Drill-fill-drill: Epoxy cure time and hole diams?

 I drilled 4 holes in my duckling aft deck for a padeye today and filled them with wood flour-thickened epoxy. I'm using #8 silicon bronze wood screws (5/8" long, I think). The hole (epoxy plug) diameters, 5/16", are twice the screw thread outer diameters, which seemed to be roughly what Gougeon Brothers recommended in their epoxy tome for smaller fasteners (though my eyes glazed over since they cover many different options). CLC's drill-fill-drill tip suggests letting the epoxy cure, but I'm looking for clarification. It seems like it might be ideal to bed the screws while the epoxy is curing, soft enough to accept screws, and maybe even capable of bonding with the screw threads to some extent (though the obvious downside, if any bonding were to occur, would be difficulty of removing the screws later). Should I instead wait a weeknir two for the epoxy to ~fully cure and screw into it when it's rock-hard? Either way, how should I determine the diameter of holes to drill in the epoxy? Same as for pre-drilling into wood? Apologies for the poor formatting - my phone can't add newline characters, apparently.

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RE: Drill-fill-drill: Epoxy cure time and hole diams?

 Should I wait a week or* two to let the epoxy fully cure, that is.

RE: Drill-fill-drill: Epoxy cure time and hole diams?

I go for a 24-hour cure (normal temps) before the second drilling.

For padeyes, I've taken to rolling up a scrap of glass cloth, saturating it with epoxy and pushing it into the screw hole. It gives the threads something more substantial to grip than epoxy. It's especially useful when repairing a hole where the screw threads have pulled out and shredded the wood.

Laszlo

 

RE: Drill-fill-drill: Epoxy cure time and hole diams?

Thank you, Laszlo. Now that you mention it, I remember seeing the bit about fiberglass on your blog. Do you remove deck fittings like padeyes when you are refreshing the varnish or simply work around them? Guessing the latter. Given that the padeye will be my anchor point for the stern cartopping tie down, I would hate to back the screws out even once after bedding them and weaken the attachment.

RE: Drill-fill-drill: Epoxy cure time and hole diams?

I take them off. The epoxy is for waterproofing, the glass/epoxy is for providing something for the screws to bite into. For bedding there's silicone compounds.

Laszlo

 

RE: Drill-fill-drill: Epoxy cure time and hole diams?

Well here's a first. Laszlo and I don't agree. Wow, that's never happened before.


I hate the redrill portion of drill fill drill. I never seem to get the second drilling centered in the original hole. And it requires a frustrating day of waiting. I often will let the epoxy cure around whatever is going to ultimately go in the hole. If I'm worried about release, I rub a little candle wax on the object or use mould release. If the epoxy grabs a fastener I apply some heat directly to the object in the form of a soldering iron then back it out. An impact driver carefully applied can be your friend by that tapping impact. You can also break the head off of your fastener if you're not careful. That is a TOTAL pita.
One does have to be careful to make sure what ever object you’re putting in the hole stays centered in the hole! Painters tape or some creative jigging has worked in the past.

RE: Drill-fill-drill: Epoxy cure time and hole diams?

i was reading this and thought there were some interesting perspectives and that i could add something.  first, we probably should have started with the question. what kind of screw were you going to use to attach the padeye?

fwiw, i only drill, fill, drill when i am using a machine bolt (e.g., a bolt that's going through the hull that is going to get backed by a washer/nut. 

if i am going to be working with a wood screw into a block of wood, i drill the hole in the wood approriate for the wood screw, put the wood screw in, back it out, fill the hole with epoxy and then wood screw in and back it out....and then let it cure.     when the final wood screw goes i, silicone on the screw.

for my drill/fill/drill machine screw technique i look for at least a 1/8 inch 'rim'.  so a final hole is always a 1/4 inch more than the target.  i agree that centering it can be a pain.  i handle that by doing a pilot hole for the final hole with a finish nail or 1/32 bit....which is fairly easy to center...then follow it up with the actual bit for the final hole.

anyway, i hope that is helpful.  

h

 

 

RE: Drill-fill-drill: Epoxy cure time and hole diams?

Really appreciate the detailed replies. I need to take some time to digest them, but to answer hspira's question, I was planning to use #8 x 3/4" or 5/8" silicon bronze wood screws only because that's what CLC seemed to recommend along with the padeye. It seems like a machine screw or a through bolt might be better in terms of mechanical strength, though. I backed that part of the kayak deck (4 inches in front of the stern) with an inch or so of thickened epoxy as recommended in the manual (I think). I'm mostly interested in strength (of the padeye connection) rather than the ability to remove the fasteners later. Usage will be mostly in fresh water but also in sea water a few times a year, but I will store the kayak in an attached garage.

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