Need repair advice

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DanBerger
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Posts: 275
Joined: May 3rd, 2004, 3:29 pm
Boat Make/Model: SC 15 w/ spin!, SC 19
Location: Norfolk, VA

Need repair advice

Post by DanBerger » April 19th, 2017, 12:43 pm

One of our local SC sailors picked up a 1981 Boston Whaler built 15 a few years ago and the previous owner had made some not-so-pretty repairs. One of the sterns looked like it was ripped off and patched back on and never finished. It looks like a good repair, but it needed a LOT of work. I have spent HOURS sanding and faring and I have it looking pretty good now. I was more curious about how the repair was done and I wanted to verify that it was safe.

The other problem is what I need some help with.

there is a crack that has been (poorly) repaired on the inside of the bow in front of the front beam. It is right in the 'bad' spot for the hull to break. It looks like it had some resin built up in it, but no glass. Then, the PO gooped on some white filler. It lasted a few years, but it started to open up and crack again last year which makes me think that it was flexing at the repair.

I couldn't let it go, so I started grinding on it. Pictures are below. I ground off the gel out pretty far, but I don't think it is far enough. It looks like the glass was delaminating from the foam around the old wound. I have since laid a strip of glass from top-to bottom of the ground out area about 1.5 inches wide. I used a foam brush to push the resin all over the area and under the glass that was there. I then used packing tape to smooth it out. I plan on adding two more glass strips about 3 inches wide, then 5-6 inches wide. I don't think I will be able to get it level with the surface of the hull, I just don't think it would be enough glass.

In one of the pictures, you can see some dark dots on the left side of the ground-out area. I'm thinking those are attachment 'points' for the bulkhead?

So my question is: have I created a large enough area to fix the crack? Do I need to enlarge the area at all--to the side or vertically? I feel like I need to get at it from the back side but I'm not crazy about cutting out more holes on the other side. If I had to, I need advice on where to cut so I can avoid the bulkhead. That is, if there is a bulkhead there.
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IMG_4394.JPG

DanBerger
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Posts: 275
Joined: May 3rd, 2004, 3:29 pm
Boat Make/Model: SC 15 w/ spin!, SC 19
Location: Norfolk, VA

Re: Need repair advice

Post by DanBerger » April 19th, 2017, 12:44 pm

Closeup of old repair:
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IMG_4395.JPG

DanBerger
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Posts: 275
Joined: May 3rd, 2004, 3:29 pm
Boat Make/Model: SC 15 w/ spin!, SC 19
Location: Norfolk, VA

Re: Need repair advice

Post by DanBerger » April 19th, 2017, 12:46 pm

ground out area and close-up:
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IMG_4396.JPG

DanBerger
Professional
Posts: 275
Joined: May 3rd, 2004, 3:29 pm
Boat Make/Model: SC 15 w/ spin!, SC 19
Location: Norfolk, VA

Re: Need repair advice

Post by DanBerger » April 19th, 2017, 12:46 pm

Close-up
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IMG_4397.JPG
Last edited by DanBerger on April 19th, 2017, 12:52 pm, edited 1 time in total.

gahamby
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Boat Make/Model: SuperCat 15#315
Location: Falls Church VA 22042

Re: Need repair advice

Post by gahamby » April 20th, 2017, 10:18 am

Does the crack go into the inside layer of glass?

DanBerger
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Re: Need repair advice

Post by DanBerger » April 20th, 2017, 10:46 am

I'm not sure, I didn't dig out any of the foam. I have a feeling, though, that it is probably delaminated on the back side. I'm thinking that I could make a much larger hole, dig out all the foam, then lay a few sheets of glass onto the back side glass and then fill the area with filling and then lay a few layers of glass on top?

This would all be done from the top, not going into the hull from the other side.

I have the same issue going on with a 20, so I'm interested in the correct fix.

gahamby
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Re: Need repair advice

Post by gahamby » April 25th, 2017, 11:52 am

I think you have the right idea. I would want to know that the inner layer of glass was solid. If you could get the repair area horizontal it would be a help.
If the inner lamination is fractured you could try getting the repair horizontal and inverted overhead. Then you could inject resin into the fracture and let gravity be your friend.This does involve a lot of gymnastics in positioning the hull.

