Best finish for a Restored Truck Bed? (Red Oak)

[Dennis Hatchett]

I've agreed to mill some 6/4 Red Oak that will be the planking for a restored 1940 flatbed military truck. It will not be a show truck but, of course, he is interested in a classic solid appearance which is why he is going with the thick clear red oak. If you are wondering why not white oak as I suggested to him, he simply had the red oak supplied to him.

My question is regarding the best finish for a utility vehicle that will be lightly used as a towing rig for his RV's. He will keep the truck garaged when not in use so the exposure to the elements will not be constant. He lives in the high desert of Central Oregon which is a very dry climate.

I suspect that a good finish would be the oil/varnish mixture 2 to 1. I've used a Boiled linsead Oil and varnish combination in the past and it seems to be satisfactory for some outdoor applications though it needs some regular maintenance. Another one I came across in the finishing forum is 1/3 Boiled Linseed Oil, 1/3 tongue oil, and 1/3 varnish.

Is there any treatment that will aid in UV protection? What's your secret recipe? And if it is a varnish/oil mixture what specific varnish do you suggest?

Thanks for your input.

[Steve Schoene]

STOP You do not want to use red oak for this--expect it to rot away in a couple of years. Red oak has pores that extend essentially the full length of the boards. It can get wet, wick water through the board and begin a process of rotting from the inside out, even though it seems dry on the outside. White oak is the wood for truck beds. It's pores are blocked so water doesn't penetrate to where it doesn't dry out. White oak is a very good exterior wood standing up to water and weather exposure quite well.

No secret for UV protection. For show wood such as yacht brightwork coatings of 6 or more coats of the best quality marine spar varnishes are best, but this would not be a good thing for a working surface of a truck bed. Once the film is breached deterioration can be rapid.

Oil/varnish mixes are probably as good as you can do. UV protection in these,even though claimed by some makers isn't very meaningful since no thickness can be built. Oil/varnish mixes must be vigorously wiped off the surfaces so there is no film accumulation. It maintain the look, I recommend a refresher coat of the oil/varnish mix about every year, given dry indoor storage for most of the time. If you were in a wetter clime, I'd avoid using BLO in the mix since mildew seems to thrive on it. It probably doesn't matter in your location. If the truck were parked outside almost monthly refresher coats would likely be needed to avoid having the wood grey.

For that matter, letting the white oak turn its natural silver grey color isn't a bad thing. Keep the show surfaces varnished and let the bed turn grey.

The varnish chosen is not particularly important, though traditional resin varnishes with phenolic resins would have some slight advantages. Polyurethane varnishes would have a slight disadvantage due to its UV sensitivity. Tung oil isn't as attractive to mildew, but adds significantly to drying time between coats. Instead of overnight, think several days between coats.