There is a limit to the length of an aluminum extrusion so joints are common. You will usually find a joint at the partners or spreaders because the mast is more in compression then bending at those places. A joint doesnít always mean a change or repair was made it may only indicate that the section used for your boat came standard in a length that needed a piece spliced in to be long enough for your mast. Properly done a splice isnít any reason for concern.
All the best,
Study the history of naval architecture and move forward knowing what didnít work before.
Donít waste time making the same old mistakes but instead make new ones and to insure your place in history be sure the mistakes are big ones.
Never design a mast that is weaker then the boat
Never design a boat that is weaker then the mast
Never listen to someone describe why your project will not work unless they can show you the broken pieces of their own version.