Vespera Hull-Bottom, Hydrolysis in Outer Laminate, 1987, 51 foot cutter

Below Vespera’s water line the entire gelcoat surface was star cracked. These gelcoat cracks resembled a shattered car windshield or a spider web. The gelcoat, checker pieces ranged in size from a few square inches to ½ square inch. Although the gelcoat was badly star cracked no blisters were present. Because no blisters were visible and because moisture meter readings of the hull showed low moisture levels, previous surveys missed the problem. Unfortunately I discounted the star cracks as a coating issue. Later the estimate I received to cure the problem was over $30k. I found this out after I bought the boat.

How could I have missed such a visible problem? Before I bought Vespera the boat was surveyed and I contacted 2 boat yards plus original manufacturer about the star cracked hull. In addition I had years of boat restoration experience. Because star cracks are unusual, no one saw the problem. The boat manufacturer sort of listened a little and did not say much. One of the yards told me to test the gelcoat to see how thick it was. They had experience with older boats having gelcoat over 1/8 inch thick that cracked. They suggested that polyester resin, itself, without structural fibers lacked strength and was likely to crack. The second yard that I contacted was in Canada where boats like mine were more common. They had past experience with European boats similar to Vespera in age, size and manufacturer. And they had worked with the star crack problems. They felt that I could cover the existing gelcoat with a good barrier coat. Another expert told me that many boat manufactures used bad resin in the 70’s and 80’s because of soaring resin costs and that all sorts of problems were now showing up. However, he would not offer a cure without seeing the boat and I did not have that done. Other than the surveyor none of the experienced yards saw my boat and that was probably my mistake. I was completely surprised by the $30k cure that I was about to run into.

Luckily I dug into the star crack problem further before I started applying a barrier coat. I was reluctant to cover the cracks with a thick barrier coat because of the most fundamental lesson learned from Allan Vaitses, that is when two materials are bonded together that contract and expand at different rates, the bond will eventually shear OR the stronger material will break the weaker. Common sense told me that unless the barrier coating was stronger than the underlying cracked gelcoat, the gelcoat cracks would come through the barrier coat. The question was how deep these cracks went? Were they deep Teutonic plates moving around or just superficial crazing?

To determine the depth of the cracks I started grinding off the gelcoat in several test areas and to my dismay I found that the cracks went through the gelcoat with stain lines through the first two layers of mat on the hull. In other words the cracks affected the hull up to the first layer of structural roving. Under the gelcoat some of the mat looked snowy white as if it just came off the roll. It was hardly wetted out. Had the resin been dissolved from hydrolysis or was the resin never applied (poorly wetted) at the factory? We’ll never know. What I did know was that I had a 50’ boat that had to have all the gelcoat and first two layers of mat removed then re-built, re-faired and recoated. The only local yard that did restoration work on this scale was in Superior, WI near Duluth. They said that the repair cost would start at about $30k and that it could cost much more if the problems ran into deeper laminate layers.

Incidentally, I also found out that Alan Vaitses was right. I found that the hull already had an epoxy barrier coat applied and the cracks came through the barrier coat.

The next question was how to cure the problem. What I wanted was a solution that would last the life of the boat. The cure that I decided on was to grind off the bad laminate and build a new thin epoxy hull over the original polyester hull. This new skin would consist of 2 layers of 10-ounce glass cloth and West Epoxy. This would be covered with 6 coats of Interprotect 3000 and 1 coat of 2000 to finish the new hull.

How I decided on this solution and the pros and cons that were revealed made for an interesting journey. To research the problem I went to boat repair manuals, a surveyor and a two boat yard that had solid experience in hydrolysis restoration projects. What I found was that there is a big difference between the people that have book learning and the people that have hands on experience. A text book or a book taught authority will tell you to remove 100% of the milky looking (hydrolyzed) fiber glass down to the dark (un-hydrolyzed) layer below. This may require cutting large holes in the hull. The big problem with this, ideal, solution is that you might not have much of a boat left when the excavation is done. Hull construction is not uniform and hydrolysis is not uniform. Some layers are wetted out well and free of hydrolysis while other layers are delaminated in pockets. True, with spot grinding and a saw we could remove every sliver of poorly wetted laminate but your hull may need to be rebuilt in many places where the hydrolysis was not really that bad. In other words the cure might be far, far more destructive than the disease.

