core material

[bletso]

Is this a normal method of coring. I have seen this on the vertical cabin wall and on the aft cabin deck. I was trying to dry it out and it really wasn't working so I lifted it up. I am thinking it would be better to replace what is there with a solid piece of 3/4 marine ply. It is not a large area.

 

[Ross]

If it is flat then you can use a continuous sheet. Best if you use pressure treated. If it is not flat then you can use small blocks. This looks like a home made repair.

 

[Cool Beans]

I've seen the small squares of plywood come out of cores on old boats on a few different sailors blogs. . .but they didn't have nearly the amount of resin between the squares like that. . .

I personally wouldn't used pressure treated for a core. I have never found pressure treated anything that wasn't soaking wet. . .

 

[Ross]

I've seen the small squares of plywood come out of cores on old boats on a few different sailors blogs. . .but they didn't have nearly the amount of resin between the squares like that. . .

I personally wouldn't used pressure treated for a core. I have never found pressure treated anything that wasn't soaking wet. . .

Probably haven't bought enough then.

 

[Old Skool Neil]

Why not use exactly what the better builders used for decades, 5/8" end grain balsa core? It's readily available and manufactured specifically for this application.

The only contraindication would be in the areas of hardware installation due to compressibility. Plywood or no core should be used in those immediate areas.

 

[Ross]

You can find it here: http://www.duckworksbbs.com/

 

[CalebD]

If you don't want to use wood for the core then consider this polypropylene core material:
http://www.expresscomposites.com/honeycomb.html
Costs about the same as a good plywood and less than Balsa core.

 

[25yearslater]

I was reading through the honeycomb bonding method as I had considered it. The one drawback to it was in order to get a satisfactory bond vacuum bagging was the preferred method. The stuff is amazing for strength and ability to resist moisture but other than small areas I was intimidated by the bonding method. I also have a post on plywood. I think it needs repeating. Exterior and other plywoods do not have cores that are free of voids, splits and plugs. Marine plywoods use "BOILPROOF" glue where water resistant glues are used for exterior and pressure treated plywoods. The atmospheric moisture will accumulate in these imperfections and in time begin to delaminate the terrestrial plywoods as well as the structural components being less certain. Can they be used with success? Some have had good luck. Depends on your risk aversion. Just something to consider.

 

[bletso]

If it is flat then you can use a continuous sheet. Best if you use pressure treated. If it is not flat then you can use small blocks. This looks like a home made repair.

Definitely not a repair. I have this same construction in the cabin area. It was constructed this way. Boat was made in Taiwan in 79. It is saturated due to deck screws leaking through. The squares are plywood squares 2 inch square. Once you have water ingress, it is virtually impossible to dry out without opening it up. Water seem to flow along the ply filler interface. It isn't rotted, just soaked and of course the bond is then bad.

 

[Charlie Jones s/v Tehani]

I'd certainly use epoxy in the repairs, and I've found that epoxy doesn't always play well with pressure treated.

The gaps between the pieces of core are terrible.

Balsa would work, as would Plywood, or kedgecell. Personally, I now use the kedgecell but also have used a good marine ply as a core.

 

[Ross]

I have had Kledgecell, Airexcore and Corecell and I could break kledgecell with my fingers and but corecell and airexcore would only bend. I used a couple of hundred square feet of aiexcore on the inside of Bietzpadlin when I refitted her.