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  #11  
Old 11-02-2007
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I've used the Casey method with great success. It makes sense to me to do it this way, because the edges of the hole must be ground out. The result is a taper leading from the good glass down into the hole. The deepest part of the hole is the smallest, so use the smallest piece of your repair patch there. As your repair gets thicker, it matches up to a larger diameter part of the taper and you use a larger diameter patch.

If I used too large of a piece of glass to patch the hole, it tends to pull up in the center if using mat, or pucker if using cloth. Then again maybe I'm just not familiar with the other technique.

John
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Old 11-02-2007
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Quote:
Originally Posted by US27inKS View Post
I've used the Casey method with great success. It makes sense to me to do it this way, because the edges of the hole must be ground out. The result is a taper leading from the good glass down into the hole. The deepest part of the hole is the smallest, so use the smallest piece of your repair patch there. As your repair gets thicker, it matches up to a larger diameter part of the taper and you use a larger diameter patch.

If I used too large of a piece of glass to patch the hole, it tends to pull up in the center if using mat, or pucker if using cloth. Then again maybe I'm just not familiar with the other technique.

John
With all due respect it is the oposite of Johns discription, it does seem ass about but you start with the largest piece of cloth to make the largest possible contact with the depresion you will have ground into the hole.
Because its back to front in relation to what you would think would be the right way is what makes it easier to remember.
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  #13  
Old 11-05-2007
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Thank you all for your comments
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Old 11-10-2007
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the first thing i see wrong is filling a circle. no matter what or how you fill it,, you will always see it, even through the best paint job. it needs to be odd shape,, take a grinder to it and put some lightning bolts into it on the outside of the O so its more like # or **} amything except a O
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Old 11-11-2007
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Quote:
Originally Posted by haffiman37 View Post
The most important is how the 'new' patch bonds to the old, that the caracteristics of the new patch (flexibility/hardness etc) is as close to the original as possible.
If Your boat is polyester/fiberglass, then use polyester fiberglass for repair and not epoxy/kevlar.
I agree with the first part of this post and as such, very much disagree with the second half. A repair patch is a mechanical bond, and epoxy is much stronger adhesive than polyester. The most important part is properly prepping the are to be repaired, and then use a good epoxy with your choice of glass/aramid/etc.

As to the hole repair, I have used both methods, and perfer the large patch first method. I have found that in the process of fairing, you tend to sand through much of the last piece of glass, and if that piece is the largest, you lose most of the advantages of having it there in the fisrt place. Just my $0.02.

Ryan
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Old 11-11-2007
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what haffiman is saying is, that rock hard epoxy doesnt flex the same as the poly,,,there lies ya problem and where ya cracks are going to be. so to keep that from happening you need to use what everything around the patch, is made from poly,,,,, and the mechanical bond is bout the same for poly as epoxy,,, its just that the epoxy is harder,,it doesnt mean it "sticks" any better
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Old 11-11-2007
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To add a little complication the West Systems Video shows wetting out all the layers of the patch and sticking them together on your work table, then slapping them in the hole in one dramatic moment.
I suppose if it is too thick you just peel off the last, smallest layer.
I am loathe to argue with the West people as they have been doing this a while. I wonder if the difference in style has to do with the difference between a production technique by someone with 30 years experience and a technique more in line with average skills.
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Old 11-11-2007
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I really hope you don't build boats for a living. The secondary bonding characteristics of epoxy is much stronger than that of polyester or vinylester resin. That is a major reason why epoxy is generally used for repairs.

Yes, epoxy-based GRP and Polyester/vinylester-based GRP will flex and expand at slightly different rates under the same stress and temperatures, but that generally isn't much of a problem unless you've made one side of a boat in epoxy-glass laminate and the other in polyester-glass laminate.

When you're talking about relatively small patches, like filling in a 4" instrument hole or 2" through-hull hole, the differences in flex and such are not really a major consideration IMHO—especially given epoxy's stronger secondary bonding characteristics and greater tensile strength.

Quote:
Originally Posted by the1much View Post
what haffiman is saying is, that rock hard epoxy doesnt flex the same as the poly,,,there lies ya problem and where ya cracks are going to be. so to keep that from happening you need to use what everything around the patch, is made from poly,,,,, and the mechanical bond is bout the same for poly as epoxy,,, its just that the epoxy is harder,,it doesnt mean it "sticks" any better
As for your earilier post about making the hole non-circular—you don't seem to realize that by expanding the scope of the hole more than necessary to grind out the non-circular shape you're actually damaging the existing laminate and weakening it, and effectively exacerbating any problems you'd have due to the strength and expansion differences between the patching epoxy and existing polyester resin.

BTW, the fibers in any laminate provide the greatest strength when they are fully continuous. This is why chopper gun fiberglass layup is so much weaker than using tri-axial roving—since the strands are much shorter in chopper gun fiberglass. By sanding an irregular outline around the hole, you're effectively weakening the laminate all around the hole...and since the outline is irregular, it is unlikely that you can repair that area with contiguous strands of glass in the patch. This is also one major reaons I generally like to put the largest piece of glass down first, rather than the smallest—when you're sanding the surface fair, you tend to go through the outermost layers quite a bit...and that would leave you with the shorter layers intact, but break up much of the longest fibers in the repair.

You can't have it both ways. Either you should minimize the use of epoxy, due to the difference in bonding and expansion characteristics, or you should maximize the contact area because having an irregularly shaped patch will increase the strength of the repair...

Again, I really hope you don't build boats for a living or that people don't use your boats for anything serious, given what you're saying on this forum.
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Old 11-11-2007
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um yes i do er,, did build boats for a living, and i painted too. and the people that taught me all this are the very top boat builders in the world. and when ya talking bout a small patch yes it dont matter,, but didnt the patch this thread is about end up like WAY bigger then a few inches?, and if the hole is a circle its a stronger patch then if the hole is a jagged edge? hmm what science is that?
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  #20  
Old 11-11-2007
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and P.S. the only boat that i've built to come back for major repairs other then cosmetics was an apogee 55 that when it was built the dude didnt know what he wanted for port lights so we had blanks in them,, when he decided they put them in using epoxy ,, 8 years later every port light cracked,,guess where and why?, and before ya wanna insult,,, i didnt have nothing to do with the epoxy
what production line did you learn from? i bet i've repaired one of em
and dont over exaggerate ,, putting a small 1/4 nick in that circle doesnt compromise anything
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Last edited by the1much; 11-11-2007 at 12:02 PM.
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