The issue of fairing the hull became a larger and larger issue as I explored the problem. Fairing is your enemy. Fairing accounts for about ½ the cost of the repair. Also the more fairing material you use the less likely the repair will last. The more cavities that you grind out, the more restoration and the more fairing is required. Likewise the more lumpy fiberglass you add to the hull the more fairing will be required. Imagine smashing up a 50-foot car fender and bringing it to a body shop to have it straightened. It takes 2 men working full time, several weeks with air files to fair a 50-foot hull below the water line. Fairing is destructive and expensive. You put on a bunch of expensive waterproof material that you grind off. Fairing results in thickness variations in the laminate repair and a mixture of dissimilar materials. Fairing compounds have fillers that enable sanding. Fairing materials are more porous and have less structural strength than laminate.

Ideally you want to do the least amount of fairing and use the least amount of fairing materials. But ideally you want to gouge out the hull down to sound laminate before restoring it. In other words you have competing goals. One goal is to grind out the suspicious laminate but the more you grind the more you will need to rebuild and re-fair. So what is a healthy balance between excavating down to sound laminate and saving laminate? To answer this we need a definition of sound laminate? Does the laminate need to look uniformly dark?

After collecting opinions and weighing arguments, I believe that sound laminate is simply laminate that does not retain moisture. Forget about how the laminate looks. If the laminate can be dried out and the laminate does not absorb water from the air after the drying process is complete, then the laminate can be successfully covered. Conversely, if the laminate absorbs moisture from the air it is bad laminate no matter how good it looks. It is outside the scope of this overview to go through all of the arguments that brought me to this conclusion. Also, the reader should know that not all authorities agree with this conclusion.

To determine if the hull is dry enough, check the moisture reading difference above and below the water line. A 2% difference is acceptable. Some hulls absorb moisture from the air after they are tent dried. If your laminate stays dry you are good to go. If it absorbs a lot of moisture back from the air you may have to start cutting holes in the hull with a Sawsall.

Because fairing is destructive to new laminate I choose to fair out the original hull BEFORE covering it with new laminate. This is the opposite of the traditional restoration method. Traditionally the hull is covered with new fiberglass layers and then faired because it is very difficult to add new laminate and maintain the smoothness. For light fairing I used West epoxy mixed with micro-balloons designed for 100% submersion. For the spots where I had to gouge the hull, I used Awlfair. Note, no roving had to be destroyed. In other words, the structural strength of the hull was not affected because only the outer layers of mat had to be removed. In Vespera’s case the roving is bright yellow Kevlar so it is very easy to see if you grind into the roving fibers.

Before I started grinding off the gelcoat and mat I had the bottom sand blasted to remove several layers of bottom paint. This got the hull stripped down to the gelcoat. I tried having the sand blaster take off the gelcoat also but this was not possible. The gelcoat was unusually hard and thick. Because the gelcoat resin was harder than the laminate underneath, the sand blaster needed to use a very aggressive pressure setting to bite through it. This proved too destructive to the underlying laminate. I ended up grinding off the gelcoat by hand using 24 grit, 8” grinding discs on a 2000-rpm automotive body grinder. This is a long, hard, messy job. It also requires the right hand motion. Start slowly and train yourself. The 2000 rpm grinder can do a lot of damage if you are not careful. The trick is to keep the grinder moving constantly with a wide sweeping motion. You will be in good physical condition when you are done.

