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Thread: trailer boards

  1. #1
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    Mar 2015
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    trailer boards

    On my 20 ft dovetail trailer I am kinda tired of using pressure treated pine just to have it break at a knot when loading something heavy. I was thinking about cutting some oak for the floor, my question is what can I use for a rot preventive , I have seen copper sulfate but they suggest soaking anything about 2 inches thick, well I need to cut at 16 ft. do not have desire to make a trough and fill with copper sulfate at what a cost. Do you guys got any ideas. I want to stay away from paint , to slippery, but I guess I could add sand to it. thanks Dave

  2. #2
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    Good quality white oak is fairly rot resistant...
    Put 2 coats of water seal of some type on ALL FOUR sides before installing..
    It will last for years if the wood was air dried to 12-15 percent before coating.
    Be sure to allow it to soak into wood, especially the sides and bottom.

  3. #3
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    Pulled a lot of medium weight stuff on a trainer with white oak boards. I'm on the weather friendly left coast but still, I think we replaced one board in many years.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  4. #4
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    For trailer decking, if you plan to treat the lumber with an oil based preservative red oak is a better choice than white oak. The reason why is that the open pores in red oak allow the preservative to penetrate deeper into the lumber.

    The tyloses in white oak pores prevent most preservatives from going more than 1/16 to 1/8" deep into the lumber. If you do choose to treat white oak, if you wait 9 months or so after installation before applying the preservative, it will soak in deeper.

    In terms of preservatives, one of the best that a lay person can buy is copper napnathanate (CuNap). A lot of the pole treatment products sold at farm and ranch supply stores use it as their base ingrediant.

    If you want to use a recycled product, used automatic transmission fluid soaked into the boards well in advance of installation works better than engine oil, and is much less nasty in terms of the surface.

    If you are going to fully dry the boards before installation, plan on some losses due to wood movement.

  5. #5
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    Dave, Going to Oak will mean you can use thinner material but it's going to cost more and be a little harder to source. Also Oak will develop thousands of small checks in the sun so it will benefit from repeated treatment.

    You might benefit from better quality pressure treated Pine (less knots)

    A lot depends on how you keep your trailer. If you keep it in a rot inducing condition (full of 10 year old firewood) wood might not be the best choice.

    Scott, The closed tyloses in White Oak make it rot resistant. Not sure what the tradeoff would be using Red Oak well treated.

  6. #6
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    Quote Originally Posted by Tom Bender View Post
    Dave, Going to Oak will mean you can use thinner material but it's going to cost more and be a little harder to source. Also Oak will develop thousands of small checks in the sun so it will benefit from repeated treatment.

    You might benefit from better quality pressure treated Pine (less knots)

    A lot depends on how you keep your trailer. If you keep it in a rot inducing condition (full of 10 year old firewood) wood might not be the best choice.

    Scott, The closed tyloses in White Oak make it rot resistant. Not sure what the tradeoff would be using Red Oak well treated.
    Tom, we did some experiments several years ago with trailer decking here at the sawmill and determined that treated RO outlasted untreated WO. The key is renewing the treatment every year or so. We tried several different things and had the best results with CuNap mixed with diesel, or used automatic transmission fluid. We saturated all sides of the dry lumber and subsequently only retreated the top surface.

    The other thing that is important is to use lumber that doesn’t have any sapwood present, as it will rot more quickly - treated or not.

    While the tyloses are responsible for the rot resistance in *most* species of white oak, they also prevent preservatives from penetrating deeply into the wood. Hence my recommendation. As you probably know, chestnut white oak does not have tyloses present and is not rot resistant. It sure makes pretty quartersawn though!

    Very good advice re the pt pine. It weighs less than Oak too thus increasing net trailer capacity. The key thing here is to use ground contact rated material for maximum longevity.
    Last edited by Scott T Smith; 10-01-2020 at 10:05 AM.

