Customer Spotlight: Beginner making a mold, fender and splitter.

I want to thank Steve at Venom Racing for sending in some photos and a write up of his experience as a first time fabricator of fiberglass parts.  He has been ordering from us since last year and I asked him for some photos of his work.  The write up below is two emails that he sent me.

Email #1

My rear fender flare project was a great learning experience since I started with no composite experience at all. I only did them to prove to myself that I could I do it but I won’t be using these or this design on the car.

I still have much to learn and maybe this winter I’ll take another crack at them. The second project was teaching myself how to do resin infusion because I needed to make a new front splitter. Again, great learning experience but still much to learn.



This was taken just after de-molding and a rough trim, hence the unevenness and leftover infusion mesh in spots. Far from perfect and I probably should’ve practiced more with vacuum bagging before attempting to make something this large but I ran out of time and I needed to just get it done.


Mounted to the new front clip of the car.


Email #2

I will say that fender flare was my 3rd version of it.  My plug failed on my first attempt before I ever got to fiberglassing.  The second version went better but I didn’t like the shape after I took a mold from the plug.  This 3rd version was a last ditch effort that I did just before I had to pack up all my fiberglassing stuff to have access to the rest of the car for different projects that needed to get done.  Once I finished those other projects, the car went off to a fabricator for a while and I started on the front splitter.  The splitter I showed you below was my second attempt.  I started the splitter project knowing I was going to make 2 different versions just in case something happened and I made 4 small flat test panels just to get a feel for how the process worked.  The first version of the splitter was simpler in design for the air-ducts but unfortunately the infusion mesh shifted once the infusion started and the mesh pierced the bag all over the place.  I did the best I could to salvage it during the rest of the infusion process but it was a lost cause and an expensive mistake.  After learning my lesson on the first attempt, the second attempt went better but still not great.  I ended up with a spot on the lower bottom that didn’t get any resin and so I then learned how to make repairs to CF.  I ground out the bad spot and laid in a patch.  Since it was going to be on the bottom of the car having the look of a “patch” didn’t matter.

As a first timer on both of these projects I had to accept that I would make mistakes and that it wouldn’t be perfect.  Once I accepted that and came to grips with taking on such massive first time projects, it was a lot of fun and I learned a lot.  When I started 8 months ago, I knew nothing about the different types of resins, types of cloths, weave patterns let alone gelcoats, release agents or how to make a plug.  Now I at least have a basic understanding of them and the confidence to make my own small fiberglass or CF repairs.  And when I get the time, I’ll have another go at these larger projects.

Great job Steve!


Vacuum Bagging Pumps and Fittings

Vacuum bagging adds more time and money to your laminate but will provide you with high quality parts.  In this segment we will discuss some of the fittings that are needed in the vacuum bagging process.


Vacuum Pump-The most important part needed when vacuum bagging is a pump.  There are many pumps on the market that vary in price.  It is definitely an investment.  There are ones specifically for large applications and ones that are meant for medium to small applications. The pumps have different styles (diaphragm, rotary vane, oil bath, piston etc.), motor horse powers and CFMs (cubic feet per minute). You will  need to evaluate your project to see which pump will work best for you.


Vacuum Port/Coupling– Used to connect your bag with the vacuum tubing. A small slit is made in the bag so the port can be placed. Sealant tape can be used to seal off any excess gaps that may exist. The connection must be as tight as possible to prevent  air leaks. There are ports that come in one and two parts.


Vacuum tubing– Tubing is most often sold by the foot. It is  used to connect the bag and port to the vacuum pump. It can be cut to size. Check to make sure the opening in the tubing matches the opening on the port and fittings.


Vacuum gauge– This part is optional but can be very important in your application. It helps you detect if there is an air leak. It also allows you to measure the air pressure at all times. This is good to know not only for the current part but also so you can replicate the process on future parts.  A T-attachment should be used with the vacuum gauge if it doesn’t already come with one.


Vacuum regulator-Regulate the amount of pressure used on the part.  There are times when you may want less pressure than other times, such as before the laminate has gelled. A full vacuum could cause too much resin to be pulled out. A vacuum regulator usually comes with a vacuum gauge so you don’t have to buy one separately.


Hose Barb– This is optional. It can be used to connect the vacuum hose/tubing to the vacuum equipment.

You can also use a resin trap or create your own.  Their are several on the market or you could make one out of a sealed jar.  You would just need to add fittings to the lid. A relief valve may be necessary as well.  You can pick up one from Home Depot.

Vacuum bagging can be really simple or really complicated depending on what you need.  Start simple and practice on small parts. You can decide as time goes on if you need some of the extras.

