Today's Quilter - UK (2020-05)

in

in

⁄in ⁄in

in

⁄in⁄in =in

in

TECHNICALTIP

Understandingthemaths

ofequilateraltrianglesis

veryusefulif youwantto

designyourownshapes,

ratherthansimply

copyonesyouhaveseen

elsewhere.

Unfinished(UF)sizeofwidthis

in morethanfinished(F)size

Height= side

measurement

3inx 0.866

F size= 2in

UFsize= 3in

ESSENTIAL GUIDE lequilateral triangles

MATHS FACTSFOR EQUILATERALTRIANGLES

Fig 2 Finished size verses unfinished size Fig 3 Triangle with in seam allowance

Weusuallycutshapesfromstripsoffabric,soit’susefultoknowwhatheight(depth)
tocuta strip.Fortrueequilateraltriangles,theheightcanbecalculatedfromthe
widthbymultiplyingthewidthmeasurementby0.866.If you’recuriouswherethis
decimalcomesfrom,it’sactuallythesineof60-degrees.Fromyourschooldaysyou
mayremember(orstruggletoremember,if you’relikeme!)trigonometry,which
dealswiththemathsoftriangles.Sineis a trigonometricfunctionofanangle.The
sineofa specifiedangleis theratioofthelengthofthesidethatis opposite that
angle to the length of the longest side of the triangle (the hypotenuse).

WHY 0.866?
Makingsomebuntingis a great
waytolearnaboutequilateral
triangles.Theresultcanbe
‘rustic’,meaningyoudon’t
havetoaimforperfection,but
justhavefunexploringthe
technique.Buntingis alsoan
excellentwaytouseupfabric
scraps.Forthisbunting,the
triangleswerebackedwithan
unpiecedtriangleandthenhand
sewn to a length of ricrac trim

Beforewegetintodrawingandcutting,it’sworthlookingat themathematical
characteristicsofequilateraltriangles.Rememberingthesefactsis useful:
QTheheightofa trueequilateraltriangleis notthesame as the width, so the
heightis alwaysshorterthanthelengthofoneside.
QTheunfinishedheightcanbecalculatedfromthewidthbymultiplying the
unfinishedwidthmeasurementby0.866(Fig 2 showsanexample).
QAllowingforainseamallowanceallround,anunfinishedtriangle width is
alwaysinbiggerthanthefinishedsize.Fig 3 showswhyit isin.
QWhentrianglesare pieced together, you can calculate the overall unfinished
sizesasfollows:
Unfinishedwidth= addupthefinishedwidthofeachtriangle,thenaddin.
Unfinished height = add up the finished height of each triangle, then add in.