Hi Ian,
Daiku gives you good advice to design your bents with good outward thrust resistance, however having just spent a pleasant afternoon with my wife listening to the choir practice in Pilgrims Hall, Winchester (circa 1300 - 1309) my eyes cannot confirm Steve Chappell's recommendations.
This hammer beam hall has stone (flint) walls built with buttresses of dressed ashlar limestone at the hammer post locations. The main cross frame (bent) braces spring from the centre of the arcade tie beam (collar) and join with the hammer post a matter of six inches or so above the canted hammer beam. The design employs massive timbers to help resist the excessive deflections to which hammer beam roofs are prone.
There is a small drawing of this roof frame in a new book - Hampshire Houses by Edward Roberts just published by Hampshire County Council - (ISBN 1 85975 633 6 price £19.95).
Given that you live in California you have the added complication of earthquakes to take into consideration and therefore I would strongly recommend that you engage someone to run some numbers on your design prior to committing to a cutting programme and this will confirm Daiku's recommendation - big posts !
Please feel free to email me a typical cross section of your proposed bent for comment.
Regards
Ken Hume
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