Getting a perfect surface with wood?

[Chotu]

Originally Posted by tomtriad

Mitiempo and GGray have good advice on this page. Cardboard templates and mockup, which you can fit closely to the hull, then proceed with lightweight materials, 1/4" ply, curtains or fiddles instead of doors on cabinets. A fellow sailor made a storage system for his tri with shelves fronted by a single sheet of ply with oval cutouts, and the cuddies separated by thin plywood baffles. No curtains, no solid fronts, no problem with ventilation or access. Whatever you make in the shop will have to be spiled and fitted to the hull carefully.

I did start this way, but I used even thinner plywood. It was a little too thin. I think something in between 8th inch and a quarter inch might be the way to go. At least on vertical surfaces. Then horizontal things like seats, quarter inch.

I had tried to do stick framing and 8th inch. That did not work well for seats.

Basically, this is just way too much trial and error. It’s destroying me mentally and financially. I need to do it the right way the first time. I’ve tried like 1000 things. I’ve done my windows six different times. All of them. Because they all fell off. This finish stuff is driving me crazy to be honest.

[LooseGoose]

Originally Posted by Chotu

Doing interior things, on the catamaran, may have to be done in wood in some areas.

If you are building say, a bookcase out of plywood, how do you get perfect surfaces for paint? And make it in such a way that the paint never peels off?

I’m trying to make things as water resistant as possible, with a perfectly smooth surface for a high gloss, and might have a little gaps here and there to fill. What would you fill the gaps with?

Basically, how can you take wood and make complicated boxes and structures with doors, yet have it come out looking like perfect modern cabinetry? And have it being somewhat water resistant like modern cabinetry is? There will be lots of changes of temperature and humidity.

Have you looked into thin Coosa board?

[Chotu]

Originally Posted by LooseGoose

Have you looked into thin Coosa board?

That stuff is extremely heavy and doesn’t have a good surface. Not a good item to build cabinetry and interior of a boat out of. Especially a high-performance Catamaran. This has to be light weight.

There are still a lot of mistakes that could be made with this boat. The entire boat with carefully engineered and built to be extremely lightweight. It is a fast boat. I don’t want to ruin it.

[slug]

Originally Posted by Chotu

I did start this way, but I used even thinner plywood. It was a little too thin. I think something in between 8th inch and a quarter inch might be the way to go. At least on vertical surfaces. Then horizontal things like seats, quarter inch.

I had tried to do stick framing and 8th inch. That did not work well for seats.

Basically, this is just way too much trial and error. It’s destroying me mentally and financially. I need to do it the right way the first time. I’ve tried like 1000 things. I’ve done my windows six different times. All of them. Because they all fell off. This finish stuff is driving me crazy to be honest.

Boatbuilders use foam core plywood

Compared to marine ply it superior and more versatile
Lightweight Structural Marine Honeycomb Sandwich Plywood for Boat Builders - Non-warping patented wooden pivot door, sliding door, and Eco-friendly metal cores
Many suppliers
Google them

[jimbunyard]

Originally Posted by Chotu

That stuff is extremely heavy and doesn’t have a good surface. Not a good item to build cabinetry and interior of a boat out of. Especially a high-performance Catamaran. This has to be light weight.

There are still a lot of mistakes that could be made with this boat. The entire boat with carefully engineered and built to be extremely lightweight. It is a fast boat. I don’t want to ruin it.

Umm... coosa is about half the density of pine plywood; the surface could easily be filled with a mixture of glass bubbles and polyester resin. Other advantages are that it is equally rigid in both axis (unlike 1/4" plywood) and all surfaces don't have to be sealed before use. A primary disadvantage is that it doesn't hold screws, but you're already aware of that.

This is not a suggestion or advice for what to use, just a statement of facts.

[Chotu]

Originally Posted by jimbunyard

Umm... coosa is about half the density of pine plywood; the surface could easily be filled with a mixture of glass bubbles and polyester resin. Other advantages are that it is equally rigid in both axis (unlike 1/4" plywood) and all surfaces don't have to be sealed before use. A primary disadvantage is that it doesn't hold screws, but you're already aware of that.

This is not a suggestion or advice for what to use, just a statement of facts.

I’m confused. I know of this as a heavy substance. It’s lightest variety 20 pounds per cubic foot. So, a 4 x 8 sheet of 1/2” Coosa is 2.6666 cubic feet of material.

Bluewater Panels

That’s 53.3lbs for a standard 4x8 sheet in 1/2”.

https://www.boulterplywood.com/MarinePlywood_4.htm

A 4 x 8 sheet of marine plywood in half inch is 37 pounds.

Coosa is really heavy stuff. I don’t know where you’re getting that from.

[rslifkin]

I'm coming up with 1.333 cubic feet for a 4' x 8' x 1/2" sheet, so 26.66 lbs for the bluewater 20 variant. The less strong Coosa "nautical" line comes in a 15 lb / cubic foot variant, so just about 20 lbs for a sheet. Compared to most foam cores or balsa, the stuff is heavy, but not compared to plywood.

[Chotu]

Originally Posted by rslifkin

I'm coming up with 1.333 cubic feet for a 4' x 8' x 1/2" sheet, so 26.66 lbs for the bluewater 20 variant. The less strong Coosa "nautical" line comes in a 15 lb / cubic foot variant, so just about 20 lbs for a sheet. Compared to most foam cores or balsa, the stuff is heavy, but not compared to plywood.

