If your jet ski or waverunner hull is made of fiberglass then gelcoat can be an excellent restoration option. Gel coating a jet ski is a great way to keep it looking new and protect the surface from scratches and dings. It’s also a relatively easy process that most people can do in a few hours. In this blog post, we’ll walk you through the steps of how to gelcoat a jet ski. We’ll also provide some tips on how to make the process go as smoothly as possible.
What is gelcoat and what does it do
Gelcoat is a type of resin that is used as a protective coating on many boats, jet skis, and wave runners. It is applied to the hull of the vessel in order to provide a shiny, smooth finish. In addition to its aesthetic benefits, gelcoat also helps to protect the hull from UV damage, scratches, and other types of wear and tear. In some cases, gelcoat can even help to repair minor damage to the hull. As a result, gelcoat is an essential part of any boat or jet ski owner’s arsenal. While gelcoat can help extend the life of your jet ski or wave runner, it is not indestructible. Over time, it can become dulled or scratched, and it may eventually need to be replaced.
How to clean and prep the jet ski surface before you start
To clean the jet ski, you’ll need a mild soap, a soft cloth, and a jet ski brush. Start by mixing the soap and warm water in a bucket. Then Wet the jet ski with the soapy water and use the brush to scrub away any dirt or grime. Rinse the jet ski off with clean water and dry it with a soft cloth. For tough grease and dirt spots you can use a degreaser. This will remove any dirt, grime or grease that could prevent the paint from adhering properly.
Finally, inspect the jet ski for any cracks, chips or other damage. If you notice any of these, make sure to get them repaired before applying gelcoat. Use a fine-grit sandpaper to smooth out any rough spots. Gel coat repair kits, scratch patch kits, gel coat paste, fiberglass repair kits come with everything you need for small repairs.
Applying the gelcoat to your jet ski, wave runner
Applying gelcoat to a jet ski is a great way to protect your investment. Gelcoat is a clear or colored coating that is applied to the surface of a jet ski to protect it from the elements. It is also used to give the jet ski a high gloss finish. Gelcoat is available in both spray and brush-on versions. The brush-on version is generally easier to apply, but the spray version will give you a more even coverage. When applying gelcoat, be sure to follow the manufacturer’s instructions carefully. In general, you will want to apply several thin coats rather than one thick coat. Be sure to allow each coat to dry completely before applying the next one. Once the gelcoat has been applied, you will need to buff it out to achieve a high gloss finish. Once the final coat of gelcoat has been applied, the jet ski should be allowed to cure for 24 hours before being launched.
It’s important to choose the right gelcoat. There are dozens of different formulations on the market, so it’s important to do your homework and consult your owner’s manual. Once you’ve selected the right gelcoat, the next step is to apply it correctly. One common mistake is to apply too much gelcoat, which can lead to runs and sagging. It’s important to apply a thin, even coat and then allow it to cure properly before sanding or buffing.
With these tips in mind, your gelcoat project should be easier. Just remember to take your time and follow all instructions carefully, and you’ll soon be enjoying your jet ski on the open water. If you have any questions about selecting the right gel coat for your watercraft, please call the Bottom Paint Store customer support team 888.505.2313.
There are many common fillers used with gelcoat and resin and here we’ll help you pick the one that is right for you.
When using putty, a good rule is not to go higher than 1/8″ thick without adding a layer of glass to prevent any issues. With the various fillers, for the right working consistency, you’ll want about 60-70% mix to resin ratio.
Milled Fibers: Finer than chopped glass, makes a harder putty that is strong and coarse.
Walnut Shells: Brown in color and preferred for wood putty or nonskid since it has large particles. Good Strength and darker pigment.
Microballoons or Microspheres: Phenolic spheres are generally plastic or glass and hollow, intact spheres that are lightweight. This is ideal for making fairing compounds. The Microballoons are a more expensive option for filler.
Fumed Silica: Also known as Cabosil FIller or Aerosil Filler. This is a hydrophilic fumed silica. Fumed Silica provides little change to weight, color, or physical properties after cure, used in resins and gelcoats to make them hang on vertical surfaces, (too much can cause porosity.)
