Hi, I have a problem with the shroud attachments on my boat and I'm looking for some suggestions/opinions.
I have a Sonata 6, but it doesn't have the original rig as far as I can tell. The original looks like a mast head rig with shrouds terminating at chainplates attached to the cabin. At some point in the past this has been changed to a slightly bigger fractional rig with upper and lower shrouds that terminate at saddles through bolted on the deck (one for each shroud). The deck is plywood cored fibreglass. There is a stainless backing plate of about 75x120 on either side of the deck.
The problem is that the bigger rig has additional loads and attaches at a point that was not originally intended, using hardware that I feel is not adequate. A while ago I noticed some cracks on the topside of the deck around the plate, probably caused by the extra load from the cap shrouds. To take some of the extra load I fitted an additional saddle on the underside of the deck on the same bolts as the topside saddle. I then attached a turnbuckle and ran this down to a steel bar running between two buttress pieces on the hull. This allowed me to tighten down the turnbuckle and spread some load to the hull.
I now want to upgrade this arrangement and replace the saddles with some proper chainplates. These will need to pass through the deck if they are to stay in line with the end of the spreaders. If I do this, what do I attach them to? They will be about 80mm from the hull and there is no bulkhead available. Would I be able to put a spacer, like a block of wood, between the chainplates and the hull?
I'm sure you could do something like that. Sand the hull back the the fibreglass for about 200mm both sides and up to the deck or cabin top. then make an epoxy fillet all around then about 4 layers of 600gm double bias starting with a 100 mm strip and going 25mm wider each layer. It will be as strong as can be.
I nearly bought one of these in the early seventies. Went to the factory up in Brookvale. I think I would look at up grading the SS strap arrangement down the inside of the cabin sides and maybe enlarging the pad on the inside of the hull as Andy59 suggests.
Just a thought, does the boat have overlapping headsails? If not why not move the chainplates outboard closer to the hull?
The advantage of the original design is that it provides sideways stability when raising the mast, plus makes it easier to walk along the side decks. I am a great believer in staying with the original design, unless there is a fundemental flaw in it.
Obviously the side deck was not designed to take the load. Why not go back to the original mounting, and maybe beef that up a bit?
Hi,
I'm not sure I can go back to the original mounting point on the cabin top. Its not just the mounting point that has been changed, but the whole rig. It's now a fractional rig with swept back spreaders. Not sure why the rig was changed, and I agree that its probably best not to try and second guess the designer. But I bought the boat second hand and I've got what I've got.
To move the shroud attachments in to the cabin or out towards the hull I think I would need to change the length of the spreaders to keep the mounting points in line with the end of the end of them. Can anyone confirm if that's correct? To attach to the cabin top would probably mean coming in 10-15cm - is that a problem?
Here's the only picture I have at the moment. It shows the inside of the cabin looking aft. The existing attachment is between those two left most triangular knees. You can just see the backing plate and bolt heads poking out.
I own a Sonata 6.
Looking at the internal pictures of your Sonata, it appears you have have a Sonata 6.3, which has a fractional rig.
Check out the Sonata website.
That it is a 6.3 is good to know and should be reassuring.
Can you post photos of the cracking of the gel coat on the deck?
The cracking of the gel coat around and on the under-deck gussets could just be cosmetic. Dig a little bit off and see if the cracks extend into the f/g itself. Might be the same story on the deck. All stainless steel chain plates which pass through a deck should be checked for crevice corrosion. Other than that, maybe what you have is OK.
I'm not sure how much pressure that chain plate would be under. It would not be too hard to put another knee in and bolt a nice stainless chainplate to that. You could scrape/sand off all that flaking paint in the process and have a good look at those existing knees. Failing that a piece of 20mm marine ply epoxied to the 2 existing knees on the underside of the deck would be easy to do and provide a fair amount of strength to the attachment point.
Thanks Andy,
putting a reinforcing piece to the underside of the deck and glassing it to the knees is probably the easiest thing to do, and is within my skill set. I'm OK with timber and glass, but was getting intimidated by the metal work that would be involved making new chainplates. This solution will allow me to keep the existing saddle arrangement, with some beefed up hardware.
Hi SonataSailor. It would be nice to find out I had a 6.3 instead of a 6 - who wouldn't want to gain a few inches? But, I'm pretty sure it is a 6. I've trawled the internet for some time now comparing my boat against other Sonatas. The things that have convinced me its a 6 are: Internal layout (sink is on the starboard side on my boat), plumb stern (the 6.3 has more slope and a lip on the transom), Fixed keel - mine has a solid keel and I think the 6 was the only Sonatas ever made with fixed keels.
The Sonatas were shipped to WA unfinished and it was up to the local dealer to add a keel etc. I wonder if the WA dealer put a bigger keel and a 6.3 rig on this boat. There's no evidence that the shrouds ever terminated on the cabin top, so maybe this is the original rig.
Here's a pic of the boat in and out of the water.
My bad on not thinking of the fixed keel version of the 6..
I think they are rarer than a 6.3.
That's a nice looking boat. With the chain plates off the cabin sides and on the deck set wider apart there is less strain. You might be a little over cautious!
Yep - the big lump of steel on the bottom makes her a nice stiff boat and able to cope with the upsized rig. 
The breaking strain of the 4mm shrouds is 1340kg. Preload for the fractional rig is 25% of that, so 335kg static load. I'm not sure what the dynamic load would be if I ever get brave enough to hoist the kite in 25 knots, but better to be safe than sorry I say.
