Re: Waterproofing under the oar leathers
In dozens of years with oars, both oiled and varnished I have never had an issue with rot or anything else under the leathers. I have seen oars fail up that were nailed. And what I have had was an oar break under the leathers mostly after lots of use which compressed the grain so that the oar had gone wasp waisted under the leather. Shaping the leather so that you have to work to pull the edges together as Ian notes is critical. Given that a long use spruce oar will compress despite the leather I put some titebond on the underside of the leather.
Ran Tan, Liten Kuhling, Vernon Langille, Josef W., Merry Mouth, Imp, Macavity and a quiver of unamed 'yaks.
"Bound fast is boatless man."