Fiberglass crack

[paxchristus]

I have a 3 inch hairline crack below the roof of my 10 year old RV due to an awning breaking off. Awning repair guy wants to drill a hole at the bottom to prevent spread and fill/cover it with Par Bond. Does this sound like a reasonable fix? Mike

[Perry J]

If you don't drill the hole the crack will continue to get longer

[Art VanDelay]

It's called STOP DRILLING. Just drill the hole then push some calk in it.

[D White]

I disagree about the hole drilling thing. If the force that was causing the crack is no longer there, it won.t continue to crack. If the force is still there, it will continue to crack, hole or not....Dave

[fusedlight]

Waving my arms in the air here a bit (my family calls it "facts by Brown") I would posit that even if the initial downward force was NOT there the crack could still propagate due to vibrations in the trailer during towing. The fiberglass on either side of the crack will vibrate at a different rate and the crack will elongate even in the absence of a vertical load.

As to the hole stopping the propagation... makes perfect sense (see my arms waving??). The biggest point of stress is at the bottom of the crack. ALONG the crack there's not much stress. Putting the hole in and filling it with a strong dollop of goop will "lock" that point in place so it doesn't experience the splitting force that's caused by the vibration in the first place.

[kirkman]

Try this first!!!!
Capt. (Captain) Tolley's Creeping Crack Cure Hairline Crack Sealer 603-435-7199-

[Bob Miller]

Standard practice in plexiglass aircraft windshields used to be (and may still be) drilling a stop hole at the end of any cracks. As mentioned, as soon as there is a crack, entirely different sets of stress go to work.

BTW: Capt Tolley's stuff works, I've used it for years, but still, drill that small hole to stop things.
"Drill Baby Drill"

[D White]

Originally Posted by Bob Miller

Standard practice in plexiglass aircraft windshields used to be (and may still be) drilling a stop hole at the end of any cracks. As mentioned, as soon as there is a crack, entirely different sets of stress go to work.

BTW: Capt Tolley's stuff works, I've used it for years, but still, drill that small hole to stop things.
"Drill Baby Drill"

This is fiberglass, not plexiglass...it has weave crisscrossed everywhere...Why would you want to drill a leaking hole in and area that is only cracked, and not leaking???

[Bob Miller]

Easy Answer, because it stops the crack from moving further. We also would drill a stop hole in Corvette fiberglass cracks before repairing. The strands from the chopper gun will help keep the area intact, but they don't always stop the crack from continuing in the resin.
That worked on my first Corvette, a 1954, and my last Corvette, a 1989, all of which are famous for developing cracks in the fiberglass. Not to mention 2 Meyers Manx's, a Meyers SR-II and about 4 Toyota Sunraders.
This is for cracks in the fiberglass, not spider web cracks, that usually are only in the gelcoat.
BWT: If drilling a 1/8" hole creates a leak problem, fix the crack and the hole, at least the crack won't get bigger.

[nlife]

Same principle works on leather too. A clean, punched hole in a belt doesn't tear like a jagged hole made with a nail.

[D White]

Originally Posted by Bob Miller

Easy Answer, because it stops the crack from moving further. We also would drill a stop hole in Corvette fiberglass cracks before repairing. The strands from the chopper gun will help keep the area intact, but they don't always stop the crack from continuing in the resin.
That worked on my first Corvette, a 1954, and my last Corvette, a 1989, all of which are famous for developing cracks in the fiberglass. Not to mention 2 Meyers Manx's, a Meyers SR-II and about 4 Toyota Sunraders.
This is for cracks in the fiberglass, not spider web cracks, that usually are only in the gelcoat.
BWT: If drilling a 1/8" hole creates a leak problem, fix the crack and the hole, at least the crack won't get bigger.

Sorry, I build Corvettes professionally (for 35 years) and I guess we need to agree to disagree, and I consider this bad advice

[kirkman]

I build and paddle fiberglass kayaks and I have to agree with D White I would never drill a hole in a crack in fiber glass. I have never had a crack in a fiberglass boat keep progressing.

[RogerDat]

Wouldn't it make a difference how the crack was patched?

I'm thinking that if one is patching the crack by sanding out an area on either side of the crack, laying in mat and resin and essentially rebuilding the structural integrity of the area it would be different than if one was just scaping a shallow V in the crack and filling with resin.

I'm not experienced in FG repar the way some of the poster are but I think the west marine online guide for fiberglass repair suggested the shallow V and resin for minor cracks and suggested drilling a small hole at the crack end.