Fiberglass

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Fiberglass

Postby Interim » Tue May 13, 2014 9:01 pm

I'm getting ready to repair a small injury on the bottom of my hull. The damage gets into the laminate but doesn't go thru. I have the west system repair kit.

The directions say to cut a series of smaller and smaller pieces of fabric, wet the area, lay on the first piece, saturate it with epoxy, lay on the next, etc. I'm assuming they mean to put them all on in one session, but want to make sure I'm not supposed to let the first layer cure before applying the second.

Am I on the right track?

Thanks.

--John
1979 DSII
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Re: Fiberglass

Postby UncleJohn » Wed May 14, 2014 1:54 am

John -

Yes, all one session. BUT, that can be pretty tricky, especially if you are working on a vertical or upside down surface. Standard West epoxy is pretty runny stuff - it drips and sags, and the layers of 'glass slip and slide. The repair kit package may have a thickener but, if it is designed to provide a thorough wet-out of the 'glass, it will still be pretty runny. Unless you can rotate the boat to put the repair in a level position like a table top, you will likely have problems with the epoxy (maybe 'glass and all) sagging out of the hole and/or dripping down the hull.

You may find it easier to do a tidy repair by doing it in one looong session. If you let the epoxy set completely, you need to clean and abrade the surface before applying subsequent layers. But, if you apply another layer while the previous layer is still 'green', the two layers will bond chemically. That's what you want. Your kit should provide specifications regarding the green cure window at various temperatures. I generally figure 8-12 hour intervals for standard West with the slow hardener - longer if it's cool, shorter if it's hot. Your stuff may have different set-up times - read the manual.

The second big advantage to working epoxy while it's still green is that it's much easier scrape, shave, or carve away the inevitable runs and sags. I have a razor-sharp Swedish sheath knife that is perfect for this. Once it sets completely it is MUCH more difficult to tidy things up for a fair and smooth surface.

Using the looong session approach, I'd start early Friday evening. Put some masking tape immediately down hill from the patch area, and maybe tape on a trough to catch any drips that want to run over the tape. Wet out the entire repair area, add the 1st layer of glass and wet it out. Don't use so much that it all runs out and the 'glass floats. You want the 'glass fully saturated, but tightly adhered to the substrate with no extra epoxy. Wipe up any drips or spills. Check it every 20-30 minutes for a couple hours to make sure the glass isn't slipping out or pulling away. Tuck it back in as needed. Saturday morning take off the tape, scrape/shave/carve any epoxy that isn't where it belongs. Re-apply tape and drip trough. Add 2nd layer of glass, etc. Repeat at appropriate intervals until the repair is flush with the hull. After the last layer is in place and the epoxy has cured to green, do your clean-up and rough fairing, but then be sure to come back a few hours later when the stuff is at a hard-green stage to do a bit more fairing so as to minimize the sandpaper work later on.

On the other hand, if it's not through the laminate or in a critical area, you could just trowel on a bit of Bondo and be done.

Show us some before and after photos.

- John
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Re: Fiberglass

Postby GreenLake » Wed May 14, 2014 3:46 am

"small" is relative.

Anything where the size of the glass patch is the size of your hand (more or less), or where a through hole goes down to 1" or less, is "small" in my book and usually not a problem, even on a vertical surface. I would not normally consider the "loooong" method for a "small" job like that.

I assume that you have followed the instruction and ground out some more laminate so that you have a nice shallow divot for your fiberglass work.

You can, and possibly should, use some plastic backing. For a "small" repair, the windows from toy boxes work well, they are nice and stiff, but still conform to the hull curve. You can press the backing onto the repair when you are done (using the "short" session method) and tape it down to hold everything in place while it cures. Should help in getting a (largely) level & smooth surface.

Second method is to build your laminate on the plastic and transfer the whole setup to the boat. That works better for repairs where you add a layer, not trying to precisely fill a hole.

Where a "loooong" job process might be useful is when the size exceeds "small", so that the glass is harder to keep in place, or where the inner hole (if there's one that goes all the way through) is getting large or complex. I had a case of the latter, where the hull no longer wanted to remain fair. In that instance, I first laminated a bit of a patch, let that set up away from the boat, then (in the green stage) glued it to the hole from the inside. That pushed the edges of the hole back into a fair shape. Now I was left with the "divot" case, but extended to form a wiggly trench. Easy enough to fill with the standard method, cure under a sheet of stiff plastic and be ready for sanding.

