Westerly Deck Cracks

[alla_breve]

Hello all,
I’ve sanded the many layers of deck paint off my westerly griffon for repainting and have found a few cracks mostly port side. They seem odd in that they are all straight lines. There is no movement or sponginess in the deck around them, they don’t appear to be deep . I think it’s balsa core in this area. I will grind one out for investigation but wondered if anybody has seen similar before? If it’s just gelcoat cracks I wonder why they’re so straight, rather than spidery? Two of them meet at 90 degrees!
Thoughts on repair appreciated, I’m thinking grind out down to the glass, refill with thickened epoxy, maybe with 1/2” tape as well?
(Sorry about the small photos , I had to reduce the file size to get them to upload)
Thanks for any advice

 

[LittleSister]

Spidery cracks are where the gelcoat, which is relatively rigid, has cracked when the GRP panel has flexed slightly. (usually where it meets a more rigid area of GRP) I imagine that straight cracks could be be when there has been a serious deflection of the GRP, and raises the question of whether the GRP panel itself has cracked.

It's hard to make out the overall pattern of straight cracks from the photos, and hence to make a guess as to whether some sort of impact has caused the cracks .

The real question, it seems to me, is whether there is actually any significant problem, or potential problem (e.g. water getting into the balsa core), arising from the cracks and requiring treatment. If you are unaware of any such problem, I'd be tempted to just treat the cosmetic issue, the easiest solution for which is repaint the decks.

 

[Concerto]

Looking at the rectangular cracks, they look like the size of the balsa panels used. This suggests the deck is flexing along the balsa core joins, possibly early delamination. Try doing a hammer test and compare with a section without cracks. There should be a different sound. If there is some delamination, I would drill a few small holes along a crack and try injecting some epoxy in as this will fill any delamination void. You may need to do this on a number of these crack lines. Also I would grind along each crack and then fill with Teroson gel coat filler, then sand smooth. You will now be ready to start repainting the decks.

 

[penfold]

Weird, they almost look like scribed lines rather than cracks; do you have any zoomed out pics or pics from further away to give more of a feel for where the cracks are relative to the gunwhale/coachroof side/etc?

 

[alla_breve]

Weird, they almost look like scribed lines rather than cracks; do you have any zoomed out pics or pics from further away to give more of a feel for where the cracks are relative to the gunwhale/coachroof side/etc?

Sorry, zoomed out pics too big to upload, did try earlier. They don’t reach coach roof or gunwale, most at about 45 degrees, longest about 10” long.