The front section of the flooring of my 16' Achilles inflatable rotted out finally. The boat is 36 years old. In looking at the construction of the original piece, it appears to have been 10mm (0.40") 4 or 5 ply plywood, trapezoidal shape (~3' on the long edge by 2' tall), encased in fiberglass, and permanently inserted into an aluminum channel on the 3' side, to mate with the next flooring section back. Interestingly, where the piece fit into the channel, it was only glassed on one side, so on the other side, there was about 5/8 of bare wood exposed against the channel face. Perhaps that's how it came to rot so badly. The boat sits covered on a trailer, and this piece does not see extensive or prolonged exposure to water, either in use or storage.
The aluminum channel slot is about 1/2" across, maybe .010 or .020 less. I need to take a more careful measurement..
I don't know much about plywood, and am having trouble finding pieces locally that seem suitable, and buying online is pretty expensive. There are two issues I need advice on - thickness and grade.
I can find exterior grade 4 or 5 ply pine in ~7/16" actual thickness (forgot to take my caliper) at Home Depot, but it appears to have some voids, though the faces don't look awful. There is also 3 ply 1/4" nominal exterior pine that looks like it might be a little better grade. Two of those appear to be about 7/16 actual.
They also carry 3 ply 5mm underlayment which looks much better quality - little to no voids and pretty flawless faces - but it's only Exposure 1, from what I can tell. 10mm would be a better starting point than 7/16".
Is fully skinned Exposure 1 adequate? Is exterior grade? Do I need full-on marine grade?
Is it feasible to glue two thinner pieces together? I've got a lot of dive weights and a few vice-grip style clamps, and other boards I can use to apply pressure, but that's about it as far as clamping.
If the final board looks like it will be a little thick after skinning - for sure the 7/16 stuff will be - can I router or belt-sand taper it slightly before skinning, where it will fit into the channel? I still have the skins from the original board, so I can measure how thick the skinning was.
I've looked at 3/8 nominal stuff at Home Depot, but it's probably .050 or more thinner than the original wood, and I'd have to find better quality stuff than what they have. Since I'll be skinning both sides where it goes in the channel, maybe it is a better starting thickness after all. I suppose I could just skin it thicker as well. There's supposed to be a hardwood plywood place up in San Francisco, but before I go driving all over to find a decent lumber yard, I thought I'd try to learn some more. If I had $100+ to drop on this, I think 1/2" Starboard would do a decent job too...
The aluminum channel slot is about 1/2" across, maybe .010 or .020 less. I need to take a more careful measurement..
I don't know much about plywood, and am having trouble finding pieces locally that seem suitable, and buying online is pretty expensive. There are two issues I need advice on - thickness and grade.
I can find exterior grade 4 or 5 ply pine in ~7/16" actual thickness (forgot to take my caliper) at Home Depot, but it appears to have some voids, though the faces don't look awful. There is also 3 ply 1/4" nominal exterior pine that looks like it might be a little better grade. Two of those appear to be about 7/16 actual.
They also carry 3 ply 5mm underlayment which looks much better quality - little to no voids and pretty flawless faces - but it's only Exposure 1, from what I can tell. 10mm would be a better starting point than 7/16".
Is fully skinned Exposure 1 adequate? Is exterior grade? Do I need full-on marine grade?
Is it feasible to glue two thinner pieces together? I've got a lot of dive weights and a few vice-grip style clamps, and other boards I can use to apply pressure, but that's about it as far as clamping.
If the final board looks like it will be a little thick after skinning - for sure the 7/16 stuff will be - can I router or belt-sand taper it slightly before skinning, where it will fit into the channel? I still have the skins from the original board, so I can measure how thick the skinning was.
I've looked at 3/8 nominal stuff at Home Depot, but it's probably .050 or more thinner than the original wood, and I'd have to find better quality stuff than what they have. Since I'll be skinning both sides where it goes in the channel, maybe it is a better starting thickness after all. I suppose I could just skin it thicker as well. There's supposed to be a hardwood plywood place up in San Francisco, but before I go driving all over to find a decent lumber yard, I thought I'd try to learn some more. If I had $100+ to drop on this, I think 1/2" Starboard would do a decent job too...
