Filling the void in cabin roof

Hi I have a delamination problem on the roof of the forward cabin on my 34 MT DC the wood unnder the glass seems ok and I was thinking of filling the void with either the floation stuff you mix and pour in or Great Stuff any thoughts**** Thanks Dom

Hiya,
** If the fibre glass layer has separated from the plywood substrate you've probably got water in there and a "band-aid" fix won't help for long.* The best thing to do IMHO is strip off the old FG , let dry and re-coat with either an epoxy system or the original polyester.* It's not really that hard to remove your forward light (hatch) either which may be necessary to do the best job.

Dominic,

I bought my Marine Trader 34DC with the same sought of problem. The surveyor called this out as a serious problem. He said he had seen it on many trawlers. I am having the problem corrected now by having the deck opened up, the core material removed and new plywood inserted with new fiberglass put over it. The guy who is doing it has been building fiberglass boats for many years and recognized the cause of the delamination problem right away. It turns out most of the taiwanese trawlers are made of mahagony plywood with polyester resin used for bonding and glassing. magogany is a good marine material in most cases. A core material for fiberglass decking is not one of them. The two materials, resin and mahogany, do not bond well with each other. The same oils that protect the wood from moisture weakens the resin bond. Furthermore, the taiwanese builders constructed their upper deck core from left over plywood sections glued together with polyester resin and sandwiched between two layers of fiberglass a few layers thick. That would have been ok if they weren't walked on a lot by mostly heavy Americans. I guess the builders thought the upper decks would not be used that much. Considering how long the decks have lasted, I guess they were right. Over time the resin gluing the small sections of mahogany plywood together butt end to butt end separated from the plywood resulting in flexing as people walked on it. That in turn resulted in cracking of the thin layer of fiberglass and infiltration of water. Mahagony is pretty water tolerant so these decks have lasted pretty long. Yours and mine have reached the end of their life as will most of the trawlers out eventually needing to be replaced. There is no easy fix because of the mahogany material used in the core. Those pieced together small pieces of mahogany scrap wood need to be removed where people walk a lot. In areas with little of no walking traffic, the decks are pretty good and your technique of filling the voids may help. I found the front of my flying bridge was still solid whereas the rear area was pretty soft. The aft cabin roof deck was pretty soft too, no doubt the after effect of people coming down the ladder and landing on that deck. Those are the two decks I am replacing now. I am not replacing the forward cabin deck because it doesn't get walked on very much.

I hope this helps explain what is happening in your decks.

Bob

Welcome aboard Bob!
Good info you are providing.

has anybody tried addressing this problem from inside, meaning the ceiling of the cabin without cutting the flybridge floor? Seem I would be eaiser

"The two materials, resin and mahogany, do not bond well with each other."

Polly resin does not bond to much of Anything except it self , if used properly and applied on partially cured polly resin.

EPOXY in the building stage would have been the proper choice , but it costs more.

Good info folks. I have a 36' Universal, and my upper deck is visually OK, but the aft/port corner is springy, and water seeps inside along the wall, down along the overhead, and into the aft cabin where it drips right onto the bed (of course).

My plan is to take up the teak, working from aft fwd to the benches - about half way. Then I'll use a precision rotaray saw to remove the glass. I expect the entire core to be rotten, so once that is removed I've been told to lay down some sheets of insulation, then plywood, then epoxy the snot out of everything before I re-glass. The fiberglass will most likely be done by a professional. Then I'm going to simply apply some rubberized non-skid.

The trouble is keeping the upper deck dry, as I'm in Ketchikan. I think I might shrink wrap the whole

I'll take any advice anyone might have.

If you peel off the top layer of fiberglass and then remove the old plywood core then there is not much left except the bottom layer of glass? How do you walk or work on top of that to lay down the new plywood core? Wouldn't this distort and give way under your weight?

*


-- Edited by Tony B on Wednesday 10th of August 2011 08:52:09 PM

motion30 wrote:
has anybody tried addressing this problem from inside, meaning the ceiling of the cabin without cutting the flybridge floor? Seem I would be eaiser

Click to expand...

*I rebuilt the gunnel walks on my ex old Mainship 34 from underneath. It was not too bad of a job, just very messy. But the only reason I went from below was because the side decks were so narrow I thought I'd have a hard time grinding it evenly, getting the proper blend radius, etc.* I rebuilt much of the flybridge on that boat from above and it was much easier to deal with that way. It was also much better from a strength perspective in that adding layers was easy.

I rebuilt the Portuguese bridge the starboard side of the stern roof from the inside or under, and used the same piece of fiber glass to cover the new plywood.* To make the new ¾ plywood bend/conform to the curve of the bridge, I ripped groves in the plywood so it flex bent, epoxy the ply to the old out side fiberglass, then filled the rip grove with epoxy to give the ply back its strength, built back/epoxy new 2X 3 support studs.* If I had to repair/replace the front and stern deck I would probable try doing it from the inside first as the inside ceiling is ¼ ply.* Under the windows I did from the out side as moving the fix counter/cabinets would have been harder. ***
*
It can be done from the inside or outside so evaluate which is easier.

"Hi I have a delamination problem on the roof of the forward cabin on my 34 MT DC the wood unnder the glass seems ok and I was thinking of filling the void with either the floation stuff you mix and pour in or Great Stuff any thoughts"

If it's localized voids and not rotted out water filled sections you can drill holes in the voids and pump epoxy into them. Use a caulking gun and epoxy filled blank caulking cartridges. If necessary pile some masonry blocks on the section to hold in place while the epoxy sets up.

I know it seems crude but it is a Marine Trader.....

I just laid in a 3 foot x 7 foot section of marine ply in my roofs soft spot. My roof was the same small blocks of (but mine were teak) of wood all resined together.

Building from underneath would be a nightmare as the cross beams are only about 18 inches apart so rebuilding in sections wouldn't be a problem unless you had to do the whole thing...like putting any roof on.

If I had to do the whole thing...I would take the flybridge coaming off and get rid of the whole pilothouse as the interior teak is shot anyway.

We have currently removed our Saloon roof and bulkheads as when we started chasing the soft spots it was looking like there wasn't going to be much left anyway.