Fiberglass hole fill

[larman]

I damaged the keel of my boat when I hit a submerged rock. I sanded and grinder out the area and I am left with a 4 inch area that needs to be repaired. There is a hole about 1 inch by 3” deep that needs to be filled. The hole is not totally thru there is still somelayers of fiber left. Can I use thicken epoxy? What is the best way to do so?

 

[psneeld]

When my bilge was full of water and my hull full of blisters plus delamination.....I would up grinding through and created a similar hole.

I built it back up as just using filler just didn't seem like a proper repair as I have never seen "how to" recommendations to use filler on that big of a hole.

Not sure it would be near as strong either and I worried the next hit of just sitting on a block in the yard may pop it loose.

 

[Bacchus]

Agree with psneld that you need to build it back similar to how the hull was constructed using fiberglass as well as resin (either polyester or epoxy).
I'm no fiberglass expert but have done some repairs.

I could not tell the shape / size of the area now needing repair from the picture but generally the recommendations I've seen are to taper the area (4:1 OK but more is better. If the hole is through the hull it should be a 2 sided repair doing the same on the inside.
Start cutting small discs of glass and make each layer slightly larger. You should be able to do several layers at one time. Be sure to finish slightly below the desired finished surface so you can fill and fair the final surface. You don't want it overfill needing to grind it off and expose fibers.

There are likely how to videos online that may be helpful and I'd use their ratios vs mine if you find a difference.

 

[larman]

Agree with psneld that you need to build it back similar to how the hull was constructed using fiberglass as well as resin (either polyester or epoxy).
I'm no fiberglass expert but have done some repairs.

I could not tell the shape / size of the area now needing repair from the picture but generally the recommendations I've seen are to taper the area (4:1 OK but more is better. If the hole is through the hull it should be a 2 sided repair doing the same on the inside.
Start cutting small discs of glass and make each layer slightly larger. You should be able to do several layers at one time. Be sure to finish slightly below the desired finished surface so you can fill and fair the final surface. You don't want it overfill needing to grind it off and expose fibers.

There are likely how to videos online that may be helpful and I'd use their ratios vs mine if you find a difference.

Ok I will continue layering it with fiberglass. I cannot access from inside the boat.

 

[psneeld]

Ok I will continue layering it with fiberglass. I cannot access from inside the boat.

2 sided build up is preferred but not necessary....especially if there is some existing laminate still there.

 

[larman]

Can you use a product like Thixo to build it up followed by fiberglass mat?

 

[SIBERNUT]

Used to be a product "Tiger Hair" we used for big holes, Google it

 

[psneeld]

Can you use a product like Thixo to build it up followed by fiberglass mat?

I would not use Thixo as a filler...I would lay up layers of a glass product with resin.

Tiger hair is polyester resin based I believe, if they upgraded to an adhesive vinyl ester then disregard, and while a great product with either resin, I would not use on holes that span much more than an inch and not as a underwater patch.

 

[Comodave]

I would grind a taper, 12:1 is the recommended taper. So if it is a 1/4” thick you should grind out 3” and so forth. Then I would only use epoxy resin since it will stick better in a secondary bond than poly resins. I would use something like 1708 glass to build it up. When you get close to the finish depth use thickened epoxy by mixing in a filler.

 

[Southern Boater]

I would grind a taper, 12:1 is the recommended taper. So if it is a 1/4” thick you should grind out 3” and so forth. Then I would only use epoxy resin since it will stick better in a secondary bond than poly resins. I would use something like 1708 glass to build it up. When you get close to the finish depth use thickened epoxy by mixing in a filler.

What you describe is certainly the industry norm, but the controversial method seems to be, do you place the small patches of fibreglass in the hole first, building to the largest patch last, or visa versa?
Watching videos from “pro’s” they appear to favour the largest patch first, followed by progressively smaller patches to the outside, stating the largest patch first concept, binds all the hull laminates to the firstly laid piece of mat.
Andy from Boatworks Today prefers the small to large process, as you would know.

