any words of advice/ caution for hammerbeam construction?

  i'm looking primarily the plan as laid out in steve chappell's "a timber framers workshop"
the hammerbeam cape in the back fits my floor plan well enough that i'm thinking of applying it as is, possibly stretching the existing ays or adding another to legnthen the structure.

  the plan is three bays totaling 36ft and is 24 ft deep. i'd like to get to 45 ft long but am still flexible.

any bit of advice or caution helps!

I'm not a timber framer myself, but my buddies are.  I have heard them deride hammer-beam because it uses extra timber, is complicated, and generally desired by clients they don't like.  Economics, techniques and personalities aside,is there a specific reason you are looking at hammer beam as opposed to other patterns?  Hammer beam was developed for churches and barns, where it was necessary for a high open ceiling, is that what you are after?

i think i'm off the hammer beam kick. it's just god awful pretty and the plan in "a timber framer's workshop" had a perfectly shaped loft for our purposes but i think i switched the layout over to a regular high post cape and figured i can lay out the exact same loft there if need be.

funnily enough, i met up with a couple of timber framers a few days ago and their opinions of hammerbeam were indentical to your friends.

Hehe, glad to help.  Good luck with the project.