SailNet Community - View Single Post - Interesting Sailboats
View Single Post
  #2741  
Old 05-12-2012
EricKLYC's Avatar
EricKLYC EricKLYC is offline
Senior Member
 
Join Date: Feb 2011
Location: Antwerp, Belgium
Posts: 468
Thanks: 16
Thanked 5 Times in 5 Posts
Rep Power: 4
EricKLYC is on a distinguished road
Re: Pogo 12.50 - JPK 38

PHP Code:
First of allto let things clearnot properly to you but to alllet me say that I love the Pogo designThat design is associated with proposing a boat with amazing performances at a price people can buy (at leat some:D). 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 limitsspecially 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 conditionseven considering speed alone
No doubt, Paulo. If the boat has met most of our expectations so far, it’s is only because of our own and very personal sailing ambitions. Or because we have not yet had enough experience with it
But there’s absolutely no way this kind of design will please every sailor. Different programs, different priorities, different tastes, that’s what makes this thread so interesting to me

PHP Code:
Those polar consider flat waterThe Pogo type design will not have a problem going fast upwind on flat watereven if a bit more off the wind
These VPP’s and polars are indeed very theoretical. It seems clear to me that we will never be able to keep up with an X41 upwind, even in flat sea conditions. If we ever do, there will be champagne for everyone

PHP Code:
The problem of those designs has to do with going fast upwind with waves

The bigger the waves the worse is the performanceThat has to do with wave drag that is increasing exponentially in that boat when crashing through wavesmaking it lose more power than the one the boat can generate over other type of boatsOf 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. 
Our very first experiences in strong wind-against-tide conditions tend to confirm this. It needs quite hard work at the helm to keep the boat comfortable.
But we think we still have a lot to learn, about trimming as well as about steering, especially upwind. I’ll be glad to post the data as soon as we have become sufficiently confident.

PHP Code:
I have saw that 40 class racersthat are a much more powerful boat than your Pogohave not good performances when they got nasty weather upwindOn 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. 
These kinds of boats perform very differently in different kinds of races. No wonder, they are after all “open” designs resulting from so called “box rules”. But I still cannot explain why the 8.50’s performed so badly in the Transquadra and 10.50’s didn’t even compete, while the 6.50’s keep on killing everybody in the Mini Transat, since both are mainly downwind races.

PHP Code:
Regarding this I have to disagree with youA narrow foil with a torpedo has a better performance than your swing keelIt 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:

[
IMG]http://i804.photobucket.com/albums/yy322/Paulo_Carvalho/Vega/hhh-1.jpg[/IMG]

This is a similar keel to the one that you have in your boatHighly efficient for a swing keel but not a match for a fixed top keelThat is why for the same ballast the Pogo has to have a bigger draft on the swing keel (kell downthan on the fixed keel
I fully agree that in order to achieve the same CG a swinging keel has to be deeper than a fixed T-keel and that the slimmer design will indeed result in a larger wet surface and therefore more drag. I only hope the higher aspect ratio will compensate this with less drift upwind.

The point I wanted to make is that a keel with a composite foil and a lead ballast (as Structure does with the canting keels) will perform better than exactly the same design made in cast iron (as most other builders do).

JPK also offered this kind of high-tech, high-aspect composite/lead swinging keel option, but they have now dismissed it. I wonder why, because the ability to switch from maximum performance to minimum draft in only minutes can be a very valuable option in high tide and often shoal sailing waters like ours.

PHP Code:
Regarding the weight of your boatI would very much liked to see its "real" weight because I have some difficulty in believing in the 5500Kg that are given by the factoryThe 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 FinotNormally the finished boat has more weightnot less
I also wondered about these differences in given weight. Could this be because of different standards when considering weight and load (with our without certain items) between the architect and the builder, or are these measures always well defined ans standardised?

In my experience Structures has always been very honest with all their information. And I believe the infusion building technique results in much lesser weight differences than e.g. hand lay-up does.
But I will certainly inform you whenever I get the opportunity to weigh our boat. And of course only after our “weight watcher” Jim has removed all the completely useless gear Mum and Dad have accumulated

PHP Code:
Regarding that less comfortable motion against the waves due to a "pendulum effect" I believe you are wrongWhen 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 stabilityThat 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;) 
In any circumstances the boat has absolutely no tendency to roll, I can confirm that.
I only thought the 3m deep keel could induce more pitching when sailing upwind and against waves. I’m happy to hear this is no real issue, one more lesson learned Paulo!

PHP Code:
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;). 
I fully agree that the JPK looks like a wonderful performance cruiser and that it will make many a sailor very happy.
That could even include me, if only it hadn’t an interior with so many doors Although it’s easier to replace doors by curtains than the other way


Best regards,

Eric

P.S. My first try at "multi quoting", I obviously didn't get it all right...

Last edited by EricKLYC; 05-12-2012 at 07:30 PM.
Reply With Quote Share with Facebook