In anticipation of you next questions, here are some pics of the mast topper setup I have. It is extremely simple and un-complex, and only cost around $5 to $10 bucks to make, and really no tools needed except an electric drill.
To start you need to go to Home Depot and buy this sink drain tube.
This is what it look like after slipping it over the end of the mast.
The tube is made of brass and is triple chrome plated so it doesn't corrode. Mine is still the original tube I put on over 3 yrs ago and have way over 5,000 miles on it in all kinds of conditions. About midway down the tube drill a 5/16 hole thru the tube. You then just take a 5/16 stainless bolt and run it thru the hole, and put a nut on it, your done (takes all of 5 minutes). Now loosen the pull down line that holds the sail down down at the bottom of the mast (take note of the types of knots used, and how it is held down). I recommend sliding the sail off and taping over the end of the mast with electrical tape, so the tube can't scratch the carbon fiber mast (a really bad thing, so be very careful with the CF mast, not to ding or scratch it). Next you slip the sail back over the mast and slide the tube over the top of the mast by pulling the little nylon strap over the top of the sail over to one side. The 5/16 bolt fits nicely into the slot at the top of the mast and prevents rotation of the sail. Now you slip the nylon strap over the end of the bolt (hint, it easier to remove the nut, slip the bolt back, then slip the strap over the end then push the bolt back in and put the nut on. I slid and glued a piece of tubing over the exposed threads so it can't cut into the nylon webbing. Now just pull the sail back down at the bottom and tie it back to the mast bottom (using the same type of knots as it was originally). Your done, you will never have to remove the mast topper again, it's there for the life of your boat. If you ever sell the boat just slip it off, take the electrical tape off, and transfer the tube to your new boat ( I'm now on my 3rd TI). It weighs next to nothing ( a few ounces at most).
Now for the rotating mast topper itself, in it's simplest form at about 4 lbs you can use a 4 inch piece of galvanized pipe (1 inch I think) and a T connector. with a 1/2 steel rod slipped thru the long part of the T, the 3ft rod is slipped in about 1/3 of it's length (1 ft out the front, and 2 ft out the back). I used PVC reducers to keep the rod centered in the tube, then file a couple notches into the rod (so the epoxy adheres better to the rod), then just glue the rod into the T with epoxy. If you can find 1/2: x 3ft stainless rod it won't rust, and will be much stronger than the mild steel I used, If you use mild steel, you will need to paint and cover the rod with electrical tape to prevent rust.
Here is a pic of the finished product.
Here is a closer pic
The thin rod sticking out the bottom is just a piece of 3/8 steel threaded rod cut to the correct length. I slid in PVC tubing to keep the rod on center (must be on center), and just filled the T with epoxy to hold everything together. You can cut the rod to the correct length later, I covered the rod with a piece of PP tubing so it doesn't scratch anything. The little rod in the center is what spins while sitting on side of that 5/16 bolt that you put into the mast topper. This bearing (it's called a point bearing, like in a watch movement) is exactly the same type of bearing that is at the base of the mast, and makes furling very easy.
You will notice there is quite a bit of slop between the 1 inch pipe and the brass mast topper, don't worry bout that, the mast topper gets sand and everything else in it, so looser is better. Think about it the furler only spins when you are furling the sail, and typically most of us point into the wind and relax the sail to furl it in and out (much easier to furl that way, all boats do that).
I just tapped the end of the rod and screwed eye bolts into the ends. The eyelet on the short end is for the spinnaker, the ring close to the mast (held on by a hose clamp) is where I hang my jib. The eyelet at the back is for the rear stay. I just clip the lines on when setting up. To keep the lines from tangling I just keep the rear stay line and the jib halyard line in 3/8 PVC water pipe. I just unclip each end then just throw the pipes on top of the boat for storage along with all the masts ( I hate tangled lines), simple.
The little guy cable on top of the mast topper is to add a little extra strength to the rod, I had the rod bend when I was sailing with all the sails up in 25mph winds on downwind runs. If you don't plan on really pushing the boat to 20mph speeds, you can forego that little guy cable.
Alternately if your worried about 4 lbs way at the top of the mast, you can always make a topper using the one of those fiberglass pultrusions, the pultrusion version only weighs 2 lbs all in, and is about 50 times stronger than it needs to be.
Here is the pultrusion version.
Here is a close up of the halyard line for the spinnaker. I just drop the mast, pull the mast topper off the top, then just lay it down in the boat for storage, the tan 3/8 water pipe keeps all the lines from fowling and are just laid on top of the boat. It takes all of 2 minutes to raise and lower the mast. It takes another couple minutes to raise the jib and spinnaker using the two halyard lines. Since going to wing sails, I seldom use the spinnaker anymore, since the boat is faster than the wind on downwind now, the spinnaker no longer works, am planning to make a code zero to replace the spinnaker for use in lower winds.
The new mast topper is made from PVC tubing. I made a fiberglass sock to fit around the fiberglass pultrusion and inside the T, then filled the whole works with epoxy (very strong). The little steel rod sticking out the bottom is the same design as the old mast topper, just a steel rod wrapped with fiberglass cloth and glued into the T with thin west epoxy poured into the whole works (very light weight and strong).
To start out if you only planning on just using a jib in light winds you can probably forego the rear stay line, if you do that you can just use a short rod with an eyebolt as the mast topper.
Hope this helps you.