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Limit of positive stability! #14339
12/30/12 11:28 AM
12/30/12 11:28 AM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Ok looks like PIYA is getting race clubs to enforce the limit of positive stability here in the North West. We had a sport boat go down a couple of years ago in a long distance race and now every one is scrambling to cover there ass.

Can we post the actual LOPS on the specs page so race organizers stop hounding me. I did my calculation measuring the boat and find Vampire within spec for serious of shore racing. But it's very close to the 110 cut off.

I know the Chicago Mac guys worked on this the same time we had our accident. I was just wishing it would go away.

I feel very confident in the boat and love the way it handles in big winds. Any one who has not surfed the boat in 40+ Knt winds should try it. It's a blast.


Vampire #18 Don
Bite Me
Re: Limit of positive stability! [Re: Vampire] #14340
12/30/12 12:18 PM
12/30/12 12:18 PM
Joined: May 2007
Posts: 2,586
Portsmouth, RI
Rhapsody #348 Offline
Past J/30 Class President
Rhapsody #348  Offline
Past J/30 Class President
Joined: May 2007
Posts: 2,586
Portsmouth, RI
I'm not sure if there is an official measurement recorded in the J/30 records. I did look on the US Sailing ORR page and extracted the following data listed for stability index.
Cert # Yachtname Sail # Class Design Stab Index Disp Flotation VPPDate Offsets Dat Name
40458 AWESOME USA-243 J-30 JOHNSTONE, ROD 98.3 7056 1985-6-25 4/18/12 11:05 am US9190.OFF US40458.dat
41435 CIRCUS USA-26219 J-30 JOHNSTONE, ROD 97.0 6704 Sistership or Class Avg Inclining 4/18/12 11:10 am US9190.OFF US41435.dat
40855 FALCON USA-6019 J-30 JOHNSTONE, ROD 101.5 6994 1984-6-21 4/18/12 11:08 am US9190.OFF US40855.dat
40777 INNISFREE USA-145 J-30 JOHNSTONE, ROD 98.3 7056 1985-6-25 3/1/12 10:44 pm US9190.OFF US40777.dat
41054 MADCAP USA-358 J-30 JOHNSTONE, ROD 97.7 6980 Sistership or Class Avg Inclining 4/18/12 11:09 am us9190.off US41054.dat
41054 MADCAP USA-358 J-30 JOHNSTONE, ROD 97.7 6980 Sistership or Class Avg Inclining 4/18/12 11:09 am us9190.off US41054D.dat
42185 RAFIKI USA-6019 J-30 JOHNSTONE, ROD 101.3 7008 1985-6-25 4/18/12 11:15 am US9190.OFF US42185.dat
41020 SALACIOUS USA-30510 J-30 JOHNSTONE, ROD 98.3 7056 Sistership or Class Avg Inclining 4/18/12 11:08 am US41020.dat

Re: Limit of positive stability! [Re: Rhapsody #348] #14346
12/31/12 11:30 AM
12/31/12 11:30 AM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Ok thank you but we need the limit of positive stability. This is the stability index.
I understand one is used to determine the other with some variables.
They are quoting ISAF offshore as the route document but when you drill down to the bottom you come to a ISO 12217-2 requirement and there is no calculation?
There used to be one on US Sailing but now the link is dead?
There is a very good article on why the whole calculation is flawed from a US Navy Prof at anapolis here.
http://www.usna.edu/Users/naome/phmiller/phmSAS03.pps

So with the variables and lack of the calculation we are scratching our head.
We are to take into account draft of hull not the whole draft and the beam and free board.
This was how I came to my number but I was hoping the class would have something with all the variables filed in so we can quote the class site. Has J/Boats ever rolled a boat to check the numbers? Yachting monthly did this recently and it was surprising to see a similar era yacht in size and shape needed a small nudge from the crane to right itself from inverted?

Does any one still have the proper calculation? I will follow this up with PIYA NW who are imposing this restriction. Just as a note they have changed the angle by over 10deg in less then three years so this tells me they don't know what is safe either.



Vampire #18 Don
Bite Me
Re: Limit of positive stability! [Re: Vampire] #14347
12/31/12 11:33 AM
12/31/12 11:33 AM
Joined: May 2007
Posts: 2,586
Portsmouth, RI
Rhapsody #348 Offline
Past J/30 Class President
Rhapsody #348  Offline
Past J/30 Class President
Joined: May 2007
Posts: 2,586
Portsmouth, RI
I'll contact Rod Johnstone and see if he has any information on this.

Re: Limit of positive stability! [Re: Rhapsody #348] #14348
12/31/12 11:43 AM
12/31/12 11:43 AM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Thank you. Thats great.


Vampire #18 Don
Bite Me
Re: Limit of positive stability! [Re: Vampire] #14349
12/31/12 12:12 PM
12/31/12 12:12 PM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
This may help.
I just found an email from one of the north west boats that includes an email from Alan Johnstone. It quotes the IMS LPS for The J30 at 105.2 deg and then he ads the variables I spoke of earlier of cockpit and deck and he says it's 10-15 deg more.

I will attach the email.
But we should still get this on the page and locked down from J/Boats so people can get back to racing.


Vampire #18 Don
Bite Me
Re: Limit of positive stability! [Re: Vampire] #14350
12/31/12 12:19 PM
12/31/12 12:19 PM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
This is the reply from J-Boat tech. Makes the J-30 a range of positive stability 115.72-120.98 Right where we thought. Now what!!!!

----- Original Message -----
From: "R. Alan Johnstone" <alj@J/Boats.com>
To: "Tony Brogan" <tony@
Sent: Monday, February 07, 2011 7:58 AM
Subject: Re: JBoat Tech Message


> Tony,
>
> The IMS LPS for the J/30 is listed as 105.2 degrees in the 2004 US Sailing
> Publication "Performance Characteristics Profile of the IMS Fleet".
>
> IMS does not take into account the deck and cockpit shapes in their
> assessment. The J/30 actual LPS when this structure is included is
> approximately 10-15 degrees higher than the IMS number.
>
> Sincerely,
>
> Alan Johnstone
> J/Boats, Inc.
>
>
>
> On 2/5/2011 5:19 PM, Tony Brogan wrote:
>> email: tony@
>> realname: Tony Brogan
>> subjectfield: Positive stability
>> mesg: What is the positive stability of a J-30
>>
>> ==================================
>>
>> REMOTE_HOST=
>> REMOTE_ADDR=70.28.245.51
>> HTTP_USER_AGENT=Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0;
>> Trident/4.0; GTB6.6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0;
>> OfficeLiveConnector.1.3; OfficeLivePatch.0.0; .NET CLR 3.5.30729; .NET
>> CLR 3.0.30618; .NET4.0C)
>> REMOTE_USER=
>>
>>


Vampire #18 Don
Bite Me
Re: Limit of positive stability! [Re: Vampire] #14371
01/07/13 04:32 PM
01/07/13 04:32 PM
Joined: Oct 2009
Posts: 369
Squamish, British Columbia
NaturalHigh Offline
Senior Member
NaturalHigh  Offline
Senior Member
Joined: Oct 2009
Posts: 369
Squamish, British Columbia
I question how the local clubs plan to "enforce" this. There are plenty of boats in the PNW that don't have any published LPS numbers. Given the way our clubs operate, I would think an email directly from the designer would suffice.

Re: Limit of positive stability! [Re: NaturalHigh] #14424
01/19/13 09:44 AM
01/19/13 09:44 AM
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
Vampire Offline OP
Past Pacific Northwest District Governor
Vampire  Offline OP
Past Pacific Northwest District Governor
Joined: Nov 2010
Posts: 147
Vancouver, BC, Canada
You may be right Scott. I have been talking to PIYA and they don't even understand what they are asking. They are confusing LOPS and stability index. When asked they could not even explain it. Yet they want us to follow it. Swiftsure has already made it suggested again yet PIYA said they wanted it? Any way this letter from the builder will put us in the good and the issue will be a dead one for the J30 fleet here.


Vampire #18 Don
Bite Me

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