Balsa core in a Catalina?

[dfloeter]

Taking me by surprise, when I dropped the main cabin top hatch surround to paint it, I found an unmistakable layer of balsa core in the top deck.  And all along I have under the impression that Catalina never used balsa. I guess I need to check those cabin top bolt holes for good bedding compound.  I will have to read up on attaching photos straight my phone. 

[Noah]

I believe they replaced plywood core there with balsa core in 1996?

[Robert Mann]

If the outer hatch screws are not sealed properly a leak will cause the balsa to rot.  Keep an eye on that. I have a small weep hole drilled in each corner of the surround so water can drip if there is a leak, perhaps giving an early warning

[Ron Hill]

Guys : If you look at the Catalinas' "Deck Laminate and Reinforcement" diagram 9-26-01 recently posted on this Message Board - in the foot notes it says "#3  ADD BALSA AT WEATHER DECK" 11-13-97 !!!    also #1 "BALSA AT CABIN TOP IN PLACE OF 3/8" PLY"  No date listed .   Drawing # 340-24013-6

A few thoughts