Pinhole of light through hull. Best way to fix?

[kjdoyle1]

Hey all, while the boat is on the hard this winter we noticed a pinhole of light we can see through on the bottom of the hull. It's not a through hole but it's a bit scary. It's maybe 1/32 in diameter. We were thinking of drilling it a little bigger (let's say 1/4") tapering above and below and filling with epoxy. However, I see videos where they grinded it open to like a 2-3" hole and tapered it with the whole 12:1 ratio, then layered multiple layers of graduated fiberglass.

Of course I'm worried about rotting in the middle.

Can we do the simple drilled hole or do you think we need to grind and do the full 12:1?

-Kyle

 

[Alan Gomes]

Are you dealing with an actual physical hole or are you just seeing a small amount of light? Fiberglass will transmit light, but one normally does not see that because there is a backing coat of gelcoat that prevents it. Is it possible that the gelcoat is just missing there for some reason?

 

[shemandr]

If you are talking about below the waterline, I don't think the Hunter's have a wood core on the bottom. If not, you don't need to worry about wood rot. You could start to worry about water absorption into the fiberglass will cause degradation of the laminate instead.
On my Ranger 29 you could see light coming thru the topsides in places where the interior paint had flaked off. But Fiberglass after curing is kind of an opaque material that can transmit light.
If it's below the waterline I don't think you can enlarge the hole and just fill it. Sometime when you hit a wave that core will shoot out of the hull.
I would layer fiberglass from the outside using the 12:1 bevel. I would use epoxy instead of polyester resin and studiously following instructions available on the web sites of the resin venders,

 

[markwbird]

With a pin.

 

[thinwater]

More information. Photos. Pinholes don't just happen. Either the problem is bigger, or it is just a light transmission issue, as Alan suggested. I've seen that many times.

I would not make the problem bigger until I understood what is going on.

 

[dlochner]

More information. Photos. Pinholes don't just happen. Either the problem is bigger, or it is just a light transmission issue, as Alan suggested. I've seen that many times.

I would not make the problem bigger until I understood what is going on.

The real test is water. Does water come through the pinhole? If there is no water coming through the hull, then it is likely just a light transmission issue or perhaps a small air bubble in the layup. Can you take some good photos of the problem?

 

[Richard19068]

The real test is water. Does water come through the pinhole? If there is no water coming through the hull, then it is likely just a light transmission issue or perhaps a small air bubble in the layup. Can you take some good photos of the problem?

It's not a through hole but it's a bit scary.

He said it is not a through hole.

 

[rgranger]

I would layer fiberglass from the outside using the 12:1 bevel. I would use epoxy instead of polyester resin and studiously following instructions available on the web sites of the resin venders,

If this turns out to be more than just light…. I might take a different approach to what @shemandr suggested. The 12:1 grind flair is to provide enough surface area for the patch to mechanically bind to the old (cured) fiberglass while still being able to get the patch fair to the hull’s curve. If the exterior of your hull is not compromised I’d do this patch from inside. Fair less than 12:1… maybe a 4:1 patch followed up by a backing plate patch out to 12 that would “stand proud”.

 

[kjdoyle1]

Good points. Here is a closeup pic.

 

[thinwater]

I don't see any structural damamge. Maybe there is a small gouge on the outside, probably just through the gelcoat.

Fill with thickened epoxy, paint the bottom, and go sailing. If there is any grinding, it will be a minimal amount to clean up the gouge. I doubt fiberglass is needed, but that would depend on the exterior damamge.

Not scary. This sort of light show-through is not uncommon. That the laminate on the inside looks good is the good news.

 

[Davidasailor26]

What does the outside of the hull look like there? Looks to me like it’s just missing paint and gelcoat on the exterior, letting the light through the translucent fiberglass.

 

[dlochner]

Good points. Here is a closeup pic.

What does the paint or gelcoat look like on the other side? It sort of looks like an impact on the other side that has removed the paint or gelcoat. Are there spider cracks in the gelcoat?

 

[kjdoyle1]

Thanks guys for the responses! No, there are no dings or damage on the outside of that hole.

 

[Old Skool Neil]

The picture really helps. When the boat is molded, hull color and stripe color gelcoat is sprayed into the mold followed immediately by backup gelcoat, then the fiberglass laminations begin. The backup gelcoat was typically an amalgam of excess gelcoat left over from actual usage vs. minimum pail quantities purchased and became a gray-ish to olive drab color when mixed together in a storage drum. Its purpose was to increase the gelcoat thickness to specification and - germane to this thread - block light transference through the fiberglass. It would not do for a customer who just dropped the family nest egg on an expensive toy to see light shining through the hull, exactly as you have experienced here.

For whatever reason, there is a void in the intended opaqueness of the gelcoat where you're seeing light. If it's a result of damage it should be dealt with but other than that I propose you don't have a problem until the drill makes an appearance.

