Builders' Forum Archives
Re: Deck Rigging Screw Ho
Posted by LeeG on Nov 23, 2005
Somehow drill-fill-drill got mistakenly associated with the installation of wood screws and deck rigging. DFD is appropriate for anchoring through thin compressible materials like mounting footbrace holes or hollow cores with machine screws. It really doesn't work well with tapered wood screws. Since the tapered wood screw will split the hollow slug of cured epoxy. But it is worth sealing the wood with something other than silicon. Here's the easiest/laziest method: 1. drill holes, 1/8 regular bit for #10 wood screws or the appropriated sized Fullers bit is better. 2. put patch of blue masking tape over hole to protect varnish. 3. screw screw in/out all the way. 4. dab holes with epoxy,,or drop with syringe. If the wood is warm it should soak straight into the porous endgrain and softer underlying cypress. In warm wood I've seen the hole filled and soak up completely after an hour, with SLOW epoxy. EVen a dab or few drops is enough. 5. After a few hours check to see if epoxy is rubbery semihard, you can pull up the masking tape to tell. 6. Install rigging/screws with a dab of silicon on the threads into the hole sealed with partially cured epoxy. 7. Assuming the wood wasn't stripped when the screws were first put in/removed you should be able to snug it down without overtightening.
When the epoxy cures hard it'll leave a well formed hole with solid threads in the wood with the silicone making removal easier.
The problem with using just silicone for a first time installation using wood screws through HARD glassed/epoxied 4mm okoume with soft cypres underneath is that the shank of the screw is wider than the threads going into the soft cypress. Lubed with silicon you'll think the resistance to tightening is the threads pulling the screw through the deck. It's not, it's the unthreaded shank of the wood screw tighting against the hard epoxied deck so the lubed threads are likely to strip in the softer cypress underneath. Fuller bits eliminate that possibility. This all may seem like too much bother but out of 34 odd deck screws going into sheer clamps I've seen two or three stripped from just putting them in with silicon. THEN you have to use epoxy a couple years down the line when the deck is re-varnished. Likewise if you're not accurate with the angle and placement of the hole it's easy for one or two screws to split the sheerclamp. Then water will make it's way in through the other side staining the side panel at the sheer clamp. Or more bothersome catch your hand while you're reaching inside. Which is why putting rigging through the deck with machine screws is desirable,,you're going to seal it anyway. So why not drill, put tape on outside, slap a 1" piece of 9oz tape over hole, redrill, then install with washer and locknut. A reasonable amount of weight could be elimated from the Chesapeake and West river kayaks by elimating the need for 3/4" wide sheerclamps. 1/2" wide sheer clamps is wide enough leaving the deck to anchor the rigging.
In Response to: Deck Rigging Screw Holes by Chuck on Nov 23, 2005