Next we will be posting basic instructions on the vacuum bagging process. Stay tuned.




Customer Spotlight: 621cycles’s Motorcycle trunk

Dave at 621 Cycles shared some great photos with us of some products he made using our chopped strand mat. Here is what he had to say,

1 oz mat 621 cycles

“Now using CSM exclusively from Fiberglass Warehouse. Much more consistent density. Here’s a few pics from the shop of the 1oz CSM being used in motorcycle trunks and chin spoilers… Thanks to Dallin for all of his help!”

621 cycles

621 cycles motorcycle trunk

finished motorcycle trunk1

finished motorcycle trunk inside

trimmed up and added wooden frame

“Here’s a new mold I laid up on one of my plugs, with 5 layers of 1.5oz CSM from Fiberglass Warehouse… Solid as a rock!”

buffed out mold

“..and buffed it out. Making parts in it every day.”

finished motorcycle trunk

“1.5oz CSM used in a larger motorcycle trunk, more thanks to Dallin…and the finished unit…”

Thanks for sharing Dave.  It is fun to see your customer projects. To see more of 621 cycles products, go to

Vacuum Bagging Materials

vacuum bagging

Vacuum bagging is worth the extra time and money when you have a part that needs to be low in weight and high in strength. Vacuum bagging provides an even pressure to the entire laminate. If done right, this will give the part a better fiber to resin ratio when compared to hand layup. It will also remove air bubbles creating a void free laminate.

There are several materials needed in a bagging schedule. These include peel ply and/or release film, breather/bleeder, vacuum bagging film and rubberized sealant tape.

peel ply

Peel Ply is a woven fabric coated with a release agent that leaves a even textured surface.  This surface minimizes prep time for secondary bonding on your part. Perforated/porous peel ply allows excess resin to seep through. A non-porous peel ply is used when it is not necessary for resin bleed but there is a need to get rid of volatiles and solvents. Peel ply can be used with or with out release film.

release film

Release film comes in both porous and non-porous form. You need release film or peel ply so that the breather/bleeder and vacuum bag do not stick to your part. It acts like a barrier between them. Release film is similar to peel ply but it leaves a smooth finish instead. Release film also does not bleed as much as peel ply.  It can be used between peel ply and the breather to lower the amount of resin that is absorbed by the fabric. This will make it  more likely that you will be able to reuse the bleeder/breather fabric. Release film that is porous, has small pin holes that are equidistant from each other. Non-porous release film allows the resin to remain on the surface of the part which gives it a smooth finish. This smooth finish will be ready for paint.

Both release film and peel ply help keep foreign materials such as dust off the finished part.

breather bleeder

Breather/Bleeder is a synthetic fiber material (like quilt filling fabric) that absorbs any excess resin from the laminate. It comes in several different thicknesses. Breather/bleeder controls the air flow as it goes through the bag as well. It should also be used where the vacuum fittings/port connects to the bag and laminate flanges.  This is so that resin does not get sucked up into the vacuum. It acts as a resin trap.

bagging film

Bagging film is what is used to make your vacuum bag. You will need it to be much larger than your laminate and also bigger than the area you put sealant tape on. It comes in various materials including nylon.

sealant tape

Sealant tape is a must.  We do not recommend using masking or some other type of tape. It is used to close bagging film to the flange of the mold/part or to itself.

There are other vacuum bagging materials on the market but these are the ones used most often.  You can achieve a great looking part with these.

In the next few weeks, we will be doing a post on pumps and fittings and also the vacuum bagging process.




Mixing Pigments with Gel Coat or Resin

mixing pigments

If you have a small repair that you need to color match or you want to create your own color for a project, pigments may be the best way to go.


Pigments can be used to tint polyester resin, vinyl ester resin, epoxy resins and gel coats. There are many colors out on the market.  You can mix a pigment alone or mix with several different colors to create your own color.

liquid concentrate pigment1

We are using an opaque or solid color.  It is a liquid concentrate.

If you add color to a white gel coat, it is going to be more pastel and light colored.  If you are looking for a deeper, richer color, you will want to use a neutral based gel coat or resin.

mixing pigment1

You should mix the pigment with the resin before adding the catalyst. The recommended mix ratio is 6-8% by weight.  You can add up to 10%. We added 5 grams of pigment to 2 ounces of white gel coat. Use a scale to help measure.

Thoroughly mix the pigment and resin so that there will be no weak areas in the end. Scrape down the sides many times and stir until all streaks are gone.

