Peeled the Hull

[Loren Beach]

Enough Helpers, Right Tools, Planning....

That seems like a lot of thickness you will build up. FYI I used three layers of 1708 biaxial fabric when I recored the deck to replace the top skin. And I probably only needed two. You might get a sample of the material and experiment with it before you purchase enough to cover the entire bottom three times! The stuff soaks up a lot of epoxy too and is a real pain to wet out unless the temps are nice and warm, and then you don't have much time to install it before the epoxy kicks. You'll probably want the slowest hardener available (West Tropical) if you are working when the temps are warm. And some helpers to mix and spread the massive amounts of epoxy! Good luck and keep us posted. I will be interested to see what techniques will work best for you. Too bad you can't flip the boat over and work on it upside down!

Good Advice to have some helpers for the application. A friend of mine did a bottom strip of his C&C 34 and got into the laminate in many places. They set up a production line, as it were, to do the epoxy and biax. I believe that there may have been four people at the height of the effort. Two minimum. Batches of epoxy mixed, precut cloth/biax laid out on tables, grooved rollers, plastic spreaders, etc.
Everyone in tyvec suits and face shields...
The result was beautiful, but there were several weekends of dawn to dusk labor for the crew.

Loren

 

[PDX]

That seems like a lot of thickness you will build up. FYI I used three layers of 1708 biaxial fabric when I recored the deck to replace the top skin. And I probably only needed two. You might get a sample of the material and experiment with it before you purchase enough to cover the entire bottom three times! The stuff soaks up a lot of epoxy too and is a real pain to wet out unless the temps are nice and warm, and then you don't have much time to install it before the epoxy kicks. You'll probably want the slowest hardener available (West Tropical) if you are working when the temps are warm. And some helpers to mix and spread the massive amounts of epoxy! Good luck and keep us posted. I will be interested to see what techniques will work best for you. Too bad you can't flip the boat over and work on it upside down!

1708 has a lower layer consisting of mat and upper layer of 1700 biax, so make sure it is epoxy compatible. Soaking up a lot of epoxy is definitely true. It has a tendency to dry out if you don't thicken the epoxy with cabosil (unless the temperature is perfect and it goes off soon after you lay it up. Cabosil will also help hold the glass in place when you are working upside down. If it were me I would go with something lighter and easier to use, like either plain 1700 or even a ten ounce biax.

 

[Roger]

I spoke with Tom Pollock at GB and he suggested going back with 3 layers of 1708 Biaxial this would just about replace the material removed. I'll start a new thread when I get to the point of reglassing the hull.
Robert

I'd stick with a cloth or knitted 0/90 biaxial. Besides the issues already discussed with the 1708 (epoxy compatibility of mat, added weight), I don't think it's the best choice structurally. The "17" component is a 17 oz. biaxial glass oriented at +/-45 degrees on the roll. You should use a 0/90 material to align with the rest of the hull laminate. Just my $.02.

-Roger

 

[Bob Hunt]

Another perspective and method...

Since this is my first post on this site I'll probably make some mistakes. Please bear with me.

I've been involved with fiberglass repair at the professional level for more than 20 years. I learned the trade from Dave Lenox. While I'm not a professional fiberglass repairer I've done quite a bit of it. I'm a friend of Mark Lenox, an outstanding repairman here on Maryland's Eastern Shore, and I'm in his shop several times a month.

The point is this: In 1982, Dave Lenox developed a method to prevent moisture permeation into failed fiberglass laminate and the subsequent possibility of blister formation. His method is based on Interplastic's CoRezyn VE-8117 vinyl ester resin. CoRezyn begins as an epoxy resin that is modified to perform like a polyester resin. But it has physical characteristics that are equal or superior to West System's 105/205 epoxy resin.

In 1990, I performed a bottom job at the Lenox shop on my 28-foot sloop using Dave's method. I've also observed many other boats being repaired, including several constructed with Hetron, an infamous fire-retardant resin that caused the worst case of blisters in maritime history.

The Lenox system uses only six components. They are: VE-8117 resin; Hi-Point 90 MEKP catalyst; 1.5-oz. mat; 1808 biaxial fabric; Cab-O-Sil TS-720 treated fumed silica (which is hydrophobic); and Cook's sanding gel coat (NPG ISO).

The occurrence of water permeation and blister formation has declined since boat builders began using vinyl ester resin to saturate the veil layer of mat just beneath the polyester gelcoat (NPG ISO). The Lenox repair method results in the same structure but it's formed in reverse order. Regardless of the particulars of a repair, they are all finished with one layer of 1.5-oz. CSM, that is saturated with CoRezyn VE-8117, and polyester gelcoat (NPG ISO)as shown in the photograph of my boat. As Dave used to say, "It's the resin that keeps the water out."

