Here is a Formula 16 mast design for the aluminium superwing section that I made using what works from the Taipan design and improving what didn't work so well. Most things were tried on my own mast and those experiences have been used to fine-tune it once more.
This mast design is fully F16 rule compliant and allows a mainsail to be downhauled to max 8.1 mtr. The boom is pretty low and I really don't think anyone would want to put a longer luff mainsail on a doublehanded F16. You would make your crew really mad. All distances are measured from the bottom of the mast section, excluding the thickness of the mast foot plate. My mainsail has a luff of about 7900 mm and during the REM-race 2004 in 20-25 knots of wind I downhauled that all the way down to my boom fitting. That is a 200 mm stretch and is also the very max my (unintentionally shorter)downhaul system allows. I initially designed my downhaul system to a 150 mm max downhaul as that was given to me by Taipan sailors. However my cascade downhaul system can produce significant more pull and so I pull an extra 50 mm out of my luff. My downhaul internal system bar is at 1420 mm instead of 1500 mm and I don't know why I made that mistake when building up my mast. But still during this REM-race we could completely depower my rig to the point that we both set on the luff hull comfortably in 25 knots of wind when we had to wait for a large fishing vessel to pass.
Due to various reasons my current mainsail fits just within this design, but next time I think I will order a mainsail with a slightly shorter luff length. I'm thinking about 7850 mm when untensioned and 8050 when fully tensioned. If anybody considers shortening the luff even more than they should place the sail feed gap higher as well. At 7850 mm untentioned the foot of the mainsail will only just pass the bottom part of the sail feed opening. Any shorter and it will hang on this point when downhauling.
My mast rotation is placed on the mast foot plate, is sheeted of the trampoline and I'm very happy with that. I would not consider sheeting the rotation arm of the boom on a spinnaker boat. I think that is inferiour and needless expensive, but it will be to much to explain why here. On A-cats and F16's without a spi I can see advantages of a boom sheeted rotation system increase.
Standard Taipan sailors should take into account that my main beam sits 25 mm higher on my hulls than their mainbeam. Therefor I have 20 + 25 = 45 mm more clearence under my boom near the mast and relative to the trampoline then they have. Especially under spinnaker I appreciate this increase in boom height near the mast. My boom therefor hangs more horizontal then on the Taipans as my clew is still in the same place. I did alot of research on the boom height on spinnaker boats and found that you really want it to be 500 mm of the (tensioned) trampoline at a location is about 300 to 500 back of the mainbeam. When Hoisting, retrieving or flying a spi you really can not expect your crew to work with a boom that is lower than that. Blade (homebuilder) builders should be able to use this very mast setup very succesfully as long as they move the sail feed up by 30 to 50 mm. The boom height will be perfect for them.
I general I'm very happy with this mast. It look really clean with the rotation arm on the mastbase and the internal downhaul system.
I can warmly advice AHPC fitting for the mainsail hook, boom fittings and hound fittings. I use 390 mm proctor spreader arms and I can advice those warmly as well. Set these up at their minimal length (390 mm) and with 50 mm rake as the minimal starting point. Increase rake if you sail in strong winds often and the rig needs to improve its gust response a little. I still have to measure prebend. Will post that later. I use 3 mm 1x19 stainless wire for my diamond wires and these do their job beautifully. I really see no need for using dyform wires here. As tensioners I use two small turnbuckles that are fitted to the mast base plate This plate sticks out a little and I drilled two holes in it (as AHPC does as well) I bought two threaded forks and put these through the holes with the threading point upward. To this I screw the turnbuckles. The other side of the turnbuckles take the threading that is pressed on the wires. Easy, effective, inexpensive. Right now AHPC has copied this approach on the Capricorn F18's. I stole this idea from Phill Brander. At least I saw what looked like this in one of his picture and I thought :"that is smart, I want to have that". To Taipan sailors with the old system; I can tension or detension my diamond wires without taking my mast of the boat OR having to take the diamond wires out of the spreader arms. This makes adjusting the tension and prebend between races a WHOLE LOT easier.
If you are using the AHPC mainsail hook fitting as well AHPC's mainsail welded shackle and ring and the distances specied above than your mainsail will hook and un hook like a dream when you use a headboard and have the eye that takes the fitting at the spacing shown in the picture below. (upper bearing surface eye about 30 to 35 mm back from inside bolt rope)
Push up sail users need to look no further. Halyard users will need to fit a little block as shown in the next picture.
For the halyard coming out of the bottom of the mast I currently use a small opening in the mast groove just below the sail feed gap (pretty close the the internal web of the mast) as the Stealth design does and that works, but I still want to show everbody the solution the Mark Woudenberg has implemented on this Taipan F16.
The spi gate is best build as shown below :
And the internal cascading system is build as follows :
Don't forget to bend the lower lip of both exit blocks leading the downhaul line into the mast and riveting this to the mast base plate instead of the mast itself. Don't look at the picture of my mast as I did it wrong. Look at Mark Woudenbergs picture. Although you can do it my way and use either the rotation arm or a ronstan cleat base to raise the cleat to the right height relative to the exit block. In my case I find that cleating the downhaul is now very easy on my boat. because of the line being pulled downwards a little towards the exit block. Right now I don't consider swivel cleats at all. I don't need them and it would make my mast only more complex than I would like.
That is it. It is now public domain knowledge. Spread the news.