Alekstar A-38 Express Cruiser

[Omeron]

Thanks for the explanation. I understand that the boat is not designed for IRC, that is perfectly ok. But are you saying that, rotating the keel about its vertical axis is declared in IRC rating application, and IRC accepted it without any problem and issued a certificate in accordance with this. I think this is very interesting and opens a completely new discussion about such a keel.
I wonder what kind of penalty is imposed because of this.
As far as ı am concerned, changing the angle of attack of a fin keel is a major,major modification and cannot be overlooked just because the center of gravity of the keel is not changed.
The purpose of the keel is to provide lift as well as stability. And changing the angle of attack is probably the most pronounced action in terms of changing lift characteristics, is it not?
Also, by changing this angle and thereby improving lift, you are also creating dynamic forces which otherwise would not be there, which in return would change stability and in return change the heel angle and in return change the center of gravity of the keel, etc etc.
I am very curious as to how IRC treats all that.
This may actually deserve a thread of its own.

[AlexMorozov]

As I already mentioned she is cruising boat and not IRC optimized, but this type of keel is not against the rules, as the centre of gravity NOT change his position at all, as rotating of keel around vertical axis, which pass via the CG of keel and bulb. The angle is rather small 0-5 degr depends of heel and practically not change the stability of boat.

[Guillermo]

Alex,
what are the loading conditions for the two stability curves of the A-38?

Cheers.

[AlexMorozov]

One with water ballast another one without.

[Guillermo]

But sided water ballast cannot produce an origin centered symmetric righting arms/moments graph....

[AppleNation]

Notice that there is a "special" on the website!

Imagine like the rest of the boat building world you are struggling to sell boats.

Have any been bought?

[AlexMorozov]

It is clear that with water ballast righting moment is better before 90 degr.
2 boats in order and now we put for sale the demoboat (hull #1) which used for presentation in Spain during 2008. Now it is not good time to build and sale the boat for any builder, but fine for customer, who do not like to pay twice price for Class 40 boat, but wish to get good platform for fast cruiser.

[Guillermo]

Alex,
the curve you have plotted for the water ballast condition is impossible if ballast is on the side. It could be true only with a centered ballast.

Cheers.

[AppleNation]

Originally Posted by AlexMorozov

.... but fine for customer, who do not like to pay twice price for Class 40 boat, but wish to get good platform for fast cruiser.

Yes but you're not selling a boat like the class40 boat. There is no A-38 class.

I think if your premise is that you are competing with a class40 then you need to rethink your business plan.

Your competition is other racer/cruisers of that length.

Cheers.

[Omeron]

What do any of you say about rotating the keel fin about its vertical axis, changing the lift it creates, and this being not an issue by the rating offices.

[AlexMorozov]

I already mentioned and repeat again that A38 is fast cruising boat and Class40 is just closest boat from racing team, however A38 is inside the class40 rules, see http://www.class40racing.com/.
Re stability graph, please read the ISO standard, how draw the curve for water ballasted boat, the water ballast is calculated as "crew action" depends of the heel. The stability curve is correct.
The lift by keel is not calculated and restricted by rules (CE), the stability is not changed due to rotating of keel around the vertical axis, already mentioned before.
Nobody compete with Class40, you just have the fast cruiser with same or better performance then similar racer, but with more comfort at reasonable pricing, nothing more. If somebody is pure racer, then go to class rated racing boats.

[AppleNation]

Not trying to have a go at you Alex... I was just asking questions and pointing things out to help you.

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

[AlexMorozov]

Thank you, if somebody need to be in class40, no any problem to fit fixed keel, the boat just loose some degrees of tacking angle, and it is all, you will have the same performance on any other courses. Everybody knows that such wide boats is not "tacker", but downwind flyer, same as Mini650 or others. If you are thinking about IRC racing, then a lot of boats optimized for this rules, Archambault-40, First 40 and many many others, where the racing round the cans is about 40% is tacking against wind. But the ocean racing (or cruising) is mostly broad reach or down wind running and each class of boat is build to purpose. I think so.

[TeddyDiver]

Originally Posted by Guillermo

Alex,
the curve you have plotted for the water ballast condition is impossible if ballast is on the side. It could be true only with a centered ballast.

Cheers.

I think it's a curve to leevard only with weather side water ballast???

[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...