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Fill-n-drill on a vertical panel?


meester

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HI All,

 

I'm hoping that some of you experienced builders will have a trick for this.   Bolt holes for the lower gudgeons and pintles will be in the water a lot, and the wood should be sealed up to avoid rot.   See?  I'm learning!

 

I'm thinking of making little cup-shaped covers out of masking tape, filling with liquid epoxy and trimming off the excess when it's still green.  Could be messy.

 

Or, I could "paint" the inner surface with neat epoxy and then fill with cabosil-thickened stuff.  I've noticed that the cabosil-thickened stuff will dull my plane blade.  Would it also be hard on drill bits?

 

Hints?

 

Bob

 

 

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The "bullet proof" solution in this situation-in my opinion- is to drill an over size hole, fill with thickened epoxy and then re-drill for the bolt. You'll end up with a solid epoxy bushing that is just about guaranteed for water resistance. Works even better under 'glass. Good luck -PeterP

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Is the panel already vertical or not yet installed?

 

If not yet installed.....simply drill your hole oversize (my preference is to leave at least 1/8" margin, so 1/4" larger hole than needed. If the hole is really big, an even larger bushing of epoxy. Maybe as large as 1" drilled hole for a final bolt hole of 1/2".....or a 1/4" margin for your epoxy bushing. But if still flat, drill your oversized hole, tape the backside and pour slightly thickened epoxy in the hole.....leaving it just a bit proud. It will shrink as it soaks into the edge grain of the plywood and will also shrink a bit as it cures. Too proud and you get to sand off the surplus. BTW, when I mark out the hole, I don't do it with a little + to mark the center but a big one that has the ends extending beyond the margin of the pilot hole. So when you are ready to re-drill, you can find the center again. Also, if the marks for this hole are on the taped side, you won't sand them off when you sand the proud pour back down to flush.

 

If the panel is already vertical, all is not lost. Same pilot hole, same marks, etc, but this time you put tape over both faces and inject the thickened epoxy in with a syringe and needle. With both sides taped up solid to the top of the hole, drill two small pilot holes into the top of the hole from above. Angle it in.....actually, drill two of these. One is to be used to inject the epoxy, the other is to let the air out. When the air hole fills up and epoxy oozes up and out, the taped up hole is full. When you are done, the epoxy bushing is poured and both pilot holes are sealed.

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Hi Gents,

 

Thanks for your thorough responses.  In my case, it's the transom, and it's already installed.  I have done a number of these fill-n-drill bushings on the horizontal, but these will the the first vertical ones.  I see the importance of an extra hole to let the air out.  I think I'll work on a variation of that plan.   The oversize "+" mark tip is a keeper.  

 

My great uncle once said, "There's more than one way to drown a cat in a boot full of warm milk."

 

Bob

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On difficult to fill holes like yours, consider a syringe and taping both sides of the hole. On the side that faces up, pinch the tape at the top, so there's a significant wedge shaped opening and use a syringe, to inject goo into the hole, until it's nearly overflowing the pinched up portion. This can be ground flat after it cures. The syringes I use come from a feed store, about across the street from me, but veterinary supply stores carry them too. 

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Academic curiousity for me, but would you use straight epoxy to fill this vertical hole, or add something? Obviously the goop must be thin enough to squirt and flow, but would any additives improve its performance?

Again, I'm not using this technique in the foreseeable future, but I am curious about everyone's experience and opinions.

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From a technical standpoint, every time you add something to straight epoxy, it changes the physical attributes and nothing is free. What this means is you might increase its hardness, but also make it more brittle or you might improve abrasion resistance, but lose some elongation, etc., etc., etc.

 

On a transom hole like this I would make a fairly thin mix, using milled fibers and/or cotton flock (for bond improvement) with some silica to control viscosity. The syringes I use do require the mix is a little runny, but not as much as you think. It's the size of the syringe barrel and the tip that makes this possible. The 60 ml syringes (the biggest I usually use) have a 1/2" diameter tip, so you can shove pretty thick stuff through it. You just spoon it in from behind, insert the plunger and squeeze. Makes doing lapstrake seams a whole lot easier, let me tell you.

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I second PAR's technique with a slight modification. I like to tape both sides of the hole and rub the tape nice and tight. Then i use a pin to make very tiny holes about 6 of them around the outer perimeter of the hole through the tape on both sides. Then I make one slightly bigger hole in the middle on the side where you'll use the syringe. When you inject the thickened epoxy it fills all the way to the edge and you can see the little worms squirt out of the tiny pin holes. Works good for me. 

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I guess I have been getting away with the simple solution all these years by using thickening epoxy with just enough cab o sil to hold shape.  The thin epoxy solutions mentioned surely work fine but seem way too much trouble when none of the many - many holes done with thicker epoxy have ever leaked or given any trouble.  That includes many stanchion and stay through-deck repairs, outboard mounting transom holes, transducer holes, lacing holes for trimaran tramps, rigging line fairleads and various others.  Just fill the hole a bit proud and scrape off excess with squeegee and its done.  Slathering on some thin epoxy on the interior is good for a belt and suspenders job but not critical.

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I've done it Tom's way too plenty of times. Just enough to hold shape and use a putty knife on both sides going back and forth, back and forth until both sides are filled nicely. You can always fill it twice within the curing window to get it nice and level, doesn't have to be perfect on the first go. 

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BTW, there is a secondary benefit to epoxy bushings beyond water intrusion. If bolts and nuts with washers are involved, it becomes a compression bushing to prevent compression of the wood when you tighten the nuts. Epoxy is rough on wood cutting tools, but drill bits will survive it just fine.

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HI All,

 

Thanks for all the great advice.  Howard's comment about the epoxy acting like a pressure bushing lit up my light bulb.  Slowly, like a cold flourescent.  Bzzz.. Glow.  Blink. Blink.  The epoxy bushing gives mechanical strength, not just sealing the wood, so it's good to make the walls thick.

 

Bob

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