Wet core

[higgs]

A cabin top deck fitting was leaking and I did not know until the headliner started dripping. Bottom line is the balsa core on the cabin top is soaked in an area just aft of the mast, encompassing up to 6 sq. ft. Cabin top - from on deck - is 1" solid glass with 1/2" end grain balsa backed with 1/8" matting. I am thinking with an inch of solid glass on deck, the balsa really is not needed to strengthen/stiffen the area. Thoughts?

 

[Chris Patterson]

Higgs, if you are thinking about building that area with glass and epoxy, or even resin for that matter, you could park a truck on it. An inch and 5/8" thick patch is going to be very, very strong.

 

[higgs]

I am thinking about cleaning the wet wood and then nothing. 1" glass cabin top seems to be probably more than most boats.

 

[Charlie Jones s/v Tehani]

With no coring, you'll more than likely start having condensation in that area in cooler weather. That's probably what the balsa is for - insulation.

 

[woodster]

this may very well be one of the few times Great Stuff spray foam is useful ...fill the cavity with it since you have such a thick glass layer

 

[Anonymous 121765]

I had the area around my mast base where the balsa had soaked & was really like mush. The deck had compressed slightly under the weight of the mast & the rigging tension.

I had a good glassman friend & we first used the sound method by tapping the deck until we got to what sounded like dry coring. WE drilled holes thru the top decking only to check whether wet or dry balsa showed up on the drill bit. We then taped off a rectangular area & then cut only thru the top decking to remove this piece intact for reinstalling later.

Vlad, my pal then made up a "mud" mix adding "Milled Fibers" for tensile strength to the mix. We filled the area & replaced the original decking skin. Vlad had a way of heating the skin to take out the sag & simply glassed it back in. He filled the drill holes & did his finish work. You couldn't tell where the cut piece was. This guy is REALLY good.

The upside, was that this area is now bullet-proof & tensile strong. If you find wet balsa that encompasses the mast, my advice is to remove the mast first. If so while you are at it, some water seepage if inside the mast could be from your wiring penetrations (like mine). There are simple solutions for this. If you go this route, start a thread for tips on re-doing the penetrations.

Here's a pic of the top deck skin re-attached before the finish work & new penetrations. The other pic shows the finished look after I re-painted the deck. No cut lines or drill holes can be seen.

CR

 

[jibes138]

Higgs,
On the Island Packet website they talk about using a mix with microballoons as a coring material. Here is an excerpt from their site:
"‘Our coring for our decks and interior liners is pretty unique.Instead of using conventional materials that are prone to rotand delamination, we actually make our own core in a liquidpaste form, made up of microballoons—tiny Ping-Pong balls—and resin. The beauty of the material is that it is chemically verysimilar to, and bonds aggressively with, the composite struc-ture, eliminating a major cause of delamination and allowing usto offer a ten-year warranty against deterioration, whereasmany builders are reluctant even to offer five.‘So we take polyester resin, mix it with the microballoons, cat-alyze it, and then apply it with a low-pressure spray gun; itlooks like shaving cream as it’s applied."
I'd give this a shot, mix some west epoxy with lots of microballoons this will keep the weight down and keep it waterproof. Good luck with the repair.

 

[Jackdaw]

Strength is not the issue here.

Assuming the depth to be filled was an inch (actually a bit less), you would need (6 x 6 x .083) THREE CUBIC FEET of resin. That's 22 gallons.

Get some plywood, and some mat.

 

[jibes138]

Jackdaw,
The AREA is 6 square feet, and the core is 5/8" thick. So 6 times .625/12 = 0.3125 cubic feet. Now the idea is to have a lot of microballoons and just enough resin to bind it all and to bond it to the top and bottom skin. So probably 75% microballoons and 25% resin 9just a guess) so .3125 times .25 = .078 cubic feet of resin. In a cubic foot there is 7.4 gallons, so .078 times 7.4 = 0.57 gallons. At about a hundred bucks a gallon probably 60 or 70 bucks. Using polyester resin will be a lot cheaper but may not adhere as well.

