Mikeym_us:Bill you will need at least 3 sizes of dowels to make the masts as well as metal bands to hold them together along with a lathe to turn down the upper most mast part. all in all it might sound easy in theory but in actuality it is a bit more difficult. but there is a possibility that some beefing up of the deck supports in the hull may be required as actual wood masts may add extra weight to the deck.
warshipguy:
I would recommend simply scratchbuilding new masts and yards from wood. They are stronger than the plastic and can handle the rigging far more effectively than plastic ones.
Bill
You don't need a lathe to make spars for a model like that. Just an electric drill, a few sheets of sandpaper in different grits, and a vacuum cleaner (assuming that your wife takes exception to clouds of sanding dust).
For convenience, clamp the drill in a vise on your bench (or a sawhorse). If you're right handed, mount the drill on your right. Either wear a glove on your left hand or pick up a rag with it. (Your hand ia about to become the tailstock of your improvised lathe.) Cut the dowel off about two inches over the finished length. Chuck one end of the dowel in the drill, turn on the drill at a fairly high speed, hold the free end of the dowel in your left end, and have at it with the sandpaper. You may be surprised at how quickly you can work the taper into the dowel. You can start with whatever diameter of dowel you can find conveniently; the big variable is the amount of time you'll have to spend sanding. (Some modelers prefer to start with a raw piece of wood split from the edge of a board. That trick guarantees the grain will be straight.)
Lots of experienced modelers do it this way - largely because the small lathes they own aren't big enough for the job. My old Unimat, for instance, can't turn anything longer than about thee inches.
You do need to be careful about the dowels you buy. The manufacturers these days are making them out of at least four woods. My personal favorite is cherry. Maple is ok, though kind of brittle. Birch is nice IF you're careful to get a piece whose grain runs parallel to the length. I don't recommend oak, except on very large-scale models.
I confess I've never found the weight of the spars to be significant. (The weight of those awful injection-molded "sails" is another matter. I'd be willing to bet that a wood yard would be considerably lighter than a plastic one with an integrally-molded sail.) To install wood masts in a plastic hull will take a little ingenuity. The best approach probably is to drill a hole through the deck and step the mast firmly on the bottom of the hull with epoxy.)
Like so many other techniques in sailing ship modeling, this one takes a little practice. But not much. My guess is that you can make a full set of spars for that model in one or two evenings.
Here's a somewhat more expensive, but quicker solution: http://www.modelexpo-online.com/product.asp?ITEMNO=MS100 .
Hope that helps a little. Good luck.