Alekstar A-38 Express Cruiser

[TeddyDiver]

Originally Posted by Alik

Pink curve is with water ballast? If so, water ballast tank(s) should be in the bottom, otherwise impossible to get increase of GM. But then, the curve in inverted position looks strange...

What is strange is the curve being at zero GM with 0 and 180 deg.
GM being increased/decreased (depending how much the boat is heeled, + when 0-90,- 90-180,+ 180-270,- 270-360 to make circle full), is obvious when CG isn't anymore in the centerline..

Hmm.. wasn't actually thinking anymore straight with the degr of heel..it should be little more or less.. or something Anyway Happy New Year to all!!!

[Guillermo]

I will have a look at ISO rules, as Alex indicates, when I come back to work (the 7th), to find out what it says there. In the mean time I find impossible a sided ballast tank can produce GZ or RM curves being null at 0º and 180º

Cheers.

[Alik]

There are factors changing stability curve when water ballast is taken:

1. Change of slope of curve (especially obvious at 0 and 180) due to change of VCG.
2. Shift of curve due to asymmetrical load, this will result non-zero GZ at 0 and 180.

As Alex said, factor #2 is neglected on the curve plotted.

But still there is a question on factor #1 - the curve does not show behaviour typical to change of VCG.

Really interested what curve is that, maybe designer can give comments.

[AlexMorozov]

Albert, may be you right, looks not very clear, I have the curves from designer and can explain only as I understood: As per ISO the water ballast is movable ballast and count as "crew weight". At heel 0 degr (no ballast aside, no crew aside), no static heel. Then the heel increase and ballast move (pink line), after about 4-5 degr, the ballast aside and all further moments are counted with ballast on one side. So, in position about 130 degr, the moment with ballast aside is lower then without ballast.
The pink curve is with weather side ballast only, the worst condition in inverted position.

[AlexMorozov]

I think that pink curve is right at 180 degr, but at 0 moment the static heel to be -5 degr. It is correct, but it is depends how count and draw the curve with movable ballast as per ISO standard.
Designer told me that this is in order with ISO, but I will ask again after 12/1. Happy New Year to all.

[JesperW]

Originally Posted by AppleNation

As for Class40 compliance.... How does your rotating keel fit with the Class40 rule of a fixed keel ?

I just felt I had to make a comment here. I have sailed this boat, and I have to agree with Alex, he is quite clear in stating that the design is not meant for racing, much more for fast and comfortable cruising.

There are many small reasons why the A-38 is not ideally suitable for racing, so myself I would recommend looking elsewhere if that's your intent.

/jesper

[AlexMorozov]

Yes, guys, you were right. After 6 months of "light use" the boat, the "bugs of new boat" were growing to "construction and engineering problems" in geometrical proportion. After 1 year ownership we had no more possibility to pay every month this "floating maintenance bill" and sold the boat at cost of materials to French sailor, who will rebuild her in next year. It is pity that good concept was not support by proper engineering and building quality from Kompan Marine.

[Omeron]

Sorry to hear that. May be you would like to share with us, what kind of problems arose, so that we can learn more about weak spots of a boat. Like the classic story, the best way to design a good shoe starts by having a number of wornout shoes...

[AlexMorozov]

Fine exterior design and good sailing ability (not optimized for IRC racing), but not practical salon layout, poor quality of builder in details - hydraulic system, construction of rudder blades, steering mechanism, engine installation and and sound isolation, interior assembling quality, shaft leg installation, non professional wiring, and other bugs. I sure that if the same boat was built in Holland, for example, she would be good example of fast cruiser.

[Godzilla]

Is this what you are talking about?

http://www.kompanmarine.ru/?lang=en