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Old 01-01-2018, 06:24 AM   #21
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FF.... wasnt it this NA that suggested the roofing tar between plywood sheets?

George Buehler Yacht Design Home Page

Probably not much different when they put red lead or something else smeared all over canvas and put it between deck layers and even hull cross planking if I recall correctly.

Here.......

https://www.duckworksmagazine.com/04...hler/index.htm
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Old 01-01-2018, 11:48 AM   #22
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Nice and clean. What color gel-coat or non-skid paint did you use. Looking for a similar color for my boat.
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Old 01-02-2018, 12:37 AM   #23
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I think core preference is closed cell foam then marine ply. I would avoid balsa. You really want to limit the spread of any water that gets in, and have a core that is resistant to rot as well.
Brian: could you explain why you think cc foam then marine ply...instead of 2 x 1/4" ply? And if you were doing the foredeck again, would you go cc foam + ply rather than 2 x ply layers?

thanks
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Old 01-02-2018, 12:57 AM   #24
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The coosa board and glass will hopefully be a 1 and done repair. Also used it on a couple of soft spots on the deck. Good stuff, solid fix.[/QUOTE]

JimW: I hadn't heard of Coosa board before your post, but have now google'd it. Why did you choose it over 1/4" or 1/2" scarf-cut marine ply? Was it because it is a lot lighter but still stiff/strong enough to walk over, or cost, or easier to work, or....? I'm in early days of investigating alternative approaches to a partial ( I hope) core replacement on my flybridge/boat deck.

thanks !
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Old 01-02-2018, 01:02 AM   #25
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Brian: could you explain why you think cc foam then marine ply...instead of 2 x 1/4" ply? And if you were doing the foredeck again, would you go cc foam + ply rather than 2 x ply layers?

thanks
Paul
Just my poor sentence construction! I was trying to give an order of preference of materials, not suggesting that you use a mix of materials!

I think multiple layers of ply works quite well. As FF has stated, use SS to ring nail the overlapping sheets down. He suggests using roofing tar between sheets, but I think I would do as the guys did on my foredeck: use thickened vinylester resin.
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Old 01-02-2018, 05:59 AM   #26
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If I were to go with with multiple layers of thin ply, I would much prefer using resin between the layers as opposed to roofing tar & ring nails. The reasons being 1:the resin at the edges of the plywood laminate repair will adhere to the existing laminate via more resin; roof tar? No bonding of the new wood to the existing structure on the edges.2: A boat continuously moves in different directions & movement is especially noticeable over a larger area such as a cabin roof, where there's lots of flexing & twisting. Ring nails or not, 3 separate panels of ply are going to tend to move in 3 different ways, Bonded as one panel would make it more rigid. 3: Roof tar is funky stuff to clean up! Yuck! Roof tar on a fiberglass yacht? Really? Why the hell NOT use resin?!!?
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Old 01-02-2018, 06:41 AM   #27
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Why the hell NOT use resin?!!? __________________




Polly Resin is not a glue and is brittle when thin after curing so more liable to crack than tar which will remain soft for decades if no air gets into the laminate.

Epoxy resin would have to be thickened to bond to layers that are not vacuumed together .

When finished a cabin top of ply is easier to bolt to the vessel .

Cored cabin tops are lighter , insulated and pass less sound , but more difficult to mount to the boat , and much harder to bolt items to as compression inserts have to be built in.

We built a replacement roof/deck for a Californian that was about 12x10, at 3 lbs per sq ft (to stand crowd traffic) it took a bunch of folks to get it up in place.

Laminating thin ply makes replacement a 1 person task, although a cored roof is simplest if thee is no structure left.
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Old 01-02-2018, 07:35 AM   #28
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FF please don't construe my posts as trying to argue your method of roof tar as being an incorrect method. This isn't an arm wrestling contest! The whole reason for this forums existence is to share knowledge & experience. I've shared mine with the op & he/she can do what they want with it. They can use cardboard & peanut butter to recore the deck if that's what they choose because it's their boat. My opinion and yours is just another tool for them to use in the decision making.
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Old 01-02-2018, 08:25 AM   #29
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"3: Roof tar is funky stuff to clean up! Yuck! Roof tar on a fiberglass yacht? Really? Why the hell NOT use resin?!!?"

hmmmmmm
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Old 01-02-2018, 03:38 PM   #30
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Jim W how did you form the Coosa board to the arch of the roof? I didn't think Coosa board flexed any (I think that is what the transom of my Carolina skiff is made of).I was thinking it would be perfect for decks . but I was wondering about anything with an arch.
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Old 01-02-2018, 05:34 PM   #31
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I think Coosa board id kerf cut to desired radius. FG on top and bottom keep it there.
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Old 01-02-2018, 06:17 PM   #32
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If I was going to do it, I would use thichened epoxy. It will cost more but it would be stronger. The cost of materials is not the over riding concern to me, the finished product is. A laminated panel will be much stronger than just nailing the panels together.
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Old 01-03-2018, 06:08 AM   #33
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If the roof is too shot to laminate ply (sealants/glue of your choice) the simplest is to use a core material.

