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Old 05-07-2016, 03:15 PM   #1
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Exclamation What is the ultimate gel coat crack V scrape tool ?

In other words, for enlarging and cleaning out a minor gelcoat crack prior to Marinetex application. A V can opener end works of course but seems like there would be something of harder alloy and sharper....or maybe even electric ?

Also....never tried it, but wondering if there exists a masking tape one could apply over a minor crack and then V scrape the crack out by feel, so that only the crack is exposed which would make Marinetex application less messy.

To be sure you weren't scratching out anywhere other than the crack perhaps go over the tape first with sharp knife to create a target path ?

Seems like regular masking tape might fray too much. But perhaps not, if one had a super sharp V scraper ?

Thoughts ?


(And please try to resist comments about first finding the reason for the cracks as I am well aware of that aspect and in this thread rather discuss cosmetic crack repair techniques)
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Old 05-07-2016, 03:34 PM   #2
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I have a tool similar to this and it would be my first choice.
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Old 05-07-2016, 04:03 PM   #3
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I prefer a squ are notch versus a vee, so I use a dremel tool unless the crack is very shallow and only a hairline.

Could still just use the dremel but there are lots of vee shaped scrapers out there.
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Old 05-07-2016, 04:27 PM   #4
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Quote:
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I have a tool similar to this and it would be my first choice.
Interesting. In the photo it shows the blade in flat scape position. Can the blade be rotated to locate it in V position ? OTOH, I notice another blade possibility for it as well...

http://www.amazon.com/Bahco-625-DROP...7F7FX8E7T78WTR


The the carbide aspects, generally carbide stays sharp way longer but the sharpest carbide is not as sharp as the sharpest hardened steel (thinking of the "not fraying the masking tape" ideal again... )
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Old 05-07-2016, 04:35 PM   #5
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Greetings,
Mr. D. I second the use of a Dremel tool for the control aspect. If one uses a scraper, one slip and you now have a crack AND a scratch.


Pick your profile.
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Old 05-07-2016, 05:33 PM   #6
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Sharpened "church key".
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Old 05-07-2016, 06:46 PM   #7
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Sharpened "church key".
Everything on a boat should be able to do double duty.
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Old 05-08-2016, 08:48 AM   #8
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Last weekend I had to repair a cracked tractor canopy, a Dremel did a nice job of prepping the cracks.
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Old 05-08-2016, 09:15 AM   #9
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Greetings,
Mr. D. I second the use of a Dremel tool for the control aspect. If one uses a scraper, one slip and you now have a crack AND a scratch. Pick your profile.
Quote:
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Last weekend I had to repair a cracked tractor canopy, a Dremel did a nice job of prepping the cracks.
What they said. When we repainted/new gel-coat, we couldn't have done it with out the Dremel. Fast and easy to control plus cracks aren't always in a straight line.
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Old 05-09-2016, 10:25 AM   #10
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What they said. When we repainted/new gel-coat, we couldn't have done it with out the Dremel. Fast and easy to control plus cracks aren't always in a straight line.
It would be interesting to see exactly which Dremel cutting tool you used, what the crack looked like before, then after Dremeling (before filling) Are you are doing this freehand, not using the little router base option ?

Seems like a Dremel could get out of control more so than a manual V scraper but I haven't actually tried it. Most of my cracks are fairly gentle curves, so no problem with the V of a can opener....but do have one that is pretty irregular where the Dremel might be best indeed.
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Old 05-09-2016, 10:29 AM   #11
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Sharpened "church key".
That's what I have used.
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Old 05-09-2016, 12:53 PM   #12
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It would be interesting to see exactly which Dremel cutting tool you used, what the crack looked like before, then after Dremeling (before filling) Are you are doing this freehand, not using the little router base option ?

Seems like a Dremel could get out of control more so than a manual V scraper but I haven't actually tried it. Most of my cracks are fairly gentle curves, so no problem with the V of a can opener....but do have one that is pretty irregular where the Dremel might be best indeed.
Either easily gets out of control if you let it. Two handed free hand is my method and start the griding with almost a gentle dragging motion to deepen the crack...that allows a better inspection of the crack and better control for the second pass.