Once the pigment is thoroughly mixed in, add the catalyst.   You can add it between 1 and 2%.  If you are using epoxy resin, it will be the B side.  You will want to follow the instructions on mixing your epoxy based on the mix ratio. Stir completely again.

mixed pigment

You can see in the above picture that the red oxide pigment mixed with white gel coat came out a pastel color.  It made a salmon color which is what we were trying to achieve.  Again, if you are looking for a richer, darker color, you will want to mix your pigment with a neutral based gel coat or resin.

For more information, visit our website at .


Casting with a Two Part Polyurethane

We have a YouTube video that shows the process of casting with a two part polyurethane liquid plastic in a silicone mold.  If you prefer to read about it, then this post is for you.

polyurethane casting supplies

In this demonstration we used a rigid polyurethane in the silicone mold we showed in a previous post.  You can read about making a silicone mold here.

The supplies you will need-

-Silicone mold

Two part polyurethane liquid plastic

-A mold release if you want to preserve your mold for multiple casts

-Stir paddle or a paint mixer attachment for a drill (purchased at Home Depot).

-Rubber bands or tape to hold the silicone mold together.

polyurethane sharkthane

SharkThane 70-20 is a two part polyurethane with a 1:1 mixing ratio. The shore hardness of the cured material is 70D. The finished product will be very hard.  It creates a white cast with almost no air bubbles.


First, add mold release (if you want).  It is not necessary but your mold will last longer.

Next, you will want to use something to hold your silicone mold together such as rubber bands or tape.

The polyurethane in this demonstration is a 1:1 mix ratio. Measure out equal amounts of part A and then part B. Figure out how much you will need to fill the mold beforehand.

A stir stick can be used to mix the two parts together.  Also, a paint mixer could be used to speed up the mixing time.  If you choose to use a paint mixer,  be VERY careful because it can create air bubbles. The paint mixer needs to be submerged in the liquid before turning it on.  If you have a vacuum pump, suction out the air bubbles before pouring in the mold. DO NOT use a paint mixer with more flexible polyurethanes as it will introduce way too many air bubbles into the mixture. But for the 70-20, it worked fine.

Mix quickly, as the polyurethane will start to gel between 90 to 120 seconds.

If you have a large part, use several smaller batches.  If you don’t work in smaller batches, the polyurethane may cure before it is poured into the mold.

Pour the polyurethane slowly into the mold to allow air bubbles to work themselves up to the top. Within a minute or two you will see the polyurethane turn white as it gels.   The polyurethane exotherms, meaning it heats up, as the polyurethane starts to cure.

gelled polyurethane

Here is the leftover polyurethane cured in the mixing cup.

The handling cure time is 30-40 minutes.

Work the cast out of the mold once it comes to room temperature.

polyurethane cast

Here is the finished product including the polyurethane that gelled inside the cup.

Fully cured castings made with rigid polyurethane, are tough, durable, machinable and paintable.  This make it perfect for point-of-purchase displays, rapid prototypes, special effects and sculpture reproductions.



Laminating Fiberglass Cloth to Plywood

***Before you start, always remember to wear safety equipment. Working with fiberglass can be hazardous. Safety glasses, latex or vinyl gloves, and a respirator are all important to keeping you safe from the fiberglass and resin. To protect your skin and clothes, wear Tyvek coveralls. Also, you need to work in a well ventilated area.

surface prep

The first and most important step in laminating (after exercising safety) is surface preparation. Do not skip this step. Use Acetone to wipe down the area that is to be laminated. This removes any dust and grease from the surface.

cutting fiberglass

Cut the fiberglass cloth so that it is a little bigger than the surface that is to be laminated. There are differing of opinions on whether you should cut the fiberglass to the exact shape or if you should cut it a little larger.  We prefer it to be a little bigger. This allows you to fully cover the area to be laminated without worrying about distorting the fiberglass around the edges.

polyester resin

You can use a general purpose laminating resin to laminate the fiberglass to the plywood.  It is used for general fiberglass applications. It cures with a surface tack which helps the multiple layers adhere well to each other.  It also holds the reinforcement in place.  Another benefit to the surface tack is that it is not necessary to sand between layers.  On your final layer, wax can be added (surface agent or surface seal) to the resin.  

laminating resin 

We measured out 2 ounces of the resin. You can measure out how ever much you need. Next, you will want to use a catalyst quantity chart to figure out how much MEKP you will need to add to the polyester resin.

Catalyst Large Quantity Chart1

To add 1% MEKP to 2 ounces of polyester resin, we needed 18 drops of MEKP. The amounts of polyester resin/MEKP does not need to be quite as exact as it would need to be when working with epoxy resin.

Using a stir stick, thoroughly mix the resin and MEKP for several minutes. For large quantities, use a power mixer and a drill to speed up the process.

