new chain-plate attachment

[phorvati]

Hi all, a little while back i posted few photos on the rusty chain plate in the rigging section. Well as I was digging out the tee-bar i found more than I bargained for. Naturally, I have a lot of questions but first things first.

1. Can i fabricate a bulkhead out of plywood and glass it using 1708 so i can through-bolt the new chain plate as shown in the hand sketch? Hull is tapered in that area.
2. Section to the right of tee-bar has water seeping out of the core(Airex) and i am trying to figure out how to address it. At this point I took some moisture readings, but those were using a cheap home depot moisture meter. However given that i have a known wet area(where the trickle was), and known dry area(solid glass to the left of the tee-bar), the numbers might have some meaning, and they are disturbing. Surveyor sounded the hull with a mallet during quick launch back in September. I was with him and he said the hull was solid. It did sound uniform and pretty solid to both of us. Also No blisters. Given that it was a quick launch moisture readings could not be taken. Now that the boat has been out of the water for 2 months, I think I should get the readings on the hull. But if it comes elevated what do i do? The boat was a FL boat and I am now in RI. Should i be worried about deep freeze and water in the core expanding causing damage to the structure?

[Suijin]

I'm pretty certain that you're solid glass below the waterline, so please tell me the boat is barrier coated. Using a moisture meter and interpreting the results is a fairly black art given the degree to which they can be influenced by various materials/thickness/etc.

The moisture you see may have in fact wicked in via the chain plate itself. I'm having trouble really telling what is going on from the photos in terms of structure.

And yes, if any cored area has moisture in it and it freezes, it could well cause cracks depending on how much moisture and how cold it gets.

I'm not going to comment on what you can do to repair the attachment. That's over my pay grade. Seems like it was goofy engineering to begin with.

[phorvati]

Goofy indeed. The tee bar was glassed in, and looks like about 12" by 12" area around it does not have core. Airx was removed and this bar glassed in. So it's unlikely water got in from the chainplate. This boat has ports and teak rubrail which is screwed into the hull. One port is directly above the problem area. Both could introduce leaks. I don't know if it's barrier coated. There is a scratch near waterline that is showing grey coat which looks like it might be interlux 2000.

It's going to get cold and I guess I need to get an idea how much moisture is in the rest of the hull before damage occurs.

Sent from my SCH-I545 using Cruisers Sailing Forum mobile app

[Orion Jim]

I wonder how many years and thousands of miles that "goofy" chainplate installation served its purpose?

[phorvati]

most of these models do not have that attachment. Based on one of the practical sailor articles, chain plate usually attaches at the knee. on this boat, it seems, this was added post production. same article suggests that on early hulls, they tabbed the knee onto inner gel coat as opposed o heavy laminates. So the entire thing is compromised. Perhaps that's why they added these.

[rognvald]

" Should i be worried about deep freeze and water in the core expanding causing damage to the structure?"



Yes.

[phorvati]

I made some progress in terms of water in the hull. It seems just in time before the winter. Using home depot moisture meter(yes i know its useless), set on masonry setting, I was able to find areas that have water from inside the hull. And boy, did they have water. This boat has 7 windows in the hull on each side. Well readings below each of the ports showed 20-30% relative moisture when the meter was set to masonry setting. As i went down from below the port and towards the bilge, there was a point where moisture readings went from high 20s to low single digits. It seems that is where core ends and solid hull begins. Drilling sample, holes at the lowest point with high moisture reading got me to several spots where water was gushing out. I only drilled the inner skin and I could feel the bit penetrating the core and stooping at the outer skin. I also confirmed that below that edge hull was solid FRP. There were some readings in the 10-20% range in areas where core is, for which water did not come out. There was only 1 spot with readings > 40% and a lot of water came out. Fluid is not solvent based, its fresh water, reaffirming hypothesis that leaky windows are the culprit. There are no blisters on this boat. I saw three surveys on this hull since 2011(one of them being mine) and each one reported the hull to be in excellent shape. I just cannot believe that three surveyors would miss this. Or is this normal for 30+ year old hull?

[rognvald]

P,
It seems impossible, to me, that 3 surveyors could miss this problem and give your boat a clean bill of health. I am certain there are some excellent surveyors in the business, but my experience with them has been entirely negative. There is much collusion among the seller, broker and surveyor if there is a monetary incentive involved where everyone benefits from the sale. I have experienced this many times. It's human nature. It will always be so. If this were my boat, I would hire a fiberglass repair specialist with a good reputation to do a sound analysis of your hull if you want the true picture. Based upon his analysis, I would proceed with the necessary repairs. It will be money well spent and you will avoid much wasted time. Good luck and safe sailing.

[phorvati]

So I'm at a point where I have to make some decisions on how to terminate this. What I know is based on RM30 calculations, force of pull on the main chainplate is 27k lbs.
I know stainless steel is 80kpsi, G10 is 38kpsi. I was thinking of buying G10 and tabbing it using 38oz stitchmat, 2415 style. 2415 is what's in the hull in the repair area and I have a lot of spare. G10 would be aligned to overlap with the stainless strap. I was thinking of getting 1" thick G10 panel wide enough to go from the hull to beyond the stainless strap holes shown in the picture. About 9". Tab the entire panel to the hull with as many overlapping sections of 2415 as feasable. Length of G10 would be around 2-3 feet. I can also make it longer. Any comments would be appreciated.

[barnakiel]

I believe part of your challenge is to attach the new system to the old hull strong enough.

In our boat, the plate supports were formed during hull lay up - in a one-piece process.

Can you get an equally strong bond now, using post production methods?

???

If the bond is not strong enough, the new support will simply snap and detach from the hull structure.

?

b.

[phorvati]

Well I need to make it as good or better than it was without the stainless tee bar that rusted away. This is how it was attached before and it obviously didnt rip out. I think it was strong enough attachment but the tee bar choice was poor.

[phorvati]

This was also post production

[barnakiel]

Originally Posted by phorvati

This was also post production

Are you sure?

Normally, an element like this would be built at the hull lamination stage to achieve chemical bond.

b.

[phorvati]

Normally, but not in Taiwan in the 70s and 80s. yes few owners confirmed it and practical sailor article talks about it. only 25 of these boats were built and first several hulls had a defect where the fiberglass knee that holds the main chainplate, see earlier pics in this thread was glassed to already gelcoated interior. On those boats, knees were separating. It is unclear how many boats had the defect. My guess is one of the POs on this boat added these metal straps to support the load in case the factory knee screw-up took place on this particular hull. The knee does not show signs of separation so i may not even need the strap. It was there i dont know for what reason, so I want to give the strap an attachment that will not deteriorate.

[barnakiel]

Originally Posted by phorvati

(...) It was there i dont know for what reason, so I want to give the strap an attachment that will not deteriorate.

OK. I stand corrected. I did not know the whole story.

Cheers,
b.