Cotton Flock: Made from pieces of cotton and thickens to an off-white color. Great for bonding many substrates, especially wood. The mixture also creates a multipurpose adhesive for many other substrates in addition to providing excellent substrate wetting and penetrating characteristics. Increases impact and abrasion resistance.
Chopped Glass: These are the biggest pieces of fillers and are most popular for use with resin putty. Perfect for corners, crack resistant, and doesn’t affect pigmented gelcoat. 1/4″ glass fibers make the strongest glass reinforced putty.
Webbing Solution is a clear liquid added to gelcoat to obtain spatter or cobweb effects. It is mixed with a gelcoat of one color and sprayed onto a contrasting colored surface.
Decorative effects produced by the webbing mixture will vary, and relate directly to techniques or gun adjustments. A fine hairline spider web pattern results from plenty of air and scanty material flow. Coarse and splotchy patterns are created by fuller material flow and decreased air volume. While our webbing solution is only tested with gelcoat, customers do use with paint achieving similar results.
The manufacturer suggests on the initial coat you add the wax and while gelcoat is still tacky before it comes to a full air cure, you apply the contrast color of webbing (which should have the wax added too).
If you are applying webbing over a fully cured gelcoat, sand with 150 grit, clean with acetone, and then apply the webbing.
Mix 2 parts gelcoat to 1 part webbing. Mix proper amount MEK-P for the amount of gelcoat. Shoot at 10 to 12 PSI.
Add to colored gelcoat to obtain desired webbing effect. Test in an inconspicuous area to determine satisfactory results
There are many ways to repair spider cracks in boats, using our Gelcoat Repair Putty is an easy and fast way of doing it!
First, you will need to determine your spider cracks are only that, spider cracks. To do so, you will need to inspect the area for any sign of broken support. If the surface is steady and looks solid, then you have spider cracks.
In order to properly fix any spider cracks, you will have to open the cracks to fill them up correctly. This can be done by using a Dremel. Once the crack is open and it has a good size you can sand and clean the area. For cleaning, you may use acetone or soap and water.
Now, you are ready to use the Gelcoat Putty. Mix in a 1-1/2% ratio of MEK-P Catalyst into the putty and mix it properly. Use a putty knife to fill in the spider cracks. Once dry, sand the surface to a smooth finish.
For filling gauges and cracks, some tips:
This product uses MEKP, just like gelcoat so your working time is 8-18 minutes, depending on temperature. If catalyzed at 1% and it is in perfect conditions (77 F) you have a longer work time. To extend work time cool product down before use.
If filling holes, fill a little high to allow for shrinkage. Once it dries you can easily smooth it out with sandpaper. Recommended thickness at 1/4″.
Gelcoat does not fully cure without first supplementing it with a surfacing agent or wax additive sanding aid. Gelcoat may be thinned for use in a Portable Preval Sprayer with styrene monomer. You can spray it with polyvinyl alcohol (PVA) before gelcoat reaches its gel stage (5-10 min.), or add 1oz per quart of a wax additive sanding aid.
PVA or Partall Film #10 is a release agent that helps with removing parts from a mold or can be used as a surfacing agent when using gelcoat without a wax additive (sanding aid).
PVA is soluble in water making it easy to wash off. Applying can be achieved by spraying or wiping the green liquid on with a sponge. It will foam slightly but dry to a clear, glossy shine. It can take 15-30 minutes depending on temperature.
For spraying gelcoat our FGCI brand does not recommend thinning.
Generally, you should not add more than 10% Styrene by volume. Patch Booster is an additive that will thin out gelcoat and not affect colors. Follow manufacturers instructions as added Mekp may be needed.
Another thinning alternative is the Duratec High Gloss Additive. This is used with gelcoat for many reasons. Mixed at a 50/50 ratio this will produce a high gloss finish and will serve as a thinner for your gelcoat, that is why this is commonly used when spraying gelcoat. In addition, you’ll omit any additional sanding aid. After waiting a full 24 hours you can buff when cured, for a hi-gloss use 600 or higher grit paper and buff with Aqua Buff 2000 compound. Follow the manufacturer’s technical data sheet as an extra hardener may be needed. Some customers use Styrene for thinning but the manufacturer warns it can affect the gelcoat colors although this is the most cost-effective option and doesn’t have the added wax.