I’m doing too many things at once. Sorry. Texting like 50 people at the same time. You’re right. I blew the math. I calculated as a 1 inch panel not a half inch.

Now that 15 pound version does sound very interesting.

How brutal is the pricing on this stuff? And isn’t it kind of like stone? Porous?

[Matt Johnson]

https://www.merrittsupply.com/produc...mposite-board/

It isn't cheap, but Merritt does pretty good pricing if you need to buy more than one or two.

-Matt

[Chotu]

Originally Posted by funjohnson

https://www.merrittsupply.com/produc...mposite-board/

It isn't cheap, but Merritt does pretty good pricing if you need to buy more than one or two.

-Matt

I would say I need more than one or two. It’s a completely empty hull on a 50 foot catamaran. LOL. Everything needs to be built. That’s like 50 sheets min.

[Matt Johnson]

1x1" stick built frames covered with 1/4" plywood is going to be the cheapest, lightest and easiest to build. You'll need 3/8" for just about ever top surface (counter top, settee top, bed base), but the sides of cabinets and furniture works well in 1/4".

If you want Formica, vertical surface grade is the lowest weight .

One variation we used on our first boat was to make 1/2" plywood ring frames, cut out the center leaving just 3" all around, and then use these as the perpendicular frames for the settees. The face was 1/4" plywood and top was 3/8". But they did require fiberglass tabbing since you don't have a screw holding surface on the edge of the plywood.


Matt

[Matt Johnson]

Originally Posted by Chotu

I would say I need more than one or two. It’s a completely empty hull on a 50 foot catamaran. LOL. Everything needs to be built. That’s like 50 sheets min.

I just had them quote for 200 sheets of Divinycell and it's well under half the single sheet price listed on their site. Coosa maybe similar.

Matt

[Chotu]

Originally Posted by funjohnson

1x1" stick built frames covered with 1/4" plywood is going to be the cheapest, lightest and easiest to build. You'll need 3/8" for just about ever top surface (counter top, settee top, bed base), but the sides of cabinets and furniture works well in 1/4".

If you want Formica, vertical surface grade is the lowest weight .

One variation we used on our first boat was to make 1/2" plywood ring frames, cut out the center leaving just 3" all around, and then use these as the perpendicular frames for the settees. The face was 1/4" plywood and top was 3/8". But they did require fiberglass tabbing since you don't have a screw holding surface on the edge of the plywood.


Matt

Thank you, Matt. I think this might be the way I should go. It’s unfortunate I already bought a bunch of other materials.

If I use wood like this, what is the absolute best way to get a smooth and perfect high gloss finish? One that can stand up to a little splash of water here and there and also high humidity and heat?

I definitely want the look of Formica, but to add that to wood makes it very heavy at that point I think. Right? Even adding formica to foam made it fairly heavy. The foam panel approaches the weight of plywood at that point.

What about adding for Micah to just one face? Would that be about a similar weight to painting?

If not using Formica, How do you handle the edges where different faces come together? A nice, sharp, square edge is needed for aesthetics.

Inside cabinets and inside a settee, I could seal the wood with polyester resin. That should keep the majority of moisture out of it correct? Similar to the ceiling with epoxy but not quite as great. Not for submerged in the water type stuff. Not for outdoor use.

[GRIT]

I'm no expert in wood. But on our first boat we used maple faced plywood, primed, sanded and painted with water based paint, for the inside panels. The outer panels, and doors, we had made at a cabinet shop, where they stained and varnished solid wood, also maple. That boat is still sailing with those cabinets, and I installed those in 1996.

We made the interior of our Corbin 39 in Black walnut, for the forward areas, and mahogany in the pilot house. Both those woods were just varnished.

I've never had any issues with anything built of wood, in our boats. Unless it's in the bilge, just seal with varnish or primer. Neither of our previous boats were finished with "marine" or even outdoor plywood. The last photos of our old Corbin interior I saw were from 2017, and the interior wood looked no worse for wear, and it had been sitting closed for a few years in Newfoundland. We built that interior in 2002/2003.

I agree with using thin plywood, and enforcing it with bulkheads, or ring frames. But I think you're overthinking the sealing bit. I think any plywood, properly supported, and painted, will suit you just fine. Be sure to attach the ends of the ply to a support, or ring frame, and you should never have any issues with twist or warping.

Around these parts, east coast Canada, practically nobody uses marine ply, it's just too pricey.

Cheers, and good luck.
Paul.

[Matt Johnson]

Vertical grade Wilsonart is .186 lbs sqft. Not really the end of the world to use it, but would add up to 300 lbs if you needed 50 sheets.

You edge a countertop with a laminate router/trimmer. This is the exact same process.

For the interior, take a look at your Gulfstar- I'm sure the interior plywood was just sealed with varnish and is holding up fine over all these years. That's just how most boats are built. But if you don't want a varnished interior for the cabinets, then paint with enamel and call it good. It doesn't all need to be epoxy sealed to last.

I'm not sure how detailed your interior plans are, but your estimate seems pretty spot on to me. Take a look at the renders for the Schionning Arrow 1360 and see if that's the amount of cabinets and furniture you'd like to build. Those plans call for 49 sheets for what you see with interior version 2.

-Matt