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Thread: Kiln Drying Cypress Planks for Near-Term Use

  1. #1

    Question Kiln Drying Cypress Planks for Near-Term Use

    Hi Sawmill Forum,

    I am a wood novice trying to work out how to properly dry 60 cypress planks that are being supplied as fresh-green lumber. I need the fastest, yet safest, solution as my job is somewhat time sensitive and our workers are ready to make use of the lumber now.

    The lumber is for a 108-passenger wood ship from the early 1970's. The hull between the water line and the main deck uses 8 quarter cypress planks that average 16ft long and 5-6 inches high (which I believe sawmills refer to as the width). Sixty of these planks are on their way to us in Southern California.

    The sawmill cutting the lumber is not drying it, so I have to find a kiln. Based on my limited research, drying wood (and doing it properly) is a science so I could use some help to make sure I am asking the right questions and finding a capable service to get it done right. This forum is terrific as I've been able to educate myself on some of these questions which are below in bold for those who want to get right to it.

    We removed the bad planks already and covered the cavities with plastic, so there is some urgency to get the new boards in place before our rainy season but I do not wish to rush the drying process and end up with warped or cracked planks. Our entire hull is double planked with cypress. It was quite a challenge sourcing it!

    I understand the concept of drying is to remove most of the water quickly without destroying the wood. People say to dry them slow but, if a kiln and correct procedures are used, how long should I estimate for this process in our project schedule? And, can it be done in under two weeks or is that unrealistic?

    They say to seal the boards to control the drying but what sealer should be used and where is it to be used?

    I read the most critical time of the drying process is taking your lumber from green down to 35% moisture content since most of the degrade occurs during this time.

    I read that each wood species has an optimum drying rate which, when exceeded, will leave you with a pile of warped or cracked firewood. How do I find the drying rate for bald cypress? Is there a drying schedule or drying recipe for cypress?

    I read that certain species, such as pine and cypress, are very difficult to damage in a kiln because they dry so quickly. Is this true?

    Do I need to need to buy a moisture meter? I'm in Southern California, FWIW.

    Once it's back from the kiln, can we install it right away or do we have to wait for it to equalize with the ambient temperature. If we have to wait, how long?
    Since this is for a boat upper hull (these planks are not under water) there is some expansion and contraction that takes place. I've been told the wood needs to equalize before we install it or it seems conceivable it could swell up or contract and cause cracks in the paint that top coats it.

    What type of Kiln should I be looking for, Conventional (High temperature), Dehumidification or vacuum? Are there any in Southern California?

    Do I need to micromanage the service we select to do the drying? i.e., make sure the operator stacks the wood flat and it is weighted down so it doesn’t warp. I respect professionals and prefer to leave them to do what they know but need to balance that with getting this right.

    Thank you for answering any or all all of my questions.

    Nick Baggs
    Marina del Rey, CA

  2. #2
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    How thick are your planks? That factors in to how long they will take to dry.

  3. #3
    My message said they were eight quarter but that was kind of buried in the message. After planing, the planks will be 1 5/8 inches by 16 feet long. The height of each plank is between four and six inches. I have 60 of them to dry.

  4. #4
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    For a guy who'd already bought the green lumber, you have a lot of questions. Here's some answers.

    I strongly doubt that you can find a kiln, and get your lumber dried, in two weeks. I buy hardwood live edge slabs from a guy who air-dries the slabs for a couple years, and then kiln-dries them. His kiln is a dehumidification kiln, and slabs usually spend a couple weeks in the kiln. Maybe he's conservative - I dunno - but the best answer about schedule will come from the guy you find with a kiln. Finding one which will handle 16 foot sticks may be a challenge. Small-batch kilns aimed at furniture-length lumber won't likely be that long.

    Yeah, I'd buy a moisture meter. They're cheap compared to the cost of your lumber, and your boat.

    Finding a kiln to do your job is going to be a big challenge.

    Usually when folks talk about sealing the wood, they're talking about sealing just the ends of the boards.

  5. #5
    Thanks for these answers. I will call the lumber yards in SoCal to see if I can find a kiln. I also hope to find a drying schedule for cypress in case the operator is unfamiliar with this type of wood. Apparently there is little to no cypress coming into the west coast anymore.

  6. #6
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    If you go to EBAC's website you can look up kiln drying schedules for most all woods, including cypress. I looked at the Forest Products Lab report I have on kiln schedules but couldn't find anything for cypress.

    John

  7. #7
    The hard part will be finding a kiln, vacuum will be the fastest but probably also the hardest to locate (not to mention most expensive). Possible good news is, considering final use will be on a boat, your target MC may not necessarily need to be as low as furniture grade lumber, which may speed up dry time, I want to say so cal equilibrium this time of year is around 16% . I would think anybody operating a kiln big enough for what you need should have enough experience to do the job right but its always a good idea to talk everything over, let them know your expectations and go over the drying schedule with them. Unfortunately green baldcypress has a very high mc (as high as 120% I believe) so I suspect even the fastest method will not be terribly fast, I'm not sure if the rule of 1% per day applies in a vacuum kiln or not but if so your looking at a few months dry time.

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    Some softwoods have no maximum drying limit. 8/4 walnut is like 5.5%/day. 8/4 white oak is 1.0%/day. Cypress? No clue.