Depending on the job at hand, we offer a few types of fiberglass cloth to choose from and different cloths are used for different jobs. They are available in different widths and are sold by the roll or yard.
Mat– This mat is used for parts and is great for not showing fiberglass patterns through gelcoat. Mat has many small fibers thrown together on a binder and is the most used, basic cloth. There is no specific direction to the fibers, making them strong and light. Sold in ¾ oz up to 2 oz thickness.
Woven Roving-This weave has long fibers weaved together like a cloth. It is extremely thick and durable making it heavier than other fiberglass materials. This often shows pattern through gelcoat and is used for heavy-duty items. Sold in 18 and 24 oz thickness.
Double Bias Non Woven- 1808, the first number is the woven roving thickness (18oz) and 08 is the mat thickness (3/4 oz). This is a combination of woven roving on one side and mat on the other, making it very durable and usually used for boat and house decks as it is very rigid.
Fiberglass Cloth– This is sold in 4, 6, 8 and 10 oz thickness and is very fine. While being rigid it is also used for anything that is see-through, such as surfboards as it’s thin, lightweight, and shows well with clear resin.
The finish of your fiberglass pool steps can fade after years of use and exposure to pool chemicals and the weather. If you notice that your pool steps are looking tacky it might be time for you to reapply gelcoat to them.
You can use Gel Coat if your pool steps currently have gelcoat or bare fiberglass for pool use. We don’t recommend the brushable gelcoat in pools because the chemicals can affect the gelcoat lifespan.
Brushable Gelcoat, often referred to as gelcoat paint, is a specially formulated product that is made to be applied like paint and eliminate the need for spray equipment. It has excellent leveling, Water/Osmosis resistance, UV light Stability, great Gloss Retention, and fantastic long-term durability and is available in a variety of colors. Here are some tips for successful brushable gelcoat application.
Applying Gelcoat by Brush or Roller – (Use a Brushable Gelcoat) When applying gelcoat by brush or roller, we recommend the Ultra Plus Brushable Gelcoat. (other Gelcoats are best applied by Spray) The Ultra Plus Brushable Gelcoat is designed for self-leveling and is a much easier application. It allows for a much smoother finish and less time for finishing the gelcoat. It is easy to use for the “do it your selfers’! Choose a good pure (natural) resin-resistant bristle brush with tapered ends. Avoid brushes that are either too stiff or too soft. For most work, a 3″ or 4″ wide brush will suffice. If there is a trim color, you should have a narrow trim brush on hand. Our Brushable Gelcoat comes with an MEKP hardener with every purchase, but you may need more which you can purchase as an option depending on the application, temperature, and other environmental factors. Gelcoat needs to be applied evenly. We suggest a thickness of 18-20 mils to properly cure. The thickness of the matchbook cover is approximately 18 mil. If you’re not sure how thick it is, pick up a mil gauge. This is a simple, easy way to see the thickness of your gelcoat.
Don’t add Patch Booster or Sanding Aid (wax). You don’t need to add sanding aid (wax) to Brushable gelcoat to have it dry tack-free. The self-leveling technology added doesn’t require any additional products or additives.
Proper gelcoat application requires you to apply your coats about 15-20 mils thick. We offer mil gauge for purchase.
Allow the gelcoat to cure overnight and then lightly sand it and buff it for an outstanding shine!
Use Acetone for your cleanup. Just like other Polyester-based products, Acetone is the best cleanup material!
The most important step: Adding the proper amount of Catalyst. We recommend 1.5%-2% Catalyst ratio. After adding the catalyst, you will want to mix for two minutes, preferably with a mechanical agitator (drill mixer). For your reference, here is the catalyst chart so you know exactly how much catalyst you need.
Brushable gelcoat is not recommended for pool surfaces.
Tips 1 mL = 1 cc If using wood mixing stick, place stick in resin before adding catalyst so wood doesn’t absorb catalystOnly catalyze slightly more than needed. Resin that cures still in the mixing pot is unusable.
