We were double trapped on a screaming reach and the sails started making a humming sound. (kinda cool sound when going that fast as it added to the experience! :D) This was my first time sailing double trapped so I was wondering if it was normal or should I have trimmed the sails differently. Had the jib traveler in towards the center and the sheet tight. The main blocks were within a foot of each other and the traveler centered. The telltails were textbook straight back. The sound was not from the rudders as the tiller was smooth in my hand and it was obvious where the sound was coming from. I did have the downhaul a little loose (on the "10" mark on the sticker) as I forgot to cinch down before we left. I have to relieve the pressure on the downhaul when at the beach or my mast/sail starts to occilate violently while pointed into the wind and the hulls start walking. Also had the battens snug but not tight as recomended for that kind of wind.

Brand new boat right?

Normally I'd ask if the leech of the jib flapping a bit, but yours is new enough it shouldn't be shot yet. That's the usual culprit. My last H16 was a 06', and that summer a buddy and I we're double trapped on a reach haulin' the mail and I got a hum too that definetly wasn't rudder related. Kind of a real low hum?

Yes, that's it exactly. Everything is new and I have installed the cam cleat and cheek block for the aussie jib halyard so the rigging was tight. It could have been the jib but it sounded like it was coming from the main. Maybe I need to tighten the lines that attach the jib to the jib stay?

I honestly have no clue what cause's it. It only happened that one time, and I had the boat set up the same way I always did. So an anomaly of settings, conditions, and boat speed? Either way I wouldn't be concerned with it.

when you're going fast enough the whole rigging will start howling as they get vibrated like big violin/bass/piano wires

on a beachcat it's because you are cutting through the air fast enough to get them oscillating, on the old square riggers it was because you were caught out in hurricane winds...

http://www.google.com/search?q=wind+howling+through+the+rigging&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a