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Re: SC15 bow - PICTURES BEFORE RECOATING [Re: TheManShed] #222695
10/26/10 10:22 AM
10/26/10 10:22 AM
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Asuncion, Paraguay
Luiz Offline OP
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Originally Posted by TheManShed
Looks like it was coming apart before the crack by the buckle in the hull. I’d take a jig saw and cut away the bad glass plus about 5” on each side in a rectangle shape. On the other hull, the good one in the same location prepare the hull with duct tape then wax to use as a mold. The hulls are pretty much symmetrical so the patch from the outside of the good hull will be for the inside of the bad hull……….so forth. I would also use Epoxy and not poly resin. I don’t recommend mat - no strength, use a biax and make one or two lay-up patch with about 4” larger than the damaged area. This will be your patch panel. I’d make 2 or 3 pieces that is a port , starboard, and deck patch.. Make one patch panel for each side and one for the deck. They will bend some so you can fit them inside the hull. Scuff the inside of the hull to get a good clean bite. Make sure all the wax is removed from the molding process. Clamp the panels in place and let dry. Also inspect the inside of the hull for any other damage before you seal it up and make sure bulkheads are attached to the hull. The seam is splitting to it needs to be ground smooth, filled and glassed over from the inside, and outside Taper the outside of the repair area then you can glue in foam or make a solid patch, and put your outside skin and finish. . West system has a short video on the repair of foam/fiberglass that covers the basics http://www.westsystem.info/wesyephodvd.html . I have some pictures of similar repair not as big and I used the cut out piece but the same idea http://themanshed.net/archived-projects/g-cat-catamaran/?g2_page=2 and http://themanshed.net/archived-projects/g-cat-catamaran/?g2_page=3
On the Supercat 20 I had to make a piece for the deck where a funky wood top patch was made. I made a temp mold of the other port hole and deck area, had to spin it 180 and correct the angle. http://themanshed.net/archived-projects/supercat-20.html Since you are close to the bulkhead make sure you do not cut into it and you can tie your patch into the bulkhead to make it stronger. Back then I used bondo type products for faring and have since removed all of it. Do not use plastic fillers they asorb water, it is best to make an epoxy paste with a filler it is a little harder to sand but much better.

I would not use the old piece of the SuperCat15 since it was failing and check out the skins around the cut-out to make sure it is sound.

It is getting late I worked too late in my shop so I need to turn in if you would like more detail you can contact me directly.


Excellent, many thanks!!!
I'll translate it to the shipyard owner and will be back with the doubts, if any.

In "I would not use the old piece of the SuperCat15 since it was failing" you mean the parts (scraps) cut around the failure area?

Cheers,
Luiz



Luiz
-- Have You Seen This? --
Re: SC15 bow - PICTURES BEFORE RECOATING [Re: Luiz] #222700
10/26/10 11:12 AM
10/26/10 11:12 AM
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Palm Beach County
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Yes

One thing to remember the hull is strong by the construction.
Inside skin /foam layer/ outside skin. They must be in 100 % contact and overlap in the repair making one single inside skin / foam layer / outside skin structure clear of any voids.

Last edited by TheManShed; 10/26/10 11:21 AM.

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

Re: SC15 bow - PICTURES BEFORE RECOATING [Re: TheManShed] #222722
10/26/10 02:18 PM
10/26/10 02:18 PM
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FL
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Please look at the bottom of the attached hyperlink.
You will observe the highest stresses are just away from the fixed support, when displacement is added.
http://web.mit.edu/calculix_v2.0/CalculiX/ccx_2.0/doc/ccx/node6.html

Oversimplifying the hull in front of the main beam acting as a cantilever, from statics the highest shear, bending moment, and torsion occurs at the main beam,
with the least rate of displacement due to bulkhead/reinforcement.

Traveling just a little ways from the main beam there is not only high bending, shear & torsion, but now add rate of displacement.
Cyclic section distortion (sans bulkhead) as the hull displaces under load (in,out,& twist) compress & uncompress the foam, as the fiberglass inner and outer skin is 10x stiffer than the foam.
The inner & outer layer move at different rates to accommodate hull distorsion, the foam eventually looses the battle.
The '70s Tornados added a bulkhead in front of the main beam for reduction of hull distortion/stress & bow deflection.

Re: SC15 bow - PICTURES BEFORE RECOATING [Re: TheManShed] #222726
10/26/10 02:34 PM
10/26/10 02:34 PM
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Asuncion, Paraguay
Luiz Offline OP
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Understood.

