Drying Wood

Discussion in 'Materials' started by Inquisitor, Jul 5, 2010.

  1. Inquisitor
    Joined: Nov 2005
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    Location: North Carolina Mountains

    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Brief - What is the quickest (for rough estimate) way to simulate drying strip planking? Oven, food de-hydrator?

    Details - I'm building a boat with strip planking. Locally I can get either Cyprus or Fir... both of which are rather green.

    I'm trying to get a handle on the density it will be when I finish planking... say at least 6 months. A book I have says they'll be around 36 lbs/cu-ft. But doesn't really give details. I got a few samples in the thickness I need for the strip planking 0.375".

    Right now...

    Cyprus' density is 40.6 lbs/cu-ft.
    Fir density is 27.3 lbs/cu-ft

    I don't have a moisture meter. Is it possible to either put them in the oven (at some temperature, for some time) or a food de-hydrator and get a rough idea of their final density.

    Thanks for your help.
  2. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    There has got to be a mill with a lumber kiln somewhere close. or buy 2 x 6 or 8 dry and cut it for your planking. it takes about 2 weeks in a KILN to get dry. Ask a private lumber dealer where the nearest kiln is.
  3. apex1

    apex1 Guest

    First find out which lumber you are talking!

    Most species are sold under different names!

    This may help:


    Here you will find some info how the choosen wood behaves in kiln drying.

    Take care, many species are fuel wood when dried too rapidly.

  4. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    I think the biggest issue is shrinkage as it drys, not so much moisture content. You might cut a few sample blocks of thickness you want and accurately measure cross grain dimension daily as you dry it out in a warm dry place. You will see most dimensional change in first few days/weeks, and amount of shrinkage will drop off. When you are down to about 2% change per week, it is about where you want it. This way you do not need a moisture meter.
  5. Boston

    Boston Previous Member

    this one is right up my ally

    dry schedules are entirely dependent on the specific species of wood you are trying to dry

    your best bet is a solar kiln that you can make at home and use the prescribed schedule /2 so you ensure against season checking

    that means that your going to remove half the recommended moisture PR/DAY
    that way your wood will be at its most stable when your done

  6. Inquisitor
    Joined: Nov 2005
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    Location: North Carolina Mountains

    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Sorry... I must not have clearly written what I was needing...

    Part of it was I miss spoke... when I said "green". You all assumed I meant I had just fallen the tree. What I meant was a local euphemism and slurring that I just got it from Home Depot. I often do simple wood working projects using their wood, and I often see wetness squeeze out when running a nail through it.

    I am trying to determine which wood I need to use. The boat scantling says I can use anywhere from 24 to 32 lbs/cu-ft. I wanted a procedure to dehydrate samples (say in a day or two) of each to estimate the density of the wood used in the boat that will air dry over 6+ months (not kiln dried).

    I have run the samples through a food de-hydrator so far.

    Fresh from Home Depot
    Cyprus 40.6 lbs/cu-ft
    Pine?/Fir? 27.3 lbs/cu-ft

    12 hours in food de hydrator
    Cyprus 36.6 lbs/cu-ft
    Pine?/Fir? 25.3 lbs/cu-ft
  7. Boston

    Boston Previous Member

    I would stick with the schedule for kiln drying and use there specifications on end results for each species

    for instance I have several reference guides that indicate what wood weighs at each moisture content
    taking the wood down to that content is key to the integrity of the wood

    Home depot couldn't care less about its quality as long as someone is equally as careless to buy, it they are happy
    the manor in which they stack there "finish" wood is indicative of some exec who never touched a piece of wood in his life.

    If your building something small just go to a local mill and help support the locals cause they will actually sell you wood that wont splash when you go to sink a nail in it and at a quarter the price of Home nitwits

    my two cents

  8. Inquisitor
    Joined: Nov 2005
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Unfortunately, I live in Home Depot's home town... I have three Home Depot's and two Lowes centers within five miles of my house. They've basically run out of business anyone in the category of which you speak.

    I have never done something of this scale. I've only done cedar strip kayaks in the past. I would like to use a home town mom & pop and even have someone that would cut the strips. Maybe you have an alternative suggestion if I give more details.

    • I'll be using Lindsay Lord technique (as described by Dave Gerr). It is very tolerant of wood quality. Gerr describes that butt joints are OK as well as not beveling edges. Filling voids between strips and in knots with epoxy grout.
    • Max displacement 10,000 lbs.
    • Predominant strip thickness 0.375" to 0.4"
    • Surface area to strip = 1800 sq-ft.

