Replacing glassed-in chainplates

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Replacing glassed-in chainplates

Postby bigd14 » Sat Jan 16, 2010 1:43 am

Hi everyone- I am about to undertake one of the most important repairs to this old boat and I am hoping to tap into the collective wisdom of the board. The issue is the glassed-in chainplates for the shrouds. The boat is 38 years old and has been severely neglected. As you can see from my earlier posts in the project section, the chainplates have leaked for years, necessitating the replacement of both side deck cores. So the chainplates are highly suspect in my opinion and should definitely be replaced. There are several reports of chainplates failing in other Ericson 27s with the same system in place. Knowing this and knowing how poorly the boat was maintained by the PO('s), I'll never be comfortable with the existing chainplates. So they have to go.

The current configuration is a stainless steel strap that runs along the inside of the hull about 7 inches below the sidedeck. It is heavily glassed in. Then there are three vertical straps that are welded to the longitudinal strap, bent into an S shape, and exit through the side deck to form the chainplates. The whole assembly forms the shape of an E lying on its back.

Chainplates on port side
Image

View underneath side deck
Image

View of chainplate with fiberglass removed
Image

What I am planning on doing is moving the chainplates to the outside of the boat. I will use the existing longitudinal bar as a backing plate, since most of the failures seem to happen on the upright section. I plan to grind off the hull-deck joint flange on the outside of the boat in the vicinity of the chainplates so they will lie flush against the hull (I'm actually debating grinding the entire flange off and glassing over it). The chainplates will have at least one bolt that goes through the backing plate bar, the others will go through the existing hull which is very thick in this section. I am thinking three bolts in all. The good news is that this has been done before by others with these same boats. But I still want to think about all the angles here.

E27 with external chainplates retrofitted
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E29 with external chainplates retrofitted
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Issues-
Some of the issues I have identified are as follows:

1. Jib sheeting- The current set up is a jib track on the toerail aft of the chainplates. I know I will lose a couple inches of sheeting ability, but will it really make that much difference?

Photo of distance between edge of boat and chainplates (about 2 inches)
Image

2. Strength of backing material and required bolt size- it'll be easy to figure out bolt shear strength and size it exceed wire breaking strength, and the longitudinal strap should support the tension of the shrouds as it does now, but how much support will the hull material where the other bolts will be provide, and how much does it need to provide (see 3.)?
3. Do I need to add additional backing material, like a long pad that runs above or below the strap to serve as backing for the other bolts?
4. Do I need to reinforce the hull-deck joint connection to deal with the compressive forces that will now be higher up on it (its already glassed on the inside from the factory)?
5. Will the additional width change the angle of the shrouds enough to cause problems (I figure I can adjust the spreader angle a bit to compensate)?
6. The chainplates will need to be higher than the toerail, which will cause my new rigging to be shorter. I may need to use sta-lok or some other DIY fitting on the bottom of the rigging to get this just right (and spend a lot of time with the local yard's crane to install them!).
7. The last issue is the nagging feeling that there is something that I am missing... and that's why I'm posting this here!

So... have at it! As usual any and all advice, commentary, musings, etc. are welcome. This is the best forum anywhere, and has been absolutely invaluable to me during this rebuild.

Thanks!

Doug
Doug
1972 Ericson 27
bigd14
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Re: Replacing glassed-in chainplates

Postby stone » Sat Jan 16, 2010 12:37 pm

1. Jib sheeting- The current set up is a jib track on the toerail aft of the chainplates. I know I will lose a couple inches of sheeting ability, but will it really make that much difference?

Yes. The fact that it may only change pointing ability a little would be a reason for me not to want to do this.
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Re: Replacing glassed-in chainplates

Postby Triton106 » Sun Jan 17, 2010 1:27 am

Doug,

Great job you are doing on your Ericson restoration! Please post more pictures of the progress.

As for the chain plate I will be following this thread closely as I am about to get to that part soon.

I am not a big fan of the external chain plate for two reasons. One is esthetically they look great on Westsail or any other heavy displacement cruisers but not on Ericsons or other similar design racer/cruiser. The other reason is that they tend to mess up sheeting angels as you noticed.

I don't know if you thought of another option which I have contemplated. You will still mount the chain plates inboard but instead of them being welded to the horizontal plate imbedded in the hull you will epoxy a wood backing plate between the hull and the chain plate. The thickness of the plate should be equal to the distance between the hull and where you want the chain plate to exit the deck. You wil then bolt the chain plate through the backing plate and the hull which should form as a strong bond as the external chain plate design and yet you don't have to deal with the sheeting angel issue or in my own case the esthetic issue.

