Replacing balsa core - few questions

[slawosz]

Hi,
I started to replace some rotten balsa on my boat. It is near companionway, where halyards winches and jammers are attached. Then came lockdown and I started to have second thoughts if my plan is correct. Here it is:
* cut skin and remove balsa - done
* cleanup fiberglass with wire brush - done
* create bevel to reglass skin
* put new core (foam) in place
* put excess resin in place of fittings holes
* reattach skin

So I have few questions now:
* old skin is quite thin (2-3 mm, so I will have only around 50-60 mm of new fiberglass - is it enough? Or should I add lever or two on top?
* Near the edges, I removed balsa under the skin (by inserting wirebrush there) - I will have to squeeze skin there - I am afraid that I will create voids (I will add lot of thickened epoxy, but still)... - is it something to worry about?

Photo for reference:

 

[Keith-i]

Overall I think your plan sounds fine. I wouldn’t worry too much about small voids. I found when I repaired the cabin walls of my boat with new balsa core that just a single layer of glass made for a very rigid structure so 2 or 3 mm I’m sure would be fine. Certainly use thickened epoxy where the screws/fixings go through and bed your deck fittings down on butyl.

 

[Boathook]

I would use ply if you are putting back the fittings. Balsa can be crushed, where's ply will be much better. Also do a dry fit with the ply and drill the deck fitting holes in it. Take the ply out and re-drill the holes quite a bit bigger. When fibre glassing back in make sure that the holes are filled with resin so that when you re-drill them no wood is exposed. This will reduce the chance of 'rot' again.