America’s Cup - ETNZ launches 1st AC75 (new)

[Pelagic]

Originally Posted by cal40john

Since the cup is named after the yacht that won it the first time, if you're going to attempt to change the name perhaps more appropriate to call it the Dolphin cup, the name of the kiwi boat.

I think the present name is perfect!

America in the 1850's represented a fledgling country, massive immigration from accross the Seas into a melting pot and a flagrant disregard for Form over Function.

That is the spirit of the America's Cup.

[MicHughV]

no offense taken...you make some good and valid points..

in bygone days I often raced my respective boats in area regatta's and races...it always amused me to see how " ratings" were assigned.....if I (or someone else) won too often) your " rating" could be arbitrarily re-evaluated..

I have raced to Bermuda several times...after the first 12 hours you will be lucky to see a competitor again until you reach Bermuda.....7-11 days out of sight....out of mind...I have often suspected that there was serious engine useage going on or other shenanigins in those races as some competitors would post some stellar times in windless races....off course...what happens at sea generally stays at sea...those races never had the prop shaft sealed, but one tell by the guilty looks that something was amiss.

In this regard, one-off racing is probably the fairest, where each competitors sails in identical boats, though any small advantage anywhere we likely be exploited.

all that aside, watching the a/c cup is one of the few " sports" I enjoy watching....if one can't actually be there, the a/c cup has been made more viewer friendly with onboard camera's, drones and the like..

I wonder if Gary Jobson will provide race commentary again ?

[jmh2002]

Team UK launched their boat today, and it is also more of a scow type design, so we are 50/50 so far on general hull types. And she again has foil wing bulbs, so this means TNZ are the only design without these (so far - they may be added later).

https://www.sail-world.com/news/222767/?source=rss

She also has quite an unusual topside design, I think trying to squeeze the maximum out of the rules has generated this unusual shape.

However a nose dive at speed might be interesting because that looks like a big funnel for water to be scooped up and coming flying down the deck directly at the crew...

More photos here too: https://www.shaunroster.com/Water/AC...L8J-UJLBqV_teM

[Tillsbury]

You’re right... I hope they’re holding on when they nosedive

I see their simulation software doesn’t have a “pretty” setting...

[jmh2002]

I note that the SailGP crew now wear harnesses and are connected to the boat. Occasionally I have seen crew be flipped out of the cockpit during a nose dive but now they only fly so far until the harness stops them

[jmh2002]

Check out this video, especially the GBR crash after 1 minute:

https://www.youtube.com/watch?v=q8xSkICK0tY

[jmh2002]

America's Cup: Images and analysis of INEOS Team UK's first AC75:

https://www.sail-world.com/news/222778/?source=rss

[CassidyNZ]

Originally Posted by jmh2002

She also has quite an unusual topside design, I think trying to squeeze the maximum out of the rules has generated this unusual shape.

However a nose dive at speed might be interesting because that looks like a big funnel for water to be scooped up and coming flying down the deck directly at the crew... :

Interesting slab-sided cockpit area, almost as though the intention is to contain any wave coming over the front and direct it straight at the crew. The front deck looks like the intention is to reduce the effect of a nose dive but my cynicism points to a quick way to send the boat to the bottom. But what do I know.

Just can’t think of any rational explanation for either feature. My limited understanding of aerodynamics let’s me think that the foredeck shape will place downward pressure on the bow at 40kn+. Is that a good thing? Maybe. The interesting thing for me is that their smaller test boat had neither of these elements - maybe that’s simply because they didn’t want to show their hand.

For sure, these are design elements that will be really hard to change if they don’t work.

Time will tell.

[skipperpete]

All these amazing advance in hydrodynamics and we still have no mutually agreed opinion on whether a trailing propeller creates more drag than a locked propeller.

[StuM]

Originally Posted by skipperpete

All these amazing advance in hydrodynamics and we still have no mutually agreed opinion on whether a trailing propeller creates more drag than a locked propeller.

The facts are quite clear to anyone who has studied it. Locked creates more drag for a fixed prop.

[MicHughV]

...this is going to be one for the record books.....a pretty wide divergence in hull design and we have yet to see the rigs...
...regardless of final outcome.....the theory about go-fast racing sailboats has been forever changed..and time will tell which outlandish design takes home the trophy...

