Seat Base Material - Plywood Alternatives??

Hey guys,

So in typical fashion, a small boat project turned into a potentially major boat project. I bought an 89 Sunsport (Okie Boarder's old boat) in January. After almost 40hrs (a lot of it hard riding) this season, I thought it might be a good idea to tighten all of the tower bolts, including the feet. So I started at the rear left, remove the vinyl panel, find there is a hole cut in the deck (probably for wiring, ballast, or maybe tower install while Okie put the tower on). Perfect!, wrench goes right in and I give the nut on the bottom side of the tower foot about a turn and a half, enough to make me think I should give them all a snug while the tools are out....

So go the front port side. Can't reach the nut, no matter how I try to contort myself into the little storage compartment behind/under the passenger seat. Figure the bow seat base on that side must have to come out, and maybe I'll get lucky and there's an access hole. Go to work on the seat base. 7/16 nut on the side and two screws into the back, except for my stereo amp is on that back wall and the screws used were long enough that they go into the bow seat base, so the amp has to come out.... 3 of 4 screws into the amp removal I find there is a stripped phillips head, on the hardest one to reach. Cordless recip saw, back up and running. Seat base comes out, find there is in fact NOT an access hole, so I cut one in with my jigsaw and tighten the tower foot. Good thing, this one took about 1 3/4 turns.

So here's where the trouble starts......

When I got the first bow seat base out I saw the wood is kinda rotten and moldy. A bunch of little bugs crawling around and I freaked out immediately thinking "TERMITES". Seat base goes to the driveway, wood gets a healthy dose of insect killer as does the bow base under the seats. This first seat is probably structurally ok, I figure at the time I'll kill any bugs, then soak it down with a bleach solution to kill any mold/mildew, clean it up and put it back in....

But my mind has me wondering, if that one is that bad, how do the others look.

Next I go for the nose seat base. PITA to remove cause one of the threaded studs attached to the seat base had come loose and was turning with the nut. Had to remove bow speaker for 2 hand access to hold it with pliers.
This seat base is trashed, completely rotted. I don't even want to put it back in like it is.

Finally, remove the starboard side rear seat base in the bow. This one is in ok shape. It looks like it had some patchwork done to the plywood when the previous, previous owner had the interior vinyl done in what Okie tells me was 2009.

So I'm considering building new seat bases and putting the existing foam and skins on (skins are in great shape, not sure about foam, it seems structurally good but won't know if it's totally rotten till I get them apart).
Anyone have any ideas for alternative materials to plywood? I'm willing to spend a little extra money but not a stupid amount. Any ideas???

Also, if I decide to go the wood route again, what is the best material to use, and how would you seal it up to make sure I can prevent mildew/mold/rot for as long as possible? Any tricks to removing/reinstalling seat skins and foam? Anyone know where to get stainless staples for putting the skins back on?

Attachment 15936Attachment 15937Attachment 15935Attachment 15938

Want to get this going ASAP so can get back to riding.

I've attached some pics for reference. Thanks for the help.

Attachment 15939I found this, what do you guys think?

Would 3/8 (.375) be enough? It looks like the original seat bases were .375 plywood, and when the vinyl guy did his scabbing he used 1/2.

Nothing structural in the bases, just needs to hold the skins on right?

A 24" x 48" sheet is $62 from Grainger, which I can have shipped to store (for free I think) and just pick up. My only concern is will this stuff take a staple?
I had some scrap TREX laying around my garage which I shot with my staple gun and a 5/16" staple just to see and that went right in....

Some of the later moulded style seats have a similar PU blow moulded material, so i would certainly agree that HDPE or HDPU would be a perfect material to build a seat base from.
In fact i couldnt think of anything better for longevity or structural strength. Ok there are other materials that are better suited but they are not readily available for general DIY use.

Oh and use stainless steel staples :)

Go for it :D

This is exaclty the material I used each time i get a mad wood piece on my boat.
I already rebuilt the rear hatch bench (0.5" thickness, black) and the shaft hatch (0.75" thickness, white) with HDPE :

Attachment 8570

Attachment 9962

I think 3/8 is not enough, it can warp or even break.

