Thoughts on building walls on a boat?

[milwaukeephil]

Hi Guys,
I'm totally out of my element and thought I'd come to this area of GJ and see if anybody has some ideas.

A buddy is rebuilding a double-decker pontoon boat in my shop and we're currently rebuilding the bathroom. The aluminum extrusion frame pieces that hold it all together have exactly a 1" inner slot for wall material.

It came from the factory 40 years ago as 1/2" foam sandwiched between 1/4" MDF sheets and covered in thin vinyl to make 1" panels.

We rebuilt the walls with 1/2" foam but used 1/4" HDPE panels instead. BIG MISTAKE. Within a day the walls started bubbling. We left it in the sun for one afternoon and the bubbles got way worse than this pic:

So, my question to you guys, is if you had to build a marine wall panel 1" thick and lightweight, what material(s) would you use?

Now is the time to figure this out since the frame hasn't been riveted together yet.

Thanks!

 

[kd3pc]

King star board will do nicely, fairly easy to work with and been around long enough to see how it performs

 

[quickfarms]

Starboard is pretty heavy for walls

Some campers use a composite panel that is fiberglass on the outside wth a foam core

 

[milwaukeephil]

King star board will do nicely, fairly easy to work with and been around long enough to see how it performs

Interesting. I'll have to call them and see if the 1/4" product will be safe from bubbling.

 

[PCustoms]

Pretty sure starboard is just HDPE.

Is this structural or just a divider?

I'd be looking to use some FRP panels. Waterproof and if you use the correct glue bonds to the foam.

 

[milwaukeephil]

Pretty sure starboard is just HDPE.

Is this structural or just a divider?

I'd be looking to use some FRP panels. Waterproof and if you use the correct glue bonds to the foam.

It's structural but not weight bearing. It holds the aluminum frame together and the second floor rests on top. It just has to hold a rivet. This might be the stuff. Need to look into what thicknesses are offered.

 

[Firebrick43]

Use Coosa composite panels 1 inch thick and Skin with fiberglass/epoxy. I use coosa board to replace rotted ply in boats. Good stuff but suit up to cut as you will itch something fierce if you dont. Use a nautical 20 or 24 series board

 

[hawkeye2]

Checkout this camper build. He uses aluminum & foam composite walls.
https://www.garagejournal.com/forum/showthread.php?t=466397

 

[Skiff Builder]

One very fast, simple, low cost way to do this is with 1" Medium Density Overlay (MDO) Crezon is one brand. plywood. Cut, seal edges, It's ready for paint, which it takes and holds very well.
Penalty is a bit more weight than foam/skin composite but your done in one day, clean.
Any decent lumberyard can get you 1" about $100.

Examples below in my current boat build. Not painted yet.

 

[Git]

That was my first thought also - MDO. Virtually ready to paint with minimal prep and it usually won't splinter when you cut it like plywood will

 

[milwaukeephil]

Thanks for all the ideas guys! I've sent all the options over to my buddy and we're planning to discuss over beers Tuesday. I'll report back.

 

[duc916]

If you decide to use plastic again compare the coefficient of thermal expansion (CTE) to the HDPE you have already tried. If the new material has a CTE similar to HDPE you will have the same issue. The HDPE might work but you will need to change how you mount / restrain it. The panel will need to float so it can expand and contract without buckling/bubbling.

 

[Doug Arthurs]

I hope you will keep us updated on this project. I am looking at building a pontoon house boat and would love to see pictures all the way along your rebuild.

 

[ez-duzit]

...We rebuilt the walls with 1/2" foam but used 1/4" HDPE panels instead. BIG MISTAKE. Within a day the walls started bubbling. We left it in the sun for one afternoon and the bubbles got way worse than this pic:

...

Wrong material and color (black) choice. Likely wrong adhesive too.

Stick with what lasted 40 years.

 

[kwb]

I would go with 1/2" MDO or something like if for the panel and then just rip strips to thicken the edge to fit in the aluminum.

Plastic is going to be a PITA. Maybe some PC or Acrylic but PE is going to have way too much growth/shrink with temperature changes.