Let's talk fiberglass repair

As I mentioned in the last few posts of my boat thread, I have a crappy fiberglass repair I need to knock out.  I'm not really even sure how the P.O. did this bad of a job.  The fabric wasn't even impregnated with resin.  I don't even know if this stuff is resin.

Is there a particular product that is going to work better for this than other stuff?  Any modifications to the normal process I'll need to use?  Grind it back 6-8" in all directions, then start laying everything in?

Initial pics: https://grassrootsmotorsports.com/forum/grm/the-worlds-most-expensive-boat/183460/page3/#post3264103

After removing the crap:

Crappy fiber

Edit: To make sure everyone is on the same page, here's the area in question with light behind it at night.

This guy is very good. He's a bit of a talker and will recommend the products that sponsor him but his workmanship is top notch. 

https://www.youtube.com/user/boatworkstoday

He primarily uses polyester resin. 

I have been that route before and it worked great for about 10 years. At this point, I would use epoxy for the resin. It's what I used on the jet boat. 

Oh, and buy some Tyvek suits. There isn't much on this planet that I like less than grinding fiberglass. A Tyvek suit with hood and gloves, with the sleeves taped, at least makes it bearable. 

A hot shower and a credit card will get the rest of the fiber out of your skin. 

Repair the boat with the same type of resin that it was made with. You'll get a better bond that way. I'd grind it back in a circle around the hole, lay up multiple layers of 6oz cloth, squeegee out all the excess between each new layer added. Next I'd hit it from the other side with the grinder and at least one layer of cloth so you've got the ding repaired from both sides. After fiberglassing mix up a batch of resin with a tiny bit of paraffin wax in it. If it's poly that'll help it cure and make it easier to sand. If it's epoxy that'll make it a little easier to sand. Brush that layer on. If polyester mix the batch a little hotter so the resin only has time to self level but not enough time to thin out and run off the repair area.

Toyman01 + Sized and said:

Oh, and buy some Tyvek suits. There isn't much on this planet that I like less than grinding fiberglass.

That's one thing I was wondering about.  The hull is relatively level in this spot.  The grinder won't be throwing the excess out at any weird angles.  I was wondering if I could grind it down with a little trickle of water running across it to prevent dust from flying up, and that way I'd just need a respirator, face shield, and mid-bicep length gloves.  

buzzboy said:

Repair the boat with the same type of resin that it was made with. 

Boat was made in the mid-late 50s.  I doubt there is anyone available to tell me what the resin actually was.  Hell, most of the links you get on this boat are my posts.

Still, might be a way.

In reply to Mr_Asa :

That's not something I've ever tried but you don't want to push water down into the laminate. It will take forever to dry out and if it's not dry the new resin won't bond well. I usually clean with acetone before I grind just to make sure there aren't any contaminants on the surface that might get smeared into the base layer. 

FYI, epoxy bonds to polyester resin without issue. Polyester resin does not bond to epoxy.  Most epoxy is not UV stable. If you go that route, make sure you paint it. 

Mr_Asa said:

buzzboy said:

Repair the boat with the same type of resin that it was made with. 

Boat was made in the mid-late 50s.  I doubt there is anyone available to tell me what the resin actually was.  Hell, most of the links you get on this boat are my posts.

Still, might be a way.

If it's fiberglass from the 50s, it's a polyester resin. Epoxy will stick to it just fine if you want to go that route.  

Toyman01 + Sized and said:

In reply to Mr_Asa :

That's not something I've ever tried but you don't want to push water down into the laminate. It will take forever to dry out and if it's not dry the new resin won't bond well.

Its already fairly well soaked just due to how I've been cleaning it out.  I'll have to look at some way to dry it out properly.  Having said that, its been nice and dry here in Florida for a while.  Saying that though, it'll probably rain for a week straight after I get the parts for this.

In reply to Mr_Asa :

Several days of hot and dry weather until Sunday. 

David S. Wallens said:

https://www.youtube.com/embed/DLJecJfFUGI?rel=0

 

Got a chance to watch this.  Excellent video, and it makes me incredibly unhappy to have to do this.  I just don't wanna.

This is another pretty good video about repairing stress cracks and such. 

David S. Wallens said:

https://www.youtube.com/embed/DLJecJfFUGI?rel=0

 

So, in this around 4:50 Tim starts to mention backing repairs.  He mentions that you can use aluminum tape to back a repair while you work on one side.  He seems to say that the resin won't really stick to the tape.  Is that accurate, or did I interpret that incorrectly?

I'd like to attempt to install the bottom side of the repair, and then tape it in place while it sets so that it is smooth and doesn't fall down when I work on the top portion

Yes it is correct. Resin will not stick to aluminum foil/tape etc. However if the foil/tape has creases in it then the resin will soak into them and then the crease will become part of your projects resin.

In reply to Sparkydog :

Awesome.  And from how he applied it, sticky side to the resin.  

I guess this means I have everything I need to do this.  I feel like I did when I was about to cut up those LS heads.  Kinda excited, but also sick to my stomach.

Strong suggestion:  Don't use polyester resin.  If the original was poly, it will bond just fine, but if the original was epoxy, it won't bond quite as well.  Good epoxy is the "bond to anything" solution.

