Keeping a Large Trailer Door From Bowing in Humidity

[lfhoward]

Hi Forum,

It's been a minute since I've been on here! I built my trailer back in 2015/16 and have continuously had an issue with the door. I was wondering if anyone has encountered this kind of thing, and how you solved it.

The door on my trailer is fairly large, like 40" wide. When it rains or the humidity rises, the door bows and becomes concave from the outside, and the lower right corner pulls away from the body between 1/8-1/4". This distance is in addition to the space taken by the foam gasket, so there is literally open space there. That means when I am driving down the road in the rain, it will always leak in this location.

Here's a pic of the inside of the door. The door is stick built with styrofoam insulation sandwiched between 1/4" plywood and aluminum on the outside and 1/4" knotty cedar planks on the inside, all glued and screwed. I don't know if the bowing-out problem would happen if it were plywood on both sides, but the entire interior of the trailer is clad in this knotty cedar and I really don't want to change how it looks. However, if there is a way to stiffen the door so it won't bend in the humidity, I am all ears.

Thanks in advance for your experiences and ideas.
Lauren

 

[Pmullen503]

The door bows because the cedar planks are expanding and contracting with humidity while the outer ply doesn't (or more correctly at a different rate.)

The solution would have been to make the door core the same on both sides (to equalize expansion), and mount the cedar planks so they could expand and contract relative to each other without changing the overall size.

So, not gluing the planks together and securing with nails and/or glue down the center of the plank only. This has to be done at the highest humidity time of the year when the planks are at their fullest width.

 

[lfhoward]

Sounds like a rebuild will be needed if I am going to stabilize the door.

 

[Pmullen503]

If you can strip off the cedar planks, and can handle the extra thickness, you could sheet the inside of the door with the same plywood you used on the outside. (Make sure it's really flat as the glue dries.) Then apply more 1/4 cedar T+G but this time leave some room for the planking to expand and contract. Apply with a bead of adhesive down only the center of each plank and maybe some brads, again down the center only. I don't think you could edge nail the thin cedar but that would be another way to do it: nail only on one edge. Again don't pack the cedar planks too tightly together.

 

[KCStudly]

Another solution could be to stress (or bow) the door slightly in the opposite direction and then truss the latch side of the door with a length of wood or fabricated hand grab. I picture a metal hand grab having at least three pillars or posts, one each at the top and bottom, and one in the middle. If made of wood it could be full dimension attatched on edge, fit with a small swale or concave in the middle so as not to contradict the preload in the edge of the door; and with just finger grooves routed or chiseled into either side to assist in grabbing. By prestressing the door in the opposite direction, when you close it the corners will seal first and the latch will pull the door flat to do the rest.