Click for Westport Click for Abeking Click for Mag Bay Click for YF Listing Service Click for Nordhavn

tank hatch terminology

Discussion in 'Technical Discussion' started by Capt Ralph, Apr 5, 2015.

You need to be registered and signed in to view this content.
  1. Capt Ralph, Apr 5, 2015
    #1
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,727
    Location:
    Satsuma, FL
    I opened up an inspection hatch on a fiberglass water tank by removing many machine bolts along its perimeter.
    Inside the opening is an alloy bar with threaded inserts thats acts as the nuts, retainer & backing plate to the cover hatch and thru bolt arrangement. A few of these threaded inserts are stripped or damaged.
    Seems like a simple enough piece of hardware.

    I'm having a brain fart tonight but I can not think of what to call this item or find replacement bars on the web.
    It's late and I'm tired but nothing comes to mind on what to even call it.

    Any ideas out there?

    Attached Files:

    Last edited by a moderator: Apr 5, 2015
  2. Capt Bill11, Apr 5, 2015
    #2
    Capt Bill11

    Capt Bill11 Senior Member

    Joined:
    Feb 27, 2006
    Messages:
    1,458
    Location:
    Sarasota/Ft. Lauderdale FL
  3. Donzi 54, Apr 5, 2015
    #3
    Donzi 54

    Donzi 54 Member

    Joined:
    Oct 21, 2009
    Messages:
    166
    Location:
    Point Pleasant, NJ & Morehead City, NC
    Google "thread inserts" there is many different styles
  4. Capt Ralph, Apr 5, 2015
    #4
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,727
    Location:
    Satsuma, FL
    I'm not wanting to repair what I have with helicoils. I want to replace the attachment bars.
    I have seen ads and articles on them long ago. I'll have to dig up some industrial catalogs .
  5. Capt J, Apr 5, 2015
    #5
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,434
    Location:
    Fort Lauderdale
    The threaded part is sometimes called thread-certs. Not sure what the backing plate with them in it are called. You might want to just have a few thread certs welded into what you have. I don't think you can buy the backing plate with them in it anywhere. Might need to have a machine shop make it.
  6. Capt Bill11, Apr 5, 2015
    #6
    Capt Bill11

    Capt Bill11 Senior Member

    Joined:
    Feb 27, 2006
    Messages:
    1,458
    Location:
    Sarasota/Ft. Lauderdale FL
    I must be missing something. I don't even see any threaded bars in those pictures. Just what looks like threaded inserts in the fiberglass.
  7. Capt Ralph, Apr 5, 2015
    #7
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,727
    Location:
    Satsuma, FL
    Maybe a better description;

    Underside clamping ring.
  8. K1W1, Apr 5, 2015
    #8
    K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,393
    Location:
    My Office
    I tend to agree with CaptJ that what you have theRe was made for the job in the quantity required.

    It should be fairly straight forward to remove them and have a machine/welding shop make you a set or two the same.

    You could also just use thicker Alu bar and drill and tap them yourself but you would not get what looks like those little stand prouds that are flush with the fibreglass surround.

    If its only a few that are stripped it might be a lot simpler and economical to Helicoil them and use plenty of Tef Gel or similar to negate any action between Alu and stainless if this is the fastener material.
  9. captholli, Apr 5, 2015
    #9
    captholli

    captholli Senior Member

    Joined:
    Jan 4, 2010
    Messages:
    1,164
    Location:
    In The Bilge
    Looking at the photos this looks to be a fiberglass tank flange arrangement using 1/4-20 flat heads counter sunk flush holding aluminum
    flat bar under the tank opening to form a reinforced flange. The fiberglass has thread certs screwed / glued (5200?) into the glass. It would be my assumption that the thread certs are also tapped into the flat bar for added strength. As far as nomenclature goes? "tank manhole bolt flange"?
    Last edited: Apr 5, 2015
  10. NYCAP123, Apr 5, 2015
    #10
    NYCAP123

    NYCAP123 Senior Member

    Joined:
    Mar 14, 2008
    Messages:
    11,205
    Location:
    Long Island, NY
    I think CaptJ hit it. It's simply a backing plate. K1W1 also when he said just make up a new one. Any welder or machine shop can make it up out of flat stock. If you search catalogs or walk around a hardware store you may find one similar that's made for some other purpose as well.
  11. bobhorn, Apr 5, 2015
    #11
    bobhorn

    bobhorn Member

    Joined:
    Mar 3, 2014
    Messages:
    232
    Location:
    Kemah, TX
    Built the same thing for as fuel tank hatch many years ago. The AL bars are threaded for the cover bolts. The bars are held in place using a couple of flat head screws while the cover is off.

    Bob
  12. K1W1, Apr 5, 2015
    #12
    K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,393
    Location:
    My Office
    It sure looks in the photos like there is Alu that sticks up right to the level of the fibreglass. This is why I suggested using a thicker flat bar to allow for some thread depth.
  13. bobhorn, Apr 5, 2015
    #13
    bobhorn

    bobhorn Member

    Joined:
    Mar 3, 2014
    Messages:
    232
    Location:
    Kemah, TX
    The first picture clearly shows the Phillips flat head screw that is holding the backing plate in place. The threaded inserts look like some type of captive nut. I used those to keep from having to tap the aluminum and possibly stripping the aluminum threads. Look at McMaster-Carr for captive nuts.

    Bob
  14. K1W1, Apr 5, 2015
    #14
    K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
    Messages:
    7,393
    Location:
    My Office