Next I choose to cover my hull with two layers of 10 oz cloth and epoxy resin. Why should the hull be covered with any additional fiberglass since no roving (structural fiber glass) was destroyed? Because what caused the hydrolysis was controversial, it seemed like good insurance to add laminate layers that had better water barrier properties (epoxy) AND structural strength rather than just a coating. The next question is why use fiber glass cloth instead of mat? Fiberglass cloth is the easiest material to keep fair, can conform to compound curves and works well with epoxy resin. Fiber glass cloth has no binders that require solvents in the resin to dissolve them. Why epoxy resin instead of vinyl ester resin? Some hands-on experts (not all) agree that the best bond to an existing polyester laminate is made using epoxy resin. Also epoxy is the best water barrier.

After I faired the hull and choose to cover it with new laminate the next problem was how to cover the hull and keep the hull fair. This may sound simple but as anyone that works with fiberglass knows, it is very difficult. To build a new, fair laminate each layer of cloth was STRETCHED over the hull using bungees. This way the cloth could be wetted out after it was hung. An extra foot of cloth above the water line was left for bungee attachment. Strips of Masonite were cut and hot glued to the extra foot of cloth while the cloth was laid out on a clean driveway. Bungees were attached to these stripes to stretch the cloth around the hull. The Masonite came from 4x8 sheets of workshop stock. It had predrilled holes for tool hangers. These holes were used to attach the bungee hooks. The largest piece of cloth was 15 feet long and 4 feet wide. Working with material this large, over-head, would be impossible without a method to stretch the material and hold it in place. Also as the cloth is wetted out it stretches. The elastic bungees took up the stretch as it occurred.

Setting up our cloth using bungees is NOT a quick solution. It is a solution that will enable you to cover a hull and avoid fairing after the hull is covered. Because you will be laying up two layers of cloth, wet on wet, you need to set up for two sets of bungees. You also need to test hang all of the pieces of cloth (both layers) before you wet any of them out. Any adjustments have to be made before you start working with mixed resin. Once resin is mixed you well be starting a continuous process that has no time for errors.

Working with epoxy takes practice. Too much resin in the laminate and it will curdle as it cures creating a maze of grooves and mounds in the laminate that will result in a nasty fairing problem. Too much heat (sun) and you will run out of time. Too cool and you will get a bad cure. The first piece of cloth that we applied was a mess. We did not roll enough resin out of the laminate and it curdled. It looked beautiful one minute and like a mouse maze the next. After the resin began to set up no amount of rolling would keep it flat. We had to grind it off and recover that area.

We applied the cloth in four steps, and four days. Eight days were required in total because each lay-up day was preceded by a setup day. The four hull sections were completed as follows, first from the forward edge of the keel to bow (both port and starboard), then aft end of the keel to the stern (both port and starboard), then the port side of the keel and then the starboard. Two layers of cloth were applied, on the same day, to each section. The first layer of cloth was butted together, not overlapped. The second layer was staggered 6 inches forward and butted as well. The second layer was applied while the first layer was still wet. Teflon peel ply was put over the second layer before the laminate was rolled out using a ½ inch resin roller. The Teflon peel ply is wonderful stuff. It allows you to roll the heck out of the laminate so you can attain a very fair surface if you have a fair surface to begin with. And as an added bonus you can remove the peel ply after the resin cures and you do not have to sand the surface or wash off an amine blush. We washed it anyway to be safe.

In summary the steps went as follows, start with a clean, washed, sanded, fair surface. Mix enough resin for the first layer of cloth, use a West foam roller to roll the resin onto the hull, hang the first layer of cloth and stretch it, roll more resin onto the first layer of cloth, your helper is now mixing resin for the next layer, hang the second layer, stretch it and roll on more resin. Then (very important) use a serrated resin roller to remove the excess resin and put on the peel ply. Finally use the serrated resin roller to remove the remaining excess resin. All this must be done before the resin begins to kick. Before starting a section measure and cut the cloth, glue on the Masonite ends, cut your bungees and TEST HANG both layers of cloth to make sure you’ve got it right before starting the real job with real resin. Using epoxy resin is like pouring concrete. Once you start you do not want to stop.