The tool end depends on the crack...larger cracks get larger heads in my work.
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Old 05-12-2016, 08:40 AM   #13
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Greetings,
Mr. D. I second the use of a Dremel tool for the control aspect. If one uses a scraper, one slip and you now have a crack AND a scratch.


Pick your profile.
Too aggressive a cut, that tool will grab the work and pull into it, easily veering off in odd directions, at least it does on aluminum gutters.

Better idea is diamond point grinders for the dremel, many many more sharp points so grinding will stay true.

I just helped with house gutters. I used the dremel with one of those cylinder cutters you show. Several times per hole, the cutter would grab the aluminum and dig in away from the direction you wanted to cut. It is like your driving down a straight road, and the steering wheel suddenly pulls off to the side.
Maybe grinding aluminum sheet is different from grinding fiberglass.

At home I have a set of diamond studded cutters, they do not cause the dremel to veer off track from the line of cut, because it is more of a grinder than a cutter.

Also good idea to wear ear protection, the dremel high pitch hurts my ears.
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Old 05-12-2016, 08:51 AM   #14
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Greetings,
Mr. 717. I hear ya on the grabbing. One needs a firm and steady hand while taking shallow cuts. Somewhat agree on the diamond studded cutters as they're sort of omni-directional but my concern would be premature clogging with FRP.

My picture was simply a suggestion. Dremel has a plethora of cutter designs so one can pick one's own "poison". I have used the Dremel flexible shaft option occasionally and the smaller diameter, pencil-like hand piece allows even more precise control.

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Old 05-12-2016, 08:59 AM   #15
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They work just fine...use them in a shallow dragging motion.....they get away from you like any tool if you try a too aggressive cut all at once or hand tools that require force and gets away too.
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Old 05-12-2016, 10:13 AM   #16
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They work just fine...use them in a shallow dragging motion.....they get away from you like any tool if you try a too aggressive cut all at once or hand tools that require force and gets away too.
Exactly

I've spent my career telling apprentices to let the tool make the cut. Treat it like a lady with a slow, steady yet firm reassuring grasp. A limp wristed loose grip with a half hearted attention span has never reassured anyone.
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Old 05-12-2016, 10:58 AM   #17
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Once a cutter digs in and starts walking on the working surface, it has quite a bit of force on it, a surprising amount. I am no weakling, 200 lbs, 6'4", can lift a 400 lb engine block by hands (stuck into the cylinders, surprised myself!), yet even paying close attention, using 2 hands, the bit when it grabs can wander immediately quickly and then you may be sorry. Diamond grinder no such trouble.

The 5 oval holes I cut were for the downspouts.
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Old 05-12-2016, 11:31 AM   #18
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With all due respect its a piss poor mechanic that blames the tool. Practice makes perfect. Been using die grinders for precision work for well over 30 years. Sorry but those holes where not round because of the operator not the tool.
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Old 05-12-2016, 11:38 AM   #19
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I thought we were talking gel coat scratches....am I wrong?


We are only talking a low pressure drag along the crack...low pressure, no digging...no grabbing.....and now just deep enough and square enough to hold the right amount of gel coat.


If you are going down into laminate...that's another whole repair issue and tools required...certainly not a beer can opener which does work fine most of the time...just suggesting a dremel as it does what I need it to do.
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Old 05-12-2016, 01:38 PM   #20
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With all due respect its a piss poor mechanic that blames the tool. Practice makes perfect. Been using die grinders for precision work for well over 30 years. Sorry but those holes where not round because of the operator not the tool.
If you had ever cut gutter downspout holes, you would know they are definitely oval holes not round holes!
Every single oval hole I cut was almost perfect.
You never cut on the line, you start your cuts further back, then you cut up to the edge.
I had absolutely no defects, these hole were very good that I cut.
All I said was it was difficult to control the cutting, but see now, who cares about the piece being removed from the hole being cut.

What we had were preformed downspouts with a short section of gutter. like a foot.
I popped out the inserts and traced the pattern out onto the main aluminum gutter. Once the pattern is visible, then you start cutting out the oval hole.
This site is extremely tedious at the moment. maybe I can just give up on this thread.
Over and out gone, never to hear again on this thread from me, bye-bye, caput, sayonara.

Yup I have ported cast iron heads too, successfully. Fact is I have done very detailed work, most would not do themselves.
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