Thru-hull Transducer mounting/fairing technique..?

I am installing a new RayMarine depth finder in my Catamaran which is currently in the water. I want to make and bond my inside fairing block for the transducer (1.87 inch shank). Also I’ll probable finish the job when I’m beached somewhere so I need to have all my prep work done so the job goes quickly. Any tips on a good fairing material and how to best approach this project appreciated.

 

I usually use marine ply (laminate for thickness) or a hardwood block. I have used Starboard too. If you know the deadrise angle, just set up a table saw and make your cut. Otherwise, I use a bevel guage and "eyeball" a transverse member for "level" to get my angle. Pre-bore your 1.87 hole and bond the block with the goop of your choice (I use epoxy, 3M 5200 is good too). I would 'glass the block completely if it's wood, so give all your corners a 3/8" or so radius before sticking it in for good, so you can 'glass the whole thing easily. When you're ready to cut the hole, drill a pilot hole dead center from inside, then hole saw from the outside. Your pilot hole will give you the right angle, so don't force it. On a final note, if you have a cored bottom, I would cut out the coring material about 1 inch around your block, build up the outer skin with as many layers of alternating mat and roving as it takes to give you about half the thickness of the coring material (more if you want to really "bullet proof" the thing, and lay several layers of mat over the exposed coring to seal it up good, again giving everything a nice radius so the 'glass will lay nicely. Then install your block. Have fun