Next came limited, finish fairing. Remember our goal was to do as little fairing as possible and to avoid using any fairing materials but no laminate can be laid up perfectly. First the butt joints were filled with West epoxy mixed with micro balloons. This required only a very small amount of fairing material. Next the entire hull was washed with water and solvent, given a dual-action sanding with 40 grit, washed with water and solvent again and given 3 heavy coats of Interprotect 3000. Interprotect 3000 is normally sprayed on but it can be rolled on. Because 3000 is almost 100% solids it is good for fairing but only light fairing because it is so hard. The whole boat was then lightly faired with an air file using 40 grit and rewashed. About 8 hours of fairing time was required. This is very small compared to a traditional fairing process using 2 full time men for several weeks. Finally 3 more coats of Inter Protect 3000 were rolled on followed by 1 coat of Interprotect 2000e and bottom paint. The bottom paint was applied before the 2000e cured so that a chemical bond was made.

The good news is that the total cost of this cure was about $5000 in materials and a lot of labor. This is good considering the yard estimate was $30,000 minimum plus transportation costs. But before you start such a project you should carefully consider the following.

  • When you work with epoxies you need to follow the manufactures application instructions very carefully. This is especially true for over coat times (min and max) and for washes. Both water washes and solvent washes are required. Also as little as a 10 degree difference in temperature can make a big difference in the time window you have to work with. Be especially aware of direct sun light. If you do not have experience laying up epoxy laminates, cover a rowboat first and keep track of temperatures and cure times. Practice on something that you can throw away. You will be spending thousands of dollars on materials and you can create a bigger problem than you started with if your work is not done right. Try explaining that to your wife.
  • Grinding the gelcoat and mat off of a hull creates far more dust than most boat yards would ever put up with. A hand held peeler can be purchased that uses a suction bag for dust but at some point you will probably have to do some serious grinding and have a lot of dust to deal with. You will probably need to be at a country marina that can put your boat far away from any other boats. Or you may be able to put your boat by your home. Where I live the city allows 1 RV in a yard as long as it is on a drive way or hard surface and 15 ft from the road. Sand blasting is even messier than grinding and well not be tolerated unless you know your neighbors very well.
  • Do not buy a hull that has moisture readings that are abnormal because a hull that does not stay dry after it has been dried out could be a total loss. There is no way for you to know if a hull will stay dry until it has been dried so don’t take a chance. A bad hull well absorb water right out of the air after it is dried. If that occurs I believe the hull can not be repaired.
  • Finally this is not the kind of project that is good for someone that has only a few hours on a weekend to spend proceeded by a 2-hour drive. You need to be at the boat a solid 16 hours a week for this type of project to work. And you need a very willing helper for ¼ of that time. On the plus side, if you have the time most of the work is fun and you can end up with a valuable product that will give you a long ride. The more that you document your work the more your product will be worth.

So what caused the star cracked hull anyway? Here are some expert’s best guesses.

  1. There probably was a problem with the gelcoat resin. The same star cracks occurred on the inside of the hull in the bilge where water collected but only where gelcoat was used. The interior gelcoat chipped off in pieces that were up to 4 square inches. But unlike the exterior coating when the gelcoat in the bilge was removed, very solid, unhydrolyzed, laminate was exposed. This indicates there was probably also a problem with the mat layup outside the hull. See (3) and (4) below.
  2. The gelcoat was too thick, 1/8 the inch and thicker.
  3. The first layer of mat was poorly wetted out trapping a lot of air in the laminate.
  4. The first layer of mat was not laid up until the gelcoat had cured too long creating a poor bond.
  5. Particles that attract moisture and trigger the destructive hydrolysis process were present in the mat laminate when it was laid up.
  6. Poor resin used in the 80’s?


Stan Sroga



Home| Highlights| FAQs| Course Overview| Live Aboard Classroom| Course Schedule & Fees| Contact| Sitemap