# Why is nobody using epoxy?



## Sam K (Apr 24, 2020)

So I’m starting to think about the specifics of mass production on the prototype boat I’ve documented in the bragging spot section. I come from an aerospace background, and the standard for resins and construction is epoxy infusion resin. I know lots of companies are doing infusion with vinylester and polyester, but everyone who is anyone in the skiff industry seems to run away from epoxy. I’ve figured out already that the cost of production difference is minimal. There are ways around the gel coat issue by using “epoxy gel coats”, really just epoxy with fillers and pigments, or by spraying awlgrip after the parts come out of the mold. On paper, epoxy is far clear of the other resins in many different ways. Some big power boat companies like Scout, a lot of yacht and sailboat companies, and premium canoe folks have made the switch. I’ve had a great experience building my first two boats and my prototype out of hand laminating epoxies. 
So, I can only assume I’m missing something as to why the skiff industry hasn’t followed. I’d love to hear what folks with more hands on experience than me, especially in infusion and marine mass production, have to say.


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## m32825 (Jun 29, 2018)

Polyester resin = new boat smell. 🙂


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## trekker (Sep 19, 2015)

Drake Brothers build a badass epoxy skiff.


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## K3anderson (Jan 23, 2013)

Its more $$$$ for epoxy. Its better in every way.


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## Sam K (Apr 24, 2020)

K3anderson said:


> Its more $$$$ for epoxy. Its better in every way.


I calculated to build my boat it would only cost about 10% more in materials to build with epoxy vs poly. And materials aren’t even the majority of the cost of production. It pays for itself in that you can use less resin and less glass to achieve the same or better strength. Also would result in weight savings of 75 lbs conservatively.


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## Sam K (Apr 24, 2020)

trekker said:


> Drake Brothers build a badass epoxy skiff.


I knew about chittum and that a lot of companies do epoxy in some cases, especially with carbon, but didn’t know about drake. They make some dang beautiful boats but I’m trying to offer a much more affordable option.


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## Sam K (Apr 24, 2020)

m32825 said:


> Polyester resin = new boat smell. 🙂


Honestly a small part of my desire to use epoxy is I absolutely hate poly smell haha


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## K3anderson (Jan 23, 2013)

Sam K said:


> I calculated to build my boat it would only cost about 10% more in materials to build with epoxy vs poly. And materials aren’t even the majority of the cost of production. It pays for itself in that you can use less resin and less glass to achieve the same or better strength. Also would result in weight savings of 75 lbs conservatively.


I built a skiff 100% epoxy. It's not used because its way more expensive.


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## Half Shell (Jul 19, 2016)

I would imagine the decision being epoxy vs vinylester, not epoxy vs polyester.


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## Sam K (Apr 24, 2020)

Half Shell said:


> I would imagine the decision being epoxy vs vinylester, not epoxy vs polyester.


Yeah that’s where I’m at, but the vinylester shortage right now is making me look closer at epoxy. Also, I like other aspects of it like significantly increased shelf life


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## permitchaser (Aug 26, 2013)

Your building the boat so your in charge. Build it the way you think it would sell better, then let the market decide. Can't wait to see it and the price


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## lemaymiami (Feb 9, 2007)

One other thing to keep in mind about “new” or just plain different technology. There’s always a learning curve and I can well understand a manufacturer wanting to stick with what they know will work as opposed to what they might have to make a mistake with while learning to use it properly…


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## Silent Drifter (Apr 29, 2021)

I thought this was the reason 🤔

Chopped strand mat is also known as fiberglass mat. It is made up of short strands of fibers that are randomly oriented and held together with a resin binder. The resin binder needs styrene to dissolve properly. This makes it incompatible with epoxy resin


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## Fishtex (May 10, 2014)

I’ve got to agree with Capt Bob here. And I too have worked in the aerospace composites world and poly or vinyl resins are pretty much unheard of unless it’s a situation with legacy military aircraft and the spec dictates.

Anything new is all carbon fiber, glass, structural foams and epoxy with either 250f/350f cures using machined molds. The tolerance requirements are really high. I did get some interest from some well known and respected boat builders in new technologies but ultimately they just aren’t interested. They have layup schedules they trust, processes that are pretty foolproof. (And they are cheap)

Moving to epoxy requires a whole new layup schedule. The fabrics, the cure, fillers, are all different, you’ve got the extra painting step. Very few builders have the desire to hire engineers to develop the new process, test it and ultimately change everything they do in production. You can’t just copy published layups and hope that works, this is production work, not a one off in some guys garage. Liability can be a big problem.

I feel like epoxy is way easier to use, is not hydroscopic, lower VOC’s, and is overall a much, much better resin, but I think most production builders don’t care. 

That VOC issue may ultimately force builders to go to closed molds and bagging, etc. The fumes are really bad for your health.


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## Sam K (Apr 24, 2020)

lemaymiami said:


> One other thing to keep in mind about “new” or just plain different technology. There’s always a learning curve and I can well understand a manufacturer wanting to stick with what they know will work as opposed to what they might have to make a mistake with while learning to use it properly…


Definitely, I think that’s what it comes down to. The manufacturing process with ester resins and accompanying materials like gel coats are so well established. That is what may well convince me to go vinylester


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## Sam K (Apr 24, 2020)

Silent Drifter said:


> I thought this was the reason 🤔
> 
> Chopped strand mat is also known as fiberglass mat. It is made up of short strands of fibers that are randomly oriented and held together with a resin binder. The resin binder needs styrene to dissolve properly. This makes it incompatible with epoxy resin


Getting rid of CSM can be used as a great advantage of epoxy though because CSM is weak and heavy. They make special epoxy compatible CSM but it’s super expensive


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## Sam K (Apr 24, 2020)

Fishtex said:


> I’ve got to agree with Capt Bob here. And I too have worked in the aerospace composites world and poly or vinyl resins are pretty much unheard of unless it’s a situation with legacy military aircraft and the spec dictates.
> 
> Anything new is all carbon fiber, glass, structural foams and epoxy with either 250f/350f cures using machined molds. The tolerance requirements are really high. I did get some interest from some well known and respected boat builders in new technologies but ultimately they just aren’t interested. They have layup schedules they trust, processes that are pretty foolproof. (And they are cheap)
> 
> ...


Thanks this is great insight. VOC’s are a big reason I will bag everything. I value my and my future employees’ health


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## Sam K (Apr 24, 2020)

Machined molds I think are the future, only reason I hand built a running plug this time is I don’t have the money to go the disposable plug route. Though I definitely see the advantages of doing it the old school way too. This boat will double as the demo boat etc and I can sell it to recoup material costs eventually


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## Sam K (Apr 24, 2020)

permitchaser said:


> Your building the boat so your in charge. Build it the way you think it would sell better, then let the market decide. Can't wait to see it and the price


Looking at less than 20k for boat motor and trailer based on my preliminary cost of good sold and margins analysis. That said, that price isn’t for sure as I haven’t even registered an LLC yet or decided on a name, so there’s a lot more work to be done! Hoping to start some level of production by February


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## Sam K (Apr 24, 2020)

Sam K said:


> Looking at less than 20k for boat motor and trailer based on my preliminary cost of good sold and margins analysis. That said, that price isn’t for sure as I haven’t even registered an LLC yet or decided on a name, so there’s a lot more work to be done! Hoping to start some level of production by February


20k for a simple package. More with add ons of course.


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## trekker (Sep 19, 2015)

Silent Drifter said:


> I thought this was the reason 🤔
> 
> Chopped strand mat is also known as fiberglass mat. It is made up of short strands of fibers that are randomly oriented and held together with a resin binder. The resin binder needs styrene to dissolve properly. This makes it incompatible with epoxy resin


You dont need CSM with epoxy.


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## Silent Drifter (Apr 29, 2021)

Sam K & Trekker 👍 thanks for the info,thats what i love about this site ive learned a fair amount from you guys in the know, i appreciate you guys 👍😎👍


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## VANMflyfishing (Nov 11, 2019)

My two cents to throw into the mix. I'm building a skiff with Poly versus epoxy due to weather changes in VA. Humidity is a pain, but poly can be used in many different temperatures. You can add MEKP or a little heat with a heat gun to get it to kick. If you are using Gel Coat, I would suggest epoxy though since poly is porous. I am sealing mine with an epoxy based high build, primer, and paint. 

If you have the system in place, Epoxy is easier to work with. Ratios have to be a little more precise and temperatures have to somewhat warmers (>55 degrees). If you are bagging it, I like poly. I do hate using CSM though...I would get a few testers of each and layup a small section.


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## Sublime (Oct 9, 2015)

VANMflyfishing said:


> My two cents to throw into the mix. I'm building a skiff with Poly versus epoxy due to weather changes in VA. Humidity is a pain, but poly can be used in many different temperatures. You can add MEKP or a little heat with a heat gun to get it to kick. If you are using Gel Coat, I would suggest epoxy though since poly is porous. I am sealing mine with an epoxy based high build, primer, and paint.
> 
> If you have the system in place, Epoxy is easier to work with.  Ratios have to be a little more precise and temperatures have to somewhat warmers (>55 degrees). If you are bagging it, I like poly. I do hate using CSM though...I would get a few testers of each and layup a small section.



Spot on. Anyone familiar with Ecopoxy gelcoat? I really want to use gelcoat on my epoxy build , but don't want to risk poly gelcoat not adhering.




https://www.ecopoxy.com/products/gelcoat/


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## trekker (Sep 19, 2015)

Sublime said:


> Spot on. Anyone familiar with Ecopoxy gelcoat? I really want to use gelcoat on my epoxy build , but don't want to risk poly gelcoat not adhering.
> 
> 
> 
> ...


Ive looked at it a few times while trying to crack the epoxy/gelcoat code. Just cant bring myself to try it. If I remember right, I couldnt find anything about UV protection. The best solution I've found is IMedge ECT 120. Epoxy compatible, but fn expensive.


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## Sam K (Apr 24, 2020)

Sublime said:


> Spot on. Anyone familiar with Ecopoxy gelcoat? I really want to use gelcoat on my epoxy build , but don't want to risk poly gelcoat not adhering.
> 
> 
> 
> ...


I’ve looked into the ecopoxy stuff quite a bit, it looks promising to me. I can ask them about UV next time I call.


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## firecat1981 (Nov 27, 2007)

Good luck to you kind Sir, but I'm not sure how you will offer an epoxy bagged and painted boat for under 20k. The paint prep alone will destroy any viable schedules, and you will need a dedicated paint booth for production, and a good experienced painter. You can't do it all if you plan to scale and make money. You can try epoxy gel coats, but they are costly and not popular.

On the other hand if you go with vinylester(or poly), once you pop the part out of the mould it's ready to go. That's the allure, and why so many steer clear of epoxy, or charge 60k+ for an epoxy boat.

As far as CSM goes there's one thing no one here has mentioned I think. Print through. On many of my test layups, whatever fabric I was using would occasionally show through. On a ester build the CSM goes down first and prevents this from happening. It would be a shame to pop a hull only to see you have to sand it down to regel it later. I bought some epoxy compatible CSM to play with and it helped, but its harder to use then normal CSM.


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## Sam K (Apr 24, 2020)

firecat1981 said:


> Good luck to you kind Sir, but I'm not sure how you will offer an epoxy bagged and painted boat for under 20k. The paint prep alone will destroy any viable schedules, and you will need a dedicated paint booth for production, and a good experienced painter. You can't do it all if you plan to scale and make money. You can try epoxy gel coats, but they are costly and not popular.
> 
> On the other hand if you go with vinylester(or poly), once you pop the part out of the mould it's ready to go. That's the allure, and why so many steer clear of epoxy, or charge 60k+ for an epoxy boat.
> 
> As far as CSM goes there's one thing no one here has mentioned I think. Print through. On many of my test layups, whatever fabric I was using would occasionally show through. On a ester build the CSM goes down first and prevents this from happening. It would be a shame to pop a hull only to see you have to sand it down to regel it later. I bought some epoxy compatible CSM to play with and it helped, but its harder to use then normal CSM.


thanks for the input, I definitely would only do it if I can find an in mold solution like ecopoxy “gelcoat”. I’m leaning towards vinylester though at least at first. Talking to some of the aerospace guys I know to try to learn more.


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## Sam K (Apr 24, 2020)

firecat1981 said:


> Good luck to you kind Sir, but I'm not sure how you will offer an epoxy bagged and painted boat for under 20k. The paint prep alone will destroy any viable schedules, and you will need a dedicated paint booth for production, and a good experienced painter. You can't do it all if you plan to scale and make money. You can try epoxy gel coats, but they are costly and not popular.
> 
> On the other hand if you go with vinylester(or poly), once you pop the part out of the mould it's ready to go. That's the allure, and why so many steer clear of epoxy, or charge 60k+ for an epoxy boat.
> 
> As far as CSM goes there's one thing no one here has mentioned I think. Print through. On many of my test layups, whatever fabric I was using would occasionally show through. On a ester build the CSM goes down first and prevents this from happening. It would be a shame to pop a hull only to see you have to sand it down to regel it later. I bought some epoxy compatible CSM to play with and it helped, but its harder to use then normal CSM.


Curious to know, what’s your go to first layer for print through prevention? I’m under the impression 3/4 oz CSM is the way to go, but I’ve recently been told a light and smooth ply like 6 oz cloth is better, at least for tooling gel coats


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## Sam K (Apr 24, 2020)

GC50 Epoxy Compatible Clear Polyester Gelcoat - Easy Composites


Special clear, UV stable polyester gelcoat designed specifically for use on epoxy resin laminates. In stock, expert advice, UK next-day/fast EU shipping.




www.easycomposites.co.uk





wouldnt be practical to source internationally, but this is an interesting product. Also, easycomposites has a fantastic set of YouTube videos on all kinds of stuff for anyone interested in learning


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## firecat1981 (Nov 27, 2007)

I tried 3/4oz with success, and also used veil cloth, but I'm not sure it would be well suited to the task.


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## Sam K (Apr 24, 2020)

http://jp.scottbader.com/uploads/files/4823_epoxy-bonding-gelcoats-brochure-english.pdf



another interesting one for anyone. They appear to have a domestic division.


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## Sam K (Apr 24, 2020)

firecat1981 said:


> I tried 3/4oz with success, and also used veil cloth, but I'm not sure it would be well suited to the task.


Ok, thanks


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## DuckNut (Apr 3, 2009)

Polyester properties are pretty good for small boat construction. Using epoxy will not increase these properties to a level that justifies the price.

I have no idea how you came up with epoxy only cost 10% more - bad calculations- because epoxy is 5-6 times the price and you will use the same amount (close enough) epoxy and poly if you are using the same layup schedule.

Fiber volume, Area – oz/ft^2, Total lb/ft^2 as a common formula.


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## Sam K (Apr 24, 2020)

DuckNut said:


> Polyester properties are pretty good for small boat construction. Using epoxy will not increase these properties to a level that justifies the price.
> 
> I have no idea how you came up with epoxy only cost 10% more - bad calculations- because epoxy is 5-6 times the price and you will use the same amount (close enough) epoxy and poly if you are using the same layup schedule.
> 
> Fiber volume, Area – oz/ft^2, Total lb/ft^2 as a common formula.


Here’s how: Two different layups, epoxy layup is roughly the same strength and is slightly stiffer, but uses far less material.

US composites current prices for poly: 28.60 per gallon, epoxy: 46.70
Poly cost per boat: 14.4 gal, 412 dollars, 543 dollars glass, 955 total
Epoxy cost per boat: 9.6 gallons epoxy, 449 dollars, 585 in glass, total 1034. 8% more expensive. 
Doesn’t account for gelcoat and whatever in mold gelcoat solution I’d use for epoxy so let’s say 15%. Can’t get the customer service reps at the pro set infusion resin distributor to give me a dang quote so there’s that variable too

Steve at UScomposites (very helpful and knowledgeable guy, would recommend for any technical questions) said my epoxy layup should work fine with their vinylester. Going to test that next if I can get my hands on some and see if I lose any relevant mechanical properties.


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## DuckNut (Apr 3, 2009)

You are playing with drooling attorneys!

You can use a chopper gun and make a solid glass hull that is 1/4" thick. Or you can use a single cloth of Kevlar that is 1/2 of a millimeter thick.

What you just described is doable and could possibly provide adequate stiffness. It will not provide adequate impact resistance. The Lithium skiff has a thin skin and it uses 131 yards of 10oz, 149 yards of 1.5 mat and 290 sq ft of core - $1,050 + $850 + 10 sheets of core. 

If you go into production with something this this you will be fixing boats, not building them. This will get your name slobbered all over social media nd you'll go out of business.

The typical layup for epoxy and poly is very similar in thickness (materials are sometimes different) but the general thesis remain nearly identical. 

I wish you all the luck in the world but a boat but the materials you are portraying don't calculate well.

Here is a clip from their website










They don't have an epoxy for less than $80 per gallon. Not the $47 you say. $47 is per 1/2 gallon. 

Something is not adding up. Read this: His cost is $7,100 per skiff

The Cost of Building a Custom Skiff - Lithium Skiff


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## Sam K (Apr 24, 2020)

DuckNut said:


> You are playing with drooling attorneys!
> 
> You can use a chopper gun and make a solid glass hull that is 1/4" thick. Or you can use a single cloth of Kevlar that is 1/2 of a millimeter thick.
> 
> ...


I don’t want to give away the specifics of the layups, but it contains on average roughly the same amount of glass as Morejohn’s 10 oz cloth based layups. 

my math above is just glass and resin, the core will cost me more than glass and resin combined at current prices. Morejohn’s number is glass, resin, core, hardware, buckets, etc, he says 4290 for glass core and resin. Including core, miscellaneous stuff and extra resin for putty I got something around 3 to 3.5 grand for mine, which adds up because my boat is much smaller than the lithium. 

46 or 48 dollars is based on buying their resin in bulk, which I clearly could do given the huge shelf life of epoxy. Bulk price of medium hardener: 1284/26.6 gallons, 48.27 per gallon. Slow hardener slightly cheaper. 

You make a very good point about needing to err on the side of overbuilding it to avoid any legal or warranty issues. I’ve been thinking from the perspective of engineering a product that performs as well as it possibly can while being as light as possible, but I guess I may need to give up a few lbs to buy myself some more protection. Gotta assume that people will drive it into an oyster bar at 30 mph


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## Sam K (Apr 24, 2020)

How’s the impact resistance of CSM compared to wovens? I know CSM sucks in just about every other physical property but I haven’t read much about impact


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## DuckNut (Apr 3, 2009)

Glass boats are made from chopper guns every day. and millions that are over 20 years old still being used. A chopper gun boat is basically the same as csm except it is not in the form of csm. CSM is a bulker- used to add thickness and hold the resin together. Thickness is part of the layup schedule.

Comparing csm to woven is not a real comparison. With that said woven cloth is great for adding stiffness but not impact. CSM is for adding bulk not stiffness but adds impact protection. Woven roving is both of of these but the print will show through.


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## Hooked Up (Aug 8, 2016)

Sam K said:


> So I’m starting to think about the specifics of mass production on the prototype boat I’ve documented in the bragging spot section. I come from an aerospace background, and the standard for resins and construction is epoxy infusion resin. I know lots of companies are doing infusion with vinylester and polyester, but everyone who is anyone in the skiff industry seems to run away from epoxy. I’ve figured out already that the cost of production difference is minimal. There are ways around the gel coat issue by using “epoxy gel coats”, really just epoxy with fillers and pigments, or by spraying awlgrip after the parts come out of the mold. On paper, epoxy is far clear of the other resins in many different ways. Some big power boat companies like Scout, a lot of yacht and sailboat companies, and premium canoe folks have made the switch. I’ve had a great experience building my first two boats and my prototype out of hand laminating epoxies.
> So, I can only assume I’m missing something as to why the skiff industry hasn’t followed. I’d love to hear what folks with more hands on experience than me, especially in infusion and marine mass production, have to say.


Close friend runs one of the cutting edge skiff production shop. We were talking 6 months ago. I asked him the same question you raise here. Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


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## firecat1981 (Nov 27, 2007)

Hooked Up said:


> Close friend runs one of the cutting edge skiff production shop. We were talking 6 months ago. I asked him the same question you raise here. Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


Proof or it didn't happen. What shop? Where's the data? I have not seen any tech sheets or comparisons that have poly equal to good epoxy. Vinylester is closer in strength and moisture resistance, but still not as good.


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## Sam K (Apr 24, 2020)

Hooked Up said:


> Close friend runs one of the cutting edge skiff production shop. We were talking 6 months ago. I asked him the same question you raise here. Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


Interesting, thanks for the input. I will say I’ve been looking more at specific resins and their technical data, and I’ve found a few vinylesters that approach the cheaper epoxies in key categories. I’ve 99% decided I’m going to go vinyl, at least at first. Maybe a good quality poly for the cap but probably all vinyl to keep things simple


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## Sam K (Apr 24, 2020)

I also haven’t found a poly that approaches epoxy though, I think chemically it’s not possible


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## Half Shell (Jul 19, 2016)

Hooked Up said:


> Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


I'm asking this, not making a comment... isn't that what vinylester is? I always thought it was essentially polyester fortified with epoxy; a hybrid in a sense. Am I wrong on that?


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## Sam K (Apr 24, 2020)

Half Shell said:


> I'm asking this, not making a comment... isn't that what vinylester is? I always thought it was essentially polyester fortified with epoxy; a hybrid in a sense. Am I wrong on that?


that’s my understanding more or less. I’m sure it’s super complicated but I’m not a chemist


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## firecat1981 (Nov 27, 2007)

It's a bit more complicated, yes.

"Vinyl ester resin, or often just vinyl ester, is a resin produced by the esterification of an epoxy resin with acrylic or methacrylic acids. The "vinyl" groups refer to these ester substituents, which are prone to polymerize and thus an inhibitor is usually added. Wikipedia"

So it's not really related to polyester resins, but more it's own product. It's much better for production, but not as strong or water resistant as full epoxy.


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## trekker (Sep 19, 2015)

Hooked Up said:


> Close friend runs one of the cutting edge skiff production shop. We were talking 6 months ago. I asked him the same question you raise here. Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


Has your friend figured out a way to avoid CSM with these new Polyesters?


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## birdyshooter (Sep 17, 2019)

I would simply say epoxy is cost prohibitive. What you need to look at is the adhesive properties of these resins. Poly and vinyl don’t adhere to squat. Where as epoxy will stick to snot. Once you do a layup with poly/vinyl that’s that, any additional work to it will have to be made with epoxy for proper adhesion.


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## birdyshooter (Sep 17, 2019)

A good overview….



https://compresdev.co.uk/CRD%20The%20Use%20and%20Application%20of%20Epoxy%20Resin%20vs%20Vinylester%20vs%20Polyester.pdf


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## Sublime (Oct 9, 2015)

Yeah, that is a pretty simple overview. I worked at a place for 16 years that made pipe and tanks for the chemical industry. 99.999% was done with vinylester resin. When there were really nasty chemicals involved, we made dual laminate pipe and tanks with something like a PVDF liner encased in fiberglass. I don't ever recall buying any epoxy resin in all of those years.


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## Sam K (Apr 24, 2020)

that overview reminded me of something I wondered a while back. Vinylester and poly don’t bond well to Kevlar or carbon. You’re supposed to use epoxy with them. Are all the companies selling fancy carbon/Kevlar boats just ignoring that?


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## birdyshooter (Sep 17, 2019)

Sam K said:


> that overview reminded me of something I wondered a while back. Vinylester and poly don’t bond well to Kevlar or carbon. You’re supposed to use epoxy with them. Are all the companies selling fancy carbon/Kevlar boats just ignoring that?


I believe vacuum bagging and layup schedules resolve these issues.


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## birdyshooter (Sep 17, 2019)

One of the skiff pioneers on here has stated many times that the cost, weight savings, and labor involved in using high speed materials really isn’t that beneficial at the end of the day.


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## Sam K (Apr 24, 2020)

birdyshooter said:


> I believe vacuum bagging and layup schedules resolve these issues.


Makes sense. I’ll have to do more testing when I get my own vac bag equipment. Im limited to hand layups now because if I use the vac equipment at UF they have a legal right to any intellectual property I produce. Can’t have that


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## birdyshooter (Sep 17, 2019)

Sam K said:


> Makes sense. I’ll have to do more testing when I get my own vac bag equipment. Im limited to hand layups now because if I use the vac equipment at UF they have a legal right to any intellectual property I produce. Can’t have that


Do some research into balsa core. It might surprise you.


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## Sam K (Apr 24, 2020)

birdyshooter said:


> Do some research into balsa core. It might surprise you.


Will do! Don’t want any organic cores susceptible to rot in the skiff though.


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## Half Shell (Jul 19, 2016)

Sam K said:


> Will do! Don’t want any organic cores susceptible to rot in the skiff though.


I don't proclaim to be a boat-building expert by any means and I am following this thread to learn more than comment... that being said... my cousin who shapes and builds some of the finest custom surfboards and paddleboards for a living only uses foam core because of the short supply of balsa. His personal boards are all balsa / epoxy boards.

I just paid him $3200 (with the family discount) for two custom SUP that are foam and epoxy. I would have paid more for balsa but couldn't get it with the covid supply chain.

Between that and dad's custom carolina sportfisher.... I'm not sure I understand the aversion to wood in boat building.


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## firecat1981 (Nov 27, 2007)

Did someone mention balsa? Sorry through up in my mouth a bit, lol. Balsa was a good choice years ago for light weight and strong coring, but it soaks up water and turns to mulch faster then typical marine plywoods. While they might have merits in surfboards that spend very limited time in the water and dry out quickly, I wouldn't want it in a boat these days. The newer generations of cross-linked foam core are a much better option and just as strong, with no rot issues, cheaper price, and better availability.

And this is coming from a wood boat builder, lol. Seriously, the foams have gotten so good and cheap that there is no reason to use wood anymore imho.


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## Sublime (Oct 9, 2015)

I thought some of the big sport fisher guys tried to migrate to foam but the boat ended up riding like poo because it was lighter than a balsa core boat. I dunno.


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## Half Shell (Jul 19, 2016)

Sublime said:


> I thought some of the big sport fisher guys tried to migrate to foam but the boat ended up riding like poo because it was lighter than a balsa core boat. I dunno.


That would be surprising to me being that consensus 20 years ago among the Carolina crowd was how much better a Jarret Bay rode compared to my old heavy Hatteras or a Viking.

With all the negative talk I hear about saturated foam cores, I'm just not so sure it's a better mousetrap. Isn't the point that both have to be encapsulated in resin and if you drill into that wood or foam core and don't seal it in epoxy, that you're going to have a pile of shit no matter what?

Wood rot or waterlogged foam, which is worse? Is waterlogged foam any lighter or stronger than rotting wood?


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## Sam K (Apr 24, 2020)

I’ve built two plywood-epoxy boats. Not even marine plywood, just (formerly) cheap pine. I learned a ton and they’re still not rotting. Won’t ever touch plywood again for skiff building though now that I’m serious. 

Another factor to why the industry has left plywood I think: foam is just so much easier to work with. Way, way easier


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## Sam K (Apr 24, 2020)

Is the waterlogged foam that people are having issues with the low density 2 lb stuff that people squirt under floors?


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## firecat1981 (Nov 27, 2007)

Half Shell said:


> That would be surprising to me being that consensus 20 years ago among the Carolina crowd was how much better a Jarret Bay rode compared to my old heavy Hatteras or a Viking.
> 
> With all the negative talk I hear about saturated foam cores, I'm just not so sure it's a better mousetrap. Isn't the point that both have to be encapsulated in resin and if you drill into that wood or foam core and don't seal it in epoxy, that you're going to have a pile of shit no matter what?
> 
> Wood rot or waterlogged foam, which is worse? Is waterlogged foam any lighter or stronger than rotting wood?


The majority of the wet foam complaints are not core related. It is the oldschool 2lb floatation foams that were not truly closed cell, and guys drilling into sealed chambers. The higher density cross linked coring is a different animal. Now there were some issues back in the day when they first started using foam core. They had a lot of delaminations, deformities, crushed cores, and yes wet foams, but things have advanced a bit in the last 20+ years.

Closed cell foams give you a level of protection. If you pierce the fiberglass it can take weeks to months before the foam will be effected and take on water If at all. With wood core, once pierced, it takes on water immediately and starts to rot soon after. Wood rot is definitely worse then waterlogged foams. With rot you need to cut everything out and rebuilt. With wet foam you can dry it out most times and reseal it.

Another thing to consider is fair movement. As you wet out wood with resin and glass it tends to soak in and can expand the grain making it move. Not a huge issue, but it makes a less fair surface and adds to fairing work. Foam core is stable and closed cell so the resin sits on the top layer instead of soaking in. So what you start with you generally end with.

As far as the old sport fishers go, a better designed hull doesn't need the added weight. Lighter hulls are designed to cut through waves, the old heavies more pounded through them adding to vibration. But the heavier boats are generally more comfortable at rest then the lighter counterparts. But we ain't going out in 6-8ft seas in our skiffs now are we?


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## birdyshooter (Sep 17, 2019)

To what @Half Shell said…. Exactly!! Keep either material dry and you’re good to go!! Issues come from idiots with drills and parking their boats under a pine tree for shelter.


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## Sam K (Apr 24, 2020)

IMEDGE Archivi - Polynt







www.polynt.com





still planning on going vinylester, but a guy who works for a yacht company told me they use this for epoxy parts. Figured I’d pass it along


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## Smackdaddy53 (Dec 31, 2012)

birdyshooter said:


> To what @Half Shell said…. Exactly!! Keep either material dry and you’re good to go!! Issues come from idiots with drills and parking their boats under a pine tree for shelter.


I like what Chittum used on their Challenger hull.


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## birdyshooter (Sep 17, 2019)

Smackdaddy53 said:


> I like what Chittum used on their Challenger hull.


What’s a challenger?


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## millerrep (Apr 14, 2014)

I for one, love epoxy plywood construct, it is simple and easy, no vacuum needed to make foam panels. Epoxy plywood skiffs perform great, and have a nice sound on the water.


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## Papa (Oct 20, 2021)

Sam K said:


> So I’m starting to think about the specifics of mass production on the prototype boat I’ve documented in the bragging spot section. I come from an aerospace background, and the standard for resins and construction is epoxy infusion resin. I know lots of companies are doing infusion with vinylester and polyester, but everyone who is anyone in the skiff industry seems to run away from epoxy. I’ve figured out already that the cost of production difference is minimal. There are ways around the gel coat issue by using “epoxy gel coats”, really just epoxy with fillers and pigments, or by spraying awlgrip after the parts come out of the mold. On paper, epoxy is far clear of the other resins in many different ways. Some big power boat companies like Scout, a lot of yacht and sailboat companies, and premium canoe folks have made the switch. I’ve had a great experience building my first two boats and my prototype out of hand laminating epoxies.
> So, I can only assume I’m missing something as to why the skiff industry hasn’t followed. I’d love to hear what folks with more hands on experience than me, especially in infusion and marine mass production, have to say.


