Pygymy Studs for foot braces

Discussion in 'Boat and Accessory Building' started by BDawson, Oct 3, 2016.

  1. BDawson

    BDawson New Member

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    Good morning!

    I'm wondering if anyone has experience with the durability of the Pygmy internal foot brace studs. I really don't want to see external mounts on my Murrelet 2PD hull but I question whether the studs are going to stay put and not tear out.

    Anyone been using the internal stud mounts in the real world?

    Thanks,
    B
     
  2. pikabike

    pikabike Paddler

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    When I built a Shearwater Merganser 16 from a kit, I didn't want to drill through the hull, so I read about the fasteners you call studs and how to glass them in.

    They heid up fine and were still good when I sold the boat years later. However, I epoxied in several layers of fiberglass "rings" of increasing diameter so as to reinforce the underlying layer and really hold the metal disk in place. I don't know if Pygmy fastens them the same way.
     
  3. BDawson

    BDawson New Member

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    Wow! Thanks for the fast reply!

    Pygmy instructions say to mount the studs into thickened epoxy and then slip a 4" square of glass over the post and wet it out.

    Fabulous idea to use increasing patches to strengthen the bond!
     
  4. pikabike

    pikabike Paddler

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    The overlapping larger rings of glass is not my idea, but one from Nick Schade's kayak buiiding forum. Check it out for LOTS of great, in-depth info from people who have built boats. Some tales of woe also, to let you know what NOT to do, such as failing to obsessively measure ratios of Part A and Part B in epoxy!

    That first step, putting the disk on a bed of "dookie schmutz" (epoxy and wood flour), keeps the disk in position for when you add the fiberglass cloth rings.
     
  5. Dan_Millsip

    Dan_Millsip Paddler & Admin

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    I used them on my boats and have no issues. They work well.
     
  6. Astoriadave

    Astoriadave Paddler

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    BDawson,

    Set in the appropriate mix of filled epoxy, those studs will only need one layer of 6 oz glass, if the filled mix is still "green." Meaning it is still tacky on the surface. OTOH, if the filled resin is fully cured, you should get in there with coarse sandpaper and roughen the area the 6 oz glass will cover to promote good adhesion. Added layers of 6 oz glass, wetted out, again over tacky underlayers, will make those studs bombproof. Once the original layer of filled resin is cured, you can add layers of glass, to the uncured previous layer(s) to however many you want, in one continuous layup. This makes for an extremely strong installation.

    Post back if you need more details.
     
  7. JohnAbercrombie

    JohnAbercrombie Paddler

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    I agree that studs can be very secure. Don't make the mistake I did once and make that buildup of thickened resin and glass too thick. I ended up with not enough stud threads to engage the nut fully. It's extremely awkward filing and sanding around those forward footpeg studs! :yikes:
     
  8. Roy222

    Roy222 Paddler

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    BDawson,
    Try to imagine an failure mode. The joint loading is mostlys shear loading
    Epoxy can carry a 1000 pounds per swuare inch.
     
  9. JohnAbercrombie

    JohnAbercrombie Paddler

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    True enough, but epoxy doesn't bond well to steel or stainless steel in my experience - and the different coefficients of expansion of steel and epoxy can cause bond failure. The holes in the studs provide epoxy 'dowels' - without them the attachment would be a lot weaker.
    So a 'belt and suspenders' approach with glass overlays can be reassuring!
    I take it 'on faith' that Boeing has figured this all out (with sintering/abrasion/surface prep?) so that the composite wings on the airplane will stay attached, each time I fly. :D :yikes:
     
  10. Roy222

    Roy222 Paddler

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    John,
    Your correct the holes in plates create a mechanical attachment more then an ionic bond.
    Polyester resin would be a better choice becasue epoxy can cause SS to corrode.
    Tell me more about how sintering is used to prep a surface for epoxy bonding. I am
    thinking lazer the metal when sheiled with inert gas.

    Roy
     
  11. Astoriadave

    Astoriadave Paddler

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    Epoxy corrodes stainless steel? News to me.

    Polyester resin is not an adhesive when used on wood. In the context of use on an epoxy encapsulated wood boat, it would also not cure if applied over epoxy.

    I would stick with epoxy for mounting those studs. The mechanical bond is plenty strong enough.