There are many ways to do this.. And none are wrong... As for 8 foot dinghy with a 12 foot oars, it may looked kindly odd 1) is half the length of boat 2) twice the beam width plus 6 As for the distance between hand grips...Depend on the person.. Myself I like to leave a space about a width of my fist..s for 8 foot dinghy with a 12 foot oars, it may looked kindly odd 1) is half the length of boat 2) twice the beam width plus 6 As for the distance between hand grips... Depend on the person..