Pour a little bit of resin onto your plywood. Using a throw away brush or spreader, spread the resin until it covers the desired surface and there is a nice thin layer of resin on your plywood.

Some people let this layer cure as a pre-coat. The pre-coat will seal the wood. The benefits of this layer is that once it is cured, additional resin will not soak into the wood. It will also help to prevent air bubbles. The downside is that the extra resin will add weight and it will take an extra day to complete your project.

Once you have applied the thin layer of resin to the plywood, place your fiberglass cloth onto it and allow the resin to soak into the cloth.


It will not completely wet it out so add a little more resin. Again, use your disposable brush or spreader to spread the resin. You can also use an aluminum roller to help completely wet out the cloth and remove any trapped air bubbles

Once you do not see any more white from the fiberglass cloth, you know there is plenty of resin. If you see thick spots of resin, you can use your brush or spreader to squeegee it off. You do not want to leave too much resin on your laminate or it will be brittle. But if you leave too little, the part will be weak.

Now you let it cure.

trim excess

During the “green stage’, which is after the resin has gelled but before it is fully cured, you can cut off the excess fiberglass. You can do this with a razor blade.

finished laminate

Here is the finished laminate. It is hard and fully cured.

cured resin1

You can also check your left over resin. It should be hard and easily removed from the plastic container. If the resin is hard in some places and sticky in others, the resin was not thoroughly mixed.

For more how to’s, information and products go to .



Breakdown of Different Fiberglass Cloths

Fiberglass cloth, also known as fiberglass fabric, is an excellent choice when you are looking for a strong, light weight part.

All of our fabrics must be used with a resin system (polyester, vinyl ester or epoxy) to create a composite part. The fiberglass is what gives any part it’s strength. It is used in a great variety of applications.  Boats, bathtubs, wind turbines, RC, surfboards, kayaks, canoes, aerospace . The list could go on and on.

The fabrics we have can be separated into 4 popular categories-

  1. RC
  2. Boat/marine
  3. Aerospace
  4. Surfboard

Keep in mind that these different fabrics are not limited in their category.  They can be used in a variety of projects.

The RC cloth is style #106 and #108,


Style #106 is a .75 oz. cloth. It is very lightweight and most often used on model airplanes. Because it is so lightweight, it can be tricky to use. You will want to use protective latex gloves or some other kind of smooth gloves. Any kind of skin tag will catch on the fabric. Style #106 is stronger than mylar. You don’t want to use it on anything requiring strength though.


Style #108 is another RC cloth. It is 1.5 oz. You will still need to be careful when working with this fabric but it is stronger than the .75 oz.

Style #1522 and #3733 are our most common surfboard cloths.  They can also be used on canoes, kayaks and boats


Style #1522 is a nice, smooth 4oz. cloth. Surfboard hobbyists use it to coat foam core.  It can also be used as a surfacing layer. It creates a clear, transparent laminate when saturated with resin.  This cloth wets out easily.


Style #3733 is a 5.6oz., aka sailboat cloth. This cloth is typically used on surfboards and general purpose projects.

Style #120 and #7781 are mainly used in the aerospace industry.


Style #120 is 3.2 oz. It is a 1:6 scale cloth for RC airplanes. You want to use this fabric when strength is needed. It is used on RC racing planes that go up to 140mph. This style is aerospace grade.


Style #7781 is an 8.9oz., four harness satin weave. Four harness means there is a three by one interfacing where a filling yarn floats over three warp yarns and under one. This weave conforms to curved surfaces. It is aerospace grade and is the second most popular aerospace cloth behind style #120.

Styles 7532 and 7500 fall in the boat/marine category.


Style #7532 is a 7.5oz. cloth. It is more commonly known as an 8oz. cloth. It is a  popular boat cloth. It is a plain weave and is stronger and sturdier than the 6oz. It is often used for waterproofing boat decks.


Style #7500 is the most popular general purpose fabric and also a great boat making cloth.  It is widely used in the fiberglass industry. It is good for making molds. It is typically used after the mat layer in a mold.  It gives it strength. It is also used in boat construction and repair.


We also carry fiberglass tape in widths from 1” to 12”.  They are 50 yard rolls.  They have selvage edges that keep it from un-ravelling. They do not have an adhesive backing.  Just like our regular fabrics, they are meant to be used with resin. Our tapes work great on smaller applications and if you will be winding. They are also often used on glass seams and in repair work.

All of our fabrics are pretty easy to handle. Remember you will want to pick the best weight of fabric for your project but you will also want it to be strong enough.

To see all of the products we have available, go to .