Hi Patrick,

Here's what I do:

First, I locate the hole above deck. From below deck, I use a hole saw of the appropriate size – for a 1/4″ hole, for instance, I use a 3/4″ or 1″ hole saw and remove the inner skin and core. That leaves just the outer skin.

Using a good duct tape (not a cheesy one), I tape over the new hole from the bottom. Sometimes, I'll put a piece of wax paper and a backing block.

I mix up some epoxy thickened a little with colloidal whatchamacallit stuff, and using a syringe I fill the hole and wait until it sets. Then I remove the tape or block and hey! Presto! Solid epoxy backing.

You'd probably want to do more than one hole at a time for this, though.

Bob

On Sun, Dec 14, 2008 at 3:34 PM, Patrick Walters < ([email][/email])> wrote:

I'm putting my plan together for installing a vent in my deck for the composting head and I know about drilling the whole, removing the core, blah blah blah, but in those instructions I think they are assuming a balsa wood core and we have a plywood core. I don't think a bent nail or allen wrench is going to be very effective. My thought was to use the dremel tool and a cutting disc which will work fine a for a big 3.75″ inch whole. But what have you all used with smaller screw size holes were a large cutting disc won't fit in?

Thanks,
-p

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s/v Deep Playa | Pearson 424 #152 | http://www.DeepPlaya.com
Patrick's Sailing Blog | http://www.shipsrecord.com/blogs/patrick

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Bob Fine
s/v Pelican
Hull #8

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Patrick,

My boat doesn’t have a plywood core. It’s balsa. Maybe there are a few plywood core spots – there should be in high stress areas – but I haven’t found them. All I’ve found anywhere in the deck & coachhouse is end-grain balsa core material.

In my opinion, it is not necessary to rout out the core around the edges of a large hole as you are discussing (and others here have said they’ve done). Instead, cut the hole you want just a shade large, like 1/16″ or maybe 3/32″ larger than the 3.75″, in your case. Then paint the inside edge, the exposed core material, all around, overlapping the fiberglass right up to the surfaces, with 2 coats of West epoxy. Let the first coat dry before you put on the second, a very light sanding in between. The thin liquid epoxy will penetrate the core, be it balsa or plywood, enough to seal the edges against any possible water intrusion. Then install the fitting, well-bedded.

That said, I do recommend over-drilling all fastener holes by several drill bit sizes or more. Then fill the holes completely with naturally thick (or else thickened) epoxy, let dry, then re-drill the correct size hole for the fastener right through the middle. Again, the core is 100% protected from water intrusion if the fastener ever leaks.

Tor
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Silver Heels, P-424 #17
http://www.SilverHeels.us
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Oops, I forgot the part about re-drilling. Do that. But as Tor said, for large holes you're good with two coats of epoxy. Make sure the thing going through the hole is well bedded or caulked, too.

Bob

—
Bob Fine
s/v Pelican
Hull #8

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One other trick for refilling fastener holes is to soak a cotton ball in epoxy, then after taping the bottom push the ball gently into the hole against the tape. The epoxy is less likely to find a path under the tape and drip into the interior (been there!).
Agree no reason to rout out the core for the large hole, just seal the edges. You only need to provide a hard core when there will be a compression load on the cored deck. If you actually have a plywood core there may not be any reason to re-enforce the fastener holes. Every where I've drilled a hole through the trunk cabin or the deck it has been balsa cored.

On Sun, Dec 14, 2008 at 4:21 PM, Robert Fine < ([email][/email])> wrote:

Oops, I forgot the part about re-drilling. Do that. But as Tor said, for large holes you're good with two coats of epoxy. Make sure the thing going through the hole is well bedded or caulked, too.

Bob

—
Bob Fine
s/v Pelican
Hull #8

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Regards,
John Stevenson
http://www.svsarah.com

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I have found that duct tape never works….. the epoxy eats it away. Softens it to a point where the resin just drips out….. and makes a tremendous mess. I have found that the blue masking tape works very well. Just the regular blue tape used for painting. For some reason the expoy (WEST) does not attack the adhesive. Go Figure.
alan

— On Sun, 12/14/08, John Stevenson <> wrote: