Viper 640 Class Association Forums

Viper 640 Public Forums => Sailing, Handling, Tips and Techniques => Topic started by: Duncan Adams on November 03, 2010, 06:38:57 PM

Title: GNAV
Post by: Duncan Adams on November 03, 2010, 06:38:57 PM
Hi All,
I am about to fit a GNAV system to my tin rig Viper, I have quite a few of the bits I need but I don't have all the measurements. Can anyone tell me the following:
The measurement from the dec to the top GNAV fitting on the mast?
The length of the GNAV tube?

Thanks
Duncan
Title: Re: GNAV
Post by: Dave Nickerson on November 03, 2010, 08:06:45 PM
Duncan - I'll try to get you the measurement off our carbon mast tomorrow.  I was thinking the distance between the 2 gooseneck fittings is the best I can do since the mast is out of the boat.

The length of the tube is in the Class rules, section 6.4: The length of the tube (without end caps) shall be 122 cm +/- 6 cm

Has anyone put a GNAV on a Viper tin rig before?
Title: Re: GNAV
Post by: Ben Steinberg on November 03, 2010, 08:12:02 PM
the goosnecks measure 39" center to center. 
Title: Re: GNAV
Post by: Darren Gilbert on November 04, 2010, 09:08:27 AM
The Boat I just bought came with a Tin rig and I've been thinking about the GNAV upgrade.  My question is how do you fee the sail through the mast track with another goose neck on it?
Title: Re: GNAV
Post by: Greg Jackson on November 04, 2010, 10:28:47 AM
Quote from: Darren Gilbert on November 04, 2010, 09:08:27 AM
The Boat I just bought came with a Tin rig and I've been thinking about the GNAV upgrade.  My question is how do you fee the sail through the mast track with another goose neck on it?

You'll have to grind and file or mill a new feeder above the gnav gooseneck and add velcro to the sail to connect it to the mast below the gnav gooseneck.

I did the grind/file trick to a replacement Lido 14 mast five or so years ago...
Title: Re: GNAV
Post by: Duncan Adams on November 04, 2010, 07:07:16 PM
Thanks for the measurements.
We have a top fitting that rivets on to just one side of the mast so no need to change any sail feeds. Bit concerned by the strength of the fitting but there is only one way to find out if it's gona work, and if it breaks shouldn't do much damage???
Title: Re: GNAV
Post by: Tim Carter on November 04, 2010, 07:26:20 PM
if it breaks with the kite up in breeze you my say good-by to the rig...  =:0
Title: Re: GNAV
Post by: Ben Steinberg on November 04, 2010, 07:35:32 PM
I know the fitting you're talking about, its cast stainless.  selden spec'ed it for vipers when they tried to get into the boom/gnav game.  It will likely work, but to confirm tims thoughts, sailing with a tin rig is sailing on borrowed time. 
Title: Re: GNAV
Post by: Duncan Adams on November 05, 2010, 06:13:43 AM
Thanks for the tip. We have moved the shroud chain plates out, we also ploughed into a wave last saturday from 17knots with main out and rig stayed up so I hopeful it won't all come crashing down, either way it's insured?!
Title: Re: GNAV
Post by: Lee Shuckerow on November 06, 2010, 03:51:11 PM
Quote from: Duncan Adams on November 05, 2010, 06:13:43 AM
Thanks for the tip. We have moved the shroud chain plates out, we alsoploughed into a wave last saturday from 17knots with main out and rig stayed up so I hopeful it won't all come crashing down, either way it's insured?!
finally had our viper carbon rig payed for. It broke in February. Make sure you have a racing package on your insurance, takes care of rig, sails, and shrouds.
Title: Re: GNAV
Post by: Jay Harrell on November 06, 2010, 05:29:07 PM
++1 on the insurance.  The day after we arrived home from 2008 NAs, a microburst hit our house and dropped a tree right on top of my mast, crushing it, and doing $10k of other damage on my house and property.  Insurance bought me a new mast...


Quote from: Lee Shuckerow on November 06, 2010, 03:51:11 PM
finally had our viper carbon rig payed for. It broke in February. Make sure you have a racing package on your insurance, takes care of rig, sails, and shrouds.
Title: Re: GNAV
Post by: Justin Scott on November 07, 2010, 05:05:13 PM
A very timely microburst if I remember.

If my damn keel box doesnt stop leaking I sense a micro burst coming on.
Title: Re: GNAV
Post by: Matt Sole on November 07, 2010, 07:30:09 PM
Who are you guys using for insurance??

Finally Justin is realising there may be foul play in his keel box issue.

I point the finger at Lee and Brad......
Title: Re: GNAV
Post by: Jay Harrell on November 07, 2010, 09:05:44 PM
Quote from: Matt Sole on November 07, 2010, 07:30:09 PM
Who are you guys using for insurance??

The Gowrie policy through US Sailing.  (http://www.gowrie.com/)  I owe them about 10 years more premium to break even.

And yes, it was well timed as far as the Viper goes - I got a new class mast out of the deal.  Despite the damage to the house, we were very lucky -  giant trees  (one 8 feet in diameter) fell all around both our cars, the Viper and our camper without damage, except for the big hole in the driveway.  Had the Viper or my truck been in their normal parking spaces, they would have been crushed flat.

Title: Re: GNAV
Post by: Brian Bennett on November 27, 2010, 01:34:58 PM
FYI. Tin rig owners.

I would be very weary about installing the GNAV on the metal mast. Due to the shallower spreader angle, and narrower shroud base, also further forward than the Carbon rig geometry, you will have very little forgiveness in "breeze on conditions" The GNAV loads the mast quite differently to the regular vang, with much more distortion in the lower panel (deck to spreaders).

Additionally, by the time you file away the sail track, and add the compression gooseneck, you will have no material support.

I hope this helps. I have some new tin rigs in storage at Hall, if someone gets in a pickle. They will be cheap.

Regards,  Brian Bennett
Viper 640 designer
Title: Re: GNAV
Post by: David Morse on November 28, 2010, 09:17:00 PM
Brian Bennett, a poster we always like to hear from.  Glad to see you still keep track.
Title: Re: GNAV
Post by: Duncan Adams on December 05, 2010, 05:12:15 PM
Thanks for the tips Brian. We have moved our chain plates to the new position (out and back)and installed longer (class legal) spreaders, do you still think fitting the GNAV would be a bad idea?