Hope this information is helpful. Bob Hunt

 

[Bob Hunt]

Hello All,

I decided to have the hull peeled on my 36 RH hopefully this will remedy the blister problem. Phil Turner came to my house and did 2 passes each about 70/1000 of an inch. I'm going to have to go back with some type of cloth and I believe I'll use West System epoxy instead of a polyester resin. What about the type of cloths and the order they should be layed? I would appreciate any feedback.



Thanks,

Robert

Robert,

The thickness of 1.5 oz. CSM after the resin has polymerized is about 0.040". You'll need to sand the peeled surface with 36 grit to make it fair and produce a rougher surface than the peeler left. You should use mat for the initial bonding layer to the formerly peeled surface that you sanded. Use a serrated roller to distribute the resin into the mat and mold it to the prepared surface. Then finish with another layer of the 1.5 oz. mat and several applications of pure resin. This should result in a final laminate thickness of 0.090"-0.100"

Cloth is not suitable for the initial bonding layer because it holds so little resin that it tends to delaminate. Biaxial cloth has a layer of mat, reportedly 0.75 oz. but it looks more like 0.25 oz., that is much too thin. Furthermore, cloth and bias don't hold enough resin to provide an effective barrier to water permeation.

Many modern boats are constructed with CSM and vinyl ester resin in the veil layer just inside the external gel coat. And this type of veil layer has been shown to be very effective in keeping the water out. Why not do what has been shown to work?

Hope this helps. Bob Hunt

 

[PDX]

A few comments

If you're having a yard do the work, and they want to use vinylester, go for it. Yards in my experience like to use polyester/vinylester. For them, its easier. Once they get a feel for the right amount of catalyst they can mix it hot and keep going, laying on several coats in fairly quick succession. Vinylester has a good reputation for water proofing and hence blister resistance. And they will need to use mat with polyester or vinylester, particularly vinylester because it has much less viscosity than either polyester or epoxy and the mat holds a lot more resin as was mentioned.

If I were going to do such a job myself, I would use epoxy. I have used polyester and, for me, it was easier to get a consistent mix with epoxy. It doesn't smell. Or at least it doesn't smell like polyester. Vinylester is also dissolved in styrene so I assume it smells the same. The process takes longer with epoxy. You have to wait for the various coats to tack up or, especially if working overhead, they will all fall off. Finally, there is a larger margin for error with a DIY job with expoxy because it has superior strength and bonding characteristics, and this is a secondary bond, http://www.redrockstore.com/resin.htm

 

[Bob Hunt]

Finally, there is a larger margin for error with a DIY job with expoxy because it has superior strength and bonding characteristics, and this is a secondary bond, http://www.redrockstore.com/resin.htm

<center style="color: rgb(0, 0, 0); font-family: Times; font-size: medium; ">[SIZE=+1]
Comparison of Clear Casting Properties[/SIZE]</center><center style="color: rgb(0, 0, 0); font-family: Times; font-size: medium; ">

	<center>CoREZYN</center><center>VE 8117 & VE 8121</center>	<center>WEST SYSTEM</center><center>105/205</center>	<center>WEST SYSTEM</center><center>105/206</center>	<center> MAS</center><center>Slow Hardener</center>	<center> MAS</center><center>Medium Hardener</center>	<center> MAS</center><center>Fast Hardener</center>
Tensile Strength, psi	<center>11,600</center>	<center>7,850</center>	<center>7,300</center>	<center> 8,000</center>	<center> 7,350</center>	<center> 6,700</center>
Tensile Modulus, psi	<center>470,000</center>	<center>408,000</center>	<center>460,000</center>	<center> 390,000</center>	<center> 395,000</center>	<center> 390,000</center>
Tensile Elongation, %	<center>5.0</center>	<center>3.4</center>	<center>4.5</center>	<center> 9.0</center>	<center> 8.0</center>	<center> 8.0</center>
Flexural Strength, psi	<center>19,400</center>	<center>14,100</center>	<center>11,800</center>	<center> 14,600</center>	<center>Not listed</center>	<center> 15,900</center>
Flexural Modulus, psi	<center>450,000</center>	<center>461,000</center>	<center>450,000</center>	<center> 535,000</center>	<center> Not listed</center>	<center> 355,000</center>

<tbody>
</tbody>

</center>
The table shows data that are the results of ASTM standardized tests. With respect to tensile strength, these data show that the CoREZYN vinyl ester resins are 48% stronger than the West System 105/205 epoxy resin. With respect to flexural strength, the vinyl ester resins are 38% stronger than West's 105/205 epoxy resin.

