wieght of fibreglass cloth.

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Gillard

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i've just started to fibreglass a few tubes and am getting some conflicting advice.
what is the best weight of fibreglass cloth to use? at the moment i'm using one layer of 5oz cloth on a 3inch tube, and i'm happy with the results, got rid of most of the epoxy and the tube does not weigh that much.
however, i've been told that 5oz is far too much and i would be using 1 or 2 oz cloth, which seems a bit light to me.

also,

would people recommend cutting the cloth so that there is no overlay on the glass join, or hasving an overlap and doing a bit of sanding?

any advice welcome
 

GregGleason

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I think the 5oz is fine for that size, but I might have gone with 2 wraps.

I cut my cloth to overhang a little, then trim to suit.

Greg
 

kandsrockets

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Your 5oz glass is good. The lighter glass will do nothing with one wrap. The lighter glass is good for a sanding vail. I use 6oz or 8oz (depends on who has a good price at the time) glass on all my builds 2.1" dia and bigger. Some only get one layer and some get 2 or 3 layers depending on what it being built for. I always leave a little over hang and sand it off after it has cured.
 

blackjack2564

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I concur with the above advice. I use 6oz on everything from 38mm up to 150mm just adding more wraps as the size increases

Just a single wrap on several AT kits has saved them from some nasty zippers and as you mentioned really doesn't add much weight.
 

Gillard

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thanks for the input so far, i had doubts that 2oz cloth would be enough, one guy in my club has been advised to use 2oz cloth around cardboard tubes for his level one build, personnally i don't think that is enough, probably okay on a baby H. i'm planning 5 or 6 oz cloth round phenolic tube for my level two.
 

troj

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thanks for the input so far, i had doubts that 2oz cloth would be enough, one guy in my club has been advised to use 2oz cloth around cardboard tubes for his level one build, personnally i don't think that is enough, probably okay on a baby H. i'm planning 5 or 6 oz cloth round phenolic tube for my level two.
It depends on what his goal is.

If he wants a bit of abrasion resistance, then he'll get it. But not much. Little or no structure will be gained from 2 oz cloth.

A couple wraps of 5oz around your phenolic tube will make a world of difference. But, at the same time, it's not necessary.

FWIW, the other guy is going to have a harder time doing his layup -- light weight cloth is harder to work with, as it bunches up more easily.

-Kevin
 

flight4

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This is a great topic. I was thinking of throwing out my own query on what weight cloth to use on a first glassing project.

Another question though. Would you use the same 5-6oz cloth when glassing fins tip to tip for strength? One layer, or more?
 

kandsrockets

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This is a great topic. I was thinking of throwing out my own query on what weight cloth to use on a first glassing project.

Another question though. Would you use the same 5-6oz cloth when glassing fins tip to tip for strength? One layer, or more?
I use the same glass for tip to tip as I do for the body tube. As for layers this depends on how large the fins are and also what the fins are made of. I have rockets that one layer t-t-t was enough and I have others that needed 3 layers.
 

troj

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This is a great topic. I was thinking of throwing out my own query on what weight cloth to use on a first glassing project.

Another question though. Would you use the same 5-6oz cloth when glassing fins tip to tip for strength? One layer, or more?
To be honest, I've only ever done the tip-to-tip twice. Once, because it was a "used" LOC Warlok someone gave me, and the tube near one of the fins was compromised a bit, so it needed extra support.

The other is a 4" dia rocket with a 3" mount that'll fly on an M motor. Someday.

-Kevin
 

Rocketcrab

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I found this on eBay -

"6 OZ - 50" X 5 YARDS

Fiberglass cloth, 50" wide X 5 yards long. This is a plain weave standard boat cloth suitable for building boats, aircraft, R/C models, speaker boxes, and surfboards. "


Is this what I want for glassing 3" and 4" tubes?
 

powderburner

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would people recommend cutting the cloth so that there is no overlay on the glass join, or hasving an overlap and doing a bit of sanding?
Gillard, you need the overlap left in place when you finish with the build phase of your project.
And the following info is not directed at you, it is just a top-level review of basic structural engineering principles (and not even limited to "aerospace" structures), it is more like a warning to those who apply one layer of glass and then sand off the overlap

While I am not a high-power flier, or builder, I can tell you that without a region of overlap along the seam, your completed tube will be little stronger than the underlying material. You will need an overlap that will probably be at least 1/2 inch to 1 inch wide (overlap width depends on the inter-laminer shear strength and the design margin you wish to use). Depending on your building skills, the overlap may need to be wider to end up with a good, usable overlap zone.

