[deltaten]

I need. to re-do my deck/s and cabin top. Having looked into repairingfrom under, cut'n'refit upper lam and simply replacing upper lamcut-out with new glass. Seemssto be the easiest/simplest wayTogo..

While look. at the lines o. the cabin top th. other evening,I wondered.....
Why NOT just glass over top?
Fair the edges. and the. non-skid, rough out the gel coat ann. add two lamms of seventeen-o-eight with mebbe a finish lam. of cloth?

With any "up top" repair, I,m gonna need to refinish most of it; probably with a grip paint, anyway, so why not just cover it. all w/glass. and paint it complete ? What would it matter to have nasty, ply mulch. captured in the old core? I would suppose that near .three eights/ half inch of glass would. be as strong. as old core lamm?

looking at options. pro or con

 

[tommays]

The core between the inner and outer skin functions like and I-BEAM which is why it is done

If you glop a bunch o stuff on top it will NOT be stiff JUST heavy and the boat will lose stability


Take a 6" x 24 " piece of even plywood which is the very worst core material and put a bad layer of glass on both sides and see how strong it becomes

 

[Barquito]

I agree with tommays. If you made it strong enough, it would be heavy. However, your solution also begs a question: Why make the repair at all? The deck is probably strong enough, even with mash potato core material.

 

[mbowser]

3/8" - 1/2" solid glass in addition to a waterlogged core would be HEAVVVY and not nearly as strong as doing it the correct way: pulling out the old core, bonding new core to bottom skin and glassing on a top skin. As Tommays said, the composite laminate with bottom skin, core, and top skin is functionally similar to an I-beam.

 

[CalebD]

deltaTen,
Having done side deck re-core projects on my boat I will comment.
The strength of any deck comes from the sandwich construction. If any layer (inner skin, core, outer skin) of the laminate fails then the whole construction is compromised.
Your cabin & decks are likely cored with end grain Balsa which has now turned largely turned to soil. The only way to really fix it is to repair the layer(s) that have failed.

doing any kind of re-core project is a lot of work and I hate having to do things right the second time so I refused to use any kind of wood for a core material. Instead I used this polypropylene honeycomb core material:
honeycomb at Express Composites, Inc.
which is very light weight and extremely easy to cut to shape. I have a few scraps left over from my projects and I'd be happy to mail you a sample for your consideration. Send me a PM with your address if you are interested in a sample.

As to repairing from above versus below I would recommend going at it from above unless you are very comfortable doing vacuum bag epoxy work. Working from above gravity is your friend; not so if working from below.

Several layers of bi-axial cloth (like 1708) should be enough to re-build the outer skin.

It is a big project and not worth doing half fast.

 

[Minnesail]

Why make the repair at all? The deck is probably strong enough, even with mash potato core material.

I have the same question. The foredeck on my 22-foot boat is quite squishy, but the rest is solid. So although it's a bit trampolinish, it holds my weight fine. Is having a 3' by 3' area delaminated really going to affect the integrity of the boat? I can see how a bigger area on a bigger boat could cause the boat to flex and twist more, but is it really doing that much on my little boat?

I'm wondering if re-coring should be on my list of projects, or if I should just live with it.

 

[tommays]

I for example re-cored the forward deck as the front was in fact going to fall off or the mooring bit was going to pull out of the deck

The rest of the boat was not perfect but good enough to pass a survey so it stays as is