Soft deck spot repair: Never do anything for the first time!!

[PSR]

So sad that on Tuesday I started to address the soft areas on the foredeck. First discovered this problem when I noticed a cracked more-or-less heel sized damaged spot on the starboard side.

You can see the impression above the bottom left edge of outline.

The outlines include the area identified as soft with hammer taps.

Following the advice of Allan Vaitses (The Fiberglass Boat Repair Manual) I am getting to the core from the interior. I’m cutting with a DeWalt oscillating tool with semicircular blade. I thought this would be safer and cleaner than a mini circular saw, although a small saw would have had depth control, which the oscillating tool does not. Here is the result:

You can see I made a mess of the cuts. A mini circular saw probably would have been been better. Anyway, the tip of the triangular area easily pulled away from the core and broke off from the larger area. The rest of the triangle, which points forward, is firmly attached to the core.

I’m not sure what to do next. The soft area outlined on the deck can’t be fully exposed yet, but the strong attachment of the headliner to the core makes it seem like overkill to rip it all off.

Damaging the interior of my boat this way hurts, but at least some of it needs to be done. I’m just not sure how far to go. Any thoughts will be most welcome.

Peter

 

[jssailem]

Peter. What is the material of the core. Balsa or plywood?
In the area that has been exposed, what is the condition of the core wood? Wet and soft crumbling in your hands or solid just no longer connected to the fiberglass?

With core issues there are many ways of going. First and foremost you need to establish the type of damage. If the core is rotten, then removal is the only option. If it is just a local leak and just separated from the fiberglass deck, once you get the moisture removed, you can introduce resin to solidify the wood and then pump in thickened resin to fill the space between core and deck for a serviceable repair. Key is to stop any more moisture from getting to the area. Means you have to find and stop the leak.

 

[DeniseO30]

From the bottom is most definitely the most difficult of all the ways to repair a wet core this is why so many people do it from the top and deal with the issues, and a lot of people don't realize if it's a large deck area that has to be redone, it also need a supporting structure keep things in proper shape and dimensions.

 

[PSR]

Thanks for the thoughts jssailem & denise030. The area of concern is shown in my photos of the deck. It isn’t large. Today I lit up the area revealed by the broken off liner.

You can see the core and it is plywood that looks practically new. So no rot or decay. It is 40+ years old!! The delaminated piece of liner was the way it was left when built. The thickened resin did not fill here between liner and core. If you look closely there is a lump of hard clear resin in the middle that probably contributed to the issue by separating the liner from the core. Here’s the inside of the piece of liner

I
There’s no thickened resin on the glass. What’s more, the glass is poorly impregnated with resin. There were lots of voids in the glass on the hull when I looked, and we repaired all of these. I’m suspicious that the other soft spots result from poor glass work.

I do not want to tear the boat up any more to find construction issues. I will inject epoxy under the deck in the soft areas, repair my interior damage, and call it done. She’s an old, good boat, and although I prefer perfection, this does not look like the normal core deterioration that would demand a full court press.
Now I have to figure out how to inject the soft spots effectively and how to repair the damage I’ve done to the liner.
Still interested in your thoughts.
Peter

 

[Johnb]

Take courage,it may not be as bad as you fear. We did a big project to replace all the portlights and had to deal with a lot of water damage in the plywood. Once we scraped out all the soft wood I went at it with a hair dryer and then just left it for a few weeks. (I made up temporary covers so I could do several at the same time). After they were dry I filled in with G10 and thickened epoxy and I believe it is better than original.

Also I think the oscillating saw is the right tool. FWIW my Bosch has a depth control attachment. Maybe there is one for yours. It removes a minimal amount of material which means less dust and easier repair. It seems like the scar is going to be way forward in the vee berth, not so bad.

Good luck

 

[PSR]

Good luck

Thanks Johnb, and thanks for your thoughts.

As I wrote earlier today, there’s no rot in the plywood I can see. It looks like new! …and that’s good!! I think the issues have to do with bad fiberglass/resin work during construction, and I’m going to fill what are probably resulting cavities under the foredeck with epoxy resin. I just need to figure out how to do that and figure out the best way to repair the damage I have done to the liner.
Cheers!
Peter

 

[DeniseO30]

Because the deck gets hot it's more likely the bond between the fiberglass polyester and plywood core will release even though the plywood or core may not be rotten

 

[dmax]

"Now I have to figure out how to inject the soft spots effectively and how to repair the damage I’ve done to the liner. Still interested in your thoughts."

