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Thread: Acclimating wood for project

  1. #1
    Join Date
    Dec 2010
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    Acclimating wood for project

    I am not a boat builder, I usually build furniture for indoor use, however, I'm building some pieces for outdoor use (personal use). I figure this group would know more about processing wood for outdoor use than anybody.

    I recently built an outdoor bench using ipe and white oak. The ipe is 5/4 x 6 boards for deck building, was stickered/stored inside my climate controlled shop for about two weeks before processing; I've had the white oak for years.

    The joinery involved pegged mortise and tenons for breadboard ends.

    Everything was hand fitted, sanded smooth, and finished with Penofin Marine finish.

    I've had it outside for a couple weeks now and have allowed it to receive rain, full sun, etc. Basically, I am abusing it to determine durability and identify issues; I've identified one so far.

    The M&T joints are still tight but not even; the breadboard ends have swelled and are now proud of tenon boards meeting them.

    Would I be better off to leave wood for exterior use protected and outside prior to processing, thus negating expansion issues?

  2. #2
    Quote Originally Posted by Dale Murray View Post

    Would I be better off to leave wood for exterior use protected and outside prior to processing, thus negating expansion issues?
    It would definitely do more to minimize wood movement, i.e. expansion.

  3. #3
    Join Date
    Dec 2010
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    Wheaton, Illinois
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    I know little about boat building aside from it is a bit of an art. How do you accommodate for wood movement?

    What I have found, done, likely do.
    Found:
    I noticed last night the grain of the ipe is now raised. First the joints raised but the wood was still super smooth, and now the grain is raised too.

    Done:
    Using an 18" piece of ipe I measured across the width and thickness in three locations using calipers. I have since placed it outside where it will sit for a couple weeks then I'll measure again.

    Likely will do:
    1. After waiting a couple weeks and measuring the changes to the piece outside I'll cut it in half, create a pegged M&T joint, sand and finish like I did the bench. I'll then put it back outside and see if the joint or surfaces change.
    2. Bring in the original piece, sand and finish again. Place outside and see what happens.

  4. #4
    Join Date
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    Quote Originally Posted by Dale Murray View Post
    I know little about boat building aside from it is a bit of an art. How do you accommodate for wood movement?

    What I have found, done, likely do.
    Found:
    I noticed last night the grain of the ipe is now raised. First the joints raised but the wood was still super smooth, and now the grain is raised too.

    Done:
    Using an 18" piece of ipe I measured across the width and thickness in three locations using calipers. I have since placed it outside where it will sit for a couple weeks then I'll measure again.

    Likely will do:
    1. After waiting a couple weeks and measuring the changes to the piece outside I'll cut it in half, create a pegged M&T joint, sand and finish like I did the bench. I'll then put it back outside and see if the joint or surfaces change.
    2. Bring in the original piece, sand and finish again. Place outside and see what happens.

    It would be a good idea to use a moisture meter and track the moisture of your test subject for as long as possible- ideally for a whole year. Chart it, and then for future projects you know your mean and median moisture levels and can target that to use for projects for outdoors. I live in the tropics and my shop is open-air, and my home as well, although we do have A/C- it's just rarely ever used, so I don't deal as much with this. When I buy wood, I let it sit and acclimate for anywhere from a week to a month, depending on where it came from, and what the moisture level is. I'm about to buy some spruce from Massachussets. Since it's summer there, and the wood will transit by boat from Miami, by the time it gets here it should be close to usable. I will let it sit a week, then rip it close to size, then let it rest a few days, then plane it. These are staves for a hollow birdsmouth mast, so they are rather thin and once ripped shouldn't take long to acclimate. It does, however, make a big difference to let the wood "come up to moisture" before using. For where you live, the seasonal changes are going to be vastly different, so you will have movement as seasons change. Using pegged tenon joints, i.e. drawbore pinned, will allow for movement without losing strength.

  5. #5
    Join Date
    Dec 2010
    Location
    Wheaton, Illinois
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    363
    Ipe is hard as a stone; makes white oak and hard maple seem like butter - it would break the pins of a moisture meter I am sure.

    If I decide to sell this - commissioned only - I will ask for their region and if it is for interior or exterior use. I will then try to acclimate for wood to this region and use.

    The ipe I'm buying is for deck building, milled to 5.5" x 1". When I process it I try to end at 7/8" and whatever I need width wise. Worst case I have a few piece end up at 3/4" thick.

    When I designed it I tried to think of all the possibilities of water infiltrating the joints and how I can mitigate it.
    - I used zero adhesives.
    - All hardware is stainless steel.
    - All joints are pegged tenons. (I did not use a domino as some suspect)

    I should get a book on boat building, or better, boat finishes. How did they keep those Chris-Crafts looking so nice?

  6. #6
    Join Date
    Jun 2009
    Location
    Katonah, NY
    Posts
    177
    Those Chris Craft boats look so nice (due to constant upkeep and their owners rubbing them with a diaper daily) because the builders understand that no finish will inhibit the moisture uptake of wood 100% - they will only slow it down - which means - left long enough in the outdoors, your wood will move around with the season and come to equilibrium no matter the finish used - even if encapsulated in epoxy. You have to plan each joint for the movement which will occur.

    Take your bread board ends for instance - if you build the project with the wood at max expansion (you left the stock outside in the rain for a week prior to building), and made a nice tight joint, with the BB end being the exact width of the table, it would appear proud in the winter since the top has shrink down a little in width in the winter when equilibrium moisture in the air is lower, thus your tight exact bread board end will appear a little long cause the inner is now smaller. If you do the reverse, as you have, in summer, the inner is expanded and now a little proud of the BB end. You have to pick your poison - or use a different method to keep the top flat other then bread board ends.

    After typing this, I went back and saw you said that after exposure to the rain, the bread board ends are proud of the inner top. That seems off to me - - I would think the top (inner) would be proud of the BB ends, not the reverse, since the inner will be at max width due to expansion now (humid summer), and since the grain in the BB ends, I assume, is running the width of the top and any expansion would be along the table length and be unnoticeable.

    Russ

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