 

[py26129]

The IP core does work well. We just had a survey done this spring and the surveyor noted that the deck was sounded and felt brand new. No delam, or moisture anywhere.

Matt

 

[rgranger]

Not great-stuff---- fire block instead.

this may very well be one of the few times Great Stuff spray foam is useful ...fill the cavity with it since you have such a thick glass layer

Hey Guys.... I recently did an experiment with spray foams. I filled a 20 oz plastic bottle with foam and let it dry. Then filled it with water and microwaved it until just boiling. Then put it in the freezer till hard. Then let the water thaw and let the bottle sit for a week in the sun.

Great stuff got a little soft but the 3M fire block spray foam seemed untouched by the process.

If you decide to fill any gaps with foam... use this stuff instead of great stuff

 

[Jackdaw]

Jackdaw,
The AREA is 6 square feet, and the core is 5/8" thick. So 6 times .625/12 = 0.3125 cubic feet. Now the idea is to have a lot of microballoons and just enough resin to bind it all and to bond it to the top and bottom skin. So probably 75% microballoons and 25% resin 9just a guess) so .3125 times .25 = .078 cubic feet of resin. In a cubic foot there is 7.4 gallons, so .078 times 7.4 = 0.57 gallons. At about a hundred bucks a gallon probably 60 or 70 bucks. Using polyester resin will be a lot cheaper but may not adhere as well.

LOL You're right, I thought I read 6 x 6! More coffee!

 

[kloudie1]

Or use a foam core to replace the balsa and minimize other stuff and have it end up waterproof too.
http://www.jamestowndistributors.co...7&familyName=Core-Cell+A500+Plain+Foam+Sheets

 

[kito]

This is a 6 foot x 6 foot area? Has anyone tried using a 6" hole saw in various locations to dig out the rotten balsa? You can then spray in some kind of foam. I don't think "Great Stuff" would flow well plus sets up too fast. Seems easier than cutting the entire area out. You would then glass the plugs back in, sand smooth and cover with your favorite anti-skid.

 

[higgs]

Kito - great idea since I do not want to go in from the top since I would be cutting out a 1 inch thick piece of glass.

 

[mitiempo]

Kito - great idea since I do not want to go in from the top since I would be cutting out a 1 inch thick piece of glass.

Are you positive that the top layer is 1" thick? How did you determine this?

 

[higgs]

Determined top layer thickness because there is bolted through hardware which I was rebedding when I discovered the wet core.

 

[woodster]

Hey Guys.... I recently did an experiment with spray foams. I filled a 20 oz plastic bottle with foam and let it dry. Then filled it with water and microwaved it until just boiling. Then put it in the freezer till hard. Then let the water thaw and let the bottle sit for a week in the sun.

Great stuff got a little soft but the 3M fire block spray foam seemed untouched by the process.

If you decide to fill any gaps with foam... use this stuff instead of great stuff

thats good news ...wonder how it will work on a rudder repair....wonder if it would be very strong or should i say dense and firm

 

[DougM]

I thought that the Great Stuff was open cell foam which would tend to soak up water over time. May be wrong. A closed cell product would be a proper choice and rather than in spray cans, one of the kits that builders use would be easier to apply.

 

[dlochner]

A cabin top deck fitting was leaking and I did not know until the headliner started dripping. Bottom line is the balsa core on the cabin top is soaked in an area just aft of the mast, encompassing up to 6 sq. ft. Cabin top - from on deck - is 1" solid glass with 1/2" end grain balsa backed with 1/8" matting. I am thinking with an inch of solid glass on deck, the balsa really is not needed to strengthen/stiffen the area. Thoughts?

Is the mast deck stepped or keel stepped? A deck stepped mast needs a lot of support as it is subjected to tremendous pressures from the rigging. A keel stepped mast needs less desk support.