If the two sides of fiberglass wrap material are brought together in a butt joint, you will have a weak "spot" (actually, a line) that extends the length of the joint. The only structural strength your tube will have is whatever properties the underlying material has. If you want the fiberglass to do any good (other than adding weight) it has to be a structurally complete layer, which requires either:

--reinforcing material woven in a continuous tube or sleeve shape that can be pulled over the length of the underlying body tube; the sleeve fibers must be continuously woven around the complete circumference with no joint or loose ends (I think woven carbon-fiber reinforcement is available in "sock" form but I don't know about fiberglass---seems like it should be?)

--reinforcing material woven in sheet form, cut to fit the underlying tube, and rolled into place with a sufficient zone of overlap which must be left in place; if you subsequently sand off and remove the overlap, you are effectively right back to a butt joint (at least, structurally speaking)

If you want to smooth the exterior as much as possible and reduce the visible exterior ridge that forms at the overlap, your choices are:

--change to tooling that lets you control the OUTER contour, that is, mold your fiberglass tube on the inside of a smooth tube-tool surface with pressure applied from the interior (balloon? bladder?) to push the fiberglass material against the mold surface; for almost all of us, this approach is way beyond our construction experience

--use conventional fiberglass wrap techniques and apply an outer layer of peel-off surface smoothing material, bleeder cloth to absorb extra epoxy, and an outer seal wrap, then apply vacuum to the whole thing to suck down the surface smoothing layer; this will reduce the amount of "bumpage" but will not eliminate it completely

--use conventional fiberglass wrap techniques and follow with a layer of microballoons (in matching epoxy); sand the microballoons

Again, if you sand off the fiberglass overlap, you have weakened or eliminated the structural overlap. And if you're going to do that, then you might as well skip the fiberglassing entirely.
 
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kandsrockets

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I found this on eBay -

"6 OZ - 50" X 5 YARDS

Fiberglass cloth, 50" wide X 5 yards long. This is a plain weave standard boat cloth suitable for building boats, aircraft, R/C models, speaker boxes, and surfboards. "

Is this what I want for glassing 3" and 4" tubes?
That will work just fine.
 

rocketsmith

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I have to disagree with comments about the thin veiling glass. I have made several airframes out of Estes bt80 tubes with 2 layers of 1.4 oz. satin weave glass and West Systems or Aeropoxy. The difference in tube rigidity is amazing and the weight is lighter than the Aerotech heavy tubing alone. These airframes have handled my 38mm reloads up to I366R. So, FWIW, I like the lightweight tubing with veiling glass for high performance smaller stuff. Anything in the J range and I would definitely use the heavier Loc or Vaughn Bros. tubing with a layer of 5oz and a layer of veiling glass.
 

WDG

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The cool thing about glassing over phenolic is that you now have a laminate. Composites (unless really done poorly) are inherently much stronger than any of the indiviual components alone. For extreme light weight and rigidity I have heard of using CF tube wrapped in foam and then another wrap or 2 of CF. When you get into large, high performance rockets it seems that some folks get way too caught up in the whole weight thing. There is often a sweet spot for altitude / speed for any rocket. Generally moving up or down from that sweet spot by 5% doesn't change your sim'd results much.

For easy glassing of 4 and 6" tubes I have used glass and kevlar socks. With a good laminating epoxy without vacuum bagging it is possible to get a very nice lay up without tons of extra epoxy. I sorta like using the glass sock as it is an easy way to really integrate separate components. For example, I made a 2 stage Talon 4 (not the kit style from GLR but stretching the aft end). (BTW, that is it on my avatar - the Tall One.) I put a boat tail on the end of the sustainer and the booster. I used a fiberglass nose cone, but my budget did not allow for 2 more glass nose cones for the boat tails. I used the precut plastic nosecone /boat tail for one of them and cut down another plastic nose cone for the other. After sanding and epoxying the heck out of the boat tails, I still had a bit of transition to blend in. Since I expected the booster to see supersonic speeds (on its first flight it hit about mach 1.2) I wanted to reduce the chance of failure due to the plastic to phenolic joint. I used glass sock and started at the end of the boat tail and glassed right over everything (including the slots in my body tubes). I sorta pleated the sock on the boat tails and once the epoxy was set, I cut off the pleats. I used a razor saw to cut open the covered fin slots. I actually didn't want to spend an enormous amount of time priming and filling to get a good finish on this (and was not too concerned by a little weight) so I ended up power sanding the thing and adding another layer of laminating resin. I think I did that twice and ended up using no filler except for smoothing things out on the fin to fin glass (CF/kevlar). I am currently making a 6" conical nose cone using kevlar sock then glass sock over styrofoam (that I will dissolve out later). I suspect I will do 2 layers of glass sock over the kevlar. The sock may not be the strongest stuff out there, but it sure makes me feel like a craftsman.
 
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