Chainplates and distortion of the deck

[monsters inc]

I was placing my jib tracks on the boat this week. Previously I was tensioning the mast uppers to see what kind of pretend I can get out of the aluminium Viper 640 mast. I had a lot on, got my measurements and left it for a week or two. When I put the harken jib track in place, there was a definite hump at the chain plate gusset. It is laminated to 1 " width as the plans suggest. When I dropped tension on the shrouds every thing went back to fair again. The new doublers for the jib tracks are in and mounted in place but I will be adding a few layers of glass under deck between Stn. 89 and Stn. 124. Have any of the sailing 550's noted any distortion in this area? I remember a post showing a torn out chainplate but went back on this site, and couldn't find it. It may have been on the sailing anarchy.. At any rate , glad I found this before anything was damaged, but looking forward to laying on my back putting cloth overhead! Not! New builds may want think about reinforcing this before closing up the deck. Just thought it may be useful to know. Here is my highly modified spinnaker, cut down from an old Dash 34, if you ever need advice on picking stitches out of sails, I now have a lot of experience! Thanks, Mike

[Warren Nethercote]

If stiffness is the issue then adding carbon fiber would be more effective than glass, or even a plywood doubler carefully-fitted. I adding glass or carbon, use a pattern and then lay out and wet out the fabric on ply-ply and then transfer that into place, Getting it to stay in place overhead will be fun.

It might be more effective the stiffen the attachment between the shroud gusset and the side shell. If would be easier to apply glass or carbon reinforcing hat attachment and stiffening that part of the hull.

Did you by any chance put a Loos gauge on your rigging? Sounds like a lot of tension.

[monsters inc]

No loos gauge, but it was tight, little or no deflection of the outer stay was possible. Your idea of a carefully fitted doubler was my first thought as well. I will post some pictures once I come up with a better plan. I am mulling over using Douglas fir stringers to match the gunwales , and tieing them to the chain plates as well. That should be a tough compound set of angles to cut. Once in place , carbon tape over the stiffeners. Oh the joys of boat building.

[Warren Nethercote]

It is easy before the decks go on ....

Here is what I did. I used a variant of Chad's 'cant frame', attaching the chain-plate doublers to that and then laminating carbon fiber to tie the chain plate doublers into the side shell forward and into frame 110. Of course, I haven't seen any rigging loads yet! As I recall, the Australian boat that lost its rig look like the builder relied solely on glue to keep chain-plate doublers inside the boat.

And if you've ever wound up the rigging on most small GRP sailboats you will see the boat get narrower. But you are right to worry if the distortion is limited to the deck!

[Thomas]

Here is what I did , the carbon fiber does the trick , the decks are also carbon cloth, and the 1" chain plate is hooked under gunnel.

[monsters inc]

image.jpeg

I ended up putting a 1/4 " doubler under the deck, tieing the 89 rib to the chainplate ending just before the 124 bulkhead. Glass went on reasonably well for an inverted job.
My new mainsail arrived from Leitch and McBride sails in Sidney, BC. Great people to deal with!

[masc]

hi!

some weeks ago after several days of sailing (and a fullstop because of a rock) i noticed a small crack on the tip of the chainplate-support. i have no other explanation that there could have been some deformings of the hull in this area. i'm gonna strengthen the hull between F89 and F110 with another layer of plywood and glass hoping that solves this problem.

btw, it would be a lot easier before finishing the boat.

[Warren Nethercote]

The corners of brackets are typically problem areas and can be crack initiation sites. in part it may be because the bracket end is a hard spot in an area of relatively more flexible hull shell which will tend to peel the bracket corner away from the shell when the shell deflects. In a properly-welded steel structure it might lead to a shell crack if the shell is thinner than the bracket.

In this case it is a bit intriguing because of the proximity of the side shell stiffener (stringer). If I were adding plywood and glass I would try to tie the lower part of the bracket to the longitudinal stringer to stiffen the whole area. Hard to say whether the cracking is stiffness or strength related. Tying to the stringer should address both.

[monsters inc]

Photo of the sail today

[Tim Ford]

Excellent! What was the verdict? Fun? Any issues? Looks great!

[monsters inc]

Excellent! What was the verdict? Fun? Any issues? Looks great!

Twitchy, quick to accelerate, sensitive to main trim. Fun. Yes