Spoil board MDF alternative?

I live in Haiku Maui. MDF and Haiku don’t get along well long term due to humidity.

Any suggestions for cost effective material to replace the MDF spoil boards that won’t absorb moisture like a thirsty sponge?

The foamed PVC sold as plastic lumber seems a good option — I used it on my SO3:


Not sure about cost effective but there have been those who have used HDPE. It comes in varying thicknesses, up to 0.75 inches. Will not absorb moisture.

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It just makes you cry when you cut into it

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I would totally use the PVC boards as @WillAdams suggested. But in my area none of the big box stores carry them. I also live in Salt Lake City, UT… so a desert and opposite of HI, so likely why I can’t find it here.

Do stores near you not offer a ship and pick up at store option?



I’ve been looking into the same thing, a material that is tough enough, waterproof, and cost effective.

I initially thought about PVC, but it seems a bit soft. The PVC I use for signs & decorations is the foam core. I haven’t seen any solid core locally.

Then I considered something like the Trex decking material, but it’s hard to find solid pieces, and the widths for deck boards are 5 1/2", not enough to get two 3" slats.

I recently saw some lawn/beach chairs made from recycled HDPE. I’m going to see if I can source that locally.

I’d like to explore the option of milling out some channels in perhaps the 4 center slats & adding vacuum for workholding on jobs that it’s appropriate for.

I redid my deck a few years ago with this:

It’s a lot more expensive now but it wasn’t exactly cheap then. It is a mixture of HDPE and Fiberglass with zero organic material with Trex and some of the others have. It machines very well, I wish that I had my CNC when I did the deck for some of the trickier cuts.

It does have a lot of little pinholes when you get below the HDPE outer shell. For most cases that wouldn’t matter but may not work for your vacuum case @Tod1d.

Are you thinking independent channels on each of those 4 center slats with a separate vac line in each with valves?

EDIT: oh yeah. You can get it in 7.5” widths.

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Nope. They won’t even ship it here. :smiley:

That is really odd. I wonder what the restriction is.

I’m guessing the exterior stuff is just not sold enough here to even bother with the logistics? I can get Trex deck stuff, but it would be horribly expensive an inefficient. I can get the interior trim boards, but it would cost around $130. Might be worth it if I cut more often with coolant, or lived in a humid environment. I’ve thought about HDPE, but that would cost a fortune and most things I use coolant for, get run on the HDM with tooling plates and vises. :slight_smile: