Securing a Battery Box to the Deck

[LCnSac]

This seems like such an elementary question, but I'm stuck. I'm installing a second battery in my 150 Sport, next to the factory installed start battery in the console out of the weather, and I'm out of plywood below the deck, according to the wood plan, for the starboard strap holder--I have wood on the port side. I'm tempted to simply use 5200 to secure the starboard plastic strap holder to the deck, and maybe secure the new battery to the well anchored start battery box with a strap. Am I asking for trouble, or do I need to glue epoxied wood to the deck and screw in the strap holders? Could I get away with screwing the strap holder to the deck with no plywood below with 4200?

Edit: Thinking through this, how about drilling out a larger hole through the deck into the core, injecting epoxy resin or Marine Tex, and screwing into that when dry?

[Binkster]

The entire deck of a Boston Whaler 15 footer has plywood under it. When I cut out a rigging tunnel to a center console That I built for my 15 footer I discovered that the undersides of the deck was 1/2" 3 ply plywood. After some research I found out that there is plywood everywhere.

rich

[LCnSac]

Rich, this is a 150 Sport. The wood plan shows only 1/2" 10" x 20" plywood on the port side of the console, inside. You may be referring to the classic 15?

[Phil T]

You are on the right track.

I use either Marine Tex or Gorilla Glue. If you use the glue, mask off the holes since it expands. Trim off the overfilled once it sets.

[Binkster]

Thanks for the correction. I was thinking of a classic. I've used Gorilla glue or 5200 to glue parts onto boats and both work extremely well. Marine Tex is more of a Bondo type material.

rich

[jimh]

...how about drilling out a larger hole through the deck into the core, injecting epoxy resin or Marine Tex, and screwing into that when dry?

Making reinforced areas using a method somewhat similar has been suggested in the past. The method usually suggested is different than yours. The usual method suggested for creating a reinforced area for anchoring a screw fastener is as follows:

--drill a small diameter hole through the gel coat and laminate layer, into the foam inner hull filler;

--fashion a tool with an L-shape, similar to a small Allen wrench;

--using the L-shape tool as very simple auger bit, insert the tool into the small hole, then rotate it, with a variable speed drill motor, so the L-shaped tool begins to cut away at the foam under the laminate, creating a cavity under the laminate; you may have to do this by hand at first to get the cavity started;

--use a strong vacuum to remove the broken-down foam from the cavity under the laminate;

--continue creating the cavity under the laminate until you have achieved the diameter and depth of cavity you feel is appropriate to hold the screw fastener;

--prepare some slow-cure formula epoxy; add filler materials to the epoxy; good filler material can be as simple as sawdust; powdered fillers can also be used; it is important to not use pure resin as it will become too hot during curing;

--using a syringe, inject the epoxy resin and filler solution into the cavity; if the cavity is large this may have to be done in steps; and

--let the resin and filler cure completely,

Once you have created a hidden resin-filled cavity under the deck, you should drill a new pilot hole. Epoxy can be quite hard and may not take a self-tapping thread very well. Consider using a machine screw tap to cut threads into the epoxy. Creating a reinforced area for a point of attachment of a threaded fastener like this will spread the load of the fastener over a wider area. This should create a much stronger fastening point in the deck of what would otherwise be an unreinforced area.