I agree with RumbaRue, forget the bamboo. What you want is landscaping poles used to stake large trees. These poles are made from hardwood and come in very long lengths. You simply cut the pole to the desired length. These can be had at any Home Improvement store along with the canvas for the sides and roof.
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Don't reinvent the wheel. There is period equipment all around you, you just have to look at with a different set of eyes. Boats is one of the best encampment designers around and RumbaRue is also a great resource for what to use for encampments.
Rumba, in your opinion, besides painters canvas, landscaping poles, and dowels, can you think of anything else that would be needed for the structure only?