any alternatives to bondo for intake / hull inteface

Discussion in 'Metal Boat Building' started by allpropless, Jan 24, 2011.

  1. allpropless
    Joined: Jan 2011
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    Location: Florida

    allpropless Junior Member

    I'm moving along in my current build and I'm looking to clean up the edges of the pump intake where it connects to the hull of the boat. I'm looking for a smooth surface to elimate as much cavitation as possible. This will take some build up of material to transition from the bottom of the boat to the intake surface.

    Is there a better / tougher alternative to bondo? My hull thickness is approx0.075" aluminum and I'm not to interested in laying beads of weld then grinding down as the transition...
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Epoxy with a metal filler. You can actually buy it in tubes (J-B Weld)
     
  3. michael pierzga
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    michael pierzga Senior Member

    By bondo, I assume you refer to.... micro fiber reinforced epoxy resin ? If so its good choice for fairing thru hulls....you might consider one of the modern epoxy resins like west system G flex . The thru hulls on this boat are faired with epoxy. After the Alum hull was epoxy primed and faired a PVC tube, whose OD equaled the ID of the thruhull, was inserted into the thru hull . The PVC pipe was then trimmed off to extend 10mm past the hull and gently faired with a sanding board into an arc shape. The tube was then extracted, coated with mold release, reinserted into the thru hull and used as a guide, form, for applying a 14 to one slope... epoxy filler wedge infront of the thru hull. with care the shape of the epoxy wedge was near perfect and required little fairing. The PVC tube was knocked out and removed after fairing by taping with a hammer. Several wrapps of mylar tape works well as a mold release for the PVC pipe and expands its diameter slightly to form a tight, tap,tap with a hammer , fit into the thru hull.

    Bondo...polyester filler... is not suitable for underwater bonding to aluminum.
     
  4. eggman918
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    eggman918 Junior Member

    try "devcon" products similar to 'JB weld" but much stronger.
    They have many products for many applications most mil-spec if properly
    applied.
    Steve.
     
  5. anthony goodson
    Joined: Mar 2007
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    Location: Dorset UK & Murcia Spain

    anthony goodson Senior Member

    All useful information Michael ,but for pump ,read jet pump.
     
  6. allpropless
    Joined: Jan 2011
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    allpropless Junior Member

    very helpful, thanks. I've considered JB weld but wasn't too excited about working with it to form the shape or contour needed. Is the "devcon" easier to work with or is it just as tacky and gummy as JB weld? Can it be sanded / smoothed out once cured?
     
  7. mark775

    mark775 Guest

  8. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    JBWeld should not be tacky at all. It can be sanded, cut, tapped and machined.
     
  9. allpropless
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    allpropless Junior Member

    You are correct, I was referring to the period once mixed while applying. Then again, it has been several years since I've worked with JB weld so I may be thinking of some other two part 'epoxy' that was tacky and tough to mold?
     
  10. eggman918
    Joined: Jan 2011
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    eggman918 Junior Member

    Devcon comes in many compounds for different materials most can be machined.
    when applied they can be shaped before fully cured much like clay with hands wet with water.Often used in the repair of large pump cases when welding is not
    a viable option.
    http://www.devcon.com/products/products.cfm?brand=Devcon
    Steve.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Most of the materials offered will make sanding, shaping and fairing quite difficult. Use a mixture of Q-cells and silica or west System 407 and some silica to control viscosity. PC-7, JB Weld and these other products are very dense, difficult to spread let alone shape and forget about sanding it unless you use an angle grinder.
     

  12. CR Contractors
    Joined: Jul 2017
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    Location: Puerto Rico

    CR Contractors New Member

    The friend who suggest Devcom knows his business , but that product is really expensive , with a good cleanup with acetone Marine tex will do wonders , slso at the big orange hardware store they sell a good epoxy in a large service to fix rust structures in concrete .
     
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