All the new boats are made with that stuff for bench.

Agreed...3/8 is not enough.

1/2 would be minimum 3/4 would be better.

I just redid mine with Starboard. I think it's basically HDPE. Not cheap but should last forever and took the staples just fine.

You really don't think 3/8 would do it for the seat backs? I kept saying seat bases, but what I really meant are the backs that attach to the deck. It's probably not that much to upsize to 1/2, and 1/2 might take the screws a little better where the edges line up.

Any thoughts on the foam? It is glued to the wood or will it come off. If it is glued, would I be able to saw it off with piano string or guitar wire and be ok or will I lose some thickness?

Any thoughts on where to get seat foam if I need it.

I'm 100% confident I can tackle this, just a matter of sourcing materials in short order. Wife kids are out of town this weekend and all next week till Friday, so I need to move quick and knock this out!!!

I plan to ride some this week, will just have to go without the seat backs in the front. Only issue is I'll have to re-mount my amp to the wall which will be some wasted effort, but shouldn't be too bad now that I know how everything goes together/comes apart. That was about 1/2 the time spent last night was finding all the bolts/screws. Lots of custom work done on this boat by the previous owner.

Thanks for the input guys, let me know on the foam....
-dy

Any idea where to source stainless staples?

Thanks,
-dy

Veada.com is a good source for foam and staples.

Menards and HomeDepot both carry T-50 stainless staples. I bought a pneumatic gun for $25 that can shoot those.

http://www.homedepot.com/p/Arrow-Fas...6SS1/100553013

You should look for an upholstery wholesaler in your area. They'll have the foam (if you need it) and any other supplies. They can probably also help with questions.

No way to know if/how your foam is attached) and what shape it might be in until you start pulling it off. My foam was all re-usable on my most recent upholstery project.

you could use 3/8 and double it up around the edges... In general under about 1/2 inch HDPE is pretty bendy.

Blows me away how much those seat bases have rotted the last several years. If you ended up going with wood, coat the wood in CPES. I like your idea of non-wood material, though.

Ordered 1/2 HDPE to re-do the seat bases. Should have it picked up from Grainger on Monday and tear into this project on Tuesday, if I don't go ride on my buddies Tige ASR that is..... : )

This is a spendy repair, about $235 for just the sheets alone, then still need some TREX for structural pieces (might just double up some of the sheets around edges if I have enough) and staples. And that's assuming the foam is still all good and not glued down so hard I tear it all up getting it off the old seat backs. I'll post some pics of the rebuild.

In the meantime, riding without the seat backs in the front. Gotta get to bed, 7AM on the lake tomorrow.

Haha...spendy :D

I just shelled out $4000 on a re-trim :O

I found a website in France where they sell scrap HDPE and every kind of plastic sheet.
Maybe you can find and equivalent company in the USA ?

Here is the link : http://chutes-plastiques.com/plastiq...laques/29-pehd

Dimensions are in "largeur" and "longueur" columns, they are in millimeters.
Thickness is in column "Epaisseur", it's still millimeters.

I plan to ride some this week, will just have to go without the seat backs in the front. Only issue is I'll have to re-mount my amp to the wall which will be some wasted effort, but shouldn't be too bad now that I know how everything goes together/comes apart. That was about 1/2 the time spent last night was finding all the bolts/screws. Lots of custom work done on this boat by the previous owner.

I work part time for a company called Cover Girl . She does vinyl and canvas boat repairs. I do all the rotted wood repairs so she can cover them. I have found that by the time I get a rotted wood issue the boat is 20 plus years old . The wood they use is nothing special sometimes I think they cut up the old parts crates to make interior parts. That being said I recommend a marine grade plywood or MDO grade plywood with a healthy coat of CPES from Rot Doctor . If the old untreated wood lasted 20 plus years the new treated wood will last 30 plus years. I think that will outlast the vinyl if not the whole boat. A good location foe materials is https://keystonbros.com
I have done many of the newer boats with PVC or other plastic seat bases wile they don't rot they do crack and are difficult to join and seam.