• Announcements

    • Zapata

      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  
Sign in to follow this  
xavic

ac45's daggerboards

Recommended Posts

Hello ladies and gentlemen,

I'm making my final degree's work about a numerical studying of the daggerboards used in AC45. I would be glad if someone could give me some information about the profiles used there (maybe naca's profile? which series?)
I've been searching the whole google but without luck.

Thank you very much sailors smile.gif

Share this post


Link to post
Share on other sites

"Manufacturer's Measurements" kept close to the chest. I do not think you will find that information published anywhere.

Share this post


Link to post
Share on other sites

I would be absolutely shocked if you could find this information before the end of the Americas cup. They have spent millions designing those foils, and aren't likely to give away any technology until after the race is over. Even after the race it wouldn't suprize me if they consider it proprietary information and keep it secret.

Share this post


Link to post
Share on other sites

I don't see why contacting Core is such a ridiculous idea. Why would the basics of AC45 foils be a big secret? They are already obsolete as far as AC35 development is concerned and if teams were sufficiently interested they could reverse engineer them themselves. Core might be helpful or they might tell him to fuck off. Worth a try.

Share this post


Link to post
Share on other sites

They have spent millions designing those foils,.

 

AC45 foils. It's unlikely much has been invested by Core on design; as far as any outsider knows these were a gift of design work done by teams in AC34. IIRC weren't they a LR design?

Share this post


Link to post
Share on other sites

you can always ask. Core is more likely to have the answer than any of us here. Might not get the latest boards, but some early development boards (which my guess is, you'd be after), but either way, core will have the answers. so contact them and ask.

Share this post


Link to post
Share on other sites

You'd be better asking Martin Fischer, he designed them. But don't expect him to be very forthcoming, the guy makes his living off his foil designs. It's unlikely that Core have the right to distribute the information even if they have it in a useful format.

Share this post


Link to post
Share on other sites

^

 

Right, he's credited with the design. Any idea who contracted him to do it? I have a recollection the foil design was donated by LR but maybe I'm imagining it.

Share this post


Link to post
Share on other sites

I know for a fact that the work we did for AC teams was held strictly under a NDA. We weren't even allowed to discuss if we were making anything for an AC until after it was over, the contract required us to deny that we did any work for them if asked.

 

Maybe I am wrong, but my guess is you are going to run into three categories of people...

 

1) those who don't have the information. Basically us, and we are worthless

2) those who have the information but do so subject to a NDA. The builder, designer, crew, shore crew, etc.

3) those who have it, and could give it to you. But they won't because they have a financial interest in keeping it closely held. So the AC teams themselves. They won't turn it over because holding the data internally increases their chances to win.

 

If I had to guess, the best bet would be a team that spent the money on research and then folded because of a lack of money or interest. That maybe willing to release their data to a scientific paper, or design firm. But my guess is some other new team came in and bought up their data when they dropped out.

 

But sure, check around, email the principles, etc. but I don't think you will every pry this data from the hands of an AC team.

 

Now if you just want foiling data, going to a company like DNA and asking what they did on the Gunboat, and what's being used for the A-Cats may be much more likely to end with good results.

Share this post


Link to post
Share on other sites

As an alternative the first set of foils of the TNZ AC72 is on display in the Auckland maritime museum. Maybe you can find an Aucklander willing to take some measurements for you. AFAIK locals get in for free so no cost involved.

The foils are generation 0, but at least they are proven to work.

Share this post


Link to post
Share on other sites

I know for a fact that the work we did for AC teams was held strictly under a NDA. We weren't even allowed to discuss if we were making anything for an AC until after it was over, the contract required us to deny that we did any work for them if asked.

 

Maybe I am wrong, but my guess is you are going to run into three categories of people...

 

1) those who don't have the information. Basically us, and we are worthless

2) those who have the information but do so subject to a NDA. The builder, designer, crew, shore crew, etc.

3) those who have it, and could give it to you. But they won't because they have a financial interest in keeping it closely held. So the AC teams themselves. They won't turn it over because holding the data internally increases their chances to win.

 

If I had to guess, the best bet would be a team that spent the money on research and then folded because of a lack of money or interest. That maybe willing to release their data to a scientific paper, or design firm. But my guess is some other new team came in and bought up their data when they dropped out.

 

But sure, check around, email the principles, etc. but I don't think you will every pry this data from the hands of an AC team.

