Sailboat Owner's Guide to Corrosion - Hull and Motor (Collier 16 - 17)

Oct 19, 2017
O'Day 19 Littleton, NH
Welcome to Section 6, the Sailboat Owner's Guide to Corrosion - Hull and Motor (Collier 16 - 17), of our SBO Book club study of Everett Collier's book, 'The Boatowner's Guide to Corrosion".

We are reading and posting, in sections, as we work our way through the subject of corrosion in the marine environment. Each section covers one or more chapters and has been posted in their own threads. As the new threads are started, I will tag any interested participants and create a linked table of contents to make it easier to follow along and participate.

A rough outline of the sections to come are as follows. They may be edited and updated as the current of our discussion requires.

  1. Sailboat Owner's Guide to Corrosion - Fundamentals (Collier 1-4)
  2. Sailboat Owner's Guide to Corrosion - Self-Corrosion (Collier 5)
  3. Sailboat Owner's Guide to Corrosion - Galvanic and Stray Current Corrosion (Collier 6 & 7)
  4. Sailboat Owner's Guide to Corrosion - Metals Aboard (Collier 8 - 12)
  5. Sailboat Owner's Guide to Corrosion - Protection (Collier 13 - 15)
  6. Sailboat Owner's Guide to Corrosion - Hull and Motor (Collier 16 - 17)
  7. Sailboat Owner's Guide to Corrosion - Electronics and Plumbing (Collier 18 - 19)
  8. Sailboat Owner's Guide to Corrosion - Topsides (Collier 20 - 21)
  9. Sailboat Owner's Guide to Corrosion - Resource
Let me know (@Will Gilmore) if you want your name added to this list. It will appear at the beginning of each new thread to let interested members know when the new thread has opened. You can then post something or click the [Watch] button to follow the thread.

Tagged participants:
@Will Gilmore
@Mark Maulden

I'll be happy to edit/update this list at any time.

Some basic rules for maintaining useful and topic focused discussion:
SBO is a public forum, and as such, anyone interested, is welcome to participate, ask questions and express their opinions. There are limitations to the form these expressions can take and the culture of participation. All the basic forum rules of decorum and good manners apply. As a participant in this series of discussions, we would ask that participants remain on topic and refrain from derogatory language or remarks. The express purpose of this series of threads will be to understand corrosion in the marine environment using Collier's book as a guide. We therefore, expect participants to make an honest effort to read and stay up on the material under discussion. We are a group of congenial sailors with a sense of humor that often can run astray. A playful comment on occasion is expected, but anyone of us will feel free to firmly redirect anyone back to the subject at hand if it looks like it is in danger of derailing the discussion. A moderator will be asked to intervene, edit out any inappropriate comments, and possible ban an offending participant, should the group find their continued presence a serious distraction. Posting in this thread will be considered agreement to these terms. Thank you so much for your understanding and cooperation. I look forward to being part of the amazing community that is developing around this subject. I know we will all have a great time.

-Will (Dragonfly)
Oct 19, 2017
O'Day 19 Littleton, NH
Chapter 16 - Hull Corrosion discuss issues with construction, fasteners, materials and placement of fixtures of or on the hull that are susceptible to collision.

Most of this chapter is general information inline with what Collier has already said about corrosion. He discusses the pros and cons of different fasteners and their material. Where it is impractical to use same metal fasteners to fasten same metals, hull fasteners should be more nobel than the material they're fastening. He gives the example of never using copper alloy fasteners in aluminum. However, referring back to his chart in chapter 4, aluminum and aluminum alloys are far less nobel than copper alloy fasteners. He describes severe pitting in the aluminum as a result. This I can believe, but he suggests far less corrosion would occur if using stainless fasteners in aluminum. Huh!

Still, some galvanic corrosion is likely to occur no matter. The results are that either the fastener loses diameter or the hole through which they run gets bigger. In both cases there is a loosening of the fastener's hold.

Another danger is the contact of a hull fastener with something like a thru-hull fitting. This accelerates corrosion.

The description of glass rudders with a steel armature was interesting. I can't thought about how those are made. With the connection to the metal shaft bushing box and steering system inside the hull, cracks in the fiberglass in area water can mean corrosion of the armature.

The other interesting thing Collier had to say at the end of the chapter was about carbon fiber in hull construction. Carbon fiber is both conductive and highly nobel and can have a disastrous effect on any less nobel fasteners, thru-hull fittings or attachments through the fibers in seawater.

-Will (Dragonfly)