I am about to embark on installing my own wakeboard tower. It has been suggested that if the fiberglass is les than 3/8 inch thick I should reinforce the backer plate area with marine plywood. Any ideas of where to get this stuff? Is there any other material I should consider?

All of the factory through hull bolts on my boat are re-inforced with a large piece of 1/2" starboard. I am not sure that would be my choice as it doesn't have a good sheer strength. I don't like wood, period, for such a use either. I would personally track down a piece of say 8ga stainless sheet and try to form it closely to the contour of the mounting point. Fill the void with two part epoxy upon installation.

How big a piece of steel? I work in a steel mill, I can't get stainless but I could getheavy coated galvanized.

Glassing in wood is not a bad idea. It provides a wide distribution of the stresses. I don't know that anyone sells marine grade plywood anymore. I would guess if you glass it in well it shouldn't matter. I would also add the steel backing plate for good measure as I tend to do things to an overkill status.

Try a lumber yard (not HD or Lowes) we have many specialty lumber yards around here. Since the wood is for backing and not in direct exposure to water, how about exterior grade plywood?

even if you chosoe marine grade plywood, i would encapsulate it with epoxy.

I had a 2003 Fourwinns with a factory installed wakeboard tower that shook like crazy. This is what I did; I took the tower off the boat and added 1/4 inch plate aluminum backing plates. The rear mounting plates were appox. 8 by 20 inches. The front plates ended up looking like triangles, and were as big as I could fit. I used epoxy to glue them in and was very happy with the results.

When I stiffened the fiberglass sides of the boat for my radar arch, I used regular old exterior plywood, in two 1/2" sheets (1" total).

I epoxied the bejesus out of it, and feel pretty confident that it will never rot as it is in an area that won't get wet.

When I applied the plywood to the underside of the fiberglass, I first used one of those orange "wire" brushes to provide some "bite" into the fiberglass.

Then I used some West System 404 adhesive filler and mixed it into epoxy - to the consistancy of peanut butter as they all say. I was able to then trowel the filler onto the inside surface of the plywood like plaster, then pushed it up into the inner surface of the fiberglass.

The adhesive filler was for gap filling, because the plywood was flat, and the fiberglass did have some bow to it.

Here are some good references:

http://www.westsystem.com/ewmag/21/better_way.html

Also from West Epoxy:

404 High-Density filler is a thickening additive developed for maximum physical properties in hardware bonding where high-cyclic loads are anticipated. It can also be used for filleting and gap filling where maximum strength is necessary. Color: off-white.

http://www.clcboats.com/shop/supplies/plywood_cedarstrips/

Try here they have epoxy and glass also.

And quite a few interesting winter projects!!

Thanks so much for your responses. I think I will end up using some sort of steel plate because the bolts (which seem quite specialized) are not long enough to add more than 1/2 inch of plywood. I would love to use aluminum but have no idea where to find something like that so it looks like galvanized steel plate. No I need to find an epoxy that is also a filler. Everything I have seen so far is very small quantities and doesn't look as though it will fill the void between the plate and the slight curve of the fiberglass.

Thanks.

For you epoxy I would go with West Systems as you can add whatever fillers you need. As for the backing plates, see if you can prebend a little to take up some of the space so you don't need so much epoxy. Remember, epoxy heats as it cures and trying to cure a really thick application can create other issues.

Did you ever get this installed?

You can get aluminum and/or stainless steel plate at KH(used to be Klure and Harris) Metals on North Main Street in Riverside. I would not recommend using Galvinized with Aluminum and Stainless Steel all together.