Polyester resin shrinkage. Is this a real concern?

[jimbunyard]

Forgot to add, for cleaning up cured, unwaxed laminations, either after the lamination is completed or between laminations, surform tools are quite handy, and fairly cheap---and cleanable for reuse.




With this one the half-round blade is much easier to use than the flat blade.

[wingssail]

Originally Posted by Cadence

I'm in the camp that believes your concern about shrinkage is unfounded. Yes there is some but unlikely enough to be an issue. The deck hull joint would be my concern.
Insure the old glass areas of your joint are sanded with lots of tooth.

I disagree. I have done repairs to my balsa cored deck a few times and originally I used polyester resin, polyester fillers, and normal fiberglass cloths and mats to effect the repairs.

Over the years some of these repaired areas shrank and left gaps between the new core material and the surrounding areas, in some cases the gaps were evident on the interior of the deck. Moisture has seeped through into the cored deck again.

Now I use epoxy resin and fillers and I have not had that problem.

[Redreuben]

As an ex laminator my advise is forget shrinkage not an issue. I’d use vinyl Ester resin and peel ply.
If vinyl ester feels like your overcapitalising then just use a good iso polyester.
I’m not familiar with your boat or it’s value but epoxy is probably lipstick on a pig.
Depends how long you see yourself with the boat if your happy to spend the money on epoxy then spend it.

[Wind River]

It looks like the polyester shrinkage issue is put to bed. It is a non issue but I can't stop reading and contemplating the advantages and disadvantages of each resin. I can see now why the average boat guy (like me) would just err on the side of epoxy. It seems it's only down side is the cost, and to the inexperienced DIY'er, that is a metric that is easy to understand and weigh into the project. If the cheaper resin fails due to an application shortcoming, the cost difference in the materials will be negligible compared to the repair. A prominent contributor here on this forum once said "The cost of boat repair is heavily weighted on the labor side, so always use the best materials available". Since the labor of the average DIY'er may not be as good as a pro, the epoxy may cover up any preparation or application failure. In my case the only concern I have is bond between the old glass and the new.

I had been convinced to use poly because that is what most of the pro's have been using. The longer this thread goes on, Vinylester seems to be preferred over polyester. The more I read about the details of each resin, the more I am leaning into the epoxy camp. It's easier to make that leap if you have convinced yourself vinylester is better than polyester for your particular project.

A little about my project to help set the stage. This is a Hudson Force 50 Center Cockpit boat. 51 feet on deck with a 14.5 foot beam. I am re-coring the entire surface of the deck and in addition to this I have peeled the hull due to an osmosis issue (peeled twice), so I will need to re-glass the bottom also. I will be using a lot of resin and really wanted epoxy below the water line, but was ok with poly..... until now.

I have already purchased 20 gallons (4 - 5 gallon pails) of polyester resin to get started on the decks back at the beginning of August 2018. Apparently Polyester resin has a shelf life of about 1 year, Vinylester about 3 months and Epoxy several years. Buying resin in small quantities is obviously more expensive than buying in bulk. If I were to buy a 55 gallon drum of epoxy, that should be enough for my entire project, decks and bottom at a substantial savings over "buy as I use" quantities of Vinylester. Epoxy may cost the same if the project is approached this way.

Buying 80 gallons of Poly in 5 gallon pails would be about $3200 plus freight. 55 gallon drum of U.S Composites 635 Thin Epoxy plus 27 gallons of hardener (80 gallon yield) is about $3200 shipped. Cost per gallon this way is the same for epoxy and polyester. If I could buy poly or vinylester resins in higher quantities I'm sure there would be substantial savings, but I simply can't use it all within its shelf life. I still work for a living and I don't know exactly when I will be able to finish this project, so I can't see investing in a large quantity of any resin other than epoxy.

So what is the downside of using epoxy for my boat given the cost argument is a non issue in this case?

1 - More expensive fairing compounds? I suppose if I have enough epoxy left over I could just mix West Systems 410 filler with it.

2 - Amine blush - U.S. Composites 635 Thin Resin does not blush.

3 - Sanding before continuing the layup

What else am I not considering?

