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New imoca boats

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This is from the float of the old Groupama but I think shows what the 60s now allow. The upper bearing can move allowing up to 5 degrees of foil angle change iQyDH2AvttFdLW_LI5mtxj8k4x4UXcJRRg6ZhFT0OYbbNlazFghP_TCCb7mxCicBIH98eQZGSeL5t0_jUAf30Yza6C3BzTujL109QW1rV6Py35B584PxV2HXHcUC5RAKkvE_hr3l3cIJrejr3GJcOC9qRS_p8GtH0kDQ9GXMskbh9Eliqx7wFmQy3sv896iJ0C3hDIPEmuYTLu2YOJPPF1C4wttT6yUQY7uXv2w4vWVcCmc-lmXdTXWezWaNP37fpu1e0R6vY8dIY3IweXpEFoYBKxM7Ip99cHuIvJBG4_8OuEylk8Wv06uQhW8LiWEuidYai9Z9wCh_8Mzes7IcG1pFOGpJlzoy8tfkpxXlNOIZ6eu-w6Wy0sW0VklPcCT17bJUDgUdFtSknKgBKMQ6goFPRAN3PtByTcc40lqevb1rXxtPfC6nCq3WydTqNE-7Zj9ZuzI9RWQ9-8Me7es78RM5ItIC5MMEvmh7iEVEaybEhtduIsPDlhC01NU9UyeAqk9z6G5o4FsOurIgM3pa1x3R_ndGDhqeFZ67L1q9RlXj-LxrcIg50iJFrQSzaE6H7Fl3ghP5C3BVn7KTnRccZbXqBkqWmUKwqwBNXvtkruxogfia29rAAwP87lkHxs7U=w883-h662-no

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5 hours ago, LeoV said:

Chimp, your fore and aft, did you mean in and out for the foil ?

 

No, I think Chimp meant fore and aft.

By moving the "deck bearing" of the foil case fore and aft, you change the angle of attack of the foil (at least its "horizontalish" section). And that angle variation is not supposed to be more than 5 degrees from what I read above.

 

CORRECTION !!!

Because the foil case is not vertical but heavily tilted, the fore and aft move of the deck bearing will have an effect on BOTH the horizontal section of the foil and the vertical section of the foil (surface piercing tip), but less than 5 degrees for both???

This is going to be interesting for the surveyors to measure....

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Yep, never boring...

second bearing may have a degree of rotation, only in translation, nice words :)
 

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On 8/28/2018 at 4:04 PM, LeoV said:

Foils move back and forth? New to me that the rule allows that.
Trying to understand, so a sliding cassette in the hull, in an angle. In the cassette the foil...

So back to the rules book, yeah;

(h) Effective from 1 January 2018, a foil shall be retractable using one degree of freedom and:
(i) A second degree of freedom may be used if a set of two bearings is used to guide this appen
(ii) One of the two bearings shall be a non-adjustable bearing positioned close to the hull.
(iii) The other bearing may have a degree of freedom.
If it exists, this
degree of freedom shall be a translation and shall limit the rotation of the foil to
of 5 degrees.

(iv) This angle is measured from the non-adjustable bearing positioned close to the hull shell

Will muse over this till  understand :)

Thanks for posting this Leo

The way I read this, is that if there is twist in the foil that would "corkscrew" the foil as it is deployed inwards  or out - then the amount of secondary twist (rotation) is restricted to 5 degrees.

Which in itself would be both useful and ample enough to effectively mode the foil from high lift to low lift and vice versa, across the speed range.

Thoughts?

 

 

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While impossible to tell how it is handling from this pic, it does show whoever did the colour scheme and graphics got it right..

...this is no "vegan" machine.

IMG_20180830_141012.jpg

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Allegedly 15 knots of wind.  There's an awful lot of daylight underneath that hull.  

40411097_1834530999915285_2368882262851715072_n.jpg

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With these foils, I suspect that "code sails" will become less relevant as the apparent wind will nearly always be forward.

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there's a lot of room at the foil deck exits for longitudinal movement, is that how they're getting foil pitch control? the deck house looks like it was designed for residency. fkn' amazing machine, I want to send it in 30 knots true.20180605564269f5ac9bdea7d79e2ffb-video-beyou-en-route-vers-la-route-du-rhum-ep-8-un-bateau-avant-gardiste_2.jpg.e59259ee77a27a98aebdec43241a62fc.jpg

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5 hours ago, r.finn said:

Allegedly 15 knots of wind.  There's an awful lot of daylight underneath that hull.  

