b': PageNo.2 Theshorterlinesshowthestrengthofthefelt.Thelongerlines showthestrengthofacompletebuilt -uproof.Thesefigureswere originallypubl ishedintheMRCAmonthlybulletinofNovember 91961. Itisint erestingtonotethedifferenceofthestrengthof thesebuilt-uproofs,fromal owofabout25lbs.toahighofabout 160lbs.tensilestrength.Theoverallaveragewas103lbs . Thebuilt-uproofsampleswerecutintotwosections.One section,consistingofthecompletebuilt-uproof,wastestedfor itstensilestrength.Theothersectionofeachbuilt-uproofwas degreasedandall tarsandasphaltsremovedfromthefelts.The feltswerethenrunthrought hetestingmachinetogivethetensile strengthofthefeltsinillustration#1. Illustration#2showsthetensilestrengthsofnewfelts gatheredatrandomthroughoutdifferentroofers\'warehousesaround thecountry: IO :.: Sl GT c . "&IHAWlliC: ~:ir.:~ UIISUGIU :r.: :;: \'U! II \' ,o!~l,,~ c uO,un.,rm,J.!" ~::~= , ,un ~. Au 28.3A4JA iao I lft,o,.,.,.~ .,f. u., iA, . ua , IO~Aa u.&.J 01111111111 \', Thesefeltsranfromalowof8.3lbs.perinchtensilestrength a-Ply forasbestostoashighas28.3lbs .perinchforPerm #11. Bearinmindthesetensilestrengthsareforfeltsonly,andnot thecompletebuilt-uproof.Fromnowonthroughtherestofthe discussion,wewillbeconcernedonlywiththetensilestrength ofthecompletedbuilt-uproof,andnotoftheindividualfelts. Atthistimeletusanalyzewhatwehavejustseen .From the1960"GutsofaGoodRoof"program,weknowthatit ispossible forabuilt-uprooftogivegoodservice.Theroofsthatweret urned incamefromtheMidwestareawherewehaveextremesintemperatures. Theseroofscamefromoverwarehouses,officebuildings 9schools , hotels,andthelike.Theyweresmoothroofsandgravelroofs,tar, asphaltandasbestos.Thisisquiteavariety.Yetremember,these roofsdi dnotfail. - - - - - - - - - - - - - - - - - - '