Fiberglass Construction 101

[Froggystyle]

Fiber Reinforced Plastics (FRP) was first applied to custom boats in the middle part of last century. It had been used in some industrial applications earlier, but it was the California boat scene that began the wholesale use of FRP in boat hulls. What a huge performance and utility upgrade from wooden boats! Far lighter, far stronger, far more durable.

The process, called "wet lamination" was easy enough to implement. You build a mold, which could be easily created from your wooden boat design you already may have as a female version of the boat you want to build. You wax the mold so your parts will release, gelcoat your mold and begin the laminates. You usually do what is called a "skin coat" of essentially non-structural Chopped Strand Mat (CSM) to prevent a thing called transfer and then start laminating. You soak fiberglass cloth in varying thicknesses in catalyzed resin (a two part plastic that gets hard) and lay it into the boat, rolling out any air bubbles with your fingers and various lamination tools. With enough resin, you can pretty much eliminate all "dry" spots and continue laminating one over another until you achieve your desired total thickness...

Let's talk about resin for a minute...

Resin is a set of long polymer chains that have what amounts to open sockets on them. They won't bond to each other because there is nothing in the resin to allow these "sockets" to attach to other "sockets", so they float around in a fluid manner. A large percentage of resin is comprised of various thickeners and thinners. Styrene is a major component of most resins, as are various petroleum based thickeners that make it easier to laminate with.

Catalyst comprises a bunch of "plugs" that like the "sockets" in the resin, won't join with each other. It stays fluid until combined. There are as many different types of catalysts as there are resins, but we will stick to the basics.

Also included in the mixture, but not usually controlled by boat builders is a promotion agent. We promote resin ourselves to control our mixture even better, and we use a product called "Cobalt" but I won't get into it. Essentially, it is an accelerator that will alter the speed at which the catalyst and resin react with each other, and at what heat.

Here comes the magic... Once you add the correct amount of catalyst to the resin it starts a chain reaction that allows the sockets of the resin to join with the plugs of the catalyst. As they are spinning into position at a molecular level, it develops heat. In the business, this is called an "exothermic" reaction. Each one of those molecules once joined is a small little bit of rigid material at the molecular level. As you get more and more of these small things becoming rigid, it takes more and more friction to get them to spin around and lock into each other. This generates even more heat. Left to its own devices in a large volume, normal General Purpose (GP) resin will exotherm to well over 350 degrees, enough to burn buckets and floors.

The resin, as stiff and rigid as it is, is barely structural on its own. It is brittle and unreinforced. Ponds of resin are weak spots in composites, and wet lamination is a strange balance between trying to add enough resin to make sure it is all the way wet, and pulling enough out to keep weight down and strength as high as can be expected.

 

[Froggystyle]

The actual process of the resin and catalyst becoming rigid is called "cross-linking". The goal is to have all of the resin chains have exactly enough catalyst molecules to react with and avoid a molecular game of musical chairs. If everything has a place, the structure becomes very strong and somewhat impenetrable. The fillers that are in the resin prevent the thing from being totally solid, and lower quality, cheaper fillers will decrease the strength of the resin considerably.

All of this takes place during what is considered a "primary" bond. All of the things move around while liquid and bond with each other. With a really strong resin, there won't be many chairs left at all in this game, so it becomes somewhat impenetrable, even at the molecular level.

Now... let's talk about fibers...

 

[Froggystyle]

FRP is comprised of essentially two components... Fiberglass fibers and hardened resin. As you can see, there is a whole lot more to the resin than you might have imagined, and there is a hell of a lot more to the glass than you would imagine either...

The strength of FRP is neither in the glass or the resin... it is in both. They work together to create a "composite" structure. About "composite"

I hate misused words. This is one of them. A tree is composite. All that it means is that it is comprised of dissimilar materials that combine to create a single structure. Wood combined with 'glass is a composite. So is a peanut butter and jelly sandwich for that matter. When someone claims to have an "all composite boat" you would be well within your purview to ask them what they mean by that. Enough...

Back to FRP structures. The glass is usually comprised of a roll of fiberglass strands in some kind of a matrix. For anything used structurally, it will have long fibers either woven or sewn into a sheet for easy installation. You see, fibers have strength only in tensile. Meaning, you can pull a fiber and it will yank from the other end of the sheet... it is continuous. This is where it becomes strong. The fiber is essentially glued to the fibers next to it, which share any sort of load imposed upon it. Multi-directional 'glasses unitize and create strength in mulitple directions. It gets way deeper into the engineering of the structure, but just understand that the way fiberglass gets it strength is by using the tensile resistance to elongation of the fibers embedded and glued to it with resin as its strength.

Lets work with just a sheet of cloth for a minute...

If you laid out a 4' x 8' sheet of a woven cloth on a table, wet it out with catalyzed resin and let it kick off, you would be able to basically analyze it's strengths. It would be very stiff in linear pull. It would not stretch from end to end, because some strands on the end you were pulling would go all the way through the sheet to the other side. It would also be strong width-wise for the same reason. It would however roll up relatively easily. This is because there is nothing creating any sort of tensile strength to prevent it from happenning. With no cross section to speak of, you would have the flexibility of the resin's physical properties working to allow it to bend and not break. This is called the "modulous of elongation" in engineering circles.

Fast forwarding on that thought for a second, if you make it thicker and thicker, you create additional strength in cross section, and as such resistance to flexing.

Long story short, When you hold a pole up or something with wires, the wires don't give any resistance to compression, you can push something towards a wire easily. So, you put another wire on the opposite side. Both wires working in tension prevent movement in that axis. That pole can fall 90 degrees to that strength however. So, add two more wires and the pole basically is immovable, and all because wires in tension are holding the position.

Clear as mud, but this should give you an idea of how steep the learning curve has been for me over the last six years.

 

[Infomaniac]

DUH !!

:joke :joke

 

[Froggystyle]

DUH !!

:joke :joke

I've got a lot more coming on the subject, but I had to eat Christmas dinner and ran out of energy...

Next up is resins...

 

[RiverDave]

My brain hurts from reading that... Definately good knowledge to know though! If you read it, you begin to understand why extra "resin" in boats isn't a good thing.

RD

 

[Froggystyle]

There are MANY different types of resins and epoxies out there. They stratify into some basic categories however, and have different properties as a result...

General Purpose resin. Also known as GP. This is the cheapest stuff you can buy essentially. It has the weakest physical strength and elongation properties, and as you can imagine is the least expensive way to go as well. They are primarily poly-ester resins. The primary bond as we talked about earlier is partially compromised by inexpensive fillers and thinners, and as such it doesn't cross-link efficiently or completely. There are a lot of open chairs in this metaphorical game of musical chairs. Strangely, the benefit to this is in a stronger secondary bond characteristic. More on that later...

Nobody in the boat business is going to advertise use of GP resins. It is done to save money, and is essentially "strong enough". Some of the real downfalls of using a GP resin, especially in the skin coat layer is that it has big, open gaps in it at the molecular level. The fillers and such, combined with a not particularly strong resin in the first place allow these gaps. It is a faster reacting resin as well, which creates more heat than other types because of how quickly it goes from liquid to solid. The bummer with these gaps is that the resin allows water to permeate through it relatively easily from an area of higher pressure/density (outside water pressure) to low pressure/density (empty boat in the water) and can easily create blisters. Water finds its way into the laminate, and then expands once the boat is brought out of the water. That is a rough description, but the basics.

Tough to catch people using GP resin in your boat. You need to know what to look for (it is basically blue usually) and keep an eye on the drums if you get an opportunity to do a shop tour. A modern high performance boat should not include GP resin anywhere in the structural laminate.

The next step up is a vinyl-ester and poly-ester blend. This as you can imagine is a carefully blended concoction that combines some of the properties of the stronger vinyl-ester but cuts it with poly-ester for cost purposes.

A full Vinyl-ester resin is the way to go on the boats we run. Stronger, denser and almost fully cross-links when kicked. It is roughly double the cost per gallon of poly-ester, but you get what you pay for. The physical properties are up to ten times stronger than a polyester while retaining a high modulus of elongation.

Vinyl-ester is the strongest you are going to get with a standard type of fiberglass resin... and while there are many different types and brands, all having individual properties that may make one better in application than another, they are all pretty good, and fully applicable in a high performance boat.

Stepping up into epoxies and such, there are many different types of them as well. Improved properties over even vinylester are greater strength, greater M.O.E. before failure, longer working times, cooler exothermic phase etc... Usually a far greater expense, and many require a post-cure phase where you actually have to heat the part up to greater than 140 degrees to get it to cure. Some activate even higher over 200.

 

[LHC30]

Well Wes, now that you have me reading...where is the rest?

Everyone should visit your shop and watch the infusion process to help put the rest of the build process into perspective.....

 

[Froggystyle]

We have covered the principal known as "primary bond"... which is the bond that resin makes with itself as it is curing. We talked about the exothermic heat created as they all move into place and become rigid, and we discussed how a high quality vinyl-ester resin is very complete in it's cross linking process... such that there isn't many sockets left when completely cured, and not many plugs either, to use my prior metaphor...

When a bucket of catalyzed resin kicks off and becomes hard, from a physics level it becomes essentially a single large molecule. It all kicks uniformly, and all hardens at the same time.

When you have one of these molecules, and you wish to join it with another one you are creating (laminating another layer into a boat for example) you are counting on a principal called "secondary bond".

Each resin you choose when engineering has different physcial properties. In our case, our naval architect hired a composites engineer to decide not just our lamination schedule, but the actual materials we were going to use in each case. Many of the "physicals" of the resins are strong enough across the board to do the job, but it really takes a Mechanical Engineer (M.E.) to begin to discern how to optimize the laminate. One of the properties is it's secondary bond characteristic, which is to say how well it will stick to itself once it is cured.

The strongest resins are the tightest molecules and kick most completely. This is a negative when it comes to secondary bond however. You have a stronger initial resin, but the joint where the next layer bonds to the original is weak in comparison.

GP resin, while the weakest physcially of what we have discussed actually has a strong secondary bond because of all of the non cross-linked resin and catalyst parts.

You see the one side is already hard. It can't move at all. When you apply a new batch of catalyzed resin, it struggles to find a place to bond at the molecular level. With all of the seats taken up, it ends up just bonding to itself, and only peripherally to the other part.

You can physically break up the molcules by sanding with aggressive grit paper and roughing the surface, but you are only creating a spot for it to bond to that is as deep as you sanded.... meaning... not very deep. If you are going to count on a surface bond like this, you need to support the part physically in some other manner... like a bulkhead or gusset to spread out the force.

Whenever fiberglass is repaired, you run into this problem. Whenever you patch in something in fiberglass you have the problem. What you create is two strong parts with a weak bond between them.

To liken it to a more familiar process, imagine bolting two pieces of metal together. Each piece of metal is strong, and if you pull them apart, generally the bolt will break, not the metal. Same deal. Plenty of things are bolted together in our world, but you need to be conscious in composite engineering that you have a weak spot in between strong parts.

 

[Froggystyle]

Well Wes, now that you have me reading...where is the rest?

Everyone should visit your shop and watch the infusion process to help put the rest of the build process into perspective.....

Just getting there... none of this is cut and paste, so I am trying to collect my thoughts on each section before putting it up.

Plus, I am working right now...

 

[Froggystyle]

I don't purport to have graduated college with an engineering degree, nor do I pretend to have it all figured out. Let's start with that as a basis...

