Cracked Fifth Wheel Trailer Plastic Fender Repair

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Over time I’ve been noticing small cracks appearing on my Keystone Cougar fifth wheel trailers plastic fenders. The cracking is taking place around the screws holding the fenders to the trailer sidewall. It started off with one or two but is slowly progressing to more and more every year. If this kept up and left unchecked, I fear one day I’d lose a fender during travel.

So, I decided this summer to pull the fenders off and see what could be done to beef them up, stop the cracking and prevent a full on failure. A reader recently contacted me via email with some insight to the problem. He believes the cracking might be caused by the indented area for the screws not being flush with the backside. 

At the end of your shelf repair video, you showed a shot of the cracks around the mounting screws for the fenders.
I just removed the fenders from my trailer so I could caulk the steel wheel tubs to the side of the trailer.
Upon reinstallation of the plastic fenders, I noticed that the indents for the screws are not flush with the back side.
If you over tighten the screws it is going to crack the plastic.
There is room enough to put a washer between the fender and the sidewall.
You might be able to epoxy a washer on the back side to reinforce the plastic.
I enjoy your videos.

Showing indent problem and washer solution

Cracked Trailer Fender Repair

I elected to take Arthur’s advice and use some washers on the back side of the fender behind the screw holes. Instead of using epoxy I chose to use SikaFlex 291 sealant. I embedded the washer into the Sikaflex and then applied a healthy layer of it all around the indented plastic area. On the front side of the fender behind each screw, I added a small rubber grommet.

Added washers behind screws

Added SikaFlex around screw indents

Fender Repair and Modifications Completed

Fifth Wheel Trailer Plastic Fender Repair Video

Time will tell, but I believe the repair and modifications made should help extend the life of my fenders and at least prevent a catastrophic failure at speed on a highway. If not, thanks to thunderbird97 on YouTube for pointing me to a website to order up a replacement set.

thunderbird97 – Ray here is a website I ordered my fender skirts in case you need it, , the only difference was old ones were thicker, new ones are made out of better material, holes matched up perfect.  Here is the Canada site

Check out more Love Your RV! Mods, Repairs, and Upgrades in the archives.

How to Fix a Cracked Fifth Wheel Trailer Plastic Fender by the Love Your RV blog -

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