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Discussion Starter · #1 ·
I am planning a project to bring my halyards back to the cockpit from the mast, which means two stand-up spring blocks and two deck organizer type flat blocks.

However, the section of the deck where I'd be installing this stuff is ...actually not sure how to describe it, but there's a "cavity" between the surface of the deck and the ceiling of the cabin. So there are two sections to the fiberglass, and it's hollow in the middle. This means that I can't drill all the way through and use a bolt/nut arrangement.

Is it ok to just attach the hardware with screws+caulk? (I'm thinking deep-biting wood screws might work?) I imagine for the flat deck organizer this won't be a problem since it will only experience force lateral to the deck. For the stand-up block, though, it will experience roughly half of its force straight up when I'm raising the sails. Will the screws pull through the fiberglass? The guy at west marine seemed to think it would be ok, but ....

Opinions?
 

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One of None
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They would pull out with even a little pressure. Suggest using a backer plate and spacers from the plate to just slightly below or even with the top (deck) The bolts would pass through the spacers.
 

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there's a "cavity" between the surface of the deck and the ceiling of the cabin.
That may be a bigger problem than whether your halyards run back to the cockpit or not.
Why is there a gap there?
How thick is the 'surface of the deck'? If I understand you right, your description sounds as though there was meant to be a core of plywood or balsa between the 2 fiberglass layers. But sometimes, some parts of the cabintop are solid FRP by design. If that's the case, and the cabin ceiling is just a cosmetic shell, I like DeniseO30's suggestion.
If the gap is where a deck core should be, I'd want to find out what the story is behind that. You could address such a problem by injecting thickened epoxy into the gap. If the gap covers a large area, I'd envision having to drill a lot of holes an inch or so apart and injecting the epoxy. Then you'd need spacers between the deck and the cabin ceiling, but you'd have a solid deck.
JV
 

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You didn't say how big your ship is but for relatively small deals, how about cutting out the under panel using the backing block/plank for a template.Thickness is what ever it takes. Epoxy to underside of deck and reglass the deck head. Mount away. Even counter bore for nuts if scalp is in danger.
 

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No way a screw will work here. Cannot imagine what the guy at West Marine was thinking.

Fill the cavity with something (thickened epoxy?) through bolt it and use a good backing plate.

Hard to say but I'm guessing you are describing a hull liner? Does the overhead extend all around the boat and incorporate cabinets and such?
 

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As others have said - how big is your vessel?

I am going to get a bit longwinded here - sorry if you already know this!

Boat decks can be built in many ways. The most common is a 'sandwich' - fiberglass layer, core (generally balsa), them more fiberglass. This makes a lightweight yet rigid surface. Some boats have structural areas of the core in marine ply, which won't crush as easily as balsa; other variants include thick fiberglass, and in some boats a balsa core and thicker fiberglass/no core in structural areas.

So that is the deck. Now inside the boat, you want to make it look pretty - so the deck interior is generally covered by something - paint, wood, vinyl panels with zippers, sometimes a more attractive later of fiberglass. This is called a "liner".

A gap (void) between the liner and deck is common. You could fill it with epoxy, but that could make access more difficult in the future.

A gap between the deck "skin" layers where balsa/plywood should be us bad. You can generally tell it is bad because the deck, instead of being rigid, flexes.

So you need to understand what the gap is, and the implications, before just filling it.

I would personally never use a screw in the situation you are describing. I would always use a nut an bolt, and always with either a backing plate or large washers. I would probably use a cap nut (a nut with a dome top) as they are more attractive.

I hope this helps. Generally the more information you can provide about your boat - make/model, length, age - the better we can provide advice. Good luck!
 

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Discussion Starter · #7 ·
Lots of good info a far. Let me provide some more info on some questions that have been asked.

The boat is a 1969 ericson 23. The section of the deck in question surrounds the mast, about 2' on either side port and starboard, and about 1' both fore and aft. The 'cavity' is there by design. It's not where the deck fiberglass has separated from the core or anything like that--there's just a gap between the deck material and the cabin liner. To be honest I'm just assuming it's hollow--might be filled or it might contain wood or something else. Sounds hollow when tapping.

Does that help?

I suppose it would be possible to drill all the way through the deck, cavity, and cabin liner with 5-6" bolts with a plate in the cabin.
 

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1. It must be bolted through with a backplate on the inside.

2. The backplate needs to be supported from below, otherwise the blocks will lift/deform the deck.
 

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You cannot put the backing plate on the liner. It won't support the pressures. Cut the liner with a hole saw slightly larger than needed for the backing plate. Drill the holes for your installation and install with bolts and nuts through a strong backing plate. The backing plate should be against the inside of the cabin top. Make a cover for the liner out of teak or luan plywood or use a removable deck plate to cover the hole in the liner. Don't forget to use caulk!

Tod
 

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It sounds like you are describing a head liner that is purely cosmetic to cover up the bottom of the fiberglass deck. Best would be to remove it, install the hardware, and then reinstall it. If that's not possible or very difficult, than you can cut a small section out of the headliner, and then fashion a cover to put over the hole.

The deck is most likely a sandwich with fiberglass on the top and bottom and balsa or plywood in the center. The hollow sound could be a problem, indicating delamination due to water intrusion. Is so, that will mean some additional work is in your future.
 

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Something like this hole saw will make a nice clean access to the underside of the deck, as gladrags described. The picture does not show the center piece of the tool (separate purchase), which includes a standard drill bit. You can drill a small pilot hole exactly where you want the center of the large hole, then the hole saw guides on that pilot hole to cut a clean circle around it.
 

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Lots of good info a far. Let me provide some more info on some questions that have been asked.

The boat is a 1969 ericson 23. The section of the deck in question surrounds the mast, about 2' on either side port and starboard, and about 1' both fore and aft. The 'cavity' is there by design. It's not where the deck fiberglass has separated from the core or anything like that--there's just a gap between the deck material and the cabin liner. To be honest I'm just assuming it's hollow--might be filled or it might contain wood or something else. Sounds hollow when tapping.

Does that help?

I suppose it would be possible to drill all the way through the deck, cavity, and cabin liner with 5-6" bolts with a plate in the cabin.
Good suggestions so far. You do want to use a backing plate or at least a "fender washer" for each screw on the inside of the cored layup. And that's above the liner. I have done work just like that on my prior 26 foot boat.
There are good discussions of this sort of work (very similar on all the smaller Ericson's in the 70's) over at the owners' site, EricsonYachts.org: The Starting Point on Ericson Yachts!.
Ask questions there and you'll get good info from a lot of other owners.

Loren
 

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Even if it was cored, like the hull, you would still have to dig out an appropriate amount of coring and fill the space with something hard like epoxy filler or a block of wood. All too often I see folks installing thru hulls on cored hulls without doing this (below the waterline), and end up crushing the core, dimpling the hull and creating a permanent and damaging leak (as water soaks into the core).
Simply put, no, screws will not do the job properly, especially if it's something that has a lot of load like a halyard. Not only should you fill the void, but using a backing block would be recommended, as well.
 

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Through bolting is the only way to properly do this. As others have said a screw will rip right of of the deck. What I would do is to purchase some fiberglass tubing or rod (McMaster sells this stuff) that is large enough to be drilled out for the correct size bolt and still leave about 1/8" wall to the OD. Drill out the holes in the deck to allow the rod to be a snug fit and then fiberglass it in place to the deck. Then use a backing plate inside the cabin. This way the tube carries all the compression loads and the backing plate distributes the load.
 
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