My opinions:
THe bottle brush in your pic has to be the highest point on the mast. Your
VHF antennae is higher, defeating the purpose. As I recall, they suggest 6 inches over the everything.
Dissipators, such as your bottlebrush, have had marginal effects. Many now opt instead for a lightning rod with a very sharp tip on top. The current theory (highly debated) is that by grounding your boat, you decrease your chances of being struck because you can bleed off the potential. I personally find this difficult to believe - but that is the saying.
Grounding a boat or not grounding is a serious consideration. I feel that a poorly gounded boat poses more of a danger than a boat that is not grounded at all. Either do it, and do it all the way... or do not do it at all. All metal must be grounded, including toe rails, tie rods, and especially your steering mecahnisms. #8 was once recommended, but now that has been chaged to #4 (IIRC) for a straight run from the mast. DO not use your keel as a grounding plane and FOR GOD's SAKES DONT USE A DYNOPLATE*** unless you plan on swimming afterwards. The more surface area exposed to the saltwater, the better. Special plates have been developed to do this. They should not be painted. A seperate lead, #8-#4, should be run to ground the diesel/prop. It should be independent of the main run, preferably running perpendicular with its own lead and outside of the remainder of the boat grounding (stanchions, etc). The third leads can all be tied together and run to a similair ground plate.
The reality of doing a correct and proper job on grounding a vessel has been severly overlooked by most sailors & manufactureres (and especially motorboaters). It is very involved and moderately expensive. As the odds of being struck are very small, it may be the best money you have ever wasted. However, for anyone in very electrical prone areas such as South Florida, the islands, or the Northern part of South America, it should be highly considered. Those travelling offshore should also strongly consider it.
Just my opinions.
- CD
*** A bronze dynoplate is porous. That poricity gives it more surface area which makes an very good ground for "low voltage" items such as
SSB. However, in a lightning strike, the very high energy causes the water inside those pores to rapidly heat up, then boil. That boiling water creates steam and pressure, which often cannot be released from the pores quickly enough. THus, the plate will explode - often taking a chunk of the hull with it. You will sink quickly. Dynoplates are dangerous lightning grounds and should not in any way be connected with your lightning grounding system in my opinion. Still, I am amazed when I see "offshore" boats whose lightning ground is a dynoplate.