I rest my case. Bob Hunt

 

[Guy Stevens]

That table has nothing what so ever to do with the project at hand.

The tensile strength reported here is the Clear Casting strength, the strength of the material without any reinforcing material such as fiberglass.

These tests also do not in any way address the secondary bonding characteristics of the materials in question.

I am confused as to why you think this table makes a case for vinyl-ester based repair. The table has nothing to do with the discussion at hand. If you look at the studies of secondary bonding of polyester vs vinyl-ester vs epoxy the epoxy comes out far ahead, (frequently surpassing the strength of the original material).

The other issue here is the permeability of the material to water. Epoxy has a higher rejection of water than ester based resins in all of the tests that I have seen or even heard of.

If you are doing production or setting up a business to do a lot of boats, vinyl-ester will cost between 1/2 and 3/4 of the cost of a high quality epoxy. Vinyl-ester is better than polyester at water rejection, so a job done with vinyl-ester if done correctly can keep blisters from coming back. Key in this is preparation and correct mixing of MEK and the elimination of contaminants throughout the job. Is it as good as epoxy, no. There are plenty of cases of the vinylester solutions failing, sometimes multiple times. Vinyl-ester is easier to apply, easier to sand, a cheaper product, and therefore a lot less expensive a process to both sell to the customer and to make a bigger mark up on.

Steve makes a good case for most things here. http://www.smithandcompany.org/GRP/GRP.html

I don't agree on everything that he does and I feel he misses a key step in the process which is washing the bottom while drying out in order to remove the chemical salts that are a cause in the first place. He feels that the cause is more from the capillary action of minute strands of fiberglass. I have read and seen it caused more often from incorrect mixing of polyester, and contaminated conditions during the layup. He uses penetrating epoxy because it is much much easier to apply than straight epoxy for the first few coats. (Remember that penetrating epoxy is epoxy that has been thinned with solvents to reduce it's viscosity). I like to use regular epoxy with a barrier coat additive from West, but it is not the easiest thing to apply. Sanding it is also difficult simply because of the hardness of the product.

In applying your new cloth drop me a PM (as it is going to be a long discussion back and forth), I have a trick that is amazing. It will probably save you a months worth of work getting the laminate back on.

My $.02

Guy

 

[PDX]

"Comparison of Clear Casting Properties?" What exactly does that mean? Is that a comparison of various dried globules of resin, without any kind of glass lamination? It might be helpful if you had linked the study or at least explained its methodology. I tried to google it and couldn't find it.

I thought the problem this thread was supposed to be addressing had to do with laminated layups. And isn't bonding strength (omitted in your study) the most important criteria for someone doing a secondary bond which is essentially what laying up over a blister repair is?

Here is a link to a study done by the US Navy.

http://www.usna.edu/Users/naome/phmiller/ASNEpaperC.pdf

It concerns their experimentation with a variety of combinations of resins and glass layup schedules. The resins include polyester, vinylester, and epoxy. The core material is the same--airex. Check out the graphs at Figure 1, page 4. This is their summary showing cost, weight, and strength as a "normalized value" for all of the different resin and layup combinations. The epoxy combinations got the highest numeric strength ratings--not across the board, although four of six of the epoxy combinations were stronger than the strongest vinylester, and three of them were considerably stronger.

 

[Bob Hunt]

The tensile strength reported here is the Clear Casting strength, the strength of the material without any reinforcing material such as fiberglass.

These tests also do not in any way address the secondary bonding characteristics of the materials in question.

I am confused as to why you think this table makes a case for vinyl-ester based repair. The table has nothing to do with the discussion at hand. If you look at the studies of secondary bonding of polyester vs vinyl-ester vs epoxy the epoxy comes out far ahead, (frequently surpassing the strength of the original material).

The other issue here is the permeability of the material to water. Epoxy has a higher rejection of water than ester based resins in all of the tests that I have seen or even heard of.

If you are doing production or setting up a business to do a lot of boats, vinyl-ester will cost between 1/2 and 3/4 of the cost of a high quality epoxy. Vinyl-ester is better than polyester at water rejection, so a job done with vinyl-ester if done correctly can keep blisters from coming back. Key in this is preparation and correct mixing of MEK and the elimination of contaminants throughout the job. Is it as good as epoxy, no. There are plenty of cases of the vinylester solutions failing, sometimes multiple times. Vinyl-ester is easier to apply, easier to sand, a cheaper product, and therefore a lot less expensive a process to both sell to the customer and to make a bigger mark up on.

