Thanks for answering. I am only going to paint if I totally mess up this wood. I reallllllllllllllyyyyyyyy love the natural look so I appreciate help.
For a clear finish outdoors use a sealer coat or two same as I mentioned before... and sand off all the nubbies between coats. You can use your topcoat thinned 50% for a sealer just fine. Or, you can still use clear shellac for a sealer (just use non-pigmented, of course), this is faster because it dries quick enough you can prolly apply three coats in a day... Not so with spar varnish... it dries pretty slow.
You want to use the best quality marine spar varnish you can afford. Minwax Helmsman is OK, but is not a great product for long term outdoor exposure. The better marine varnishes prolly cost upwards of $80. a gallon! But, they do last longer & have better UV inhibitors... Ya kinda get what ya pay for with this stuff.
Some folks like to seal their wood with epoxy, like boat builders do... Then topcoat with spar varnish for the UV protection it offers. Costs a bit more, but is a very good way to go too.
Main thing to remember is NOT to use any kind of "Poly" as in polyurithane varnish... None of them will hold up outdoors!
As for your seam or joint... May be a little late now? But it is prolly best to use epoxy (and fiberglas tape?) to make the joint. You can mix some filler like micro-beads to make a putty to fill voids with too. Of course, one of the reasons a lotta guys put a "woodie" kind of trim on their trailers is you can cover up the joints with trim... I like that look anyway, so that's what I'm gonna do to my tear...
I use Mas Epoxy because I can get it for less than West System & others...
http://www.masepoxies.com/mas11.htm
PS: If you want a good spray gun for the money... This HVLP gun from Harbor Freight is a good one. I have three of them! I know a bunch of woodworkers and hot-rod builders that use this gun, it just won't last as long as a 3 or 4 hundred dollar Pro gun like for daily pruduction. They are often on sale for $49.95... I got two a while back for $39.95... I guess those days are gone tho...
http://www.harborfreight.com/cpi/ctaf/d ... mber=43430
Friend ~ Brick