What Is In A Chine

H

hardee

New member
Over the last month I have been working under my boat, cleaning, scraping barnacles, checking on the trailer bunks etc. One of the more disconcerting findings is what appears to be a crack, more like an absence of gel coat, rather than a fracture resulting from a strike. It is right at the apex of the chine. Looking down from above (like from inside the hull, it would be looking down into the bottom point of the “V” where the topside makes the curve around the downward pointing edge of the chine), and recurves back up to the hull.

For most of the length (about 3 ½ feet) the “crack” is barely wide enough to get a finger nail into and about that same depth, 1/16” or so for an average. There are a couple of places where it is 3/16” wide and 1/8” deep. These are about 2” long and still right at the apex of the chine. The aft most part of the “crack” is about 3 feet forward of the transom, and it is all on the starboard chine.

Today I used a dremel and ground into the larger “crack” about 1/8th inch. It appears to be going into intact resin, maybe fiber edges. I am wondering what is in that chine? Is it solid fiberglass with glass matt and resin? Would there be a wood runner through there? Where it curves up from the point of the chine to meet the flat hull bottom is almost 1.5 inches. If that is all solid, I might be in good shape yet.

I currently have two opinions on a fix, and am wondering which way to go.

Fix #1. Grind it out the full length, about 1/8th inch deep with the dremel and fill with gelcoat resin or paste.

Fix # 2 Grind the whole chine down about 1/8th to ¼ of an inch, and then cover with resin, and glass matt or tape, and build it up for the strength.

The concern is that the gel paste would not provide structural strength needed to maintain the working edge of the chine. Fix #2 would entail considerable more material and time (and $$$) but may be the “right thing to do”. I will do that if it is what is needed. If fix #1 would not compromise the strength (and the boat does not rest on this chine on the trailer), then maybe the gel paste would be an adequate solution. It certainly would not be a cosmetic concern as none of that would be visible without crawling under the boat when it is on a trailer. Fix #2 would entail a well matched color and would be visible as the bottom ½ to 1 inch of the chine for about 3-4 feet.

This issue needs to be taken care of before I do bottom paint, yes, but I still want it done right before the bottom paint. I don’t want the bottom paint to be a cover up.

Yes I know pictures would be great, and I can take them, just not sure I can get them into the CBRATS site.

Any input would be appreciated. I have an appointment coming up with a “repair” guy on Monday, so I need to decide soon. Thanks again.

Harvey
SleepyC:moon

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Harvey, you may have had an imperfection in the original layup, in the form of an air bubble, bizarre as it sounds, which lay between a thin layer of gel coat against the mold and the first layer of glass. As normal wear and tear wore away that thin layer, the bubble became exposed.

It does not sound like a crack, because of the variation in the width.

I would mix some milled glass fibers into catalyzed resin (or, epoxy) along with some Cabosil or other fumed silica to a peanut butter consistency and fill the void a little proud after roughening the interior surface of the void with a small rattail file.

Allow it to cure.

Gently block sand with 80 grit to a fair surface, and then wet sand down with 150 grit or 220 grit. Call it good, since bottom paint will cover this up anyway, and proceed with bottom paint.
 
Other than the transom, the decking above the v-berth, the cockpit floor (and some other horizontal surfaces) the remainder of the boat is fiberglass with no stringers or other material internal to it.
 
My guess would be with AstoriaDave on this one. Bubbles in the layup are much more common than we would like to believe. If they remain below the surface, we never see them and they're not a problem. If the much weaker gel coat fails over one, they are exposed and cause a panic. Yours runs in a direction that suggests a crack, but it is also the direction where the mold could cause a bubble between layups.

You might be able to get in with good magnifying glass or jeweler's loup and take a look. A structural crack will have sharp edges and exposed glass fibers. A bubble will have rounded resin walls inside of what looks like a crack.

If I am understanding the area, it is the chine where the side of the hull meets the bottom. Since the bottom is balsa core, you might think that the chine area is fiberglass over balsa. When I was drilling out my seat box holes, I drilled from the inside about 1 inch away from the chine. In quite a few places the hole showed balsa core towards the center of the cockpit and fiberglass and resin towards the chine. That told me that the balsa core is laid up an inch away from the chine and the chine is solid fiberglass for an inch. A bubble on the exterior would not be a problem.

Also, I think that for a structural crack of several feet there would be some evidence of a past impact.

Mark
 
Thanks for the replies.

1. If it was the result of an impact there should be some evidence (like a compression, dent, fracture lines like on a glass windshield maybe.) None of that here.