Be sure to have a good strategy when applying your gelcoat. Once you mix and catalyze, you have about 15 minutes to apply the gelcoat before it starts getting hard or starts to “gel.” The actual working time depends on the amount of catalyst and how hot the working conditions are. Anything below 60 degrees and your gelcoat will not cure, but as you get warmer and warmer, your working time will decrease rapidly. At 70 degrees, you get 15 minutes, but at 90 degrees, you only get 5 minutes. If you need more time to work, be sure to sit the can in some cold ice water to cool it down to 60 degrees to allow you a little more working time.
Here are some helpful tips on how to work with brushable gelcoat, especially during the warmer months.
Cooling the gelcoat, by refrigerating the product to around 70 degrees, will give you up to 15 minutes of working time.
Humidity can be another factor, so, make sure the mold and surrounding area is dry before applying your brushable gelcoat.
Make small batches of gelcoat at a time and catalyze at 1 ½ % to avoid the material from getting hotter. When spraying the gelcoat, make sure you catalyze at 2 %. If you choose to use Duratec, please note, that the product must be cool as well.
If you seek to roll on the gelcoat, the product should be applied evenly at 14 mil thick.
A fiberglass boat is a great investment. They are durable and can last for years with proper care. But like anything else, they are not indestructible and will eventually need to be repaired. One of the most common repairs is patching a hole in the hull. Fortunately, this is a relatively easy repair that can be done by anyone with basic fiberglass repair skills.
The first step is to clean the area around the hole. This will remove any dirt or debris that could prevent the patch from adhering properly. Next, cut a piece of fiberglass cloth that is slightly larger than the hole. Apply a generous amount of fiberglass resin to the cloth and then place it over the hole. Use a roller or brush to smooth out the cloth and remove any air bubbles. Allow the resin to cure for 24 hours before sanding down the area and painting over it. With a little time and effort, you can have your fiberglass boat looking like new again.
A major fiberglass repair, such as patching a hole, can be a daunting task. Watching a professional do the job can help you get on the right track and be confident in doing the repair yourself. This step-by-step video tutorial produced by Sea Hawk Paints will show exactly what needs to be done when patching a hole in your fiberglass boat.
Note: Before attempting a repair by yourself, get a professional opinion. Always wears Personal Protective Equipment when sanding or working with chemical compounds! Respirator, safety glasses and gloves are always recommended.
Here is a list of products you will need for the repair:
Fairing is process of smoothing out and restoring the damaged surface of the hull. A fairing compound such as Epoxy resin can be used to fill in divots or gouges and then be sanded to a smooth finish. This restores the surface to its original shape and also prepares it for painting.
Note: Before attempting a repair by yourself, get a professional opinion. Always wears Personal Protective Equipment when sanding or working with chemical compounds!
Here are some guidelines to fairing out imperfections in your hull:
Sea Hawk’s Epoxy Pump Kit makes it easier than ever to measure the Resin to Catalyst ratio very accurately, and get the same result every single time! But how are the pumps intended to be used?
The Pump Kits come in two sizes, one kit accommodating the Size 1 and 2 Resin and Catalysts, and one kit accommodating the Size 3 Resin and Catalysts. Be sure to get the right size kit for the amount of resin and catalyst you plan on using. The Kit contains a total of 3 pumps; one for R1 Resin, one for C2 & C3 Catalyst, and one for C1 & C5 Catalyst.
The Hawk Pump Kit User Manual and instructional video explain how to use the pumps for accurate measuring, how to prime the pumps, pump cleaning and storage, and how to use the pumps with various Hawk Epoxy System Sizes.
R1 Epoxy Resin – a smooth, low-viscosity liquid epoxy resin. With a variety of Hawk Epoxy Catalysts, it can be cured under a wide range of temperatures and environmental conditions to form a high strength plastic with superior moisture barrier characteristics. Hawk Epoxy repair kit is available in four system sizes color coded on each label. Note: Mix ratios vary by catalyst. For optimal product utilization, be sure to choose the same Size for both the resin and catalyst. I.e Size 1 Resin with Size 1 Catalyst.
