Flotation in early Prindle 18

My buddy has an early Prindle 18, and after a close call over the weekend, would like to add some buoyancy that will be available when the hulls are completely flooded. Any suggestions for a boat that's not worth a lot of money? He suggested Great Stuff foam, but I tried to discourage him and promised to consult my panel of experts...
Thanks for any help

I just bought a Hobie 18 for parts and the previous owner had filled the hulls with foam. He did a few things wrong. First, he COMPLETELY filled the hulls with foam. bad news. Second, he didn't allow for drainage by putting some kind of tubing along the bottom. Last, he left the port hole covers off and the foam soaked up all sorts of water. I couldn't pick up ONE of the hulls! I ended up taking a sawzall to it and could barely lift the center 1/3 section around the dagger well!

I wouldn't suggest the Great Stuff foam because it expands and could crack your hull. Also, I'm not sure if it would soak up water or not. You could be inviting a more serious problem by haveing a lot of moisture inside the hulls.

I don't think a Prindle will sink--it may completely fill up with water and turn over, but it shouldn't sink. The Hobies, on the other hand, do have a big chunk of styrofoam in the hulls for flotation but it is loose in the hulls. There isn't a whole lot of styrofoam and it probably only provides marginal floatation--enough for an added measure of security, but probably not necessary.

The easiest most durable is to put float bags like they use for Lasers in the hulls.

The float bags are $16 for 50 lbs floatation & $35 for 250 lb floatation

An alternative is a bunch of inflatable beach toys. Stuff them in the porthole and inflate them. They are on the clearance rack this time of year so, get the best ones you can find. I have seen some "heavy duty" beach balls, that would be great, for a couple of dollars.

Now for really cheap:

* Super heavy duty trash bags (tie and glue the ends shut)
* Collect old Lifejackets from your friends. Be Sure to get a throwable, so he will always be legal (3 in each hull should do it)
* empty plastic bottles (1 & 2 liter soft drink and 1/2 gal milk)
* Search the beach for Styrofoam crab trap floats. (If you come to Houston, I know the cove where they all float ashore)
* Inflatable Woman left over from friends Bachelor Party. This would be cool but kind of hard to explain under some circumstances.

I have a lot of foam noodles in my hulls and mast. They're cheap and they provide a lot of floatation.

This year I added floatation bags. You can buy the really good bags typically used on monohulls but the cheaper bags made of PVC are a good solution for beachcats.

I use both the noodles and the bags. During an accident there is the possibility that the bags would be punctured inside a fibreglass or carbon hull but the PVC is really durable. The bags will not be inflated tightly so they should be able to bend with the hit. If they are punctured though, the noodles will still work. I've heard some say that the noodles will soak up water but I think that observation comes from seeing those that are left in a swimming pool for weeks. If something happens on the boat for the amount of time it takes for the noodles to become waterlogged you should carry a waterproof VHF to summon help a lot sooner.

I recently read of a Star restorer who bought five thousand ping-pong balls and placed them in netting.

This month's "Sailing World" has an article about rebuilding a really old Star monohull, and replacing the ancient flotation with Ping pong balls contained in a bag(s) in areas where flotation can fit (bow & stern apparently). I thought this was a very elegant solution for the following points.
1. typical inflatable or air-filled bags can puncture, and unknowingly, no longer be reliable flotation. Whereas ping pong balls are extremely tough and hard to puncture. the noodles are also good for this, they're tough and immune to puncture.
2. small size would allow being put through small openings, and yet fill larger spaces, and odd shaped spaces. Noodles work with our hull shapes pretty well, also.
3. still allows water to drain under/through them.
4. Weight is pretty light for ping pong balls, although I have not calculated weight to volume ratio for ping pong balls vs noodles, etc. Ping pong balls would not ever absorb or hold any moisture, whereas the foam noodles do soak up some moisture.

Downside - if pingpong balls are not held in place somehow, they might rattle around, making noises that may be irritating. Noodles might be quieter.
Cost - I don't know about costs of pingpong balls in bulk. Retail prices would be prohibitive.

Like in modern medicine, your are treating the syptoms, not the cause. Don't blame the water for this, it's your fault. Take responsibilty of your safety! That like saying guns kill people, you know, people kill people! It sound like she suffers from years of neglect and abuse with no maintenance or maybe you just left the plugs out, I don't know. Anyway, take the hulls off, go over them, find the holes, go over her entirely, repair, refinish! works every time. this is cheap, but labor entensive but if you have enough time to go sailing you have enough time for this!