Drilling holes through stringers.

[ceol]

I would like to drill a couple of drain holes through a few stringers in the bilge area. Are there concerns with doing this? I see some holes in most of the other stringers. The holes will be pretty small, less than 1/2" in diameter.

Should I do a small test hole in the top of the stringers in question to determine their internal make up?

This is on an 84 Elite 29 CB.

Thanks,

G~

[Freesail99]

I drill 1/4 inch holes through a few fiberglass stringers myself. I don't see it as a problem.

[ceol]

Thanks,

I was just worried about possible lamination problems if water is now able to get into the stringer. I may very well be over thinking the problem here, I am very good at that.

G~

[Freesail99]

I always have epoxy around, I gave a quick wipe to the inside of the holes with some epoxy. That should take care of any potential problems.

[sailingdog]

ceol-

I'd pot the holes you drill through the stringers much the same way you'd do holes through a cored deck. If you drill them oversized and fill them with thickened epoxy and then re-drill the final hole, you should be fine. The thickened epoxy will help strengthen the hole and protect the stringer's core material from water intrusion.

[Freesail99]

From all I read you fill a hole with thickened epoxy and re drill it, to strengthen it. There is no stress on this hole. I can't see why coating it with epoxy would not stop any possible water issues.

[NOLAsailing]

Just brushing the interior of the limber hole with epoxy is very likely to leave some areas open for water intrusion. If you pot the hole and redrill through the thickened epoxy, there will be no exposed grain.

Filling a hole with thickened epoxy does not add strength to most laminates - it's purely a measure to prevent rot.

Rot is one thing you really don't want in a stringer, as the repair could involve gutting the boat.

[sailingdog]

Also, if you're using a metal snake to run wire, the snake can often chip off plain epoxy, thickened epoxy is much more resistant to chipping.

NOLA-

Thickened epoxy resists compressive loads much better than most cored laminates, and in that sense it does add strength to the area under load. Balsa, which is the strongest of the commonly used good core materials, will crush under a high compressive load, while thickened epoxy will not. Marine plywood has decent compressive load resistance, but is a lousy core material.

[Freesail99]

I really don't think that 1/4 or for that matter 1/2 hole or two will weaken any boat stringer. As far as wire chipping off epoxy, maybe. A big maybe. But the question was to drill holes for a drain hole, not to run wire. Wiping the holes & drilling them may take 5 minutes to do. Using thickened epoxy makes the job into a multi day job, when it doesn't need to be. I said before I used 50 grit belts on a belt sander and epoxy just torn those belts up. I really think it's a moot point, and your making a job take longer then it needs to be. Both ways will get the job done.

[NOLAsailing]

My point is not that the size of the hole will weaken the stringer, but rather that wiping down the interior of the hole is difficult to do perfectly and if it's less than perfect, then it will eventually rot from water intrusion. The only way to be sure it won't rot is to completely isolate the exposed grain inside the drill hole. This is not something worth taking the easy route on as a stringer replacement is no joke.

Yes, it is a mutli-day job, if you count the cure time, but the actual effort expended is negligibly more.

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SailingDog, good point - as usual - about the compressive strength.