Injecting will be tough, probably want to drill some holes up to the underside of the deck and use a syringe to inject thickened epoxy and then tape over the holes - gravity will be working against you so it will be tough to insure good adhesion. You could end up creating a bigger mess. I think you would be better off removing the core in the soft areas (even though it is solid) and replacing it so you know it is attached. JudyB in this thread shows how it can be done from underneath:

soft area starboard fore deck

Soft Foredeck Does anyone know if there is wood or foam in between the glass in the fore deck construction over the v berth ? foam ? balsam? I also have a small soft fore deck area on the starboard side of my O'day 25. Was planning on drilling a series of holes and...

forums.sailboatowners.com

As far as covering the damge, you could get a 3/8" sheet of Azec (PVC lumber) and fashion a nice cover with rounded edges that would look decent.

 

[PSR]

As far as covering the damge, you could get a 3/8" sheet of Azec (PVC lumber) and fashion a nice cover with rounded edges that would look decent.

dmax-thanks for your thoughts, especially for the suggestion regarding cleaning up the interior damage. Nice idea!
Peter

 

[PSR]

In the area that has been exposed, what is the condition of the core wood? Wet and soft crumbling in your hands or solid just no longer connected to the fiberglass?

Thanks again is for your response and for so many consistently useful posts to other threads!! The core is plywood and it looks sound where I’ve exposed it. The distribution of soft area of the foredeck makes me suspicious that other soft spots are similar results of poor construction, not core deterioration from a leak or leaks, because the spots are isolated from fittings. So I aim to inject the soft spots from below somehow. Dmax pointed me to Judyb’s post showing her solution to what may have been a similar problem. I’ve looked there and the repair does involve complete removal of the core. Any other thoughts?
Peter

 

[PSR]

As far as covering the damge, you could get a 3/8" sheet of Azec (PVC lumber) and fashion a nice cover with rounded edges that would look decent.

Dmax Thanks again for your thoughts. Any reason you suggest Azec specifically? I guess it has more structural strength than easier to obtain material like Komatex pvc board…

 

[dmax]

No real reason for Azec other than it is high quality (and more expensive) - anything you like will do, just throwing out a suggestion. Doesn't need to be strong.

If you really don't want to dig out the core and you are sure it's dry, you can try to suck the resin in by creating a vacuum. Drill a few holes in strategic locations, use rubber plugs to plug up all but two of the holes, apply a vacuum on one of the open holes and inject epoxy in the other. Then move on to the other holes. You'll have to be creative on how far apart the holes need to be to be able to pull resin through - maybe 3 - 6 inches? It also has the potential for creating a big mess so you'll want to cover everything below. I would probably use slightly thickened epoxy (i.e. not to mayonaise consistency, more like motor oil) - you need a balance between too drippy and too thick to flow. To create a vacuum, you want something like this:

2.5 CFM Vacuum Pump

Amazing deals on this 2.5Cfm Vacuum Pump at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

You can then get some 1/4" tubing that will become your sucker hose (cheap PVC hose works, can't be too soft or it will collapse under the vacuum). You will probably need a brass fitting with a barb for the vacuum pump to attach the hose to the pump. On the other end, wrap some butyl rubber around the hose about 1/2 inch from the end, stick the hose into one of the holes and press the butyl in to seal the hole/hose. Turn on the pump and you are good to go. Incidentally, I have used a vacuum pump to suck moisture out of my deck core (high moisture content but not to the point of rotting) - worked a treat. If I were doing it, I would measure the core for moisture content (buy/borrow a moisture meter) and if it was at all elevated (15% or above), I would start with one hole and apply a vacuum and get as much moisture out as you can. It's not a quick process, I ran the pump on my deck for about 60 hours in the worst area. Warmth is your friend so letting the sun heat up the deck will help. You should be able to get close to 30 Hg (good to have a pressure gauge to measure, check for leaks) - at that pressure, water will boil at 70 degrees farenheit allowing the pump to pull it out as vapor. When I did mine, the decks were 120 - 130 degrees from the sun.

 

[PSR]

Thank you so much for your detailed advice dmax. I'm not certain that the core is dry under the soft area (which is not extensive). Moisture may have entered in the cracks around the depression that made me look for soft spots. My only other evidence is that there was a void above the liner in one of the locations, where the plywood core looks practically new. and that the soft areas are not associated with any fittings. They seem to be isolated. Given the sub-par fiberglass work in that spot and in other parts of the boat, I will bet on resin voids as the culprits. My plan now is to fill the cuts I've made with West System Six10 thickened epoxy and to use that to replace the piece of the liner that is broken out also. I have not used Six10, but I have a lot of experience with West System epoxy. The Six10 application looks like a good one to force the adhesive up into the cuts, and it has an adequate working time to clean up around the cuts before it sets. After that, I will consider how to get something into the rest of the soft areas. Vacuum seems good, and I appreciate your detailed description of how to do that.
Cheers!
Peter