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I have been rigging my boom this week. I will be running a rear bridle, and a centre swivel and jammer. Next up the vang. Or gnav. I have vang hardware , but could easily build the track and pole for a gnav. The attraction of the gnav is the extra space under the forward boom. Pitfalls could be mainsail shape on one of the tacks. Vang advantage, simplicity, less pressure on the gooseneck. Disadvantage , less angle to mast base due to the compression post,deck stepped mast. Any comments appreciated.
Does the vang on the current boat fleet handle the loads adequately in a blow, if so, how much advantage are you using?
Finally, how high above the deck have the booms been mounted? Thanks M

Hi Marko, I do not have any experience with the Gnav on an i550, but before I started building mine I spent time trying to figure out whether or not to buy a Viper 640 or start building. (I started building) The guy I knew with the Viper had an early boat that came w/o a Gnav (had a traditional vang arrangement) and then he retro-fitted a Gnav. He loved it. He said it was by far a better arrangement (even though the Viper really doesn't have much of a "cabin") it freed up the cockpit for tacks and jibes with no discernible loss in performance. I got impatient and just finished my boat with a vang, but if I had more time, I'd definitely go with the Gnav. An additional benefit is you wont need a boomkicker, which is my next upgrade -- unless I say screw it and decide to finally run the Gnav.

Well, I repurposed some old harken track and a car. Used a whisker pole section 4 feet long and a 4 to one vang block. Drilled and tapped for mounting screws . That part was easy. Fitting the bottom of the pole to the car with a pin took some carving of high density plastic. I am thinking that the goose neck for the top of the gnav may have to incorporate a tab to mount some shrouds to, for preventing the mast moving forward. Although my viper mast still has its liner in place so it may be over thinking... If someone could direct some tips on uploading photos I would be glad to share them but most of my picture files are too large to add them here. Cheers , Mike

Mike if you want to send the pix to me at timford AT nbayracing DOT com

I can easily downsize them and post them under your name. (hint: I'd love to see the pix)

Here are some of the photos from Mike's build (nice job!) I'll put them up and Mike can caption them

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a few more from Mike:

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Top photo, the boom . I salvaged a star boat that the owner wanted out of their yard. The boom was cut down to fit a viper 640 main , as I have an aluminium viper mast. I elected to go with a double bridle for the mainsheet, with the sheet ending up at a block swivel at station 169.5.
Second photo: the boom vang, harken track and car. Drilled and tapped 10-24 screws into the top slot of the boom to mount the track. This was positioned by mounting the gooseneck on my shop support and using a 48 inch straight edge to see how much the car needed to move if the boom lifted ( lots of twist off the top ) or pulled down tight ( flattening ) . The gnav pole is a section of aluminum whisker pole, with hi density plastic in the end to match the loop on the car. I will eventually make up some soft shackles to attach the gang fall to the mast and car. I don't think the zip tie will cut it! Also the boom and vang will receive a coat of paint before too long. The top gooseneck will be a composite wrap around the mast, and two sets of stainless ears. More on that soon .
Photos 3 and 4: Brightside paint, 3 coats, wet sanded with 320 grit between coats. Rolled and tipped , lightly thinned , but the final coat was done on a cooler day, about 60 Fahrenheit, which was the optimum temp.
Photo 4 the rudder : laminated fir core, layers of carbon on the top then skinned with carbon down the foil, and a layer of glass for abrasion protection, Brightside fire red, the hard ware was another salvage , this time a set of hardware from a j24 that was being scrapped. Selden rudder gudgeons for 50 dollars, as opposed to 600 new price. I also got selden chain plates at the same time....the tiller is one I had from another project.
Photo 5 the mast step, sits on yellow cedar compression post. I will probably add a plate to fix turning blocks to and make stepping the mast a little easier
Photo 6 engine mount. More high density plastic, but it's light and doesn't corrode. 2.5 horse Suzuki . Rudder hingeing in the foreground
Photo 7 my favorite. The keel . I started with a piece of old growth red cedar. Nice tight grain. Light, and no checks. Then I started block planning. Templates cut into sheet stainless to check shape. More planning. Lots more work here than expected. Then came block sanding. Many months of say I got yeah I should finish that soon... Finally I sealed it in epoxy and put 2 stainless ready rods in the centre of the foil to mount the bulb. That was a tough drilling job, 18 inches straight in the centre., then slotted two spots for nuts , then filled everything with 404 and epoxy and dropped it into the pre drilled bulb to set up. Then came two coats of carbon cloth, blocked fair between layers and a layer of glass. Barrier additive and epoxy was used to block everything fair, no filler. Painted then joined to the bulb with 404 and nuts. More fairing, sanding painting wet sanding painting sanding and painting. Final coat on a cool day again ....
Thanks to Mr Ford for posting the photos...more soon I hope. Mike Evans. Hull 239
Photo 7

I have updated my gnav pole. Aluminum whisker pole is out . Carbon fiber hockey stick shaft is in. More soon.

Here is the Carbon fiber GNAV strut. Lighter than aluminum, less windage.

Looks nice. I think that I'm going to take the same approach, however I'll probably leave the "Easton" graphics on. The great thing is that if one breaks, I have about 15 replacements in the garage.

Phil

On the trailer , another step closer to completion!