Repairing deck gellcoat stress cracks

[Hamish_ct]

I have a lot of experience with this. Its not a difficult job but takes time. Spider cracks are different than alligator cracks. Spider cracks need to be opened up. Use a roto zip,tool, dremmels are more for hobbiest, you need a professional tool. You only have to open it up enough so that the gelcoat can fillthe void. 4mm MAX.

For aligator cracks you have to sand down the whole area the gel coat over.

If you have any fiberglass or resin work to do do not use epoxy west systems. Gelcoat does not chemically adhere to epoxy. You have to use polyester resin. Your boat was built with polyester resin.

My advice is ..to strip the whole deck. work,out all the cracks then spray gelcoat the deck.

Prep work is the most important part of this. And you need a proper mask.

There are a lot of great books on diy boat work. Read up and ask a lot of questions.

In addition, spraying gelcoat outside is risky. It doesn't finish well. You should either build a cover over the whole boat or move the boat to an inside warehouse space.

The comment on using 5200 to fill the cracks will cause more problems and it will look,really bad.

Good luck. Its a worthwhilebjob to do and the results will make the boat look,new.

[BigBeakie]

I've used Magicezy on both stress cracks and deep gouges. The liquid Magicezy for thin stress cracks works well. It flows down into the thin cracks and bonds to the gel coat. You can run a fine sewing needle along the crack to open it up, ie V it before applying. With a slight buff after setting for 24 hrs, the cracks have disappeared.


Sent from my iPad using Cruisers Sailing Forum

[minaret]

Originally Posted by BigBeakie

I've used Magicezy on both stress cracks and deep gouges. The liquid Magicezy for thin stress cracks works well. It flows down into the thin cracks and bonds to the gel coat. You can run a fine sewing needle along the crack to open it up, ie V it before applying. With a slight buff after setting for 24 hrs, the cracks have disappeared.


Sent from my iPad using Cruisers Sailing Forum

Pictures, please?

[SVTatia]

Originally Posted by minaret

Not you! I thought I'd spent a bit of effort trying to convince folks to grind and glass stress fractures/spider cracks. It's the only way to get rid of them forever. It drives me crazy when people suggest a dremel and fill.

I know I know.... my apologies Minaret, but to strip the whole deck and cabin top and re-glass is totally out of scope for my project, else, I'll be spending piles of money on divorce lawyers. I'll save these dollars to re-do the painting in 3 or 4 or 5 years...
I am talking about gel coat crazing, I doubt that the OP has many stress cracks, these are localized whereas crazing is all over - without pictures I can safely assume they are the ubiquitous little (some are bigger) cracks and I believe these are mostly cosmetic. I very much agree that stress cracks need attention to its root cause and fixed permanently.
What I did on the cabin top looks ok, it was a lot of work and only half the job - I'll have to tackle the decks next - sides, fore and aft.

[SVTatia]

Originally Posted by bcboomer

Have you or anyone else here actually used this? If so, is it any good or just a good idea that doesn't really work?

There is another one...

Captain - Capt. Tolley's Creeping Crack Cure Sealer

[Canibul]

How do you know if a hull was laid up with epoxy or with polyester resin? I thought polyester was only used on low stress, no load cosmetic jobs like bondo filler for auto body repair. I have a hard time finding epoxy resin down here, and West systems is the only one stocked, by one store. Three other stores carry polyester fillers and resins. My life would be easier if I could use polyester on this old boat.

[Terra Nova]

Originally Posted by Canibul

How do you know if a hull was laid up with epoxy or with polyester resin?...

Nearly all fiberglass boats were built using polyester resin.

Originally Posted by Canibul

...I thought polyester was only used on low stress, no load cosmetic jobs like bondo filler for auto body repair...

No.

[jeepbluetj]

Originally Posted by Canibul

How do you know if a hull was laid up with epoxy or with polyester resin?

I'm sure the actual pro's will chime in with a real way to tell the difference. Me? As a rank amateur, I can tell by smell. When drilling, grinding, etc... Polyester smells like a surfboard shop. Epoxy doesn't. Dunno about vinylester as I've never dealt with it.

[minaret]

Originally Posted by jeepbluetj

I'm sure the actual pro's will chime in with a real way to tell the difference. Me? As a rank amateur, I can tell by smell. When drilling, grinding, etc... Polyester smells like a surfboard shop. Epoxy doesn't. Dunno about vinylester as I've never dealt with it.

Yep, smell and color.

[scuba0_1]

There's videos on YouTube for all the items that have been listed here

Sent from my SM-N910V using Cruisers Sailing Forum mobile app

[Impetuous too]

We sadly have experience of this. We spent four years restoring our Alajuela 38 which had been left on the hard in Texas for 18 years.

