FG/CF: How to estimate the weight and thickness?

I have never done composites laminating before and have a question. I am thinking of laminating phenolic tubing for a L2 or L3 capable rocket. While working on the design in OR, I don't know what to put for the weight/thickness. Assuming a 6oz cloth, how much weight (resin and cloth) will this add to my rocket? Obviously, the cloth weighs 6oz per square yard, but what about the resin? What is the thickness per layer going to be?

Also, how many FG layers do you think a 6" phenolic will need to be to handle all Ms and most Ns? CF layers?

It varies per user. The weight of the cloth plus the weight of the epoxy.
If you are using 6 oz cloth I'd go with 3 layers.
With carbon fiber is stronger but, also more delicate.
You need to apply a sanding or protective veil.

JD

I saw on the site FiberGlast, that they say the amount of resin is about the same as the weight of the cloth. So a square yard of 6 Oz would use about 6Oz of resin as well. Does anyone have experience that verifies or de-bunks this claim?

If you vacuum bag you will ideally get 50/50 ratio.
By hand lucky if you get 60/40.

JD

CZ Brat said:

I saw on the site FiberGlast, that they say the amount of resin is about the same as the weight of the cloth. So a square yard of 6 Oz would use about 6Oz of resin as well. Does anyone have experience that verifies or de-bunks this claim?

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The only comparison I can offer is a recent on going project.
I laminated a 16.25" long piece of 5.38" Loc tubing.
I weighed it before I glassed it ( usually don't)
It weighed around 298 grams before the lamination.
After it weighed 485 grams.

That was: 2 layers of 6 oz S-Glass and 1 layer of 3 oz E-Glass.
Hand laid, no vacuum, 2 wraps continuous ( it was one piece of fiberglass).
The 3 oz was a separate piece.

It didn't add allot of thickness, maybe another 1/32" or so.


JD

JDcluster said:

If you vacuum bag you will ideally get 50/50 ratio.
By hand lucky if you get 60/40.

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Yep.

Typical thicknesses are almost always provided by the supplier. See for example US Composites FG cloth: https://www.uscomposites.com/cloth.html.

dixontj93060 said:

Typical thicknesses are almost always provided by the supplier. See for example US Composites FG cloth: https://www.uscomposites.com/cloth.html.

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So does that thickness include the resin? Does resin add much thickness?

JDcluster said:

If you vacuum bag you will ideally get 50/50 ratio.
By hand lucky if you get 60/40.

JD

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So with vacuum bagging, if the cloth weighs 1 oz, I will add 1 oz of weight with the resin, and hand layup will add 1.5 oz of resin?

That sounds about right, again I don't weigh most of my hand layups.
There will be a thin layer of resin in between each layer of cloth wrapped around the parts.

No, the thickness given is the how thick the cloth is.
The amount of resin depends on temperature, and viscosity of the epoxy system in use.


JD

CZ Brat said:

So with vacuum bagging, if the cloth weighs 1 oz, I will add 1 oz of weight with the resin, and hand layup will add 1.5 oz of resin?

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Another question. If doing more than one wrap, do you do one. At a time or 2 wraps at once? Is it different for vacuum versus hand?

CZ Brat said:

Another question. If doing more than one wrap, do you do one. At a time or 2 wraps at once? Is it different for vacuum versus hand?

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For two layers, do one continuous wrap that will go around the tube 2 times. I usually cut a 1/4" beyond the seam to insure I have overlap.

BTW, I have gotten 50/50 resin/cloth ratio with hand layups for airframes, but it is only by using a roller. You just keep rolling and rolling until the cloth is fully wetted out.

https://www.amazon.com/dp/B007VS4FIC/?tag=skimlinks_replacement-20

Greg

I go with at least a 2" overlap.
I use a broomstick or pole to hang the tube off of.


Measure out you cloth first, once you start mixing epoxy everything will have move quicker.
You need to be able to coat everything before the potlife window expires.


JD

[video=youtube;bjZNyXsd8gw]https://www.youtube.com/watch?v=bjZNyXsd8gw[/video]

Tony

I saw on line the suggestion of filling the tube with couplers when vacuum bagging. If I vacuum bagged cloth onto 4" or 6" phenolic, do I really have to put couplers into the tube to reinforce it? It seems to me, that at aprox. 14 PSI, evenly applied around the entire circumference as you have in bagging, it shouldn't deform the tube in any way. Any experience with this? What about standard LOC tubing?

I would suggest: you start with hand layups first.
Vacuum bagging is tricky even for me with a couple of years of experience.
You need something internal to better support your work.
End caps are also required to prevent the bag from being sucked into the tube.

I did one wrap of Carbon Fiber / Red Kevlar on a PML phenolic tube back in 2004.
I used a 98 mm casing to hold the shape of the tube.
The results weren't the best ( had some wrinkles) but the tube was tight on the inside after... and had to really sand the coupler in order for it to fit.
It squeezed it that much.

14 PSI doesn't sound like allot until you put it up against 1-2 PSI.

Here's a good example:
[video=youtube;Uy-SN5j1ogk]https://www.youtube.com/watch?v=Uy-SN5j1ogk[/video]

JD

CZ Brat said:

I saw on line the suggestion of filling the tube with couplers when vacuum bagging. If I vacuum bagged cloth onto 4" or 6" phenolic, do I really have to put couplers into the tube to reinforce it? It seems to me, that at aprox. 14 PSI, evenly applied around the entire circumference as you have in bagging, it shouldn't deform the tube in any way. Any experience with this? What about standard LOC tubing?

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