Replacing Balsa Core on Cabin Top

[Bennett Schneider]

Here's a question regarding the repair of a soft cabin top on a Europa style trawler.
When removing the top skin, will I find "beams" between the top and bottoms skins like you would find in your house?

Thanks,

Ben

 

[Portuguese]

...don't think so...if it is basa core, it shouldn't

 

[Bennett Schneider]

I'm thinking that it's probably going to be those plywood squares that were so popular in boats made in the far east. Regardless, I'm expecting to open the top skin in as large a piece as I can and replacing it with balsa.

 

[FF]

>large a piece as I can and replacing it with balsa.<

With all that work you might consider a plastic core like Nadia Core that wont rot again.

 

[Bilgewater]

I replaced most of my fly bridge deck balsa core, but did it in sections as I couldn't remove the fly structure. I did not find any beams underneath. I did not compare the prices between balsa core and Nadia core, just replaced with 1/2 inch sheets as was the original.

 

[Portuguese]

Rotten wood underneath FG.
That's what happens when the resin is not epoxy. When will people realize that polyester or any other thing that is not epoxy will not impregnate wood therefore, will not bond with FG?

The application of inappropriate resins with FG/Wood is yhe only reason why people runs from wood core FG structures.

Bennett, if you are going to use wood as core again, do not use any other resin then Epoxy. Otherwise, follow FF’s recommendation

Good luck

 

[rjtrane]

I would suggest using closed cel PVC foam core - low density. It handles similar to balsa but bonds better. There are proprietary "pastes" to bond the foam to the remaining fiberglass under the core. Once cured, fill voids with the same slury paste then laminate the new surface layers of fiberglass. Divinicell - Klegecell - Airex - are brands I've used in the past. With modest camber, you will not need the scored sheets.

We use Nidacore in our superstructures - it is a plastic honey comb - very light and inexpensive. It is mostly air. It may work as well as the PVC foam cores. Since most of the cost is in labor. Either paid or "free", why not use the best material. Avoid balsa.

Making it look pretty may be the most challenging part? I'd personally look closely at finishing with a "rubber" non-skid or synthetic teak.

 

[FF]

>Rotten wood underneath FG.
That's what happens when the resin is not epoxy.<

Nope water entering the wood will cause rot , weather its wrapped in polly , epoxy or gold.

Epoxy bonds far better to wood , but a fitting letting water in will destroy the wood anyway.

 

[psneeld]

Here's a question regarding the repair of a soft cabin top on a Europa style trawler.
When removing the top skin, will I find "beams" between the top and bottoms skins like you would find in your house?

Thanks,

Ben

I think it depends...my beams are inside the cabin under the (skin)...but the (skin) was still 2 layers of glass with teak blocks in between so it really was more "deck" than skin.

But it is possible to have the beams between the skins though not as likely as showing the beams inside makes it look "nautical".

 

[jleonard]

I re-did the flybridge of my ex 1978 Mainship 1 several years ago. Huge flybridge similar (I think) to a Europa style. No beams in the core. Plywood "frame" around the edge and balsa core inside.
1st advise is to make sure you only rebuild what is truely wet. I used a 2 inch hole saw and took "core samples" by drilling thru the skin to make sure my moisture meter was telling the truth. It was close, but I'm glad I took that step.
Turns out that due to the crown, the center 1/3 (or 1/2) was fine.
After making saw cuts thru the skin only I removed them and scraped out the wet core material in small sections to not collapse the structure.
Then after consutling a local boatbuilder/fiberglass supply house (Legnos Boat, Inc) I used their suggested method to rebuild.
5/8 exterior plywood, secured the the inside of the lower skin with "bondo-lite" after being prepped (painted) with ployester resin thinned 25% with acetone for penetration into the plywood. Then 1 layer of 1 1/2 oz mat, a layer of roving, then the mat again until it was equal to the original surface. All knitted together of course.
Then we ground the surface to get the original crown back.
After that we rolled on vinlyester gelcoat tinted grey with non skid moxed in.
It came out great and there's no doubt it will last another 25 years.