  7. #7
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    Up here in NY people often use hemlock or larch (call Tamarack in some locales) to redeck trailers. Both are pretty low cost and come in long, clear lengths. Treated, both last a good long time.

    John

  8. #8
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    Mar 2015
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    cleveland,tn.
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    I have a lot of red oak here that is dying so wood is not a issue , and I will cut it to dimensional size , yes it will weigh more than pine but I would think max. 400 lbs difference it is a 6 ton trailer so what I put on it I believe I got wiggle room. And I keep it under cover so uv and water damage should be kept at a min. Now it is just finding the time to do it.

  9. #9
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    Cyprus is another good outdoor wood.

  10. #10
    I have no idea if it works, but old timers around here swear by used motor oil on the hay wagon decks and trailer decks. And they specify, USED. Seems like it has to be wrong to me, but I am no specialist on the matter. I have to say the 1 inch oak hay wagon deck lasted a good 14 years after I bought it used and before I had to replace the deck. I gave it the used oil every other year.

  11. #11
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    oil does work, I have heard to cut it with some diesel fuel so it soaks in easier ,as far as the cypress goes it is stronger than pine but not as much as oak and that would be great if I could hit the lottery to afford 2x8x16 enough to do the trailer, I remember when I lived in Fla. cypress was not that pricy . But they have cut so much of the old growth cypress years ago prices are high last I knew. I think now the cypress knees are protected in some areas.

  12. #12
    Yellow pine and pick boards with out knots i have treated on my trailer for years and never had a problem i dont know why you drop stuff but being a bit more careful helps

  13. #13
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    Feb 2003
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    Hayes, Virginia
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    Once upon a time I purchased green five quarter white oak from a local mill for my trailer deck. Lasted over 20 years without any maintenance.

  14. #14
    Join Date
    Jan 2019
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    Fairbanks AK
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    I have seen "trailer board" in a lumber grading guide. I don't remember if I saw it in the WWPA or NELMA books (western and northeastern) respectively, but now I am curious. I will look it up over the weekend if I can, probably specs for knot size, grain runout and thickness. Curious to also know the intended trailer that needs graded flooring, maybe tractor trailers subject to DOT.

    EDIT And I couldn't find it (trailer) in either of WWPA or NELMA grading guides, I did find scaffold grade in the WWPA book. I remember I saw a snippet of the SLMA grading guide online, might have been in there, I haven't bought a copy. As you have already noticed, PT pine, probably Southern yellow in your area, breaks at the knots. SYP (in general) is a fabulous as softwoods go, comparable to Doug Fir and tamarack and larch. If you can find clear SYP that is already PT that could/should work for you.

    If you got oak trees dying and a sawyer I would probably be inclined to go that way. I have heard of USED motor oil cut with diesel a few times myself, never actually done it.

    Can you talk a little about the loads you expect the trailer to carry and how far apart the floor supports are? Is there maybe a thicker cross piece in the undercarriage so you could use some 10 foot boards for the decking? I am starting a week of staycation tonight, some straightforward beam problems would be a welcome respite from the usual drudgery of my day job.

    The other important question is what exactly PT pine is meeting your needs except for breaking at the knots. The design values (fiber stress in bending and modulus of elasticity and so on) vary between grades. In general the drop off from select structural to grade one to grade two isn't too steep, and in general those values fall off a cliff when you start talking about grade 3. Most likely it sounds to me like your existing decking is grade #1 or grade #2 PT SYP construction lumber 2x6-8-10, yes?

    Do you have 20' lengths of clear (knot free) southern mixed oak standing on the stump? Knots are problem grading oaks too, and I am inclined to agree with other Scott down your way sapwood can be a rot issue.
    Last edited by Scott Winners; 02-13-2021 at 3:45 AM.

  15. #15
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    Hi Scott
    Here's a question for your spare time.

    If the supports are 4 ft apart but I install a crosswise cleat underneath fastened to the boards, how does that help? My thought is that it helps a lot with point loads but not at all for a distributed load. Is that right?

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