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Thread: My first post and first problem

  1. #1

    My first post and first problem

    Good morning,
    As the title states, this is my first post on this forum. I've been following it for some time and really enjoy reading all the help that is provided by the people that know whats going on.

    Now, my problem. I live on a lake in Virginia. I have been asked to build 4 kayak racks holding 6 kayaks (3 on each side). I plan on using 6X6X8 pressure treated lumber for posts (about 2 1/2 to 3 feet in the ground).
    Then I plan to half lap pressure treated 4X4 posts to use as the kayak support. Probably going to cut a gusset to help support the 4X4 to the 6X6.

    My concern is shrinkage. If I cut the half lap (on the 6X6) 3 1/2 inches to accomodate the 4X4 and then cut the half lap (on the 4X4) 5 1/2 inches to fit the 6X6, I should have a pretty close fit...which of course, is what I want. "BUT", what I'm worried about is 3 or 6 months down the road when "everything" has shrunk. I would venture to say that I will be looking at 1/4 inch sloppy gaps at all my joints.

    I have gone to 2 places to shop for the required lumber. Looked at "KDAT" (kiln dried after treatment) and I found it to be just as wet as regular PT lumber.

    Sure would like any ideas, thoughts or suggestions.

  2. #2
    Join Date
    Jan 2016
    Longmont, CO
    kdat i have used is the same as you describe, infact my cheap menards lumber, which i have to drive some distance to aquire, shrunk less than the expensive kdat from a local yard i got to finish the project. go figure....

    kayaks weigh maybe 50 lbs? i would get the lumber as early as possible and sticker it, i did this for my new car trailer deck, stickered and strapped down to the trailer for a month and i really think it helped with warping. I have done similar in the past as well.

    i would half lap the joints as you describe and use timber lock screws to hold everything together. I do not think the shrinkage will effect the usability or strength in a meaningful way of the rack. could you through bore a hole for the 4x4 in the 6x6? as both shrink, the gap should not get too much bigger this way? could be a fun and interesting way to build them as well.

  3. #3
    Join Date
    Sep 2006
    Deep South
    Your choice of lumber size seems like huge overkill to me. Kayaks weigh less than a hundred pounds but your proposed structure will support thousands of pounds per boat if I understand what you are proposing to do.

    You aren't going to be able to get away from shrinkage and swelling if you build your racks out of wood. That is the nature of the material. I think you are overestimating the severity of the problem.

  4. #4
    Join Date
    Feb 2016
    Honolulu, HI
    If you're worried about shrinkage, then just forgo the joinery. A couple 2x4 bolted through or lagged into the sides should be enough to hold kayaks, and if it gets damaged it would be easy to repair. Something like this..


  5. #5
    Join Date
    Aug 2019
    Could just mortise a 2x4 right through the post and put a slightly longer 5/4 cap on each side. Round all the ends.......just spitballing

  6. #6
    I would do as Steve suggests and make a through-mortise, as I have a chain mortiser that makes it quick and easy.

    Without the mortiser, I would follow Randy's advice and bolt a 2 x 4 to each side of the post.

  7. #7
    Quote Originally Posted by Randy Viellenave View Post
    If you're worried about shrinkage, then just forgo the joinery. A couple 2x4 bolted through or lagged into the sides should be enough to hold kayaks, and if it gets damaged it would be easy to repair. Something like this..

    The way I would do it. 1/2" through bolts.

  8. #8
    Join Date
    Feb 2014
    Lake Gaston, Henrico, NC
    You're right. The horizontal pieces will shrink more than their mates in the vertical 6x's. I would just bolt them, and then in 6, or 7 years, when the 6x's have dried out, partial lap joint them if you still think it's worth the trouble.

    Which lake?

  9. #9
    I try to use treated lumber before it dries. When you use it the soaking wet (the way it comes from the yard), it will dry in the shape that you have assembled it. If you let it dry before using it, it will assume whatever pretzel shape it wants. I have learned this the hard way. Plus screws are much less likely to split when the wood is still wet.

    Make sure whatever hardware you use is rated for contact with treated wood. Hot dip galvinized, stainless, triple coated, etc is a must. Zinc plated bolts will not cut it, nor will standard construction screws.

    If you are able to tighten your hardware after the wood dries, you should be fine.

    No need to fiddle with half laps or fancy joinery. It's a Kayak rack, not a jewelry box Plus treated doesn't tend to machine well or hold fine detail.

    2x4s or 2x6s bolted cross beams like shown above are the way to go. The main thought for the 2x6 arms are to space the bolts out more to resist racking when only one side is loaded. Plus treated 2x6s tend to be better quality than 2x4s, which for some reason frequently seem to be cut through the center of a 4" wide log.

  10. #10
    As I mentioned, this was my first post.
    I would like to thank the people that took the time to offer ideas and advice. I think that I'm going to like it here.


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