How to Fill a LARGE Hull Void ?

[skipmac]

I am trying to figure out how to fill a large sump area in the bilge of my boat. In the Pearson 424/422 model there is essentially a hollow spot over the encapsulated keel.

This area is in the bilge between the engine and the mast step. It is about 10" lower than the rest of the bilge so this is the sump where everything drains. The Problem: this area is as inaccessible as the center of a black hole. The water tank is built into the hole leaving a small gap under and around the sides. Forward and aft of the sump access is blocked by plywood bulkheads that support the cabin sole.

Forget accessible, the area is not even visible, not even with a mirror on a stick. I can just barely fit a hose with a strainer on the end for a bilge pump pickup but beyond that, nothing. The bulkheads and the tank mark an event horizon beyond which anything that enters is permanently lost. Any matter on the boat that is dropped is inexorably attracted to the hole. Drop a nut on the bow and it will end up in the hole. Worst, I can't get in there to clean and the PO managed to spill old engine oil into the bilge which, added to 25 years of drips, spills and whatever it's pretty rank down there and inaccessible for cleaning.

So hopefully this makes my case for why so now the how. The space under the tank is about 1.5' X 3' X 3" and, did I say, inaccessible. I thought about pouring epoxy into the space but the tech adviser at West Epoxy strongly recommended against it due to concerns about bonding to the oil coated surfaces which I can't reach to clean.

So any suggestions? Anything that I could pour in there that would bond and not just create a trap for smelly grunge to collect?

[Cotemar]

The problem is nothing will stick to the oil. Oil holds bugs and smell.

How about power washing with soap a few times until it is clean and dry.

Then fill with epoxy.

[skipmac]

No way to power wash the area. I'm not kidding when I say inaccessible. I can just barely see a 2-3" section of the bottom of the sump that is about 3 1/2 ft long. The rest is under the water tank that is glassed into the hull.

Only idea I have for cleaning is to fill the thing with some kind of enzyme, cleaner, degreaser or whatever. The problem is with no access to scrub or rinse how effective will the cleaning be and would I get a bond.

I was hoping someone would know of something that might actually stick to oily, greasy, scummy fiberglass.

[boatman61]

Originally Posted by skipmac

No way to power wash the area. I'm not kidding when I say inaccessible. I can just barely see a 2-3" section of the bottom of the sump that is about 3 1/2 ft long. The rest is under the water tank that is glassed into the hull.

Only idea I have for cleaning is to fill the thing with some kind of enzyme, cleaner, degreaser or whatever. The problem is with no access to scrub or rinse how effective will the cleaning be and would I get a bond.

I was hoping someone would know of something that might actually stick to oily, greasy, scummy fiberglass.

I reckon you'd get away with a hot tar and gravel mix ok.... think you'll find there's a fair amount of chemical compatability...

[IrishLass]

One way to fill the void (although I am not sure it will bond with a dirty surface) is to mix up some A/B foam and pour it into the space, allowing it to expand to fill the void. Excess can be trimmed with a knife or saw. The foam is available in different densities. We use it to fill similar voids in the bilges of the boats we build. Also, I used the high density version of the foam to fill the rudder on my Tartan 37. You can buy the foam from Composites One, North American Composites or other fiberglass supply houses.

[osirissail]

Simply put if the area is "inaccessible" you need to make it accessible by carefully planning out to remove the cabin sole above the area. Then you can assess whether the area is clean or not. If it is clean then you can fiberglass in new bulkheads fore and aft then fill the area with floatation foam (the professional 2-part stuff). Then fiberglass over the filled in area to make a totally sealed area. Then put the cabin sole back into place.
- - You need to consider if any pipes/hoses/wiring or anything else transits the area before sealing it off.

[skipmac]

Originally Posted by IrishLass

One way to fill the void (although I am not sure it will bond with a dirty surface) is to mix up some A/B foam and pour it into the space, allowing it to expand to fill the void. Excess can be trimmed with a knife or saw. The foam is available in different densities. We use it to fill similar voids in the bilges of the boats we build. Also, I used the high density version of the foam to fill the rudder on my Tartan 37. You can buy the foam from Composites One, North American Composites or other fiberglass supply houses.

