Floor reinforcement for fiberglass river boat

[rgary3]

I'm new to fiberglassing boats, so I was hoping to get some advice on reinforcing the floor of my fiberglass river boat. I've attached some pictures of the floor of the boat, you can see that it has two wooden runners and the rest is just fiberglass. This is a 20' 48" boat and with only two runners there is flex in the boat when it hits a wake or rough water. This flex has started to cause some hairline cracks so I want to reinforce it and repair the cracks.

My original thought right now is to sand down the gelcoat to the glass and then fiberglass in either marine grade plywood or HDPE marine sheets in between the runners so they would be flush with the runners creating a floor that would not flex when faced with rough water or wakes. Is this a reasonable plan? If so once I sand down to the original fiberglass, do I need to place a fresh layer of fiber glass for the marine grade plywood or HDPE to sit on top of before I fill in the gaps and glass over top of them? Any advice would be greatly appreciated!

Thanks!
RG

 

[Chris1956]

Adding plywood would add some strength, but not much. A center stringer, and a plywood deck over all three stringers would be stronger.

A frame, gunwale to gunwale would effectively cut the length of the stringers thereby adding strength, but you would need to step over it.

Not much in the way of good advice, sorry.

 

[Scott Danforth]

foam under the deck would add support