Mast step/foot – epoxy instead of plywood buildup?

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  • 24 Jun 2021 23:27
    Reply # 10695769 on 10658937

    Hi Chris,

    exactly. Additionally if done a different way Fw x  (H+B) equals Fp x B. This assumes that the mast is pinned at the base and the force of the sail is balanced by the force at the partners. Just a different way of calculating the same thing.

    David.

  • 24 Jun 2021 13:46
    Reply # 10693992 on 10658937

    The drawing attached shows how I understand forces related to a Free Standing Mast. Basically, it is as Howard explained, except I think at partners forces will summ up : force generated by wind and the reaction at mast step. Since I have learnt statics some 50 years ago, I might be wrong and if so, would appreciate  explaining why ;)


  • 22 Jun 2021 18:43
    Reply # 10685240 on 10658937

    Just a note on resins.....  Epoxy is about 2.5 times the weight of plywood, and has little strength as a solid block....It shines as an adhesive and laminating resin, not as a solid material.   HDPE is essentially not pourable, and only slightly lighter than epoxy.... about the weight of water... epoxy is slightly heavier, HDPE slightly lighter.   HDPE can be formed fairly easily, in it's "melted" state, which is NOT a pourable liquid.  It is very viscous...like taffy.  It also cannot be bonded to anything by any glue known to man. 


         It strikes me that the compression load of a free standing mast is trivial compared to the other loads, and the function of the mast sole and step is to transmit the longitudinal and lateral loads into the hull over a large enough area that it will not damage or deform the hull structure.  Those loads can be several tons.  The load on the partner should be identical except for the lack of any vertical load.  The ratio of the bury to the distance to the vertical center of effort from the partner is the multiplier... simple leverage.  


          The use of epoxy and cabosil or some other thickener should make fitting the sole into the hull fairly easy....It doesn't seem to me that this should be too critical so long as it is filled.

  • 22 Jun 2021 08:35
    Reply # 10682493 on 10682147
    Anonymous wrote:

    Thanks Tony,

    I've been an avid watcher of your YouTube channel for months, and watched your mast foot and partner videos a few time.

    Please, keep up the great work.

    Matt



    Thanks Matt. I'll do my best :-)

  • 22 Jun 2021 06:11
    Reply # 10682147 on 10658937

    Thanks Tony,

    I've been an avid watcher of your YouTube channel for months, and watched your mast foot and partner videos a few time.

    Please, keep up the great work.

    Matt

  • 21 Jun 2021 09:30
    Reply # 10678047 on 10658937

    If I might be so forward, here's a video of how I built my forward mast step using a design/method that was VERY strongly influenced by Arne's write up. I hope it can be of some help...


    https://www.youtube.com/watch?v=c34N-aimJug

  • 18 Jun 2021 15:06
    Reply # 10662860 on 10661814
    Anonymous member (Administrator)
    Matt wrote:

    Arne:

    How thick is that mast sole in your writeup?

    It doesn't appear to be fibreglassed, only epoxied?

    So, there's a gap underneath?

    How heavy is Ingerborg's mast?



    The sole is 6 x 15mm = 90mm.
    Only epoxied.
    Yes, there is a gap under that sole. 
    The mast is around 53kg.
    Arne
  • 18 Jun 2021 13:23
    Reply # 10662350 on 10658937

    Yes, layering is the way to do it, but you only need to wait until the preceding layer has gelled and cooled before the next pour. Just be prepared to stop and wait if there's too much heat build-up. Still, it makes sense to reduce the quantity of resin by adding something lighter and less expensive. Wood chips? sawdust?

  • 18 Jun 2021 11:16
    Reply # 10661814 on 10658937

    Arne:

    How thick is that mast sole in your writeup?

    It doesn't appear to be fibreglassed, only epoxied?

    So, there's a gap underneath?

    How heavy is Ingerborg's mast?

    Mine is 90kg, just making sure that something similar to Ingeborg's mast sole will suit mine.

    I'm thinking it might be simpler for me, while the boat is in the water, to sculpt a mast sole out of foam, then make up the plywood version back in the shed.

    David:

    That makes an annoying amount of sense.

    Can one mitigate the heat problem by doing successive layers, say, 24hrs apart, 10mm at a time?


  • 18 Jun 2021 09:29
    Reply # 10661188 on 10658937
    Anonymous member (Administrator)

    Matt,

    my original reason for making my first maststep out of plywood  was probably because I knew this material best at the time (Malena, 1990).

    Later I have found that this was a lucky choice for more than one reason.

    • ·         The plywood maststep has a very big contact area with the hull. This makes the bond of the glue less critical.
    • ·         This is a general purpose method which works both on flat bottoms and on V-shaped bottoms. That big, rigid plywood sole makes sure that the whole glue area works in unison, and it also beefs up the hull at the same time.
    • ·         The MkII mast step, built in two stages with a sole part and a step part, simplifies getting the mast plumb, or with the right rake: One test-steps the mast with the mast step temporarily fitted, then makes adjustments, and finally glues the maststep permanently to the sole. This lets one use smaller mast partners with much less clearance around the mast, since the mast need no more adjustments here to get the rake correct.

    This sort of mast step surely is not the quickest to build, but it is safe and amateur friendly. If you start now, instead of spending weeks on discussing a smarter way, you will get the job done faster than you think.

    Good luck!

    Arne


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