Glueing topmast - epoxy or sikaflex?

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  • 25 May 2018 21:43
    Reply # 6262172 on 6260872
    Reed Conaway wrote:Also there is a risk of cold temperature bond failure if you sail in high latitudes. 
    3M 5200 is not suitable for temperatures much below freezing, but Simsons is fine.  Your point is well worth considering, Reed, seeing where Jami is based, although I doubt that many people actually go sailing in temperatures much below freezing.



  • 25 May 2018 11:29
    Reply # 6260937 on 6260678
    Ok, thanks again!
  • 25 May 2018 10:24
    Reply # 6260918 on 6260678
    Anonymous member (Administrator)

    Jami

    I think the glue will not fail, no matter what type you use. Even if you only get 50% contact surface, it will still hold well, as we are only talking about some moderate shear forces here. In addition, you will no doubt fit a fairing over the joint, which will have a big glue surface on the top section, so you would hardly need to glue the joints inside the lower mast, at all (but of course, you will)!

    Sooo...
    Don’t worry, be happy  -  and keep up the good work!

    Arne


  • 25 May 2018 08:42
    Reply # 6260872 on 6260678
    Deleted user

    As this is a structure subject to load cycling I would look to examples of how aluminum masts and wings are constructed. 

    Bonding aluminum sections with adhesive will need to be flexible and spread over an unknown minimum area. 

    If the seam is perpendicular to the compression/tension vector without creating a stress concentration in the mast is unlikely. Also there is a risk of cold temperature bond failure if you sail in high latitudes.


    For a freestanding mast intended for offshore sailing this is what I would look at making.

    An all alloy 6061 structure with a composite join comprised of the two sections, a riveted inner sleeve to fix them in place and welding to fix permanently. 

    Several plug welds above and below the seam 

    A butt weld around the seam. Weld in alternating sides of the tube structure in small 1 inch segments to prevent mast centerline deviation. Any deviation can be corrected by alternately using a weed burner and a water hose to straighten it.

     

    If the mast is for inshore sailing then riveting (with several more rivets) would suffice. 

    This is over-engineered, more expensive and takes more time.

    Getting back home after a mast failure will be well . .  You know... 


    RC


  • 25 May 2018 08:28
    Reply # 6260866 on 6260826
    David Tyler wrote:

    Sikaflex would take an age to cure, as it needs moisture. With a wooden topmast, that moisture is drawn from the wood. You'll need to make a conical fairing with epoxy, anyway, won't you?

    Well, I used Simson's Marine glue to glue my wooden topmast to the alloy tube.  The topmast was thickly coated in epoxy, so there was no moisture from that to help with the cure.  I hoisted the sail only a few days later without the mast rotating with the sail, so I can only assume that it cured fairly quickly.
  • 25 May 2018 07:22
    Reply # 6260826 on 6260678

    Sikaflex would take an age to cure, as it needs moisture. With a wooden topmast, that moisture is drawn from the wood. You'll need to make a conical fairing with epoxy, anyway, won't you?

  • 25 May 2018 06:04
    Message # 6260678

    When glueing a hybrid/two-part mast (in my case aluminium to smaller dia aluminium), would it be better to use epoxy or sikaflex (or similar)?

    I have made two glass/epoxy bands for the topmast to make a snug fit. What I’m a bit worried is how do I make sure that the epoxy used for joining the tubes is spread evenly and that the amount is sufficent?

    At first thought sikaflex as sticky stuff would be easier and would also be more flexible option in a bending tube mast. But would it be strong enough?

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