Mahogany Exterior Door Help?

[Davoud]

I need to build an entry door for a small astronomical observatory that I am constructing in Maryland. The door will be only 32-1/4" wide by

45" tall (as the wood-frame base upon which the telescope dome will rest is only 48" tall).

I would like for it to be a frame-and-panel door (two vertical panels) of solid mahogany.

The problem is that the door exterior will be fully exposed to the sun and elements. It will face southward, getting the sun all day long. Summer-winter temperature changes are fairly extreme in Maryland.

My concerns are water getting into the joints where the panels rest in the grooves and finding a finish that will stand up to the sun. I used a very expensive spar varnish when I refinished an exterior wood door a few years ago and it lasted about a year.

Advice most welcome.

Davoud

[bob]

Seems like you are just asking for deterioration with a frame and panel door under those conditions. Why frame and panel? Why not build a solid door with no grooves/cracks for moisture to sneak in? I'm not sure what finish to use, but something used on wooden boats seems appropriate.

Bob

[Wm Jones]

What brand of spar varnish did you use? UVA Spar Varnish by Pratt&Lambert or McCloskey is highly recommended.

Your error may have been a failure to dilute then progressively concentrate the varnish: first coat is 20% varnish:80% naptha or mineral spirits; second coat is 30% varnish:70% naptha/m.s.; etc until you're at

100% varnish.

Make sure the panels "float." i.e. 1/4" edge of panel into 5/16" slot in stiles and rails...

It will last forever...particularly if you remember to finish the bottom and top horizontal surfaces of the door most especially.