 

[NightCrawler]

Rookie tip. Don't mix up too much resin. I made up a small coffee can of mix to quickly put down with a roller on a new runabout floor. Third time I hit the can with the roller the pot was hard as a rock. The resin had kicked off. So of course, upset, I grabbed the can with my bare hands. Resin generates a good deal of heat when there's a lot of it playing in a container. Had to pay the deductible when I dropped the can over the side onto a new car parked in the garage next to the boat on a trailer. . .Insurance agent said your issue is not listed under 'accidental' items. . .wait, it's over here under StoopidStuff. So it's not covered.

 

[Southern Boater]

Rookie tip. Don't mix up too much resin. I made up a small coffee can of mix to quickly put down with a roller on a new runabout floor. Third time I hit the can with the roller the pot was hard as a rock. The resin had kicked off. So of course, upset, I grabbed the can with my bare hands. Resin generates a good deal of heat when there's a lot of it playing in a container. Had to pay the deductible when I dropped the can over the side onto a new car parked in the garage next to the boat on a trailer. . .Insurance agent said your issue is not listed under 'accidental' items. . .wait, it's over here under StoopidStuff. So it's not covered.

I reckon most first timers mix too much resin initially, especially after watching YT videos, same with 2K paint, there must be so much product wastage, besides all the “disposable” by-products like brushes, rollers, paint trays, mixing cups, gloves etc….

 

[jgwinks]

You can slow the resin kicking off in the pot by pouring it into a shallow, flat container like a roller tray or even a disposable foil baking pan. The added surface area will allow the heat to dissipate preventing the thermal runaway which causes the premature cure. If I'm applying to a large horizontal surface I try to pour all the resin out onto the surface then even it out with a roller. The sooner you get it out of the mixing pot the better.

 

[Comodave]

You can also put ice under the container with the resin in it. Also be careful if you throw away a container with uncured resin in it. It can go thermal runaway and possibly start a fire in your trash. I usually set the container on a concrete surface for some hours to let any heat dissipate before throwing it away.

 

[TJM]

Yes, the exothermic chemical reaction generates the heat as a by product, not a requirement. Cool it down with surface area.

 

[grandbanksbayfield]

I agree with the guys who recommend layers of cloth and epoxy. Fair it out like Commo Dave recommends and then put a heat lamp on it for a few days. One can put on a new layer every hour or so but too much too fast can build up enough heat to blow the whole job. If you let the patch sit overnight, scrub off the last layer with warm water to get rid of the amine blush that forms on epoxy as it cures and prevents adhesion. A hairdryer is great for drying something that is wet for a short time, like a quick rinse. For fairing, use Gougeon Bros (West System) 407 milled fiber followed by a skim of 410 phenolic beads. Never use colloidal silica for fairing. It is almost impossible to sand.

 

[DNT99611]

First thing it to get the keel iron out of the way. You can not do a proper job with it there. You need to remove enough glass so you get back to good glass and all signs of delamination are gone. Tip: a tile cutting blade on a 4.5 inch grinder goes through glass like butter. Grind things well and then use pore foam to fill the hole. That can be shaped very easy so you have something to laminate against.

 

[grandbanksbayfield]

Final Suggestion

I damaged the keel of my boat when I hit a submerged rock. I sanded and grinder out the area and I am left with a 4 inch area that needs to be repaired. There is a hole about 1 inch by 3” deep that needs to be filled. The hole is not totally thru there is still somelayers of fiber left. Can I use thicken epoxy? What is the best way to do so?

You certainly have received an incredible amount of good advice from all of the people responding on this forum. One last thought: It is more expensive than polyester or vinyl ester resin, but the Gougeon West System is by far the easiest to use. The little pumps allow you to mix small batches as you go, avoiding over-heated resin and other problems. It eliminates waste and makes life easier. A gallon should do it with some left over and then you will have a some left over to do projects around the house.

 

[fgarriso]

You may want to think about a lay up schedule. That is alternating layers of glass mat and then cloth. Map will go into rough areas so you can roller out the air bubbles.

 

[Comodave]

I like the support that West Epoxy has. Whenever I have called them they have been very helpful.

As to the mat and glass layup I usually use 1708 which is 2 layers of glass and one layer of mat. Chopped strand mat doesn’t work well with epoxy resin but the mat in 1708 does play well with epoxy. It is sewn to the glass rather than having a binder to hold the mat together.