C1 ULTRA SLOW CURE CATALYST:Designed for use with HAWK EPOXY R1 Resin for construction and repairs with superior adhesion, strength, bonding, filling, and moisture barrier qualities at higher temperatures and for an ultra slow cure. Do not use under Sea Hawk marine wood varnish.
C2 SLOW CURE CATALYST: Designed for use with HAWK EPOXY R1 Resin for construction and repairs with superior adhesion, strength, bonding, filling, and moisture barrier qualities at higher temperatures and for a slow cure. Do not use under Sea Hawk marine wood varnish.
C3 FAST CURE CATALYST: Designed for use with HAWK EPOXY R1 Resin for construction and repairs with superior adhesion, strength, bonding, filling, and moisture barrier qualities at cooler temperatures and for a fast cure. Do not use under Sea Hawk marine wood varnish.
C5 CLEAR FINISH CATALYST: Designed for use with HAWK EPOXY R1 Resin for very clear fiberglass cloth and coating applications with exceptional moisture barrier characteristics. Perfect for natural wood and carbon fiber clear coats with no blush. Longer working times in very warm temperatures. May be used under Sea Hawk marine wood varnish.
TIP* For easy accurate measuring be sure to use the Hawk Epoxy Pumps that are calibrated to dispense the correct amount of resin and catalyst. This is much easier and leave little room for mistakes.
Next choose the best Hawk Epoxy Filler depending on the application:
F1 High Load Adhesive Fiber Filler– Thickens to a light grey color creating an easy to use adhesive designed for bonding hardware and other applications with dissimilar materials. This mixture will maximize bond strength for anticipated high loads.
F2 Structural Adhesive Filler– Thickens to an off white color, creating a general purpose thickening additive for bonding, gap filling and filleting. Mix to a workable consistency allowing sag-free and easy flow properties for vertical and overhead applications.
F-3 Light Density Adhesive Micro Fiber Filler – Thickens to an off white color. Great for bonding many substrates, especially wood. The mixture also creates a multipurpose adhesive for many other substrates in addition to providing excellent substrate wetting and penetrating characteristics. Increases impact and abrasion resistance.
F4 Bridging Adhesive Filler – Thickens to a brown color, creating an easy to use adhesive with excellent gap filling and filleting qualities. This mixture blends with many different types of wood to allow for a natural looking fillet or gap fill.
F5 Light Density Fairing Filler– Thickens to a reddish brown color, achieving an easy to sand and carve fairing compound while still remaining strong and light weight.
F6 MicroSphere Fairing Filler – Thickens to a white color, creating a lightweight fairing compound for small to large areas. This product holds a feathered edge very well and is suitable for nearly every substrate. This closed celled structure can also be used for increased acoustic and thermal insulation.
Make sure the blisters are thoroughly drained and grind them deep enough to remove any damaged material beneath the gelcoat. Increase size of ground area as needed until all the laminate around the blister is sound. Clean the entire area and allow it time to dry.
The filler recommended for blister repair is F6 MicroSphere Fairing Filler. F6 MicroSphere Fairing Filler thickens to a white lightweight fairing compound for small to large areas.This creates an easy to sand putty that will help fill in transitions and hull imperfections. Apply using a putty knife, spatula or trowel. Spread smoothly on the surface in a 1/8″ – 1/4″ layer using heavy hand pressure to displace air bubbles/voids. Try to force the material into holes or joints and smooth to the thickness needed.
Before applying the Hawk Epoxy, the hull must be very dry. Make sure the hull moisture is under 15% by using a moisture meter. Wipe down the entire area with clean rags and acetone. This will remove any remaining contaminants on the hull.
Hawk Epoxy is a low viscosity epoxy system that makes fiberglass repair easy for everyone! Equipped with a wide variety of Catalysts and fillers, you can mix up the exact epoxy batch needed for almost any job. For more information on how to mix Hawk Epoxy,click this link. Mix only enough Hawk Epoxy to use in 5-10 minutes. Apply the Hawk Epoxy to the hull using the Roll and Tip method. Use a roller to apply the epoxy and then use the tip of a high quality brush to smooth the epoxy evenly. The roller should be lint free and non-wicking. Any fibers that get in to the epoxy could compromise the integrity of the seal.
