Weatherproofing MDF?


Howdy,
Anyone have any ideas as to how I can weatherproof, as much as that's possible, some 1/2" MDF?
I'm planning a new portable slot car track to replace my current one and I want to make this one a routed track, it will be attached to the top of a torsion box that is then mounted onto a utility trailer.
I'm not locked into using MDF, but it is the recommended material amongst track builders.
I know it soaks up moisture like crazy. I won't be using it in the rain or snow, it will be stored outdoors with a cover on it. I live in SoCal so there's really only a couple of dozen days of rain to deal with.
Any thoughts or ideas welcomed.
-- John Emmons
"when hatred calls with his package, refuse delivery..."
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John Emmons wrote:
> Anyone have any ideas as to how I can weatherproof, as much as that's > possible, some 1/2" MDF?
Doubtful, IMHO.
> I'm planning a new portable slot car track to replace my current one and I > want to make this one a routed track, it will be attached to the top of a > torsion box that is then mounted onto a utility trailer. > > I'm not locked into using MDF, but it is the recommended material amongst > track builders.
I don't know about track builders, but how about MDO?
> I know it soaks up moisture like crazy. I won't be using it in the rain or > snow, it will be stored outdoors with a cover on it. I live in SoCal so > there's really only a couple of dozen days of rain to deal with.
Since you are in SoCal, forget about trying to seal using epoxy, the sun's UV will kill it.
Varnish is probably best.
Lew
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I'm not familiar with MDO, what is it?
John

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A plywood like material made for outdoor use. Many road signs are made from MDO. Comes in 4 x 8 sheets
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MDO medium density overlay
it's a resin coating that is fused by heat to the plywood.
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John Emmons wrote:
> I'm not familiar with MDO, what is it?
Plywood for outdoor signs.
Has a paper coating bonded to it.
Since you are in SoCal, check Gahnal<s/p>, know they have it.
Lew
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On Wed, 16 Aug 2006 19:44:50 GMT, "John Emmons"
As far as I could tell looking at it at the lumberyard, it's regular old pine plywood with a very thin layer of veneer-like hardboard on each side. I'm assuming it's for projects that are going to be painted- can't think of any other good uses for it offhand.
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There is always waterproof MDF which is weather proof...
http://www.sierrapine.com/products/mdf/medex/default.asp
MDO might be a better option and can be bought from a local sign company....
There are "many" versions of MDF, not just the one you saw at Lowes or Home Depot.
John Emmons wrote:

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what about fiber glass? you can use the cloth or just the resin. it would help if you did all surfaces and then painted.

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snipped-for-privacy@worldnet.att.net says...

If you can avoid chips and dings, a water based primer and 2-3 coats of oil based enamel will work just fine. The moment you break the paint you will have to redo that spot or you'll be up the creek the moment it gets seriously wet. Rounding over the edges and corners will help greatly to preserve the integrity of the paint.
I'd probably use plywood. The better grades should do the job just fine. (More layers for the same thickness is what makes it a better grade as a rule).
h.t.h. -P.
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John Emmons wrote:

You can't.
If you _must_, then replace the MDF with Valchromat -- an extra resin MDF that's soid colour all the way through and significantly more resistant to moisture. I use it for bathroom fittings, but I'd still be wary of real outdoor use.
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John Emmons wrote:

I don't think it's possible. Why not use exterior grade plywood?
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I'm leaning towards trying that. MDF is the preferred material for what I'm trying to build, it's flatness and ease of routing the slots and you can bend it for banked turns.
My track will be basically flat and I need the weather protection more than the other attributes so it sounds like MDO which has been recommended by several people will be the way to go.
John

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So, now that you have all these answers from people telling you that if you remove a piece of MDF from it's protective building and take it outside, it will dissolve, I guess it's up to me to tell you the real truth. I've had an unfinished MDF box sitting outside, unprotected, in Seattle for over a year. No, it's not in very good shape but it's still around. In your case, since you are going to keep it covered and the weather is as good as it is where you are, there is no real need to do anything special other than put SOME kind of finish on it. BTW, I wonder how people get their MDF home since, as they claim, it decays when taken out of a building.

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John Emmons (in tIJEg.627700$ snipped-for-privacy@bgtnsc05-news.ops.worldnet.att.net) said:
| Anyone have any ideas as to how I can weatherproof, as much as | that's possible, some 1/2" MDF? | | I'm planning a new portable slot car track to replace my current | one and I want to make this one a routed track, it will be attached | to the top of a torsion box that is then mounted onto a utility | trailer. | | I'm not locked into using MDF, but it is the recommended material | amongst track builders.
It might be worth your trouble to investigate Extira, a product that looks and machines much like MDF, but isn't vulnerable to moisture. I use it for outdoor signage and it has worked well for me.
It's a bit heavier than MDF (90#+ for a 3/4 x 4 x 8 sheet) - and it's definitely harder on router bits - but it may be a good solution for you.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto
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Hi John:
As others have said, MDF isn't really a good choice for outdoors.
A few years ago, I would have been in the "use MDO" camp, but my experience of late has changed my mind. MDO is indeed regular plywood, with a waterproof resin-impregnated paper bonded to one or both sides (you can buy it either way). The surface is waterproof. However, the plywood inside is not treated against decay. Any unprotected edges or holes will allow moisture inside, and become trapped between the waterproof surfaces. Unless you are VERY careful about sealing all exposed edges and holes, moisture will find its way into the inside and begin rotting it from the inside out. Perhaps if you are meticulous about painting it, and you keep it covered, and don't drive through puddles, etc., you'll be fine with MDO, but I thought you should know that it's not without risk.
My recommendation would be to get exterior-grade plywood, or even pressure-treated plywood. It's typically not very flat, but if you're going to mount it to a torsion box, you should be able to get it flat and keep it that way. Non-treated plywood will still need painting, but it shouldn't have the same level of moisture entrapment as MDO. Pressure-treated plywood should last many years.
Regards, John.
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John,
I'm catching up on threads. If you haven't bought anything yet, why not post this question on www.slotside.com ? One of the folks in the hobby may have already faced this problem. I assume you're painting the track in blackboard paint.
I've got a few drawers full of memories that date back to 1962-3. Still have my old Cucaracha and a Cox Lotus 40.
Regards, Roy

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