Wet balsa core repair options?

[john61ct]

Originally Posted by Cheechako

It isnt so much the hardness that's an issue, it needs to be closed cell foam which doesn't absorb much moisture. You can stand on regular styrofoam which is fairly soft and the PSI of your weight/area is likely higher than that on a deck.

And the good quality urethane pourable and sprayed foams are closed-cell.

But the low density say 2# / cu ft, is not structural, just for insulation and flotation.

The 8# stuff takes a whack with a hammer to break off big chunks of it.

So the latter is preferred. IF you could create a continuous open empty layer, it would be hard and strong load-bearing.

I'm not skeptical of the material science, but of the fact the rotten core is still there, blocking the new material from filling in enough of a void to become structurally significant.

Now maybe stripping enough of the weak old core out from below, then somehow forming the bottom half of a "mold" and then injecting the dense closed-cell foam, maybe that would work.

But at that point might as well use the traditional approach.

One thing I've definitely got out of the thread, is get the surveyor to really focus energy on this aspect when I'm shopping, so I never have to deal with it!

[Cheechako]

Originally Posted by Cadence

Don't even mention Styrofoam in the same breath with polyester resin. I can not speak to epoxy. Maybe a little off subject but Styrofoam turns into a noxious vapor went exposed to polyester resin. FYI

Yes it does! Turns into slime! I did not imply to use it in there. Just that even soft-ish foam like styro supports weight very well.

[clockwork orange]

Originally Posted by Kelkara

Can I ask a dumb question ... What is a moulded liner? and how do I tell if I've got one?

A lot of production boats built in the last 30 years or so have a full moulded fiberglass headliner that is often separated from the actual deck rather than the various other headliners on other boats such as fabric liners. Often they cover the entire cabintop, down the cabin side and under the decks out to the gunwhale in one piece effectively blocking access to recoring from the inside.

[john61ct]

Originally Posted by Cheechako

Yes it does! Turns into slime! I did not imply to use it in there. Just that even soft-ish foam like styro supports weight very well.

Compression, fully supported.

The 8# urethane has some tensile strength too, but ideally would get some embedded mesh for reinforcement.

_____
Anyone seen the "Poor Man's Fiberglass" PMF / Foamie trailer builds? Pretty cool DIY materials hacking there, super cheap and lightweight.

But OT to this

[Cadence]

Originally Posted by Cheechako

Yes it does! Turns into slime! I did not imply to use it in there. Just that even soft-ish foam like styro supports weight very well.

I didn't take it as if you implied using it. Sorry if I came across that way. I just thought it was worth mentioning since people hear foam and the first thing that comes to mind is Styrofoam if they don't know better.

[ramblinrod]

Originally Posted by Dymaxion

Quick questions...
Has anyone used a rotary cutter tool like "Rotozip" to cut through laminate layer?

Not really.

For cutting skins I use a:

A) Rotary tool (Dremel with a stone) to open hair line cracks and voids.

B) Hole saw for cutting round holes.

C) Multi-tool with saw blade to cut straight or curved for less than 8".

D) Circular saw with depth adjusted for longer straight lines.

E) Angle grinder with cut-off blade to for longer curved lines.

Cutting right through the composite is about the same, except for:

1. Dremel for less than 1.5".
2. Multi-tool with sawblade to about 3"
3. Jigsaw for 3-8".
4. Circular saw for straight 8" to 24".
5. Sawzall for curved 8" to 24".
6. Chain saw for greater than 24".

[john61ct]

Rotosaw will include the functionality of most of that list.

Just a matter of having the right attachments, bits and blades.

[Cadence]

Originally Posted by john61ct

Rotosaw will include the functionality of most of that list.

Just a matter of having the right attachments, bits and blades.

A good GRP laminate is brutal on blades. Going cheap is expensive.

[clockwork orange]

Originally Posted by ramblinrod

Not really.

For cutting skins I use a:

A) Rotary tool (Dremel with a stone) to open hair line cracks and voids.

B) Hole saw for cutting round holes.

C) Multi-tool with saw blade to cut straight or curved for less than 8".

D) Circular saw with depth adjusted for longer straight lines.

E) Angle grinder with cut-off blade to for longer curved lines.

Cutting right through the composite is about the same, except for:

1. Dremel for less than 1.5".
2. Multi-tool with sawblade to about 3"
3. Jigsaw for 3-8".
4. Circular saw for straight 8" to 24".
5. Sawzall for curved 8" to 24".
6. Chain saw for greater than 24".

Pretty much the same except we have an air powered Kett saw which works well too for straight cuts and you can hook vacuum up to it. I tend to avoid anything that I can't control the dust on, the multimaster kicks up very little dust so is easily controlled. I prefer to take a little longer cutting it out if I can keep the dust down.

