any alternatives to bondo for intake / hull inteface

[allpropless]

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...

[gonzo]

Epoxy with a metal filler. You can actually buy it in tubes (J-B Weld)

[michael pierzga]

Originally Posted by allpropless

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...

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.

[eggman918]

try "devcon" products similar to 'JB weld" but much stronger.
They have many products for many applications most mil-spec if properly
applied.
Steve.

[anthony goodson]

Originally Posted by michael pierzga

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.

All useful information Michael ,but for pump ,read jet pump.

[allpropless]

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?

Quick and easy, Splash Zone. Even works in water. Every boat has some on board, don't they? http://shop.sailboatowners.com/detail.htm?group=1555

[gonzo]

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

[allpropless]

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?

[eggman918]

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/produ...m?brand=Devcon
Steve.

[PAR]

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.