Scramble
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Looks like a CFD calculation for the attachment of the bulb to the keel, but the rest of the grid is not fine enough.
what keel is it?
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Schakel
Dayboat sailor
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This. Interference drag. Refer to Fig 2 and explanation above it on page 78 of this article:
https://www.ericwsponberg.com/wp-content/uploads/keel-and-rudder-design.pdf
floater
Super Duper Anarchist
except its lead.
Tacoma Mud Flats
Have star, will steer by
The missing 2010 Etchells Mould 11 build-to CAD solid ?
It's just a NURBS surface. The shape is more complex in the joint so there's more control points there, which is showing up in the visualization. Meshes for CFD are much denser and more regular.
Matagi
Super Antichrist
It's not.
KS post from 7 November in the respective thread:
'At the moment there is only one keel design, standard cast iron keel with cast iron bulb at 2.25m. There is strong initiative to have performance version with lead bulb at 2.55m (and -250kg) . We are keen to do it once the base options get sorted as this keel will - with carbon mast - reduce weight of the boat for another 300kg. '
So that's probably going to happen in the future, but not yet.
floater
Super Duper Anarchist
well, thank you. and apologies @bohme. As part of my penalty for getting it wrong on the internet - I did a little research into "just what is the difference" between a cast iron and lead bulb (read at your own risk, lol). Densities and spot prices:
- Cast iron: 7,860 kg/m3 (1.84 $/kg)(1,550 kg ballast) = $2,852
- Lead - regular keel (11,343 kg/m3 (2.28 $/kg)(1,550 kg ballast) = $3,534
- Lead - performance keel: 11,343 kg/m3 (2.28 $/kg)(1,300 kg ballast) = $2,964
- Depleted Uranium - gone nuclear: 19,050 kg/m3 (130 $/kg) = $169,000
Of course - this isn't right. Because the notion is that only the bulb would be lead, not the entire strut. So the difference in cost between cast iron and lead actually doesn't seem to amount to much. So, it must be the difference in fabrication cost - perhaps simply time - that makes the difference in effort between a cast iron and lead solution.
It would be interesting to develop a curve of fabrication cost (or total cost) vs. performance gain for keel 'option'. I wonder. Oh the joys of being a boat builder - engineer, economist, sailor?
Kristian Seascape
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Well, some comments:
- lead is more expensive, not just raw material, but material after taking into account the costs of casting, environmental stuff, tracking of material, waste disposal, etc.
- lead has 30% less bigger density, so lead bulb can be 30% smaller for same weight, reducing overall drag.
- the strut has to be different, either going to high modulus cast with hollowed fin or doing some other methods like casting a H strut and encapsulating it in GRP hydro body. This is important to lower vertical center of gravity and allowing you to either have more stability or having equal stability with less weight.
- lead is more expensive, not just raw material, but material after taking into account the costs of casting, environmental stuff, tracking of material, waste disposal, etc.
- lead has 30% less bigger density, so lead bulb can be 30% smaller for same weight, reducing overall drag.
- the strut has to be different, either going to high modulus cast with hollowed fin or doing some other methods like casting a H strut and encapsulating it in GRP hydro body. This is important to lower vertical center of gravity and allowing you to either have more stability or having equal stability with less weight.
Matagi
Super Antichrist
I think it's hard to tell. The main unknown factor is your buyer's willingness to pay the premium or rather take the cheaper option. You can have the Roma with standard rims, but who does that, right
?On the other hand, the larger cast iron bulb might even be the smarter option ratingwise, but that is sth. that remains to be seen.
It might be a good move financially from a builder's perspective to invest into the tooling later (70,000 EUR for the keel, was it?), once your other investments amortized. The moment you announce the 'turbo'ed' version, you have to be prepared though. That's the point when potential buyers will hold back their order and wait for the new version. Old customers might be furious once they realize that they now own the 'Oh-you-mean-the-classic-series' version of what was once the hottest sh*t.
floater
Super Duper Anarchist
I'm just trying to figure out which is more fun: building this new toy, or sailing it? Kristian will have to report back..I think it's hard to tell. The main unknown factor is your buyer's willingness to pay the premium or rather take the cheaper option. You can have the Roma with standard rims, but who does that, right
On the other hand, the larger cast iron bulb might even be the smarter option ratingwise, but that is sth. that remains to be seen.
