Deck-only chainplates

[mrx]

Good time-of-the-day!

I am currently considering buying a boat and have a concern I'd really like to discuss with more experienced boat people

The boat is Contest 33, 30something years old.

It appears that the chainplates on this boat are only connected to the deck. There are 3 sets of shrouds wach side (at angles forward and back and one going straight), all connected to loops in the deck. As far as see, those loops are held to some sort of a backing plate embedded in fiberglass under the deck. This is all. No connection to main bulkhead, nothing goes to the hull.

I got into a brief conversation with designers of the yacht (or, rather, people that took over - original designer passed long time ago) and they say that this is not an unusual design.

Still, I'd like a bit more guidance on this - this is one issue I am not sure I entirely understand the implications of.

So, how common is this? What are the things to consider?

Any help would be appreciated!

[Brion Toss]

Hello,
Let's just say that it is an increasingly uncommon configuration, because over the years there has been so very much trouble with it. It was one of those Brilliant Ideas that people come up with, for why bother anchoring to the hull when all these calculations here say the deck will do just fine?
Trouble is, the calculations left out variables like time, shock loads, construction quality, and other real world details. The result is that such decks frequently end up camel-backed, with associated problems of decks cracking (there goes the core), hull-deck joint problems, distorted interior joinery, throughdeck leaks, and of course difficulty getting and maintaining a tune.
Sound bad? It is, which is why many boats have been retrofitted to take the load to, of all places, the hull. This is something you could do yourself, affixing a tie-rod to each chainplate, for instance. But first, sight the deck to see if it flat now. Check for cracks, and if you find any, assume core damage until it is proven otherwise. Oh, and if all looks good, it were safer to assume the boat simply hasn't been used much than to think all is actually well.
Fair leads,
Brion Toss

[mrx]

Brion,

Thank you for the reply!

I suspected as much regarding the design. In this case according to designers "chainplates were moved inboard" as a part of "modernization" redesign (think 1971 modern). It appears that they were outside and directly connected to the hull before then - a much more conservative configuration.

The deck looks solid (surprisingly so) and straight, but the wood cross-beam (side to side thing) under the mast which seems to be there to stiffen the deck has a few cracks on the bottom surface, so there are definitely upward forces.

It did cross the Atlantic once, most likely when it was a much younger boat A testament to good fiberglass, but I wouldn't want to put all my trust in that

I thought about building some sort of a tie rod there but there does not seem to be anything useful on the hull to tie it to. Building fiberglass fittings connected to the hull without good strength calculations and in confines of a ready boat sounds like a bad idea.

I think I will pass on that boat, though it is a real nice (project ) vessel otherwise, to be sure.

Thanks again!

[Brion Toss]

Hi again,
In all fairness, I can think of an exception: Albin Vegas haven't had a failure to my knowledge, though the decks do tend to collapse downward under the mast...
Fair leads,
Brion Toss

[mrx]

Just when I was thinking it is decided and off I go to look for another boat

To be honest i really like this boat otherwise, she provides a very nice lines - classic but not outdated, and just seems like an excellent balance of many things that is so hard to find in anything reasonably priced.

The chainplate issue is where the balance hangs Now that you mentioned Albin I am back in doubt.

Do you think it would be possible to achieve a well tuned rig if custom fittings were to be made to connect at least one set of chainplates to the hull? I presume the feasibility and price of such fittings is a question for fiberglass, rather then for rigging specialists?