[How to "unify" a series of curves?]

I have made a pencil in affinity from a series of curves/lines now that I am done I would like to make the pencil entirely one shape. Whenever I select the nodes and use the "Join curves" tool, The curves become one shape except that some lines are created that sort of close the shape or connect them in a weird way. I have added the images for a better understanding of what I mean. How do I stop this from happening? Thanks.