Print through from foam edges?

All i can say Dennis, is that thousands of boats have been built with foam core and thin skins - mostly high performance multihulls. Farrier even coined a boat building method doing it -the vertical strip plank method. Then there is horizontal strip planking, or full size sheeting- like i use. All of these boats, when they're built properly, dont look like this a few years down the road. They stay fair, and these lines dont show up. Something has gone amiss to causes this to happen. What it is exactly, is anyones guess until the paint can be stripped off and a decent look underneath.

 

What do the others agreeing that its cosmetic only say to this?

 

Hard to imagine why it would only occur after several years, that I don't understand.

 

Thermal cycles in the tropics? The area of the prob is mainly located to the area shown my pic. The light is directly overhead so it shows it up a lot. I am guessing that this area is where it got the direct WA afternoon sun for a few years?

This corecell brochure even lists one of the benefits of it over other PVC foams as being more stable at high temp so that it does not suffer from print through. So it would appear that this prob is common enough for crosslinked PVC that it is listed as a drawback for this type of foam in this brochure.

http://www.fram.nl/faq/how/Corecell_in_Marine_Struct.pdf

 

The sides, in white, shouldn't get very hot. I keep getting back to what the laminate is on the outside skin, if it is super thin, it will be less effective in keeping the core in shape.

 

All manufacturers produce a high temp foam. Its used generally for high temp processing such as oven cure etc. The surface of a white coloured boat, gets nowhere near 100deg C, but that's about what I'd expect from a marketing blurb... In fact, most epoxy resins will begin to soften at ~ 80deg C, this is published as the resin HDT or Tg. If high temps above this level were present, most epoxy boats would be looking shagged aswell....

 

In the interests of peace of mind, Dennis should get a surveyor to look over it for him, if only to examine the particular issue that concerns him.

 

Yeah well I will get a surveyor for sure. However I would rather not waste $2000 for a full haul out survey if it the boat can be ruled out prior to that with my own research. The surveyor will charge the same rate if its in or out of the water and I also want a out of the water survey. When I figure out who I am using I will send him the pics first and he may be able to advise if I should go further.

The builder is gone for a month and cant answer any more questions.

 

Dennis; most likely it is just cosmetic, suggest you first go and tap the boat just with your finger nails. You will know the hollow sound if you find an area of delamination. More of a concern are hairline cracks so concentrate on these if there are any.
If this passes the tapping test get Geoff Cruse to do the survey for you.
Good luck

 

Thanks mate.

That was the name I was forgetting (Geoff Cruse). I will send him the pics first then go onto survey if the pics aren't an immediate killer. We done tapping at it sounded fine. I am going down on Sunday again with 44c possibly.

 

Tapping with, and dragging or scratching your fingernails along the surface should sound out air voids on a thin laminate.

When it comes to fairing those ripples, the majority of it will be filling. Be very careful of sanding those ridges when it comes to long boarding. If it's a very thin laminate, the ripples can only degrade the strength of it, and sanding into the laminate will exponentially weaken it in some ways. Thin laminates rely heavily on transferring loads smoothly, those ridges and hollows will somewhat disrupt that.

Is it painted or gel coated? Are those spider cracks in the upper blue stripe?

What are the other reasons for it being low priced?

It wouldn't hurt to put in a dingy or something and give a closer look underneath and all around.

 

Also look for docking bruises, I think there is one in the picture. The core gets crushed in this area and needs to be cut out, not hard to do when the boat gets sanded and repainted.

 

Id say that "docking" has caused all of the problems... Id say the lines are hard edges because of resin between foam sheets - agree with redreuban. As the boat gets pushed up on its fenders, it has compressed the foam around the hard spots and the lines have printed through... This probably explains why the lines are all down where the fenders sit and not so much up higher on the hull. You can see one bad spot, which looks like a hole thats been repaired... probably lost control in flukey winds and blown up against the corner of a marina pontoon which went through the hull judging by the height of it?

 

I know of a popular brand of west coast sport-fishers that show print through from the grid scored foam used, BUT structurally the boats are fine

 

Geoff saw the thread/pics thinks most probably it is not structural, so I will get a survey and he can tell me for sure. The issue is certainly not instantly damning. He says that that since VE shrinks overtime this will happen more with VE than epoxy.

The docking bruise theory sounds valid and shows why foam really needs that extra layer of glass even if a thinner one is good enough to handle global loads. Possibly I can add a layer of glass & epoxy in key areas if I fear the print through coming up again. There are quite few decent dents which will need re coring then! The other side has a nice one!

The lines in the blue edge are not cracks. There is no stress cracking anywhere in any laminate that I saw. The boat is painted not gel coated.