Other observations:

• There is no core material in the pictured lamination so there's nothing to rot, no worries.
• Before accepting it as fact I'd like to see some support for the comment "water absorption into the fiberglass will cause degradation of the laminate instead". If true, how could anyone sleep at night with a wet bilge?
• About the comment "it's not a through hole" in the opening post, forum posts often inaccurately call 'thru-hulls" as "through holes" so without further detail it could not be taken literally at the time. That's not a criticism of the opening post, just historical fact of forum vernacular.

 

[Alan Gomes]

The picture really helps. When the boat is molded, hull color and stripe color gelcoat is sprayed into the mold followed immediately by backup gelcoat, then the fiberglass laminations begin. The backup gelcoat was typically an amalgam of excess gelcoat left over from actual usage vs. minimum pail quantities purchased and became a gray-ish to olive drab color when mixed together in a storage drum. Its purpose was to increase the gelcoat thickness to specification and - germane to this thread - block light transference through the fiberglass. It would not do for a customer who just dropped the family nest egg on an expensive toy to see light shining through the hull, exactly as you have experienced here.

For whatever reason, there is a void in the intended opaqueness of the gelcoat where you're seeing light. If it's a result of damage it should be dealt with but other than that I propose you don't have a problem until the drill makes an appearance.

Other observations:
There is no core material in the pictured lamination so there's nothing to rot, no worries.
Before accepting it as fact I'd like to see some support for the comment "water absorption into the fiberglass will cause degradation of the laminate instead". If true, how could anyone sleep at night with a wet bilge?

Thanks, Old Skool Neil, for providing the details that might help others when confronted with this situation.

Since I know Neil from other contexts, I thought it would be helpful to add something that he didn't mention, and that is that Neil used to work for some of the major boat builders in Southern California back in the '70s. So he was involved in the process he describes at that time.

 

[mikeracca]

Good points. Here is a closeup pic.

Im not seeing a hole here. I see light, but no hole. The glass on this side looks good and there is no wood or cork or any thing to rot at this point in the hull. Now what does the other side look like? That is the $65,000 question here. If there is a chip in the paint/gel at this point then feather sand the area around this back and fill with Fairing compound Then spray new gel coat, or use thickened gel coat as the fairing compound and wet sand and buff to a nice shine, repaint bottom as needed. paint isn’t good at sealing water so please seal with gel coat or another sealant. Epoxy and polyester are also not good at sealing out water.

If there is damage to the hull here, then the correct way to fix is to dig it out some and refill it with new glass and some polyester resin. That’s what was used to make your hull and it should be used to fix your hull for best results, less chance of an incompatibility later down the line. Once filled then fair it out and redcoat as described above.

If you do run into delaminated glass as you are digging the hole out keep going… go till the glass is solid again and then just a bit further before you stop. Fill and fair as above.

 

[Alan Gomes]

It's highly likely that you don't have a problem here and that you don't need to do anything at all. I certainly would not start busting out the drills and grinders at this point. But whether you are talking about this or any future hull repairs, it is not true that polyester resin would be the best for such repairs. The fact that the boat was made with polyester is not the point, because you are talking about a secondary bond. For that, epoxy would be a much safer bet, as new polyester does not bond especially well to already cured polyester.

 

[Davidasailor26]

I agree with. The other advice to not go poking at it and opening it up. That will only make things worse.

With regard to epoxy, polyester, and gelcoat - epoxy followed by antifouling would be the preferred method for a place like this. Epoxy provides the strongest bond to the underlying material, regardless of what it’s made of. Epoxy is also the most waterproof option, so best for below the waterline use. Gelcoat is polyester based, which is what allows blisters in older boats. The downsides of epoxy are that it’s harder to get polyester based gelcoat to stick to its surface, and it’s not UV resistant. Both of those are non-issues below the waterline where you can use antifouling.

 

[jnorten]

My Catalina hull below the waterline is solid glass. If your Hunter is similar, then like others have said you shouldn't have rot to worry about. Along the lines of Catalinas, many of my vintage (early 80s). . .if you know where to look in the nooks and crannies. . . definitely transmit some light.

 

[shemandr]

...Other observations:
Before accepting it as fact I'd like to see some support for the comment "water absorption into the fiberglass will cause degradation of the laminate instead". If true, how could anyone sleep at night with a wet bilge? ...

There have been numerous articles about the osmotic intrusion of water (Particularly fresh water) into the fiberglass laminate. A quick google turned up results relating to fiberglass pools. I wouldn't exactly call that evidence but that's about as much time as I'm going to put into defending a statement that I made (Merely to suggest that because there is no wood core there isn't a risk of water intrusion). There has been a lot published about the need for barrier coats below the waterline when the original gel coat is compromised. The reason as I see it is to protect the laminate.
The inverse question is interesting. “Is the whole barrier coat industry a fraud?”