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  1. #11
    Join Date
    May 2001
    Location
    UK East Coast
    Posts
    36,245

    Default Re: Chamfering a backing pad

    Quote Originally Posted by zoidberg View Post
    My understanding is that you're exactly right.

    I don't see why you can't take an iron file or a sander of some sorts, and chamfer your block that way. Takes but a couple of minutes...

    Also make sure you round the corners/cut or sand off any sharp angles, for otherwise you can get a concentration of load leading to cracks in the GRP..... or so I'm told.
    If it's bedded on filler, there's no problem. It's a lifeline fitting, not subject to eg rigging loads.

  2. #12
    Join Date
    Jul 2006
    Posts
    4,766

    Default Re: Chamfering a backing pad

    Quote Originally Posted by pvb View Post
    If it's bedded on filler, there's no problem. It's a lifeline fitting, not subject to eg rigging loads.
    Lifeline loads can be remarkably high in extremis. I'd use 18 or 24mm ply, and strong U-bolts with large washers. I've seem lifeline fittings bent and almost pulled through the deck despite a ply backing pad and new penny sized washers.

  3. #13
    Join Date
    Jul 2003
    Location
    West Australia
    Posts
    11,635

    Default Re: Chamfering a backing pad

    Quote Originally Posted by srah1953 View Post
    I wasn't thinking of using epoxy. I asked because in a book I read recently it suggested chamfering the edges. It didn't say why but I'm assuming the reason is the possibility of a "hard" edge creating a weak spot.
    Probably chamfering the edges is simply to make a good looking job of it. Assuming you are not going to put glass over the wood. (That definitely needs chamfer and filler into the tight corners.) So just take off the rough edges or not as you wish. There should be no load problems on the edge away from the GRP and presumably no concern re splitting. ol'will

  4. #14
    Join Date
    Sep 2001
    Location
    Home - Sothampton, Boat - Gosport
    Posts
    10,090

    Default Re: Chamfering a backing pad

    Quote Originally Posted by LadyInBed View Post
    If you are talking about chamfering the top edges, I think it is a good idea because square edges splinter easier and splinters can snag on braised rope, webbing or clothing.

    PS: A Router bit on an electric drill would do a job.


    Attachment 79762
    Unless your drill is mounted in a stand, I could see that ending in tears.

    As for epoxy or polyester, TBH, all the force that matters is going to be pulling the ply into the GRP, so car body filler would be fine. The U-bolt will hold everything together anyway. However, if strength of bond matters, epoxy every time.
    Steve
    Never believe anything until it has been officially denied.

  5. #15
    Join Date
    Jun 2007
    Location
    Ireland, Carlingford
    Posts
    439

    Default Re: Chamfering a backing pad

    Quote Originally Posted by jwilson View Post
    Lifeline loads can be remarkably high in extremis. I'd use 18 or 24mm ply, and strong U-bolts with large washers. I've seem lifeline fittings bent and almost pulled through the deck despite a ply backing pad and new penny sized washers.
    I'd love to know, out of pure curiosity, the conditions they were subject to. Surely must have been very extreme, no?

  6. #16
    Join Date
    May 2001
    Posts
    14,370

    Default Re: Chamfering a backing pad

    Quote Originally Posted by srah1953 View Post
    I'd love to know, out of pure curiosity, the conditions they were subject to. Surely must have been very extreme, no?
    Depends on what is "extreme". A crewman weighing 80 kilos falling overboard will put a heck of a shock load on the fitting when the tether reaches the limit and comes to an abrupt stop.
    Should we paint what is on a face, what is inside it, or what is behind it?

  7. #17
    Join Date
    Jul 2006
    Posts
    4,766

    Default Re: Chamfering a backing pad

    Quote Originally Posted by srah1953 View Post
    I'd love to know, out of pure curiosity, the conditions they were subject to. Surely must have been very extreme, no?
    Well - two on deck went overboard as the boat was violently inverted: boat then landed on one injuring him quite badly.

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