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  #2461  
Old 05-10-2012
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Re: Interesting Sailboats

Too fine entries, combined with too wide sterns ,eliminates directional stability, and make a boat hard to control downwind. Such bad hull balance is a common curse on cruising boats.
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  #2462  
Old 05-11-2012
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Re: Interesting Sailboats

Quote:
Originally Posted by Brent Swain View Post
Too fine entries, combined with too wide sterns ,eliminates directional stability, and make a boat hard to control downwind. Such bad hull balance is a common curse on cruising boats.
I don't understand what you mean. These two factors are not independent and have to be associated with a properly designed hull. Maybe you are talking about the design of old IOR boats that had a big beam at the middle of the boat and fine entries and small transoms. I tend to agree.

But I am talking about modern hull designed and boats with the beam brought aft. Regarding those you cannot have more directional stability than on an open 60 or a Class 40. That is one of the main design requirements on those boats and they are being perfected along 40 years.

Directional stability is fundamental to solo sailing where you leave the boat on autopilot even on the middle of a storm and keep tacing or have to go forward (leaving the boat on autopilot) with the boats going ant racing speeds.

Directional stability and a stable platform while sailing is probably the main reason those boats are so beamy. If speed was the only concern the boats would be more narrow, along the lines of VOR boats. And of course, those boats have fine entries.

Regards

Paulo
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  #2463  
Old 05-11-2012
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Re: Interesting Sailboats

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Originally Posted by PCP View Post
I am talking about modern hull designed and boats with the beam brought aft. Regarding those you cannot have more directional stability than on an open 60 or a Class 40. That is one of the main design requirements on those boats and they are being perfected along 40 years.

Directional stability and a stable platform while sailing is probably the main reason those boats are so beamy. If speed was the only concern the boats would be more narrow, along the lines of VOR boats. And of course, those boats have fine entries.
I could not agree more.

The 12.50 has quite fine entries, a disgraceful 4m50 and very aft beam, but an extraordinary directional stability with its twin rudders.

To illustrate this: we once started the autopilot at +10knots on a beam reach and it took us several minutes to realise the pilot piston was in fact disengaged from the steering mechanism (we do this on purpose when steering ourselves, to get more feeling at the helm). The boat was perfectly steering itself, as if it were a long keeler sailing upwind.

Best regards,

Eric
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  #2464  
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Pogo 12.50 - JPK 38

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Originally Posted by EricKLYC View Post
Yes we do, Paulo. Let me know whenever you would be in the neighbourhood of Nieuwpoort and we will have fun together .
Yes, I would like to meet you and do that. Maybe next year on my cruising spring voyage (by car) I would do that. Anyway I love Flemish country and cities. I have also friends there.

First of all, to let things clear, not properly to you but to all, let me say that I love the Pogo design. That design is associated with proposing a boat with amazing performances at a price people can buy (at leat some). Other type of fast boats with more ballast ratio and more narrow are more expensive to build and also more difficult to sail near the limits, specially downwind.

That does not mean that the boat is perfect and has not weak points and strong points neither it is the best answer to all sailors or all sailing conditions, even considering speed alone.

Quote:
Originally Posted by EricKLYC View Post


..
I ‘ve seen VPP and VMG figures that suggest the Pogo 12.50 should even be able to keep up with a racer such as the X41 upwind (fastsailing.gr - The crazy polar diagrams - VMG at all angles - The yacht , Stunningly fast!).
When I look at our actual upwind GPS tracks on the screen, I find this very hard to believe. But as we learn, especially about trimming, we definitely make progress. Who knows, one day… As soon as we can collect reliable data and have made sensible comparisons on the water, I’ll certainly let you know....

But as Paulo stated, even apart from handicap considerations (horrible for any Pogo, designed without any consideration for any handicap rule), racing results indicate we will very probably never be able to stand out in an upwind course.
Those polar consider flat water. The Pogo type design will not have a problem going fast upwind on flat water, even if a bit more off the wind.

The problem of those designs has to do with going fast upwind with waves.

The bigger the waves the worse is the performance. That has to do with wave drag that is increasing exponentially in that boat when crashing through waves, making it lose more power than the one the boat can generate over other type of boats. Of course the big power needed to go on those conditions and the big wave drag make also the boat very uncomfortable in that particular case.