There is no doubt however that I have become an engineer. I have designed all of our hardware in CAD, designed and engineered everything from hinges to new bulkheads, and on that path I learned an awful lot about mechanical engineering from the people I hired to put a pen to paper on the important stuff like hull design and composite structure.

I will share with you some basic thoughts and truths regarding this aspect of the engineering done on the boat...

1) By the time fiberglass is rigid enough to peform as a boat hull, it is essentially three times stronger than it needs to be to do the job.

This was one of my first information bombs dropped on me by my engineer when we first started designing the boat. If you just keep building up surfaces in straight glass, you will have essentially three times the weight needed to do the job.

This of course glosses over things like motor mounts, reinforcements, through hull fittings etc... but you see the point.

Rigidity and strength are two completely different things. A surfboard, for example is very rigid, but very weak. They break, they can be punctured easily and they ding like they were meant to. Conversely, a snowboard isn't particularly stiff, but it is very strong. Both are FRP products, how are they so different?

The difference is core.

In the early 1900's, the structural steel "I" beam began service in high-rise buildings. Prior to it's use, solid beams and masonry were used. This limited the height you could go, because you just couldn't get the building to support its own weight. The "I" beam effectively increased the cross section (rigidity) while decreasing the weight required to get the edges out there... Beam theory has it's origins as far back as Galileo, and is truly one of the more important engineering discoveries ever. It is interesting, and for more reading on that and the rest of the Euler-Bernoulli Beam Equation theory, click here...

http://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equation#History

Coring a composite has essentially the same effect. You spread the structural components out to increase rigidity. In pure FRP, you do it with brute thickness (hence the 1" thick keels in boats of yesteryear) and it comes with increased weight, expense and durability. Remember, each of those secondary bonds on a thick hull plays a role with regard to potential delamination.

A cored composite is considered by engineers to be essentially an "infinite I beam" in the sense that it has rigidity in every axis, not just one like an I beam. They type of cores play a big role in this, and we will get to that later.

2) Unbalanced cored composite structures are only as strong as the strongest sub-structure.

When you core fiberglass, it is important to put as many ounces of material on one side as you do the other. This balances the strength on either side of the core and allows it to be as strong as it possibly can. This is a tough theory to describe in words, so I will show you a quick pic...

The top pic is a comparison of a normal boat hull layup and our cored, infused layup. Most of the boats out there have something similar to the one on the left. It consists of a gelcoat, a skincoat, outer laminate, coremat to bed the core into, a 1/2" - 3/4" balsa core and then another inner laminate. The bottom pic is what an engineer sees though...

The "zones" I have highlighted in each laminate show the individual "structures" that are in each construction. With the secondary bond kept in mind, you can see that the left laminate is comprised of a cored structure (light green), a coremat cored structure (red) and a pure FRP structure (blue) all with secondary bonds between them. Each of those structures has different properties of elongation, rigidity and puncture resistance, so under stress, each act WAY differently and you get what is termed "delamination" related failures. Delamination is nothing more than the secondary adhesion bond breaking apart from the individual structures. You are left with three independent structures which pretty quickly destroy each other.

On the right you have an infused piece. There is only one secondary bond... that of the structure of the boat to the aesthetic-only skincoat layer. It is non-structural, and since wet part of the lamination is done in one shot, there are no secondary bonds to consider. Note that it is balanced inner and outer, and as such as the maximum strength possible to achieve with the available reinforcements and core thickness. This is optimized.

The part on the left weighs about 9.5# per foot... about standard. The one on the left weighs three. It is approximately eight times stronger and four times stiffer.

3) Exotic materials are only beneficial if you have already optimized your application of them...

Lets say you have something as simple as a rear sprocket on a motorcycle. If you have a Harley, adding an aluminum chainring would be totally stupid for any reason other than aesthetic. Sure they are lighter, but with 500# of bike, chrome steel exhaust, big huge leather seat, windscreen, leather saddlebags etc... what good is saving 1 pound in a sprocket? The negatives are greatly reduced longevity, greatly reduced strength and hugely increased cost.

If you want to switch out that sprocket on a fully optimized 999R Ducati for that last bit of weight savings... when you have already gone to a Titanium exhaust, carbon fiber cans and bodywork, smaller seat, thinner plastics, no signals or lights etc... then you have a real honest need for it.

Adding carbon, kevlar and the like to a normal custom boat build is throwing good money after bad. Is it stronger? In some ways, yes. Is it more expensive? By four times. Is there negatives? Many. Decreased stability to UV light, it conducts electricity, increases galvanic corrosion throughout all of your systems, and many others. Not to mention that the weight savings is never realized...

You see, as with the weight optimized motorcycle vs. the non-weight optimized, the weight savings is only useful or worth the negatives if you have done everything else.

Here's why...

Carbon fiber is approximately 10% stronger in tensile strength than "E" Glass, which is what we all basically use in various configurations. But how does that help?

Lets say you have a structure similar to a fishing rod built out of E-glass. You need this pole to hold up 100 pounds. With a standard lamination schedule like you see in most all of your boats, lets say that pole uses 40 ounces of cloth as a schedule, and for the sake of easy math lets say the part weighs 10 pounds. A standard wet-lamination process will use about 70% resin and 30% fiber by volume. That means that this structure that is 10 pounds is seven pounds of resin and three pounds of 'glass.

If you substitute carbon fiber for the E-glass, you will be ten percent stronger in tensile, which in this model would roughly result in ten percent more payload. Lets say it will now hold up 110 pounds.

But you only needed to hold up 100 pounds. Is the carbon fiber lighter? No. You are still using a 40 ounce laminate schedule. It is just a bit stronger. You still have three pounds of it in your part. If you weigh 40 ounces of carbon, you will amazingly find that it weighs the same as 40 ounces of glass.

