Question on hull deflection at chain plates.

[Ric in Richmond]

Looked at a 1968 33' Non cored GRP boat today with slight hollows on the hull sides at point which the blocks the chain plates are attached to.

Single upper with double lower shrouds. I think rig tension from a hydraulic backstay may be a contributing factor.

Probably never notice them but for the flag blue paint. Clearly at and around the attachment points where large blocks were glass into place with stainless steel chain plates then through bolted fore and aft thru plates then glassed over again (why do they glass over stuff that any reasonable person would want to inspect occasionally?)

Easy access to inspect interior of hull and found no obvious delamination or seperation.

Stern didn't appear compromised but had much better attachment method.

Owner was aware of the deflection and said yard had inspected as well as prior survey.

Sound reasonable? Is this a deal breaker on old boats or something that happens often?

Thanks in advance..

Ric

[Rachel]

Hi Ric,

What brand/model boat was it, if you don't mind saying?

--- Rachel

[Ric in Richmond]

Hi Rachel.

It is an Allied.

I re read my post and that is hard to understand.

Picture the the shrouds attached to chainplates piercing the deck and attached to blocks of wood with bolts. Then the chainplate/block assembly glassed to the hull side.

The hull has been deflected in response to the load placed upon the block.

The dark blue paint and shiny surfaces of course magnify the effect. The deflection doesn't appear to by more than 1/4" at most. You can access the back of the hull at these points and there is no obvious delamination or cracking.

May just hire a surveyor. Other than,and a few minor things, she looks good.

[Figment]

This is commonly referred to as a "hard spot".

Is it a general area of depression in the rough neighborhood of the chainplate knee, or is it more like the precise outline of the knee is "printing through" the hull?

Is it possible that the whole deal was glassed over by some goof who was trying to spread the load and diminish the hard spot, or does that glass work look to be original to the boat?

[George ( C&C 40 )]

Hi Ric,


Just a quick note. Increasing pressure ( shortening ) on the backstay with a haydraulic backstay adjuster reduces, not increases, tension on the shrouds.

If the previous owner has a haydraulic backstay adjuster he has probably been racing the boat. If he has been racing the boat, the cap shrouds ( the ones that go all the way up, AKA uppers ) have more tension on them than any other piece of standing rigging. This is because the cap shrouds keep the masthead from falling off to leeward and allow the boat to point well as the wind increases. Very important in a race.

The hydraulic backstay adjuster allows you to tighten the forestay which reduces headstay sag. This also helps with pointing. The downside is that when you tighten down on the backstay you bring the masthead closer to the deck of the boat and therefore reduce tension on the shrouds. This is bad for pointing -- see above. The only way to fix this is to tighten up the cap shrouds so much that when you crank down on the hydraulic backstay adjuster you don't loosen the cap shrouds to the point that the masthead blows to leeward killing your pointing ability.

The upshot is that the cap shrouds carry a whole lot of tension on a race boat. A whole lot. Probably why he glassed in those reinfocements.

Sounds like a pretty good setup though.


George Jones

C&C 40 "Delphinus"
Wavelength 24 " Poco Loco"

[Ric in Richmond]

Kind of a moot point. I got beat out of it.

I think they would have been fine.

The front lowers were the most pronounced...thats why I think it was backstay.

Kinda bummed at the whole deal now.

Still looking for classic glass, 33-38 feet, "name" designer, Good shape with some projects ok. Don't want to have to gut and redo a boat.

Any leads are appreciated.