    Right now, if I use the Canadian Fir (has a KD desination) it'll be $800 plus several table saw blades and lots of boring time.
  9. Boston

    Boston Previous Member

    I'm feeling pretty qualified to speak to the issues of wood characteristics and quality of different grades, drying practices, storage, things like that( although some folks might disagree with my view of Douglas Fir and Poplar ) however

    I would refer you to some of the more experienced members in the actual construction techniques Old MR Gerr is suggesting as my experience in that specific area is limited

    Home Depot and Walmart have very similar business models which are essentially designed to bleed this country dry while there employees are subsidized by welfare programs paid for by what few successful americans are left and there manufacturing is a virtual slave based economy on foreign soils taking jobs from the local American economy and selling them overseas to the lowest bidder willing to sell there own people into what amounts to indentured servitude IE slavery by any other name.
    doing business with there kind is synonymous with slitting your own throat.

    just a little food for thought

    property values go down whenever a walmart or home depot move into an area cause realters know that as the local businesses go down the tubes so does the local economies and so does the property values
    we all pay for the subsidized profits of those vultures

    happy shopping

  10. tunnels

    tunnels Previous Member

    From the wood flooring trade:confused:
    Use a big plastic cover on the ground and stack all your wood with a fillets between each layer then put a standard dehumidifyer along side the stack and then cover everything with the rest of the cover, Each day open the cover where the humidifyer is and empty the tank ,taking note of time and amount of water gathered . After a short time the amount of moisture will start to get less untill there is very little in the tank ,at this point your wood will be at a very low % of moisture :p . its easy its cheap to do and is not harsh on the timber . Just like air drying :) .
    Kiln drying is force drying and not good for the timber :eek: .
    All timber will shrink slightly as it dries ,if done quickly it can do awful things to the timber like twisting and cracking in various ways !:(
  11. Boston

    Boston Previous Member

    you might look into solar kilns that you can build yourself, not sure what area you live in but around here the issue is of the wood drying to fast. Slower the better is a good rule of thumb.

    best of luck
  12. Inquisitor
    Joined: Nov 2005
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Don't know if this is (or will be) of interest to someone else doing research...

    My test samples of Cyprus and Fir being dried in a food dehydrator finally seemed to flat line after several days...

    Cyprus 36.6 lbs/cu-ft
    Pine?/Fir? 23.4 lbs/cu-ft

    And thanks to our lovely southern summers... they went back to...

    Cyprus 40.6 lbs/cu-ft
    Pine?/Fir? 27.3 lbs/cu-ft

    ... within 12 hours of pulling them out.
  13. Inquisitor
    Joined: Nov 2005
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    Location: North Carolina Mountains

    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Several more questions from the wood noob... I gather that the answers will be highly dependent on wood type. But for my question, please consider Fir.

    (1) Somewhere in my research (unfortunately didn't book mark it) I read that Fir is deminsionally stable. In the reference, it stated, that Fir is often cut green, not dried at all, but can be formed up in a strip plank boat and allowed to dry on the boat. That it does not shrink appreciably. Is this your experience?

    (2) I know for some woods that drying too quickly is readily visible. I know my Oak fire wood logs radially split in short order even in our moisture rich air. Does fir show visible damage if it has been dried too quickly?

    (3) If Fir doesn't show visible (eye ball level) damage, is that a sign that it hasn't been dried too quickly? In other words... can Fir be dried too quickly, not show visible damage, but have damage none the less? If so, how can you tell if its been dried too quickly?

  14. rob denney
    Joined: Feb 2005
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    Location: Australia

    rob denney Senior Member

    22 years ago I raced a 12m tri in the Sydney Hobart. That boat was planked with long grain balsa with 300gsm/9 ounce cloth each side. This is far weaker than any of the fir you are using. The boat is still going strong. I don't think you need to worry about the properties of the wood in a strip planked boat being degraded by over zealous heating. The wood is mostly there to keep the skins apart. There is plenty of materials for the longitudinal strength.

    Moisture content is very dependant on ambient conditions. Over the time it takes you to prepare and plank your hulls, cedar would dry out to ambient. Denser timbers will take a little longer. As an example, there are a lot of hulls built in very dry conditions subject to occasional storms. A planked, but unglassed hull will move noticably after a storm, but revert to normal in a couple of days. Once it is glassed, there should be no further appreciable movement unless you paint it a dark colour.

    No idea how much money you are saving vs using cedar or other light timber, but you are adding unremovable extra weight to the boat, which you will have to compensate for with more sail, stronger beams and rig, etc.

    Re tow, I can supply it for $US 12/lb and am currently putting together a half ton order of tow and uni. If you want to be in this, please pm me.

    Last edited: Jul 25, 2010
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