PVC spoilboard

[Acmeaviator]

Unfortunately my buddy is in a non-temperature or climate controlled shop. I have had a hard time with various spoilboard materials warping and requiring frequent resurfacing so I've decided to pop for some PVC and solve the problem for good. I have a few questions:
1. Should I remove the factory MDF table and attach two layers of PVC (table and spoil) - if so what thickness would be best for each?
2. Should I leave the MDF table and just use PVC for spoil?
3. Will the increase in weight affect the performance of the buddy?
4. What "ugh knowns" should I be aware of?

Appreciate any help any always:D

[steve_g]

Brian:

My shop is a similar situation. To get any sense of stability/consistency I had to get rid of all MDF. Currently I am using multiple layers of Baltic Birch with good results. In the past I have used Sintra as my top layer also with good results. Note*I have always used double stick tape and don't have a vacuum system.

Steve

[cowboy1296]

i am posting only because i want to know the answer myself. i know that there were postings on here before about a template for the bolts to hold the sacrifice board to the power stick, that would be nice also. i used 3/4 inch plywood (because it was handy and shopbot did not send me one) and noticed some warping on the bottom which bumps on my rollers.

[CNYDWW]

Assuming you're speaking of Exterior PVC sheet that is actually a foam. I haven't used pvc as a spoilboard but there are a few things to consider when using it. I do do a lot of work with the material. PVC isn't self supporting, you should use another layer of material along with it or an aluminum substructure. It's soft enough the rollers on the buddy would eventually dent the material or wear grooves in it. I would actually consider two layers of 1/2" veneer plywood with a 1/2" sheet of pvc sandwiched between, glued with urethane glue and a lot of weight. With that it should be rather stable and hold up well to the use on a buddy.

[Brady Watson]

I'll chime in from the other camp that wouldn't recommend PVC (of any type) for a spoilboard, support board or plenum. In fact, I have removed a number of PVC setups and replaced with Medex.

Contrary to popular belief, PVC - expanded or Type1 Gray, isn't any more stable than a number of other more affordable options. If you machine a grid into it, it will have a tendency to want to curl on you. When you bolt it down, you need to slot the bolt holes to allow for expansion & contraction because it will buckle between the bolts, causing 'rainbow' shaped rise & fall between crossmembers. PVC does NOT take a screw, so you can rule that out if you ever have to screw a part down. If you want to use it for a plenum, I have yet to find an adhesive aggressive enough to keep the bleeder board nice & flat & stable on top.

I've torn off & replaced my spoilboard a number of times over the years & the most stable combo I have found is MDO plywood as the support board and Medex moisture resistant MDF for the spoilboard. Medex has a high plastic resin content & it machines nice & flat, with almost a slick finish with NO fuzzies. It also puts off a chip/curl when cut & takes a screw well. It is ultra stable. The trick is to GLUE the Medex down to the MDO & use no screws except for the carriage bolts holding the MDO to the frame.

I've spent a ton of cash fooling around with PVC, phenolic ($$$) and a number of other substrates in the hunt for a stable bed. MDO & Medex are hard to beat.

-B

[Acmeaviator]

Brady your setup sounds like the best solution. In the last few days my shop has gone from 30's to 80's with some rain blown under the door for good measure. My current spoilboard (3/4 mdf screwed to the factory mdf table) is lifted enough at the front edge to visibly see the gap:(

[nat_wheatley]

Brady,
With the Medex, do you still need to use a sealer on it after you've routed the plenum?

[Brady Watson]

There is certainly no detriment in sealing the plenum with poly or epoxy. I don't bother...but I make sure I don't puncture the bottom layer creating leaks - and definitely seal the edges with wood glue. On my table, a 1.5" layup of plenum & bleeder X 5' X 16' = over 2 square feet of open area for leakage, just at the edges(!) So...I make sure I seal them up. The phenolic paper on the MDO effectively seals off the bottom support board to plenum.

-B

[nat_wheatley]

Got it, thanks Brady.

[wberminio]

I did a similar setup 4 years ago as Brady suggests.
Maple ply base(laminated top and bottom with plastic lam)
Medex plenum glued down
Still stable as day one