Spacing of scarf joints relative to butt joints

[GeoffNZ]

Hi.
I have had to replace a couple of sections of planks one above the other. Top plank is in with butt blocks at the ends. I will need to remove a larger section of the lower plank to space the joints appropriately. I know it 3 frame spaces if I use butt joints again but what if I use scarf joints is there an appropriate distance from the butt joint above. If there is an appropriate spacing where on a scarf joint do you measure from. Near end, far end, middle of it.
The plank in question is midship just below the waterline. 26 ft 1964 british folkboat carvel planked and partly wedged at some point in her history -if not when built.
Thanks for any guidance
Cheers Geoff

 

[Hacker]

We space scarfs using the same rule for butts. Middle would be fine. Just remember to cut the scarf direction to avoid presenting the opening of the joint to the water flow.