Repair balsa core from inside boat

[Restoration man]

Hi I’ve got 1976 storebro 31 biscay twin diesel motor boat in the uk , im currently In the process of repairing the fore deck core from the inside ,only the front 1/2 of the fore deck around the winch and the cleats etc , this is originally made up of ply and balsa ,I’ve used Moisture meter to identify the wet part and I’ve got back to good balsa , I’ve left 2” Perimeter around so I’ve got something to glass to , I cleaned all the old balsa and plywood out of the perimeter, my question is can I fill this void with epoxy thickened with cabosil or similar because it will be very hard to try slide the new core ( was going to use armacell pet foam ) into this void and avoid any air pockets, part I’m repairing is quite rigid due to a chain locker bulkhead, hope you understand what I’m trying to do is this a good plan ???

 

[Scott Danforth]

I would trim the lip off, grind it back a bit for proper tabbing, and not have to try to stuff anything in there, just bond the new core. there are many on-line tutorials about re-coring sailboats that you can get some pointers

 

[Restoration man]

I would trim the lip off, grind it back a bit for proper tabbing, and not have to try to stuff anything in there, just bond the new core. there are many on-line tutorials about re-coring sailboats that you can get some pointers

I’m a bit reluctant to trim the lip back as there wouldn’t be enough to tie into when I put the inside skim back on, it would mean fiberglassing right back to the hull joint it’s just to tight up there to be trying to get the fiberglass to conform to the shape , it’s going to be hard to do it with the lip but without the lip near on impossible, on the photos it looks easy but trying to squeeze into the pointy end is very hard , hence why I spent so much time cleaning every last trace wood out of the lip

 

[Scott Danforth]

the break the core up. the core is to take up space between the two layers of fiberglass. to separate them and keep them from compressing together.

 

[kcassells]

I would fill the voids with PB, 1/4" cut glass and cabosil as my mix. Make the pb thick so whereas you can hold the mix upside down and it doesn't drop out of the container. Then its time to go to work. The cut glass is the strength. Pb is no strength except for as a glue.
I would also use ply that has been wetted out that was cut to fit to place. Key word is cut to fit then wetted out and dried. All edges have to be soaked prior and dried out. Then apply pb to adhere the wood. Also the wood could be prepped as pcs,. or as 1 pc. like a puzzle. If its pcs. then again, the voids need to be filled with pb as stated above.
Its a process thing. Ie fill, sand etc...
Glass it 2x and have a great day.

 

[Scott Danforth]

The down side is youwill be working upside down and fighting gravity.

That, in my opinion makes the job harder than redoing the top of the deck and the non-skid

I have a soft spot on my foredeck that is from a crack in the fiberglass that exposed the balsa to the elements for a short while While that was glassed over 5-6 years ago, the balsa appears to be soft now in one spot. After helping do the deck on a buds sailboat by spending 4 hours in the v-berth laying on my back and fighting glass matt falling on my head, i decided when I tackle my foredeck, im going thru the top

 

[Restoration man]

Thanks everyone for the advise, I’m definitely going to cut then prime with neat epoxy what would you expect it to take 2 coats or is it case of keep putting it on till it won’t take no more ? , also if I could stuff the foam and the wood into the lip poss by grinding the edges of the wood and foam down a bit and ramming it in with thickened epoxy (don’t know if I’m going to be able to do it till the foam comes ) would that be better than stuffing the edge with pb ? If i do go down the route of stuffing the edge with pb will it create a hard spot or is it not worth worrying about ?
Should the join between the wood and the foam, or any joins between foam and foam be butted up or should I leave something like a 1/8” gap and fill that with thickened epoxy?
One more question should I use pb ( epoxy with cabosil and chop strands )to stick the core to the inside of the deck or use just thickened epoxy with cabosil? I can prop the core into place easily enough
Sorry for all the questions
Thanks Nick

 

[kcassells]

