Composite Military Helmet Replica

Many people like to use old military helmets for various purposes. I use it at aircombat competitions with radio controlled scaled aircraft models from WWI 1:8 and WWII 1:12.
Helmets are obligatory, as fast RC airplanes can go out of control when they crash in the air. Since our sport includes airplanes from the wars, many of us choose to use helmets from the same historic times. I have been using an original M59/M85 Yugoslav Combat helmet for years. But the problem with originals from that era is, they are made of metal and so heavy to wear for the whole day events. They also get pretty warm on the summer sun.

This is what this instructable is about. Making replicas of old military helmets from modern materials. Composites of different fibers (carbon, glass, aramid, basalt) and epoxy resin are strong and lightweight. Real nowadays military helmets are also mostly made of Kevlar/aramid composits.

You will need:
-a mold (more about in the next step)
-PVA or other mold release agent
-epoxy resin (about 40min open time)
-glass/carbon/kevlar(aramid)/basalt fiber cloth
-spray putty
-sandpaper
-paint or varnish (I used 2k car paint)
-nylon belt and holders
-nylon belt clips
-some tools (including sewing machine)

Because there is not* gonna be a video about this project. But this one includes "how to cut aramid/kevlar" and some other useful information.

This instructable is not about mold making, but you do need one to proceed to the next step, so let's see what the options are. I have to say I did not make the mold I used, but borrowed it. When I started asking around who has it I found out 3 of my friends have such molds, so I picked one and start working. The one I got was the German one - don't know the exact M number, maybe somebody else knows and can let me know in the comments.

If you don't find anybody to borrow it there are 2 ways to make it. The most common one is to make the mold over an original helmet out of composite. The second option is to 3D print it. There is some more afterwork for finishing the surface, but with 3D printers being better every day it is not that much of work anymore.

In the pictures you can see the white mold I used. This one is made out of composits over an original helmet. The grey/red one is a 3D printed version that my friend Aljaž N. built. Thanks to him for sharing his photos so you can see how this should be done.

Applying mold release is the most important part before the start. It prevents the mold and the final product to stick together. I used 2 layers of mold release wax + 1 layer of PVA.
The PVA needs to be completely dry before the next step.

Getting the product out of the mold can be tricky sometimes, but what worked out the best for me was blowing compressed air (8 bar) into the side between the mold and the product. Blow all around and eventually it will jump out.

The first helmet's outer layers are made of carbon, but inside it is mixed materials. Carbon is known to be strong and lightweight, but it can be sharp if it cracks. First you need to cut pieces of cloth. The first carbon (after the initial 80g glass) is visible, so it should be nicely cut in the shape you want. I couldn't place the cloth inside in one piece because of the helmet's shape. Each layer must be completely soaked in epoxy resin. I like to use the epoxy with 40min open time with mixing ratio 100:40 but any epoxy that is slow enough to let you finish the job is ok.
The helmet #1 is made from the following layers:
-80g glass
-160g carbon
-220g basalt (cheap carbon)
-220g Kevlar/aramid (inside only, it should not get to the edge, as it is hard to cut and sand)
-220g basalt
-220g basalt
-160g carbon

It needed about 250g of epoxy to fully soak all of the above layers.

Before you take it out heat up the product including the mold ta about 50°C for at least 3-5h. This will make the epoxy resin reach it's final strength. (more about my DIY heat comora in the video above)

Got the #1 carbon look out of the mold. Looks good for a start. More about the finishing process will follow.

Kevlar/aramid is known to be "bulletproof". This is the strongest of all three helmets. The only problem here: Kevlar is extremeley hard to cut. But there is a trick so you don't need to buy expensive scissors.
Take some solid quality scissors and sand the edges of them with an angle grinder like if you wanted to damage them. This will create small notches that will hold the fiber while the blade will cut it.

This one is made of:
-80g glass
-300g Kevlar
-300g Kevlar
-240g glass
-240g glass

This one also needed about 250g of epoxy.

Basalt fiber characteristics are somewhere between glass and carbon. It is also cheap, but the look is not as nice as carbon. There is no special reason why I did 3 of them form the layers mentioned. It is more about the first and last layer that are visible. I did a mix of materials depending on what I had available. All of them are strong enough.

This one is from:
-80g glass
-220g basalt
-160g carbon
-220g Kevlar (inside only)
-220g basalt
-220g basalt

This one took about 220g of epoxy.

Cutting the edge should be done with a diamond wheel. Dremel 545 is a good example.
Carbon, basalt and glass are easy to cut with such wheel. Kevlar/aramid is a different story, but it is possible to do it slowly.

Sanding should be done with differend sandpapers. Start with about 150 and finish above 1000. Best is to do it under water.

Except for the carbon look one that is finished only with transparent polyurethane car varnish (many layers), the others are first sprayed with putty (spray filler). This shows all the mistakes that you need to sand.

Painting - sanding - painting is a long process. You should repeat it until you get rid of all the mistakes.
I used the airbrush paint gun and standard 2 component car paint from a local shop.

The helmets have up to 5 layers of paint/varnish depending on how many mistakes I needed to cover on each of them.

The carbon one is transparent varnish only, the Kevlar one is in green RAL 6025 mat and the basalt is in RAL 7016 mat. The paint gun was set so the finish is a bit structural, not glossy.
All 3 of them are sprayed with transparent varnish also on the inside to get the glossy inside look.

At this point, I was satisfied with the result, but we are not done yet.. there is much more work to be done on the inside.

Years ago I made the interior for the original YU helmet I am using now since I got it empty. Now I tried to copy the work I made back than and is well tested over the years.

I designed the "hooks" and got them water cut from 1.5mm aluminum in a local shop. Sent them to the cataphoresis paintjob afterwards and the result looks verry nice. They can be bent by hand afterwards.

I am including .DXF files if you need to cut them feel free to use them.

I helped myself with a piece of plastic sheet while placing the holders and finding out the right locations. I decided to glue them with 5min epoxy. The other option is to use rivets, but this includes drilling and the rivets would be visible on the outside. I did not want that, hopefully the glue will hold over the years.
To make the glue stick better sand both, the alu holders ant the helmet on the part where glue will be applied.

Mix a bit of cotton flocks to the epoxy to make it denser. For the black helmets I also used some black pigment to make it black.
The neck strap holder needs to wait to be glued after the strap is sewed to it.

My version of interior consists of 25 and 15mm nylon straps.
First you should make 6 (per helmet) folded 25mm parts sewed on one side that can let threw 2 25mm straps (visible on photos).
Next, 2 (per helmet) 25mm straps long enough to go all around the interior + some extra length with tightening plate on one side.
And finally the neck straps out of 15mm nylon with sewed glue hooks and clips.

Final pack of straps per helmet can be seen on the photo. Additionally, 3 pieces of 25mm strap should be placed between the holders in the helmet. Those ones do not need sewing, only the edges should be heated up to prevent them from tearing apart.

The straps placement can best be seen from the photos. The 2 straps that go all around should be tightened accordingly to the head's size.

Let's see what's the weight of them.

The original metal one that I am using now weights 1200g (2.65 lbs)

The carbon #1 weights 487g (1.07 lbs)

The Kevlar/aramid #2 weights 545g (1.2 lbs)

The basalt #3 weights 526g (1.16 lbs)

All are close in weight, but way lighter from the original metal one.

Thanks for reading all this. I am more than satisfied with the results. Feel free to comment and ask anything I might have missed out and of course share your helmets If you make them.

Till next time.
Vid