Marine Goop and Styrofoam are not compatible

Unless you want to slowly melt Styrofoam...and yes the back of the Marine Goop package said not to bond Styrofoam.  Some of us like to learn the hard way!   

 

You ought to see what happens when you try to stick a hot coat of fiberglass resin to it. 

-Spot-

Why is it that I don't find topics like this until it is to late and I learn the hard way?

Since I can't seem to find dense cell foam to the size I need, I will next try the RTV/styrafoam combination.
I got a free remnant of styrafoam house insulation from my local ACE hardware store, but a whole sheet of it would have been cheep also.

A pool noodle will not work because the new"Down Immaging" transducer is much longer. I would need a piece that is at least 7" long.

Erik

Try an appliance store for closed cell foam or, next time you're out this way, stop by and I'll give you a chunk.

-Spot-

The "kneeling pads" sold at garden centers are closed cell foam.  Some are on the thin side but I found some at Wilco that were thick enough and less then $10

K. Jr used schedule 80 pvc, which the goop also started to melt. He saved his install by a few wraps of duct tape that held the shape of the pvc until the goop set up.

+1 on the Garden kneeling pads. 

OK... I found some foam that will work. It's not "dense cell" or "closed cell" but it is actually firm foam. I'll add pics as I'm probably "pioneering" the Down Immaging I transducer kayak "through hull" mount being that its so new to the market.

I had another idea though. Has anybody just tried to use spray foam? There would be no need for Marine goop and it could form the puck that holds the TD and the water.

As a matter of fact I'm thinking of getting several cans to add flotation to the ends of my T13 instead of being stuffed full of pool noodles anyway.

Erik

Assuming I'm thinking about the right type of spray foam, it probably is more work than its worth.  I was considering getting some low density pourable polyurethane foam to add some permanent flotation to the bow and stern of my boat like you suggested.  After reading some previous experiences people have had doing just that on other forums (north cal I think) I concluded it was too much of a mess.  I also couldn't really think of an easy way to work around the rudder controls if I were to add the stuff to the stern.

K. Jr used schedule 80 pvc, which the goop also started to melt. He saved his install by a few wraps of duct tape that held the shape of the pvc until the goop set up.

sorry lb that was only sch 20 drain pipe, it was easy to cut and form to the hull. i think sch 40 would withstand the goop, but have not tested it yet.
i would just say no to spray foam. it will not adhere to your hull for any length of time and is a sponge for H20

Foams by their nature encapsulate air or chemical vapor.  Not sure that is good to shoot through.