SEMI-PERMANENT CORE ROT REPAIR
David Whyte, #397, Mandara
if the area is not too large, you can make a semi-permanent repair to get by w/o cutting off the skin.
find a source of empty caulk gun cartriges--they do exist for sale, but you may have to dig for them...as example there is only one place in the seattle area you can get the things.
Epoxy can be thinned with acetone until it's darn near water thin if you like. takes a long time to kick off all the way, but it will.
Mark out a grid over the area you want to firm up, and drill a scad of 3/16" holes on, say, 1-1/4" or 1-1/2" centers. use the caulk gun and jam in as much thinned epoxy as it will take....you'll have epoxy coming out the neighboring holes...it's a messy job for sure. as time passes in the next day or so, you may find much of the epoxy has run away inside...if so, hit it once more.
You can do this with big syringes, too, but it's a pain and you'll go thru quite a few...it's well worth hunting up the caulk tubes.
FWIW, MANDARA's coachroof is largely good, with a few smallish and local soft spots. rather than hassle recoring it, i've got 3 dozen caulk tubes (well...they're cheap, and i'd rather have too many!) and a gallon of acetone to go with the resin. figure to saturate the thing with thinned out resin and call it good.
I wrote before about soaking a punky skin with thin epoxy, and Ray even put it in the MIR...I need to follow up on that. It certainly does appear to work, I've done it before and might again...but I have to add, having taken apart my work afterwards now, that I am not impressed by the lack of penetration/saturation of the balsa. It does indeed solidify the rotten areas, and it does indeed stick the skin back to the balsa...but I wrote it as "semi-permanent core rot repair", and that is definitely all it is. We decided to not be stupid after we had already done it to the mainly OK feeling/sounding coach roof, and respect the fact that we are dealing with a spore, after all, which likes to travel...so we had best put the Nida everywhere all at once and not have to think about opening her up again.