And he said doing 24k.

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7 hours ago, jack_sparrow said:

An "extended" and "retracted" side by side foil comparison.

 

FB_IMG_1535763466574.jpg

That is actually the maximum retracted position (can't get both foils in at the same time, so port is fully retracted and starboard is as retracted as possible)

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Proportions aren't exactly the same but I there is a bit of similarity with another "mean machine", namely the corsair f4u.

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Hanging to see some video footage of this thing as per the photos with a lot of the boat out of the water. Anyone know how many new Imoca's are being built ATM?

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4 hours ago, terrafirma said:

Hanging to see some video footage of this thing as per the photos with a lot of the boat out of the water. Anyone know how many new Imoca's are being built ATM?

Someone said 5 or 6 earlier this year. They were correcting me, as I had only heard of 3, so it sounds as though it is still healthy.  Not sure how many are actually in build at the moment.

 

 

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3 hours ago, eastern motors said:

Any word on the keel pin incline angle?  

 

is it inclined? 

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On 9/3/2018 at 10:02 AM, Potter said:

Someone said 5 or 6 earlier this year. They were correcting me, as I had only heard of 3, so it sounds as though it is still healthy.  Not sure how many are actually in build at the moment. 

Sebastien Simon is mentioned to have one in process, that could be one you never heard off.
qoute figaro race site;
The solo racer who grew up in Les Sables d'Olonne, home of the Vendée Globe the legendary solo race round for which he has a new IMOCA 60 in build

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On 9/2/2018 at 3:02 PM, Panoramix said:

Proportions aren't exactly the same but I there is a bit of similarity with another "mean machine", namely the corsair f4u.

Image result for corsair f4u

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3 hours ago, eastern motors said:

It's certainly not declined.

 a diving plane wouldn't be a good look. inclined?

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No videos of the boat sailing yet and it has been out, so is it fair to say some cat and mouse going on? Something to keep us entertained in the meantime.! 

 

 

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On 9/6/2018 at 5:08 AM, 3to1 said:

 a diving plane wouldn't be a good look. inclined?

No. If "declined" is down toward the bow, then "declined" it is.

As I understand it, the axis is inclined to produce a negative AoA on the strut when canted. Since the keel is canted to windward, you don't want lift acting against the weight of the ballast, but rather a small negative AoA to enhance it and generate more RM.

At least that's the theory.

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I'd be pretty surprised if they were going for a negative AoA with the keel. it'd add righting moment but it'd be fighting the leeward foil which is trying to reduce wetted surface and keep the bow from plunging, plus it'd increase overall hull/rig loads. even the VO65's which were tippy because the keels were so light had positive keel AoA.

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13 minutes ago, 3to1 said:

I'd be pretty surprised if they were going for a negative AoA with the keel. it'd add righting moment but it'd be fighting the leeward foil which is trying to reduce wetted surface and keep the bow from plunging, plus it'd increase overall hull/rig loads. even the VO65's which were tippy because the keels were so light had positive keel AoA.

Even with the light keels, it seems Brunell found an extra gear by NOT fully canting in some breezy, reachy conditions.  No, I don't know why that worked.  I just read it.

So there are mysteries for us corner-bangers to ponder over.

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3 minutes ago, Left Shift said:

Even with the light keels, it seems Brunell found an extra gear by NOT fully canting in some breezy, reachy conditions.  No, I don't know why that worked.  I just read it.

So there are mysteries for us corner-bangers to ponder over.

Thank you Dongfong.

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28 minutes ago, Left Shift said:

Even with the light keels, it seems Brunell found an extra gear by NOT fully canting in some breezy, reachy conditions.  No, I don't know why that worked.  I just read it.

So there are mysteries for us corner-bangers to ponder over.

not sure if there's a mystery there, my guess is they probably attained a net increase in RM by not letting the keel develop positive lift, more so because the boat would be at high speeds and the keel would want to levitate if significantly canted.

didn't they also lower the center of effort of their sail plan in hard reaching conditions and sheet less giving the boat a wider groove?

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Them foils have some fat sections. Probably to keep them strong enough not to break. The loads must be crazy. Figure boat's displacement x dynamic loading factor of 3 or more.

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2 hours ago, RobG said:

No. If "declined" is down toward the bow, then "declined" it is.