I have saw that 40 class racers, that are a much more powerful boat than your Pogo, have not good performances when they got nasty weather upwind. On the last "around NZ race really nasty weather lead to the abandon of the Pogo 40 class racer that was having a bad performance, beaten even by narrow old boats, but that were really very bad conditions. Other boats with the same type of design also experienced difficulties and an overall bad performance. The guys on the Pogo were good, they are one of the main racing teams on that side of the world and the only one that races (for years) with a 40class boat on ocean races. It is the same team that had made several Sydney-Hobart with that boat.


Quote:
Originally Posted by EricKLYC View Post

Concerning B/D ratio, I think the draught should also be taken into consideration. There must be a big difference in righting moment, and thus in both security and power, between the same ballast weight in a 2m deep massive cast iron keel or in a 3m deep composite construction with all the weight in lead and in in the bottom section. As far as I know only Structures is offering this latter kind of build for cruisers and I understand they want to keep the details of this design for themselves.

On the other hand, the much lower centre of gravity will act even more like a pendulum which, together with the overall light weight design, should result in a less comfortable motion against waves. That’s probably also why we should not try to sail close-hauled but concentrate upon keeping up both speed and power by bearing down a little.
Regarding this I have to disagree with you. A narrow foil with a torpedo has a better performance than your swing keel. It offers less drag (less surface) and it brings the CG lower.

Have a look at the picture on the JPK 38. The keel CG is marked on each one and you can see that is remarkably lower on the torpedo keel:



This is a similar keel to the one that you have in your boat. Highly efficient for a swing keel but not a match for a fixed top keel. That is why for the same ballast the Pogo has to have a bigger draft on the swing keel (kell down) than on the fixed keel.

Both boat with the fixed keel with about the same draft have the same ballast (1900kg) but the JPK is smaller and therefore lighter.

Regarding the weight of your boat, I would very much liked to see its "real" weight because I have some difficulty in believing in the 5500Kg that are given by the factory. The designer gives it more weight and I would still be waiting to see a boat that could be made with less weight than the one that is given by a designer like Finot. Normally the finished boat has more weight, not less.

I say this because the difference in weight between the JPK 38 and the Pogo 12.50, as stated by the factories is only 500kg. Being the ballast, the constructions techniques and materials the same I have some difficulty accepting that a substantially more beamy and several ft longer boat would have such a small difference. About a 1000kg difference should seam more natural to me, considering they are both top builders that use race boat technology.

Regarding that less comfortable motion against the waves due to a "pendulum effect" I believe you are wrong. When there are waves there is wind and the boat will be strongly "tied" to a side by the wind force and there is no wave that is going to make it roll from one side to the other. As I have explained the substantially bigger beam on the Pogo will make him less comfortable on waves due to a superior wave drag.

What you saying related with the pendulum effect can happen downwind but not in a boat like the JPK that has already a considerable beam and a lot of form stability. That would happen surely on the Aspect 40 if the crew is not on top of it and by crew I don't mean a single guy

That could be a problem on those racers (or very fast performance boats) narrow and with almost 50% of ballast on a very deep keel. As I have said already, that associated with the shape of the hull (that permits more heel before a greater hull stability) is the reason those boats are tricky to sail downwind. They can go very fast but they need a crew to balance perfectly the boat and not allow that rolling movement.

The JPK 38 has not only a considerable beam but also a hull shape that don't allow great angles of heel, like the Pogo. The JPK 38 is really a mix between the hull shape of a Pogo and that for instance of an A35, trying to get advantages from both sides. Off course it will not be as good downwind as a Pogo, but will be more comfortable and better upwind (taking into consideration the different sizes of the boats) or at least is how I see it.

Regards

Paulo
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Last edited by PCP; 05-11-2012 at 05:45 PM.
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  #2465  
Old 05-11-2012
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Re: Aspect 40

Quote:
Originally Posted by PCP View Post
The boat weights only 4400kg and almost half is in ballast meaning that hull will only weights about 2000kg.
What makes this boat interesting to me is they have created a really light family cruising/racing boat, utilizing carbon fiber to a high extent, for example stanchions, toilet seat, mast and boom (of course!) and even the shrouds are carbon fiber (twice as strong as rod but only 1/5 of the weight!

Despite it's narrow hull, they say it starts planing in about 16 knots wind on flat water, with boat speed around 12-14 knots and close to 20 knots in 20-25 knots of wind. I don't know how stabile the boat is in these conditions. I will sail on my brothers boat in a regatta next week and I think there will be an Aspect 40 attending as well. I will try to speak to the owner of the boat to see what they say.

