage=1
Philip
N3253
The best photos are on the Desefaio Espanol team site but the way the photos of setup there's no direct link. The others are pics of the oracle boats on their cradles on valenciasailing.com somewhere in the earlier 06 archives (its a blog) but have to do some work so no time to go look out the link for you, sorry...
http://www.desafioespanol2007.com/imgGaleria.aspx?t=FotoPortada&publica=1&Id=1&galeria=8&w=640&p=1&campo=100.jpg
Is this what you were on about?
They seem tiny and look more like a wind hawk on steroids!!
Jon
3211
Yeah that's it, there's a closer up photo than that one too. If you kill off the vortex at source (i.e. the leading edge) I guess they wouldn't have to be that big. Presumably they're swept back a bit to stop them poking holes in the kite?
Tim,
Do you really think that it'll make a lot of difference? It's perhaps the same effective power increase as farting underwater whilst doing the crawl.... ::)
Bettering one's sailing technique would be more effective ;) ;)
Possible, but bear in mind that any difference proportionally is greater on a smaller object. That being said I am no aerodynamic (or hydrostatic) genius, but I bet that they would be both fiddly to make and fit, and if there were any benefit to having them, someone in the 14s would probably have had a go at it already.
:-/
Hey Jimbo,
You are assuming Timmy isnt already a sailing god in disguise....
I think wings would be best suited with square topped rigs, but its fun and in principle the theory is good.
Cheers
Mike
Is it possible the less stable platform supplied by a dinghy would make them ineffective. All that pitching and mast tip flexing and that... You'd have a job deciding which angle to have them at... I suppose they could be adjustable.... mmmm.... more string.... 8)
I think they look great, and thats all that matters right? and when I have a spare few days at work will run some analysis.
Anyone got any more details than those pictures?
[quote by=Jimbo41 link=Blah.cgi?b=Cool,m=1161228639,s=5 date=1161254319]Tim,
It's perhaps the same effective power increase as farting underwater whilst doing the crawl.... ::)
Bettering one's sailing technique would be more effective ;) ;)[/quote]
Undoubtedly, though Mike is obviously correct in noting that I am in fact a sailing god (except at windy gybe marks at burton week).....
It wouldn't be any power increase but would be a reduction in aerodynamic drag which = higher pointing. Most useful developments often seem to be the subtle ones (and cheap and within the rules (I think)).
I don't think the movement of a dinghy any worse than an ACC when you consider how high the rig (i.e how much any movement of the boat is amplified) and how much they heel - suggests that the angle of attack isn't too critical, just that it disrupts the vortex. Mike's probably right that it works best with square top mains as they help reduce vortex drag too - but suspect the only reason nobody has tried it on 14s or Moths is they're too busy fiddling with underwater wings. Development is not a linear thing, more dependent on fashionable focus of the day...
Jon_P - haven't seen any more technical stuff anywhere but one thing looks likely from the photos - that the end winglets are hinged and can be oriented for each tack - how cool is that...
See also: 'Induced drag is easily 75% of the total air drag of a sailboat' http://www.wb-sails.fi/news/99_1_AeroShape/Aero.htm
http://www.wb-sails.fi/news/470StreamAnim/index.htm
ok another pic to show what they are trying to prevent.
http://www.jonpaton.com/images/winglet.png
The thing I dont understand is how somehting as small as that little thing in the photo is going to change this massive vortex. maybe it does...
are we sure it's not just a fancy wind indicator?!
I would offer to try one out but i don't think that a 5% reduction in drag is going to help me win the race!
Could be manufactured out of wood - to keep Jim happy...
Just spent some time looking at the article on foils and what happens when smoke is passed across them. A way that I remember checking things out like this in my younger days was to sail when it was snowing. Yeah I know it sounds sado masochistic, but it does show you the air flow across the sails and the pretty patterns that can be made when you get things wrong. Only problem is you spend more time looking at the snow patterns than where you are going, so do it on the sea or on a v. large lake.
You could even get Jim to make some wooden winglets to see what happened at the top of the mast