As I understand it, the axis is inclined to produce a negative AoA on the strut when canted. Since the keel is canted to windward, you don't want lift acting against the weight of the ballast, but rather a small negative AoA to enhance it and generate more RM.

At least that's the theory.

Actually no.  The other way around, the stated thinking in the VOR65 design was that the lift produced by the keel at a postive AoA when canted reduced drag through reduced effective displacement more than the negative impact of the lost RM that a positive AoA entails, however in practice it seems the boats discovered that it made sense to limit cant angle for a better RM/drag trade-off.

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5 hours ago, DickDastardly said:

Actually no.  The other way around, the stated thinking in the VOR65 design was that the lift produced by the keel at a postive AoA when canted reduced drag through reduced effective displacement more than the negative impact of the lost RM that a positive AoA entails, however in practice it seems the boats discovered that it made sense to limit cant angle for a better RM/drag trade-off.

Limiting cant would also reduce keel AoA and hence lift, so maybe it's not as helpful as the designers thought.

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12 hours ago, RobG said:

No. If "declined" is down toward the bow, then "declined" it is.

As I understand it, the axis is inclined to produce a negative AoA on the strut when canted. Since the keel is canted to windward, you don't want lift acting against the weight of the ballast, but rather a small negative AoA to enhance it and generate more RM.

At least that's the theory.

open 60 keels are set with the pivot angled up towards the bow. Over the last 6 years this angle has continued to increase. The keel fin is vertical and can see the angle in the pic. The leading edge is to the right

39753177_10217473004485516_5567393572673552384_n.jpg

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12 hours ago, RobG said:

Limiting cant would also reduce keel AoA and hence lift, so maybe it's not as helpful as the designers thought.

Yep, that's my point.  Seems the Farr office overestimated the benefit of Lift vs RM

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If I remember well, I read somewhere that for some canting keel monohulls (maybe not IMOCA but rather Class Mini??), the design is even more complicated than that...

With a very short cord profile and a torpedo like bulb, positioned relatively forward compared to the foil; the profile was intended to twist.

When the keel is fully canted, with CG of the bulb relatively forward, the "nose" of the torpedo goes down a bit. You end up with a profile with a fairly high AoA near the hull because the rotating axis of the canting keel is pointing up forward, but because of the twist of the whole profile, the section near the bulb has a much lower (or maybe even negative???) AoA.

So the keel profile WOULD generate lift near the hull and no lift (or even downward force???) near the bulb.

 

If you know the real deal, please correct me and flame away!

 

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6 minutes ago, Laurent said:

If I remember well, I read somewhere that for some canting keel monohulls (maybe not IMOCA but rather Class Mini??), the design is even more complicated than that...

With a very short cord profile and a torpedo like bulb, positioned relatively forward compared to the foil; the profile was intended to twist.

When the keel is fully canted, with CG of the bulb relatively forward, the "nose" of the torpedo goes down a bit. You end up with a profile with a fairly high AoA near the hull because the rotating axis of the canting keel is pointing up forward, but because of the twist of the whole profile, the section near the bulb has a much lower (or maybe even negative???) AoA.

So the keel profile WOULD generate lift near the hull and no lift (or even downward force???) near the bulb.

 

If you know the real deal, please correct me and flame away!

 

Very possible but you have to look at the system as a whole.  If a twisted fin generates net zero lift through positive and negative lift being generated from different sections of the fin then that's a higher drag solution than a fin that doesn't twist at all but is angled to generate zero lift.  There's no way to get over the fact that creating net positive lift from a canted keel fin with a centre of effort to windward of a ballasted  monohull's centre of buoyancy reduces Righting Moment.  It's just basic mechanics.  

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5 minutes ago, DickDastardly said:

Very possible but you have to look at the system as a whole.  If a twisted fin generates net zero lift through positive and negative lift being generated from different sections of the fin then that's a higher drag solution than a fin that doesn't twist at all but is angled to generate zero lift.  There's no way to get over the fact that creating net positive lift from a canted keel fin with a centre of effort to windward of a ballasted  monohull's centre of buoyancy reduces Righting Moment.  It's just basic mechanics.  

Even if the lift close to the hull and the (hypothetical) downward force near the bulb cancel each other, on one hand, you are correct, this is no additional global lift.

But on the other hand, this is a "torque" or moment, that enhances the weight effect of the bulb. So more righting moment (at the cost of some more drag, true).

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3 minutes ago, Laurent said:

Even if the lift close to the hull and the (hypothetical) downward force near the bulb cancel each other, on one hand, you are correct, this is no additional global lift.