I thought about foam but is it resistant to bilge slime, engine drippings, bilge cleaner and whatever else may inadvertently end up in the bilge? I of course endeavor never to do this but seems like occasionally some diesel or oil can drip (plan to build an isolated pan under the engine soon as I can). I have this horrible vision of an inaccessible spot filled with half dissolved, melted foam goo.

Even if it doesn't melt on contact with whatever ends up in the bilge it would not leave a nice, smooth cleanable surface. My previous experience with foams is there are lots of cracks and crevasses that would collect dirt and more grunge.

[skipmac]

Originally Posted by osirissail

Simply put if the area is "inaccessible" you need to make it accessible by carefully planning out to remove the cabin sole above the area. Then you can assess whether the area is clean or not. If it is clean then you can fiberglass in new bulkheads fore and aft then fill the area with floatation foam (the professional 2-part stuff). Then fiberglass over the filled in area to make a totally sealed area. Then put the cabin sole back into place.
- - You need to consider if any pipes/hoses/wiring or anything else transits the area before sealing it off.

Making access would require destroying the cabin. The water tank is glassed in over the top of the sump and under the settees and the galley. Without tearing up the cabin the only way to gain access would be to cut open the top and bottom of the water tank to get to the space under it.

Nothing passes through the area so that's not a concern. Even though I cannnot see into the sump I can see the front and back.

[s/v Jedi]

People are saying to completely fill up this area and cover with epoxy for gas tight sealing. But you can't do that because you have a tank mounted in that area.

It simply means that you have to remove all that's in the way.

ciao!
Nick.

[skipmac]

Originally Posted by s/v Jedi

People are saying to completely fill up this area and cover with epoxy for gas tight sealing. But you can't do that because you have a tank mounted in that area.

Exactly!

Originally Posted by s/v Jedi

It simply means that you have to remove all that's in the way.

ciao!
Nick.

No, no, I don't want to. I want the easy solution.

I already have major parts of the boat disassembled and have plenty of big projects to do for now. Besides, what is in the way is pretty much half the main cabin and I don't think the payoff justifies removing the floor and cutting my water tank into tiny pieces.

There just has to be some kind of resin that I could pour into the hole that will harden, leave a nice, clean, flat surface and stick to the greasy fiberglass.

[atoll]

i think boaty nailed it hot tar will stick to any thing ,failing that a cement mix,it will not stick to any thing but will fill the void and should you ever need to remove the tank,should slide out

[skipmac]

Since a picture is worth a thousand words (in my case probably worth two thousand words) I tried to sketch out the area in question.

The drawing is more or less to scale, at least in regard to the sump and water tank. There is an access hatch in the sole just forward of the tank (about over the leading edge of the keel) and just aft of the tank I left out the engine room where there is no sole and a small crack open just forward of the aft floor support and where I can look straight down to see about a 2-3" strip of the aft end of the bottom of the sump.

Removal would require outright destruction of the main cabin one way or another. Think I would rather buy another boat or just leave the hole where it is than to go that route.

Hate to use a really tired cliché but I believe I have already thought about the obvious solutions so trying to (are you ready, a little drum roll) think outside the box (I can hear the chorus of groans from here).

So my last desperate ideas:

1. Is there any wonder cleaner that I can just fill the hole and it will take away all the nasty off the fiberglass so I can get a wonderful, perfect bond and just pour in the appropriate epoxy mix?

2. Is there some kind of wonder goo that will stick completely and reliably to nasty, oily, slimy fiberglass?

3. Have I found a situation where you can't get there from here?

[skipmac]

Originally Posted by boatman61

I reckon you'd get away with a hot tar and gravel mix ok.... think you'll find there's a fair amount of chemical compatability...

Looking at what I've been cleaning out from under my fingernails since the weekend I think tar is pretty much what the bilge grunge has become. Thanks for the suggestion but think I've got enough tar in the bilge already.

[Johnathon123]

Maybe, and I am just spitballing here, next time the boat is on the hard, cut through the hull, clean and fill, glass it back up

Shouldn't need that big a hole.

Like I said just spitballing

[skipmac]

Originally Posted by Johnathon123

Maybe, and I am just spitballing here, next time the boat is on the hard, cut through the hull, clean and fill, glass it back up

Shouldn't need that big a hole.

Like I said just spitballing

Well actually am on the hard for a major refit (the photo on my post is current). The sump is in the top of the keel where the glass is really thick and in a critical structural area. I'm just not too keen on chopping a hole in the side of the boat, especially there.