Patching spoil board...

[harryball]

Well guys... I'm still here, just been busy busy. I guess in the rush my mind got lost and I zero'd to the wrong place :-)

Anyway, I have a 24" long 3/8" cut into my spoil board about 3/8" deep. It's out in the field, not close to the edges. When this happened before with a 1/4" bit I just used wood putty and filed the void. It worked well, another 6 months without problems. This one is larger and I was preparing to fill it with wood putty, then thought I'd ask.

I did get my XPS foam, it looks promising... just need TIME... more TIME. For indoor projects, has anyone primed XPS foam (the blue stuff like from home depot) with anything other than the epoxy smooth on type stuff? I was wondering how something simple like Kilz2 would do.

Bat house sales are still doing fairly well, we've been out numbers from last year so far. I've been experimenting with new ideas but again... I need more time in a day than I have right now.

/RB

[Brady Watson]

Robert,
Just fill with putty or inlay a piece of wood & CR it flat...

The problem with latex/water-based stuff on foam is that it leaves a lot of air bubbles. You want to get ahold of a product called FSC88-WB (water based) it is sold wherever PrecisionBoard brand foam is sold. Other than that, use Zinser B-I-N white pigmented shellac in a red & white spray can (Depot)...but do not get the white & gold can - it melts foam. After you have a barrier coat with either product to encapsulate the foam, you can top coat it with whatever you want. Some use truck bedliner spray, but this is essentially the same polyurethane type stuff that smoothon sells for coating foam, give or take a few differences.

-B

[ed_lang]

I use fiberglass resin I get at Advance Auto. I also use it between my zones to keep air from moving between zones in the spoilboard. I cannot take credit for that as Jay Wyant showed me that on his ShopBot. Works GREAT!

[scottcox]

To take Brady's inlay idea further, cut a 3/8" deep bat shape around your goof, then inlay a wooden bat cutout and surface flat.

[Gary Campbell]

Ed..
For a quick & easy fix use one of the bondo clones...hardens quick & sticks to most anything, sands easy.
Gary

[propellers]

We use bondo for all these goofs. If its a large cut then cut a peice of wood to fit veeeery loose in the void, fill with bondo, shove the wood in and after cure CR or sand flat with the table. We use Bondo to also hold parts to the table, works great for those hard to hold item. At the moment the Bot is surfacing several warped board flat all held down on the corners with Bondo. After cut we will run the flat side table down in the planer and will end up with a warpless board.

[harryball]

Thanks for the input... This "Zinser B-I-N white pigmented shellac in a red & white spray can" is very intriguing. Sounds like a simple easy to complete process. I'll give that a shot first and go from there.

Bondo... that's an idea, it would repair the spoil board nicely.

/RB

[ccw]

Can i stick my nose in here?
I am replaceing the spoil bd and im useing the trupan product this time.
My question is do you need to surface the under side as you would with regular mdf.
it stuck in my mind that you did not.
just thought i would check.
Mark

[harryball]

There are differing opinions on this... I surface both sides... when I tossed Trupan UL on my bot and turned on the vac to surface the first side I watched the vac pressure fall as the first side was surfaced, so I flipped it for the glue down. Removing the skin on one side allows more air to flow ergo removing the skin on both sides will let the maximum air flow. Granted... when I surfaced the second side the loss of vaccum was small, but it did change.

I think it could also have something to do on where the sheet was in the full stack... I have to believe (right or wrong) that the pores on the lower sheets of a double stack of 66 sheet pallets must have more pressure on them compressing the surface and closing the pores more. Just my thought process...

In the end... it can't hurt.

/RB

[Brady Watson]

I'm not a big fan of Trupan as a spoilboard material - unless you are using it as a vacuum bleeder board on top of a machined grid. You really need to have a plywood support board, and a sheet of MDF, Extira, MDX etc glued down to that. If using vacuum, then machine your grid & put your trupan on top. Skim-machining the trupan is optional. I haven't noticed any increase in performance by skinning trupan...MDF - yes, but not trupan. Trupan really isn't stiff enough as a support board, so don't bolt it to your steel xmembers. It WILL sag on you. The other reason I don't like it as a spoilboard is that it really doesn't hold screws very well. It isn't dense enough. MDF etc will take a screw in the event that you have to screw parts down.

Be sure to GLUE down your spoilboard to your support board. Screws are bad news...

-B

[thecustomsignshop]

We use Bondo to patch the spoil board. As for a spoil board itself, we use xterra(sp). Agree, avoid using screws.

[mitch_prest]

if you did have to use screws .. would brass screws be the way to go

[harryball]

I guess my terminology is shifted a bit... I use a plywood base with a 1" piece of exterior MDF that has the plenum cut into it. I surfaced the plenum to make sure it was level. It has 4 zones cut into it. I then glued a 3/4" Trupan UL on top.

It is the Trupan that I made the cut into. It didn't destroy the surface, it cut about 3/8" into it and created an area that will loose vac quickly if opened up.

Screws are a bad idea, but if you have to use them make sure they are non-ferrous and will not create sparks if struck. Creating sparks while creating fine dust particles and providing ample airflow is a good method for starting a fire.

The patch worked, thanks guys!

/RB