Use Bondo to fill cracks in wood?

I have a couple of 2"x12"-15' facia boards. They get a lot of sun in summer and rain in winter. The wood has split in cracks as wide as 1/4". Since the boards were developing dry rot in the cracks I treated them with borax/antifreeze. Then I caulked them with flexible spackle compound.
Trouble is, due to the constant expansion and contraction of the wood, the caulking is forced out of the cracks. I thought of applying some Bondo (or similar epoxy) to the cracks or to the entire boards.
Will this work or will the Bondo pop out, too? Can I use some semi-liquid bondo and paint it on?
The boards are difficult (expensive) to replace because they are tied in with the roof tiles.
Thanks
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Walter
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Walter R. wrote:

I've used automotive type Bondo with good effect on lots of outdoor wood cracks. It isn't all that great at water resistance, so you have to make sure it's well painted.
Depending on the applicatin, sometimes I'm able to insert a few screws or nails "inside" the cavity I'm filling so that the Bondo can grab onto them and keep from popping out if it's adhesion to the wood isn't too good.
I've always used just the automotive Bondo, 'cause it's easy to buy at local auto parts stores, but Bondo makes an s-load of home repair products, some of which might be better for your application. See:
http://www.bondo-online.com/catalog_brand.asp?hdrBrand=2
Give it a try.
Jeff
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Jeff Wisnia wrote:

I can't find the post now, but I recently read that because Bondo hardens to a solid, you may have popping out due to the wood expanding and contracting around it. Some sort of flexible epoxy product was recommended. If I find it I'll post back. Maybe someone else has the name of it....
JP
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Walter R. wrote:

Siding professionals I've heard from always recommend against using Bondo. You need something flexible that will move with the expansion and contraction of the wood.
Prime first so the caulking (or flexible filler) has something to stick to, then apply the caulking/flexible filler.
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wrote:

Maybe you could bond a thinner board over the whole thing to cover it as a veneer? You'll be able to get a smoother and more durable finish that way.
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Squirt glue into the cracks, and clamp the wood. Then that crack will be permanantly repaired, and the wood will split somewhere else.
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Could you explain this one for me, Walt? I hadn't heard of this before.
<snip>

Along the lines of veneering with a thinner piece of wood, could you have it faced with aluminum sheet stock formed to fit? I don't know what your styling is so this just may not be appropriate.
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Here's a link for the Boracare wood preservative story and recipe:
http://www.terryking.us/public/boats/ethylene-rot.txt
I personally find that mixing with boiling water is sufficient to hold solution if you will apply right away. Boiling with a candy thermometer results in a superior batch with long shelf life.
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Please refer to the link provided by John Keiser in his post. Excellent.
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@example.com says...

I've had very good luck with these products:
http://www.rotdoctor.com /
Their "CPES" is great for sealing wood from rot.

Ouch.
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Keith

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