From Knipoch ride south on the A816 to the signposted Easdale on the B844 continue 6.5 km to the very single track bridge that spans a small part of the atlantic on the way to Seil Island continue a further 9km to your destination Easdale where a small ferry can be taken (passanger only ) to the island and a interesting museum to the people of a bygone era also a local brewery.
From Arrochar head west on the A83 then left onto the B828 at the rest and be thankful (bacon butty van) a detour can be taken to Lochgoilhead via the B839 coffee,lunch etc lovely bay views.Backtrack tothe B828 and head through Hells Glento the junction with the A815 where you turn right until you join the A83 and turn left to Inverary.