...but how does this affect you local cruiser ?? having those two foils poking out the side is going to make finding a marina a problem.....I can see it now "....yessir, we can accommodate your 75' overall lenght.....what is your draft and beam ?.....what ?....oh **** !!"..

..ah well, I continue to watch the progress of this a/c with interest......

.....it's like owning a Ferrarri or Lamborghini.....fast, yes, practical, no.
Some many years ago, I had an opportunity to drive an earlier model Lambo with the proviso I gas it up, which I willingly did for this privilege.....ha, was I in for a surprise.....when you put you foot into it, your gas consumption shrivels to around 3-4 mpg.....a 20 gallon tank can disappear in an extremely short time.....hmmm...like 30 minutes....ah well, money well spent.....but no thanks.....it was fun.....for sure....

...these a/c boats follow in the same thread....fast..undoubtably...practical....no, I don't think so.....

[jmh2002]

Originally Posted by Tillsbury

I see their simulation software doesn’t have a “pretty” setting...

In the right context I'm all for the 'practical is beautiful' and 'fast is beautiful' type of thinking sometimes. So all I can say is that Team UK's boat better be damn fast for me to start thinking about liking how it looks...!

Originally Posted by CassidyNZ

Interesting slab-sided cockpit area, almost as though the intention is to contain any wave coming over the front and direct it straight at the crew.

Yes, those were my exact first thoughts too! Hopefully the designers have some other intentions...

[MicHughV]

...glad to see the Brits making a go of it this time around....
...I notice their boat also sports foils on the rudder..makes sense to me.....it would appear to be quite a feat to balance a 75' boat on just one immersed foil...nice to have that " extra" leg in the water at the stern to help control pitching..
...the Brit scow shape....maybe to reduce weight in the bow???
...definitely taking a wave over the bow would wash down the entire length of the boat..wonder what their thinking is here ???
lastly, their foil wings are " straight"....no curve or little flip on the ends...one sees these on aircraft now, ostensibly to reduce turbulence....wonder why the Brits opted for this design..
...many questions...let the games begin !!!

[MicHughV]

...regarding the drag of a spinning propellor vs. a fixed propellor...I was told by an experienced navy helicopter pilot, that a helicopter pilot can still exert some control over a helicopter with a failed engine but spinning blades vs. blades that don't rotate at all...
off course, helicopter blades are long and narrow vs. the more stubby one's of a boat's prop..but I would imagine the same theory would apply...
a spinning tree leaf also falls much slower than a non spinning leaf, so there must be some theory behind this phenonima..maybe wiser heads can provide a better answer...

[cal40john]

Originally Posted by MicHughV

...regarding the drag of a spinning propellor vs. a fixed propellor...I was told by an experienced navy helicopter pilot, that a helicopter pilot can still exert some control over a helicopter with a failed engine but spinning blades vs. blades that don't rotate at all...
off course, helicopter blades are long and narrow vs. the more stubby one's of a boat's prop..but I would imagine the same theory would apply...
a spinning tree leaf also falls much slower than a non spinning leaf, so there must be some theory behind this phenonima..maybe wiser heads can provide a better answer...

They have -
This link has Maine Sail's test and links to MIT and Strathclyde
Propeller Drag under sail, Article

Yachting Monthly test -
https://www.yachtingmonthly.com/gear...let-spin-29526

View figure 6 in the link below (Strathclyde) -
http://www.plaisance-pratique.com/IM..._sdarticle.pdf
Last two paragraphs in the conclusion -

The experimental results confirm that a locked propeller
produces greater drag than does a freewheeling screw (up
to 100% more drag was observed, this being at higher
speeds). Furthermore, for the freewheeling case, the
magnitude of the hydrodynamic resistance is significantly
affected by the amount of frictional torque on the shaft,
low torque being accompanied by low drag.
Finally, a simple model of sailboat hull resistance has
been used to illustrate the likely scale of the drag penalty
due to various arrangements of trailing propeller. This
shows that, especially for the case of craft having moderate
or low DLR combined with powerful mechanical installations, the impact on sailing performance of a trailing
propeller is very significant indeed. By combining the
present findings with other more detailed techniques which
exist for modelling hull drag, the influence of propeller
drag on sailing performance should be substantially
predictable.