The /ɑ/ vowel is usually spelled <ar> but we also find <a> in ta and <aa> in baa. Notice how the homograph baas enters into two different pairs, as does the near homograph tours and Tours (the French city). The /ʊə/ diphthong is spelled <oor>, <our>, <ure>, <ewe> in crewel or <ue> in cruel.
This contrast is between a long vowel and a diphthong. The starting tongue positions are fairly well separated and confusions are unlikely.
Interesting pairs include:
The density value is 2.94%. The pairs make 21 semantic contrasts, giving a loading of 54.8%.
ajar adjure baa Boer baas Boers baa boor baas boors baas bourse bar Boer bars Boers bar boor bars boors barn bourne barns bournes guard gourd guards gourds kraal crewel kraals crewels kraal cruel lard lured mar moor marred moored marring mooring mars moors pa poor par poor parr poor parley poorly spar spoor spars spoors ta tour ta Tours tar tour tarred toured tarring touring tars tours tar Tours
Credit: John Higgins