jopj

January 27, 2011

New film

A new video is published under video/photo. In this film Yrvind introduces one of his most famous boats, Bris I.




January 11, 2011

LIGHTNING CONDUCTOR

This is Christer Bohlin. Expert on lightning explaining the theory and giving me advice. Thank You Christer.

Below his picture follows a text, than more pictures.

The high voltage of lightning is something that I definitely do not want inside my boat but sometimes one have to do the best of the situation.

If lightning strikes it passes through my boat wether  I like it or not. As most superior forces the more resistance it meats the more damage it will do. Therefore I decided to make its passages through my saloon easy and convenient by building a lightning conductor.

It has taken time to get used to the idea that one day millions of volts from the lightning may pass trough the cable within a few inches of my head without morphing me into some kind of Frankenstein.

To get things properly done i have been consulting Christer Bohlin who for many years been conducting research at Uppsala University´s high tension laboratory. He told me that quite to the contrary I could even hold my hand on the cable when the lightning is passing trough it, that it is as safe as sitting on a high tension power cable. Although I trust science I will keep my fingers away when I hear thunder.

I have two separate systems. One is permanent. It connects the stainless steel grab-rail on the deckhouse to the bronze shoe at the bottom of the boat.

There is also a secondary system which can be set up when lightning approaches. It consists of two six meter long cables connected to a bronze rod. The bronze rod can be inserted into the mast head fitting where the top mast otherwise goes. One cable then runs down two meter into the water on each side of the boat. This is important because otherwise there will be a potential difference. That is different voltage on each side of the boat.

Matt Layden was once struck by lightning being at anchor at Block Island R.I. I have not been struck, but I have experienced St. Elmos fire a bright blue or violet glow, appearing like fire it was accompanied by a buzzing sound. Although not dangerous in itself it means that the whole atmosphere is charged with electricity and that there are a high risk that lightning will strike. It is worrisome.

I like to thank Retronic of Västervik for the supply of the tinned cables.

The bronze shoe is used to ground the cables. It is connected to the cables by 3 ten millimeter silicon bronze bolts.

Below the cables connected to the three bronze bolts.

Below I made cable holders of glass fibre composite.

Below the tinned copper cable wrapped around the grab rail.

Below the cable was encapsulated in Tesa Professional vulcanization tape to keep out the epoxy as not to get bad conduction before being encapsulated in NM-epoxy composite for strength.




WordPress logo