[pcmm]

I definitely don't agree that the shelf life of epoxy is "indefinite" My experience as been that the shelf life of epoxy is around 1 year. after that it gets cloudy and I've found that the results become a bit less consistent. I also don't think that a good quality poly resin costs as much as you are quoting. In Canada I can get 5 gallon pails for $140 CAD. or about 30-40% less than the numbers you are listing. I agree that Epoxy is technically superior but both work well for their numbers But I would never purchase it in those quanitites if I thought It might sit around for more than 1 year. too much opportunity to get contaminated with moisture and the effects of temperature, etc.

[Wind River]

Originally Posted by pcmm

I definitely don't agree that the shelf life of epoxy is "indefinite" My experience as been that the shelf life of epoxy is around 1 year. after that it gets cloudy and I've found that the results become a bit less consistent. I also don't think that a good quality poly resin costs as much as you are quoting. In Canada I can get 5 gallon pails for $140 CAD. or about 30-40% less than the numbers you are listing. I agree that Epoxy is technically superior but both work well for their numbers But I would never purchase it in those quanitites if I thought It might sit around for more than 1 year. too much opportunity to get contaminated with moisture and the effects of temperature, etc.

I never suggested the shelf life of epoxy was "indefinite". From what I read the shelf life was about 3 years for the resin and 2 for the hardener and it will darken with age but that doesn't affect its properties. I'm pretty sure my epoxy work will be done within that time frame.

As far as the cost of the polyester, I paid $171.49 USD plus a $28.50 HazMat fee for each pail to be shipped but not including shipping. Maybe there are better deals out there I didn't find, but that seemed to be on par with most others I found. Maybe I am not looking in the right place? I used FiberglassSite.com

[pcmm]

Originally Posted by Wind River

I never suggested the shelf life of epoxy was "indefinite". From what I read the shelf life was about 3 years for the resin and 2 for the hardener and it will darken with age but that doesn't affect its properties. I'm pretty sure my epoxy work will be done within that time frame.

As far as the cost of the polyester, I paid $171.49 USD plus a $28.50 HazMat fee for each pail to be shipped but not including shipping. Maybe there are better deals out there I didn't find, but that seemed to be on par with most others I found. Maybe I am not looking in the right place? I used FiberglassSite.com

You should be able to get regular polyester for $125 a pail at uscomposites. vynilester is $179 . I like epoxy but with my experience with it I would not trust any opened containers that are a year old unless you've been able to keep them inside (climate controlled) 100% of the time. I've the same experience with WEST, EAST, System three, SeaHawk and EXP.

[TeddyDiver]

Originally Posted by wingssail

I disagree. I have done repairs to my balsa cored deck a few times and originally I used polyester resin, polyester fillers, and normal fiberglass cloths and mats to effect the repairs.

Over the years some of these repaired areas shrank and left gaps between the new core material and the surrounding areas, in some cases the gaps were evident on the interior of the deck. Moisture has seeped through into the cored deck again.

Now I use epoxy resin and fillers and I have not had that problem.

Bad bonding me thinks. In that epoxy is better.

[Cadence]

Originally Posted by TeddyDiver

Bad bonding me thinks. In that epoxy is better.

[TeddyDiver]

Originally Posted by Wind River

It looks like the polyester shrinkage issue is put to bed. It is a non issue but I can't stop reading and contemplating the advantages and disadvantages of each resin. I can see now why the average boat guy (like me) would just err on the side of epoxy. It seems it's only down side is the cost, and to the inexperienced DIY'er, that is a metric that is easy to understand and weigh into the project. If the cheaper resin fails due to an application shortcoming, the cost difference in the materials will be negligible compared to the repair. A prominent contributor here on this forum once said "The cost of boat repair is heavily weighted on the labor side, so always use the best materials available". Since the labor of the average DIY'er may not be as good as a pro, the epoxy may cover up any preparation or application failure. In my case the only concern I have is bond between the old glass and the new.

I had been convinced to use poly because that is what most of the pro's have been using. The longer this thread goes on, Vinylester seems to be preferred over polyester. The more I read about the details of each resin, the more I am leaning into the epoxy camp. It's easier to make that leap if you have convinced yourself vinylester is better than polyester for your particular project.

A little about my project to help set the stage. This is a Hudson Force 50 Center Cockpit boat. 51 feet on deck with a 14.5 foot beam. I am re-coring the entire surface of the deck and in addition to this I have peeled the hull due to an osmosis issue (peeled twice), so I will need to re-glass the bottom also. I will be using a lot of resin and really wanted epoxy below the water line, but was ok with poly..... until now.

