re-coring balsa

cfretz · Post by **cfretz** » Mon Jan 09, 2006 12:39 pm

I found your site last night and was reading untill 1am. Theres alot of great info so let me throw my hat in the ring.

We are in the process of rebuilding a M-16 Scow from the 70's. Its a little race boat that scares the heck out of you on a windy day. i opened up a soft spot in the floot to reveal a few square feet of rotten balsa. Looks like the whole floor is wet but the majority is bonded to both skins and still strong.

What should i do? Its a race boat that i will probably outgrow in a few years. Its taken almost 30 years to get this bad. Can i just replace the rotten balsa and leave the wet untouched?

the deck is bad too so i cut a small hole(didnt want to mess up the nonskid) and cleaned out the core with a coathanger chucked in a drill.

I'm hoping i can pour a 2 part foam with low expansion properties into the deck. has this been done?

its open and i plan on leting it sit for a few weeks to air dry. Work will start by march to be done by june. Any advice or suggestions are appreciated. I am not looking to rebuild for the next 30 years rather the next 5.

I need a source of balsa around philly.

I posted an introduction in the boats section.

regards

Post by **Tim** » Mon Jan 09, 2006 1:37 pm

Hi Chris, and welcome!

I think you can repair your sole to the extent with which you feel comfortable. If you're not worried about longevity and resale, then a spot repair of the area you've opened will work fine in the short term.

Of course, the right way to approach this would be to redo the whole area, but I understand your feelings on this. Doing the patchwork repair will keep the boat going for a while, though the other areas will likely continue to worsen over time.

I'd be wary of trying 2-part foam in the deck. The expansion on that sort of material can be surprisingly powerful, and if the space is enclosed, there is the possibility that the foam could actually cause weak bonding in the deck to let go, delaminating the structure. Obviously, this is a worst-case scenario, but it's something to consider.

catamount · Post by **catamount** » Mon Jan 09, 2006 3:31 pm

Chris, for the part that has wet balsa, but the skins are still well bonded, one technique you could try would be to drill holes through one skin and into the balsa on grid pattern with approx 1 inch spacing (it's not critical to be precise). This is supposed to allow the core material to dry out more thorougly. When dry, you just fill the holes with thickened epoxy.

I'm not familiar with the M-16 scow, but I know with Laser's people open up the access ports in the deck and then put a lightbulb or two in the space between the hull and deck to provide a heat source to help dry the boat out. Also, keeping the air moving with a fan will help too.

FWIW, I ordered balsa from Defender.com for the re-core job on QUASAR, my San Juan 21.

Good Luck,

stone · Post by **stone** » Mon Jan 09, 2006 7:57 pm

Cant see the pics. The best prices for balsa and great service is http://www.mertons.com/. About 10 dollars cheaper on all sizes (4x2 piece) than Defender.

cfretz · Post by **cfretz** » Thu Mar 09, 2006 12:56 pm

heres an update.

the last pic really shows the extent of rot. we removed all the wet core and at least another 6" of dry to be sure.

theres still a bit more to come out but we should be done this weekend.

I picked up an old fridge compressor to try my hand at vacuum bagging the new core in. Are any of you around philly and experienced with vacuum bagging?