Wet Decks - Buy or Fly?

[Jules_M]

Originally Posted by odonnellryan

but I will probably test out injectadeck to see how it works. I was considering either that solution or to drill it out and fill with epoxy.

I emailed Practical Sailor asking them to test Injectadeck. They replied they would look into it. Maybe they need a little more nudging...

As for Allegro II, that deal is dead.

[epoxyman]

So I love to read these forums( I learn a lot) but I typically don't add my 2 cents, however I think I can help with this forum and not detract.

I have rebuilt 7 older sailboats (newest was 1981) in the last 16 years, and I run a composites research laboratory and teach composites at the University level (means I have made a bunch of mistakes and hopefully learned from some of them).

On a Whitby 42 I had to cut out and repair two 4 ft by 6 ft sections where the dorade boxes failed over time and allowed moisture to destroy the balsa core in the coach roof. The yard estimate was $30-35,000 (2009). I did the work including repainting and non-skidding the deck for $3,000.00 - project took about 80-100 man hours. I used the project as a basis for teaching a repair course.

I think the first thing to address is; "What is the role of the core on the deck?"
A sandwich composite structure (2 FRP skins separated by a core) acts like an I beam - separating the skins increases the stiffness of the structure by 300-700 times (based on distance of separation). The skins (flanges) resist the bending while the Web (core) takes on the shear forces. If the skins are no longer bonded to the core then the I-Beam no longer functions. So to properly repair the rotted core (if it is balsa) and have a successful I-beam, the structure must be properly repaired.
I like the idea of using a moisture cured urethane, however you would have to drill enough holes to truly REPAIR the structure. The skins must be bonded on both sides to the WEB (core). Depending on the severity, the you may have to drill a network of holes 3- 6 inches apart (picture in video was close). This will result in quite an ugly deck unless you then repaint the entire deck.
A lot of moisture intrusion is cosmetic Vs. catastrophic (degrading the structural integrity of the boat). Depending on where it is located (near mast or stays, as an example), and how you plan on sailing (cocktails at the dock or open water), how you repair will be critical.
If you are going to SAIL, and the disbonded (no longer valid I-beam) areas are in critical locations - repair it correctly, or walk away.

[john61ct]

Originally Posted by Scout 30

Injecting epoxy into a wet core is pointless. Epoxy is a great product but it does not react well to moisture & will never stick to anything wet.

I agree, but this product claims to **only** work with moisture present, formulated specifically for that, won't work with dry cores.

Not saying I believe this product is effective,

just that there **are** such adhesive / sealant systems that require moisture cure, even those designed to work underwater.

[Scout 30]

Originally Posted by john61ct

I agree, but this product claims to **only** work with moisture present, formulated specifically for that, won't work with dry cores.

Not saying I believe this product is effective,

just that there **are** such adhesive / sealant systems that require moisture cure, even those designed to work underwater.

I was responding to Ryan's post saying he would either use injectadeck or drill & epoxy. If the core is completely dry squirting epoxy into it would make sense as it would stick to the upper & lower skins but a wet core will never dry out unless one of the skins is removed.

I think injectadeck would work if it does 3 things:
1. Adhere to both the upper & lower skins.
2. Create a core that is dense enough to be structural.
3. Remove all of the moisture that is present.

I think it might succeed with 2 & 3 but 1 would be a challenge due to the rotten core residue that would be present. I think it would probably adhere to the upper skin in some places but less to the lower skin.

[Scout 30]

Here's a thought, what about injecting 5200 into the core? Anybody who's used it knows it sticks to everything including skin, clothes, hair, etc & we all know what the tubes are like when it cures in them, very hard & dense. Plus it needs moisture to cure. Hmmm

[john61ct]

or best of all do it right so you don't need to keep revisiting the issue