Apply the second coat when the first coat is tacky to the touch. Your finger should leave an imprint but not lift any of the epoxy coating. Allow the second coat to dry fully. Once it is completely cured, wash the repaired area with soap and water. The repair is now ready to be sanded and painted with Sea Hawk bottom paint. If redoing the hull apply Tuff Stuffprimer, followed by bottom paint.
If the blister has damaged the fiberglass, that will need to be repaired with fiberglass clothcut to match damaged area.
The video below is from Sea Hawk Paints and demonstrates how to seal a fiberglass hull using the Hawk Epoxy System.
When it comes to boat repair, epoxy and polyester resins are both popular choices. But which one is the best option? Epoxy resin is known for its strong bonding properties, making it ideal for repairing cracks and holes. It also has excellent waterproofing qualities, making it ideal for boats that spend a lot of time in the water. Polyester resin, on the other hand, is a bit more flexible than epoxy, making it better suited for repairs that require some give. It’s also less likely to yellow over time, making it a good choice for boats that will be spending a lot of time in the sun. Ultimately, the best choice of epoxy or polyester resin for boat repair depends on the type of project you are tackling.
Every household should own a Hawk Epoxy Kitlike this. You can use it to repair anything around your home or own your boat. This kit comes with the resin, catalyst and your choice of filler. Just mix them together and you have an excellent bonding, filling, or adhesive paste.
FGCI General Purpose Resin is used for laminating with fiberglass, kevlar and carbon reinforments. It can be tinted with pigment up to 3% and best results are when used at 70-85 degrees F. Hardener varies depending on thickness of fiberglass, the more fiberglass the less hardener as you will generate more heat-never go below 1%. Complete cure needs sanding aid added to resin or PVA while still hot.
Polyester resins are unsaturated resins that are combined with hardeners, such as MEKP.
Polyester resin is used more for fiberglass lay-up or if you’re going to finish a repair with gelcoat, as the polyester resin will bond to the gelcoat better than epoxy. It is also cheaper than epoxy and a great choice when casting deep molds.
Various Types of Polyester Resin:
Boatyard Polyester Resin is a non-specified resin that contains different types of polyester resins and wax. Boatyard Polyester Resin is not recommended for use below the waterline. The material may cure hard and tack-free due to the included wax. If so, the product will need to be sanded prior to adding another layer in order to promote good bonding.
Clear Casting Polyester Resin is used to cast small objects into a mold. This method can be used to create sculptures, crafts, or industrial prototypes.
Surfboard Polyester Resin is Clear & wax free. It is ideal for building & repairing surfboards because it cures to an almost clear color when applied in a film. Also it highlights underlying graphics.
Iso Marine Resin is based on isophthalic acid. This resin is a step above the general purpose polyester resin and that is reflected in the price. Iso Resin is stronger, more durable, and is the best choice when applying in corrosion environments or elevated temperatures.
Vinyl ester resins are formulated with a base of polyester resin strengthened with epoxy molecules (a hybrid form of polyester and epoxy and aiding for gelcoat to bond with epoxy) and also use peroxides, such as MEKP, for hardening. These are cheaper than epoxy resins and more expensive than polyester. Ideal temp for use is 77 F, not applied over 1/8th thickness or it will generate too much heat.
Vinyl esters are more tolerant of stretching, less likely to show stress cracking and more resistant to water penetration. Vinyl ester is the choice when improved resistance to moisture is the goal (like repairing a blistered hull).
Long term water exposure (hull or water tank) or if impact resistance is important vinyl ester is usually chosen.
Epoxy resins are cured with the addition of a hardener. Unlike the polyester and vinyl ester resins, cured with a small amount of catalyst, epoxy resins usually require a lot more, often 1:1 or 2:1. A epoxy resin is the most expensive of these.
