Taking down to fiberglass

[reed1v]

Sandblasting is the best way to remove layers from a fiberglass hull.If your going to repair an extensive section, might as well do it right.

[2hullvenus]

Originally Posted by reed1v

Sandblasting is the best way to remove layers from a fiberglass hull.If your going to repair an extensive section, might as well do it right.

I think he said he's fixing cracks and adding some glass to the original layup to prevent them from forming again.

A uniform take down isn't how you fix cracks.

[2hullvenus]

Originally Posted by Scot McPherson

Specifically I need to cut out the chain plate backing and replace it with new lumber. The chain plate blocks are fiber glasses in and in a tight space so I'll need an angle grinder to get in there to cut.


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Whole different story.

Cracks around the chainplate are not the same as cracks in a fiberglass hull, as my whole post was about.

Good to see the actual problem now. May have been helpful earlier.

Definitely use an angle grinder to tear all of that out.

If this glasswork developed cracks, the boat was definitely not designed correctly from the start.

Be absolutely sure your new glasswork is sufficient.

Pay particular attention to fiber orientation as pertains to the loads the chain plate will be putting on your bonding work and the hull.

Not the worst idea to get a couple hours of a naval architect's time to be sure you get it right.

[Scot McPherson]

Originally Posted by 2hullvenus

Whole different story.



Cracks around the chainplate are not the same as cracks in a fiberglass hull, as my whole post was about.



Good to see the actual problem now. May have been helpful earlier.



Definitely use an angle grinder to tear all of that out.



If this glasswork developed cracks, the boat was definitely not designed correctly from the start.



Be absolutely sure your new glasswork is sufficient.



Pay particular attention to fiber orientation as pertains to the loads the chain plate will be putting on your bonding work and the hull.



Not the worst idea to get a couple hours of a naval architect's time to be sure you get it right.

Not what I said. Totally different job totally different section of the hull, just saying I could use an angle grinder for both jobs and not need to buy a tool I won't use again any time soon.

For the chain plates, I need to replace rotten wood backing, and that all. The wood is encased in fiber glass so I need to cut it out, smooth it out and glass new blocks into place...but that's a whole different topic and I don't really have any questions about what to do here.

My question here was strictly about tool choice for stripping down large sections of gelcoat down to the glass.

And thanks to everyone who has taken time to think about it and respond.


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[Cheechako]

I'm confused about what you are doing. Are you stripping and adding glass to the whole hull? Are you removing/repairing just the chainplates? If you are glassing the whole hull then a good hard sandblasting might be a great way to go, it will be more uniform and have good grip for adhesion.
Peeling would be great too, but more expensive and of course you are losing some of the glass you want to gain.

[2hullvenus]

Originally Posted by Scot McPherson

Not what I said. Totally different job totally different section of the hull, just saying I could use an angle grinder for both jobs and not need to buy a tool I won't use again any time soon.

For the chain plates, I need to replace rotten wood backing, and that all. The wood is encased in fiber glass so I need to cut it out, smooth it out and glass new blocks into place...but that's a whole different topic and I don't really have any questions about what to do here.

My question here was strictly about tool choice for stripping down large sections of gelcoat down to the glass.

And thanks to everyone who has taken time to think about it and respond.


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Your posts were not at all clear.

Peeling or sandblasting, then.

[GrahamHO]

Originally Posted by Scot McPherson

If you wanted to take your finish all the way down to the fiberglass to do some patching and add another layer of cloth to your hull, which tool would you pick to remove material the fastest?

A belt sander
An angle grinder

Or something else?

I have a hull that was cracked on the rocks, and I want to take a large swath of material down clear to the glass so I can reinforce and patch where it's cracked, then lay another layer or two of 9oz glass over the entire section.

If you had t pick one, which would you prefer and why?

Thanks,
Scot


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I'd use neither as they are to violent. I favour hand tools for that job like some different sized sharp chisels and gentle taps with a hammer or simply using them by hand, followed by hand sanding. You need of course to taper any repair. A small orbital sander is useful for later finishing. I use one that takes 125 mm perforated discs held on by Velcro like material. They have a random rotary action and a dust bag.
Patch with epoxy (West) and add layers of glass while the previous smaller (tapered) layer is still tacky. Use those small metal rollers to press the glass into the resin. Then apply peel ply to the top layer to get a fairly smooth finish. You peel it off later. If and when your metal rollers ( small diameter made from threaded rod) become blocked with resin you can burn it off in a flame or fire.
Cleaning them in meths or thinners works for a while.
If your hole is large, you may need a piece of (Formica) bench top material taped inside and coated in polish to make it removable. .

