Fiberglass Repair Option

This is typical of repair. Note that repair is made from the inside out if space permits. From Marine Composites

 

Thanks. I used to head a large FRP boat yard and we crank out a boat per week in series production. The yard is also Lloyd's approved facility at the time.

 

Should be. A patch sample is only needed and burning it in a gas stove or propane torch should make the laminate separate from each other. We do it all the time as we pull out core samples from each boat everytime. All we have to do is identify the type of fabric used.

 

rx

There was a long thread on this prior to this one, it went into more detail on the damage and other possible solutions.

He feels the laminate is thin and was a defect in manufacturing. He doesn't know how it failed and can't get any information from the manufacturer about the laminate schedule.

He doesn't know if this is the only thin area or if far more of the hull is this way. This is why further investigation is needed for a good answer as in how to fix it.

These repairs are coming out of his pocket and he can't find anyone that is willing to bid on cutting out the liner and doing it from the inside.

 

Here is the old thread.

Hull Damage Question https://www.boatdesign.net/threads/hull-damage-question.64732/


@bucketlist

In your opening post on the other thread you discussed delamination some 100" of it...can you expound on that? It is clouding things here because the repair area is much larger if so. And you can't outside repair by laying glass over delam! And 100" is almost certainly hitting structures!

Also, to avoid muddying the water, there is no core, correct? This was an early misunderstanding, right?

 

great advice . Thank you

 

The way a typical hull this size is made you won't have just one small section thin. It would need to be missing a laminate that would correspond with the dimensions of the fabric used in that section of the hull, say 50"X10' to 50"X20'.

The laminate may go from keel to gunnel or bow to stern. That's why I said more holes need to be drilled to determine just how much area is affected.

And when I indicated a large area needs to be built up, it needs to include all of the potentially thin laminate.

I've seen where an entirely new bottom has been glassed over the old one because it was thin or too damaged. I've done this to a couple of smaller boats.

 

No core , correct

 

What about the delam claim for 100"?

 

Wow, a long thread. I will have to wrap my head around it. Seems to me 3 different thread all pointing to the same problem.

In the thread about burnout test, even if bucketlist is able to get the lamination sequence and the UTS of the material, as Ad Hoc says, there is a lot of variables.

First would be the definition of the panel size, the designed pressure, and the guiding rules used. Class rule generally requires a safety factor of 3, ISO will allow up to 2. It is more of a forensic investigation to prove that the design is inadequate. Sorry to disappoint but consulting the forum cannot answer that.

We can only focus on the repair.

 

Most of this is one notch above my paygrade, but he has lost a couple years now of boat seasons and that sux.

It may be hard for him to get the old layup right. This is why an overlay is so attractive. But the delam he mentioned before needs to be explained. That 100" delam is bothering me.

 

The single skin hull laminate should be 6.5 to 7 mm (0.27") thick by LR or ISO standard with a nominal pressure of 33 kN/m2 of pressure. The keel width should be about 1.5x thicker with a width of about 10% of the chine width or about 340 mm wide.

Looking at the picture, seems the unsupported bottom was propped at the panel causing a complete shear (not a crack anymore), rotated and caused keel delamination. Probably during transport or handling.

Damage could be assessed by progressive shallow grinding to the point where there is evidence of delamination. A sharp chisel can be used to pry off individual laminate suspected of delamination.

The greater problem is the keel delamination.

 

Regardless of how it is repaired, I wouldn't leave port without the assurance of a foam-packed hull, in case of another unexpected fiasco.

 

Closer inspection of the photo shows stress cracking or delam at the yellow arrows.

It is suspicous because it is breaking along what appears to be a longitudinal.

The concern here is that this is a stringer and the internal tabbing is compromised.

If this is the case, then not reattaching it to the longitudinal is bad business.

Is this where you are referring to the 100" delam in the other thread?

It looks like rx has confirmed the layup is within an acceptable limit. The keel reinforcement is not clearly understood. So, the repair is the focus.

Let's agree the boat is unable as is. A no brainer. You need to determine if there is structure at the yellow arrows. A stringer. Remove a 4" coupon on the inside of the shear and reach inside. If you find a stringer there which I expect, I don't believe it wise to fix without opening the floor. When boats are constructed, these long internal structures are well bonded to the hull with glass tapes.

The four inch coupon can be burn tested and you can take pictures and see if the layup can be determined. Rumor has two layers of some type of fabric and the rest is coremat. The coupon you pull may include stringer tabbing (fyi).

Also, if this is under a poly tank; you are going to need to check the tank. If the hull sheared, the tank may have ruptured. If you hole saw the coupon, make sure the pilot is very short so as not to hole the tank.

 

I'm surprised that 6-7 mm of glass in the bottom, and regardless what quality of materials, would pass muster under any standards regime, for a boat that size, unless there is some complex webbing framework behind it, I would expect it to crack up sooner rather than later, in offshore use in worse than average conditions.