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NACRA 5.0 hull repair (structural?) #234979
07/19/11 09:14 PM
07/19/11 09:14 PM
Joined: Sep 2009
Posts: 11
Corpus Christi Bay, TX
ccmac Offline OP
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(re)broke my hull just below the aft crossbeam last week--not sailing hard, just 15kts & smooth water. It's a well-used '83 nacra 5.0 in Corpus Christi, TX, but the hulls are otherwise OK. I paid a "pro" to repair a nearly identical crack last summer, but then only got a few months of sailing out of it before it came back. To my untrained eye, this looks like a long history of sloppy repairs. Without any experience with fiberglass work, I'm hesitant to tackle a job where others have failed. I'd be more willing to experiment if it were a more vanilla hull puncture, but this looks structural. Any suggestions, or is it time to part the old girl out on craigslist?

Josh

[img]http://www.flickr.com/photos/12713306@N02/5952705329/[/img] [img:left]http://www.flickr.com/photos/12713306@N02/5956037171[/img]


Josh
'83 Nacra 5.0 - 1075
-- Have You Seen This? --
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235008
07/20/11 06:04 PM
07/20/11 06:04 PM
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japan
erice Offline
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that is a highly stressed area, but it should be possible to rebuild it as strong is enough overlapping glass is used inside.....................but you'll need a structural repair, not a cosmetic repair

any pics of the inside?

were you aware that the "chip" on the strap is upside down and backwards? that would have a tiny effect on how the bolt worked the captive nut....


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: NACRA 5.0 hull repair (structural?) [Re: erice] #235010
07/20/11 08:42 PM
07/20/11 08:42 PM
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Corpus Christi Bay, TX
ccmac Offline OP
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http://www.flickr.com/photos/12713306@N02/5955981911
http://www.flickr.com/photos/12713306@N02/5956037171

Here are two photos from the interior.

I had no idea about the chip upside down and backwards--it was like that when I bought it two years ago. How should it be oriented?

How would you describe the difference between structural and cosmetic repairs?

Josh


Josh
'83 Nacra 5.0 - 1075
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235023
07/21/11 09:07 AM
07/21/11 09:07 AM
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Lake Norman. NC
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Originally Posted by ccmac

How would you describe the difference between structural and cosmetic repairs?


If you can fix it with less than one roll of duct tape, it's a cosmetic repair. Any more than one roll, it's structural.

Re: NACRA 5.0 hull repair (structural?) [Re: erice] #235028
07/21/11 10:05 AM
07/21/11 10:05 AM
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Posts: 890
Dunedin Causeway, FL
David Parker Offline
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Quote
were you aware that the "chip" on the strap is upside down and backwards? that would have a tiny effect on how the bolt worked the captive nut....


I disagree. It looks like the curved edge of the "chip" is down and toward the strap so the strap follows the gentle curve of the chip rather than its sharp corner. The old 1985 Nacra manual says, "Be sure the curved edge of the black chip is down so that the strap takes the same curve as the black chip." There is a round edge on both ends so you have to look closely. I think he has it right.

However, I doubt that this caused the hull to fail. The cool thing about fiberglass is that if you think large you can cut open the hull, lay down significant glass and resin, put in a new backing plate for the bolts, and then do a good gel coat repair. It will be as good or better than new. You just have to think major and not think just skin repair. It's not hard work, you just have to be committed to the bigger fix and be willing to get out the chain saw for that first cut. After that it's play dough and paint. Don't abandon the boat over this.

Re: NACRA 5.0 hull repair (structural?) [Re: David Parker] #235047
07/21/11 05:16 PM
07/21/11 05:16 PM
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erice Offline
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- as long as a curved face of the chip is against the curve of the strap then it's right, think my 1982 chips have only 1 curved edge, but if these chips have 2 that would explain why you can see 1 of them NOT against the curve of the strap...

