Sinker Log Issues

      A discussion of the sawing and drying characteristics of recovered sunk timber. May 11, 2005

Question
I found a source with some 100 year old sinker logs (pine and cypress) from a river in Louisiana. These logs would have probably been 100 years old when they sunk about 100 years ago. I have been told that when cut, the lumber is a little darker than that cut from a fresh log. And of course they have about 15 growth rings per inch. Has anyone out there had experience with sinker logs as to strength, discoloration, sawing difficulty, etc.?

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
Ask yourself first why the logs sank. It is likely that they were bacterially infected and had a higher MC than normal. This bacteria could also have affected the color and strength. Therefore, it is commonly found that such logs will produce lumber, but some sections of the lumber might be inferior in quality. You may also note that the sapwood is not usable. Sawing is easy, although the higher MC means slower sawing. Before sawing, you do need to clean the logs to eliminate debris. Drying is easy, but slower rates than normal.



From contributor D:
Colors can be very unusual and will vary greatly from log to log. I never before heard anybody say that wetwood was easy to dry. I've heard the exact opposite.


From the original questioner:
Gene, it's my understanding that these logs were part of huge rafts that were used to transport the logs. Last year I put several freshly cut pines into my pond to preserve them. They barely floated at first and within one week, they were on the bottom. I did not expect that. Have not yet pulled them out. I am scheduled to go and look at some of the lumber cut from these sunken logs in a couple of days. The price he wants is $1.50 bf for logs and $2.00 bf for squared cants, for either pine or cypress.


From Professor Gene Wengert, forum technical advisor:
If a log gains more water while it is in a lake, river or pond, that water will come out easily. If the water gain above normal is due to wetwood ("wetwood" is a special term and is correctly used for a special type of wood that occurs in the living tree and is closely associated with bacterial infections that weaken the wood), then wetwood must be dried more slowly. Slowly does not mean drying is harder… rather, slowly means drying takes longer. But no special techniques to control warp, etc. are needed.

However, it is very difficult to dry wetwood without some quality loss, as some of the wood is so much weaker than normal. Because the stresses that develop in drying cause the problem for wetwood, it follows that wetwood could be dried better in a system that dries wood without developing such high stress levels... a conventional system that dries more slowly (as I stated earlier) or a vacuum drier that is properly operated to avoid large MC gradients and stresses. The RF-vacuum and electric blanket-vacuum systems did develop stresses and then honeycomb in drying, so it would have to be a different type of vacuum drying.



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