Polyester resin shrinkage. Is this a real concern?

[Cadence]

Originally Posted by Benz

While poly and vinyl-ester smell to high heaven, and yes, you should not drink the MEK, those resin systems are far less unhealthy than epoxy. Boatbuilders around here have been laminating with MEK-catalized resins from when they dropped out of high school to retirement with no "MEK sensititvity." There are also dozens, young and old, who have become epoxy sensitized from incautious use, and one at least I know was hospitalized and cannot now even be around grinding dust.

Point is, unless you squirt the MEK into your eye, there's not a lot of risk. Getting catalized poly/vinyl resin on your skin doesn't hurt you, and the only reason people wear respirators is to shut out the smell. Most don't. OSHA does not require respirators for use with MEK-cat resins, but they do for use with epoxies. Hmmm.

It only talks a few parts per million of MEK in your eye so catalyzed resin will do the damage. Wear goggles.

[44'cruisingcat]

Originally Posted by Benz

As far as osmosis which was just mentioned: the project in question is a deck. It does not sit 24-7 in water. Vinylester is way better for a hull that's gonna sit in the water, but given the price diff it may not be better enough to justify for a deck.
If budget was no issue, I'd always choose vinylester over poly for a big project. But if budget was no issue, I'd also always pay someone else to do it. Poverty or penury can make you look long and hard at other suitable options. In this case, polyester resin is a perfectly reasonable one.

As I've been saying, polyester gets used because it's cheaper.

If they were all the same price, how much polyester do you think they'd sell?

[TeddyDiver]

Originally Posted by Benz

While poly and vinyl-ester smell to high heaven, and yes, you should not drink the MEK, those resin systems are far less unhealthy than epoxy. Boatbuilders around here have been laminating with MEK-catalized resins from when they dropped out of high school to retirement with no "MEK sensititvity." There are also dozens, young and old, who have become epoxy sensitized from incautious use, and one at least I know was hospitalized and cannot now even be around grinding dust.

Point is, unless you squirt the MEK into your eye, there's not a lot of risk. Getting catalized poly/vinyl resin on your skin doesn't hurt you, and the only reason people wear respirators is to shut out the smell. Most don't. OSHA does not require respirators for use with MEK-cat resins, but they do for use with epoxies. Hmmm.

Read it.. https://www.tetconnect.com/images/st...POR002_SDS.pdf
Thou not my concern what you use but don't lie to others. In commercial production it monitored the safety limits shouldn't be exceeded and the working space ventilation meets the specs. However that is not the case of DIY projects. How many have adequate ventilation in their backyard tent. If you have change to works open air that's different but again how many do?

Teddy

[Wind River]

Good morning.
Sorry I have been absent from this discussion for a day or two.

After great consideration of all the points brought up here about the pros and cons of the different resins, I have decided to use vinyl ester for my project. Since I will be re-glassing the hull at some point to eliminate the osmosis blister problem I had, I thought it would be good to keep the material consistent throughout to entire project and polyester was not an option for the hull.

I had tunnel vision with the bonding issue. I never once thought the bond of polyester to the Coosa board was insufficient, I concentrated only on the bond of the new fiberglass to the old glass as if the bonding to the new core has no effect on the stress this connection would see. Obviously (now) the entire connection of the core to the lower skin and the new glass over the new core all add to the stiffness and strength of the deck and not taking that into account had me thinking that all the deck stress was going to be taken by the 2.5” connection of the old glass to the new . It wasn’t until these two comments sunk that I had realized this.

Benz said - “As for adhesion, dear me, look at all the surface area you're bonding to! Think of all the molecules holding hands along that long, long stretch of surface. It's plenty.”

Jimbunyard - “Perhaps a more esoteric reasoning needs also to be introduced. You've already used Corebond to secure the Coosa panels to the inner skin. Corebond is polyester resin mixed with, as far as I can determine given the weight per gallon, glass beads. Since the real strength of the deck is determined by the separation of the inner and outer skins and their bond to the separating core, it seems a little odd to be questioning bond strength of poly at this point, given that (very roughly) at least half of your deck's strength already relies on just that bond. To venture even further into esoterica (and doubt), does the differing strengths of the two resins contribute to or detract from the overall structure's strength?”

It really shows the value of discussion of the broader topic at hand than just one piece of the puzzle.

I contacted two different suppliers for vinyl ester, Composites One and U.S. Composites. I would be able to purchase vinyl ester from U.S Composites for $179 for a 5 gallon pail. Composites One only sold it in the 55 gallon drum and for comparison that would be about $143 for 5 gallons. Composites One has a warehouse local to me and will deliver for about $12.

On the U.S. Composites website they give and approximation of the amount of resin it takes to wet out different types of fiberglass and they say that for Chop Strand Mat the ratio is about 2 lbs. of resin to 1 lb. of mat. For 1708 Biax cloth the ratio is about 1.5 lbs. of resin to 1 lb of cloth.

My side decks and foredeck cover a little over 18 square yards. The layup will consist of 3 layers of 1.5 oz. CSM mat and 5 layers of 1708 for a total fabric weight per square yard of 10.34 lbs of fabric per square yard of layup. With the above ratios, that comes out to 16.78 lbs. of resin per square yard. At approximately 9 lbs per gallon, that is almost 34 gallons of resin.


I still have a 11 square yard aft deck and a 12 square yard cabin top to recore and re-glass, so I might have to recore one of those before purchasing the vinyl ester so I don't waste any of the drum. Based on the above resin ratios I could do the side deck, foredeck and aft deck with one drum and one 5 gallon pail but that doesn't take into account any waste.

Does this sound about right? Would you base this job off the above ratios of glass to resin?

[Wind River]

Originally Posted by TeddyDiver

Read it.. https://www.tetconnect.com/images/st...POR002_SDS.pdf
Thou not my concern what you use but don't lie to others. In commercial production it monitored the safety limits shouldn't be exceeded and the working space ventilation meets the specs. However that is not the case of DIY projects. How many have adequate ventilation in their backyard tent. If you have change to works open air that's different but again how many do?

Teddy

I have my tent attached to a small building that has a 10,000 cfm exhaust fan in it. At the other end of the tent is a zip up window. Very good ventilation in this one.

[TeddyDiver]

Originally Posted by Wind River

Good morning.
Sorry I have been absent from this discussion for a day or two.

After great consideration of all the points brought up here about the pros and cons of the different resins, I have decided to use vinyl ester for my project. Since I will be re-glassing the hull at some point to eliminate the osmosis blister problem I had, I thought it would be good to keep the material consistent throughout to entire project and polyester was not an option for the hull.

I had tunnel vision with the bonding issue. I never once thought the bond of polyester to the Coosa board was insufficient, I concentrated only on the bond of the new fiberglass to the old glass as if the bonding to the new core has no effect on the stress this connection would see. Obviously (now) the entire connection of the core to the lower skin and the new glass over the new core all add to the stiffness and strength of the deck and not taking that into account had me thinking that all the deck stress was going to be taken by the 2.5” connection of the old glass to the new . It wasn’t until these two comments sunk that I had realized this.

Benz said - “As for adhesion, dear me, look at all the surface area you're bonding to! Think of all the molecules holding hands along that long, long stretch of surface. It's plenty.”

Jimbunyard - “Perhaps a more esoteric reasoning needs also to be introduced. You've already used Corebond to secure the Coosa panels to the inner skin. Corebond is polyester resin mixed with, as far as I can determine given the weight per gallon, glass beads. Since the real strength of the deck is determined by the separation of the inner and outer skins and their bond to the separating core, it seems a little odd to be questioning bond strength of poly at this point, given that (very roughly) at least half of your deck's strength already relies on just that bond. To venture even further into esoterica (and doubt), does the differing strengths of the two resins contribute to or detract from the overall structure's strength?”

It really shows the value of discussion of the broader topic at hand than just one piece of the puzzle.

I contacted two different suppliers for vinyl ester, Composites One and U.S. Composites. I would be able to purchase vinyl ester from U.S Composites for $179 for a 5 gallon pail. Composites One only sold it in the 55 gallon drum and for comparison that would be about $143 for 5 gallons. Composites One has a warehouse local to me and will deliver for about $12.

On the U.S. Composites website they give and approximation of the amount of resin it takes to wet out different types of fiberglass and they say that for Chop Strand Mat the ratio is about 2 lbs. of resin to 1 lb. of mat. For 1708 Biax cloth the ratio is about 1.5 lbs. of resin to 1 lb of cloth.

My side decks and foredeck cover a little over 18 square yards. The layup will consist of 3 layers of 1.5 oz. CSM mat and 5 layers of 1708 for a total fabric weight per square yard of 10.34 lbs of fabric per square yard of layup. With the above ratios, that comes out to 16.78 lbs. of resin per square yard. At approximately 9 lbs per gallon, that is almost 34 gallons of resin.


I still have a 11 square yard aft deck and a 12 square yard cabin top to recore and re-glass, so I might have to recore one of those before purchasing the vinyl ester so I don't waste any of the drum. Based on the above resin ratios I could do the side deck, foredeck and aft deck with one drum and one 5 gallon pail but that doesn't take into account any waste.

Does this sound about right? Would you base this job off the above ratios of glass to resin?

That's a thick layup, way too thick and heavy me thinks. How thick was the core? And the CSM makes me wonder, as I'd never use on corecell anyway..
The shed and ventilation looks good

[Wind River]

My original core was 15mm and 18mm plywood. I replaced it with 5/8" Coosa and figured an extra layer of cloth would make up the difference in thickness.
The original deck skins were mostly 1/4" thick. Some areas more some less. I tested the layup and 6 layers of 1708 was 1/4". I wanted to add two layers of chop strand on the top in case I needed to grind some down to get fair and not hit the 1708 biax. I read it's best to start with a layer of CSM also even though there is some on the 1708.