- i would define a cosmetic repair as 1 where someone with next to no knowledge of frp structures went in to "make it look like new" (like maybe a car repair shop worker) and a structual repair as 1 where someone who had a reasonable sense for frp and beam loads on a beach cat when in to "make it stronger than before"

- the pics of the inside look pretty ugly to me, ie cosmetic repair was done by someone with no real idea of frp repairs

- repairing a botched repair is harder than simply repairing a break/crack so if i were you i would be asking around at boat shops for someone who builds or repairs boats to have a look at you hull and quote a repair.....with only a basic understanding myself i would think you need at least 3 overlapping layers of woven cloth on the inside and maybe the same on the outside, which would take a lot of finishing...


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: NACRA 5.0 hull repair (structural?) [Re: David Parker] #235048
07/21/11 05:37 PM
07/21/11 05:37 PM
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Corpus Christi Bay, TX
ccmac Offline OP
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How large should I think here? Am I looking at cutting out an inch or two around the fissure, or should it be a basketball-sized hole to fill in and mold?

Is there anything you can see in the pictures to suggest what mistakes were made in the earlier repair attempts? Any speculation? I'd be more comfortable tackling the project if I knew what NOT to do.

Thanks for all the wisdom and encouragement,
Josh

Last edited by ccmac; 07/21/11 05:39 PM.

Josh
'83 Nacra 5.0 - 1075
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235050
07/21/11 07:28 PM
07/21/11 07:28 PM
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japan
erice Offline
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hopefully someone more knowledgeable will step in...until then

- the internal pics seem to show a putty/cosmetic repair and not a woven cloth/structual repair

- you want to aim for something like
1. cleaning out the previous repair's? bondo and getting down to woven glass on both sides...this will be easy on the outside and difficult on the inside

2. putting a small patch of woven glass over the bare crack that overlaps all areas by about 2 inches

3. putting a 2nd patch on top that overlaps by about another 2inches

3. putting a 3rd patch over that with another 2 inch overlap

4. let set, fill crack void on other side with chopped up glass and resin, let set, grind flat

5. repeat 3 layer repair on other side, let set

6. fair outside repair with filler

7. brush over white gelcoat


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: NACRA 5.0 hull repair (structural?) [Re: erice] #235103
07/22/11 05:50 PM
07/22/11 05:50 PM
Joined: Aug 2001
Posts: 1,307
Asuncion, Paraguay
Luiz Offline
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Originally Posted by erice
hopefully someone more knowledgeable will step in...until then

- the internal pics seem to show a putty/cosmetic repair and not a woven cloth/structual repair

- you want to aim for something like
1. cleaning out the previous repair's? bondo and getting down to woven glass on both sides...this will be easy on the outside and difficult on the inside

2. putting a small patch of woven glass over the bare crack that overlaps all areas by about 2 inches

3. putting a 2nd patch on top that overlaps by about another 2inches

3. putting a 3rd patch over that with another 2 inch overlap

4. let set, fill crack void on other side with chopped up glass and resin, let set, grind flat

5. repeat 3 layer repair on other side, let set

6. fair outside repair with filler

7. brush over white gelcoat


Use structural epoxy, not polyester resin.


Luiz
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235152
07/24/11 04:37 PM
07/24/11 04:37 PM
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Corpus Christi Bay, TX
ccmac Offline OP
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Here's a peek at the teardown process including some good profile views of what the last repair was like. Plenty of glass there, but it looks like they layed it down in 2-3 separate panels with few if any sheets making the turn THROUGH the corner...mostly just lots of bulk epoxy in the joint that had started crumbling.
http://www.flickr.com/photos/12713306@N02/5971258523
http://www.flickr.com/photos/12713306@N02/5971820112
http://www.flickr.com/photos/12713306@N02/5971817742
-Josh


Josh
'83 Nacra 5.0 - 1075
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235163
07/24/11 08:34 PM
07/24/11 08:34 PM
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japan
erice Offline
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looks like you've got the idea. what you need is LOTS of glass fibers running ACROSS the break and then solidly bonding to good glass over a wide area. try not to cut the cloth for the patches so that only 1 weave will cross the break. turn the cloth diagonally and cut it so both weaves cross the break. bi-axial. again, the 1st patch could cover the entire crack by 2inches and be bonded to nicely roughed up glass. the 2nd patch goes over the 1st patch while it is still wet and overlaps it by another 2" and is bonded onto a new area of lightly ground off glass. 3rd patch etc.

if it looks like getting 3 good patches down inside the hull is going to be next to impossible you could beef up the repair by adding a 4th layer to the outside.

for the strongest repair you'll want to use the heaviest cloth that will make the bends. this may mean laying some plastic film over each layer and taping it down until it has hardened enough to keep it's shape. then peeling off the plastic while the resin is still tacky and laying the next layer on top etc.


