Fiberglass Repair Question

[marksa1458]

1975 Century Arabian. Previous owner smashed the side somehow:





My plan is to lay a layer of 8 oz cloth on the inside several inches beyond the damaged area and then grind out all the cracks and fill/ fair with an epoxy fairing compound. Ultimately the whole boat will be painted. Is this the best way to tackle this problem?

 

[Woodonglass]

Re: Fiberglass Repair Question

Based on what I'm seeing in the picture, I personally don't think one layer of 8oz of glass on the inside will be enough to repair this damage. Others may come along and have different opinions. This appears to have been a significant impact. How much Flex is there in the side? What is the Actual measurement of the damage?

 

[Decker83]

Re: Fiberglass Repair Question

:welcome: marksa1458.. From looking at the pics you have some pretty heavy damage..

The cap has a nasty crack, and it looks like the hull will have some bad shattered glass behind the gel coat..

I am no expert but IMHO I don't think you will get by using just 8oz cloth..

You will need to look inside and grind back all the bad glass and replace with some CSM and 1708 biaxial to start with..

You can then grind back the outside of the hull and make the needed repairs..

There are a lot of great gentlemen here that know way more than me that can help you with this repair in a lot more detail..

Have a great week..

 

[marksa1458]

Re: Fiberglass Repair Question

Thanks for the replies. The construction of this boat is a layer of fiberglass/gel coat, layer of foam and another layer of fiberglass. There is a little give to the damaged area, but it's not soft. I can measure when I get back into the garage. I will open up the inside and post some more pics. Thanks.

 

[GT1000000]

Re: Fiberglass Repair Question

That is a fairly involved repair...
I don't have the time to go thru all the steps, right now...
But I would start by removing any bright work, the rub rail, the grab rail, emblem and quite possibly the windshield, and gaining access to the interior...
Take lots of good pictures of the insides and post them...
We have several excellent glass guys here who will assess the damage as best as possible and guide you to a successful repair...

 

[marksa1458]

Re: Fiberglass Repair Question

Additional pics of the inside:

There is 3 layers to the hull. The outside glass, foam core and a thin inside layer of glass



The foam core



The inside glass



The inside glass and foam removed (the blue tape is the center of the damage)



The only evidence of damage on the inside are these stress marks (difficult to see):



The area has "slightly" more give than the rest of the hull.

Thanks for your input.

 

[GT1000000]

Re: Fiberglass Repair Question

The following is a somewhat simplified, but accurate description of the what you will need to do to effect a solid repair...
After you clear away the rub rail and any other bright work or hardware in the way...start grinding away all the bad glass...
Go as far as necessary to get to good, uncracked, solid glass, approximately to where the orange ovals are...
Create a shallow dished area with the green ovals being the deepest areas and the orange areas being pretty much flush with the surface...if possible, try to get to the inner most layer of glass, without breaking through... but if you do, no biggie...
If the inner most layers survives, then begin laying in progressively larger pieces of CSM [1.5oz.] and 1708 biaxial, until you reach the desired hull/cap thickness...
Depending on whether you are going to paint or gel coat, the final height of the glass should be level with the surrounding area if painting, or just shy, by about the thickness of a penny for gel coat...
If you happen to break through the inner layer, just create a dam out of some wood or cardboard covered with wax paper and proceed as above...
If done correctly, that should be a solid enough repair...
If you want to add additional strength, you could grind a slightly dished area on the inner skin and apply a couple of extra layers of CSM and 1708 in the same manner as the outside...
Take your time and make sure your laminations are as bubble free as possible...
Good luck and be sure to keep us posted on your progress, plus if you have any additional questions, fire away...

Here are a couple of sketches...

Where to grind...



Applying laminations...

 

[marksa1458]

Re: Fiberglass Repair Question

Thanks GT - thats how I will go.

For the inside though, can I simply apply a layer of heavy cloth over the area, I won't need to fair it out and foam will go back in over the repair and a thinner layer of glass over the foam.

It will take me a few weeks, but I will post my progress.

 

[1Zorro1]

Re: Fiberglass Repair Question

GT is on the money IMO. On Youtube you will find similar repair tutorials. Look for the shop sponsored ones.