So what if you reduce the amount of carbon by ten percent to have it do the same work for less weight? Well, that will make a difference. Let's see how much...

The three pounds of reinforcement equates to 48 ounces. The seven pounds of resin equates to 112 ounces. If you save 10 percent on the weight of the glass, you need ten percent less resin as well to wet it out. So, your 10 pound part could be reduced by 4.8 ounces of reinforcement and 11.2 ounces of resin. One pound. You can save 1 pound by using carbon and optimizing your schedule.

In contrast, if you optimize the application of the laminate you have a much bigger loss in weight.

Same structure as a model. The resin infusion build process results in a 30% resin volume, 70% fiber. The aforementioned structure still has 48 ounces of 'glass, but now only 14.4 ounces of resin... (which is incidentally still more than perfect, but close to it.) With NO change in lamination schedule or materials, the part just got reduced down to a total weight of 62.4 ounces, or 3.9 pounds.

In summary, if using wet lamination, you can switch to carbon fiber, adjust your schedule and build the part for one pound less and four times the material cost. Using infusion alone, you drop 6.1 pounds, retain even greater structural strength and modulus of elongation and the material cost per pound is the same... but you use 60% less!

With the infusion, a switch to carbon essentially gets you another .4 pounds off, but again at four times the expense. But, if you NEED to lose that additional .4 pounds... it is there for the harvesting.

These are pretty basic engineering principles, but they are valuable to understand, and may help you see through some of the BS being sold by the various members of the industry.

 

[whiteworks]

nice thread, look forward to reading more. throw in few pie charts and this thread is gold

 

[Froggystyle]

nice thread, look forward to reading more. throw in few pie charts and this thread is gold

Here you go...

 

[shueman]

...Adding carbon, kevlar and the like to a normal custom boat build is throwing good money after bad. Is it stronger? In some ways, yes. Is it more expensive? By four times. Is there negatives? Many. Decreased stability to UV light, it conducts electricity, increases galvanic corrosion throughout all of your systems, and many others. Not to mention that the weight savings is never realized...

Really...

 

[Froggystyle]

Really...

Absolutely. It is one of the most nauseating things in the industry right now as far as straight ripoffs to the client.

 

[RiverDave]

Nice Pie Chart..

In all seriousness Wes, I appreciate you taking the time to write that. I have a feeling this particular thread is going to be one of those, few people will read it, right up until it comes time for them to buy their next boat.. LOL When they do, they'll be printing it out and taking it down to the mfg's grilling them 6 ways to sunday.. In that regard it's worth more then gold, to the consumer, and to the industry as a whole.

DR

 

[Froggystyle]

Nice Pie Chart..

In all seriousness Wes, I appreciate you taking the time to write that. I have a feeling this particular thread is going to be one of those, few people will read it, right up until it comes time for them to buy their next boat.. LOL When they do, they'll be printing it out and taking it down to the mfg's grilling them 6 ways to sunday.. In that regard it's worth more then gold, to the consumer, and to the industry as a whole.

DR

That is pretty much the idea. You would have to be pretty interested in composites to read through it... More so I guess to write it... but it is good stuff, legitimate, and gets you thinking.

 

[DaveC]

You know you could have just cut to the chase and saved us all alot of time and reading... Next time give us the executive summary as follows.

The part on the left weighs about 9.5# per foot... about standard. The one on the right weighs three. It is approximately eight times stronger and four times stiffer.

J/K

Read and understood completely.

excellent reading. thanks.

 

[Froggystyle]

You know you could have just cut to the chase and saved us all alot of time and reading... Next time give us the executive summary as follows.



J/K

Read and understood completely.

excellent reading. thanks.

Except it is the one on the right that weighs three...

I have street cred with you after the drywall screw incident, huh?

 

[Waterjunky]

Great information. Very interesting reading for the mechanical geek (like myself) out there who want to know more than "it works". The next logical question that I see is, how long do you think it will be before others in the boating industry take notice of this process and start doing the same thing? I am thinking of major players in the boat market like some of the big name performance manufacturers (Formula, Cigerette, etc) or some of the high end recreational boat builders (Cobalt, Regal, etc).
Do you know of any other boat manufacturers using this technique?

 

[DaveC]

fixed it. WTF??

BTW I believe its some sort of coated outdoor wood screw..... anyhow thats trivial shiat next to important topics such as the infuson.

This is an interesting topic.. They had a show on Discovery recently about construction of composites in airplanes. Just as you described it.

Also what I find interesting is how such a small builder boat builder can take such a giant leap forward in technology while some of the "big names" have not. :hmm what the hell has the world come to when bling is more important than weight in a "performance" application .

I've noticed for a long time the very short list of manufacturers that build them light. Maybe one of these days I can afford one

so when does the next model go into design?

Except it is the one on the right that weighs three...

I have street cred with you after the drywall screw incident, huh?

 

[Froggystyle]

fixed it. WTF??

BTW I believe its some sort of coated outdoor wood screw..... anyhow thats trivial shiat next to important topics such as the infuson.

This is an interesting topic.. They had a show on Discovery recently about construction of composites in airplanes. Just as you described it.

Also what I find interesting is how such a small builder boat builder can take such a giant leap forward in technology while some of the "big names" have not. :hmm what the hell has the world come to when bling is more important than weight in a "performance" application .

I've noticed for a long time the very short list of manufacturers that build them light. Maybe one of these days I can afford one

so when does the next model go into design?

As I have stated many times, this industry thrives on "what worked last week" and continues to trudge forward as a result.

With zero production when I started, I didn't need to concern myself with how my shop did it last week, or what we would have to adapt from. We started from scratch, and we just chose the best, most current process available.

There is a lot of freedom in starting from scratch. We have used all of it.

I am not surprised it is taking its time to catch on though. It is a difficult technology to re-train, and I feel that most companies would be better off hiring completely new for a new aspect of the construction than attempting to re-train wet laminators. The two technologies just do not cross.

 

[Froggystyle]

About to get into epoxies here... anyone want to hear about it?

 

[OCBD]

About to get into epoxies here... anyone want to hear about it?

Sure, let's hear it.

 

[Flying_Lavey]

Damn! This is GREAT stuff to read Wes! Keep it comin!


Hmmm.... a 22' picklefork with infusion layup and an outboard.... :hmm (Haul
Balls!)

lol

 

[Froggystyle]

The last time I weighed in on this section I discussed application of more "exotic" materials and cores. We talked about the pluses and minuses of carbon fiber and other aramid structural reinforcements, and discussed why a properly designed core structure was so important to the physical properties of a fiberglass part.

Epoxies: Like polyester and vinylester resins we have discussed already, epoxies are often used in FRP applications as the formerly liquid substrate of the structural matrix. Like the other resins, they are exothermic, or, to throw another term out there for you, they are a "thermosetting epoxide polymer". They are two part, like "normal" resin, and require a catalyst to form the long polymer chains. Here are some of the stronger positive attributes and properties...

Epoxies have far higher physical strength characteristics than polyester and even vinylester resins. Given the exact same laminates, an epoxy structure will be far stronger without an ounce of weight gain. So much so, that switching to epoxy alone in a wet layup is a larger strength gain than switching to carbon fiber. To pull from prior segments, the reason for this superior strength is found in the really, REALLY tight cross linking of the polymer chains found in epoxies. There are literally NO open chairs in this molecular game of musical chairs left.

Epoxy cures very progressively. Vinylester (VE) and Polyester (PE) resins cure using a "plateau" scale. Meaning, they are cool, cool, cool, etc... for about 1 hour, then they "kick" all at once and get HOT really quickly. This causes an expansion of the material while it is curing, but then a shrinking of the material as it cools off. This creates a "transfer" effect usually and applies the pattern of the fiberglass that was on the inside onto the outside where the pockets of resin got hotter that the less resin filled 'glass. This is the thing where you can see the "weave" of the glass in the surface finish. This slow cure is one of the reasons why it cross-links so completely.

With epoxies, you aren't as likely to get transfer, but they do take their sweet ass time to kick off.

So, it sounds like the wonder material, right? Considering how much thought we put into our own laminate, it should be a matter of at least curiosity why we don't use them in our own boats, eh? The answer is, that there are downsides to epoxies as well...

Epoxy is expensive. While not enough alone to be a driving factor for me, it doubles again the cost of vinylester, which is double the cost of GP polyester resin that I am competing with in many cases. So, add four times the material cost to the mix.

Epoxy cures slowly!. While I have written this thread with our own process in the back of my mind, I am considering the industry at large in my answers as well. The slow kick time of epoxies in a wet lamination environment would mean that all of your lamination epoxy would end up in the bottom of the boat thanks to gravity. With the VE and PE resins, they are thick, and by the time the side laminates start "draining" themselves after lamination, it has already started to kick and get hard, keeping them in place. A quick squeegee of the resin right before kicking will pull enough of it back up the gunwale to re-wet anything that has drained a little. One more reason for the uber-high resin content of the wet lamination process. If you ever watch people wet laminating, you will note that they rarely if ever squeegee "down" for obvious reasons.

Epoxy, like Carbon Fiber is not UV stable! Our boats spend a lot of time outdoors... like... all of it. Epoxy degrades at a very accelerated rate when exposed to UV light. Like, amazingly so. You absolutely have to top coat it with quite a rugged UV resistant topcoat.

Gelcoat won't stick to epoxy Period. Epoxy will stick to poly and vinlyester though. Meaning, that if you gelcoat a boat in the mold, and then epoxy behind it, you have no dramas. The epoxy will dissolve the primary bond of the polyester and crosslink without problems at all. Go the other way, and build a boat out of epoxy and try to gelcoat it after the fact, and you will find that the anemic secondary bond characteristics of VE and PE resins coupled with the extraordinarily tight cross-linking of the epoxy will amount to the inability to adhere to it.

More on epoxy processes in the next segment...

 

[Froggystyle]

Epoxy resins are employed in many of the same ways as standard VE and PE processes... meaning, you can use them the same, but have far different results in most cases. We have already covered the strength gains if laminated properly, but this will illustrate what has to occur to actually see those gains.

Wet Lamination:It is difficult to wet laminate epoxy and get a high quality result. Gravity, a slow cure time, thin-ish consistency and long exotherm tend to make epoxy a very difficult media to use when wet-laminating all but horizontal panels. You will be "working" material for hours with epoxy trying to keep the material where it needs to be, and as anyone who has worked with wet lamination knows, any time you have to "work" the material, you risk messing it up... especially as you close on it kicking.

"Vacuum bagging": As mentioned earlier, for the most part people are snowing you in this industry regarding "vacuum bagging" and it is why I always put it in quotes. With a VE or PE resin, there just isn't time before it kicks to actually vacuum bag a part of any size to any expected result. The time to gel, even in perfect circumstances never exceeds 1.5 hours or so. The resin at that point has long since yelled "last call" and started exotherming itself. With the time it takes to add a vacuum bag, seal it and expect to do anything other than de-bulk the laminates if they are still even slightly viscous is absolutely minimal, and even as highly trained as my guys are, we can't 'bag anything bigger than an instrument panel effectively. Epoxy changes that.

With the slow kick time, epoxy allows you to have plenty of time to 'bag a part and get to it while it is still fluid. Vacuum's don't stop gravity however, so you will still see a drain of the part until it gets under bag, but the action of the vacuum bag pressing with the extraordinary 2,116 PSF will usually counter this for the most part. Even with epoxy, a long cure and proper lamination, the very best possible ratio with a wet lamination/vacuum bag application will yield 50% resin, 50% reinforcement. Way better than the 70% resin wet lamination process, but still a distant third place.

Many of the best epoxies need to be "post cured". The "thermosetting" aspect of certain lower strength epoxies can often be accomplished at room temperature... at least to start with. The epoxy itself will exotherm, creating heat and will cure on it's own. It will have a lot of the properties mentioned above, stick to damn near anything and will provide a very strong bond. Nowhere near as strong as post-cure style epoxies though.

With a post-cure epoxy, you laminate the part and then put it in an oven at usually around 220 degrees for several hours. This activates the catalyst and cures the part, providing what amounts to the very strongest possible structural FRP. This is the bomb. Unfortunately, there are massive side effects to the strength.

You have to vacuum bag. The heat makes the epoxy very, VERY viscous for a while, and anything not vacuumed will just end up in a pool at the bottom of the boat and your sides will be essentially dry. The best processes all utilize vacuum fortunately, and once you have gotten to the level of complexity required to switch to a post-cure epoxy substrate, you are probably already spooled up on vacuum bagging or infusion.

Huge transfer and shrinkage problems. If you think that the transfer issues in wet laminated vinylester are bad, you should see post-cured epoxy parts. The entire mold, cage, gelcoat, skincoat, outer laminates, core, inner laminates and structures are brought up to over 200 degrees for hours. They all expand at different linear rates, and to different degrees... which is fine because the epoxy is still fluid. The problem is on cooling...

They also all shrink at different rates. Core will go one way, laminates another, mold another and the steel cage yet another. The un-reinforced gelcoat is so on it's own program that it often doesn't pay to gel an epoxy part until after you are done and pop it, but gel doesn't stick to epoxy parts, remember... The shrinkage creates massive transfer issues, and results in a very poor surface finish. Which is fine if you plan on block sanding and top-coating after the fact, but us West Coast guys and buyers pretty much demand the gelcoat graphics that our side of the industry has become known for, which creates a real quality issue.

The easy answer is, unfortunately, to use a lower strength, non post-cure epoxy product to laminate with.

Resin Infusion: Resin infusion adapts very well to epoxy. In fact, depending on the style of epoxy, literally nothing in the process changes. We don't care how long it takes to cure (except for how long the core is exposed to any solvents in the resin such as styrene) and there are no problems with either drainage or pooling. The product is de-bulked before it sees the epoxy, so you fill it with a perfect amount of substrate and call it a day.

Resin infusion offsets the cost of epoxy: Since infusion yields a part that is only 30% substrate, you will use about 1/3 the resin of a wet lamination. This savings makes up a huge amount of the cost difference between a wet laminated VE and switching to epoxy. If you are already infusing though, it is still going to double the price of the substrate.

With a low resin volume, exotherm is limited. As mentioned before, the resin/epoxy gets hottest in volume, with smaller volumes not getting anywhere near as hot as pools of it. When you infuse, there are no pools or "hot spots" so it minimizes the effect of the exothermic heat/shrink/transfer issue.

Pre-Preg lamination: Mentioned already, pre-impregnated fibers (pre-preg for short) gives a near-perfect resin to fiber ratio of 30/70. Often, pre-preg carbon fibers are laminated with epoxy for strength and long kick times. When money, time, talent and reason are no object (military aerospace for example) this is the medium of choice for many.

Pre-Preg needs to be frozen: These laminates are pre-catalyzed, so they need to be kept frozen until use. You have a narrow working window before it starts to go sideways on you, and then you have to chuck the material.

Cannot have voids, period. The process usually involves pulling the laminate out of the cooler, laminating the part perfectly, tailoring closely to ensure zero voids (voids will drain the laminate of the perfect ratio, resulting in worst case scenario... dry spots) and applying a vacuum bag. The part, now 'bagged is put into an oven, essentially creating an autoclave as the part is in vacuum and being heated.

Quality control absolutely paramount: If quality control is aerospace level, uber-high quality parts are possible and are cranked out daily as a result. If QC isn't super strict, garbage comes out the door, as the process has more failure points than any other.


Epoxy infusion is a great process for hull construction when you need super high strength, you don't mind a lot of surface re-work for glass smooth finishes, money is no object and vinylester won't produce a strong enough or light enough part.

To answer the question I posed before of why we don't use epoxy... the answer is simple. We don't need to. Our process is 400% ahead of the industry right now. We are thousands of pounds lighter than the next competitive boat, twice as strong, eight times as rigid with a nearly indestructible hull under any type of condition that could be loosely considered normal use. It has rendered the Trident deckboat as the fastest boat on the water with a 550 or 700 Ilmor engine, even with a giant stereo and aerodynamically garbage deck configuration (compared with a canopied race style boat). We are beating the industry right now with hundreds of pounds of additional parts on board, and an even lighter availability of process tied behind our backs. Bottom line is, we can check off a box and switch to epoxy. We can build a boat with less stereo weight, and we can choose an exotic lamination reinforcement if we want to, and it doesn't change our process at all.

And in an industry when people are wet-laminating carbon fiber, "vacuum bagging" boats using VE resin and "infusing" boats using balsa cores, we are using results instead of buzzwords to prove our point.

Someday we will need to switch to epoxy to remain in front... but not this week.

 

[RiverDave]

My freakin brain hurts after reading that..

RD

 

[wsuwrhr]

My freakin brain hurts after reading that..

RD

Less coffee and cigarettes, more water and orange juice. See if that helps.

I have said to Wes and about Wes, he is very knowlegeable about the process and science of his craft.

I like chatting with him, hanging out and being part of the "vision."

Brian

 

[maxwedge]

Very intersesting read. Thanks for taking the time to post it.

 

[Roger 1]

Thanks for taking time to post all of this to share with us. It has confirmed some of my ideas, concepts and ''suspicions'' that I have had for a long time as well as enlightend me a great deal. I read the whole thing in its entirety and don't believe that I blinked but a few times and never yawned once!
Thanks again for sharing the time and wisdom.

Roger Holmberg

 

[Gelcoater]

very cool,i have been in this industry for 21years,its about time some one came cleen about all the hype on carbon/kevlar lay up and its proper use and application. hopefully future buyers read and understand all the info contained. i dont claim to know evry thing about f.r.p. layup but evry thing u said is dead on. i have seen lots of people spend LOTS of money on carbon inlays,kevlar layers in layup etc. and have to bite my tongue. thanks for telling all what an employee [not in sales] cant,hope they read it!

 

[vdcruiser]

I just joined this forum, and that was a very interesting and informative read. Thank you.
I do have a question though. What is the best resin/process to use for structural repair on a standard laminate polyester hull ?

 

[riverman140]

Alot of VERY usefull information.. i do admit your thread kicked my ass. thanks for the great information

 

[420HOA]

Great read, great info, Thanks "V-Drive Row":thumbsup

 

[Froggystyle]

I just joined this forum, and that was a very interesting and informative read. Thank you.
I do have a question though. What is the best resin/process to use for structural repair on a standard laminate polyester hull ?

Sorry I lagged getting back to this... the thread was from a little while back.

You want to make sure that if you have a standard PE hull, you are going to want to repair with a similar or at least compatible product.

The challenge to "upgrading" your resin to something higher performance is that the rest of the boat is still the same. Flex characteristics, gelcoat adhesion, porosity and myriad other considerations come into play, and for anything other than a small internal repair, could come back to haunt you some day as you create a new "stiff" portion of the boat hull.

For repairs on a PE hull, I would use a high quality PE (Polyester) resin like a Reichold or Hexion. I used Composites One as a supplier, and they are nationwide, so you could get it from several different sources. Something with good chemistry, minimal inert fillers and low exothermic temperature when kicking would be at my forefront. Make sure you do a "cup test" before laying the real deal down so you can verify time to gel on that day with that catalyst.

That said, you can really use almost anything on a PE hull. It will accept Vinylester as well as epoxy, so you could use whatever is handy for a small enough repair.

On several huge infusion repairs we did, I used epoxy for it's strength in primary bond, and it's willingness to bond with the existing laminates well. The spot was well reinforced, and I didn't see any drawback to using the higher quality epoxy.

Hope this helps.

 

[Gelcoater]

When you do the cup test,I think its important to do a test in a simular thickness level.In a cup it will kick much faster than it would in normal use. I would get a big piece of cardboard and wet out some matt on it,about a foot or so square taking notes of resin volume and catylist volume.Roll it out and wait. If humidity and temp are the same when you do the job,you will know how long you have to work it.

 

[Froggystyle]

When you do the cup test,I think its important to do a test in a simular thickness level.In a cup it will kick much faster than it would in normal use. I would get a big piece of cardboard and wet out some matt on it,about a foot or so square taking notes of resin volume and catylist volume.Roll it out and wait. If humidity and temp are the same when you do the job,you will know how long you have to work it.

For sure. Absolutely for sure... but the cup test will give you a great "no less than" timing, something a lot of beginners could really use.

Once that bell goes off, stop messing with it and get to cleaning up, or lose your tools.

Most importantly is to do the test to make sure your resin and catalyst work together.

I had a situation once where a laminator used my infusion catalyst instead of HP90 on non-infusion resin. Ooops. It kicked, but over the period of a couple of days. We blew the part just in case and didn't use it, but it was a lesson learned regarding not only checking for time, but for compatibility and effect.

Another thing we did was we promoted all of our own resin to keep a close eye on shelf life and Cobalt. Someone used non-promoted resin for a speaker box once, and again, took more than double the time to kick. Fortunately, it was non-critical and wasn't a wasted part, but we learned early on to cup test literally everything getting shot.

 

[Gelcoater]

I am sorry to say I have done worse.:grumble:I sprayed a deck with an airless system(that i talked them into buying) and didn't check to see it was pumping catylist at the head after prime and sprayed the whole thing with 0 catylist:skull The line was kinked:swearI didnt even know for 45 minutes.It pulled A+ lines every where,no sags,perfect layer. At about 40 minutes it haddent kicked @2.5% and I knew something was wrong,checked the gun, and knew I was screwed.

Now its one thing to screw up a paint job,but it gets worse. We decide to spray a good hot coat down on top to see if it will get the soft stuff to kick. Well it did for the most part,there were a few patches here and there that were wet spots on the mold,but it gets worse:grumbleown in the gunnels it did this strange creep/buckle/shift and printed the creep/buckle/shift pattern in the mold.

I felt like such a dick,I was sure Jeff(Camire) was either going to fire me or kick my ass or both right there. So we had to acetone the rest of the wet spots off,wet sand the print out, and do the multi coat waxing ritual.We did take the time to touch up the couple little cut marks and little divits that add up on any high use mold to make the deck cherry. It was one of those nightmare days you wish you would wake up,because you just cant believe its happening.Let just say that mistake has not been made again.

 

[vdcruiser]

Thanks for the comments about making repairs, I had to repair some cracks around my strut caused from throwing a prop blade, and wondered what type resin would make the strongest repair. Some good tips here about where/how to get the resin. Its so tempting to just get it from Home Depot/Lowes, etc.
Its comforting to know that even the "pros" have screw up sometimes.

 

[Gelcoater]

To error is human As far as im concerned,thats how one becomes a pro,doing,learning from mistakes,and always looking for a way to make what ever "it" is even better. Im willing to bet Froggy's laminator (if he had a job after) never used the wrong catylist again too.

