‘Diamond in the Rough’, or ‘Pasture Time’ for this catamaran?

Discussion in 'Multihulls' started by Coastal Ogre, Sep 9, 2019.

  1. Coastal Ogre
    Joined: Jun 2019
    Posts: 16
    Likes: 2, Points: 3
    Location: Florida

    Coastal Ogre Junior Member

    I thought I would ask the benevolent gray beards for some thoughts on this yacht. I realize it is easy to say “depends on the survey”. But this might be beyond what is typically seen in the second-hand market. In fact, there are a handful of very intriguing catamarans currently for sale that are not mainstream and might be beyond the scope of a typical one-day pre-purchase survey to ascertain the true state of the structure.

    1993 Catamaran G&B Mitchell G60 Sail Boat For Sale - www.yachtworld.com https://www.yachtworld.com/boats/1993/catamaran-g-b-mitchell-g60-3552580/?refSource=standard%20listing&refSource=standard%20listing

    So to spark some discussion, here are my initial questions:

    1. Anyone know of the history of this builder? (currently, the internet is awash with the sales ads on this unit and not the actual builder/designer)
    2. What technically specific areas should be reviewed when inspecting the wood & epoxy hulls?
    3. Thoughts on the longevity of the construction v. solid (or even cored) hulls? Any issue with cyclical fatigue?
    4. I see the forward deck around the windlass is beyond life and the listing does state several overdue maintenance issues that need to be dealt with, but I’m not seeing any fatal issues in the text (of course). I once had the pleasure of walking around this catamaran in Grenada while I was hauled out. Due to timing with my own cat, I did not inquire to go inside. However, the exterior was stunning (great lines and huuge!).
    5. Construction and/or design issues from the early 90’s that have since fallen out of favor that might be present (and a potential buyer should be aware of)?
    6. If moisture damage is found, what options are there for mitigation and repair with this construction?

    Thanks for any and all feedback!
     
  2. Corley
    Joined: Oct 2009
    Posts: 3,740
    Likes: 172, Points: 63, Legacy Rep: 826
    Location: Melbourne, Australia

    Corley epoxy coated

    I seem to recall she was a Ron Given design, a NZ designer with a good reputation for designing solid, reasonably fast and seaworthy boats with most pro built. Cedar strip/composite construction has excellent properties as far as fatigue goes. The most important thing to check is where penetration through the core has occurred that it is properly repaired and back filled with epoxy. Things like new winches and deck fittings are often where damage will occur if improperly fitted.

    She is listed on Ron's website too:
    Ron Given Catamaran Design, sail and power, New Zealand and Noumea http://www.givencats.com/

    There is a detailed walkthrough on YouTube you may not have seen as yet?
     
    Coastal Ogre likes this.
  3. Coastal Ogre
    Joined: Jun 2019
    Posts: 16
    Likes: 2, Points: 3
    Location: Florida

    Coastal Ogre Junior Member

    Corley,

    Thanks for this information! I did notice that she is listed on Mr. Given's website based on your post.

    Says she has an estimated 70k miles under her keels (as of 2001). I wonder the what percentage of life this equates to?

    And the video is interesting (I watched it around a week ago), if Ron Given's name was mentioned then perhaps I wasn't properly paying attention.

    **Edit - I had to chuckle! They said Ron's name in the first minute of the video... I'll claim that I hadn't my earphones on yet when they mentioned him :).

    Thanks for identifying her!!
     
    Last edited: Sep 9, 2019
    Corley likes this.
  4. catsketcher
    Joined: Mar 2006
    Posts: 1,203
    Likes: 88, Points: 48, Legacy Rep: 790
    Location: Australia

    catsketcher Senior Member

    Don't think that the boat will have a given number of fatigue cycles or lifetime. If the boat is designed well, it will have low stress on the important components. This can equate to an almost limitless lifetime. The DC 3 plane and most bridges are designed with large factors of safety and this means that the number of fatigue cycles to failure is into the hundreds of years. Same with many wooden and even fibreglass boats. As long as the loads are low enough you get heaps more fatigue cycles.
    If the boat was a lightly built racer, it would have some sort of fatigue life built in. But considering Gives designs are well regarded, I would think that it is up for many decades of cruising.
    The great thing about wooden composite structures is that they will tell you when they are undergoing high stress. They will crack. So if you find some cracks in the beams or structure then this is telling you that that part is too highly loaded. But it doesn't mean it will catastrophically fail. This is why I like nice wood composite laminates instead of thin foam carbon ones for cruising boats - wood composite often fails really slowly, whereas carbon in some situations can fail catastrophically.
    So consider the boat for sure - its not even into its stride yet.
     
  5. Coastal Ogre
    Joined: Jun 2019
    Posts: 16
    Likes: 2, Points: 3
    Location: Florida

    Coastal Ogre Junior Member

    Catsketcher,

    Thanks for this feedback. I will need to investigate the correlation between useful life of a complex object and factors of safety, as I've never heard of them being directly linked. Do you have any references perhaps?
    Likewise it has been my experience that all complex manmade objects in a dynamic environment have a useful life (often described in potential cyclical loading/stress), whether defined or not by a designer.
    Interestingly enough, aerospace and aviation designs have very low factors of safety (around 1.2-3.0 depending on the sub-system). Which is usually nagging me when I'm helping our A&P perform maintenance on my wife's Piper Cherokee. And I'm not sure the FAA would agree that a DC-3 (although a marvel in engineering) would be airworthy for a century without significant NDT and component replacements.

    Thanks for the tip on the cracking wood - as I'm sure there have been modifications over her lifetime (with and most likely without builder/designer oversight). And we will investigate this thouroughly, if we decide to move forward.
     

  6. catsketcher
    Joined: Mar 2006
    Posts: 1,203
    Likes: 88, Points: 48, Legacy Rep: 790
    Location: Australia

    catsketcher Senior Member

    There are lots of wooden boats that underdo cyclic loading every day. My cat sits on her mooring and back when she had removable windows I could hear them gently squeak every time a wave passed. She is sitting there cycling all the time, even more when we sail.
    Fatigue cycles tend to be logarithmic, so you can get a boat that will last for a very long time with a little more laminate and lower loading. Read more from the Gougeon's, they were the first guys to investigate wood epoxy fatigue.
    A Summary of the Fatigue Properties of Wind Turbine Materials (Journal Article) | OSTI.GOV https://www.osti.gov/servlets/purl/12694
     

    Attached Files:

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.