The reason we could buy the boat for only $10,000 US was the very severe cracking over the whole boats outside surface. It was noticably worse on the 'sunny side' from where she'd sat. We started out sanding well, cleaning well and filling well, using 40 grit sandpaper, working our way up with finer grits then filling with West system with colloidal filler. We then painted over a coat of epoxy then used Awlgrip system (including their fillers) to paint. We did the cabin top and deck the first year.

When we were back to it two years later we could already see that this wasn't going to be good enough long term. We could see the occasional tiny hairline crack. Long story short we removed ALL of the gelcoat from our topsides. As it had originally been layered up we think too thick this was not an easy thing to do. You can see on our blog though that it came out beautiful. Not a hint of cracks anywhere we removed the gelcoat and ground any cracks that had pulled in the fibreglass. There is definitely nothing wrong with our hull, only the gelcoat. The couple of places it had pulled just visible cracks into the top layer of fibreglass was where the gelcoat was the very thickest, around 1/4".

It's a lot of work but we plan to do our cabin top this way one day in the future. For now, we still get loads of complements but the cracks are slowly coming through where they were worst and the gelcoat is still there. Just an aside, we love our beautiful boat and we care about how she looks but it's really not necessary to fix cosmetic cracks in order to sail. We met many people under the age of 30 on some ropey looking but safe boats having all come across the same 3,500 miles from Panama to the Marquesas. We all had just as much fun there!

We spoke about how we worked on our gelcoat in our restoration pages on our blog a while ago if you'd like to see what we're talking about. I haven't updated it with the new cracks but if you want to know any more info we'd be pleased to share.

We wish you all the best whichever route you choose to take!

Ruth and Duncan

[Terra Nova]

Wow! 1/4" thick! Yeah, shrinkage would be fantastic.

Love the Alajuela 38. Very nearly began with a bare hull I'd located.

[Boatyarddog]

Originally Posted by mackrobertson

Hello fellow boaters,

I am re-fitting a 39 year old Allied Mistress and the deck has extensive stress cracking, probably due in part to the hot Texas sun.

I would be genuinely interested in anybody's experience with the repair of the cracks. I will have her re-painted with epoxy. Will that be enough to fill those cracks permanently, or will they reappear?

Please name any products and/or procedures that you or the yard has used on this problem.

Thanks kindly, for any and all experiences and advice,
Mack Robertson
Allied Mistress Hull #7
S/V Island Mistress

Use alkyd enamel paint, it's great for filling in those cracks checks, and impurrefections.
It's softer, but gets harder as time passes.
Epoxy is very brittle. And will crack again.
Interlux has lots of nice colors too.


Sent from my iPad SV Cloud Duster

[Terra Nova]

Originally Posted by Boatyarddog

...Epoxy is very brittle...

Epoxy is very flexible.

[Boatyarddog]

Originally Posted by Terra Nova

Epoxy is very flexible.

Without any glass it's brittle as hard candy, shatters when hit with a hammer.
Where is the flexible in that?

From the tensile data collected through this research, it can be concluded that the mechanical behavior of the epoxy systems tested changed as the test temperature approached and exceeded the Tg of the material. The maximum engineering stress of all epoxy systems ranged from 5-10 ksi below the Tg and the values slightly decreased within that range as the test temperature approached Tg. Much lower values of maximum engineering stress are seen for samples tested at the Tg. The modulus of the epoxy systems remained around 300 ksi for samples of all epoxy systems tested below the Tg, slightly decreased as the test temperature approached the Tg, and then drastically decreased as the samples were tested at the Tg of the system. Although some samples slipped at the end of the tensile test for one of the epoxy systems, clear ductile behavior was witnessed and higher elongation values compared to samples tested below the Tg were measured. Elongation comparisons were not made for samples tested above the Tg since the hold time was not the same as the other samples tested below and at the Tg of epoxy. However, it can be concluded that for most samples under the Tg, brittle failure occurs after the sample was exposed to the test temperature and the samples tested at and above the Tg of the system failed in a more ductile manner. Additionally, approximately the same percent conversion was present in all FTIR films that were exposed to the test temperatures within the same epoxy system. The mechanical behavior of the samples tested under these conditions showed the flexibility of the crosslinks in the epoxy systems through the mechanical properties studied. Additional testing should be done in order to determine an exact value for the upper use


Page 37 of 43, link. http://www.honors.ufl.edu/apps/Thesi.../Download/1070


Sent from my iPad SV Cloud Duster