See through deck?

[Amart]

Not sure if this is normal or if I'm seeing things. Just got a fresh rain on a boat I just purchased and it appears that I can see the core through the gelcoat or is this something else?

[Franziska]

Originally Posted by Amart

Not sure if this is normal or if I'm seeing things. Just got a fresh rain on a boat I just purchased and it appears that I can see the core through the gelcoat or is this something else?

Try cleaning whit a mild abrasive on a not too prominently visible spot. Could be from a ripstop tarp which was on there long time.
Or is that the antiskid pattern and it's either worn off or someone spilled Diesel a while ago?

If you can't clean it off, it looks suspicious.
Core print through looks different normally, never seen it transparent like that.
Can't imagine that it would look like this on a production boat. Unless they did a really bad job when spraying gel coat.

Other thing that I could envision is that the previous owners cleaned the deck very hard and very often with abrasive cleaners so that the gel coat got very thin, if that's the case than you could perhaps really see through the top skin.

If it's "just" a thin gel coat, you can kiwigrip the deck. Provides enough UV protection and looks good while providing also great antislip.

In the worst case, drill a small hole on a dry day and feel if the shavings are wet. If that's the case you are in trouble. X my fingers that that's not the case.
If you use a core drill you could also verify the gel coat and upper skin thickness.

[Amart]

It was really the entire deck area, I kind of wonder if the gelcoat was worn away that much. The texture is like the molded diamond texture which still seems to be in great shape. The deck feels rock solid walking on every part of it, just seems odd.

[Chotu]

Is it print through then dirty feet leaving more dirt on the elevated foam or balsa block part of the print through? That would leave that pattern even on non-skid.

Has this boat been in the tropics?

[Calif.Ted]

Call or E-mail them pictures, it seems to be a honeycomb deck core showing thru but don't know if it's normal or not. Fiberglass can transmit quite a lot of sunlight if the angle is right.
https://privilegecatamaransamerica.c...arans-america/

[Amart]

It rained again and I was not able to see it at all now. The print was totally even across the non skid or not. Yes the boat was in the tropics for most of her life.

[Chotu]

Originally Posted by Amart

It rained again and I was not able to see it at all now. The print was totally even across the non skid or not. Yes the boat was in the tropics for most of her life.

OK. I am 99 or even 100% sure it’s what I said

So, what happened is while the boat was in the hot tropical sunshine, it developed something called print through. This is when the resin expands and contracts with heat, and it does so differently in places where the core is and in places where the core is not.

The squares you see are a type of core that is used for complex curves. Balsa comes in that type, and so does foam.

The space in between the blocks is just empty space. It ends up filled with resin, or with a core bedding compound. Either way, it reacts differently in the hot sun than the square parts.

So my theory is you have slightly higher areas where the square parts are, and lower areas where the lines in between the squares are.

As you walk around on it, you are getting the squares dirty, and the low parts in between them is staying clean. That’s why it disappeared when it rained.

This is nothing to worry about at all. It may not look amazing, but there is no structural problem here. Many boats develop print through. It is not unheard of at all. The hotter the tropical sunshine and temperatures, the softer the resin gets, and it ends up getting print through.

[Shrew]

I used to own a house that was stick framed with masonite siding. In certain weather conditions (the right combination of rain, temp. and sun angle), you could see the pattern of the wall studs in the siding. you were absolutely NOT seeing the studs through the masonite siding.

This could be similar. The comb pattern of the coring would have more resin in the crater floor and more material in the crater ridges. Each has different thermodynamic properties and may cause the moisture, dew, frost, whatever on the surface to behave differently. The difference reveals the pattern.

Just a thought.

[Chotu]

Originally Posted by Shrew

I used to own a house that was stick framed with masonite siding. In certain weather conditions (the right combination of rain, temp. and sun angle), you could see the pattern of the wall studs in the siding. you were absolutely NOT seeing the studs through the masonite siding.

This could be similar. The comb pattern of the coring would have more resin in the crater floor and more material in the crater ridges. Each has different thermodynamic properties and may cause the moisture, dew, frost, whatever on the surface to behave differently. The difference reveals the pattern.

Just a thought.

That’s also true. In certain sunlight conditions and temperature conditions, condensation might happen over the squares and not over the lines. Thanks to the different thermal properties of the core, versus solid resin.

[Manateeman]

Have the manatees seen this before? Answer...Yes.
Is this what boatbuilders call print through...answer ...No.
Is this a case of very thin gel coat? ...answer ...might be.
Is is “structurally “not important... answer...no.
If you bounce up and down on it...do you hear crunching?
Drill a few 1/8” holes. What comes out...damp, wet?
This is why we detest core.
There is no perfect test for the d...core.
Forget moisture meters, thermo meters...blah blah...blah meters.
The repair options have been beat to death on the forum.
If you jump up and down on it like tons of water and you are happy...then paint it over and move on.
The advantage of manatee pizza parties is that the term non destructive testing never applies.
Don’t worry. Be happy.
Captain Mark

[Amart]

I have walked around on a lot of it and jumped up and down and it seems to be totally rock solid with no crunching or creaking or anything.