Epoxy is not UV stable I do not believe and I also don’t think you can gelcoat over epoxy.


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## firecat1981 (Nov 27, 2007)

millerrep said:


> I for one, love epoxy plywood construct, it is simple and easy, no vacuum needed to make foam panels. Epoxy plywood skiffs perform great, and have a nice sound on the water.


You don't need to vacuum foam panels, you can hand laminate with epoxy just like plywood. With products like Carbon Core PE you can use it as a near direct substitute for ply, it costs less then good marine ply, no rot issues, and you can actually find people who will buy it when your done.
I've built 4 boats with epoxy and ply, but there's just no point to it anymore with better and cheaper stuff readily available.


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## millerrep (Apr 14, 2014)

firecat1981 said:


> You don't need to vacuum foam panels, you can hand laminate with epoxy just like plywood. With products like Carbon Core PE you can use it as a near direct substitute for ply, it costs less then good marine ply, no rot issues, and you can actually find people who will buy it when your done.
> I've built 4 boats with epoxy and ply, but there's just no point to it anymore with better and cheaper stuff readily available.


10/4 - 
Not familiar with Carbon Core PE. My reference in my mind was really poly on core, not epoxy on core. I could never bring myself to spend for core, but at $ 95 for 3/4 I‘d reconsider on the next one. Still like the way wood sounds on the water and it catches fish, and holds a screw.


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## firecat1981 (Nov 27, 2007)

You shouldn't be screwing into wood, that's the #1 reason you get rot. Once the sealant fails it's a direct route for water into the core. Always use the drill fill drill method!
As far as sound goes, I'm not sure you would notice a difference, I can't. It still sounds way better then an uncored hull.


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## DuckNut (Apr 3, 2009)

millerrep said:


> 10/4 -
> Not familiar with Carbon Core PE. My reference in my mind was really poly on core, not epoxy on core. I could never bring myself to spend for core, but at $ 95 for 3/4 I‘d reconsider on the next one. Still like the way wood sounds on the water and it catches fish, and holds a screw.


Never drill/screw into wood core. Bad idea.

I agree with you on the sound of wood. The foam core has a high pitch ping to it. Also, there is such a thing as building too light and having your skiff end up like a beach ball. Need a compromise.

The Carbon core is just at home with poly as it is with epoxy.


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## trekker (Sep 19, 2015)

What gelcoat are the few epoxy builders using in mold? I've found ECT 120 from Poly NT. Is that pretty much the only epoxy compatible gel available?


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## DuckNut (Apr 3, 2009)

trekker said:


> What gelcoat are the few epoxy builders using in mold? I've found ECT 120 from Poly NT. Is that pretty much the only epoxy compatible gel available?


No, there are others.

Crystic, Resolcoat, and I am sure there are others as well.


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## trekker (Sep 19, 2015)

DuckNut said:


> No, there are others.
> 
> Crystic, Resolcoat, and I am sure there are others as well.


Thanks Duck!


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## Sublime (Oct 9, 2015)

Another option to use gelcoat on an epoxy build may be to use Total Boat's Total Protect as a primer. I have been in contact with a Jamestown Distributor representative and in short, he said to

Use at least two coats of Total Protect primer
Let the primer dry for 5-7 days
Then sand with 80-120 grit


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## DuckNut (Apr 3, 2009)

Sublime said:


> Another option to use gelcoat on an epoxy build may be to use Total Boat's Total Protect as a primer. I have been in contact with a Jamestown Distributor representative and in short, he said to
> 
> Use at least two coats of Total Protect primer
> Let the primer dry for 5-7 days
> Then sand with 80-120 grit


I think he is looking for a solution for building in a mold.

But your idea works well out of the mold.


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## trekker (Sep 19, 2015)

Hooked Up said:


> Close friend runs one of the cutting edge skiff production shop. We were talking 6 months ago. I asked him the same question you raise here. Seems polyester resins have been upgraded with newer properties. Bottom line, just as strong, less expensive and lighter.


So, no mat needed with these new super polys?


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## sydngoose (Oct 1, 2017)

I use epoxy on all my boat builds: It is easy to work with: not cheap, but what is these days? TOUGH as nails, literally once properly cured.


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