[Benz]

You're on the right track, Wind River. It is good to start with a layer of CSM over the core. BTW, it's common to do a "skin coat,"--a single layer of CSM, well rolled down and bubble-popped (I hope you have some bubble poppers), that you allow to tack off before starting on the other layers. Then if you do your next plies mat-down, and finish with CSM, you'll have a nice sandwich.
Don't feel like you have to do all six layers in one go--you can take several days if you wish, as long as you knock down the little sticky-ups on the hardened surface before starting again. Good luck.

[Benz]

Originally Posted by TeddyDiver

Read it.. https://www.tetconnect.com/images/st...POR002_SDS.pdf
Thou not my concern what you use but don't lie to others. In commercial production it monitored the safety limits shouldn't be exceeded and the working space ventilation meets the specs. However that is not the case of DIY projects. How many have adequate ventilation in their backyard tent. If you have change to works open air that's different but again how many do?

Teddy

This is not an OSHA document. It seems to be from Lancashire. As I said, respirators not OSHA required for poly and vinyl esters, but boy are they ever for epoxy!

[Wind River]

Originally Posted by Benz

You're on the right track, Wind River. It is good to start with a layer of CSM over the core. BTW, it's common to do a "skin coat,"--a single layer of CSM, well rolled down and bubble-popped (I hope you have some bubble poppers), that you allow to tack off before starting on the other layers. Then if you do your next plies mat-down, and finish with CSM, you'll have a nice sandwich.
Don't feel like you have to do all six layers in one go--you can take several days if you wish, as long as you knock down the little sticky-ups on the hardened surface before starting again. Good luck.

I have not heard of this bubble popping. Is it exactly what it sounds like?

What is a bubble popper?

Is the 1st CSM layer supposed to go just on the core or all the way up the scarf of the original glass?

There is a small step up at the scarc. I was going to build up to with the CSM and one layer on 1708 before going onto the scarf.

[TeddyDiver]

Originally Posted by Wind River

I have not heard of this bubble popping. Is it exactly what it sounds like?

What is a bubble popper?

Is the 1st CSM layer supposed to go just on the core or all the way up the scarf of the original glass?

It's a roller either a metallic one with grooves or with plastic "brush" to force the air bubbles from CSM. With fabrics you can squeeze with spackle knife or similar to do the same and at the same time get the excess resin of to dryer places. The result is much better resin/gf ratio on fabrics compared to CFM, as you see also in the US Composite website, however IMO their approximate for Biax is way too much. I have no trouble to squeeze Biaxial laminate to 1/1 resin GF ratio. Thou laminating the CSM under increases that some. Some resin goes also to wet out the core. Structurally the CSM contributes are minimal just helps some with the bonding to the core.

[TeddyDiver]

Originally Posted by Wind River

There is a small step up at the scarc. I was going to build up to with the CSM and one layer on 1708 before going onto the scarf.

No as the CFM would be penetrating the layup, just rip it a bit short before the scarf not cutting.

If the new core is a bit thinner than the old one grind/sand of a bit more of the scarf for the new layup to go bit over the old core and to get the transition smooth. If it's allready there you can either sand the cores to be even or use filler to do the same or both..

[44'cruisingcat]

Originally Posted by Wind River

I have not heard of this bubble popping. Is it exactly what it sounds like?

What is a bubble popper?

Generally called consolidating rollers. Often its a short length of threaded bar, maybe 12mm diameter, drilled end to end, and fitted on a handle like a small paint roller.

[Benz]

^^what they said about bubble poppers. They're very handy tools to get the tiny air bubbles out of the laminate, and to push it down without dragging around the strands of CSM, as a squeegee would do (as Teddy pointed out, you can squeegee over biax. I still prefer a bubble popper). Bubble popping is the first step in many a dropout's boat building career, and though I skipped dropping out of high school, I've still spent days on end bubble popping.
I would take the skin coat all over the entire surface to be laminated. When the skin coat is good and wet and pressed down, you'll know that there's no dry spots in the core or bonding surface (they're going to take a good deal of resin to get wet). The skin coat ensures good adhesion between the original surface and the rest of the laminate. It's like a hot-coat, but with substance to it.
Oh, you'll need a small (5/8" diameter, 2" long) bubble popper for details, and a longer one (maybe 6") for the large surfaces. Press down hard enough to consolidate the laminate, but not so hard that you disarrange the surface. If you keep a bucket of acetone handy, you just stick the poppers and brushes and squeegees in there whenever they're not in use--keeps them from gunking up.
This is going to be fun!

[Redreuben]

Well given I’m just a high school dropout, I’ll leave you educated experts to your calling.