 

Now if you just want foiling data, going to a company like DNA and asking what they did on the Gunboat, and what's being used for the A-Cats may be much more likely to end with good results.

 

Great that you're an insider. Shame you can't read the question.

 

AC45! These are one design - hell hand over a million and you can have one in a month. Nothing to do with any 'AC Team', their 'super secret research', or their NDAs.

 

It was ACDUH who comissioned the original non-foiling design.

Actually there is a(n ex-) ACteam involved - LR. And they would probably be glad help to undermine AC everything :D

 

But there are 100s of high def photos of the things by now, + they put them on display at every ACWS event and any boat show they can find.

 

But have it this way if it makes you feel better...

 

0688fe3.jpg

 

"That's right Chief, I've never heard of the AC45 foil from the Naca 2414 series bent 94°".

Share this post


Link to post
Share on other sites

The funniest thing about the above post is the reference to Naca foils. When are people going to get their head around the fact that top end designer's don't pick foil sections out of a catalogue. The Naca foils are a systematic and published analysis of the effects of changing foil parameters. Yes you can used the published data and pick something that is kind of "ok" for your use but that isn't and never has been their point. What they are good for is calibrating in house or proprietary CFD programs.

 

Ignore the whole Americas cup thing, ring Holland Composites and ask for the lines plan for their new DNA A cat. There is nothing stopping you from buying a boat and measuring it so why shouldn't they release the info to you?

Share this post


Link to post
Share on other sites

If you went to the trouble of downloading one of the many readily available NACA foils in the archaic point file format they use and then load it into any modern CAD program and interpolate a curve from those NACA points it will look like crap. I often use those files and draw a new clean NURBS curve that matches the old clunky NACA points and use that. Way easier that trying to tweak an unfair curve that results from the point data that represents NACA foils.

Share this post


Link to post
Share on other sites

The funniest thing about the above post is the reference to Naca foils. When are people going to get their head around the fact that top end designer's don't pick foil sections out of a catalogue. The Naca foils are a systematic and published analysis of the effects of changing foil parameters. Yes you can used the published data and pick something that is kind of "ok" for your use but that isn't and never has been their point. What they are good for is calibrating in house or proprietary CFD programs.

 

Ignore the whole Americas cup thing, ring Holland Composites and ask for the lines plan for their new DNA A cat. There is nothing stopping you from buying a boat and measuring it so why shouldn't they release the info to you?

Still quite tough to beat them over a range of conditions, though.

Share this post


Link to post
Share on other sites

 

 

Ignore the whole Americas cup thing, ring Holland Composites and ask for the lines plan for their new DNA A cat. There is nothing stopping you from buying a boat and measuring it so why shouldn't they release the info to you?

 

If it's anything like moth foils, nobody will ever get any info on the profiles used by a commercial company, unless it is completely out of date.

Share this post


Link to post
Share on other sites

from a g-tran

--

 

Voilesetvoiliers.com: But because of their size, the "tips" (horizontal portion of the foil) have enormously twist under load!

MF: The profile is differential along the "tip", precisely because that part spin, like a wing. It's like a veil that opens in blast: these forms are very complex. The "shafts" have their own profile since they have a dual role: drift particularly close door and "tip". So there are several possibilities for forms of foils according to the wind conditions, playing on profiles, the thicknesses on the twist.

 

https://translate.googleusercontent.com/translate_c?depth=1&nv=1&rurl=translate.google.com&sl=auto&tl=en&u=http://www.voilesetvoiliers.com/course-regate/martin-fisher-une-choregraphie-du-vol-coupe-america/&usg=ALkJrhhi-47llpZr0VwL3pAcHtoCBGrNlA

Share this post


Link to post
Share on other sites

He got the wind limits wrong though - bit unbelievable...that'll stuff 'em! :D It's not 6-22kn.

 

 

Voilesetvoiliers.com: There will be foils for 6 to 15 knots of wind and 12-22 knots of wind?

MF: Probably: Wind limits are at least 6 knots, 22 knots maximum.

 

 

 

"WIND LIMITS"

 

.......all races for AC Class Yachts shall be started when the approximate average true wind speed is between six (6) and twenty-five (25) knots.......

 

 

So his foils won't handle the rough stuff....

 

Shhhh!