2. It doesn't look like a bubble where the top (or bottom), broke out. It just doesn't look like it ever filled; sort of rolled edge like a pancake edge in the fry pan.

3. I like the idea of the thickened paste for filling, especially if there is no need for structural reinforcement. The fun part is laying on my back and spreading this 12 inches above my face. :shock: :wink:

Any other thoughts are welcome.

Harvey
SleepyC :moon

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hardee":2087ela1 said:
3. I like the idea of the thickened paste for filling, especially if there is no need for structural reinforcement. The fun part is laying on my back and spreading this 12 inches above my face. :shock: :wink:

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The milled glass fibers are important ... they add needed strength to the resin mix. With added thickener, should be able to dab it into the crack and squeegee it into position, even overhead. Experienced folks can make these mixes in a small sandwich bag, cut a corner, and squeeze it out just like decorating a cake. I just slap it on and squeegee away, the Neanderthal method! :wink :wink
 
Agree mostly with AstoriaDave. As the boat is molded the "chine" is reversed, at a different and reverse angle from the rest of the hull bottom. There is no wooden stringer etc. There may or may not be core material over this glass, but often is. The downward turn is gong to be solid glass. When you have an acute angel down in the mold--often ti is not adequately filled with glass--and a defect may show. This is going to be mostly mat--I don't know if a chopper gun was used on your boat, but if it were, then this probably would have been filled mostly with chopped strands. It is too acute an angle to get 24 oz roving--one of the main structural components of the hull into this area. The roving would have been placed on top of the "void" of the reversed chine, and then rolled up the side with a more obtuse angle.

Agree ont he milled fiber--and I would use epoxy resin for better secondary bonding.
 
I have a 2007 22' cruiser. I have noticed a few similar places that look like the gel coat has shrunk, exposing glass below, and the glass appears to be cracked at the edge. There is a small, shallow crack as described above. This has happened at the turn of the chines in a few places near the water line, and also where the bottom meets the transom. Can this happen if the mold is not properly prepared or if the gel coat is not applied thick enough? It is not structural; I have probed with a pick and it is less than 1/16" deep.
 
cbgale":3gmmqao4 said:
I have a 2007 22' cruiser. I have noticed a few similar places that look like the gel coat has shrunk, exposing glass below, and the glass appears to be cracked at the edge. There is a small, shallow crack as described above. This has happened at the turn of the chines in a few places near the water line, and also where the bottom meets the transom. Can this happen if the mold is not properly prepared or if the gel coat is not applied thick enough? It is not structural; I have probed with a pick and it is less than 1/16" deep.
Click to expand...

Sounds like our boats are related. I agree, I don't think it it is structural. I have to admit, I have, over the last 10 years run over a few small sticks, but nothing heavy enough to leave a dent, or make anything louder that a slight "tick". Also, because of where the "crack" is, that"hit" would come at a very shallow angle, making for a very glancing blow. I just don't se evidence of that.

Now I am trying to decide if the FG guy is right and wants to grind out a half inch, replace with FG mate or tape, and then spray gel coat or paint the fix.

I don't much like the idea of paint over the patch. Seems that would show around the edges, and require a ton of gymnastics, (Taping, masking and ...?) to do on the trailer. I'm liking the sound of the thickened gel coat paste, spread like peanut butter. (I have much more experience with peanut butter :lol:

Harvey
SleepyC :moon

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Gel coat is sprayed into the mold, thus covers the entire polished surface of the mold. If the mold is not well prepped, the hull with stick, and potential damage to the mold, and boat...that rarely happens. The mat, next layer, does not lend to getting into this area, unless carefully laid. It is a problem getting the mat in, not the gel coat. No structural strength in gel coat...purely cosmetic. I had one large boat with no gel coat, only waxed resin on the last (or first) layer.
 
If you think it needs strength consider epoxy and colloidal silica. Its strong and is recommended for use below the waterline. Its a PIA to sand flush so apply sparingly. I used a fair amount of that and can vouch for its performance and longevity. Do wear mask when working with it. Its linked to lung cancers .......that is no joke.

Good Luck
 
After doing some sanding and grinding, I have found that for much of the "repair", sanding the apparent "crack" off, takes a bit of light sanding with 220 and the crack, which was just enough to catch a fingernail, is now gone. Makes me even more sure this is a defect in the gel coat surface. not a crack or scratch or anything structural.

The Gel Coat, in my case the burgundy or "Cabernet" color is only about 1/16 to 1/8 inch thick before I get into the white/grayish with some fiber in it.

Still working on it but it doesn't seem as bad as I was expecting, and no "fractures" to be found so far.

Harvey
SleepyC :moon

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