Quick question for any Polycraft owners

[Remote River Man]

Hi all -

I'm planning to screw a Santmarine storage bin (one of those the long, white plastic ones) into the inner hull of my new 4.5 Drifter Frontrunner along the side of the boat, and am wondering about the correct length of stainless steel self-tapper screws to use, as well as the thickness (gauge). My understanding is that both the inner and outer hulls of a Polycraft are around 10mm each in thickness, with varying amounts of space between inner and outer hulls depending on where on the boat it is. So I want the screws to bite nicely into the full width of the inner hull but not extend too much into the space between, and not at all into the outer hull.

I imagine in places like the flat ledge just behind the windscreen (on a Frontrunner), where you'd drill straight down into plenty of space to install a fishfinder or compass, length of screw isn't as much of an issue. But I suspect there's much less leeway along the side bulkheads. I'll be using washers and a dab of Sikaflex on each screw hole, and drilling a pilot hole first. I welcome advice on screw lengths and thickness. What screw lengths do the rest of you normally use around different parts of the boat, especially along the inner sides?

 

[XD351]

From memory most of the stuff I fitted used screws in the 2 - 5G range . 2G for things like clips for landing  nets and 5G to screw the front deck extension down ( poly 410 challenger ) - I mostly sized the screws according to the mounting  holes in the part I was fitting . With my boat I found out the hard way that the area along the floor where it meets the sides is right above the tunnel inside the chines  is solid and not as thick as I thought - fortunately it was one hole that can’t be seen that was easily fixed with a hot knife and some of the plastic swarf from drilling the holes . I had to make a drill stop so I didn’t drill all of them though as the drill bit pulls itself into the plastic really fast ! A blunt drill works better just keep the speed of the drill as slow as possible - polyurethane melts very easily !