What's involved in making new GRP cockpit locker lids?

[Babylon]

My cockpit locker lids (GRP of twin walled construction, i.e. with a foam or balsa core, with solid teak top surfaces) have begun to feel quite squishy when stood on, and I suspect they're pretty wet and rotten inside. Any recommendations for methods (or a GRP specialist Southampton area) to make good existing... or fabricate new ones?

 

[Akestor]

A quite fast repair i would do, would be to cut 4-5 stripes of the wall that is at the inner side without damaging the outer wall. Then remove the roten core and install 4-5 thick iroco ribs( at least 20mmx 40mm each and as length is needed for the width of the lid) as an airplane wing is made internally. The ribs screwd and epoxied on the inner side of the external wall should make the top wall very stiff and good to dance on it. Hope it makes sense!

 

[pvb]

As Akestor has suggested, it would be much easier to try reinforcing the existing lids than starting from scratch.

 

[maby]

My first reaction would be to try to fix the existing lids - that is likely to be a lot less effort than making new ones. There are plenty of articles on the web explaining how to fix delaminated GRP decks - and this is just a small example of that. Working from the inside (and, hence, invisible side), you drill and cut access panels through the inner skin, dig out the saturated balsa, replace it and glass over the access holes you cut. Personally, I would not be replacing the coring with anything other than epoxy and GRP - there should be no place for balsa on boats - it's a terminally stupid idea.

Fabricating replacements in GRP is not particularly difficult - provided you have a mould for the component - and that is usually the killer. Again, there will be instructions on the web and I guess you could make a mould based on the old locker lids using silicone, but that is a lot of work - trust me - I've done it on a far smaller scale.

 

[ShinyShoe]

If repair is not an option, are the lids identical or are they individual?

Identical? Moulding your own mould from the best is not impossible and the you can make as many lids as you want

 

[Wansworth]

Make new ones from solid wood?

 

[maby]

Make new ones from solid wood?

Hmmm, that requires serious mojo if you want it to look anything like the original!

 

[Wansworth]

Hmmm, that requires serious mojo if you want it to look anything like the original!

The nic 32 has wooden locker tops looks good

 

[Babylon]

Thanks for the feedback. I think the most sensible way to proceed is to remove them from the boat (I'm coming out for a month in early Spring) and get them home to the dry of my workshop. Then, as the GRP and teak tops are aged but otherwise intact, remove the bottom skins as Akestor suggests, dig out the soggy flabby stuff, and create an internal structure of hardwood ribs plus sides to be epoxied/screwed to the remaining GRP. With that done, there's little reason to re-skin the bottoms - if anything an open structure will prevent future moisture building up.

 

[maby]

Thanks for the feedback. I think the most sensible way to proceed is to remove them from the boat (I'm coming out for a month in early Spring) and get them home to the dry of my workshop. Then, as the GRP and teak tops are aged but otherwise intact, remove the bottom skins as Akestor suggests, dig out the soggy flabby stuff, and create an internal structure of hardwood ribs plus sides to be epoxied/screwed to the remaining GRP. With that done, there's little reason to re-skin the bottoms - if anything an open structure will prevent future moisture building up.

Worth a try, but you may be surprised at how thin the top later of GRP is. I'm not confident that the result will be stiff enough to take the weight that it must carry. Test it carefully once you have finished - if there is any doubt about its weight bearing, back fill with epoxy and replace the removed inner skin.

 

[Babylon]

I think from memory that the whole structure must be at least 1.5" maybe 2.0" thick as per foreshortened photo below showing surface teak running lengthwise, so a 'core-box' (i.e. internal ribs running widthwise or even a lattice within a perimeter frame bonded to the internal GRP sides, all of 20mm Iroko or oak) should be plenty strong enough.

 

[William_H]

I would suggest that you simply drill largish holes in the under side in the worst affected area through the core but short of the top layer and fill with epoxy possibly with finely chopped glass. Then seal over the top with glass. Just do a few holes then wait for cure. You can then decide how many holes you need to do to get the repair you want. The more holes filled with epoxy the stiffer the lid but a few may just reinforce sufficiently. ol'will

 

[coopec]

I would do what others have suggested and cut the old foam out and replace it using a flexible glue (like Sika 291 or similar) then a few layers of poly/glass.

But it would be easy to make up new ones. Here are my molds for two different sizes

 

[Stemar]

Thanks for the feedback. I think the most sensible way to proceed is to remove them from the boat (I'm coming out for a month in early Spring) and get them home to the dry of my workshop. Then, as the GRP and teak tops are aged but otherwise intact, remove the bottom skins as Akestor suggests, dig out the soggy flabby stuff, and create an internal structure of hardwood ribs plus sides to be epoxied/screwed to the remaining GRP. With that done, there's little reason to re-skin the bottoms - if anything an open structure will prevent future moisture building up.

This is how I'd go about it. If they aren't rigid enough open, I'd cover the bottom with a thin ply (BWP would be fine), covered with a layer or two of glass cloth & epoxy.

 

[Bajansailor]

If you cut out the bottom skin from the lid carefully, and dig out all the soggy stuff that is what remains of the core, you could perhaps replace it with a layer of foam as a new core. And then simply glue the bottom skin back on with epoxy. Should be massively strong.

 

[coopec]

If you cut out the bottom skin from the lid carefully, and dig out all the soggy stuff that is what remains of the core, you could perhaps replace it with a layer of foam as a new core. And then simply glue the bottom skin back on with epoxy. Should be massively strong.

And use a core like Divynicell or Airex (neither absorb water)

 

[Daydream believer]

It would be a doddle to make those in epoxy coated wood & as the top is teak anyway it would not look out of place.

 

[Refueler]

If you cut out the bottom skin from the lid carefully, and dig out all the soggy stuff that is what remains of the core, you could perhaps replace it with a layer of foam as a new core. And then simply glue the bottom skin back on with epoxy. Should be massively strong.

Now we are getting sensible ...

Simply dig out old filling material and then inject foaming PU or similar to create a solid but light new filling ...

Do this is small amounts in stages as the expansion can be tremendous and create a lot of pressure possibly deforming the structure. If you remove most of the underside GRP - that will allow you to fill and avoid pressure problems.

 

[Bajansailor]

The floor in our cockpit was cored with plywood, which was all rotten, and the floor was very spongy.
I cut out the top skin carefully in rectangular or trapezium shaped slabs, dug out all the manky wood, and then used what is called 'plastic board' here - 3/4" thick PVC foam with a thin plastic laminate on each side (popular for building kitchen cabinets with), as 'proper' foam sheets are ridiculously expensive.
I bedded the plastic board sections down on epoxy putty (I scuffed up the laminate first) and then just glued the original top 'lids' back down.
Ok, this is a cockpit floor which will take a lot of abuse, so I added a layer of fibreglass over the top, but this would not be necessary for small locker lids.

 

[Yellow Ballad]

Makes it look very easy, something I wish to try one day!