Aug 16
Fiberglass Boat Build Continues
posted by: Steve Jones in Fiberglass Boat on 08 16th, 2017 | | No Comments »

Now it is time to break out the fiberglass. Fiberglass resin and 1 ½ ounce mat is applied over the foam surfaces and allowed to cure. When I fiberglass over this kind of foam, I like to brush a nice thick layer of resin directly on top of the foam and then lay resin soaked pieces of mat on top of that. Like with all my projects, I allow the mat and fiberglass resin to Read the rest of this entry »

Aug 14

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.

Aug 13


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








Aug 11

A little more here regarding removing your fiberglass part from your mold.

If you waxed your mold well and applied a good coat or two of  PVA, your part should easily pop out of the mold.

The operative word in the ^^ Sentence Above ^^ is “SHOULD”!  For a better understanding of why it may not “Easily” pop out of the mold, read my previous post: Read the rest of this entry »

Aug 10

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 »

Aug 8
Fiberglass Model Build Part 7
posted by: Steve Jones in Uncategorized on 08 8th, 2017 | | No Comments »

Preparing the plug is the next stage of this build. I begin by mounting the two halves of the plug to a piece of inch thick MDF board. I attach the plugs by using screws from the back side of the MDF. Some people glue or epoxy their plugs to the parting plane. I prefer to use screws because I can remove the plug from the MDF after the mold is finished with out destroying it.

Once I have the plugs securely attached to the parting plane, I need to go around the base of the plugs looking for gaps between the board and the plugs. Any gaps are filled with clay. This is just a matter of forcing the clay into the gaps in order to prevent resin from getting under the plug. When the gaps are filled and all excess clay is removed, I can apply mold release wax to the plugs and the MDF parting plane. I like both McGuire’s and Part-All mold release waxes. It is important to apply at least five coats to the plugs in order to ensure adequate coverage. The plugs should be polished to a shiny smooth finish.

PVA is now sprayed onto the plugs and the parting board. The PVA is an excellent barrier between the mold and the plug. I like to spray a coat, let it dry and then re-apply. Applying two coats of PVA can result in lost detail but that is not a concern for me with this project. An additional coat of PVA will ensure an easy release when I de-mold the plugs.

I apply the PVA with my spray gun at about 60 psi and a distance of 8 to 12 inches. PVA is cheap and valuable at the same time. This set of mirror image plugs is now ready for molding.

For the molding process I need my air compressor and dump gun along with: tooling gelcoat, fiberglass resin and chopped mat, MEKP, rubber gloves, disposable brushes and a respirator or fume mask.

Happy Glassing


Aug 7
Fiberglass Boat Build- Keel, Hull and Sides
posted by: Steve Jones in Fiberglass Boat on 08 7th, 2017 | | No Comments »
In the post before last, I had begun to cut out pieces for the bottom portion of the hull of this boat.

As I studied the layout of the bottom of the hull, I identify the important features that I want to maintain throughout the building of this model. Obviously, an outline of the hull Read the rest of this entry »

Aug 5
Why Vacuum Bag Fiberglass Parts
posted by: Steve Jones in Fiberglass Tips & Trix on 08 5th, 2017 | | No Comments »

One way to make light, strong and clean parts is through a technique called vacuum bagging.  In general, parts made with vacuum bagging techniques show better strength and stiffness than simple molding lay-ups and they are smoother to the touch.  The strength and stiffness of vacuum bagged parts obviously comes from  Read the rest of this entry »

Aug 3
Joining Fiberglass Mold Part Halves
posted by: Steve Jones in Fiberglass Tips & Trix on 08 3rd, 2017 | | No Comments »

There are several ways to join fiberglass halves.  Fuselages, boat hulls and car bodies usually require joining of at least two pieces in order for the project to reach a point of completion.

With some applications, a sleeve can be built into the plug with will allow the second part to slip into which will result in a nice joint that can be epoxied together.  An application that comes to mind in this circumstance would be the deck of a model boat to the hull.  This technique needs to be planned well in advance since it requires Read the rest of this entry »

Aug 2
Fiberglass Fender Build Part 4
posted by: Steve Jones in Uncategorized on 08 2nd, 2017 | | No Comments »

In order to mount this plug to a parting plane, I am going to need a flexible piece of material, something that will easily follow the curve of my fender plug without causing distortion. What I ended up with is a six-inch wide piece of mahogany door skin that will act as the parting plane that will be mounted to a one inch thick, six inch wide by 36 inch long piece of MDF.

To mount the fender plug to the door skin, I used some bondo to stick wooden blocks to the inside of the fender plug and then I screwed the mahogany to the blocks. I then used my hot glue gun to attach the ends of my newly mounted plug and parting plane to the MDF. Just for visual reference, what I ended up with was similar looking to the Dunlop walk-over bridges that you see crossing over the track at automotive races.

With the plug mounted, I am ready to start the molding process. As with all plug molds, I begin by filling any and all gaps that exist between the plug and the parting plane with clay. In this case, I had no gaps so I went straight for the mold release wax. Since my parting plane is a very porous mahogany, I used 5 full coats of wax to ensure that the chances of my plug sticking to the final mold would be minimal. I allow the wax to completely dry and then apply two coats of PVA mold release and allow it to dry.

This plug is now ready for molding. Anyone who has read any of my prior blog projects knows the process that I am about to explain. I begin by mixing enough black tooling gelcoat to brush a nice thick coat over the surface of my plug and parting plane. Once this cures to a tack, I apply three layers of 1 ½ ounce fiberglass matt and fiberglass resin.

When applying the fiberglass mat and resin, I am always careful to make sure that the material has no air bubbles trapped inside. This is especially important with the corners. In this case the critical area is where the plug meets the parting plane. Remember, hurrying through this portion of the mold build will result in defects in your final product. The more defects that you have – the more repairs you will have to make to your parts.

Happy Glassing


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