Thanks everyone for the advise, I’m definitely going to cut then prime with neat epoxy what would you expect it to take 2 coats or is it case of keep putting it on till it won’t take no more ? , also if I could stuff the foam and the wood into the lip poss by grinding the edges of the wood and foam down a bit and ramming it in with thickened epoxy (don’t know if I’m going to be able to do it till the foam comes ) would that be better than stuffing the edge with pb ? If i do go down the route of stuffing the edge with pb will it create a hard spot or is it not worth worrying about ?
Should the join between the wood and the foam, or any joins between foam and foam be butted up or should I leave something like a 1/8” gap and fill that with thickened epoxy?
One more question should I use pb ( epoxy with cabosil and chop strands )to stick the core to the inside of the deck or use just thickened epoxy with cabosil? I can prop the core into place easily enough
Sorry for all the questions
Thanks Nick

Thanks everyone for the advise, I’m definitely going to cut then prime with neat epoxy what would you expect it to take 2 coats
**2 coats are fine nough. Just make sure edges get saturated
or is it case of keep putting it on till it won’t take no more ? , also if I could stuff the foam and the wood into the lip poss by grinding the edges of the wood and foam down a bit and ramming it in with thickened epoxy (don’t know if I’m going to be able to do it till the foam comes ) would that be better than stuffing the edge with pb ? If i do go down the route of stuffing the edge with pb will it create a hard spot or is it not worth worrying about ?
** Just fill with pb as discussed. Force it in. Poke it to let out air bubbles and go at it again. Foam will probably degrade quickly.
Should the join between the wood and the foam, or any joins between foam and foam be butted up or should I leave something like a 1/8” gap and fill that with thickened epoxy?
** No foam at all.
One more question should I use pb ( epoxy with cabosil and chop strands )to stick the core to the inside of the deck or use just thickened epoxy with cabosil? I can prop the core into place easily enough
** Always use chop strand to make pb. Cabosil is your thickener, chopped strand is your strength. When making the pb determine your resin amount then drop the chopped strand in and let it soak until it falls to the bottom, then add hardener, then add cabosil to thickness desired. I use a drill with a small paint paddle. The mix nearly doubles from original when finished so keep that in mind. Try small batches until you feel comfortable. You want to pull the paddle out, look at the mix and make sure the mix is stiff.
Like the swirls don't drop or hold the stuff upside down and doesn't drop.

Pics man pics!
Poly or poxy is a matter of choice.

 

[kcassells]

hey that's just my approach, anyone else can chime in.

 

[Restoration man]

hey that's just my approach, anyone else can chime in.

Thanks for the advise mate much appreciated
When I said foam i was referring to the divinycell pet foam I plan on using instead of using the end grain balsa , my fault for using the wrong terminology,
one more quick question I appreciate the need to put some chop strand into the mix to fill the voids round my perimeter, but is it still necessary to put the fibers into the mix when I glue the wood and the divinycell to the deck ? I am only using it as an adhesive
I kind of originally thought I would just mix just cabasil and epoxy to a thick mix and use notched Trowel so I could get an even layer on the inside of the deck ,then push my ply and divinycell into this prop and leave to dry trying to get quite close fit between deck and the divinycell , will it still Trowel with the fibers added ? Is this good idea or would you still stick with the fibers in the mix ? Sorry for all the questions , I really want to do this right fist time , here are few more photos
Nick

 

[Scott Danforth]

me, I would use a core bond unless you cant get it in time, then I would mix up PB a bit on the soupy side and probably roll it on with a 4" roller

 

[kcassells]

Pics are very valuable here. Thanks.
Never used this but Old Man Scott has been around....:]
Core-Bond B72 is the a lightweight polyester based Core-Bond, it is formulated to be catalyzed with standard MEKPs. Core-Bond B72 is suitable for both hand-layup and vacuum-bag core installation, and is used as a 2-part system in conjunction with a priming resin applied to the core surface.

• Lightweight and non-sagging
• Formulated to the degree of elasticity required for the core to skin interface
• Significantly reduces the possibility of print-through
• Combines with the priming resin for a thorough cure and good cohesion

Not supplied with catalyst.