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.
Phenolic Microballons
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 Fibers
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.
Repairing a hole on the side of your boat is possible by following this guide and using epoxy resins for wooden boats.
Begin by inspecting the hole for any cracks that extend away from the hole and clearly mark the entire area that needs to be patched. You want to be sure to extend your mark out beyond the damaged area by a few inches.
Hawk Epoxy f2 Structural Adhesive Filler
Cut the marked area with a hand saw making sure the hole is beveled in order to allow layers of fiberglass to fill the hole. Measure the thickness of the hull substrate and multiply it by 10. This is the distance from the hole edges that the bevel needs to accommodate.
Use a power sander with a 50 grit sanding disc to bevel from the whole edge out to your mark. Fiberglass layers are going to be placed on the outside of the hull. Use a flat backing on the inside of the hole to keep the wet fiberglass cloth from caving into the hole.
Next cut six pieces of fiberglass bi-axle cloth with the first piece being the size and shape of the outer edge of the bevel. The final sixth piece being the size of the hole itself. Remember it is important to use fiberglass bi-axle cloth for hole repairs.
Wet out the beveled area of the hole with a mixed epoxy. Lay the cut fiberglass bi-axle cloth on a piece of plastic going from large to small pieces. Make sure to wet each piece as you place them on top of the next piece. When wetted out properly the bi-axle cloth will become transparent. Put the wet out pile of fiberglass bi-axle cloth into a piece of peel ply, with the small pieces down. Next, mix the Hawk epoxy f2 filler and hawk epoxy resin catalyst until you reach a soft butter consistency.
Brush this mixture onto the beveled area of the hull and be sure to center your filler. Wipe off any extra leftover epoxy from the hull, squeegeeing out the air pockets and wiping with a clean cloth that has been dampened with solvent. This will be a lot easier than sanding it off later. Allow the patch to cure for the recommended cure time (overnight is typically sufficient) per the instructions on the hawk epoxy resin can label.
Once it has cured, remove the repair area backing on the inside of the hull. The repair area on the inside of the hull can be left untreated if it will not be exposed to sunlight. Remove blush with soap and water. Next sand off any rough areas on the outside of the hull with 80 grit sandpaper and then sand with 100 grit sandpaper the entire repair area so it is completely smooth (this may require a disc sander if it’s too difficult to sand by hand). You can dust off the area a clean cloth, air gun or brush it off with a clean brush.
F5 Light Density Fairing Filler
Prepare a batch of Hawk epoxy resin and catalyst. Apply coats to the repair area with wet epoxy, with the remainder of the Hawk epoxy resin mixed in the Hawk epoxy f5. Lightly mix filler until density is a medium thickness with no sag consistency.
Next, spread the mixture onto the repair area and squeegee the area until as smooth as possible. Allow the area to cure until you can push the corner of the squeegee into the surface and only a slight indentation remains. Repeat the process with Hawk epoxy mixed resin and f5 light density filler, adding another coat of this mixture onto the repair area. Let this cure for 10 to 12 hours.
Remove the blush with soap and water and sand the repair area with a smooth 80 grit sandpaper.
To add color, mix another small batch of Hawk epoxy and introduce the liquid dispersion as this will seal and fill any low areas. Now that you have a strong and sturdy hull side you are ready for paint!
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:
What is the best way to achieve maximum adhesion when replacing your boat’s hardware? This How To article will give you the basic knowledge you need to get your repair done correctly.
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 simple steps to follow when bonding hardware to your boat:
Sand both the surface and the hardware to get maximum adhesion.
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:
Use long strokes to spread out filler compound over the damaged hull. Apply until the mixture is slightly raised above the hull surface. Make sure the compound extends beyond the repair area.
Let cure 6 hours.
Add skim coat of F5 Filler / Epoxy compound to achieve a very smooth surface. Let cure.
Sand the repair to the desired shape with 80 grit sandpaper.
Finish by applying another 2 or 3 layers of Hawk Epoxy Resin.
The surface is ready to be painted!
Hawk Epoxy Video Tutorial
For more information see these other How To Articles:
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.