How thick is the foam core in that area? I'd like to hear from Matt on this one.

Matt Haberman
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Re: Need repair advice

Post by Matt Haberman » April 25th, 2017, 10:10 pm

Sorry for the late reply.

- For starters I would agree that you want to grind out the fractured core. It is most likely fractured all the way through to the inner skin, however if it isn't fractured all the way through then you could stop as soon as the fractured material is removed. For reference the core in that vintage of hulls is most likely 1/4" thick, although it could be 5/16" thick.

- Regardless of how much of the core you have to remove you want to taper it out over several inches. You want the transition back to the outside of the hull to be gradual.

- Be careful when removing the the core down to the inner skin. The inner skin is fairly thin and you don't want to damage or remove it unless it too is damaged. You should also note that there are significant reinforcements around the beam area and the core is tapered away by the beams. These reinforcements are visible on the right side of your repair photos, however I think you are still in the area where the core is full thickness.

- If you end up removing the core and find that the inner skin is also damaged you should pre-fabricate a small flat backing "plate" This can be made from a few layers of woven cloth on a flat table covered in wax paper. When this is cured you can trim it out so that it is roughly 2" larger then your opening in all directions. This should be flexible enough that you can fish it inside the hull and bond it into place on the inside of the hull, covering the opening. Make sure you sand the entire plate very well so it will bond to the inner skin. You can use resin thickened with cabosil as your glue.

-With the plate on the inner skin you can add another layer of glass on the outside of the hull, this should run out onto the tapered core.

- At this point I would vacuum bag in a replacement piece of core that is tapered to match the repair area. Going to need a good vacuum pump to do this, your shop vac isn't going to cut it.

-With the core bonded back in place I would then vacuum bag the patches over the repair area. Each patch is progressively larger until tapered back out onto the existing outer skin.

- Fair back in with body filler and then re-gelcoat or paint the hull.

I should finish by saying that this is a significant repair in a highly stressed area of the hull. If done properly the repair will outlast the rest of the hull, if it is not done correctly it will probably hold up for a while, just a matter of how long it will last and how catastrophic the failure will be.

Good Luck!

PS: The dark spots in the core are resin that bled through the perforations in the core.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com

gahamby
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Re: Need repair advice

Post by gahamby » April 26th, 2017, 10:32 am

Matt, Thanks for the reply.
I had considered the through the crack backing plate method.
Let us know how it goes Dan.

DanBerger
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Re: Need repair advice

Post by DanBerger » April 26th, 2017, 11:45 am

I was thinking about that through the crack thing, too. I'm just not sure how I can get the resin to coat the inside of the hull, much less cleaning the inside of the hull.

So, what I'm thinking--I'm pretty sure there is a crack in the inner layer. I can do Matt's trick of making a patch and getting it to the inside of the hull. Ill make a flat strip of glass out of a few layers of mat glass. I'll need to make the hole larger to get the backing patch through and I think I can do some cleaning on the inside with a wire and cloth. I'll run a line through the patch so I can pull it out so that it will match the curve of the inside of the hull. I have West system Epoxy and some adhesive additive that is super strong--it is what I have so, I kinda have to use that.

That should take care of the back and seal it up. I'm definitely taking pictures.

So, on the core issue--what can I use for the core?? I don't have a vacuum pump, I'll probably get one, but what is the difference if I just keep layering up the hole with glass?

Matt Haberman
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Re: Need repair advice

Post by Matt Haberman » April 26th, 2017, 5:18 pm

Dan,

- If you use thickened resin you can "spread" it on the inside of opening using a putty knife or tongue depressor.

- Regarding glass mat, don't use it. Get woven cloth it is 100x better then glass mat.

- The core will make the repair lighter and will mimic the flex characteristics of the surrounding area. You could do it all out of glass but it will be heavier and will act differently then the surrounding laminate. That difference could result in a stress riser adjacent to your repair and a new potential failure location. Regarding core material, if you give Tom a call he should have something that would work.
Matt Haberman
Aquarius Sail Inc.
http://www.aquarius-sail.com

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