Thanks,
Esty and
Mr.U for the link and the picture. I can't see those daring the "Atlantic" but then apparently the mad Celts sailed west in little corrigals. (And I will use sp? for corrigal as various versions of it canna be found in any online dictionary, nor my handy one, and I can't lug out my OED at the moment. so there

)
The Vikings used a really neat way of slightly overlaping their timbers to improve the water-worthiness of their boats and so I wondered if Tolkien would be precisely detailed enough to work that in.