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Rot Test

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This thread ran about a year ago...


....and got me to thinking about how fast various woods weather and rot. So I have been running a little test. Several scraps of wood and plywood, just tossed outside to weather on a pile of brush near a woodpile. They went out there May of 2007 and have been rained on, snowed on and generally left to rot. Area is shaded, but these were on top of the heap, so they would drain off and dry out as moisture left. Maybe not the best test conditions......but it's what I did. A better test for what we do might be to glass most of it, but leave a section open to allow moisture in, but not out.

Here is what I started with:


and these plywood scraps....


After one year, here is what they look like:


(Scrap of Hem Fir was added to the pile after the first photo)

and the plywood and some laminations...


Surprise so far is how good the doug fir and hem fir and even spf look. The ash, red oak and white oak have turned a dark grey and don't look too hot. Another surprise is the yellow pine, which looks like it's taken on more water than any of the rest. The cherry has turned really dark, but doesn't look like it has much rot. The cypress and western red cedar still look good, as does the CCA and Black Locust.

The plywoods don't look to bad....that is some OSB for reference, which I figured would go down fast. It hasn't. Despite what they say about not being durable, the Okume is holding up better than the 1/4 inch marine fir or luan.

The long skinny laminations are strips of black locust and osage orange (aka, hedge, bodark, etc.). They were bent to the point of breaking. This was to test a stressed lamination of oily woods to see how well the epoxy would hold up. The busted up one is black locust. One strip did break while still in the clamps (knot), so ignore that. It looks ok so far. The osage orange has developed a small hairline crack in the glue joint of one laminated strip (System 3 Gel Magic with 30/100 walnut shell mixed in for spacer), and looks like it has started to come undone. Osage orange is a very hard, very rot resistant hardwood, that has some oil content. It's used to make long bows, so is very springy and tough. Almost indestructable. It might make a substitute for teak, but is hard to find in straight sections. But it may not hold glue well. Other than some light fading, the wood looks just like it did when it went outside. No hint of rot.

Lastly, here is a piece of luan plywood, glassed over. Half was painted and half varnished. The edges were sealed with epoxy, but not painted or varnished. The paint is System 3 LPU, with the hardener and clear coat. Those dark areas are the System 3 non-skid granules, which trap dirt and have looked dirty like this since nearly day one. BTW, the first picture was from a year ago, and the second is current, but this piece has been outside now just as you see it for at least 3 years.


and current....


I guess the point is if you want to cut down on maintenance, paint it. ;)

I'll leave em out another year and report back next summer.

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The only one that surprised me is how much better the painted plywood did.  I guess that shows you the effect of UV exposure even in non-tropical areas. 

Its an interesting test; I don't think the weathering (graying) of the cedar, etc. really means they are more susceptible to rot, but it will be interesting to see what happens over the next year.

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Grey and weathering doesn't bother me much. I'm looking for spongy rot.

Purpose of this is to ID and avoid putting wood like red oak on a boat. On my Spindrift, I had made my knees and breast hook out of red oak before I realized my error. Changed them out to Black Locust, which is stronger and has a high degree of rot resistance. And varnished, it looks really good.

BTW, both Black Locust and Osage Orange are used as fence posts in the midwest. Untreated, and cut green, they will last 50 years plus, with half of the post stuck in the ground. Once a hedge post has cured and is dry, you gotta be really good to drive a nail into it. A fence steeple will just bend over on you at the slightest miss hit with a hammer. Couple that with the ability to bend and not break and it seems like a natural wood for a tiller (still thinking of Charlie Whipple's tiller that broke), provided it's a one piece and not a lamination.

Perhaps a better way to duplicate Dale's condition would be to wrap these pieces in a tarp or scrap of plastic or garbage bag? His tarp would shed rain, but would also trap moisture. Tarps do that, which can be proven by putting a piece of clear plastic or a tarp on a grass lawn and watch the moisture form.

I may look around for some more scraps of the same stuff, and put some uncoated and epoxy coated scraps in an unsealed garbage bag and put that out too. Some painted, some varnished and some clear.

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Hi Howard Johno here from down under.I found your rot test interesting,I did a similar test with Meranti marine ply that I used for my weekender.I started the test 12 mths ago and had a similar result to you,Meranti always worries me as I dont regard it as a durable timber,same for Oregan Pine,if not protected with paint they suffer the affects of rot ,some times surprisingly rapid.This has been my experience over the last 25 years repairing boats and houses,and the culprit is always freshwater gaining accsses some how.I still think that the proven rot preventative is linseed oil cut 50 50 with kerosene then oil based paint thinned with kerosene not turps and then oil based paint.This of course does't work with using fiberglass on timber,which I think is wrong anyway,any timber that does duty outside cries out for oil,particularly in boats.This I know will be regarded as heresy by many,wait till they have a decent impact with their boat say having to come alongside a jetty in squally conditions,the fiberglass gets cracked ,even minutely,water seeps between the ply and the fibreglass,and so begins the end of a boat,and I have seen it OFTEN! The up side is that the weekender is usually built by the owner so his or her maintaince will likely prevent such an outcome,however I think that fibrglass is best used as a solid hull not as a component in a timber hull.  Something else about Oregan,it's become noticable that timber that came from the Mt St Helens area ,after the event,is very prone to decay,something to do with the age or the condtion of the trees after being partly cooked by a volcano,just a point of interest on what affects timber

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