Sea Hawk Tuff Stuff Epoxy Primeris an effective water barrier and universal primer. When applied to metal hulled boats it can serve as corrosion protection below the waterline. Therefore many boaters want to have that sort of protection on their Jon boat, and apply Aluma Hawk Boat Painton top. Aluma Hawk is an aluminum boat paint that is one of the easiest and most popular paints for aluminum boats. It is a quick-dry, high-solids, corrosion-inhibiting coating designed for use on an aluminum surface without the need for additional primers. It is chromate-free and may be used above or below the waterline in fresh or saltwater environments. You can paint Aluma Hawk with a brush, roller or spray. Apply 2 coats following the proper dry time requirements. No sanding is necessary between coats of Aluma Hawk if less than 48 hours between coats. Thinning: thin if necessary with MEK.
When over-coating Tuff Stuff Epoxy Primer it is important to meet the required over coating times in order to achieve the best adhesion because temperature and humidity have a direct impact on dry times. QUICK and EASY RULE: When the coating is dry to the touch, yet still has some tack, it is ready to be over coated. Your thumb will leave a print without lifting any epoxy. This is called hot-coating. However, if the coating is completely cured (or after 24 hours) it needs to be thoroughly sanded with 80 grit sand paper to remove the shine, or you must apply another coat of Tuff Stuff within 6 days. Then you have an additional 24 hour maximum window to overcoat with paint.
These two products are great on their own, but they can do so much more when working in conjunction with each other.
When you are trying to repair a small hole in fiberglass, the best type of product to use is a premium epoxy. This will insure a proper repair and will not allow for shrinking of the material and create a water tight seal.
We recommend the Hawk Epoxy Kit. It contains the epoxy resin, catalyst and filler for the job. Watch the video below to see the steps needed to perform a small hole repair.
Below shows the comparison of the West System products to the Hawk Epoxy products. Hawk Epoxy is comparable to the West System with how it works and its uses. West System is known for A/B/C/D selection system size (Size A resin with Size A hardener) the Hawk Epoxy uses 1/2/3/4 (Size 1 resin with Size 1 catalyst). The pumps are sold separate with West System and Hawk Epoxy, this works where 1 pump of resin is mixed with 1 pump of catalyst, or more depending on instructions. This is just to make it easier and less chance for error for the customer and it doesn’t mean a 1 to 1 ratio because the pumps are calibrated differently and each pump size can distribute different amounts.
Please Note: This chart simply shows the likely equivalent product by brand. It is not recommended to mix the products brands.
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.
How to Fix a Leaking Seam or Rivet on Aluminum Boat
As aluminum boats age they show various signs of wear and tear. One of these signs may be a leaking seam or rivet. Over time, rivets can stretched and loosen, causing a gap in the hull integrity and this results in a leak. The solution to this problem is fairly simple and may be fixed at home using just a few tools and know-how. So, how should this problem be addressed?
Locate the Leaking Rivet or Seam
The first step is to find the exact seam or rivet that needs repair. To do this, put the boat in water and observe carefully. You could also put water inside the boat and see where it allows the water to escape from.
Assess the Damage
The second step is assessing the extent of damage to the rivet or seam. If the seam is too wide to be filled or caulked, it will need additional rivets in combination with a sealant product. If the damage is easily visible a sealant or caulk will be sufficient.
Choose a Sealant or Epoxy Product
There are hundreds of products out there that claim to fix leaks and seal cracks. How do you know which to choose? The Bottom Paint Store has done most of the hard work for you and can confidently recommend 2 products that really work.
If your hull is bare aluminum you can cover the entire surface with a high build epoxy primer to help seal and protect it such as Tuff Stuff. For application details see our link for application of a marine epoxy.
Hawk Epoxy is an excellent product to repair aluminum hulls. We recommend getting one of the Hawk Epoxy Kitsthat will contain everything you need for filling in the aluminum. Hawk Epoxy is a versatile product that can be used for many other application too. Everyone should own this kit! See video for mixingand selecting fillers.
Another option is G/Flex 650 Epoxymade by West System. This liquid epoxy is more flexible and versatile than regular epoxies and will adhere to almost any surface. The bond that it creates can absorb shock, vibration, expansions and contractions. It will fully cure in 24 hours. Also, West System has created a detailed and comprehensive set of instructions for a wide variety of applications. They can be found atthis linkand below:
Now that your leaky rivets and seams have been repaired, you are ready to paint! Check out this How To Articlefor more information on how to paint your aluminum vessel. Aluma Hawk is a great option or any of our antifouling copper free paintfor aluminum.
