Starboard backing plates?

Discussion in 'Fiberglass and Composite Boat Building' started by Crocodile69, Feb 28, 2014.

  1. Crocodile69
    Joined: Feb 2014
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    Location: Key West

    Crocodile69 Junior Member

    Hey all,

    I see people switching from wood to Starboard for seacock backing plates. I like the idea, though I was curious if there was cause for concern regarding Starboard's (HDPE) thermal expansion/contraction with exposure to hot and cold?

    I heard from the makers of Starboard that a 1" thick 4' x 8' sheet can expand as much as 3/4". I understand that a small backing plate won't see this much expansion/contraction, though even a small amount of movement over time could cause possible leaks?

    I live in Key West where the sun is brutal, but plan to take the vessel up north periodically. Does anyone have any experience with this? I've attached their worksheet (I hope I did), though didn't run the numbers yet.

    View attachment Expansion_Contraction-Worksheet.pdf
     
  2. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    I haven't known anyone to use starboard, but G10 (a high strength fiberglass) is becoming very common.

    Starboard also has a major issue in that it is a very poor structual material and has almost no stiffness. Wholy unsutable for use as backing plates.

    The G10 however is wonderful stuff and I highly recommend it.
     
  3. Donald Holland
    Joined: Feb 2014
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    Donald Holland New Member

    You can buy epoxy plate material we call it G-10 out here in California this is the top of the line for backing blocks. Although at my yard we purchase aircraft quality ply wood and cut them out using hole saws then bevel the outside edge at about30 degrees saturate them several times using penetrating epoxy

    We typically do this when a new hire comes on board and cut the entire 4 x8 sheet which gives us enough blocks for 4 months. Then if the new kid is real green we send him to find the bronze magnet. All of the guys know what's going on when the kid asks for the bronze magnet. We will say go see Sam he had last Sam says no it's over in the shop ask Steve Steve will send him to see joe it's funny as hell but it's hard to hold a straight face.

    Try it you will get good laughs
     
  4. Crocodile69
    Joined: Feb 2014
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    Crocodile69 Junior Member

    Awesome. The G-10 sounds like a winner. I have several bronze seacocks on my 34' Falmouth Cutter that I'll be replacing. If I order a small sheet of G-10, what would be a good average thickness?

    Also, I want to install a seacock on my exhaust. Do you think G-10 could withstand the heat?
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Starboard (HDPE) isn't the best thing for a backing plate. It doesn't take fasteners well, it don't bond well, it isn't very strong, etc., etc., etc. Plywood works, G-10 is far better and metals (stainless, bronze, etc.) are the traditional choices.

    Welcome to the forum Donald. You sound just like the evil, but good natured person, we all aspire to be when we eventually grow up.
     
  6. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Agree 100%, G10 is perfect for all kinds of backing plates, i glue mine permenantly to the hull or deck with a nice thickened epoxy brew of milled fiber and cabosil to get 100% contact to the uneven glass surface. I see a lot of aluminum plates which are a poor choice.

    Steve.
     
  7. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    FR-4 is a better option for heat. It's very similar, but has a fire resistance rating up to 285F. Depending on how hot your exhaust is that may not be high enough and you may need to look at something else.

    As Steve mentioned I typically just bog it in place with a thickened epoxy, and let it set. The one issue with it is that the board is incredibly hard. Wood working tools will work, but you will dull tools quickly. I recommend switching to ceramic blades for cutting, and carbide drill bits.
     

  8. alan white
    Joined: Mar 2007
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    alan white Senior Member

    A lot like what we used to say to the new carpenter's helper on the crew. Sometimes too much caulk has been squeezed into a joint and someone has to go get the macine that sucks the excess out. So the helper looks around for it, asking the others if they've seen it.
     
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