Steve.

[ramblinrod]

Originally Posted by Cadence

A good GRP laminate is brutal on blades. Going cheap is expensive.

Precisely.

Going with too light of a tool wastes time and materials.

My customers would tend to dislike either.

Then there is the premature tool failure due to excessive running time (which comes out my pocket), so I would absolutely detest it.

[ramblinrod]

Originally Posted by clockwork orange

Pretty much the same except we have an air powered Kett saw which works well too for straight cuts and you can hook vacuum up to it. I tend to avoid anything that I can't control the dust on, the multimaster kicks up very little dust so is easily controlled. I prefer to take a little longer cutting it out if I can keep the dust down.

Steve.

Excellent point.

My written company policy is to leave every work site in equal or better condition than found.

I also use "dust collection at source" tools and practices where ever possible.

Else, one spends far more time cleaning up the project or work site than it would have taken not to make the mess in the first place.

[prof_mariner]

I gave the entire deck and cabin top a "hammer test". There were large areas of the starboard deck and cabin top (near the mast) that tapping sounded "dead". Otherwise the bow, cockpit and port side sounded fine and the entire deck felt solid except for one small area (maybe 3" in diameter) that felt like the gelcoat was loose.

The deck appears to have been repainted and there were many "spider web" cracks and crazing in the gelcoat / paint all over the deck and cabin top (see attached photos).

My plan is to remove all deck hardware and remove whatever wet core I can from the holes left. I'll decide what to do next depending on how much water I find and how bad the core material appears to be.

[ramblinrod]

Originally Posted by prof_mariner

I gave the entire deck and cabin top a "hammer test". There were large areas of the starboard deck and cabin top (near the mast) that tapping sounded "dead". Otherwise the bow, cockpit and port side sounded fine and the entire deck felt solid except for one small area (maybe 3" in diameter) that felt like the gelcoat was loose.

The deck appears to have been repainted and there were many "spider web" cracks and crazing in the gelcoat / paint all over the deck and cabin top (see attached photos).

My plan is to remove all deck hardware and remove whatever wet core I can from the holes left. I'll decide what to do next depending on how much water I find and how bad the core material appears to be.

Unfortunately, those photos do not look very promising.

Those radial spider cracks that appear like a hard-boiled egg tapped with a spoon, indicate rot or delamination below (not just wet).

The check cracks elsewhere may be:

a) A result of excessive gelcoat thickness (common in the 60s when builders were still to figure out optimum).
b) A really bad paint job
c) signs of more trouble below.

One, two, or even 10 spots like those radial spider cracks, say 6" in diameter and you could do spot repairs.

From a 6" diameter skin removal, one can gouge out 18" diameter of rot if need be, before you hit sound but damp core. Dry and flush that as I indicated, and you could be on your way in about 3 days. Just pack in core and thickened resin, re-skin, finish and you're good to go.

If the entire deck looks like that, and there is trouble below, that is different story.

Unfortunately, while the fittings leaked the DPO turned a blind eye, for likely 20 years or so.

Had the leaking deck fittings been removed and rebed within a couple years or as soon as these signs developed near the fitting, you would not have much work cut out for you.

Now I fear, you may have a lot of cutting out work ahead of you.

[prof_mariner]

Originally Posted by ramblinrod

Unfortunately, those photos do not look very promising...

...Now I fear, you may have a lot of cutting out work ahead of you.

I was afraid you were going to say that. These spider web cracks can be seen over most of the cabin top and the starboard deck. I didn't count them, but I'd guess there were well over a dozen, maybe 20 of them ranging from 4" in diameter to almost a foot.

When I first looked at the boat I was under the impression that the hull and decks were solid glass laminate. Seemed plausible based on the age and that the decks felt solid (no soft or spongy spots). I wrote off the cracks as a bad gelcoat / paint job.

But after seeing the report showing high levels of moisture in the deck I realized I needed to investigate this further. This boat comes from New England so it's very likely, as you said, the previous owner neglected to rebed the deck hardware and over time (and freezing temperatures) the core got wet, froze during the winter, and got worse.

The negotiated price for the boat is very attractive. I can access the cabin top from below (the head liner can be removed) but the side decks look like I'd need to work from above. I'm really tempted to take on this project but my better half thinks I'm crazy. For the sake of my marriage, I may pass on this one...

[clockwork orange]

Very few boats have solid glass decks regardless of how old they are, some older boats may have plywood core but there is nearly always some type of core. To help map out the wet core in addition to a plastic hammer you can now buy decent moisture meters by Ryobi from Home Depot for about $50.