Pedestal seat material, OkumePlywood or Lumber ?

[TJM]

Hello:

My factory 20 yr old seats are rotting out. All of the cushions were re-done about 5 yrs ago and look great. I want to keep these and fabricate new bases for the seats.

My Question is, Do I need to use Marine grade Plywood? I am not a great fan of the Okume coloring and grain structure. Can I use Mahogany Plywood as long as it is all covered with Spar varnish?? The Mahogany at our Lumber yard is not Marine rated to the BS1088 spec. It is just rated to the A-1/VC. ( Veneer Core )

My Regal has a lot of teak wood trim accents inside and out. The Mahogany would match much better than the Okume. Teak is out of the question at $ 30 per Board Foot.

I would be repairing seating for 10 people so money is an issue.

 

[pdecat]

The difference between marine and other ply is no interior voids. In most modern plys the glue is all water proof exterior grade glue. Those voids are a problem however because of swelling due to water absorption. If you seal the ply on all sides including any fastener holes with several coats of resin any ply should last for a long time.

 

[yzer]

I'd recommend BS 1088 compliant marine plywood or Lloyd's of London certified BS 1088. Good marine ply is worth the investment.

My boat is mostly Philippine mahogany and white oak but there is a significant amount of marine plywood in the construction, including the vinyl covered helmsman and companion pedestal seats. None of this ply has failed to date. Good names today are Joubert, Hydrotek or Aquatek.

If appearance under varnish is a consideration for you then go with Okume or Meranti. If the ply is completely covered with vinyl, the heavier meranti is an excellent choice. I see no need to use epoxy sealer on marine plywood (or any wood) used above the water line. A couple of coats of Pettit Clear Sealer 2018 is all that is needed. If painting, mix a little of the paint into the clear sealer to help cover, then follow with two coats of marine enamel. If you want to stain and/or varnish, stain first then use a couple of coats of the Pettit sealer followed by varnish.

When restoring my original Chris-Craft plywood and vinyl covered seats I sealed the ply with Pettit clear sealer mixed with paint followed by two coats of the oil based alkyd enamel paint. All of the the plywood was covered with marine vinyl upholstery in this restoration so a good polyurethane exterior marine enamel was not required.

 

[jtybt15]

I wouldn't bother with marine grade for seat backs and bottoms. fill any voids that show up after cutting. Paint/seal any exterior surfaces(especially where condensation is a problem) and end grains but leave the interior/covered surface 'raw'. Drill a few 3/4" holes to help 'breathe'.