I have already purchased 20 gallons (4 - 5 gallon pails) of polyester resin to get started on the decks back at the beginning of August 2018. Apparently Polyester resin has a shelf life of about 1 year, Vinylester about 3 months and Epoxy several years. Buying resin in small quantities is obviously more expensive than buying in bulk. If I were to buy a 55 gallon drum of epoxy, that should be enough for my entire project, decks and bottom at a substantial savings over "buy as I use" quantities of Vinylester. Epoxy may cost the same if the project is approached this way.

Buying 80 gallons of Poly in 5 gallon pails would be about $3200 plus freight. 55 gallon drum of U.S Composites 635 Thin Epoxy plus 27 gallons of hardener (80 gallon yield) is about $3200 shipped. Cost per gallon this way is the same for epoxy and polyester. If I could buy poly or vinylester resins in higher quantities I'm sure there would be substantial savings, but I simply can't use it all within its shelf life. I still work for a living and I don't know exactly when I will be able to finish this project, so I can't see investing in a large quantity of any resin other than epoxy.

So what is the downside of using epoxy for my boat given the cost argument is a non issue in this case?

1 - More expensive fairing compounds? I suppose if I have enough epoxy left over I could just mix West Systems 410 filler with it.

2 - Amine blush - U.S. Composites 635 Thin Resin does not blush.

3 - Sanding before continuing the layup

What else am I not considering?

For fairing buy micro ballons (adds volume and easier sanding, not for high stress) and silica ie cap-o-sil (prevents sagging) and mix with the epoxy. You can use also other "additives" like talcum (makes the compound harder) saw dust (volume and strength) micro fibers (strength) or pretty much anything but test first.
Cheaper..

[Cadence]

Originally Posted by TeddyDiver

For fairing buy micro ballons (adds volume and easier sanding, not for high stress) and silica ie cap-o-sil (prevents sagging) and mix with the epoxy. You can use also other "additives" like talcum (makes the compound harder) saw dust (volume and strength) micro fibers (strength) or pretty much anything but test first.
Cheaper..

Talc is a bitch to sand and fair. On the other side of the coin it won't mar micro balloons.

[44'cruisingcat]

Using polyester "because the pro's do" might sound good, but consider why the pro's use it...

Because it's cheap. Not because it's better.

Vinylester gives a considerable improvement in properties for not much more money. Why wouldn't the pro's use vinylester? Because every dollar more they spend on materials is less profit for them.

Also bear in mind that pro's may have considerably greater skills. So they can do a decent job with cheaper materials. Whereas for an amateur better materials may help compensate for less skill.

[TeddyDiver]

Originally Posted by pcmm

You should be able to get regular polyester for $125 a pail at uscomposites. vynilester is $179 . I like epoxy but with my experience with it I would not trust any opened containers that are a year old unless you've been able to keep them inside (climate controlled) 100% of the time. I've the same experience with WEST, EAST, System three, SeaHawk and EXP.

Dunno about warm climates but I'm now using the last batches of West drum bought 12 years ago stored in my celler in about +15C and still good.
Epoxy resin creates crystals when stored longer times which makes it "greyish" and eventually allmost solid. This starts on any surfaces on the storage vessel so you don't see it before it's developed quite much. However there's an easy cure, just warm up the epoxy up to about 50deg C and the chrystals melt away at once. The hardener darkening is due oxidation, that's nothing to worry about but keep the containers sealed as hardener has also some volatile stuff and loosing much is defineatly an issue.

Teddy

[Wind River]

Originally Posted by TeddyDiver

Bad bonding me thinks. In that epoxy is better.

This is my concern, bad bonding. I don't really trust the old laminate to not to be contaminated to some degree from moisture, seeing that it is a 36 year old polyester boat with blisters (below the water line).
If the old laminate was nice, clean, top quality laminate, I would not be as concerned with bonding, but my gut is saying it is not.

[Wind River]

Originally Posted by 44'cruisingcat

Also bear in mind that pro's may have considerably greater skills. So they can do a decent job with cheaper materials. Whereas for an amateur better materials may help compensate for less skill.

This was my thought also.