Bilge redo ideas please!

[albertjizhang]

Hey guys!

I have been sanding and grinding the bilge of my Dufour 35 lately, as there had been bilge water and waste diesel held up in the bilge to the verge of overflowing for a couple years, and I find lot of places with delamination and rotted laminate.

During the grind down, I find the bridge structures over the bilge( I’m not sure if they count as bulkheads), they are glasses onto a layer of laminate, and that layer of laminate is separated from the hull, and the space in between has been filled with oil and filth and moisture, and has all turned black
I’ve sanded all the delaminating glass off of the surface, but the parts under the “bridge structure” I cannot reach and cannot clean. The topside of the “bridges” are sound, but when I reach inside, I can scoop out oil and peeling glass fibre.

I’m leaning towards removing the “bridges” so that I can clean the hull properly and lay new glass directly on the hull, at least to cover the thickness that had rotted and has been sanded away. Then rebuilding them with plywood and epoxy. But I prefer hearing your opinions first before getting into action! Thank you very much.

[Don C L]

It appears to me those frames are not supporting the structure of the hull and are there to support the cabin sole. They may have been loose for quite a while, right?

[SailingHarmonie]

This again?

Your boat was built in two pieces. The hull, and a liner. It was built this way because it was cheap to do so. The parts you want to remove are integral to the structure of the liner. They can NOT be removed without compromising the structural integrity of the boat.

I can assure you that NOTHING was added to your boat that wasn’t required. It was built to a budget price point, and you remove parts at your risk.

What you are proposing is the equivalent of the homeowner cutting away the load bearing wall because it is in the way.

[fourlyons]

Originally Posted by SailingHarmonie

This again?

Your boat was built in two pieces. The hull, and a liner. It was built this way because it was cheap to do so. The parts you want to remove are integral to the structure of the liner. They can NOT be removed without compromising the structural integrity of the boat.

I can assure you that NOTHING was added to your boat that wasn’t required. It was built to a budget price point, and you remove parts at your risk.

What you are proposing is the equivalent of the homeowner cutting away the load bearing wall because it is in the way.

I read the OP's post differently. I understand they are considering removing the grid, cleaning and adding glass to the hull, then reproducing the grid in ply and epoxy (and presumably fiberglass). This is a perfectly good plan, as long as they reproduce what's there. I would not use plywood, but instead use foam as forms.

[Nekton73]

I am not familiar with the structural design of your boat, but agree the pictures appear to show the 'grid' as independent of the hull and there for the purpose of supporting the cabin sole. The look like other floor grids I've seen that are premade shapes glassed into place after the hull is laid up. If you want to go to the trouble of removing them completely and then rebuilding exactly what you have with new material I see no issues, other than a lot of work, but if this is a labour of love and pride then it may be worth it.


If you would consider a less labour intensive option, perhaps do your best to clean everything you can, dry out everything (if you are in warm climes then a fan to move air should suffice, if colder, then a heater plus fan), build out the sides with a thin additional piece of laminate (1/4" ply if you wish) and then glass everything solid and nice. Finish with your choice of bilge sealant/paint. This will keep the original structure in place, seal any holes, and add strength.

[Cyrus Safdari]

You basically want to make the floor grid or liner integral to the hull? Great ideal. You don't really need to rebuild the grid from stratch
I am a fan of using expanding marine foam in inaccessible places to plug em up, keep out junk
The strength of the floor grid or liner is not in its core ( probably hollow) but in the layers thickness and beam shape of the fiberglass on the exterior. An easier fix is to seal up all the holes and gaps between the grid and hull interior with tape, pour expanding marine foam in the hollow areas of the grid structure (drill pour-holes from top into the grid core), and then glass over the whole structure (with fillets as needed), making the grid and hull interior into one piece. If you pour the foam in small increments, it will find the lowest point and expand to remove air gaps under the grid, and though some foam may initially leak it will self-plug eventually just make sure the tape job is well done so it doesn't burst as the foam expands. Any spilled foam is not hard to remove before it sets

This may help make the boat stiffer too. Don't use hardware store expanding foam, not at all same thing.

You'll have to drill a few limber holes later to allow drainage, followed by some paint or gel coat

[Don C L]

Hmmm.. I have my doubts. I think the frames came loose because of the hull flexing as hulls are wont to do. I doubt these frames were intended to be integral to the hull and necessary for the hull integrity. I am happy to be proven wrong though.

If the encapsulated keel on the Dufour is anything like the Cal 28, that keel does move side to side and the hull does flex..

[Uncle Bob]

^^^^^^
This.
Trying to reinvent a design reasonably well proven without any idea of what you're doing is fraught with danger.

Repair the cut and damaged portions, clean with a pressure washer those sections that are hard to access, paint with a good paving paint and go sailing.

[Don C L]

I don't know how the weather is where you are now, but can you take her out sailing for the day. If so, leave the sole off and watch the keel and hull. I am guessing you'll see some movement. If so, no amount of glass there will stop those frames from detaching again IMO. Is your keel boated on to a stub, or is it encapsulated? I was assuming it was encapsulated. In any case I still bet you'll see some movement.

[neilpride]

It is structural although at first glance it may appear to be a support for cabin sole.

The best thing to do is to cover it all with FG and paint it with white gelcoat.

It's a pain in the ass but, you're going to put a material like plywood that rot over the years when you already have a frame?

[Chotu]

I agree with Neil pride. Putting plywood there is absolutely crazy. It’s wet enough and full of fuel that it destroyed fiberglass. Plywood is going to last one season.

I don’t know if the peeling fiberglass OP is talking about is on the main hull or is the tabbing that holds these frames in place.

If it’s the tabbing, just redo the tabbing.

[neilpride]

More pics, if you don't like Poly, then Epoxy and a 2 part barrier coat primer do the trick.

[Bobby Lex]

Random thoughts:

1. As has been mentioned a couple times above -- be sure to drill limber holes in each stringer for drainage to the bilge/sump.

2. Expedition Evans' youtube channel did a major grid repair job on a salvage boat they bought. The first dozen episodes or so show their painstaking process of grinding, repairing, and re-tabbing several damaged stringers in their grid. Although the Evans' can be annoying, their repair videos are reasonably useful in showing how to make these repairs.

Good luck with your project!

Bob

[wyb2]

How I read this:

The grid (whatever it’s original purpose) is fine, but the tabbing that bonds it to the hull is peeling away from the hull.

The enclosed boxes of the grid is preventing the cleaning of some amount of water/diesel/oil trapped inside. This may cause an issue if trying to simply tab them back to the hull.

I would consider cutting away 1 wall of the box structure (or sizable access holes in 1 wall) so you can clean properly inside. Then to rebuild, you can replace the blanks you cut out and glass over the whole thing, bonding the blank back in and bonding the grid back to the hull. Your cabin sole will end up a few layers of glass higher than before, but that might be more accurate than if you try to rebuild the whole thing from scratch.