The back stay chain plate on my Pearson Triton (west coast version) is set up that way. I am not sure why I have not seen more chain plates done that way. I am sure there are reasons why more people are not doing that and I will be interested in learning why.
Ray D. Chang
Triton 106 in Berkeley, CA
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Re: Replacing glassed-in chainplates

Postby newt » Sun Jan 17, 2010 2:40 am

Doug,
I just replaced my standing rigging and chainplates on my Valiant. They are a b*&tch to get out. I used a slaphammer and made sure they were as loose as possible. You have to modify the slaphammer with a old bolt, but it can be done.
As for the shrouds- I did put the adjustable DIY fittings on the bottom. It makes a lot of sense and gives me peace of mind for out in the boonies adjustment. I also put my steering cables in the same way, but those are a bit harder to do.
May the wind on your back not be your own.
newt
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Re: Replacing glassed-in chainplates

Postby bigd14 » Mon Jan 18, 2010 12:41 pm

Thanks for the replies. Ray I think your solution sounds like a good one, and one I hadn't considered. I would probably use G10 or some other FRP instead of wood to reduce the possibility of rot if water penetrates. It would be some significant glass work, but easy enough. Do you have a photo of your backstay assembly?

I wonder if I would need some kind of backing plate on the hull side for the bolt heads?

Heading down to the yard today to check the structure. 40+ winds last night...


Doug
Doug
1972 Ericson 27
bigd14
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Re: Replacing glassed-in chainplates

Postby bigd14 » Mon Jan 25, 2010 1:26 am

I gave a lot of thought to Ray's suggestion about building a backing pad in the interior of the hull and I think that is what I will now do. I removed a few inches of fiberglass on each side of each chainplate, both to inspect the condition of the welds and in anticipation of drilling holes through them. All the welds seemed fine, but there was a bunch of rust that seemed to be running down from the deck area. So if there is going to be a problem, I suspect it will be where the chainplate goes through the deck. But of course, I won't be able to tell until I cut them off.

Image

So here is the current plan.

1. Cut off upright portion of chainplates.
2. Drill 4 holes through hull at each chainplate. 2 of the holes will be through the existing metal strap (see diagram)
3. Build a pad at each chainplate area (or one big pad all the way across all 3) approximately 1 inch thick. Some combination of frp like G10 and biaxial cloth. Pad will extend up to the deck and down as far as the bottom of the liner pan, and in far enough to allow the chainplate to mount flush against it and extend straight up through the deck.
4. Using holes already drilled on hull side, drill remainder of holes through pad.
5. Install SS backing plate on exterior of hull.
6. Install chainplate using 4 SS shoulder bolts.

Here is my conceptual plan for the bolt hole placement:
Image


Of course this brings up a bunch of questions and issues I'll need to consider:

Hull backing plate- necessary or not, and if so, what kind and size of material? I don't think it would look very good, but if it's necessary, I'm more concerned about structural soundness than looks.

Pad build up. Should I add a layer of frp, or just use layer upon layer of biax?

Individual pads, or one large one the entire length of the strap? I also thought about glassing in a strip of frp above the strap for its entire length to add strength. The upper bolt holes would go through this strip.

Liner issues. On the starboard side, the liner sits higher up than on the port. There is a void behind it which I will either have to fill with thickened epoxy somehow, or I will have to cut portions of it down. I don't want to leave a compressible space behind there. See photo below.

Sizing of through bolts and chainplates. I'll have to figure out existing rigging loads. The existing chainplate is 1/4 inch ss that is 1.5 inches wide. Right now I am thinking of upsizing everything a bit. 3/8 chainplates, 1/2" bolts perhaps. I like to overbuild stuff and I want the chainplates to be the strongest part of the rigging.

Here is a photo showing the liner issue. I could stuff the wire down between the hull and the inside liner that extends down to the starboard berth. Then there is the overhead liner glassed over this area. The liner is part of the structure of the boat so I don't want to try to take large sections of it out if possible. you can also see a void on each side of the chainplate area I cut out in the bolt hole photo above.
Image
Doug
1972 Ericson 27
bigd14
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Re: Replacing glassed-in chainplates

Postby Triton106 » Tue Jan 26, 2010 1:30 am

Doug,

Here are some of my thoughts on the questions you are contemplating. Apologize in advance that due to my busy schedule now I don't have the time to dig deep into the supporting material.

Of course this brings up a bunch of questions and issues I'll need to consider:

Hull backing plate- necessary or not, and if so, what kind and size of material? I don't think it would look very good, but if it's necessary, I'm more concerned about structural soundness than looks.


I don't think hull backing plate is necessary. When you epoxy the G10 backing plate to your hull and glass in over you will create a tremendously strong solid piece of fiberglass that is over inch think. Adding a backing plate of course will be stronger but hardly required.

Pad build up. Should I add a layer of frp, or just use layer upon layer of biax?


I don't completely understand your question. If you are using G10 as backing plate I am not sure if you need to add more fiberglass to it.

Individual pads, or one large one the entire length of the strap? I also thought about glassing in a strip of frp above the strap for its entire length to add strength. The upper bolt holes would go through this strip.


I think single pad is strong enough but one large pad is stronger. I envision that the pad will go all the way to the undereside of the deck.
Ray D. Chang
Triton 106 in Berkeley, CA
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