Gravel Guard

Newly installed "Gravel Guard"

Truthfully I don't know what this rubber overlay was originally called, but I read a post where someone called it a "gravel guard" so I'm taking that as an authoritative source.

It's basically an 18" tall rubber mat that runs the width of the trailer starting at the interface with the frame. It overlays the front-most lower part of the aluminum skin. It's about 1/8" thick and looks for all intents and purposes exactly the same as a thin-ribbed corrugated rubber floor mat; the kind that you might find in a wet area of a commercial kitchen to provide traction.

I believe the gravel guard on the trailer was original. It was a crumbling mess. Just touching it would deposit a black smear on your finger.

Gravel guard before replacement

The guard is held on by some narrow aluminum coving that is predrilled about every 1.5". It was screwed through the rubber into the sheet aluminum with 1/2" sheet metal screws. The screws had deposited rust stains on the aluminum and the excess holes collected dirt and insects over the years, so I cleaned them up using a dremel tool with a very fine grit sanding sponge. Also, the rubber didn't seem to be glued on, but there were a few spot where it seemed to have adhered to the aluminum skin so I needed to scrap those spots off. Otherwise the rubber just peeled on in pieces or crumbled away.

I ordered replacement corrugated rubber from Amazon but it's widely available including at Home Depot, etc. It was simply a 1/8" thick 3' wide x 8' long fine-ribbed corrugated rubber mat. I cut it lengthwise down the middle to get an 18" width and then trimmed one end to get the roughly 6.5' length.

I prepared the aluminum coving with some Sikaflex sealant to plug the extra predrilled holes so that water, dirt and bugs would be discouraged. I also dabbed Sikaflex on each of the exterior screw holes that would be under the replacement rubber. Then I started at the top and attached the long horizontal piece with new #6 3/8" stainless A point sheet (not self tapping) metal screws. Then I moved to the two inner vertical strips. This was a pain because I wanted to reuse the holes that were already there and with the rubber in place you can't see the hole in the aluminum you're trying to thread into. Much cursing later I finished the install.

I will likely go back and redo the lower aluminum strips because the rubber is looking to have stretched out a little in the warmish desert Fall days. I'd guess you could avoid this by cutting the mat a bit wide and tensioning it as you installed the vertical pieces. On reflection it did appear that the rubber had been trimmed after the bottom horizontal strips were in place. They probably pulled on it as they went along sort of like carpet installers.

I got some alternative ideas for replacement material from the Boles Facebook groups: a sheet of black ABS; black paint (does 2024T3 aluminum really need a gravel guard?); and truck bed liner sprayed on. One person suggested that if I was really worried about gravel (I'm not) I could rivet on another overlayment of aluminum sheet. All good ideas and I might consider them if this rubber mat decays quickly or becomes an issue in another way.

One final note. I was not sure if the gravel guard was original or a feature added by a previous owner. I'd seen them on a lot of 40's Boles but there were also some picture without them. I though maybe it was a dealer option or something. I was told by one authoritative source that no trailer from the 40's had a gravel guard. So I wasn't sure. But then I received a picture of a 1946/47 Boles Aero flyer from the daughter of Don Boles. It clearly shows both trailers with gravel guards. So maybe it was a factory option.