Steve makes a good case for most things here. http://www.smithandcompany.org/GRP/GRP.html

I don't agree on everything that he does and I feel he misses a key step in the process which is washing the bottom while drying out in order to remove the chemical salts that are a cause in the first place. He feels that the cause is more from the capillary action of minute strands of fiberglass. I have read and seen it caused more often from incorrect mixing of polyester, and contaminated conditions during the layup. He uses penetrating epoxy because it is much much easier to apply than straight epoxy for the first few coats. (Remember that penetrating epoxy is epoxy that has been thinned with solvents to reduce it's viscosity). I like to use regular epoxy with a barrier coat additive from West, but it is not the easiest thing to apply. Sanding it is also difficult simply because of the hardness of the product.

In applying your new cloth drop me a PM (as it is going to be a long discussion back and forth), I have a trick that is amazing. It will probably save you a months worth of work getting the laminate back on.

My $.02

Guy

Here's why the relative strength of clear castings of various resins is important:

1. weak resin + fiberglass = weak laminate
2. strong resin + fiberglass = strong laminate

It's as simple as that.

 

[Bob Hunt]

"Comparison of Clear Casting Properties?" What exactly does that mean? Is that a comparison of various dried globules of resin, without any kind of glass lamination? It might be helpful if you had linked the study or at least explained its methodology. I tried to google it and couldn't find it.

I thought the problem this thread was supposed to be addressing had to do with laminated layups. And isn't bonding strength (omitted in your study) the most important criteria for someone doing a secondary bond which is essentially what laying up over a blister repair is?

Here is a link to a study done by the US Navy.

http://www.usna.edu/Users/naome/phmiller/ASNEpaperC.pdf

It concerns their experimentation with a variety of combinations of resins and glass layup schedules. The resins include polyester, vinylester, and epoxy. The core material is the same--airex. Check out the graphs at Figure 1, page 4. This is their summary showing cost, weight, and strength as a "normalized value" for all of the different resin and layup combinations. The epoxy combinations got the highest numeric strength ratings--not across the board, although four of six of the epoxy combinations were stronger than the strongest vinylester, and three of them were considerably stronger.

The Navy study omits many significant details and is not very applicable to restoring a peeled hull because:
1. the panels were cored
2. the panels were post-cured at 140* F. for eight hours.

However, the study does state that the resin chosen to construct the boats in the 1980s was CoREZYN 8117, the vinyl ester resin I recommended and have used for 22 years. West System's 105/205 epoxy resin was apparently not chosen.

 

[Guy Stevens]

Secondary bonding......

The question still is secondary bonding characteristics.

Vinyl-ester is a poor secondary bond and is less of a hydro block than epoxy. So for this project it is not the best solution, we are not looking at ultimate strength here, the boat already has a hull. Was it weakened by the aggressive peel? Yes it seems to have been. The removed section of the layup schedule could be replaced with either polyester, vinyl-ester, or epoxy.

The issue is not ultimate strength alone, since the new layup will have to bond with the already cured polyester and have a superior water rejection properties. The best secondary bond is epoxy, and the best water rejection is an epoxy barrier coat.

In this application I also would not recommend West for the build out of the layers. It can work wonderfully, but there are better epoxy compounds for this that result in less work. I would use West in the barrier coat and fairing layers however.

Guy

 

[Guy Stevens]

Faulty Logic

Here's why the relative strength of clear castings of various resins is important:

1. weak resin + fiberglass = weak laminate
2. strong resin + fiberglass = strong laminate

It's as simple as that.

Nope, that is not what the table tells us. The strength of composite materials is dependent on the complete construction of those materials. Not the strength of the individual components of the materials added together. This is true of all composite materials.

The clear casting strength tells us nothing about the structural strength of the assembled components of the composite material. The properties of the composite materials are not easily solved by adding the strength of the individual materials together.

The Navy study does try to show us that in general the strength of the composite materials using epoxy exceed those using the vinyl-ester layups. The study also deals poorly with a lot of variables, which they state but don't test or deal with well. It is a flawed study, useful for their purposes, not really useful for our project under discussion.

The choice of the materials used to build the vessels was not based solely on the strength or physical characteristics of the materials in question. Cost, ease of construction, ease of fairing and painting as the hulls were to be painted, were considerations that were highly weighted and discussed in the study. Neither the Navy study, or the (Bob Hunt's) table have anything to do with the project of repairing the Ericson in question.

Bob has seemingly had good results in having a boat he owned repaired with similar, but not identical, issues using a yard that favored the use of Vinyl-ester compounds in their solution to the problem. Indeed if I owned a yard that did this type of repairs I believe I would be forced to use this method if I wished to be competitive or a cost effective solution for my clients. This is based on the cost of materials, and even more the cost of labor. (Which was probably the only part of the Navy study that does apply to the project at hand.)

However if I were fixing a boat for personal use, or assisting one of my clients in repairing their own boat, I would use an epoxy based solution.

Guy