Epoxy resin has the best bonding strength as it will bond dissimilar or already cured materials for strong, reliable repair work. This is the most expensive resin but offers the most in its ability to flex, prevent delamination and ease of repair work.
If doing a repair and not overlaying with gelcoat then the epoxy will perform best as it tends to act as a stronger “glue” for the patch to the surrounding surface.
Laminating Epoxy Resin is the correct choice for repairing boats. It is super durable and has high resistance to water. Also, it has very good adhesion to a variety of surfaces including metals, plastics, fiberglass, wood, and glass. The ratio is well suited for use with high-solids marine, maintenance coating and bonding agents. The cure time is three days in the sun or a week if it is not. Set time changes with activator and film thickness. If there is an excessive amount of activator applied , the laminating epoxy will be soft and rubbery. In contrast, if there is not enough activator, the epoxy will not cure hard. Laminating Epoxy is available in 3 different ratios that provide different working and cure times.
A Premium Commercial Grade Clear Epoxy Resin – Klear Kote Epoxy Resinis used extensively in coating surfaces and in table tops where a clear, hard and durable coating is required. Commonly seen on bar tops and restaurant tables. Easy to use 1:1 mixing ratio of resin and hardener. Items coated with it will become permanently preserved and protected for your enjoyment throughout a lifetime. The epoxy resin will not exhibit blushing or sweat out under high humidity conditions.
Epoxy resin kits are sold in two parts, A and B, which should be applied in two stages. The first stage is referred to as the seal coat. The seal coat is brushed on in a thin layer and is used to seal any pores on the surface and prevent air bubbles from forming in the following flood coats. This stage is followed by the flood coat, which will flow and self-level, clean brushes or squeegees can be used to help spread the epoxy. Flood coats are applied in 1/8″ layers at a time, as many as desired can be applied, however, one to three coats is average for most table or bar coatings. Resin kits are often applied on bar tops and tabletops in many bars and restaurants.
Superbond Standard Epoxy Glue
Superbond Standard Epoxy Glueis a two-part, 1:1 epoxy adhesive that has a Vaseline consistency. The product adheres to nearly everything and is a favorite among woodworkers. It’s offered in a fast curing agent, giving 8-15 minutes of working time; a medium, giving 20-30 minutes, and a standard, offering 30-45 minutes. SuperBond is offered in sizes from ½-pint tubs all the way to 5-gallon pails.
Rot Stop Epoxy
Rot stop epoxy is a 2-part epoxy that is 1:1 ratio and is very simple to mix. The coverage is similar to other epoxies, and like other epoxies, the product does vary in thickness based on temperature. The advantage of Rot Stop is it is NOT affected by moisture, making it excellent for deck or flooring and cracking repair, especially moisture damage.
Gelcoat and resin spray guns are ideal for large surface spraying, such as new mold construction, composite refinishing and large boat surfaces. Look for a resin gun with a blue die cast body which will ensure a long life. Most HVLP cup guns use nylon flat seal just behind the threads that the air cap attaches to.
If you have used a spray gun with a nylon flat seal just behind the threads that the air cap attaches to and cleaned it with acetone, the seals disintegrate so it is best to use one with a plastic seal.
In order to have a form from which to develop your mold, you must either build the article from scratch using wood, plaster, polyester putty, formica, sheet metal, etc. or you must have on hand a completed article which you wish to duplicate. The latter is of course the fastest method. The plug is generally a male model exactly like the item you wish to fabricate in every detail. If the plug does not have draft (taper) then you will have difficulty getting parts off. If the plug has reverse bends, like many canoes, then you will need to make a split mold which can be spread or taken apart.
If the plug contains soft materials on its surface such as plaster, wood, or putty, then it will have to be sealed with lacquer orresinto fill the pores. If plaster is used, it must be oven dried and then sealed.
To prevent your mold from sticking to the plug, the plug must be coated with plastic film known as “PVA.” This is a plastic dissolved in alcohol and has a green color. It can be brushed or sprayed on, but the best system is to spray on three thin coats, the first being a “mist coat.” The appearance will then be green. Each coat must dry half an hour or so and there must be no pools or drips to blemish your mold surface. For the easiest possible parting, before applying the PVA, apply a soft wax (TR Mold Release) formulated for use with PVA.After the third coat ofPVAhas dried, a coating of this wax can be gently applied over it for easy parting.
