Easy to do

I foamed my (former) 170 mast and boom also (just bought a larger sailboat- but can still try to brief you on the procedure).

What I did was go to Home Depot and got several 6 foot (or maybe it was 8 foot) long noodles of A/C coil insulation-- the grey or black colored foam-noodle stuff thats often wrapped around the copper tubes that run from your houses air conditioning compressor. The diameter on these foam insulation noodles is about two inches...a perfect size to fit into the mast and boom.

I used a powerdrill to drill out the rivets that hold the aluminum masthead (which houses the halyard sheaves). I removed the masthead and then just inserted the foam insulation noodling into the mast. On my boat the stuff stopped going in at about 13 feet-- I think it hung up on the several spreader rivet studs that intrude into the mast-hallow. I deemed the upper 13 feet of mast float to be all that would be needed anyway. The lower part of the mast shouldnt theoretically get near the water if the mast is sealed and upper float doing its job.

Next I used 3M duct tape and silicon chaulk to carefully and somewhat cosmetically, seal the hole just below the masthead sheaves (the hole will be visible if you look at the masthead/aluminum fitting from the bottom up. This would be a huge entry point of water in a capsize, if not sealed. I also used 3M 5200 marine sealant/adhesive all the way around the top of the mast, where the masthead fitting meets the spar (mast) proper. I also 5200ed the rivets that I used to replace the masthead.

I then pushed noodle down the aft, open end of the boom- and it simply stayed put because the rivets at the aft end of my mast protrude into the inside of the boom just enough to stop the noodle from backing out.

Others might have a variation on this theme...but probably similar to this in principal. I never tested my method in a capsize drill (I only like to get wet in a Laser!), but Im assuming shell hold. I dont think the guy who bought the 170 planned on testing it either- but its nice to know its insurance.

The only time I ever capsized my 170 (and she quickly turtled-- this was pre-noodling, obviously) was when I was suddenly slammed by a line squall of what I estimate was 35-40mph wind for several minutes. It happened in less than 10 seconds. So I guess my parting thought is, no one ever plans to capsize. Others whove noodled and tested it say it works great.

Best,
Mike G.
s/v Freebird -Compac 19