    John

  9. #9
    Quote Originally Posted by John TenEyck View Post
    Some softwoods have no maximum drying limit. 8/4 walnut is like 5.5%/day. 8/4 white oak is 1.0%/day. Cypress? No clue.

    John

    This is true. I was thinking "rule of thumb" at 1% but it does vary by species, and I have no clue what cypress max may be, off the top of my head I would guess that being so wet while green you would be safe at a higher rate but that's just a guess. I found a spreadsheet a while back that listed green mc and max rates by species, I'll have to track it down, all the ones I've found recently either don't have drying rates or don't list cypress.

  10. #10
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    Quote Originally Posted by Nathan Jordan View Post
    This is true. I was thinking "rule of thumb" at 1% but it does vary by species, and I have no clue what cypress max may be, off the top of my head I would guess that being so wet while green you would be safe at a higher rate but that's just a guess. I found a spreadsheet a while back that listed green mc and max rates by species, I'll have to track it down, all the ones I've found recently either don't have drying rates or don't list cypress.
    If you find that spreadsheet I'd be interested in it if it's sharable. Thanks.

    John

  11. #11
    1000BF of wood (about 50 planks) will be shipped from Mississippi to SoCal. So, plan was to dry it here but there aren't a lot of sawmills near LA :-) and I haven't been successful finding a kiln. I've shifted now to identifying a vacuum kiln in Arkansas or Mississippi to handle it. The thinking is, they're probably used to drying cypress and know the wood, where as a SoCal outfit might find it to be a hassle. I read the vacuum type is somewhat rare and would like to know how much faster is this type? I keep reading that cypress is supposed to be air dried for about 6 months after it's cut and before kiln drying. One report said it should be kiln-dried to the range of 10-12 percent moisture content and another said moisture contents by weight for 6/4 and above is 13% to 18%. The sawmill is providing the 16-foot planks as a "true 2x6." Before the boards are fixed to the boat they will be planed to 1 5/8" thick so perhaps that will remedy any small degradations from the drying process.

    I appreciate all the responses. These boards are for a ocean-learning vessel built in North Carolina in 1973. It has an interesting history so here's a video if any of you want to hear about it and what we're doing.

    John's EBAC website tip taught me more than I ever wanted to know about drying wood. Thanks!

    This was a good resource too... on cypress grades.

    This thread on another forum talked about the drying schedule but I had a hard time following it.

    Nick

  12. #12
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    There's lumberyard up here in middle California which does urban logging. They mill and dry Monterey Cypress. They might be willing to dry your lumber. https://www.jackelenterprises.com/

  13. #13
    So I still haven't tracked down that spreadsheet I mentioned, but I did find this https://www.woodweb.com/knowledge_ba...s_manual_7.pdf it may all look like greek but the think I found most interesting was the table on the very last page. Basically it says you can take 1" thick cypress from green to dry in anywhere from 10-20 days, so for your 2" stock it will obviously take longer, and this chart doesn't really say much about kiln operation but it should give you a rough idea of whats possible. I don't think the time necessarily doubles from 1" to 2" (maybe depending on species) but I would guess 1.5X length.

    I would look around on that forestry forum for a vacuum kiln I really like that forum, I bet there's at least one or two in central TX that could handle the job, the Houston and Austin areas are loaded with small mills and kiln operators. I hate to recommend but there's always the book of faces. I'm also pretty sure most of the kiln manufacturers will keep a list of their clients so if you contact them directly they can get you in contact with operators. (One semi local to me operator I've seen on fb is these guys
    https://nettdr.wixsite.com/nettlesservices could work out en route from MS to CA)
    Last edited by Nathan Jordan; 12-14-2020 at 11:36 AM.

  14. #14
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    Nick, it’s doubtful that you can dry the cypress in 2 weeks without damaging the wood; rendering it unsuitable for its intended use.

    If I were in your shoes, my first choice would be to locate a commercial kiln in MS that dries 8/4 cypress. A lot of cypress is milled in that state and there should be subject matter experts there for drying.

    IMO at a minimum you are looking at 2-3 months in order to dry it with minimal degrade. I just completed drying a few thousand board feet of 10/4 cypress for some dry saunas and I have 7 months invested in the drying process. The lumber quality turned out great though. It was air dried under cover for the first 4 months and then finished at a slow rate in a solar kiln.

    You will want the wood dried to around 15% MC. If you go below that you’ll need to let it acclimate for a month or so to bring the MC% back up to EMC with an ocean environment.

    Off the top of my head it sounds like you have around 1000 bd ft of lumber to dry. A small Nyle kiln should be able to handle that. I would suggest that they start off very conservatively and at a slow rate for the first few weeks, and then gradually increase the drying rate. Temps in the 90f range and initial RH% in the 90% range for the first 4-5 weeks, then gradually reduce the RH. Temps should not exceed 120f in a DH kiln and only when the lumber is below 25%mc. Keeping the temps down and the RH% high during most of the drying process is critical to having a high quality finished product.

    In General, table 7-30 on page 176 of the Woodweb link that Nathan posted would be a good DH kiln schedule guide to follow.
    Last edited by Scott T Smith; 12-15-2020 at 2:36 AM.

  15. #15
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    Quote Originally Posted by Nathan Jordan View Post
    I don't think the time necessarily doubles from 1" to 2" (maybe depending on species) but I would guess 1.5X length.
    Nathan, the increase in drying time is actually between 2.5x to 3x when comparing 8/4 to 4/4 drying rates.

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