 

[DNT99611]

Epoxy is not a substitute for good prep work. A good quality iso or vinyl ester with good prep will do just fine. My buddy just stretched his 37 foot Delta that had been stretched 5foot before using epoxy. He was able to get a nail bar under the epoxy and pop off large hunks of the epoxy laminate. Best we could tell was poor prep was the problem. In this case it looked to have been sanded way too fine.

 

[ronobrien]

Rookie tip. Don't mix up too much resin. I made up a small coffee can of mix to quickly put down with a roller on a new runabout floor. Third time I hit the can with the roller the pot was hard as a rock. The resin had kicked off. So of course, upset, I grabbed the can with my bare hands. Resin generates a good deal of heat when there's a lot of it playing in a container. Had to pay the deductible when I dropped the can over the side onto a new car parked in the garage next to the boat on a trailer. . .Insurance agent said your issue is not listed under 'accidental' items. . .wait, it's over here under StoopidStuff. So it's not covered.

When working in summer I have poured the resin into a paint tray and then placed that tray into another larger tray with ice in it. The ice draws off the heat to slow the kick.

 

[Comodave]

Epoxy is not a substitute for good prep work. A good quality iso or vinyl ester with good prep will do just fine. My buddy just stretched his 37 foot Delta that had been stretched 5foot before using epoxy. He was able to get a nail bar under the epoxy and pop off large hunks of the epoxy laminate. Best we could tell was poor prep was the problem. In this case it looked to have been sanded way too fine.

Any product can fail without the proper preparation. One instance does not prove that epoxy isn’t the best resin.

 

[PierreR]

I prefer a two sided approach

My neighbor next to me (dirt home) developed a leak in his boat after an encounter with a concrete dock. My neighbor has a 34' SeaRay and was waked hard when pulling up to a concrete dock. The wake picked up his bow and surfed him down onto the dock. Knowing his insurance company would total the boat he asked me if I could do a cheap quick repair. I said the boat was structurally compromised and would not be cheap. None the less I charged him about 10% of what the yards would charge him.
These photos show the hole after grinding out the delamination. Of course there was no actual through hole before grinding so he could not watch. I fabricated a stem out of Jatoba and a stainless strap at the top to hold it in place. Then I glued 3/8" Divinicell coring to the edge of the hole and the slot built into the stem. The second photo show partial lamination with ounce and a half biaxial weave starting small to large on both sides. The inside layers being slightly thinner than the outside layers.
When out flush, I faired with a compound made from epoxy resin, talc and burnt rice hulls. Burnt rice hulls are a form of fume silica and carbon fibers and is literally rice hulls that have been sintered. Fabulous stuff for fairing in my opinion but probably not attainable to the average person. I use Raka epoxy 127 and 350 non blush harder. I roll on layers with a 4" roller, short nap or foam. Raka's wet out properties are fantastic and cloth gives me a high glass to resin ratio. My last layer is matt as that has high resin content.
I refused to try to match paint and paint the hull so my neighbor does the Krylon spray bomb job on it (Face Palm) and that is the final photo. My first attempt at pictures.

 

[PierreR]

Ahhh, not to good

 

[RickyD]

My 1974 Ericson 32 sailboat had the worst blister problem imaginable. It had a blister in every square foot. Bought it well below market value in 1986 and after grinding off the gel coat and blisters we bagged and dried for three months then faired and covered with 8 coats of West System epoxy. We could do two coats a day/weekend, then have to lightly sand the entire bottom to accept the next two coats. We used the microballoon thickener for the blister buildup. I didn't get another blister for 12 years. Then it was two on the rudder. Then one or two over here or there every three years. Never a real problem again. Very easy to use.

 

[DNT99611]

Any product can fail without the proper preparation. One instance does not prove that epoxy isn’t the best resin.

I was not saying epoxy is not the best resin. I am saying its better properties will not make up for poor prep. The time I was speaking of is not the only time I have seen it, just the worse.
Also when building up a 1/2 inch of glass or more for a keel area there is nothing wrong with using a good quality ester resin. I am just finishing up fixing a 2x6 foot hole in a boats keel. Epoxy was not my choice for that job.