I’m almost done with the RG-65 I’m building, and I’m begining to think that I seriously went overboard with the way I reinforce it.
I used balsa with all the reinforcement, and cover each one with fiber on both sides. I’m finding building guides now that only use bare balsa (waterproofed of course) as reinforcement…
Should bare balsa be enough?
My boat is 25.6 inches LOA and 8.6 inches Beam (yes, I know I over did the beam also, but I was looking for more interior room for sleepovers and weekend cruises…)
Some years ago (actually it was 1978 - and I was still at school) I built a 24" hull out of balsa. The hull itself is only about 1.5mm balsa and the internal strengthening is just balsa - including the keelbox. The thicknesses of the internal balsa varied depending on expected loads. For many years the hull exterior was just waterproofed and painted, but a few years ago I applied a light layer of fiberglass to the hull to toughen it up for my kids to sail. No fiberglass inside at all. It’s still going strong after 27 years. It was a free sailing model but I currently have the deck off to convert it to RC, and will be adding a new keel to get the ballast lower and lighter (to compensate for the weight of the RC gear).
So if built sensibly and assuming the balsa you are using is appropriate, I’d say you don’t need additional fiberglass.