 

[DragDad]

I read the epoxy portion of this and came to the conclusion that it holds value in boat building only in structural elements that can be controlled for quality, while the Polyester and Vinyl Ester products work better for the visible exteriors of the vessel. For instance, if one wished to design and build a "no wood" hull, they could tape and shoot the gelcoat, lay up primary skin and incorporate an epoxy frame into the cured skin. The only problem exists in the order in which you install the epoxy structural elements, as poly and vinyl esters do not want to adhere to the epoxy, but the epoxy likes adhering to the poly and vinyl ester materials.

hmmmmm

Leaves me wondering if epoxies have a place in boat building. I dont know. I know they work amzingly well for repairing holes and the like.

 

[hallett21]

We have covered the principal known as "primary bond"... which is the bond that resin makes with itself as it is curing. We talked about the exothermic heat created as they all move into place and become rigid, and we discussed how a high quality vinyl-ester resin is very complete in it's cross linking process... such that there isn't many sockets left when completely cured, and not many plugs either, to use my prior metaphor...

When a bucket of catalyzed resin kicks off and becomes hard, from a physics level it becomes essentially a single large molecule. It all kicks uniformly, and all hardens at the same time.

When you have one of these molecules, and you wish to join it with another one you are creating (laminating another layer into a boat for example) you are counting on a principal called "secondary bond".

Each resin you choose when engineering has different physcial properties. In our case, our naval architect hired a composites engineer to decide not just our lamination schedule, but the actual materials we were going to use in each case. Many of the "physicals" of the resins are strong enough across the board to do the job, but it really takes a Mechanical Engineer (M.E.) to begin to discern how to optimize the laminate. One of the properties is it's secondary bond characteristic, which is to say how well it will stick to itself once it is cured.

The strongest resins are the tightest molecules and kick most completely. This is a negative when it comes to secondary bond however. You have a stronger initial resin, but the joint where the next layer bonds to the original is weak in comparison.

GP resin, while the weakest physcially of what we have discussed actually has a strong secondary bond because of all of the non cross-linked resin and catalyst parts.

You see the one side is already hard. It can't move at all. When you apply a new batch of catalyzed resin, it struggles to find a place to bond at the molecular level. With all of the seats taken up, it ends up just bonding to itself, and only peripherally to the other part.

You can physically break up the molcules by sanding with aggressive grit paper and roughing the surface, but you are only creating a spot for it to bond to that is as deep as you sanded.... meaning... not very deep. If you are going to count on a surface bond like this, you need to support the part physically in some other manner... like a bulkhead or gusset to spread out the force.

Whenever fiberglass is repaired, you run into this problem. Whenever you patch in something in fiberglass you have the problem. What you create is two strong parts with a weak bond between them.

To liken it to a more familiar process, imagine bolting two pieces of metal together. Each piece of metal is strong, and if you pull them apart, generally the bolt will break, not the metal. Same deal. Plenty of things are bolted together in our world, but you need to be conscious in composite engineering that you have a weak spot in between strong parts.

When you lay up a boat do you "race" to get all of the layers of glass in at once? Or do you lay a layer then sand and continue onto the next layer?

Could you also elaborate on Infusion. Your threads have been great!!!!:thumbsup

 

[Froggystyle]

When you lay up a boat do you "race" to get all of the layers of glass in at once? Or do you lay a layer then sand and continue onto the next layer?

Could you also elaborate on Infusion. Your threads have been great!!!!:thumbsup

Sorry for the lag in getting back to you... I don't check this much.

When we laid up a boat, it was all dry, and you infuse in one shot, so there is no racing for anything.

Frankly, I don't know how anyone is "vacuum bagging" something the size of a boat without doing it in sections, which seems to defeat the original idea in the first place. I imagine you would have to race your ass off to try to get it all done, bagged and vacuumed before it kicked...

 

[NAFLASH]

This is great stuff you are posting and it is all spot on!

 

[hallett21]

Sorry for the lag in getting back to you... I don't check this much.

When we laid up a boat, it was all dry, and you infuse in one shot, so there is no racing for anything.

Frankly, I don't know how anyone is "vacuum bagging" something the size of a boat without doing it in sections, which seems to defeat the original idea in the first place. I imagine you would have to race your ass off to try to get it all done, bagged and vacuumed before it kicked...

So when you infuse do you have a special machine to do so? And I think you said it was stronger than a wet layup correct? How about versus kevlar? Does infusing take more or less time than a traditional lay up? Seems like everyone should be doing this these days.

 

[Gelcoater]

So when you infuse do you have a special machine to do so? And I think you said it was stronger than a wet layup correct? How about versus kevlar? Does infusing take more or less time than a traditional lay up? Seems like everyone should be doing this these days.

Machines,(plural He makes it sound easier than it might actually be,kinda like tooling a boat from scratch. He is however,a grat source of knowhow once you get there.

Kevlar

 

[Luv2gofast]

Wow!! Great writing. I wish school was like that...I would have done much better. You did a great job of explaining very complicated processes and materials in a simple way. I need to learn more about the "infusion" process in FRP. It sounds like a huge advancement over wet lay up although out of reach for the average guy. Most of my experience in FRP is racecar body repairs. I see several things I am doing wrong after reading this. I'm sure my next repair will be much better...thank you.

 

[jrork]

Wow, whar a great thread. Thanks for taking the time to put this down. How about some discussion on fabrics? The selection out there is mind boggling

Thanks again......john

 

[Rickybobby]

Awesome, read, thanks for taking the time to share with us. Newbie question concerning hull "layups". I have heard about "light layups" and "heavy layups" is this some sort of measurement or number of "layers" of cloth/resin used in the construction of the hull ???

I know in surfboards, sometimes a "heavier" cloth is used (6oz vs 12oz) Does it really matter what "ounce" cloth is used when it comes to making repairs on an existing older hull ???

thanks