Anatomy of a hole

rpludwig · May 26, 2020

r u sure that's on your boat?....looks like an astronomical black hole pic taken from the Hubble telescope....u can see the nebula surrounding it, and a few stars being born....

Apex · May 26, 2020

check mainesails posts on the subject. Drill the 1/2" hole, then remove core leaving the skins. THEN fill with epoxy. THe skin holds the epoxy plug in place, and it prevents water intrusion into the core.

AaronD · May 27, 2020

Apex said:
check mainesails posts on the subject. Drill the 1/2" hole, then remove core leaving the skins. THEN fill with epoxy. THe skin holds the epoxy plug in place, and it prevents water intrusion into the core.

I think this is the article @Apex is referring to. @Maine Sail is much clearer than I am. My only addition is that you might find you need smaller diameter Dremel bits than the one he specifies for some applications on our small boats (e.g. cleats mounted with #10 screws).

Grotto · Jun 3, 2020

pclarksurf said:
Strange but interesting-- I had asked a question previously about overdrilling/ potting the 1/2" holes for the upgraded chainplate eyebolts. Theoretical concern was you drill a 1/2" hole, you fill it with epoxy-- then you drill it again... what's the point. I decided to expand (hog out) the topside significantly-- but wasn't willing to do that to the deck and below.

I charged ahead willing to see what I ended up with -- 1) hard to take a picture of a hole

2) appears opaque -- aka: a good coat of not wood.

from the liner looking up toward the deck:

View attachment 179822

Typically when potting holes you drill bigger say 3/4 hole fill then redrill your 1/2 into the epoxy filler it is supposed to create a watertight ring around the bolt so water will not soak into the core if your bedding fails.

AaronD · Jun 3, 2020

Grotto said:
Typically when potting holes you drill bigger say 3/4 hole fill then redrill your 1/2 into the epoxy filler it is supposed to create a watertight ring around the bolt so water will not soak into the core if your bedding fails.

That's one standard method. @Maine Sail's method is a little more subtle. He recommends drilling the holes at actual size, and removing a little core (with a dremel), so when you fill and then redrill, you end up with a tube of epoxy, bounded by the original skin on both sides. Equally water-tight, and possibly slightly stronger.

Quoting from his article:
"I prefer to leave as much of the top and bottom skin in place as is possible. Much of the strength of the deck comes from these skins so leaving them intact when potting a hole is the ta good practice. Leaving the top and bottom skins intact, without over drilling all the way through both skins, leaves you with a captured plug of epoxy that can’t physically pop out or break free as easily as a complete over drill of both skins can."

The whole article is worth reading. I haven't done any comparison testing of my own, but it sounds sensible; and I try to follow the rule: "When in doubt, always trust @Maine Sail."

Grotto · Jun 3, 2020

AaronD said:
That's one standard method. @Maine Sail's method is a little more subtle. He recommends drilling the holes at actual size, and removing a little core (with a dremel), so when you fill and then redrill, you end up with a tube of epoxy, bounded by the original skin on both sides. Equally water-tight, and possibly slightly stronger.

Quoting from his article:
"I prefer to leave as much of the top and bottom skin in place as is possible. Much of the strength of the deck comes from these skins so leaving them intact when potting a hole is the ta good practice. Leaving the top and bottom skins intact, without over drilling all the way through both skins, leaves you with a captured plug of epoxy that can’t physically pop out or break free as easily as a complete over drill of both skins can."

The whole article is worth reading. I haven't done any comparison testing of my own, but it sounds sensible; and I try to follow the rule: "When in doubt, always trust @Maine Sail."

Makes complete sense, I did both (overkill) overdrill and dremmel fill and drill

shemandr · Jun 3, 2020

I'm sure there must be a router bit to hog out the core material. That nail thing didn't work so good for me. Beat up the core pretty good but I was unconfident that I had removed much of it. I've look at bits and of course since the bit has to go thru a relatively small hole it has to be small. And it has to be asymmetrical so you can put the shaft against the top skin and hog out a significant amount. Anyone aware of anything like that? Ideally after removing the core you should treat the inside skins with a solvent to aid adhesion of the epoxy. Or at least remove the dust. Practically speaking it may be better to overdrill the lower skin to get better access for removing core and prepping the surface. If you don't get good adhesion and enough epoxy core the hole process is a waste of time.

rpludwig · Jun 3, 2020

keyhole bit or slot cutter router bit perhaps?
although I'd be hesitant to go at it with a router at 20k rpm....could easily get away from you!
maybe chuck said bit in a variable speed drill and have at it while under control....just my thoughts as a woodworker to hog it out...play with it on some scrap wood first.
(mlcs is a great source for bits & reasonably priced)

MLCS Key Hole Cutting Router Bits, T-Slot Cutter and Aluminum Insert for Slat Walls

MLCS Woodworking Key Hole Cutting and T-Slot Router Bits

www.mlcswoodworking.com

Hayden Watson · Jun 3, 2020

I used the 654 Dremel bit for potting all of my deck hardware and it worked great.