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  1. #1
    Left The Driveway
    Join Date
    Jun 2020
    Location
    North West Arkansas
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    Angry 31MB Bottom Bunk Structural Failure

    Hi everyone, new to Grand Design, this is my first post. We purchased our 31MB about a month ago and overall love it, the mid-bunk is perfect for our family. However, the structural design of the lower bunk is terrible and is a failure point. I found this out when I sat on the edge of the bunk to set up the TV I installed. When I sat down, I heard a cracking sound, not something you want to hear from furniture. Upon investigation, I found movement in the bed frame and staples popped on the side.

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    I removed the plywood to take a look and was not happy with how this bunk is built. There was no physical connection between the top and bottom support rails at the front of the bunk. There was a piece of wood at the corner but its only purpose was to provide for stapling on the lauan. This left the front of the bunk unsupported causing the staples to pop out.

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    Beside this, the design of the bunk has a couple other issues. The cross beam supports are only stapled to the front and rear supports (weak connection) and there is no support in the center of the cross beams. On a positive note, there is a lot of unused space under the bunk that could be used if you were to modify this area. The fix for all of this was pretty simple. I added a piece of 3/4" plywood at the front corners for support (highly recommend doing this at minimum). I added a pocket screw to all the cross braces for strength, and add support in the center of the cross beams. All in all pretty simple to do if you have a Kregg pocket hole jig and a small bit of carpentry know how (only took a couple of hours).

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    I know they build these units pretty fast but this was a design flaw leading to a failure.

  2. #2
    Big Traveler
    Join Date
    Jan 2018
    Location
    NorCal
    Posts
    1,457
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    You'd be surprised to know how much of this trailer is just held together with staples. It's scary. Nice work with the Kregg jig. That's the right way to do it.
    2017 Ford F450 - our kids call her "Big Red"
    2018 Grand Design Reflection 28bh

  3. #3
    Fireside Member
    Join Date
    Sep 2020
    Location
    Central Ca
    Posts
    67
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    Thanks for the pictures/retrofit idea. Wife saw another retrofit on FB, but was doubling the joists and adding some blocking cross members. Didn't love FB idea structurally and your idea makes better use of what was already there with less material. I did end up adding some front plywood strips also screwed into the front section and the 2x2 joists at this point in time (don't love this long term but didn't want to tear further into the front ledger and cabinet finish face at this point). Will see how this works out after a first few trips but future mods may be thicker sheet of plywood and probably some more retrofit at the front and back ledger condition (needs to work around front drawer layout).

    2020 GMC 3500 Denali SRW SB Duramax 4x4
    2021 Reflection 31MB Goosebox 16k

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