Does anyone know of a locking devise or rubber "boot" that will secure the mast and prevent it from turning when the catamaran is moored? Last year I used plastic zip-ties through the holes at the mast bottom to hold it but I'd like to get something quicker and more secure this year. I have an older (1988) Prindle 16.
Also, Can anyone suggest a clear algae resistant bottom paint for the hulls?

attach your jib sheets to the mast rotator, sheet, and cleat. No recommendation on bottom paint, tho..

Beach catamarans are generally not reccomended to keep in the water for long periods. I believe leaving your cat in the water for extended periods would lead to leaking or delamination.
Good Luck,

Leaving yoru beach cat in the water for long periods is not good for two reasons.

1) Normal gelcoat and epoxy paint are not truly waterproof. Over time water will get into your hulls and wreak havoc on the fiberglass sandwich. You need to use a barrier coat that is formulated to block the water penetration. Many of these also have anti-fouling additives to help with algae growth. Clear, don't know of one. White, I think I have seen one before.

2) The waves bang the heck out of your rigging. Not only does the mast rotate from stop to stop, but since your shrouds are not tight the mast will wobble around and shock load your shrouds, forestay, and all connection points. Not good for the hardware. All kinds of damage can occur over time. To prevent this you have to tension your rig so it is no longer loose. I like to tension one shroud and use the jib sheet on the mast rotator (Like John said) to tighten down the rig.

I have never left my boat sitting in water for longer than a few hours while not sialing so I have no experience with the barrier coat.

Lots of monohulls have blisters caused by water seeping into gelcoat. It is a common occurrence.

The blisters are caused by water getting into the hull lay up during construction. The resulting blisters are like an aneurism in that they start from the inside.

I'm really skeptical! You're gonna have to persuade me.

It's not that I can't be wrong, I want to be sure.

This is not something I know a lot about, but I have some questions..

I know older constructions buildt with chopper guns or chopped strand mat and polyester have osmosis problems, but I tought the risk of osmosis (and hence blisters) was negligible with woven mats and epoxy. As far as I understand osmosis on boats, the ends of the glassfibers need to be exposed for the water to enter, and chopped fibers are especially bad in that regard (not to mention the inconsistency of the fiber layout).

Delamination due to humidity in the laminate? How does this really work? When the matrix is bonded to the distance material, how is the bond destroyed by humidity? Decomposition of the distance material?
If mooring the boat is enough to let a critical amount of humidity trough to the core by diffusion (or is there something else at play), what about letting a small amount of water stay in the hulls while on land/storage? Or even worse, letting water/humidity stay in the hulls, closing all ventilation and letting the sun heat the hulls?

I will admit I have only seen gel coat blisters on boats 15-20 years old.

Maybe the problem has decreased with improved practices.

Read this.

"Fiberglass Blisters - Explanation, Diagnosis and Repair"
Hartoft Marine Survey, Ltd., Annapolis, MD

Thanks Matt.

[quote The resulting blisters are like an aneurism in that they start from the inside.
[/quote]
PAINFULL

PAINFULL [/quote]It's the same as someone having a stroke caused by a blood vessel bursting or a toothy little alien coming out of your chest.