Self-made "FRP bracket" using aluminum angle material as a mold!

Mr. Itabashi of Model Create Maxi explained introductory FRP crafting techniques in an easy-to-understand manner. Let's make our ownFRP bracket in the shape of an angle by using an aluminum angle material as a "mold. Since it is an angle-shaped bracket, it is easy to process it into a mold. Therefore, depending on your ideas, you can make a bracket that can be used for various purposes!

⚫︎ Interview supported by: Model Create Maxi

Let's go ahead and "cut out the fiberglass" to be used for tensioning!

The angle material that served as the mold is a 25 mm wide product sold at home centers. The smooth surface gives the impression of being easy to demold, but the basic rule of thumb is to apply a good mold-release wax treatment.

Before mixing the polyester resin and hardener, the first step that must be taken is to cut the glass fibers to be attached. If the resin is mixed first, there is no time to spare.

Use the resin as an "adhesive" after mixing!

After the glass fiber cutting is done, let's measure and mix the polyester resin at this stage. We used a "non-paraffin resin" that does not contain paraffin. The mixing ratio is 100 resin to 1 hardener.

Poly resin mixed with a hardener is applied to the inside of the angle material that has been waxed with mold release wax (in this case, the female mold). This coated resin acts as an adhesive and improves the tracking of the fiberglass.

The first layer of glass fiber is placed on the female angle material, and poly resin is soaked into the glass fibers while pressing down with a brush. 90-degree angles are easily achieved.

The fiberglass is applied in two or three layers. For a thicker finish, more plies can be used.

Tighten with a "small chako man" to squeeze out the unwanted resin.

The male mold is pressed against the tensioned angle material and tightened using a small "chako ten thousand" to squeeze out the unwanted resin. The surface of the male mold should also be treated with release wax for demolding.

The mold was held in place with two small Chaco 10,000s. This squeezes out the poly resin that has soaked into the mold more than necessary, making it possible to create lighter weight and denser products at the same time. Let's get rid of the wasted resin.

For example, let's apply R processing to the outer corner (right angle apex) of a male mold. The inside of the product will be R-shaped instead of right-angled, resulting in a high-strength construction. FRP parts can evolve with a little work and ideas.

The parts can be demolded after about an hour of temporary curing. However, to ensure more stable strength, it is better to leave the mold pressed for at least half a day or overnight to dry.

Homemade FRP bracket in the shape of an L-shaped angle is completed.

Once the chaco vise is removed, insert a flat-blade screwdriver into the gap between the male and female molds, and with a quick twist, demold the product from the mold it was pressed against. After the product is completely dry, it will snap out of the mold.

What remains on the female mold is the FRP part that was fabricated by tensioning. At this stage, the parts are not trimmed, so the shape is not perfect, but by cutting the unnecessary parts, the shape can be made exactly as desired.

Trimming the outer perimeter completes the L-shaped 90-degree angle bracket material. If the material is not dried properly, it will become elastic, and if it is twisted, the resin will break down and turn white. Complete drying is important.

FRP work can be easily enjoyed by mixing polyester resin and hardener and applying the mixture. Because of the impression that FRP work is easy and enjoyable, there are actually many cases where the wrong work procedures are used. In fact, there are many cases in which the wrong work procedures are followed. Mr. Itabashi of Model Create Maxi says that he has seen many cases in the past where he thought, "If I had followed the basics and proceeded faithfully, I could have made a better product!Mr. Itabashi, who gave us a lecture on FRP construction this time, has abundant experience participating in mini bike endurance races and Sunday races. At circuits, he sometimes sees details of original machines with self-made FRP parts, but he sometimes has the impression that "you can see how rushed and hurried he is in his work. ......The most important factors are the choice of polyresin and the mixing ratio of polyresin and hardener. The resins that are easy to handle for overlays are paraffin-free, commonly known as "non-paraffin" resins. Non-paraffin resins are also said to facilitate later repair work. The basic mixing ratio of hardener is "100 to 1," and the mixing ratio may be fine-tuned when working in cold winters or in humid environments. However, he says that it is only a very small adjustment.If more poly resin is soaked than necessary, the strength of the part will be significantly reduced and the finished product will be heavier. Even if the thickness is secured with resin, the part will not be strong enough and will end up being heavy.Here, we used a "male-female mold" made of aluminum angle material. By tightening the mold after tensioning (in this case, using a small Shako vise), excess resin can be overflowed to create a dense FRP product. As a supplement, if you want to make a stronger part, you can increase the thickness of only the 90-degree angle part by applying "R processing" to the 90-degree protruding corner of the male mold (by shaving with a file, etc.).Since the cross section of the product will be R instead of 90 degrees, glass fiber can be added only to this section, easily increasing the strength of the product. Also, by drilling or cutting the mold before tensioning, it is possible to reflect the shape of the mold in the product.In addition, by following the same procedure as in the present project, original parts made of semi-dry carbon can be made by using carbon fibers, applying epoxy-based heat-resistant resin, and forcibly drying them in a "simple oven". We hope that more Sunday mechanics will give FRP crafting a try, as it can be more enjoyable than you can imagine, even if it is just the realization of an idea.

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Self-made "FRP bracket" using aluminum angle material as a mold!

2026.2.12

Mr. Itabashi of Model Create Maxi explained introductory FRP crafting techniques in an easy-to-understand manner. Let's make our ownFRP bracket in the...