For that job, I used three phases.

For "small-ish" repairs, you do not need to use standard (runny) laminating epoxy (but if that's what you have, it's OK). Some of the stuff that's sold as glue is non-sagging, yet will still wet out glass cloth. This is true, in particular, for "Gel-Magic" from SystemThree. This one can be purchased in the caulk gun cartridge, meaning that you don't have to mess with mixing; and, as long as the glue in the mixing tip doesn't set, you can mix additional amounts by simply squeezing more glue through the tip.

I think I used that glue for both gluing the patch as well as wetting out some of the laminate in my repair, hence no issues with drips. Type "gored" into the search box on this forum, and you should get the link.
~ green ~ lake ~ ~
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Re: Fiberglass

Postby Interim » Wed May 14, 2014 8:42 am

Thanks, John and GreenLake.

Yes, the hull is upside down. I rented an extend-a-boom forklift (http://www.runyonrental.com/FORKLIFT-19 ... 0LB-C.item) pretty cheaply (not defined here to sustain self-deception). I hung the boat on two slings, and we just rotated it over by hand and lowered it on to a set of sawhorses.

"Small" in this case means about 2" x 4", right on the centerline of the hull about two feet aft of the stern. Laminate is damaged, but there is not a hole so I have backing to work from.

I gather from John's note that some curing should happen between application of each cloth, otherwise they layers would slide around. This allows the chemical bonding. I guess that means mixing new epoxy for each application.

Additional inspection last night revealed a possible crack in the centerboard trunk. Ugh. That will be a fun space to work in.

Lots of opportunities for learning :)

--john
1979 DSII
Interim
 
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Re: Fiberglass

Postby GreenLake » Wed May 14, 2014 12:26 pm

This definitely fits my definition of "small".

If you are working bottoms-up, so that it puts the repair on a near level surface, you do not need to worry about your repair "sliding". Yes, wet cloth can slide, but what you describe should be easy conditions, so you should be able to do it all at once, and then, as needed, secure it by taping some plastic over it (the reaction does not need access to air).

Mix up a single batch of epoxy and do it all in one go. (Don't mix up too much, and pour it out into a shallow dish once mixed, and it won't go off prematurely. One perhaps 2oz should be enough for a small patch). With a small repair, well prepared, you can finish it during the pot life of your batch.

You need to have all your glass bits pre-cut and everything ready.

Epoxy can be cleaned with alcohol until it cures. White vinegar works as well and the acid neutralizes the hardener (the more chemically aggressive of the components). The idea is to clean up any spills (and any non-disposable tools) right away (but keep cleaning agents off the repair itself until it's cured, some will inhibit the reaction).

Gloves!

and good luck!
~ green ~ lake ~ ~
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Re: Fiberglass

Postby Interim » Wed May 14, 2014 3:52 pm

Thanks. Definitely gloves. Googles too, given my history.

Sounds like you have some chemistry experience.

I appreciate the help.

--john
1979 DSII
Interim
 
Posts: 141
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Re: Fiberglass

Postby GreenLake » Wed May 14, 2014 11:35 pm

Not an expert in epoxy chemistry. But the information about the white vinegar is something I have from my favorite manufacturer. Either from their website or via the occasional e-mail query I sent them. Anyway, it's worked for me. I always keep a gallon bottle handy... but also plan on mostly disposable tools; for most things it's not economical to attempt to clean them.

And, by the way, "googles" --> "goggles" ?! :)

Good luck, hope it turns out well.
~ green ~ lake ~ ~
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Re: Fiberglass

Postby K.C. Walker » Thu May 15, 2014 4:19 pm

+1 for using the all-in-one go method. If you use plastic sheeting, I use .5 mm mylar, or Dacron fabric as a release cloth you can squeegee your patch pretty darn close to the final dimension. I'm guessing that the repair kit includes the medium hardener so you don't have to rush too much. Still, it's a good idea to do a dry run to make sure everything fits and that you don't need to spend any extra time. Make sure you stir the mix thoroughly, like for a full minute. This stuff gets really nice and hard and difficult to sand so don't get it proud of the surface, if you can help it. Use the squeegee as a straight edge, or use a straight edge to check (check it in your dry run, though it will be a bit thicker with the epoxy). If there is some of the patch that is proud of the hull surface, and you are into sharp tools, when it is leather hard (the first stage of hardening) it's fairly easy to cut and sculpt, I would use a sharp chisel myself. Though, be careful not to pull it out of your repair because it is not up to full strength yet. If you plan on making it nice and smooth, leave it a little low and then use lightweight filler as the next step to make it fair. Lightweight filler is MUCH easier to sand.