It might be a good move financially from a builder's perspective to invest into the tooling later (70,000 EUR for the keel, was it?), once your other investments amortized. The moment you announce the 'turbo'ed' version, you have to be prepared though. That's the point when potential buyers will hold back their order and wait for the new version. Old customers might be furious once they realize that they now own the 'Oh-you-mean-the-classic-series' version of what was once the hottest sh*t.
Kristian Seascape
Member
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Gents,
we need a solid but not to pricey base. Going too technical on mast, keel or some other area can and will backfire in a very spectacular way. In no time, boat will be recognized as pricey and too technical for a typical Beneteau customer. On the other hand, they want a list of options to pick from ... Regarding the boat design, it is really a zero sum game. Whatever you can save without too many (or with acceptable) compromise, you can invest into another area where it makes more effort in having a good overall package.
This keel design is quite elaborate one for the given technology. Sam Manuard is a very good naval architect and a smart cookie (has a masters degree in geology and was drilling North Sea for oil deposits before started drawing boats) so he took the challenge of having a rather basic construction method (=cast iron) but optimized it for low(est possible) drag in given scenario. Yes, lead has 30% less volume, but he did a very long bulb (~ 2.1m long bulb is quite interesting) with small cross section to reduce drag.
However, we will not push these new options too soon as we need to get the first boats out, optimize and sort out production methods (it is all fun and games to design and build first one but to churn out boats on time and on quality every 7 working days, that is completely new game).
Investing into high modulus cast iron (hollow) fin is undoubtedly very good but maybe not the most optimal was of doing the performance keel. Not many clients would be willing to cash out roughly 20k (price for keel + amortization of tooling investment). I believe we can be smarter in this department and achieve same result with combining load bearing strut, lead bulb and GRP hydro body, with same overall performance but a fraction of costs. But this is something to discuss in the future...
we need a solid but not to pricey base. Going too technical on mast, keel or some other area can and will backfire in a very spectacular way. In no time, boat will be recognized as pricey and too technical for a typical Beneteau customer. On the other hand, they want a list of options to pick from ... Regarding the boat design, it is really a zero sum game. Whatever you can save without too many (or with acceptable) compromise, you can invest into another area where it makes more effort in having a good overall package.
This keel design is quite elaborate one for the given technology. Sam Manuard is a very good naval architect and a smart cookie (has a masters degree in geology and was drilling North Sea for oil deposits before started drawing boats) so he took the challenge of having a rather basic construction method (=cast iron) but optimized it for low(est possible) drag in given scenario. Yes, lead has 30% less volume, but he did a very long bulb (~ 2.1m long bulb is quite interesting) with small cross section to reduce drag.
However, we will not push these new options too soon as we need to get the first boats out, optimize and sort out production methods (it is all fun and games to design and build first one but to churn out boats on time and on quality every 7 working days, that is completely new game).
Investing into high modulus cast iron (hollow) fin is undoubtedly very good but maybe not the most optimal was of doing the performance keel. Not many clients would be willing to cash out roughly 20k (price for keel + amortization of tooling investment). I believe we can be smarter in this department and achieve same result with combining load bearing strut, lead bulb and GRP hydro body, with same overall performance but a fraction of costs. But this is something to discuss in the future...
Gouvernail
Lottsa people don’t know I’m famous
The new ILCA Centerboard
fastyacht
Super Anarchist
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So here is the ugly truth. Displacement sailboats do not go any faster today in any menaingful way, than they did in 1903. If you race the classic circuit, try to catch DORADE. I know, she is a yawl and yawls are "slow." Good luck catching her to windward in your fancy fiberglass boat with lead keel.
Spending loads of money on all sorts of optimized (=$$$) structural "innovations" in a ballast fin is obviously a losing proposition. Case in point: star boat. Cast iron. 15.5 foot floating waterline. Routinely passes 30 foot modern fin keeled boats going to windward. No I am not making that up. Been there done that.
Oh and the lead thing with enviro stuff" is a shit show in Europe.
Spending loads of money on all sorts of optimized (=$$$) structural "innovations" in a ballast fin is obviously a losing proposition. Case in point: star boat. Cast iron. 15.5 foot floating waterline. Routinely passes 30 foot modern fin keeled boats going to windward. No I am not making that up. Been there done that.
Oh and the lead thing with enviro stuff" is a shit show in Europe.
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That explains the ugliness of the fillets at the root and lack of dillet on the bulb. You want the fillets to have a steep leading and trailing angle.
And to reduce interference drag, you locally reduce the volume of the bulb where the keel joins it. This also helps reduce the VCG of the bulb.
Rasputin22
Rasputin22
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Dillets?! DILLIGAF?
