Dave,
Your boat was built in South Africa and there are a number of differences with the UK built masts. The mast split is higher up the mast and the jointing piece is meant to be fixed in the top section, but I'm not sure how. It is not a big deal if it is not fixed as long as it not so loose that it could fall out in transportation when you have the mast separated. The jointing piece became fibre glass when the mast went to South Africa. It is hollow and should not leak. It needs to be emptied, dried and sealed. I have never owned a South African 2 piece mast (mine was 1 piece) but I suspect it would not hurt to drill a couple of small holes one at each end to facilitate draining it. You then need to find and mark the source of the leak. Once this is done you could dry the joining piece in the airing cupboard. When dry the joining piece needs to be sealed - both the new holes and the leak site. This can be done with epoxy resin. It might be worth consulting Brian Phipps of Windsport on my suggested procedure before undertaking it.
It sounds like the top section of your mast does not contain water and is OK but the bottom section leaks and contains water. This is the classic leak and is caused by the sealing plug at the top of the bottom section having a slight leak and the rain seeps into the lower mast over time when the mast is upright. Your boat is 10 years old so it has had 10 years for water to creep in. It is normal for the lower section of the mast to take a long time to drain when inverted. Several days is normal - I found they drain best when angled from the vertical.
I have never managed to replace the sealing plug and effect a permanent seal. Once it is drained you have a few options.
1) you can live with it for a period and see how quickly water builds up. It may not happen at a very significant rate and an occasional drain might be adequate. This can be accomplished by putting the mast top down when trailing.
2) you can use the plug and screw technique I talk about in the article.
3) another option is to seal the fibre glass joining piece in the bottom section of the mast using lots of silicone sealant. This will make the lower section of the mast longer than the top section but that does not matter much. It also means that it will be very difficult to remove the joining piece from the mast for any reason.
I suggest that you start by trying option 1 above as it has least downsides.
Regards
Bob
PS Most UK built boats from sail number1200 have an Aluminium extrusion joining piece and it was this I was referring to in my article. The early Sparks had one piece masts but then Panthercraft sold a kit which enabled the owner to cut his own mast in 2 and make it into a 2 piece mast. The kit included a fibreglass joining section like yours. I have the kit instructions for this kit that I will send you if you send me your email address. You can do this by the private messaging facility on this chat page or alternatively send me an email to
technical@sprint15.com