-- Last Updated: Oct-20-12 10:08 PM EST --
..... excellent expansion and contraction properties , which means less chance of developing cracks in changing temperature conditions . Call it "stretchier" if you will .
I like the Varathane spar product better than say the Minwax spar for just that reason .
Not sure about the crystal clear spar Varathane has , so since I don't know how well it handles the expansion/contraction thing (which is what a spar varnish/urethane is all about anyway , plus the UV inhibitors) , I can only advise the standard "Varathane Premium Spar Urethane" , for things like exterior use and marine things like paddles . Besides I prefer the deepening of tone as it ages as opposed to a crystal clear (some call that a slight ambering) .
The Minwax spar seems to have a tendency to chip/crack out much easier , or at least that's my experience (strickly speaking of the "spar" products) .
Varathane has quit a number of finishes for differnt type applications such as floors , furniture , etc ... so don't grab the can because it says "Varathene" brand , It must say "Spar" , either the "Premium" (what I know) or the "Crystal Clear" (on your own there) ... Spar Urethane .
ps., ... 4 coats is correct on new wood , perhaps 2-3 on well sanded previously finished projects .
pss., ... "pure" Tung oil , a minimum of 4-6 coats rubbed out each coat , then the occasional maintnance coat "rubbed" out as desired/needed .
My experience w/Linseed oils is that they are irritant to the skin , causes skin to dry and crack if to much exposure (like handling a paddle grip) .