Closed cell foam is not available here. The alternatives are:

1) Recover foam from the cutout (it seems to be in good shape), glue the bits with epoxy over a thin layer of glass and reuse.
2) Wood. Planks, ply or laminated are easy to find. Heavier.
3) Glass mat. Makes a thik solid laminate. Heavier.
4) Styrofoam (high density). The repair doesn't extend to the keel, it is mostly above the waterline and the boat is never moored.
5) Open cell polyuretane foam (insulation type)

6) Combinate two or more. Maybe a few wood (or glass) battens laid longitudinally, with strips of recovered foam between them?

I can buy a PVC foam plank, but if they can't be forwarded by plane, it'll take about three months to arrive (planks ship truck only, apparently).
The foam appears to be 4 mm (5/32) thick, does this sound right? Brand and density unknown. Color is like sand - check the picture.

Thanks!

Attached Files
SC15 foam color.jpg (192 downloads)
Detail of delamination with foam color visible.

Luiz
Re: SC15 bow - PICTURES BEFORE RECOATING [Re: sail7seas] #222729
10/26/10 02:42 PM
10/26/10 02:42 PM
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Asuncion, Paraguay
Luiz Offline OP
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Originally Posted by sail7seas

Please look at the bottom of the attached hyperlink.
You will observe the highest stresses are just away from the fixed support, when displacement is added.
http://web.mit.edu/calculix_v2.0/CalculiX/ccx_2.0/doc/ccx/node6.html

Oversimplifying the hull in front of the main beam acting as a cantilever, from statics the highest shear, bending moment, and torsion occurs at the main beam,
with the least rate of displacement due to bulkhead/reinforcement.

Traveling just a little ways from the main beam there is not only high bending, shear & torsion, but now add rate of displacement.
Cyclic section distortion (sans bulkhead) as the hull displaces under load (in,out,& twist) compress & uncompress the foam, as the fiberglass inner and outer skin is 10x stiffer than the foam.
The inner & outer layer move at different rates to accommodate hull distorsion, the foam eventually looses the battle.
The '70s Tornados added a bulkhead in front of the main beam for reduction of stress & deflection.


Yes, the risk of skin/foam detachment is higher in this area - and this is what happened.


Luiz
Re: SC15 bow - PICTURES BEFORE RECOATING [Re: Luiz] #222736
10/26/10 03:22 PM
10/26/10 03:22 PM
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Gainesville, FL 32607 USA
dacarls Offline
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Hi Luiz,
I bought small sheets (0.5 m x 0.5 m) of stiff polyurethane foam 4 to 6 mm thick from internet contacts in the USA. It was sent by UPS to me ok. No large-scale "shipping".


Dacarls:
A-class USA 196, USA 21, H18, H16
"Nothing that's any good works by itself. You got to make the damn thing work"- Thomas Edison
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: erice] #222753
10/26/10 07:49 PM
10/26/10 07:49 PM
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Dunedin Causeway, FL
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Originally Posted by erice
ouch! there are a few pics about of snapped off supercats bows, maybe they can be dug up here?


Here's a little SC-17 hull damage. It looks like this one was helped along by too much dragging the hull up the beach. That "sanded off" the seam along the bottom.

A little epoxy, a little duct tape, and it's back on the water, eh?
"Tis but a scratch" (Monty Python, Black Knight)

Attached Files
SC - Hull 1.jpg (171 downloads)
SC - Hull 5.jpg (170 downloads)
Re: SC15 bow - PICTURES BEFORE RECOATING [Re: dacarls] #222815
10/27/10 05:55 PM
10/27/10 05:55 PM
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Asuncion, Paraguay
Luiz Offline OP
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Originally Posted by dacarls
Hi Luiz,
I bought small sheets (0.5 m x 0.5 m) of stiff polyurethane foam 4 to 6 mm thick from internet contacts in the USA. It was sent by UPS to me ok. No large-scale "shipping".


Interesting. Any details, like if it is closed cell, the density and price?


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: David Parker] #222816
10/27/10 06:15 PM
10/27/10 06:15 PM
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Asuncion, Paraguay
Luiz Offline OP
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Originally Posted by David Parker

Here's a little SC-17 hull damage. It looks like this one was helped along by too much dragging the hull up the beach. That "sanded off" the seam along the bottom.

A little epoxy, a little duct tape, and it's back on the water, eh?
"Tis but a scratch" (Monty Python, Black Knight)



Do you know if this one was fixed or scapped?

Ours just looks better, but in fact only the keel and half of one side keep the bow from falling apart. I can probably break it using my hands only.


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Luiz] #222817
10/27/10 06:24 PM
10/27/10 06:24 PM
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japan
erice Offline
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in the usa you wouldn't fix that
you would either part it out and recover most of the boats cost
buy another hull
or buy another supercat


eric e
1982 nacra 5.2 - 2158
2009 weta tri - 294
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: erice] #222823
10/27/10 07:57 PM
10/27/10 07:57 PM
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Asuncion, Paraguay
Luiz Offline OP
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Originally Posted by erice
in the usa you wouldn't fix that, you would either part it out and recover most of the boats cost, buy another hull or buy another supercat


Right, much like you do with the cars, they are saved only when truly loved by the owner, which could be the case, I guess.

Here we have different price structure, tax regime, labour costs and availability of parts/boats. As a consequence, the rational decision is often different, even if the boat's state is about the same.

Cheers,


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Luiz] #222858
10/28/10 08:39 AM
10/28/10 08:39 AM
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Houston
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The advice you are taking looks very good. I like to add a couple of things. Tell the yard:

The taper on the original hull were it meets the patch should be 8-10 to 1 and I would use light (2-3 ox/yd) cloth for the repair.

They should seal the foam as a separate step after the taper, coat with epoxy and let it dry before you add anything else.

A good core material for this type of repair is core mat:

http://fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html

It can folded like cloth so shipping costs are reasonable. I was told once that you can make something similar by coating both sides of ~1 oz/yd fiberglass with epoxy micro balloons. The epoxy micro balloons mixture should be what West Systems calls peanut butter thick. I have not tried this since core mat is cheap for me.

My personal preference is to use Kevlar for the inner patch. Kevlar tends to hold even after glass or carbon cracks. I have made it to shore twice because I used a layer of Kevlar in my laminate.

Good Luck

Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: carlbohannon] #222871
10/28/10 10:46 AM
10/28/10 10:46 AM
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Luiz Offline OP
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Originally Posted by carlbohannon
The advice you are taking looks very good. I like to add a couple of things. Tell the yard:

The taper on the original hull were it meets the patch should be 8-10 to 1 and I would use light (2-3 ox/yd) cloth for the repair.

They should seal the foam as a separate step after the taper, coat with epoxy and let it dry before you add anything else.

A good core material for this type of repair is core mat:

http://fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html

It can folded like cloth so shipping costs are reasonable. I was told once that you can make something similar by coating both sides of ~1 oz/yd fiberglass with epoxy micro balloons. The epoxy micro balloons mixture should be what West Systems calls peanut butter thick. I have not tried this since core mat is cheap for me.

My personal preference is to use Kevlar for the inner patch. Kevlar tends to hold even after glass or carbon cracks. I have made it to shore twice because I used a layer of Kevlar in my laminate.

Good Luck


Great advice Carl, thanks!
My boat's floats used coremat as buildup between coats for increased stiffness in some points.
Tomorrow I'll meet with the guys in the shipyard and make the final plan - and will post it here, obviously.

Cheers,


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Luiz] #222895
10/28/10 04:54 PM
10/28/10 04:54 PM
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toronto, canada
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http://www.noahsmarine.com/
just order 1 sheet of the proper sized corecell, contour cut.

Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: basket.case] #222937
10/29/10 08:05 AM
10/29/10 08:05 AM
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As you can see everybody has ideas on how to fix it. You have to trust the person doing the work to blend the ideas.
My thought...Kevlar good on the inside doesn't sand well so it's good for an inner wet lay-up. Coremat I've used it for bulk and some stiffness no strength. Foam use boat build quality nothing else. Wood - never.

Good luck


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

Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: TheManShed] #222977
10/29/10 08:24 PM
10/29/10 08:24 PM
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Luiz Offline OP
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Originally Posted by TheManShed
As you can see everybody has ideas on how to fix it. You have to trust the person doing the work to blend the ideas.
My thought...Kevlar good on the inside doesn't sand well so it's good for an inner wet lay-up. Coremat I've used it for bulk and some stiffness no strength. Foam use boat build quality nothing else. Wood - never.

Good luck


Yes ,lots of good instructions! I discussed them today with the shipyard owner and have good news, mostly:

1) The foam aparently isn't a problem. One of his providers in Argentina has Divinycell and will ship truck (700 miles). Many thanks for all the sources indicated!

