Drill and Fill Questions

[Rumdoctor]

Is there a rule of thumb or recommended amount to overdrill? I.e. if there is a 1” diameter fitting, what diameter should you overdrill.

When filling the over drill with the epoxy, do you thicken it with wood flour? Thicken with something else?

[Fuzz]

I think the general rule is make the hole 1.5 times the fastener size. 1" hole needs 1.5" over drill.
I use wood glue for almost everything but if it is in an area where very high loading is expected you can add other stuff glass fibres being one of them. Just do not use something soft like a fairing compound.

[Jaysen]

I think there’s a difference between loaded and unloaded holes though. EX: a through hull vs a screw hole.

Am I wrong about that?

[Rumdoctor]

Specifically, I was interested for my transom drain tube, bow eye, and cleats.

[Jaysen]

Will all be through bolted or some screwed/lagged?

I ask because I think (which is dangerous) that through bolt holes only need to be a bit larger than the bolt with epoxy not being structural (more of a seal)(give room for redrill inaccuracies). The lagged/screwed holes need to provide structural support to the threads.thats where the 1.5x plus glass, wood flour, cabosil, etc comes in.

Someone correct me if I’m wrong about all that. Wouldn’t be the first time. Today. According to wife.

[piperdown]

Now this has me curious. Would it also depend on the size of the hole whether to cut cloth to place in and epoxy over? Still learning myself.

[icelikkilinc]

IMHO, the over-drill and fill is to avoid rotting...

It helps with strength but when you talk about cleat or bow-eye, you need to divert the forces by using backing plates and under structural supports, not relying screw only.

[TomW1]

IMHO, the over-drill and fill is to avoid rotting...

It helps with strength but when you talk about cleat or bow-eye, you need to divert the forces by using backing plates and under structural supports, not relying screw only.

The main purpost is to prevent rot. It also adds some strength to the wood when mixed with wood flour. The 1.5 over drill is correct for all holes.

Tom