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I'm about to replace the mast wedges in our F40 (CF masts), as I had to cut out the urethane items that were in place when we removed the masts. Does anyone know where I can obtain replacements from? I am looking at Spartite as a possible alternative and see that some people mention cheaper alternatives: can anyone recommend any of these?

I went with http://www.smooth-on.com/ castable utathane rubber. Comes in differentry hardnesses, Spartite is around a Shore Hardness of 60 -don't think you want to be softer than that. A cheaper product. I needed two sets of hardner/resin. I cast half round wedges, used the old ones to hold the mast in place, cast the new ones one at a time. WAX,WAX,WAX... and you don't want any contour on the mast or boat side that will key in. I made a plastic plate as a mold around the mast below deck , sealed using modeling clay, also built a dam to address the curved deck. All sounds more complicated than it really was. Take your time, worry a lot, it will be fun ...

Erik

mc-master website has ready urethane bars and strips of different sizes and hardnesses. I bought one of those formed bars of shore hardness 70 or 75 4 years ago. The length of that bar was 3.14+ of my masts diameter so I intended to cut new wedge out of it ( you can cut it all right) .
My original wedge is not like a solid ring , it has one cut in it. it is not like a donut but rather a strait strip laying in groove in deck around the mast. I do not know if it is supposed to be donut or not ? The gap between ends of my original wedge was about 1 -1/2 to 2'' when I put it back.
so I ended up reusing my old wedge and just added some small bit of wedge I produced out of 'mcmaster' urethane bar which tightly fits into the gap and acts like a lock. so far so good.. 4th year now

I aslo want add that I sealed the metal ring / bolts holding wedge down to deck with black 5200 3M caulk (which was probably bad idea , I used sleeve on my mizzen mast later ) but point is that black 5200 holds watertight 5th year now and seems to be UV resistant indeed.

my round mast just uses wood wedges, I have a few extra's and could make you a new set for a small fee
cheers,
Yarrow

Last year, I cast two wedges for my Freedom 39PH out of Smooth-On PMC-790 2-part polyurethane which has a Shore A hardness of 90 (the hardest that they make). You also need to use an accelerator because the PMC-790 on it's own requires 48 hours cure time before demolding (try keeping your boat and mast still for that long). With the accelerator, cure time comes down to 4 or 5 hours. I used Smooth-On KICK-IT! accelerator. As a mold release, I used Smooth-On Universal Mold Release.

A few recommendations based on my experience:

• Pick the calmest day that you can too minimize mast movement.
• Stabilize the mast as much as possible. I used the two halyards fore and aft, and two ratchet straps to stabilize it side to side. I also used various wooden blocks and shims below to stabilize the mast.
• Follow recommendations on the packaging for temperature and humidity (I had to wait two months before finally getting the right conditions).
• Very important, DO NOT cast in direct sunlight. The polyurethane will cure too fast, to the point that you may not even have time to finish pouring it! (Don't ask how I learned this.)
• If you use clay to make a dam, it is imperative that it be sulfur-free, oil-based molding clay. Sulphur inhibits the curing process.
• Carefully cover surrounding deck areas, and put a plastic over furniture and floor below. An accident happens quickly, and this stuff is extremely hard to cleanup.

It all works very well. Have everything prepared ahead of time. When the right day comes, follow the instructions to the letter and take you time!

I too used PMC-790 on Flutterby, and they have been successful so far, although I've not done much sailing on them even though they've been up ~5 years.

The prior owner had done spartite, and the partners were badly scored and keyed, and it got messed up when I took the masts out. Then I refinished both the partners and the masts. In the hole below my mast step, I found one piece of original PU wedge material, about enough to go half-way around a mast. I ended up cutting it into pieces of wedge about one inch wide, and tapped four of them around each mast to hold my mast in place while I poured the PMC-790. They got molded into the rings pretty securely to my eye, and all was good the one time I removed and replaced the masts. I put release compound on the partners but not the masts. They pretty much stayed put on the masts, although when I was tightening down the aluminum top-hat rings with butyl putty filling the gap, I think I saw the wedge starting to force down a teeny bit, so I suspect it isn't fully locked on the mast anymore.

It is pretty clear that PMC-790 (or spartite) is a bit softer than the original wedges. If I ever have to do it again, I would seriously consider getting some harder PU stock and shaping it into four to eight sections, tapping those in to position my mast, and pouring a much smaller batch to fill any gaps, and make a full ring. I'd also make a bigger/better dam on top for my main mast since the partners aren't horizontal, and my ring doesn't go quite to the top in front.

So far, my only issue is a bit of creaking from my mizzen, but I just noticed that it slipped 1/4" to SB in the base; with the foot moving, I'm not surprised at the partners creaking, if that was indeed the source.