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.
See catalyst chart for mixing guidance:
The weight of MEKP is 1/125 grams per CC. 30 Drops is approximately equal to one CC (Cubic Cementer) NOTE: Using drops for catalyst is only an estimate. In Critical applications MEKP should be measure by using CC’s or Fluid Ounces which are volume measurements. The percentages in the chart: 1% thru 2% are percentages of gelcoat by weight.The CC’s and OZ’s values in the chart have been converted from weight of MEKP to volumes of MEKP.
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.
Epoxy paint is a latex acrylic substance that may have a small amount of epoxy in the mix and provide a tough, durable protective coating that’s effortless to maintain. Putting a water-based bottom paint (WBP) over a solvent based primer can be done with some modified application procedures. You do NOT want to make the window, or hot coat the water based paint over the solvent based primer such as Tuff Stuff high build marine epoxy primer. If you do, it will mud crack. So instead of putting on the WBP over the Solvent Primer in the same day, you need to wait for the primer to totally cure. Then you have to sand it with 80 grit sandpaper before apply WBP. This is a lot of extra work and very difficult to sand = extremely hard surface. So the best thing to do when using a high build solvent based epoxy is to coat it with a solvent based paint. That way you skip the extra time and labor with sanding.
Marine Epoxy systems on the bottom of bare fiberglass is the best way to protect your boat against blisters. It also provides added adhesion of the bottom paint to the hull. Here are the steps that you need to take for proper application of a marine epoxy primer (barrier coat system) to the bottom of a boat.
Preparation
Clean When painting a bare fiberglass / gel coat hull for the first time, it is extremely important that all contaminants such as grease, oil, wax, salt, or other foreign material are completed removed prior to sanding or application of a Sea Hawk System. Scrub the surface with a detergent soap and stiff bristle brush.
A. Clean and de-wax fiberglass hull with S-80 Wax N’ Grease Killersolvent based dewax. Saturate cheesecloth rag and wipe thoroughly to remove any cleaner and contaminants. Be sure to remove any residue before it dries and change rags frequently to insure contaminants are completely removed.
OR
B. Apply S-90 De-Wax Etch & Cleanerwith a maroon 3M Scotch-Brite® padscrubbing thoroughly. Do not allow cleaner to dry on the surface and remove by flushing with water.Rinse entire surface with water and check for any beading on the surface which will indicate that wax is still present. If necessary repeat step 2 again until the surface is contaminant-free. Choose your system below.
Apply Marine Epoxy Primer Seal the surface with 2-3 coats of Tuff Stuff Epoxy Primer. Apply the first coat of marine epoxy primer and allow the surface to dry to become tacky. Temperature and humidity affect the dry time, but you will know when to apply your next coat of marine epoxy primer once the paint film becomes “tacky”. You should be able to firmly press your thumb into the paint film and leave a thumbprint without any high build marine epoxy primer coming off the surface. You should use this method in between coats of marine epoxy primer and your first coat of bottom paint.
Tip: When applying marine epoxy primer over multiple days, it is always best to go overnight between coats of marine epoxy primer instead going overnight between the final coat of marine epoxy primer and the first coat of bottom paint. When over coating Tuff Stuff Epoxy Primer it is important to meet the required over coating times in order to achieve the best adhesion because temperature and humidity control dry times. It is hard to give exact times of cure. An easier rule in epoxies is when the coating is dry to the touch, yet still has some tack, it is ready to be over coated. However, if the coating is completely cured (after 24 hours) it needs to be thoroughly sanded with 80 grit sand paper to remove shine. If the marine epoxy primer is not sanded after full cure, bottom paint will not adhere.
Apply Bottom Paint to Marine Epoxy Primer Apply minimum of two coats of bottom paint. Allow 3 to 6 hours between coats and a minimum overnight dry. See the specific Technical Data Sheet for bottom paint being used. Some bottom paint may require more than 2 coats.
What is the best way to achieve maximum adhesion when replacing your boat’s hardware? This How To article will give you the basic knowledge you need to get your repair done correctly.
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 
How to Fix a Leaking Seam or Rivet on Aluminum Boat