 

[marksa1458]

Re: Fiberglass Repair Question

Follow up - on all my projects to date, I have used epoxy and cloth and have never used polyester. Would it be better to use polyester for this repair.

 

[Decker83]

Re: Fiberglass Repair Question

If you use epoxy on the outside of the hull, gel coat will not adhere to it. If you are going to gel coat Don't use epoxy..

I would definitely apply the same to the inside of the hull as describe above.

If you use a heavy cloth on the inside, be sure to use CSM (1.5) and the cloth in one wet layup.. The cloth by itself will not bond well without the CSM..

I would not spend the extra money on epoxy.. The hull is made of polyester..

Have a great weekend..

 

[jbcurt00]

Re: Fiberglass Repair Question

Depends, if you plan to re-PAINT the hull after the repair, you can use either. If you want to try Gelcoating the repair, it HAS to be a polyester repair.

Epoxy will take longer to cure at each step of the layup, and cost more then polyester resin. Polyester resin REQUIRES the use of a respirator, but cures quickly, even if you do multiple layups all at once.

I'd wear a respirator to do epoxy too if working w/out sufficient ventilation.

 

[marksa1458]

Re: Fiberglass Repair Question

Got the gel coat off.



The cracks are more visible fron this side. Do they need to be cut out?

 

[GT1000000]

Re: Fiberglass Repair Question

If you plan to add some new layers to the inside, you can leave the cracks there until you build up the outside, then grind away the remaining cracks from the inside and build up the laminations...
Otherwise, I personally would remove all signs of cracking, as that glass is compromised and no longer structurally sound...
From the looks of the picture posted, you might be better off doing it the first way, build up the outside, then remove the bad stuff from the inside using the same technique as the outer skin, grind out to a dish and rebuild...
That way you will end up with the strongest possible repair...

 

[Mud Puppy]

Re: Fiberglass Repair Question

Got the gel coat off.

The cracks are more visible from this side. Do they need to be cut out?

In Aircraft, if it were Aluminum, you would "Stop Drill" to prevent it from cracking further, if it were Composite, you would "V Notch" grind well past the busted fibers of the damage.

You need to work some resin "soak it up" down into the bottom of the crack to make those fibers part of the hull again and not part of the crack if that makes any sense. Resin with some fiberglass fibers mixed in will help bond that area back. You can buy chopped fibers, or if you don't need many, you can make them yourself. They aren't very expensive either way. Work the resin mix down into the notch. Leave it a tad high and after it's dry, you can flatten it back out on the outside with slight grinding or sanding. It won't matter quite as much on the inside, but the basic idea is to push the resin mix through to the inside and have it "mushroom" out. This, when done correctly, not only bonds to the hull, but by attaching to the inside surface, forms a "plug" that will not come out or crack around. "Vee'd" from both sides would be ideal, i.e. "outside of hull >< inside of hull".

I would only cut out the area if the damage was in the shape of a "C" compromising 75% (or more) of a circle or an oval. The area in the opening of the "C" is still attached, so the only discontinuity is the semi-circle of the "C".

The "Step Backs" that GT1M spoke of is where the real strength of the repair will come into play. Make sure to clean the area before each application of resin (and glass/ resin) with acetone and make sure that it is well evaporated before you smear anything into the damaged area or additional layers if you sand.

When the outside is done, it should be near flat, to avoid all of the sanding/ blocking, each layer flat into its own step. Use a Bondo spreader and you're in tall cotton.

 

[marksa1458]

Re: Fiberglass Repair Question

Update.

Ground out the gel and laid a layer of thickened epoxy and a layer of biaxial cloth(1708)



I did it this way to retain the shape of the hull. I then ground out all the cracked glass:



Now that the bad glass is gone, I plan to epoxy in 4 layers of the 1708 to build back the thickness in the different ground down regions and then place two more layers over the whole area extending into the undamaged area.

 

[GT1000000]

Re: Fiberglass Repair Question

Looks real good!
Since you used epoxy for the repair, I will assume you are going to paint?
Should be better than new when done...

 

[marksa1458]

Re: Fiberglass Repair Question

Thanks

Yup going to paint. While the gel is ok, it's brown.....

 

[Decker83]

Re: Fiberglass Repair Question

Looks great from here in Texas..

Sounds like a good plan..

Have a great hump day..eace: