May 29
Fiberglass Model Build 11 Meter RHIB
posted by: Steve Jones in Fiberglass Boat on 05 29th, 2017 | | No Comments »

To prepare this model for the molding process, the first thing I need to do is mount it onto a parting plane. My inclination is to use some nasty looking piece of scrap 1/8 inch piece of press board that I have laying around. However, since I am going to take a bunch of pictures of this process and turn it into yet another fiberglass instruction manual for my current series, I decided to use a nice looking piece of wood from the local Home Depot … Read the rest of this entry »

May 28
Fiberglass Finishing
posted by: Steve Jones in Uncategorized on 05 28th, 2017 | | No Comments »

When I first started working with fiberglass, I found it a fascinating yet frustrating material. While I enjoyed the fact that it was water proof and could be formed into any shape, I was often frustrated by my attempts to finish it in a way that would make my final product look presentable. Over the years I have come to the realization that a nice fiberglass finish requires a little preparation and a little improvising.

Obtaining a nice smooth finish can be obtained on a consistent basis when using a mold to produce your parts. Even so, thought and preparation are still necessary. A nice thick gelcoat layer that is covered with a layer of veil that is then covered with a layer of chopped mat will create an end product with a nice finish and no pattern transfer to the final product. The gelcoat layer should be thick enough to allow light sanding without getting into the mat.

When repairing a broken piece of fiberglass, getting a smooth finish takes a little more work. On painted surfaces, I like to remove the paint around the damaged area with sandpaper. Depending on the size of the damaged area, I like to remove enough paint around the damaged area to give me a couple inches of working room. I will then tape over the finished side of the damaged area and apply my repair to the backside of the repair.

Once the resin has cured, I remove the tape and access the exterior of my repair. If the repair is flush or depressed, I will smooth over the surface with either bondo, finishing putty or a thick mixture of resin and cabosil. Once this has cured, I will sand it smooth, primer it, inspect it and go from there. If there are defects in the surface, I will refill them with the medium that I find appropriate and repeat the sanding, inspecting and primering that I had done before. This process continues until the finish is right.

You should not be afraid to sand fiberglass. If you happen to sand it to the point that you expose glass fibers, clip the long ones off and brush more catalyzed resin on. Let the resin cure and re-sand. You may have to repeat this process several times to get your repair right. If your sanding continues to expose fibers, you may want to cut the surface down an 1/8 of an inch or so and fill over the surface with either gelcoat, resin mixed with cabosil or even bondo. Once this has cured you will have plenty of room to shape and sand without exposing fibers.

The bottom line is that many people feel as though the final outer surface of a fiberglass repair must be fiberglass. This is nice if possible, but there is nothing wrong with smoothing over the outer skin of a fiberglass repair with gelcoat, bondo, resin mixed with cabosil or body putty.

Fiberglass Shooting Star Body (Speed Racer) For RC Car

Happy Glassing


May 25


To begin laying up a fender, I mix about a half a cup of gelcoat with the recommended amount of hardener.  Once this is thoroughly mixed, I use a disposable chip brush to paint the gelcoat into the mold.  I try to get a heavy layer of consistent thickness.  This gelcoat needs to cure to a tackiness before I apply the fiberglass mat and resin.  Usually this takes about 45 minutes. 


While I am waiting for the gelcoat to cure a bit, I begin to prepare for the next steps of this process by tearing 1 ½ ounce mat into small pieces that will be easy to lay into my mold.  Since this is a fender, it has compound curves – one that goes side to side and one that goes front to back.  In my experience, smaller pieces of mat are easier to work with in a mold like this.  Just FYI, my pieces of mat are approximately 4” X 4”.


Now that the gelcoat has cured to a tack, I mix an 8 ounce cup of resin and catalyst (as directed by the manufacturer) and begin to work my way around the inside of the mold with resin and mat.  I soak a chip brush with resin and use it to blot the resin onto the mat over my freshly applied gelcoat.  Since the gelcoat is still tacky to the touch, it holds the mat in place while I soak it with resin.  I work my way from one end of the fender to the other and then back again (two layers of mat and resin) being careful to make sure that the mat has no air trapped underneath and that the mat overhangs the mold by an inch or so.


Once this mat and resin cure to a gel-like state (this takes about ½ hour of 45 minutes) you can safely trim the overhanging extra mat with a razor knife.  If the resin pulls or is too sticky to cut, check back in another 15 minutes and try it again.  This is the best way to clean up your parts of excess fiberglass.


After trimming, I allow the part to sit in the mold for a day or so to let it fully cure.  Once fully cured, I pop the part from the mold using a couple of plastic putty spreaders.  I simply use my fingers to pick at the part until I get slight separation from the mold then I push the plastic spreader between the part and the mold and work my way around until the part pops out.  Since I used adequate release wax and two coats of PVA, this part easily separated from the mold.  One fender down, one to go!  

My New Beach Cruiser With Fiberglass Fenders Installed

My New Beach Cruiser With Fiberglass Fenders Installed








May 23
Building Fiberglass Fenders: Part III
posted by: Steve Jones in Fiberglass Fender Project on 05 23rd, 2017 | | No Comments »

With the recent application of bondo leveled and cured, I can now smooth out the surface of my fender – again. As it turned out, the two outer thirds of the circumference of my fender were about the same height. The middle section was about ¼ to 1/3 inch on the shallow side. It is in this center section that I need to reshape the fender around my newly formed ridge of bondo. I accomplish this with more bondo and a credit card that I use as a spreader. I like using credit cards or other thin pieces of plastic as spreaders because they can be used to produce a flat smooth surface or a nice smooth curved surface. Read the rest of this entry »

May 22

With the keel and the hull sides attached, I can think about filling the hull with foam and carving out the bottom of the hull. As I study the hull bottom as it sits, I notice that the hull sides have some waves in them. Since it is much easier to fix this now, I go ahead and glue then clamp some thin pine strips along the inside of the hull sides about ½ inch below the upper edge. This strip will also help me with the construction of the hull bottom. Once these extra hull pieces are secure, I measure and cut Read the rest of this entry »

May 20

Recently I had my first really bad experience with making a mold for a plug that I built.  This was a big disappointment for me.  I had spent about eight weeks building a model of a Porsche 917K body in 1/10 scale that I intended to mold then reproduce.  My model was built to fit a Tamiya TT-01 R/C car chassis.  I had looked for months on the Internet for a 1/10 scale R/C body of this car with no luck so I decided to make my own. Read the rest of this entry »

May 18
Fiberglass Reproduction License Plates
posted by: Steve Jones in Fiberglass Tips & Trix on 05 18th, 2017 | | No Comments »

In the post prior to this one I had just started to get into the benefits of using silicone for a mold for a fiberglass project like this one.

First of all, silicone doesn’t smell and it doesn’t stick to anything other than itself.  With silicone I would never have to worry about ruining the original like I did with my first effort with building a fiberglass mold.  Secondly, there is no need for parting agents like wax or PVA – pieces simply effortlessly pull right out of silicone molds.

So, let’s get started.  The process of mounting the plate to a parting plane remains the same expect for the fact that I want the silicone mold to be little deeper than the fiberglass mold so I am mounting the plate to a ¼ inch piece of MDF that I traced the plate onto and cut out with my scrolling saw.  This ¼ piece of MDF is then glued to a parting plane and the plate is secured to the MDF with wood screws.

The pieces of the parting plane with the plate.

1/4 inch mdf glued to parting plane.

Aligning the plate to the parting plane with clamps.

Plate screwed to the parting plane.

The next step is to seal the edges of the plate with clay to prevent the silicone from getting in between the plate and the MDF.

Now I use 1 X 1 pine to build a perimeter around the plate that will act as a wall that will contain the silicone.  I leave about a ¼ gap between the plate and the pine perimeter that will define the boundaries of the mold.  At this point I go around the outside of the pine with masking tape to prevent any silicone from leaking out.

Sides of the mold clamped in place and Silicon at the ready.

With the plate prepared I go ahead and mix some silicon with its curing agent and pour it over the plate.  I make sure that there is enough silicon to completely cover the plate with about a ¼ inch depth.  The next step is the easiest of all – let it stand for 24 hours.

Silicon is flowing.

The silicon is curing – will be ready in 24 hours.

More on this project soon!

Happy Glassing


May 15

I have a bit of experience working with silicon molds so as expected, the mold cures perfectly and peals easily from the parting plane and the plate.  Oddly enough, the mold removed some rusted paint flecks from the plate – oh well!


With a perfect mold I go ahead and load it up with a layer of gel coat and a few layers of resin and mat.  Since this process is covered completely in the fiberglass mold manuals I won’t do too much detail on this except for re-hashing the differences between a fiberglass mold and a silicon mold.


When using a silicon mold you have to make sure that the mold is sitting on a flat surface – if the surface is curved your mold will be curved as will your final parts.  The other major difference here is that the silicon needs no prior preparation before making parts.  Simply apply gel coat, fiberglass mat and resin into the mold – no need for mold release wax or PVA.


Mold ready for Gel Coat


With a layer of Gel Coat applied I can now lay a resin and mat.


Plate is removed from the mold about 24 hrs later and is ready for paint.


This was a very simple process and in the case of duplicating a flat object like this license plate was much easier than using a traditional fiberglass mold.  Please email me at should you have any questions regarding plate duplication.

May 14
Fiberglass Copter Build Part 8
posted by: Steve Jones in Uncategorized on 05 14th, 2017 | | No Comments »

I begin by applying black tooling gelcoat with a dump gun at about 80 psi. I make sure to keep the gun close to my work because gelcoat makes a huge mess if it gets on something other than your project. I lay down a nice thick layer of gelcoat making sure to get good coverage around the base where the plug meets the board.

Once the plug is covered with gelcoat, I let it cure to a tack. I did this project on a nice hot San Diego day so it cured to a tack in about 45 minutes.

At this step I used a different approach than I am used to. I came into possession of a large roll of veil that I decided to use in the corners and angles of the mold. In the past I have always used a combination of cabosil and resin. I found the veil easy to work with, especially when pushing it into corners with a chip brush. With the veil in place, I proceed to build the mold with three layers of 1 ½ ounce chopped mat.

I begin applying the chopped mat by brushing a nice thick layer of catalyzed resin over the area of the plug that I am working on. Then I place a piece of mat that has been pulled off of my roll and lay it on the plug. I like to keep the pieces fairly small on a project like this, no larger than 6 inches square. Pulling the mat apart will leave many loose fibers that will help the strength of my final product once it has cured. When applying the mat, I like to overlap my pieces by about 20% and build a nice flange around the base of the plug.

Happy Glassing


May 13

Ask any group of composites fabricators, and it is quickly apparent that everyone has encountered a problem with sticking a part in a new mold. It is just a fact of life in the open molding business, that on occasion a new mold will stick the initial part, regardless of the  Read the rest of this entry »

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