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 Post subject: Small gouge in hull
PostPosted: Thu Mar 07, 2013 11:52 am 
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After my first deep clean of my new-to-me 1985 hobie 16, I've come across this little bugger. As you can see, from the left it starts as a scratch then gets to a gouge for the last inch to inch and a half. Aesthetically it doesnt bother me, but it almost seems like if I put a ton of pressure on the gouged part, I could put a one inch hole in the fiberglass. Aside from taking this to a fiberglass shop(which I'm going to guess would cost me more than I'd like to pay), whats the best way to fix this? It doesn't have to look factory original, but of it's a white color and not super noticeable I'd be happy. Thanks for any advice! Image


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 Post subject: Re: Small gouge in hull
PostPosted: Thu Mar 07, 2013 2:44 pm 
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Location: Jersey Shore
Looks like this damage likely cracked the outer fiberglass skin at the very least. Overall, it looks to be a pretty small area of damage based on the photo.

First thing I would do would be to do the coin tap test around the damage. Listen for where the sound goes from a crisp high pitched tone to a dull flat tone. The dull tone indicates where the hull structure is damaged. Mark the area with a pencil. Then you'll have to use a dremel or a die grinder to grind away the gelcoat in the damaged area so you can inspect how extensive the damage is.

Most likely it will just require a few layers of 6 to 8 oz fiberglass to patch the damage, then application of putty, fairing, and finally gelcoat. It's not as difficult as it may sound, just takes a little time and some thought and you should be able to pull off a decent repair without going to a professional. I would estimate you're looking at $50 to $80 in materials (with plenty of material leftover for future repairs).

I'd recommend you do a little searching on this forum as there have been a few prior discussions of similar repairs. There are also some good Hotline articles on repairs, so you should search those archives under the "This Old Hobie" articles.

Last, don't be tempted to just smear some Marine Tex or other putty in there as a repair. If the fiberglass skin is cracked, then you need a fiberglass patch or it will likely crack again allowing water to penetrate the hull and ultimately lead to delamination (again, start with the coin tap test). Also, for a repair like this, you want to stick to polyester/vinylester resins - no epoxy.

sm


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 Post subject: Re: Small gouge in hull
PostPosted: Thu Mar 07, 2013 4:17 pm 
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Thanks for the reply, one of the main reasons I asked the question was to see whether or not I could just put some sort of Marine Tex or putty on there, so I'm glad you made it a point in you our response to advise against that. I'll have to buy the materials but I'm sure it's worth it.


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 Post subject: Re: Small gouge in hull
PostPosted: Mon Mar 11, 2013 5:10 pm 
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So I've used a small grinder to get out the loose parts. I hope I didn't go to deep, it seems like I'm in the inner foam core as it's a spongy material.
Image

I bought the polyester fiberglass repair kit shown below, is that the one to use? Can I lay fiberglass directly in and over this hole or should I put some sort of filler in first before the fiberglass? Is this a situation where it would be better to make a true hole in the boat(cut through the inner fiberglass layer) and work from there?

Image

Thanks for the help.


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 Post subject: Re: Small gouge in hull
PostPosted: Mon Mar 11, 2013 5:22 pm 
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Location: Raleigh, North Carolina
Not sure about the Kit. You need...

Polyester Resin
A few strips of fiberglass cloth
Some white polyester gel coat
(optional but worth it - prevail spray can)

if that's all in the kit you are good to go.

Then do this...

viewtopic.php?f=20&t=43039

Just make sure the foam is ok. If it's waterlogged or delaminating (foam seperated from the glass skin) then you might want to inject it with Gitrot before you make the repair.

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94' H16 - 100403
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 Post subject: Re: Small gouge in hull
PostPosted: Mon Mar 11, 2013 5:41 pm 
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Location: Jersey Shore
It looks like you need a lot more taper to that repair. You really want to remove material at a gradual taper so that you can laminate on a patch (or patches over the damage and the patch is able to bond to the existing fiberglass skin. Right now, you have no way of laminating to the existing glass. So you need to remove the gelcoat around the hole you created (and you will probably end up removing part of the hull stripe/sticker). For reference, in the aerospace industry, they require a taper of 30:1 for composite skin repairs. So if you grind down 1/8", you would need to taper the material back roughly 4" from the edge of the damage. Since you're not repairing the wing of a 787, you can cheat that to some degree, but the idea is that you want to gradually remove material at a taper so you have a place to lay in your repair patches and they have existing fiberglass to bond to.

Also, you mentioned that your foam core is "spongy". That is bad because it means water likely penetrated the core. You're going to have to remove material until you get to undamaged foam. If you only have to remove a little more foam to get to "good" foam, then I would do that and then probably just use filler to replace the foam you removed (formula 27 filler if it's just a small area, if it's larger then probably resin thickend with chopped glass). If it's a large area, you would want to replace the foam with new high-density foam core, although I doubt that's necessary in this case. Once you've filled in the hole you created and tapered back the repair area some more, you can laminate your fiberglass repair plys (two or three layers of 6 to 8 oz cloth). Then sand it lightly, overcoat with formula 27 putty, sand smooth, then gelocoat, wetsand, and polish.

Also, I would not go through the inner skin if you can help it. If you do, you will have to laminate a patch on the inside before you can go through with the rest of the repair.

sm


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 Post subject: Re: Small gouge in hull
PostPosted: Mon Mar 11, 2013 5:45 pm 
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Thanks for both replies, they have really clarified things for me, I'll let you know how it turns out!


