Coring material

[unbusted67]

Hello I’ve got a soggy section of balsa I’ve got to replace but i don’t want to lay balsa back in. I think the stuff sucks and I’m not 100% certain that I’ve found the source of water intrusion so why put something back in that could get soggy again?

What should I use? It for a cabin top and there is contour to it so I’m wondering if I should get something pre scored?

[Matt Johnson]

How much of a curve are you dealing with? 1/2" foam coring contours easily to a pretty good radius without scoring -- to a larger radius than a typical cabintop. Each cut in the scoring should be filled when you lay is, so it's an extra step/cost if you don't need it.

[CharmCityBoater]

May I suggest watching this? Short answer, Divinicell.

https://youtu.be/Bqb7iA6AG-g?si=HB9kW6A4sW2LowdK

[SVQuestOfPaget]

Not that it's much more rot resistant than Balsa, but you can lay in two 1/4" sheets of marine plywood as well - will be heavier and you'll still want to pour an epoxy annulus before using any bolts or screws through it. You shouldn't have to score it at that thickness, but it may need temporary screws as you lay it in. Just another thought. Regardless, best to find where the water is coming in before you do any kind of repair.

[catsketcher]

I have had this problem with my cat - small sections of Duflex have gone soft. I peeled off the top laminate of glass (used a grinder with a cutting wheel) and then used a chisel to scoop out the soggy balsa. Then I laid in some foam. I did not get too worried about the details of the core. I made up a runny epoxy mix - micro balloons with tomato sauce consistency and pushed that into all the hidden corners (I didn't cut all of the top off - I found some more soggy balsa). Then I pushed different pieces of foam into the void and wiggled them in - pushing down on the filler and into the sides. Keep on pushing the pieces of foam in - ensuring you have a really good bond with the lower laminate. Then go over with a thick epoxy filler mix - squeezing filler in all the gaps between the foam pieces.

Then I used a 7 inch sander polisher to clean up the top and grind paint off the surround laminate on the edge of the cutout. Next step was laying down the new top laminate and then filling and finishing.

I would use foam and epoxy if possible.

[unbusted67]

Originally Posted by CharmCityBoater

May I suggest watching this? Short answer, Divinicell.

https://youtu.be/Bqb7iA6AG-g?si=HB9kW6A4sW2LowdK

Jesus. This is fantastic.

[CharmCityBoater]

Originally Posted by unbusted67

Jesus. This is fantastic.

Yep. Fantastic channel. Good analysis and details.

[coopec43]

Originally Posted by catsketcher

I .......... Then I laid in some foam. I did not get too worried about the details of the core. I made up a runny epoxy mix - micro balloons with tomato sauce consistency and pushed that into all the hidden corners (I didn't cut all of the top off - I found some more soggy balsa).

I would use foam and epoxy if possible.

What sort of "foam"? Did you get expert advice or is it your own solution? Is the yacht still going alright now?

[coopec43]

Originally Posted by unbusted67

Jesus. This is fantastic.

I have no problem with Divinycell as my deck is cored Divinycell. The hull is Airex.

I used Airex on the hull as it can absorb shock load but it tends to soften in heat. (I used Divinycell on the deck for that reason)

But there are lots of core materials - Airex, Divinycell, Klegecell, Balsa

https://www.practical-sailor.com/wp-content/uploads/2020/02/HULL_CORE_COMP_1007.pdf

[boatpoker]

or Corecell ... anything but plywood.

[coopec43]

Originally Posted by boatpoker

or Corecell ... anything but plywood.

OR BALSA!

Corecell "absorbs negligible water"

The Roberts Mauritius 43ft yacht (solid glass) has a designed weight of 12193kg. The Tammy Lift operator told me Helen weighs 11.6 tonne That is a big weight saving