Hey Paul G. - I meant to add (I'll put it at the top) - your boat does look beautiful, you should feel proud - and I bet you are loving the sail too!
Marcus
The prize for “suggestion of the week” should be duly awarded to Len. I don’t agree with making do with a 9m above partners mast (unless you opt for a 2-masted rig) – I think you would regret it. However, Len’s brilliant afterthought suggestion of a tabernacle could well give you an extra 2m of mast height. If you look at Annie’s blog, you will see that she installed a tabernacle, arranged so that the heel of the mast is at deck level. The lower tabernacle, which will extend down to the keel, can be regarded as a lower mast extension. It won’t help in any way with interior accommodation – but it does give you some extra mast height. The advantage Annie sought was not needing to have a hole in the deck to keep watertight, as the mast is entirely above deck. I would consider forgoing this advantage in order to sink the mast a little deeper, ie get a little extra “bury”, as I will explain in a minute – but if all the rest of the engineering is sound, it’s a matter you can decide for yourself. (I am planning a "sunk tabernacle" for my own project, to allow a tallish mast - and a "secret weapon" which has been brewing in my mind ever since I put a sunk tabernacle into my little trailer boat.) A tabernacle extending 1 m above deck looks a little prominent on paper, but when you look at the beautiful Fanshi, you can put any concerns about that aside.
Now, from an engineering point of view (and I am assuming the specs of your two tubes pass muster, you can check those details anyway) an 11 metre mast in a 1 metre tabernacle meets the “10% bury” rule – just – with nothing to spare. So that gets you to 11m “above partners” with the tack of the sail a little higher than 1m. That gives plenty of room for parrel-downhaul spans if you follow Slieve’s system – and it also allows plenty of height at the aft end for sheeting. The only problem is, its still not enough height at the mast head to give you the full area of sail you should carry.
Why not (if the aluminium tube specs allow it) add an extra 3 m to the top of the mast, in the form of a wood, aluminium tube or carbon fibre, or glass fibre extension? Give the mast an extra 0.5m bury into the tabernacle (in which case you lose the advantage of a 100% sealed deck) and put on a decent sail, along the lines suggested by Slieve – or any other you like – and aim to match at least the working sail area you had before. This would give you a 1.5m bury and a 13.5m LAP (length above partners) mast.
Edit: You could optimise those numbers a smidgeon and reduce the length of topmast extension by a few cm if you want to go to exactly 10% bury - and as David has pointed out while I was writing this - you can squeeze another 0.4m from your two 6m tubes as well - this further reduces the length of the suggested topmast extension, down to 2.5m perhaps, or thereabouts.
Or, if you want to stay 100% above deck, scale down the top mast extension, raise the tabernacle slightly, and see how much you can get, allowing 10% bury – I think you might still squeeze in with 13m LAP and a 1.3m above deck tabernacle – and a slightly reduced potential sail area. Again, slightly better than that actually, following David's suggestion. You might need something like that anyway, to clear the deckhouse, depending on how much rise of batten you eventually decide on and where the sheeting goes - without a drawing its a bit hard to say, but you can look into that anyway.
I think Len’s suggestion plus a short topmast extension opens the possibility of a fairly decent a sloop rig, if that is what you would prefer. Do not skimp on mast height (as I think you have done in your most recent drawing). You need as much halyard drift as you can get, for a number of reasons, and if you try to cram too much sail onto a mast which is a smidgeon too short, you will regret it.
Summary: If you want a sloop rig, your first concern must be to get the tallest mast you can.
After that, you can look at the various forms of junk rig and see what gives you the best out of the mast that you have. The choice of which type of junk rig will also have some effect on where the mast (tabernacle base) is placed, don’t forget – but otherwise I think the choice of sail type is of less importance than first organising a high enough point for the halyard, and getting on as much sail area as you can, since you are struggling to match what your current rig gives you.
In the bigger scheme of things, you need sail area, camber and a means of managing it. The rest is detail. All the modern junk rig types have their advantages and disadvantages, they are all good.
(When choosing the sail type – as you have realised - with a higher yard angle you can get a little bit more sail area onto your chosen mast. This might influence you a little towards Arne’s Johanna rig. The difference is not that great that it’s a game changer, but it’s definitely a thought. First and foremost – decide if you want a sloop or not, and if you want a sloop – you’ve got to get that masthead up to 13m+ in my opinion, so start from there).
Step 1: run your proposed aluminium mast tubes past the people who have expertise in this area. They will want to know outside diameters, wall thickness and grade of aluminium. In addition, I would suggest length of proposed topmast extension (if you are going for a sloop) - and some idea whether you are thinking of inshore cruising or whether you plan a trip around Cape Horn.
Step 2: decide where you want the mast to be placed and accordingly what type of junk sail will fit best - and then you can start worrying about scaling up batten lengths and all those other secondary details.