Fiberglass thin versus thick for props?

[josiff]

Hey all,

Relatively new to purchasing props, but I have a question.

If you can see light through the fiberglass of your prop when it has white primer on top. Is that bad?

I've been looking around the forums and I got a new prop recently and the prop is really lightweight, but it's really thin compared to the only other fiberglass prop I have that is really thick... like probably 5x more thick than this minimum.

Is there a point to add more fiberglass to it? I couldn't find any threads about thin vs thick fiberglass other than the more layers you add the more heavy it gets. Is there a benefit to impact/shatter resistance if it is thicker?

Below are some photos. First photo is the inside of it with flash. 2nd and 3rd somewhat blurry photos are a ceiling light shining through from above.

 

[lmgill]

The question is, is the thin piece, mostly glass, with a small amount of resin? If so, this is far better than a thick piece.
A common mistake is to think of fiberglass as an additive to polyester resin. This is incorrect. The strength is in the glass, the resin just keeps the glass from moving. If a Fiberglass-reinforce plastic (FRP) is thick, this often is an indicator that the person laying it up, believed more resin, less glass was the correct way. Here are a couple of great images of a 1960's Porsche 904 race car body, with a proper layup of FRP. It has been photographed with a light inside to show how thin and even the glass layup is. Excess resin, just makes the FRP weaker. A good FRP piece can be bent and flexed with no "cracking" sounds. Fiberglass skies for example.

 

[Duncanator]

Imgill is right about thick resin not adding to the strength.

Now, additional layers of glass in alternating directions will add the the strength and rigidity of a casting. The gel-coat doesn't get any harder, but it'll be harder to punch a hole through the wall of your casting.

Flying model airplane bodies are often remarkably thin, but you'll want that to reduce weight. A full sized boat hull is going to want to be thicker because you may hit a submerged log while out on the lake, and you don't want to sink.

So what you might want really depends on how much abuse your part might need to endure. I prefer to keep my parts thin, but reinforce areas that may see heavy use.

 

[josiff]

The question is, is the thin piece, mostly glass, with a small amount of resin? If so, this is far better than a thick piece.
A common mistake is to think of fiberglass as an additive to polyester resin. This is incorrect. The strength is in the glass, the resin just keeps the glass from moving. If a Fiberglass-reinforce plastic (FRP) is thick, this often is an indicator that the person laying it up, believed more resin, less glass was the correct way. Here are a couple of great images of a 1960's Porsche 904 race car body, with a proper layup of FRP. It has been photographed with a light inside to show how thin and even the glass layup is. Excess resin, just makes the FRP weaker. A good FRP piece can be bent and flexed with no "cracking" sounds. Fiberglass skies for example.
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This is super interesting.... Thank you for the photos as well.

I'll need to inspect it. This prop specifically is a Boba Fett/Jango Fett classic jetpack.

The first maker at my original post is 7CS/Darth Voorhees. His pack is so much lighter and thinner than my BobaMaker jetpack V3 (circa 2017) so it really threw me off.

Below is a photo of how thick BobaMaker's fiberglass part of the jetpack is that I have painted up.

Darth Voorhees aka Lou let me know he only really puts 1-2 layers of fiberglass on purpose to be really light.

 

[lmgill]

I can see from this picture, the layup has quite a bit of resin. Maybe no too much, but far more than is needed to make a proper layup.

 

[PropReplicator2]

Just curious as to who made that jetpack?

 

[josiff]

Just curious as to who made that jetpack?

The first 3 photos in my original post are DVH/7CS I just got delivered 2 days ago.

The solo pic that is greyish/blue on the inside is a BobaMaker V3 (2017).

 

[PropReplicator2]

josiff ill speak for Lou when I say he definitely knows what he is doing. His casts are very durable and nearly nobody that I know of has ever had any problems with his parts/castings. His gelcoat is custom made but he definitely adds enough fiberglass to make a durable casting.

P.S. im sorry for not noticing that you wrote who the makers were in a previous post.

 

[Duncanator]

The thinner one looks like it may have been hand laid glass matt, while the thicker one looks to be chopped glass fiber (maybe a chopper gun). Both look like good lay ups from the photos.

 

[Zombie Killer]

Like Duncanator said it depends on the use. A race car body is made just thick enough to survive a race and thier main concern is weight , not driver survivability in a crash. I make my prop stuff relativly thick so it can handle abuse. If you want to carry said prop 10 miles then ya go thinner, if you want to beat someone over the head without it breaking then thicker is better.

 

[kruleworld]

Adam Savage always says cosplay items should be as light as possible. when you've got to carry it for 6 hours in 100° heat, you'll agree.