On the Californian we used less expensive Nadia core 3/4 inch material on a flat concrete floor.

The camber was created with a 2x6 laid under the center with 2x4 a couple of ft. away to maintain a fair curve.

The lamination was 1 1/2 oz mat 3/4 oz woven roving and then another layer of mat.

It was allowed to cure overnight , then VERY carefully turned over so the inner portion was now up and glassed.

I am no fan of waxed resin so the unit was taken outside to sun cure.

As mentioned it was about 3 lbs per sq ft , so no fun to move.

The inside (the overhead when finished ) was lightly sanded and spray on rubber cement holds auto style roofing material.

The outside was lightly sanded (# 20 silicone carbide floor sanding discs) and painted with no skid.

Under a week to build ,and get up in place longer to trim and mount
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Old 01-14-2018, 05:45 PM   #34
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We jacked the fly bridge up from inside the cabin to get the ďsagĒ out, glassed down the coosa boards, screwed down edges until cured then took out the screws, lowered the jack inside and nothing moved up top! Solid fix and no more soft spots or water seepage issues. There are many uses for coosa board, strong, water absorption >1%, takes fiberglass well, nice addition to marine industry!
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Old 01-14-2018, 08:20 PM   #35
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Quote:
Originally Posted by Aquabelle View Post
The coosa board and glass will hopefully be a 1 and done repair. Also used it on a couple of soft spots on the deck. Good stuff, solid fix.


JimW: I hadn't heard of Coosa board before your post, but have now google'd it. Why did you choose it over 1/4" or 1/2" scarf-cut marine ply? Was it because it is a lot lighter but still stiff/strong enough to walk over, or cost, or easier to work, or....? I'm in early days of investigating alternative approaches to a partial ( I hope) core replacement on my flybridge/boat deck.



thanks ![/QUOTE]



Came at the recommendation of Hooks Marine Services (Pensacola Shipyard) they have used extensively with good results. Cost is much more expensive than marine plywood, but the structure, weight and nearly 0% absorption rate makes it superior to most other materials. Kind of a 1 and done. I was dealing with teak on the fly bridge that had soft spots and water would not drain off the deck as over time it had sagged a bit puddling water then weeping into the core of the fly bridge. No more teak, just a solid fly bridge of glass, slick coat and non-skid. Low maintenance and solid footing.
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Old 02-14-2018, 05:13 AM   #36
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Deck core

Hi Seamoose,
As you know I am currently doing this exact same job on my 34. Its construction is exactly as you described, a paper thin Fiberglass layer, 1/2 inch wood squares (off cuts I assume) and then a heavier top layer of glass. I ended up gutting out the whole top as I just couldnít leave a puzzle of luan up there. I too decided to cut the bottom layer as it had been damaged by me, and also to check out what was beneath it and if it had been effected by water ingress. There was no bracing needed as the framework seemed like it was carrying all of the load. I am about to go tomorrow and start laying it all back down. You will see pics on my thread as the project continues. I have sat there and pondered how they originally constructed it, and I have come to the conclusion that it was made in a mould upside down. The top layer of glass was very consistent, and the luan ply squares, although they varied in thickness, were all epoxied flat against the top glass layer, but the thin bottom layer was not flat, it followed the levels of the ply thickness. The only way this would be possible is if it was built upside down, meaning the thin layer was applied last, let to cure, flipped over and installed onto the boat. It was not glued or screwed to the structural timbers at all, it appeared to just float over the top, and secured to the cabin walls etc.
Was yours like this?
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Old 02-14-2018, 02:05 PM   #37
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Hello 34 Clipper!
Yes, this is EXACTLY how mine was put together and I have had the same, exact thoughts about how they built it. Structurally, it makes no sense at all.

My current plan (too cold here in Michigan to work on boats just yet) is to do the same, rip out all the luan blocks, and use marine ply, but have a physical connection to the bracing, not just floating in air.

At the same time I'd like to make a PVC pipe "chase" so I can run more wiring from the mast to the lower station.

Thanks Again

Will you post or PM me a link to your thread so I can see the pictures?
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Old 02-14-2018, 02:36 PM   #38
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What do you mean that it is too cold in Michigan? I have been working all through the winter on mine. Just have a propane heater or two...
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Old 02-14-2018, 03:09 PM   #39
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Deck core

Haha us owners must think alike, I have already repaired the structural beam at the step up to the top bridge, and in the process I added a 1 inch pvc pipe to do exactly as you described. I didnít want to run it toward the bow as I didnít want to weaken the structure, so I ran it from the centre where the mast is and ran it to starboard. It pokes down through the bottom of the deck next to the mast, and the other end pops up through the top but inside the Wall cavity of the flybridge structure (where your speakers are).
Iíll take photos today.
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Old 02-14-2018, 05:52 PM   #40
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What do you mean that it is too cold in Michigan?
At the Marina where the boat is they are only open 3 days a week, and not on weekends. Had I sprung for heated storage I could get in and work on it anytime, but the folks who store in heated would probably have a huge fit if I started making dust as that's where all the really expensive boats are.

But don't worry, I have an old farmhouse I work on during the winter.
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