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: NACRA 5.0 hull repair (structural?) [Re: erice] #235810
08/07/11 05:15 PM
08/07/11 05:15 PM
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Corpus Christi Bay, TX
ccmac Offline OP
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After finishing up the sanding & grinding, I created a backing piece to glue onto the inside of my gap. I molded cardboard and covered it with plastic packing tape to match the interior profile of the hull corner. I laid two pieces of wet-out 6oz fiber cloth onto the mold, and peeled it away when cured. The backing piece glued almost perfectly into the hull's interior with some ketchup-y resin+colloidal silica. I filled the low spots above the backing piece with filler & now I'm ready to start laying glass inside and out--hopefully three more layers inside and at least three on the outside.
http://www.flickr.com/photos/12713306@N02/6019754000


Josh
'83 Nacra 5.0 - 1075
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235817
08/08/11 03:16 AM
08/08/11 03:16 AM
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japan
erice Offline
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repair all looks good

that 2nd inspection hatch, which i think someone has put in forward of the beam, could cause problems down the track though...


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: NACRA 5.0 hull repair (structural?) [Re: ] #235853
08/08/11 01:55 PM
08/08/11 01:55 PM
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Palm Beach County
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OK here is my 2 cents worth:
I've made repairs like this before and an outside patch will work for a while as evident with the last fix. But to make a strong fix cut a hole in the inside of the hull as an access port so you can get in and fix the area from the inside. Then fix it from the outside. The last step will be to fix your access hole. Here is a link to the type of repair I'm talking about:
http://themanshed.net/archived-projects/g-cat-catamaran/?g2_page=2
Few other things Iíve learned from experience use epoxy not a poly resin it just holds better and donít use Bondo or plastic filler it will swell and absorb water. Do not use any fillers where your cross beam touches the fiber glass. The lay-up under the cross beam should be long pieces Ė no seams. Remember Mat has no strength. I use a woven biaxial or triaxial. Budweiser or Rum usually helps with the fiberglass itch if taken early enough.


Mike Shappell
www.themanshed.com
TMS-20 Builder
G-Cat 5.7 - Current Boat
NACRA 5.2 - early 70's

Re: NACRA 5.0 hull repair (structural?) [Re: erice] #235934
08/09/11 12:26 AM
08/09/11 12:26 AM
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Corpus Christi Bay, TX
ccmac Offline OP
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Erice,
What kind of problems are you imagining for the inspection hatch? I already poked my boney butt through one on the opposite hull about a year ago, but that was an easy replacement.

Outside is glassed over with at least three layers of 60oz biaxial cloth all over & up to 6 or seven around some of the corner areas. Next up I'll be laying a similar mess on the inside corners.
http://www.flickr.com/photos/12713306@N02/6024347439

Last edited by ccmac; 08/09/11 12:28 AM.

Josh
'83 Nacra 5.0 - 1075
Re: NACRA 5.0 hull repair (structural?) [Re: ccmac] #235939
08/09/11 07:00 AM
08/09/11 07:00 AM
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japan
erice Offline
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erice  Offline
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i think the hatches on the 5.0 should be like the 5.2

1 behind the aft beam

and 1 behind the main beam

your early series of photos show what look to be the inside of the hull forward of the beam, presumably your lowered your camera through a hatch forward of the beam

your later photos also seem to show a hatch forward of the beam

the factory presumably doesn't put hatches there as it is 1 of most highly stressed hull areas. there are huge loads in all directions from those long unsupported bows which is why when you see photos of collapsed cats it is usually the bows that have snapped off just forward of the main beam

you might get away with simply monitoring that area very closely or it might be better to remove the non-standard hatches there and glass in the holes



eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294

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