You should be fine. Doing your first epoxy work on the bottom is a good thing. You'll want it smooth for good performance but it doesn't have to be pretty.
KC Walker, DS 1 #7002
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Re: Fiberglass

Postby Interim » Tue May 20, 2014 4:20 pm

I did it, all-in-one go. My resin is a bit outside the profile I want, but I think the dremel will help there. The fiberglass went easily, but I do now understand why West suggests cutting it 3/4 inches smaller than the repair area. The fabric seems to spread out when saturated. I put filler on top, which sanded nicely, and a thin coat of resin on top of that. It is not perfect, but the hole is sealed and the shape won't create additional drag. The experience will be useful if I ever do a visible repair.

Two tests remain: 1) will spray paint endure through the summer, and 2) will the roller on my trailer crush the filler.

Next step is to lay the boat at a 45 degree angle so I can get inside the keel trunk, and to see whether I can lay in some fabric to fix what feels like a 5" break in the fiberglass.

Further updates to follow.

--john
1979 DSII
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Re: Fiberglass

Postby GreenLake » Wed May 21, 2014 1:41 am

Sounds like you had a good experience. What did you use for filler?
~ green ~ lake ~ ~
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Re: Fiberglass

Postby Interim » Wed May 21, 2014 8:21 am

The west system includes a powder that you blend into the epoxy to create the filler. They don't give an amount. Rather, they say add the powder until it reaches a non-sagging consistency.

The color I sprayed on last night didn't quite match the rest of the hull, so I'll try to keep the keel underwater from now on. :D

On another note, I used the 3M 5200 adhesive/sealant to fill some gaps in my hull-deck joint. I thought It is supposed to reach a sandable hardness, but it is still pretty soft after more than a week. Right now I have some bulges that I would like to smooth out, but this is more an aesthetic issue. As long as the hull stays attached to the deck, I suppose I'm all right.

--john
1979 DSII
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Re: Fiberglass

Postby GreenLake » Wed May 21, 2014 12:02 pm

From the specs:

3MTM Marine Adhesive/Sealant 5200 is a one-part polyurethane that chemically reacts with moisture to
deliver strong, flexible bonds. It has excellent adhesion to wood, gelcoat and fiberglass. It forms a
watertight, weather-resistant seal on joints and boat hardware, above and below the waterline. In
addition, its flexibility allows for dissipation of stress caused by shock, vibration, swelling or shrinking.


I don't think you should expect this to harden to a sandable state. Supposedly, it is strong enough that anything you glue is permanently bonded, to the point that I've read that the best (only?) way to undo a bond is to saw through it with a thin wire....

If your bulges are big, you might succeed in slicing them off with a razor blade.

On fillers: I'm partial to premixed stuff, like QuickFair from SystemThree. For places where the filler has to have strength, I've been using 3M's High Strength Marine Filler. It's not epoxy based, but it has some glass fibers mixed in and is strong enough to, for example, fix a gouge in the leading edge of a CB, an application where it extends out a bit and is unsupported. If your trailer roller ever knocks out the filler you used, that could be your backup plan. (I wouldn't expect it to, though, unless you used more than a very thin layer).
~ green ~ lake ~ ~
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Re: Fiberglass

Postby Interim » Mon Jun 02, 2014 11:55 am

Good news and bad news:

We went for our first sail of the year on Saturday, and had to hold off as thunderstorm cells passed nearby. When they were gone, the wind went dead calm and there was no point in trying to sail. However, we did have a nice shakedown for setting up and launching.

The good news is that during the 30 minutes the boat sat in the water, we took in no water whatsoever. This was probably only a good test of our forward repair. The centerboard trunk and the hull-deck joint probably need to be underway to get tested.

Regards,

--john
1979 DSII
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Re: Fiberglass

Postby GreenLake » Mon Jun 02, 2014 5:11 pm

It's hard to "test" a foredeck repair, other than by sailing it very hard. If it survives fine, but if not, that test would not be very "non-destructive"...
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