[reed1v]

Originally Posted by 2hullvenus

I think he said he's fixing cracks and adding some glass to the original layup to prevent them from forming again.

A uniform take down isn't how you fix cracks.

In the hands of a competent sandblaster, one can remove very small areas, provide fine bevels for laying up patches, and, if so desired, even carve holes into the hull. Advantage is that one can control exactly what is removed whereas the other methods leave much to be desired in terms of control and refinement.

[chris95040]

Originally Posted by skipgundlach

Agreed on Epoxy repair; secondary bond of epoxy to poly is the same as prime bond poly.

i wish!!!

[Cadence]

Originally Posted by chris95040

i wish!!!

You have that right. Poly is only good laid up wet or uncured.

[UNCIVILIZED]

If your hull's cracked, get some Good NDT done on it, to first determine the size & depth of the needed repairs. Ditto on what may be damaged in terms of bulkhead, chainplate, & other structural, internal attachments.
As on this kind of a fix, it's unwise to go at it half cocked. Including, knowing/deciding how much material needs removing, & replacing, where.

Once the Full extent of the damage is determined, then you can sit down with a professional who has the requisite knowledge, in the proper areas of expertise, & formulate a proper plan to fix things. Including some suggestions on which tools to use for what.
And when you're figuring the cost of the repairs, the proper tools are simply part of this cost. Cheaping out on such rarely works out well, in addition to making the job more difficult to do well.

As they say, "There's never enough time to do the job correctly, but there's always time to do it again".

Glass removal 101 = 9" Grinder, with a dust muzzle. There are other options. But without knowing exactly what it is you're trying to accomplish, I'm hesitant to make any further recommendations.

[Scot McPherson]

So a neighbor had a 6 inch Grinder which he pretty much said I could have and return anytime or even not all. I just had my first opportunity to sit down and grind some of the cracks down with a smooth taper to 6 inches on either side. Using a 40 grit pad, it took the material down very quickly and it wasn't very long until I was able to learn how to control the "cutting" of the material.

I ground clear down to and through the roving until I could just about push my finger through the hull if I tried hard enough.

I'll begin laying back up next weekend if it's warm enough. It's supposed to be in the high 40s. Not really a question but more rhetorical thinking here, but wondering if I should risk laying up if it's below 50 degrees. West system recommends not below 40 F.


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[deltaten]

I've found 60 degrees almost to cold for epoxy resin lamination. Can't even imagine trying it @ 40 ! Last little project , I had to supply mild heat @ 68 degrees to get the resin to set.

[Scot McPherson]

Well when the boat was stranded on the beach where it go cracked, i was forced to do some patchwork prior to having the boated pulled off and re-floated. It was about 50 degrees and getting colder and it dipped into the low 40s overnight. Tye next day it warmed up to 50-ish again and the patching laminations hardened up pretty well. In fact that morning I had to put in yet another patch elsewhere, where I hadn't noticed another developed hole in the hull, and it hardened up before that afternoon when the boat was dragged off the sand. Granted the boat was only in the water for 3 hours between refloating and getting hauled out, but even after hauling out, the patch was rock hard.

Those are what I ground out this weekend.


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[GrahamHO]

Originally Posted by Scot McPherson

So a neighbor had a 6 inch Grinder which he pretty much said I could have and return anytime or even not all. I just had my first opportunity to sit down and grind some of the cracks down with a smooth taper to 6 inches on either side. Using a 40 grit pad, it took the material down very quickly and it wasn't very long until I was able to learn how to control the "cutting" of the material.

I ground clear down to and through the roving until I could just about push my finger through the hull if I tried hard enough.

I'll begin laying back up next weekend if it's warm enough. It's supposed to be in the high 40s. Not really a question but more rhetorical thinking here, but wondering if I should risk laying up if it's below 50 degrees. West system recommends not below 40 F.


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50*f is around 10*c and a little on the cool side. It will cure OK but take a lot longer. When you are building up several laminations, you don't want the previous layer to be cured before you apply the next one so 50*f won't matter.
When one layer is still tacky you should apply the next. Then when you want it all to "go off" you can apply some gentle heat with a hair dryer moving it around for some time.
I've just finished laminating some glass onto end grain balsa to make new washboards. After I finished rolling the first layer until it was smooth, I immediately applied the second layer while the first was still wet. Then after I rolled that one I applied peel ply and rolled that. The temp was around 18*c 65* f and I didn't need heat.