I have a canal 16 feet across. I want to put a 4 foot wide bridge over it using 2 beams spread 3 ft. What size beams are needed. Load = 700?

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answers:
oldschool say: Bridge design on yahoo answers? 700lbs? 16ft is a little long without some support midway. The stronger the beams, the heavier they are. Maybe two pine tree trunks properly anchored at both ends
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Maybe it's just me say: 700, huh? 4 foot wide bridge with 2 beams 3 feet apart. 700 what by that way?
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Joseph say: And are the beams made of high strength steel or Swiss cheese? It does make a difference, you know.
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expert say: Ummmmmmmmmmmmmmmmmmmm
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Ronald 7 say: 20 inches would do the job
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