2) Realignment of the bow with the rest of the boat will be easier than I thought. The broken hull fell almost exactly in its normal place once turned upside down. Looks like the keel is ok.

3) He is familiar with the suggested techniques and says that his people can execute any of them. As you expected, he combined methods and added a few of ideas of his own.

We found a few other damages, all on the same bow, but not nearly as bad. Anyway, the current plan is the following:

1- Cut a rectangle from the center of the deck to below the end of the fupture on the inner float wall (the big rupture).

2- Use the opening made to inspect the inside and confirm or adjust the rest of the plan.

3- Patch the inside skin of the outer side of the float (smaller breakage), adding a longitudinal carbon batten between the two layers (windsurfer batten). He wants the battens to obtain more stiffness on the horizontal plane. On the vertical the keel and deck are far appart.

4- Laminate a one layer patch from the intact hull (waxed).

5- Remove the patch, clean the wax and laminate a second layer where the wax was, with two longitudinal carbon battens inserted between the two layers.

6- Clamp the battened patch to the rectangular hole.

7- Remove only the damaged foam and/or outside skin from the smaller rupture on the outer side of the float.

8-Glue new foam to the inner skins.

9- Sand, chamfer and clean the edges of the outer skin for the repair.

10- Laminate the outer skin (two layers), sand, coat and finish.

He'll do everything with epoxy/biaxial glass (but for the batttens). What do you think?
Cheers,


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Luiz] #222987
10/30/10 07:06 AM
10/30/10 07:06 AM
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Ft. Pierce, Fl. USA
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The carbon battens and the fiberglass have differing strengths and modulus of elasticity...It is a case of divide and conquer...the carbon battens will be loaded up and take all the strain before the glass comes fully into play...after the battens fail you are just back to whatever glass cloth was used...it all has to work in unison and I am afraid the carbon battens and the fiberglass (more than likely E-glass) are too different in physical properties. That is something the windsurfing community found out back in the 80’s…it sounded good that the builders put a hybrid carbon cloth in the laminate, I saw one F2 board broken in half…they had a cloth with every 4th or 5th thread in “0” orientation was carbon fiber, the rest were E-glass. Others would add a few 1” carbon tows on a “0” axis along in the glass with the same failing results. Again…it is a case of divide and conquer. The carbon gets loaded up… fails, and what is left is just the glass…and because the builder was relying on the carbon as this miracle material, they used a lighter glass laminate…bam…catastrophic failure. There is more to adding carbon to a laminate than meets the eye..

Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Seeker] #222989
10/30/10 07:31 AM
10/30/10 07:31 AM
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Everything is good instead of battens form the same glass as used for the repair, less carbon, around a small diameter paper tube then cut it in half length wise. Use that instead of the batten


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

Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: TheManShed] #222998
10/30/10 11:18 AM
10/30/10 11:18 AM
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Luiz Offline OP
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Understood, in this type of repair one fiber type alone will work better than a mix of fibers. Many thanks to both of you!

I wonder if it makes sense to mold glass battens directly over the healthy hull, together with the patch lamination.

A question:

The inner skin will result stronger than the outer skin. I'd feel safer with the opposite. Considering that we'll have a relatively wide access to the inside, is it possible to patch the OUTER skin from the inside? (At least the big rupture?)

It would require the opening of a wider rectangle from the inside, by means of removing only the foam and inner skin to leave enough space for the patch under the outer skin repair.

The patch would be glued to the outer skin and then glassed from the outside to the right thickness. Afterwards, foam and inner skin would be glued to the inside. Or maybe the foam could be pre glued to the patch...

The other repair method would be used for the smaller rupture (or deck)

Cheers,


Luiz
Re: Advice on fixing a nearly chopped Supercat 15 bow [Re: Luiz] #223000
10/30/10 12:02 PM
10/30/10 12:02 PM
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Ft. Pierce, Fl. USA
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I did something like that on a power boat to close up two large holes in the liner (8" X 32"). If the compound curve is not too extreme, use a piece of 1/32" gloss finish laminate (formica)cut oversize for a form .Taper everything well on the inside of the hull, then use contact cement to temp glue the Mica around the perimeter of the hole on the outside surface of the hull(or if the compound curve is too great take a mold off the good hull) and build up everything from the inside. After the repair you can break the bond of the contact cement with laquer thinner, wipe it clean with out a trace. Of course you have to have release wax where the actual repair lays against the form. Worked extremely well for me.

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