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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 1:20 pm 
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A few more questions. Do I need fiberglass mat for this repair or are a few layers of fiberglass cloth enough?

Secondly, is there an alternative to formula 27? None of my local West Marines carry it, although they said they could order it. I'd like to get this repair done by the end of the weekend though, so I'd rather not have to wait several days for an order if I can help it.

Lastly, I understand from previous responses that "spongy foam" is bad. Well the foam directly below the gouge didn't seem to be in the best shape so I sanded it out, but I'm just not sure if the surrounding foam is in good shape. Is the foam supposed to be really hard? I sure I could take a ballpoint pen and dig more out if I really tried, so does that mean I'm not to "good foam" yet? I'm just confused on what constitutes good foam. Thanks again!


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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 4:31 pm 
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ArizonaCat wrote:
A few more questions. Do I need fiberglass mat for this repair or are a few layers of fiberglass cloth enough?


2-3 layers of cloth should do it. Depends on the size of the hole when you are done sanding.

ArizonaCat wrote:
Secondly, is there an alternative to formula 27? None of my local West Marines carry it, although they said they could order it. I'd like to get this repair done by the end of the weekend though, so I'd rather not have to wait several days for an order if I can help it.


Not sure about this I always use formula 27. I guess you could use a West System filler to make really thick resin but it will not be as easy to work with.

ArizonaCat wrote:
Lastly, I understand from previous responses that "spongy foam" is bad. Well the foam directly below the gouge didn't seem to be in the best shape so I sanded it out, but I'm just not sure if the surrounding foam is in good shape. Is the foam supposed to be really hard? I sure I could take a ballpoint pen and dig more out if I really tried, so does that mean I'm not to "good foam" yet? I'm just confused on what constitutes good foam. Thanks again!


Good foam is clean, crunchy and dry. Bad foam is wet, dark and squishy. Core foam is not hard in either case. It's brittle and easy to compress. I would avoid digging out any more than you must. If you have concerns, you can inject the foam around the hole with Gitrot before you make the repair. That will take care of a potential issue. You can probably determine the state of the foam by tapping around the hole with a coin. If it the coin taps sound dull compared the rest of the hull you may have issues. If so do this...viewtopic.php?f=9&t=46828

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94' H16 - 100403
www.HobieFleet97.org
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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 4:47 pm 
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You don't need fiberglass mat, just use the woven cloth.

Formula 27 is a polyester based putty/filler. You can substitute it with thickened resin (like West 403 microfibers) or even Bondo in a pinch.

The foam core should be "crisp". You can dig it out with a sharp instrument, but it should not be "spongy". Did you do the coin tap test and did you check to see if the surrounding area of the hull is soft?

You should also try to examine the hole for signs of moisture. Sometimes if you inspect closely, you can see moisture/bubbles coming to the surface, especially if you leave the hull out on a hot/sunny day. You can also stick the edge of a rolled up paper towel into the hole and see if it wicks up any moisture. You definitely want to make sure the core is as dry as possible before you fix the hull.

My guess is that the previous owner sailed the boat with the crack in it and water penetrated into the core. It's not the end of the world, but it could lead to delamination down the road if not taken care of, so I would recommend you get it as dry as possible. I would probably drill a few vent holes through the outer skin in the "spongy" area (same as you would do for delam repair) and then leave the hull out in the sun for a few days or throw a lamp on it for a few days to get it dry before continuing with the repair.

sm


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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 5:11 pm 
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Thanks again for those replies, my understanding of this is getting better and better. I'm just a little intimidated by the project because the current fiberglass skin seems to be so thin that it seems like its going to be difficult to make the repair level with the existing skin, but I guess that's what sanding is for...


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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 5:16 pm 
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It's all about sanding, patience and more sanding! The great thing about fiberglass is you can sand away your mistakes and try again.

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Garrett
94' H16 - 100403
www.HobieFleet97.org
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 Post subject: Re: Small gouge in hull
PostPosted: Wed Mar 13, 2013 5:51 pm 
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How is this looking? It pained me like crazy to make the hole bigger, but I ground away more fiberglass that had the white damaged look. As you can see, the damage extended the length of the scratch. I also extended the amount of area where I sanded away the gel coat(and now have apparently made my 16 into a Hobie 10 :D ) Hopefully in the next couple days I can get ahold of some formula 27, since that's the one thing I don't have yet.
Image

Not gonna lie, I almost threw in the towel today--I called a few fiberglass places, but they all estimate $300+. I'm gonna try to do this myself and see if I can make it look decent.


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 Post subject: Re: Small gouge in hull
PostPosted: Thu Mar 14, 2013 3:45 am 
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First off, you're 1/2 the way there. Grinding out the hull is the hardest part (at least from a psychological stand point). I wouldn't pay someone $300 to fix a small area like this, especially if you're not concerned about it being cosmetically perfect.

I would probably grind back the gelcoat another 1/2" all around to increase the taper around the repair. The idea is that you want to add successively larger patches over the repair. So each patch increases by about 1/4 to 1/2 inch more than the previous patch (essentially creating an upside down pyramid of patches if you will). If you're careful and take your time, there actually won't be that much sanding required. So far, it looks like you're on the right track.

sm


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 Post subject: Re: Small gouge in hull
PostPosted: Thu Mar 14, 2013 7:29 am 
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Location: Clinton, Mississippi
FYI....Formula 27 is carried by local hardware stores around here.....or was the last time I bought it, at least.

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Hobie 16


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