But on the other hand, this is a "torque" or moment, that enhances the weight effect of the bulb. So more righting moment (at the cost of some more drag, true).

More righting moment and increased drag through both keel fin twist and higher effective displacement

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17 hours ago, DickDastardly said:

Very possible but you have to look at the system as a whole.  If a twisted fin generates net zero lift through positive and negative lift being generated from different sections of the fin then that's a higher drag solution than a fin that doesn't twist at all but is angled to generate zero lift.  There's no way to get over the fact that creating net positive lift from a canted keel fin with a centre of effort to windward of a ballasted  monohull's centre of buoyancy reduces Righting Moment.  It's just basic mechanics.  

Correct.  But  righting moment (from the keel) isn't as important with the advent of giant foils.  

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On 9/9/2018 at 6:24 AM, eastern motors said:

Correct.  But  righting moment (from the keel) isn't as important with the advent of giant foils.  

Yes and no, the foils move the centre of buoyancy way to leeward so a lot more RM can be achieved.  In an IMOCA 60 the strength limits of the one design rig serve to limit the amount of RM any IMOCA boat can develop so in that case yes, keel RM becomes less relevant.  In another class without RM limits that wouldn't be the case.

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2 hours ago, DickDastardly said:

Yes and no, the foils move the centre of buoyancy way to leeward so a lot more RM can be achieved.  In an IMOCA 60 the strength limits of the one design rig serve to limit the amount of RM any IMOCA boat can develop so in that case yes, keel RM becomes less relevant.  In another class without RM limits that wouldn't be the case.

This is the IMOCA thread.  

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On 9/8/2018 at 2:28 AM, ctutmark said:

open 60 keels are set with the pivot angled up towards the bow. Over the last 6 years this angle has continued to increase. The keel fin is vertical and can see the angle in the pic. The leading edge is to the right

erli

While I concede that the leading edge is angled up, I'd be very cautious about using an uncontrolled oblique image as proof. Without access to appropriate photogrammetric equipment or very sophisticated digital technology, to show an angle of 5° or 6° accurately in an image, you'd need to align the camera, keel and boat carefully and identify some datum for horizontal, such as waterline or similar. 

E.g. in the image, the trailing edge of the axle appears to be almost twice the distance from the bottom of the nacelle as the leading edge.

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4 hours ago, RobG said:

While I concede that the leading edge is angled up, I'd be very cautious about using an uncontrolled oblique image as proof. Without access to appropriate photogrammetric equipment or very sophisticated digital technology, to show an angle of 5° or 6° accurately in an image, you'd need to align the camera, keel and boat carefully and identify some datum for horizontal, such as waterline or similar. 

E.g. in the image, the trailing edge of the axle appears to be almost twice the distance from the bottom of the nacelle as the leading edge.

Maybe you view this as fake news that doesn't fit your theory but here you go:

https://www.seahorsemagazine.com/24-content/august-2013/134-leading-edge

 

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On 9/11/2018 at 12:42 AM, ctutmark said:

Maybe you view this as fake news that doesn't fit your theory

What is it about "While I concede that the leading edge is angled up…" that represents "fake news"? The Seahorse Magazine article is a good reference, thank you.

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20 hours ago, bushsailor said:

Anyone got any info pictures of the foil bearing systems used in these boats?

Cheers

+1  I'd personally pay money to see some interior images around the foils.

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Not bad to do a qualify trip of 1200 miles the 6th time out on the water.

Diraison is a 07 design Finot Conq

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12 hours ago, southerncross said:

Found this.  Sorry. No time for a translate.

 

 
TIME FOR OCEANS, THE NEW 
IMOCA PROJECT BY STÉPHANE LE DIRAISON
 
 
. TIME FOR OCEANS is the new IMOCA project of skipper Stéphane Le Diraison. A program lasting three years until the Vendée Globe 2020 and dedicated to a universal and unifying cause: the necessary protection of the oceans.
Bouygues Construction, Suez and the City of Boulogne-Billancourt,  already strongly sensitized to this cause, are the first three partners, private and public, who support Stéphane and join the TIME FOR OCEANS program.
. Mid-September, Stéphane LE Diraison's 60-foot TIME FOR OCEANS (a 2007 Finot-Conq plan) will sail in its new colors. He will start the prestigious Route du Rhum-Destination Guadeloupe on November 4th in Saint-Malo.
 

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