The first step is to apply a gelcoat which will be the mold surface. Thegelcoat must be “exterior gelcoat” (wax free). If many parts are to be taken off the mold, it is desirable to use a“tooling gelcoat” which is designed to give longer life in mold use. The gelcoat should be in contrasting color to the surface of the part you will make. Since most parts are light colored, black gelcoatis commonly used. This facilitates spraying up a uniform thickness of light colored gelcoat since the black will show through thin spots.
If the gelcoat is to be brushed on, two coats must be applied, and the first coat must cure several hours before the second coat is applied. The best means of gelcoat application is a simple gelcoat gundesigned for the purpose and easy to clean. Air pressure of 80 to 90 pounds is desirable. Gelcoat must be applied at least 15 mils thick, or a quart to every 25 square feet of surface. If the plug was rough so that considerable sanding of the gelcoat will be necessary, then double the application. Before applying the gelcoat, it must of course, be catalyzed with MEKp peroxide hardener, using from one to two percent. All gelcoats from the Bottom Paint Store include the MEKp.
When the gelcoat has cured so that it cannot be scratched off with the fingernail at the edge of the mold, which takes from 2 to 4 hours to overnight in cool or humid weather, you are ready for the “skin coat.” This is a layer of ¾ or 1oz. fiberglass mat, thin enough so you can see and remove all air bubbles entrapped by the resin when you “wet-out” the mat. The resinshould be applied with amohair roller or brush until no white fibers remain. Any air bubbles are then eliminated with a grooved plastic or metal laminating roller. The polyester resin used should be “lay-up resin,” which is wax-free. Be careful not to over-catalyze when laying up the glass. Above 75°F one 10-15 cc of hardener to the quart will generally suffice. Below 70°F, 20 cc per quart. Do not work below 65°F.
In laying up a fiberglass mold, warping can be avoided by allowing each layer to “kick” or gel before proceeding with the next layer. For a large mold, it is good to apply just one layer per day. After the “skin coat,” you can use 1½ oz. fiberglass mat for a faster build-up. Generally, woven roving is not used in molds because the pattern transfers through the mold to the gelcoat. If it is necessary to use woven roving fiberglass for strength in a large mold, it is applied after a thickness of 3 or 4 layers of mat has cured hard. The thickness required in a mold depends upon size and shape and the number of parts to be taken off. For a dinghy mold to be used only a few times, four layers of mat might be adequate.
Removing mold from the plug
Allow mold to cure several days if possible so it will hold its shape. The first step is to trim the excess laminate back to the molded edge. This is easily done with a saber saw and a metal-cutting blade. The edges are sanded carefully until the line between the mold and plug is exposed. Then a sharpened “tongue stick” is forced between mold and plug to separate the edges. The stick is then pulled clear around the plug until all edges are free and no bridges remain. Avoid using metal tools for this purpose as they will scratch the mold surface. Then the mold should pull free of the plug. If not, the parts can be flexed or pounded gently with a rubber mallet. If necessary, air or water can be forced under pressure between plug and mold. A hole can be drilled through the interface for this purpose. PVA is water soluble, which facilitates parting with water pressure.
Polishing the mold
Depending upon the condition of the mold surface, it may have to be sanded with 220 grit working up to 600 grit wet or dry. The surface is then compounded with regular and fine finish compound formulated for fiberglass work. Best results can be achieved by using special compounds such as 3M Finesse-It Marine Paste Compound to bring out a mirror finish.
Before using a mold, it should be allowed to cure a week or more if possible. Be sure to use PVA parting film and soft wax for the first 3 or 4 parts, after which a carnauba wax can be used.
Alligatoring, or wrinkling, can result from:
1. Gelcoat too thin in some spots
2. Insufficient hardener, or hardener not mixed will enough.
3. Gelcoat not cured long enough before mat lay-up.
4. Acetone cleaner drips out of roller or brush during mat lay-up.
Original technical article provided by Fiberglass Coatings.