Share this post


Link to post
Share on other sites

Nicely complemented by an interview with Ferdinand Van West in Catsailingnews coupla days ago, about 4-pt foiling and the Nacra15-17. Liked the clarification that the windward Z-foil daggerboard contributes to heave stability in lieu of the leeward uptip - but that entails that the boat must not heel and the inherent windward board lift decreases the available righting moment. So performance wise the 4-pt configuration will always be inferior to 3-pt

Share this post


Link to post
Share on other sites

^ Haven't read the interview - but does the heave stability come from the lift on the windward board or just the fact it's under water? Could you set it to the neutral lift angle and still get the extra stability without the negative effect on RM?

 

I guess not - or they'd be doing it?

Share this post


Link to post
Share on other sites

^

Beats me - but I guess the whole point of 4-pt foiling is not fiddling with boards (rake and/or AOA) while under way

Share this post


Link to post
Share on other sites

Nicely complemented by an interview with Ferdinand Van West in Catsailingnews coupla days ago, about 4-pt foiling and the Nacra15-17. Liked the clarification that the windward Z-foil daggerboard contributes to heave stability in lieu of the leeward uptip - but that entails that the boat must not heel and the inherent windward board lift decreases the available righting moment. So performance wise the 4-pt configuration will always be inferior to 3-pt

While I understand the theory, this isn't actually what is being found in practice and I suspect there are other factors coming into play that are not being discussed. The theory goes that the windward board decreases righting moment, and while that may be correct in practice, there must be some compensating benefits.

 

It is true that we have not seen enough direct comparison to know for sure what is going on. However, the few A Class boats that have been fitted with 3-pt set ups have been slower than 4-pt. Add to that the comparative performances between non foiling A's and the latest foiling ones. When foiling first started in the A, the biggest problem was being fast enough to windward. The conventional boats had an advantage, as one might expect. Guys like Stevie Brewin were getting to the top mark behind people they weren't usually behind. There was clearly an issue. Now, the foiling 4-pt A's are quicker upwind, even when not foiling, than the floaters.

 

In short, what i believe is happening is that while the 4-pt set ups lose out on righting moment, they gain it back, probably from lower drag meaning they are as fast, if not faster. When you add in other factors, such as simplicity of sailing, you get a noticeable advantage - note that latter comment is mentioned in the interview.

 

It's also worth remembering that a lot more development has been done by very smart people on the 3-pt set up. The 4-pt z set ups are really being developed on a far more ad hoc basis. This is because the AC rules (the AC being where the money is) force them down the 3-pt route. It would be interesting to see what would happen if the same attention was given to the 4-pt set up. My gut feel is that with development, 4-pt will become the all round best solution, being faster and easier to use.

 

but I guess the whole point of 4-pt foiling is not fiddling with boards (rake and/or AOA) while under way

 

I think the opposite is true. Speaking to people who sail both Flying Phantom/N20F type boats and A's, you adjust the AoA on the A far more. You set it differently for upwind and downwind, you change the amount of rake for different wind strengths, you use different rakes depending if you are trying to foil upwind or not. And some are even setting the boards differently on each side upwind, either to reduce drag or to attempt to get some righting moment. With people now leaving the downhaul on the same amount all round the course, the board rake is probably the most important control on a foiling A.

Share this post


Link to post
Share on other sites

Don't worry, Stingray, not only is it not a dumb question, it is one that a lot of A Class sailors would like an answer to! The short answer is yes, but the long answer is maybe.

 

I know of people training in both Europe and Australia who have found conditions in which upwind foiling seems to pay (I don't know what the Yanks are up to, so cannot comment). That is very different from seeing regular upwind foiling at the next world championships. My best guess is that if conditions are right, we might see some upwind foiling at the next worlds, by a few at the front of the fleet. You will only need a few bursts of foiling to have a big advantage over the others. It should be pointed out that when racing the Flying Phantoms, upwind foiling only pays some of the time, so this isn't just a 4-pt foiling issue.

Share this post


Link to post
Share on other sites

^^ If 4 pts As are faster than 3 pts upwind, you don't have to be a genious to conclude that either:

 

- 4 pts have less righting moment but compensate by more lift

or

- the ww board is negative, producing more rm.

 

I would opt for the 1st hypothesis,

Share this post


Link to post
Share on other sites

However, the few A Class boats that have been fitted with 3-pt set ups have been slower than 4-pt.

What does 3-point and 4-point mean? I imagine whether the daggerboards are raised/lowered on tacks and gybes but is there more to it than that?

Share this post


Link to post
Share on other sites

 

3-pt means both rudders/stabilizers and leeward (uptip) board in the water, 4-pt has the two (currently Z-type) boards down all the time

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this