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PostPosted: Fri Nov 26, 2010 8:33 pm 
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Hello all,

It sucks my first post has to be in the repairs section but such is life eh?

I've been reading about bottom fixes and I've been trying to find information on repairs for holes but I havent really seen anything for this kind of damage.

I recently purchased my first hobie! upon taking her out but the hull quickly filled up with water. When I pulled her out I looked and the front end of the starboard hull had putty that was falling off. There was apparently some huge hole that was repaired with some kind of putty (maybe bondo?) that did not stick to the hull at all. i removed most of the putty that was falling apart and was left with a large piece missing from the hull.

Image
IMG_0192 by kagor101


Image
IMG_0196 by kagor101, on Flickr

How do I go about repairing this? Typical cloth layers with epoxy resin or polyester? I was reading to use epoxy for anything truly structural yeah? Also how do I go about keeping the profile of the hull?

Any help is greatly appreciated.


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PostPosted: Mon Nov 29, 2010 12:31 pm 
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Location: Lititz, PA/Somers Point, NJ
ouch!!

Body filler has no place in a hole that big on the keel. The ideal way to fix that would be to start on the inside where you can lay up larger peices of mat and give you a good base to build out from. Any chance you have a port in the hull that you can access this damage?

I'm affraid if you just work from the outside you won't have enough strength and it will break out again.

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PostPosted: Mon Nov 29, 2010 6:11 pm 
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Location: Detroit, MI
This can be done from the outside. No need for a port. It's not a structural part of the boat, but it needs to be tough to withstand modest impacts.

You'll need to remove all the damaged glass and feather back the edges. It will look much, much worse before it gets better. Disc sander on an angle grinder will make very quick work of this.

You'll need to fabricate a backing sheet of polyester resin / glass to go in the hole and be glued in place with epoxy. Spread out a plastic drop cloth on a firm, flat surface and wet out two layers of fiberglass matting in a rough circular pattern, big enough to overlap the hole by 3" on all sides. After the resin starts to go off, but before it's really hard, peel it up and form it into the rough shape of the hole by inserting it and pulling it back against the sides with fishing line stitched through the apex of the curve. (See "Blind Hole Repair", Hobie HOTLINE magazine here: http://2010.archive.hobiecat.com/hobieclass/eHCA_Hotline05-06_2008.pdf. Let the resin cure completely, remove and glue back in with thickened epoxy resin (peanut butter consistency and don't be shy about using lots to glue it in).

Once that's in place (plugging up the hole and forming a rough outline of the shape to be restored), start laying glass and polyester resin until the shape is built up. Sand to shape, fair with thickened (Cab-o-sil) poly resin and sand to final shape. Spray with gel, sand and polish.

This can be done in 3 days, most of which is waiting for resin to go off. The only real hard part is matching the color. Good luck with that.


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PostPosted: Tue Nov 30, 2010 6:34 am 
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Yep do what MBounds says. I wasn't recommending putting a port in but if there was one already there it would be worth using.


Mbounds... I'm a bit confused I'm hoping you can help me out. My understanding is that epoxy likes poly but not the other way around. I understand why you would use the epoxy to glue it into place but won't there be an issue adhering the polyester resin to the epoxy after the epoxy cures?

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PostPosted: Tue Nov 30, 2010 8:08 am 
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reelknotty wrote:
Mbounds... I'm a bit confused I'm hoping you can help me out. My understanding is that epoxy likes poly but not the other way around. I understand why you would use the epoxy to glue it into place but won't there be an issue adhering the polyester resin to the epoxy after the epoxy cures?

The reason I would use epoxy to glue in the backing plate is simple - it's much stronger than polyester and much more tolerant of the poor fit that you're going to get when you glue that piece in. Let's face it - you won't get a perfect fit on the backing plate to the inside of the hull. Epoxy will compensate for that.

If you're careful, there shouldn't be much epoxy exposed after you glue the backing plate in - maybe just the stuff that squeezes out. If you scrape that off before it cures, then give it a quick wipe with acetone, that will minimize it even more.

The problem with epoxy is the amine blush that forms on the surface when it cures. It's waxy and not much sticks to it. It must be removed (toluene, soap+water or sanding) before poly will stick to it.

Epoxy forms very strong chemical bonds with almost anything - a physical bond (surface roughness) is not necessary. Polyester resin likes to chemically bond with itself and requires more surface roughness to bond with other materials.


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PostPosted: Tue Nov 30, 2010 8:13 am 
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perfect thanks. I was picturing the oozing epoxy and just trying to put it all together in my head. Thanks for the clearification!

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PostPosted: Sun Jan 02, 2011 4:01 pm 
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Thanks for all the help. I ended up doing a double post on this because I didnt realize the first one actually survived the mod. I ended up using polyester resin because that is what was available at my local HD. But you were very right. I had to roughen up the surface quite a bit as well as use a significant amount of resin to and folded backing pieces to get it to make a tight fit. I used the fishing line technique and it worked amazingly.

If you want to see the results check out the other post I did here.

http://www.hobiecat.com/forums/viewtopic.php?f=13&t=33302


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