His repair looks like a pure epoxy with hardener that sat on the shelf for a while.  Epoxy hardeners use a carbon/oxygen bond that slowly "tans" over time.  It doesn't usually affect the strength of the finished product, just looks like poop.  Polyester resins (like a quart of bondo that you can buy at the parts store) is not really epoxy.  It is used in situations where the ultimate bond and strength isn't needed, but resistance to chemicals is important.  It also bonds to different substrates poorly.  For instance if you use polyester on PVC, once it cures you can pop it off with a fingernail.  It's great for body repair, fabrication of non-structural things, and good bonds.  But if you want to set it and forget it, epoxy is your bitch.

Epoxy is the bond-to-nearly-anything solution.  If you put epoxy on PVC, you could use a chisel on it and it would rip PVC off the substrate before it broke the bond.

Since you're splurging.... get West Systems epoxy.  Hands down the best of the best.  I keep a gallon of this at the theater.  Way overkill for you, but it comes in quarts as well.

Grinding/sanding is recommended.  Epoxies and polyesters are very much like many paint systems.  There is a window of time when the first coat is still curing and can accept a new coat and allow it to key into the coat below it.  Ever notice on a can of spray paint how it might say "recoat within 2 hours or wait 8 hours and lightly sand."

Since the substrate is quite obviously cured after 60 years, sanding/light grinding will be the ticket.

I picked up some FGCI epoxy stuff at T.A. Mahoney's

https://www.fgci.com/item/125460/Laminating-Epoxy-Resin-Quart-Bottle-65404184-/

https://www.fgci.com/item/125251/Non-Corrosive-Epoxy-Curing-Agent-4-1-Ratio-EA-684B-1-2-Pint/

I've taken it mostly down as far as it can go.  Chased the cracks, drilled the ends.  Still need to clean the bottom a bit more and get the top into more of a square shape, and I think I'll pull my little hull guards off on that side so I don't worry about them getting any crap on them.  Shouldn't have sealed them in quite yet I guess.

I've been working with fiberglass for a few years thanks to my other hobbies.  A lot of RC airplanes are wood and then covered in glass and resin, sanded and made beautiful.  If I can find photos of the first plane I ever did with dad in high school I will post it.  It was gorgeous but a bit too heavy to fly really well.  Fiberglass is super easy to work.  That is some of the heaviest (thickest and largest weave) fiberglass I have ever seen.  It was also attached improperly.  I'm glad you pulled it off.

You need to sand the area of the patch and around the patch out quite a ways from the holes (I'd say 6 - 9 inches).  You will need to do multiple layers of cloth for strength.  I would lay resin or epoxy, lay the first layer over the patch and while still tacky, I'd add a 2nd layer at a 45 degree angle to that layer.  I'd then soak both layers with resin or epoxy and squeegee them nicely and let dry.  Then I'd sand it again and do two more layers.  Since this is structural you want layers at different angles built up and aren't worried about weight much.  I would use a much lighter cloth.  I'm thinking 1-2 oz cloth might be good in this application (multiple layers).  I have some stupid light cloth for RC airplanes that would be of no help.  You can find all the cloth and epoxy and resins you will need for this at any big RC hobby shop like a Hobbytown. If you are in the DFW area, I'm happy to come over and help you do the first layer and after 48 hours or so you can do as many as you want.  It's easy to be honest. 

I'm thinking about using some epoxy and fiberglass cloth to fix some cracked mounting holes on my F body console right now.  I may do it tomorrow.  Once the cracks are repaired and can drill through the cloth or cut it with a very sharp hobby knife and viola new strengthened holes. 

You need to get a finned roller to ensure the mat is saturated and all of the air bubbles are out.

I would use chopped strand mat and use 3 or 4 layers.  Start with a piece that just covers the damage, then add successively larger pieces on top.  If you tear the mat instead of cut it, the repair will tend to 'disappear' into the original fiberglass. Saturate each layer and then roll with the finned roller. I have had better luck rolling from the center out.

Finally, be careful how much resin you end up with in the patch.  You need it to be wet, not pooled.  Roll out the excess.  All of these resins are exothermic and the more you get in one place, the hotter they can get when they go off.  Combine that with a hot Florida day, you could end up with a fire.

No, it is not a wife's tale. I once mixed a couple of pints of polyester resin and realized I was wasn't ready one hot day .  Sat the pail to the side and, after a few minutes, it started smoking -and not just little smoke, enough smoke for me to get a hose to cool it off.

I was thinking about excess resin and rollers.  Started to think about how best to wipe it up when I had it squeegeed off to the side.  Normal putty knife to get the gloop up and then use a chip brush or roller after to smooth any sharp edges back?

It depends on the substrate but I usually just use a plastic applicator, like you would use for bondo on a fender.

For a nice finish, you can cover it with saran wrap and then press a piece of plywood against it with a concrete block or something while it cures.

Ok folks.  I think I have everything.  As a friend of mine used to say, time to find out if I'm a hero or an shiny happy person.

Ok.  Well, that wasn't so bad.

I severely overestimated how fast or hard the epoxy can kick, though.  I was in full sun and 90 degrees out, though.  This is about 10 minutes after I mixed it. You can barely see it here, but that is vapor boiling off just below the 5% mark on the stick. The entire thing was smoking a second or two before that.  I panicked when I saw that and looked at the boat.  Little bit of vapor, but not near the amount that I got here.

Definitely going to not mix as much next time.  I overpoured the 4-part for sure.

It was like this at 25 minutes