Chainplates and bolts through the Hull

[Island Time O25]

Since my rigging is probably original and before undertaking any serious offshore travel I've been thinking for a while to put the chain plates outside while updating the rigging. Asked a friend who is a naval architect and a boat builder and he recommended this as well. Says since I am not racing the loss of performance would be more than offset by the benefits of no leaks through the deck, less obstacles on my way to the bow as well as being able to see the plates. Been procrastinating with this project even though the logistics are fairly easy as the access to the plates is very good and the job looks very straightforward.

Could never understand why the designers put the chain plates in the middle of the deck walk through. This IMO is the worst place for them. Either do the racing version and stick them to the doghouse or do the cruising one to the outside topsides. This middle of the road approach is neither here nor there and makes for frustrating trips to the bow on any under 40' boat.

[Island Time O25]

Originally Posted by Stumble

No, but age does equate to work hardening. At 30 years they are probably close to their cycle fatigue lifespan even if there is no corrosion.

On another, brand specific forum, a member related how he scrounged a sheet of titanium of the right thickness for the plates and had it cut up and drilled at a tool and die shop. According to him it came out only slightly more expensive than quality SS plates.

[knockabout]

a quick snapshot of through bolted chainplates /our rig is a lot lower tension than modern boats / they bolt through huon pine / two layers of epoxy sheathing outside, flow coat inside / gave up using rubberised type sealant over 10 years ago and use thickened marine epoxy to seal the bolts / these were replaced 2013 and previously 1998 but had to be resealed often to stop small leaks, after using epoxy to seal the bolts and the chainplates to the hull there has been no movement and no leaks / the bolts and chainplates are 316 stainless, epoxy used is 180 marine with q-cell powder mixed to icing consistency. the bolts punched out o.k with a drift last time they were replaced

the black pipe in the photo is the port side kiss counterpoise earth for the hf

[Dave22q]

My Morgan 33 O/I has the same set up. I see it as stronger and easier to inspect then alternative locations. That more than offsets the very infrequent wetting of the plates as Morgans are not designed to sail,on the edge.

[Cheechako]

Originally Posted by Stumble

No, but age does equate to work hardening. At 30 years they are probably close to their cycle fatigue lifespan even if there is no corrosion.

Nah, not even remotely close. Most chainplates don't even cycle much.

[clockwork orange]

Originally Posted by roverhi

I have the opposite take as Uncivilized. The big problem with inboard chain plates is the through deck area. Sealing this area is an area that's very prone to leaking. That can result in crevice corrosion in the stainless and core rot in the deck. The force on the bolts is in shear which is the strongest. Sealing the bolts is relatively secure as you don't have to contend with movement of the deck. Ideally it would be good to have fender washers under the bolt heads or the chain plates on the outside of the hull. Wouldn't bother me the way it was built, though.

Second 'old frog' recommendation to check all the chainplates and rigging attachment fittings to check for crevice corrosion. Taiwan stainless doesn't have a great reputation for quality and the areas where the SS passes through the deck and hull are the weak point.

While I mostly agree that there are less issues with the chainplates through the hull sides I should point out that the bolts are in single shear which is the weakest, not the strongest as suggested use of a bolt being only 60% of the tensile strength. This is of course irrelevant as long as there are enough bolts of appropriate size. I am working on a customers Hans Christian at the moment abd we have the chainplates out, in this case they go through the deck but bolt to the hull and the heads of the bronze carriage bolts were sucking their way into the fiberglass, a poor design imho. it would be better with the chainplates on the outside.

Steve.