//Mr W
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  #2466  
Old 05-11-2012
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Transat AG2R

Nice images:



A bit more than two days to the finish and Morvan is really the king of the Figaro, at least in what regards Transats. Tabarly has made a great race but I don't think he can catch the King. I wonder why Morvan have never tried the vendee Globe?
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  #2467  
Old 05-11-2012
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Re: Interesting Sailboats

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Originally Posted by Faster View Post
Here's an interesting look at the new Ker 50... not a cruising boat, to be sure, but what I find fascinating here is the very antithesis of the slab sided chined hulls from the likes of JPK and others of late....

Hei Faster, when you posted this I thought that was a some year's old 50, but you are right it is a brand new boat, but not a 50, it is a 51 ft boat, so new I did not knew about it.

Great boat and I bet it is a missile a winner among 50ft racers.

Like all Ker boats it has a big draft and a big ballast ratio in this case “only” more than 50%. The boat weights 6600kg and the ballast is 3575kg, at the end of solid steel machined foil with 3.75m.

Can you imagine the righting moment of that boat, considering it has a beam of 4.8m? To put things in perspective, the new 50ft cruiser from Pogo has a beam of 5.16m, so it is beamier, but 4.8m is a lot of beam on a 51ft and more than is usual on Ker boats.

For instance the beautiful Ker 53 has only 4.20. I have already posted about it. Take a look you are going to like it:

http://www.ker53.com/media/KER53_Brochure.pdf

So this new boat is really a beast of power, power from a huge ballast ratio and big draft, power from a beamy hull designed to heel and take advantage of all that ballast.

I want the see the racing results of this one. The boat is going to race the Round Gotland, Voile de St Tropez, Middle Sea Race and Sydney Hobart.

To make things more interesting the boat has an incredible big bowsprit for the geenaker and asymmetric spy, with 3.2m and a voluminous bow, to give buoyancy and make sure the boat will not go underwater under the power of that big asymmetric spinnaker.

Varuna, that is its name, was built in Germany. It is made of carbon and Nomex honeycomb and they used a unusual technique: For each part, each major component was made a CNC-machined mold. The components do not need to be laminated. They are glued together with a very precise fit with less material consumption and less weight.

What a boat!!!!! Thanks for calling my attention to it.















Regards

Paulo
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Last edited by PCP; 05-11-2012 at 09:29 PM.
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  #2468  
Old 05-12-2012
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Jason Ker: Cruising boats

Innovative architects like Ker that can make winning racers can also make winning cruisers and put to cruising service all that knowledge that makes their boats win, now used for a different purpose.

The fact that Ker is on the other side of the world for most builders does not help and he became a major architect because his boats were winning a lot. Just look at this list of victories and that with very few boats on the water:

Results | Ker Yacht Design

So even being faraway some European boat builders started to use their services. Curiously the first one was Southerly and Ker helped them to make a cruising boat different from all others and to make their cruising line, swinging keel and all, a truly contemporary line. The design has already some years but it looks like a new design. Beautiful boat:

http://www.northshore.co.uk/videos/2/iphone.mp4








Then on his part of the world Sydney call him for the design of the 37 and the 43. Also beautiful boats. Here the 43GTS:







And now it is Salona that seems to have made him its official designer. He has been collaborating in the design of the keels of previous hulls still used (35, 38 and 41) and has designed the new Salona 60:






The Salona 60 is not a top performance boat, it is more intended for cruising and it is not a very light boat even so look at this Polar:




The boat can make with 4K wind 6.5K speed, with 6K wind 8.5K speed and with 10K wind 10K speed and that is a Polar in loaded condition

In 2 to 4 years he would probably be designing for them a new 45 and then the rest of the line. Ker adapts perfectly to the Salona philosophy : fast performance cruisers, not too beamy, not too narrow (by modern standards) and with a bit more ballast ratio than the French boats.

I cannot wait to see those boats

Regards

Paulo

Last edited by PCP; 05-12-2012 at 07:58 AM.
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  #2469  
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Baby Celeste

Hi Paulo,

Here is a new design, again swedish

The Baby Celeste by Gabriel Heyman:






Absolutely stunning if you ask me! Loa 9,25 m, Beam 2,28 m, Draft 2,00 m (lifting keel), light displacement 1,550 kg, ballast 650 kg, SA upwind 40,8 sqm, Asy 42 sqm. First boat will be built later this year. It´s a shame it doesn´t fill my needs

Mr W
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  #2470  
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Baby Celeste

What a baby

I agree, absolutely beautiful. Thanks for posting

Regards

Paulo
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