Beneteau also created a leak-potential problem in their popular 350 model. Over the years we have had three of these in our club and they have all leaked. I know of one that was permanently repaired, and will always be leak free. The fellow that did it had to build a new curved lens set, and that was an interesting project in itself.
BTW, other boat builders have created the same problem with long fixed-port lenses, like Yamaha and ODay, to name only two.
The problem, as alluded to by others here, is the different thermal expansion of the lens and the frp cabin structure.
Our boat had leaks on the fixed ports when we bought it, and it was caused by the same problem. I once did the math on the difference in expansion/contraction for my Lexan (r) ports and my boat frp structure and it was significant. (If my hull were molded out of Lexan it might be almost half a foot longer on a very hot day...)
The solution is to "float" the lens on a bed of sealant thick enough that it will keep a mechanical grip on both surfaces and not be torn loose from either side. On our boat with a bit over two feet of length of lens, we bedded our four new lenses in about an eighth inch of sealant when we installed them. That was in '95, and they are still leak-free. (Easy answer to getting the depth uniform is to put an appropriate rubber O ring around each screw, hole before gunning on the sealant, on our boat. And, put a tooth pick in each hole to mark it before laying in the sealant.)
The Ben 350 that had its huge new cabin lenses bedded in, used something like 15 or 20 tubes of sealant total. (!)
There are several great sealants that have adhesive qualities and will never attack the plastic. I chose black LifeSeal.
BTW, other boat builders have created the same problem with long fixed-port lenses, like Yamaha and ODay, to name only two.
The problem, as alluded to by others here, is the different thermal expansion of the lens and the frp cabin structure.
Our boat had leaks on the fixed ports when we bought it, and it was caused by the same problem. I once did the math on the difference in expansion/contraction for my Lexan (r) ports and my boat frp structure and it was significant. (If my hull were molded out of Lexan it might be almost half a foot longer on a very hot day...)
The solution is to "float" the lens on a bed of sealant thick enough that it will keep a mechanical grip on both surfaces and not be torn loose from either side. On our boat with a bit over two feet of length of lens, we bedded our four new lenses in about an eighth inch of sealant when we installed them. That was in '95, and they are still leak-free. (Easy answer to getting the depth uniform is to put an appropriate rubber O ring around each screw, hole before gunning on the sealant, on our boat. And, put a tooth pick in each hole to mark it before laying in the sealant.)
The Ben 350 that had its huge new cabin lenses bedded in, used something like 15 or 20 tubes of sealant total. (!)
There are several great sealants that have adhesive qualities and will never attack the plastic. I chose black LifeSeal.
