foam/tower reinforcment

[xjcj3a]

Hello,

i am installing a DIYwake shark fin tower onto my 1996 glastron gs160. I have a question about mounting. I have the side of the boat marked and ready to drill, but behind it is foam. I am making an oversized mounting plate out of plywood. Should i chisel out the foam to lay the ply directly to the underside of the fiberglass? or laying it directly to the foam is ok?



Also, the legs do not mount flush with the gelcoat. I was planning to make some plastic shims to fill in the slope. Best way or can i use some kind of epoxy? thanks for any help.

 

[jmmacky]

Re: foam/tower reinforcment

I would remove the foam and apply your backing plate directly to the fibreglass of the boat otherwise you could still get some flex. I'd remove the foam in the area, sand the glass, clean with acetone and apply the plywood mounting plate using PB (resin, chopped strands and cabosil). You could put a layer of csm over that as well to spread the load over a larger surface area.

Instead of a plywood mounting plate I used a product called coremat to reinforce the inside of my hull at the tower mounting points.

 

[akorcovelos]

Re: foam/tower reinforcment

did you get the tower used? It should have come with rubber pads that go on the outside of the Hull between the legs and boat.

 

[xjcj3a]

Re: foam/tower reinforcment

it did come with the rubber pads, but i didnt think with the slight concave of the boat that i should just use those. do you have experience with that?

Also, what is PB? and CSM?

 

[akorcovelos]

Re: foam/tower reinforcment

if the Hull is to concave /convex for the rubber pads to take up the gap then you shouldn't mount the tower there. post pics of your boat and where you plan to mount the feet. PB =peanut butter and CSM = chopped strand matting.

 

[xjcj3a]

Re: foam/tower reinforcment

i would say, when the bottom of the mount is flush with the boat. it leaves a 1/4 inch gap at the top. sorry dont have an image of that with me. This is probably the smallest curve on the entire boat

 

[xjcj3a]

Re: foam/tower reinforcment

Here are two images of identical boats to mine

 

[akorcovelos]

Re: foam/tower reinforcment

There can't be a gap. PM me your email and I'll send you a copy of the install directions for my Big Air Ice Tower which is basically identical to your tower. It will give you the info you need.

 

[the-goose]

Re: foam/tower reinforcment

Tower installation is not as complicated than it looks. I just installed a Monster MTE basic universal tower on my 1986 17.5 I/O closed bow runabout. In addition to the 3"x4" base plates supplied with the tower brackets I added an extra 3"x10" plate lengthwise under the hull at the front brackets. At the rear brackets I figured the forces are mainly downward, so I placed the extra plates on top of the hull. Both front and rear brackets are mounted horizontally as opposed to angled at the side of the boat.

I put a tow rope on and had a couple of buddies pull and tug hard at the rope with the boat on the trailer. The tower feels pretty sturdy in all reasonable directions but I am still not 100% comfortable that the front won't pull out or crack the hull. The PB CSM and Plywood might be a better idea. Now I'm thinking of running some thin cable lanyards from the top of the tower to another point on the bow, is that lame? Thanks for the input?

 

[akorcovelos]

Re: foam/tower reinforcment

if the tower is installed correctly there is no need for cables. Most of the load on the tower is pulling away from the boat so the extra backing plates should go on the inside of the hull with only the rubber pads on the outside. If you put solid plates on the outside without the rubber pads its going to crack your gelcoat from the movement of the tower. The tower will move a bit, its designed to.

 

[jimtur]

Re: foam/tower reinforcment

this is what I do on my boat



1/2" plywood with screws and glued with fiberglass resine, and I add 2 layer of fiberglass.

 

[Lake Lizzard]

Re: foam/tower reinforcment

Absolutely reinforce the inside of your hull with plywood or fiberglass. As the others have said - remove the foam to get to some clean fiberglass and then reinforce.