I was in that area with a 30'
sloop in 1995-96 and then sailed up to Chiloe. The Beagle is a better route, less tidal, less fetch and more scenic than
Magellan. This being said, unless you venture outside after reaching the end of the Beagle, you will end up transiting some of Magellan anyway, but the western portion of it is more appealing. Occasionally, you get an easterly in Magellan.
I would recommend strong
sails, slab reefing in the main, the ability to carry a proper
storm jib and a serious ground tackle. I was carrying 80m (260') of 10mm chain and a mid-size
CQR on a 4.5-tonne
boat. Unless you can
anchor in front of a stream with shallow
water and sand, I usually found best holding in 18-25m (60-80')of
water throughout Patagonia. Anything shallower and you risk
anchoring on rocks and kelp, even if not visible on the surface. Watch your
depth sounder, you want a smooth bottom.
Unlike the usual trend of tying to trees and mucking around close to the rocky shores, I kept some swinging room and just anchored very seriously. Short-handed, messing with
dinghy, lines and anchors is asking for trouble and there was no need for that. Also I wouldn't trust the holding of the
anchor unless it is set in a good bottom and that was a good reason for not going in shallow water, unless there was an alluvial bottom at hand.
Eric