On the other hands, Craven probably didn't knew about the level of "Stonewall" protection, and assumed that her armor at least as durable as on other southern ironclads. He may assume that his guns didn't have enough penetration power to smash through the "Stonewall" plating on the big distanse, and if he closed with the enemy, his long and not very agile frigate might be rammed by "Stonewall".
I did a bit of digging into this near-action, partly because of a magazine article I was writing (which was rejected, alas) and also in connection with my bio of Henry Walke (who was skippering the
Sacramento at Ferrol). It appears that the basic battle plan that Craven and Walke had drawn up was to get
Stonewall out into incontestably neutral water deep enough for the
Niagara (the deepest-drawing vessel of the three) on a day when the sea was a little rough-- it had been observed that the shape of
Stonewall's bow limited its forward speed in those conditions (and also hampered the use of the 300-pounder forward gun). Craven and the
Niagara would draw the ironclad's attention, and Walke's
Sacramento would flank her on the rear quarter, ramming if there was an opportunity.
Captain Thomas Jefferson Page of the
Stonewall appears to have been fully aware of the disadvantage rough water placed his ship under, and himself declined combat on two occasions; on the third, when the sea was abnormally smooth, he was more aggressive and the Union officers correspondingly more cautious.
I do not have a good read on what Walke felt about Craven's decision not to engage. He loyally supported his superior in his testimony-- but there are a couple of clues that say to me that, had their positions been reversed, Walke might have acted more aggressively (one of which was a rebuke from Craven for getting too far ahead of the
Niagara in an attempt to close with the
Stonewall in the first of the three encounters).