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Old 04-11-2012, 07:35   #1
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Light through the hull

I'm new to this forum and am looking at a 30' trailer sailboat build in 1974. There are small specks where light shines through the hull on the inside, though they are not actual holes. Also, larger areas where the fiber glass is translucent on the inside. This is all above the water line. The hull is woven glass below the water line. I have not found any actual holes on the outside and in fact no blistering. It defiantly needs paint though. How bad is this? I would only use it for lakes and maybe the coast some day.
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Old 04-11-2012, 07:57   #2
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Re: Light through the hull

Hello, In my experince, the translucent areas are most likely repairs if they are golfball size or larger. Perhaps from filling in a thru-hull or a minor impact. If there are alot of nickel or dime size below the waterline it could be repaired blisters. If they are much smaller "pea" size. I would think it is due to uneven pigment of gelcoat. To inspect, i would use the handle of a screw driver to "sound" the hull. you should hear a crisp solid sound. a dull or hollow sound could mean problems. What is the year and make of the boat? I wouldn't write it off because of translucent areas.
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Old 04-11-2012, 08:15   #3
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Re: Light through the hull

Light through the hull on a 30 ft boat is not uncommon on racers. If you know who made the boat, maybe we could comment on their reputation.
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Old 04-11-2012, 08:37   #4
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Re: Light through the hull

Randal,

My Olson 30 has numerous areas (like the entire cockpit) that was translucent. The boat was designed like that, and is well known as one of the most successful ocean racers of its day, and is still an extremely popular solo distance racer. As Don mentioned it isn't that uncommon in areas where you don't need much strength.
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Old 04-11-2012, 09:19   #5
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Re: Light through the hull

Fiberglass is translucent! Small flickers of light are the result of refraction within the glass. It happens on all boats and indicates only that the gelcoat layer is porous.
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Old 04-11-2012, 09:21   #6
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Re: Light through the hull

any uncored boat will show lots of light through the glass unless it's painted or gelled on the inside. "Fiber optics"
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Old 04-11-2012, 09:32   #7
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Re: Light through the hull

Polyester resin (epoxy as well) and fiberglass is opaque. It is where there is gelcoat that you are not seeing light penetrating the fiberglass. No worries, light is not a positive indicator that the hull or deck is too thin.
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Old 04-11-2012, 10:35   #8
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Re: Light through the hull

Most boat manufacturers spray on an opaqueing layer, probably gel coat. Since fiberglass is translucent and sometimes transparent, it lets light through. Makes people real nervous to see through the hull of their boat which is why builders add the non light transmitting layer.

Bought a new boat that had a totally screwed layup on one half the hull. After first long sail, bulkheads began to print through and hull got very wavy. Took plugs out of the hull to determine thickness of layup. Areas where light was streaming through turned out to be thickest. Other areas that looked solid and opaque turned out to be only a single layer of light cloth about an 1/8th of an inch thick.
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Old 04-11-2012, 11:24   #9
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Quote:
Originally Posted by RANDALLK
I'm new to this forum and am looking at a 30' trailer sailboat build in 1974. There are small specks where light shines through the hull on the inside, though they are not actual holes. Also, larger areas where the fiber glass is translucent on the inside. This is all above the water line. The hull is woven glass below the water line. I have not found any actual holes on the outside and in fact no blistering. It defiantly needs paint though. How bad is this? I would only use it for lakes and maybe the coast some day.
You say that it's a trailer sailor built in 1974. Some of the less expensive boats of that era were built up with chop guns to lay up the fiberglass, and those hulls are prone to a phenomenon called "oil canning," where the hull flexes while going to weather in rough seas. You might want to do a bit of research on the particular hull that you're looking at.

Many hulls from the early 70's were overbuilt, with more layers of fiberglass than necessary by modern standards. If that's the sort of boat you're looking at, you'll be fine. But if you're looking at a hull that will oil can, walk away. Too many good hulls out there to buy a bad one.
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Old 04-11-2012, 11:43   #10
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Re: Light through the hull

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Originally Posted by S/V Illusion View Post
Fiberglass is translucent! Small flickers of light are the result of refraction within the glass. It happens on all boats and indicates only that the gelcoat layer is porous.
Well maybe...but it could also be a sign of Polyester Mites, no?
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Old 04-11-2012, 12:20   #11
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Re: Light through the hull

OK, light comes from the sun and so do UV rays which overtime breaks down fiberglass. I apply a black paint, resin or gelcoat before the final color. You cannot see light thru black...Just sayin. Plastic painted black finish coated with white will last (indefinately) forever. I repeat, ergo, black plastic if exposed to the sun will melt, then break down. White plastic will just break down. Rotting hulls sit in many backyards.
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Old 04-11-2012, 12:33   #12
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Re: Light through the hull

Quote:
Originally Posted by Cheechako View Post
any uncored boat will show lots of light through the glass unless it's painted or gelled on the inside. "Fiber optics"

Exactly. It's nothing to worry about. I see it on almost all boats. Generally when the gel-coat is not real thick (which can be an asset) light will be transmitted though as you say via fiber optics. Last week I used this as an advantage to place a new thru-hull for the basin in my head. At night, I shined a light against the inside the hull, went outside and could see a faint light shining through and drilled in. The hull was over 5/8" there. So you see, its not a thickness issue.
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Old 04-11-2012, 12:39   #13
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Re: Light through the hull

We looked at an Alberg 30 this summer and noticed the same over the vee birth area. Broker told us pretty much the same as been posted here - just light reflecting though the fibreglass. They didn't appear to be leaks and the boat had been very well maintained otherwise so we weren't too worried. Alas, she wasn't the boat for us.
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Old 04-11-2012, 12:40   #14
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Re: Light through the hull

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Originally Posted by svHyLyte View Post
Well maybe...but it could also be a sign of Polyester Mites, no?
maybe teredo worms
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Old 04-11-2012, 22:31   #15
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Re: Light through the hull

Light throught the glass !! just remember it goes both ways so if you getting undressed inside the boat and the lights on some one next door could be having a pep show veiw of what you doing .so if you have girls on board turn off the lights or you could draw a crowd !!
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