Hi thanks fir your post.i have an outback 28krs with same slide out rails problem.does anybody know if there is steel support bar running the length of the rail or wood?wondering if I can put more screws in
Mine developed cracks at the end fastener in the rails. I noticed it after going over some tall speed bumps in a parking lot. I extended the rear slide and removed one of the screws to see what it looked like. With the slide out, the rail isn't taking any load at the front end so taking the screw out wasn't a problem. They are square drive truss head cabinet screws. I was able to find the same screws but in zinc finish I just can't remember where. Probably Tacoma Screw or Fastenal.
After doing a bunch of searching, I found pictures of a partially completed outback with a rear slide that showed what looks like 2x6 pieces between the roof trusses at the slide rail locations that the rails are screwed to. In the stowed position, the rollers for the slide out sit between the two factory installed screws. When the slide out bounces, the rail flexes trying to go from straight to a U between the two screws. This flexing causes the cracks.
I'm a structural engineer and I work on repairs for large commercial airplanes. I see stuff like this every day at work. I drilled extra holes through the rails into the 2x6s and installed extra screws with fender washers that were the largest I could fit in the rails. The washers were thin enough to not interfere with the rollers. I also trimmed washers to fit over the end fasteners to spread the load when the rails had already cracked. With the washers in place, the rail won't flex and won't crack down the center. The load is pushed out to the flanges and away from the center of the rail. Also the load is now taken straight into the ceiling through the new screws in place of having to travel each way to get to the ceiling through the factory screws. Because of this, the rail doesn't bend anymore. I haven't had any problems since I did this repair.
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