ʻOiai he ʻano "C" nā mea ʻelua, ʻokoʻa loa ko lākou mau kikoʻī ʻokiʻoki a me nā ikaika o ke kūkulu ʻana, kahi e hoʻopilikia pololei ai i ko lākou hiki ke amo i nā ukana a me nā laulā o ka noi.
ʻO ka ʻāpana kea o ke kahawai C heʻōnaehana hoʻohui wela i ʻōwili ʻia. He mānoanoa kona pūnaewele (ka ʻāpana kū pololei o ka "C") (maʻamau he 6mm - 16mm), a he ākea nā flanges (nā ʻaoʻao ʻelua moe) a he ʻano piʻo ko lākou (e hoʻomaʻamaʻa i ka hana ʻōwili wela). Hana kēia hoʻolālā i ka ʻāpana kea i ke kūpaʻa kūlou ikaika a me ka paʻakikī torsional. No ka laʻana, he 10# C Channel (me ke kiʻekiʻe o 100mm) he 5.3mm ka mānoanoa o ka pūnaewele a he 48mm ka laulā o ka flange, hiki ke halihali maʻalahi i ke kaumaha o nā papahele a i ʻole nā paia i loko o ka hale nui.
Ma ka ʻaoʻao ʻē aʻe, ua hana ʻia ʻo C Purlin e ke kulou anu ʻana o nā papa kila lahilahi. ʻOi aku ka "lahilahi" o kona ʻāpana kea: ʻo ka mānoanoa o ka pūnaewele he 1.5mm - 4mm wale nō, a he haiki nā flanges a he pinepine nā pelu liʻiliʻi (i kapa ʻia ʻo "nā iwi hoʻoikaika") ma nā kihi. Ua hoʻolālā ʻia kēia mau iwi hoʻoikaika e hoʻomaikaʻi i ke kūpaʻa kūloko o nā flanges lahilahi a pale i ka deformation ma lalo o nā ukana liʻiliʻi. Eia naʻe, ma muli o ka mea lahilahi, nāwaliwali ke kū'ē torsional holoʻokoʻa o C Purlin. No ka laʻana, ʻo kahi C160 × 60 × 20 × 2.5 C Purlin maʻamau (kiʻekiʻe × laulā flange × kiʻekiʻe pūnaewele × mānoanoa) he kaumaha holoʻokoʻa ma kahi o 5.5kg no ka mika, ʻoi aku ka māmā ma mua o ka 10 # C Channel (ma kahi o 12.7kg no ka mika).