Just varnish has been good enough in my experience with our lugger. We've used, abused, and repaired other bits and bobs, but the spars are fine.

Also, using epoxy on the spars might make maintenance more difficult. You can't epoxy over varnish. So if you get any wear and tear you have to sand everything back to the bare wood and re-apply epoxy then varnish. With varnish only you can do a lot less sanding before touching up the finish.

   Got it. Thanks a ton John. BTW, any recommendations on varnish?

   Always plenty of opinions.  I vote for epoxy coating first, it does add a little harder protection to the surface (anti-dent), but more importantly I think you get less subsequent variation in moisture content within the wood, which equals less dimensional change (expansion/contraction), which equals less liklihood and longer time before ther older, more brittle varnish top coats will micro-crack, which is the point at which (or even before this point) top-coats of varnish should be sanded off, with some newer (more plastic, elastic) coats of varnish added.  The base coats of varnish, having seens less UV and oxygen, will last long time (stay plastic for many years) if top coats are periodically replaced.  And this whole discussion of oxygen and UV and plasticity are why I also vote for keeping things waxed.  I've never had problems with re-finishing.  By the time you do some alcohol wiping and sanding and alcohol wiping during the refinishing process, I never had problems with any wax remaining to interfere with refinishing.

And as to varnish selection, again, many opinions, and many products work well.  The very highest rated marine "varnish" coatings in durability tests are two part systems.  I've never tried them.  Of the many more traditional varnishes I have used, when all said and done considering things like brush-ability, drying time, suitable clarity (I actually like those that tend golden, but not really dark gold), advertised UV protection, etc., I have come to use McCloskey Man-O-War as my go-to varnish.

   And I guess I forgot to mention, I've never gone back to doing a re-epoxy after putting the initial epoxy-then-varnish finishing on anything.  No matter what damage and whether or not the damage went down into bare wood, all subsequent touch up and refinishing I've ever done has been varnish only, so I've never worried about the "epoxy over varnish" issue.

   Thanks @Bubblehead. Much appreciated for the insights and knowledge. :)