Structural Veil, Epoxy

I have some ideas kicking around about ultralight MPR, but I'm out of my depth-of-experience on composite/laminate materials.

• Are any/all of these -UN-suitable for structural use such as tube rolling, tip-to-tip papering?
  • Carbon Fiber Tissue
  • Fiberglass Tissue
  • Aramid ( Kevlar ) Tissue
  • Aero-Veil
• If -NONE- of these are suitable, what is the lightest woven fabric we know about?

• Regardless, which epoxies are likely to yield the lightest final weight?

I'm perfectly capable of ordering a couple dozen samples of tissue, fabric, and/or epoxy ; but I'd rather not :smile:

Cheers!
-dh.

What size rocket are you considering?
I'm shy on Epoxy, but I could send you a few small samples of some various FG cloth weights to mess around with.

That's how I got started glassing. JeromeK99 noticed me papering everything and occasionally using basswood for fins, and told me how lightweight glassing would make my builds even stronger and not nearly as heavy. The rest as they say, is history.
A couple other folks saw me glassing and sent me some different weight fabric to try, and I loved that too!

The amount of weight it adds is not as much as you would think, and it certainly is lighter than basswood and filling spirals and having to use lots of heavy coats of primer to cover imperfections.

PM me if you are interested.

PM sent ; I'll publish any results I get here, if I don't end up permanently affixing my fingers to some other body part

I'll visit the post office on Friday!
Hope you love it as much as I do!

The lightest would be fiberglass in the .5 to .75 oz range along with epoxy. The number of wraps would depend on how strong you need the airframe to be.

Pat_B said:

The lightest would be fiberglass in the .5 to .75 oz range along with epoxy. The number of wraps would depend on how strong you need the airframe to be.

Click to expand...

So none of these .2 - .4 oz unwovens might be marginal for wrapping or fin-tipping , say, a CTI 144-G65-WH/LB-8A ?

That weight range would be way too light for that purpose. You get a lot more structural strength using a woven fabric.

Some people use a heaver fabric for structural strength, then overlay that with the lightweight stuff for a better finish.

Pat_B said:

That weight range would be way too light for that purpose. You get a lot more structural strength using a woven fabric.

Some people use a heaver fabric for structural strength, then overlay that with the lightweight stuff for a better finish.

Click to expand...

I am aware of the -intended- use for these materials.

It would be very presumptuous of me to ask for a reference to the lightest woven fabric one knows, nevertheless....

Lighter fabrics are actually more of a pain to deal with than heavier fabrics, they seem to want to "float" on the epoxy and have a tendency to move around as you work them. However they do give good results once you learn how to deal with them.

Hi dh

you can work with the tissues but the kevlars and Cf's are brittle, require thickness to maintain integrity. You can get some fiberglass plain weaves at less than 9gsm but expensive and typically done on old Toyota looms, look to Japan for specialty fiberglass, electronic supply companies.

If you decide to go this route use a wetting aid as it will cut down on the slippery-ness referred to by some.

Epoxy is not necessarily the lightest or strongest choice....west systems is typically brittle and when combined with a brittle variant (high mod) kevlar or carbon fiber is a bad combo. If you want the lightest resin a trick from racing is to add 50% (mix to your requirements really) glass bubbles or other glass shapes to a low viscosity low solids resin....creates a brittle matrix but its light weight. just combine with a mid mod fabric. Me I would go with a stronger fabric and lighten up the resin system.


You also have several vinyl-esters on the market that out perform room cure epoxies.

rharshberger said:

Lighter fabrics are actually more of a pain to deal with than heavier fabrics, they seem to want to "float" on the epoxy and have a tendency to move around as you work them. However they do give good results once you learn how to deal with them.

Click to expand...

This is a good point!
I have found that doing multiple wraps of really light stuff is trickier than doing single wraps of heavier stuff.
The 1.25oz. and 2oz. stuff is easy to work with. I have some 2.3oz stuff you'll like that goes on nice and stays where you put it.

Aero-Veil works will to improve the finish. I cannot speak of strength. I have used it on balsa fins on a mid powered rocket. The fins held up to flights and landings, but burned up in a motor CATO.

I have also worked with FG, Kevlar, and Carbon Fiber veil. All four tends to float on epoxy. All four improve your ability to finish the rocket with less filling.

Sorry, I have never tried to break them.

Any of the veil fabrics are purely to prevent fabric pattern print-through at the surface as they don't have a woven pattern. Structurally, they are darned near useless.

For a fiber to take tension or compression it needs to be aligned with the applied force. A misalignment of 20 degrees costs on the order of 50% of the strength. In a veil fabric, the fiber density is low and the alignment is random. Only short sections of very few fibers will try to take the load. So, they simply break. As I said, useless, structurally.

Fabric wetout isn't really a problem in general if one is using the right epoxy types for the job. That is, laminating resins. Preferrably aerospace ones, not West Systems (which is rather good for its intended purpose which is fiberglassing onto wooden boats and not running off too badly on vertical surfaces, but is very poor for any aerospace application. Too thick, too heavy, way too low a Tg). Absolutely not thinned epoxy glue.

Highest strength light thin fabrics currently available are spread-tow carbon. Try R&G in Germany for good selection and price.

Gerald

G_T said:

... Structurally, they are darned near useless. ... A misalignment of 20 degrees costs on the order of 50% of the strength. ...

Click to expand...

This is super interesting! While doing my Necessary Research Homework , I stumbled across An Article indicating X layers at Y degrees offset given Z materials ; I cannot now recall The Article.

Might you, perchance, have a reference to Show Us The Way?

Somewhere or other in my pile of research papers I have a pdf book on structural joints/repairs for aviation. I believe I have a few others which might also be applicable. Work for a while has been roughly 9am to near midnight for a while, most days. So I'll need to get some spare time to dig around and find the relevant stuff. But google searching will find it if you dig in. It might be better to do that than to wait for me to have an hour free to dig through my papers and books.

Gerald

Google search for:

Adhesive Bonded Joints for Composites
Adhesive Bonding of Aircraft Primary Structures
Adhesively Bonded Joints for Fibrous Composite Structures
Composite_Repair.pdf
Composite Structures, volume 25, 1993
DIAB Guide to Core and Sandwitch
Effects of Flaws and Porosity on Strength of Adhesive-Bonded Joints
ESA Adhesive Bonding Handbook
(R&G) Faserverbundwerkstoffe Composite Technology - Handbuch Edition 06 09 (or any later ones which may be better)
Further Developments in Design and Analysos of Adhesive-Bonded Structural Joints
Introduction to Composite Materials
MGS L285 Properties
td_en_vergleichsdaten_kohlenstofffasern_engl.pdf
Tech Tip 24 - Bonding to Al
The Curse of Nylon Peel Ply

I can't post them of course as that would be a copyright violation. If you search for these you might find something interesting. I haven't sorted them out for you; I really don't have the time. Sorry.

Likely there are better papers you can find. I also know I have a bunch which I missed on quickly checking through my computer - stuff on specific techniques such as vacuum diffusion bonding. Info on techinques such as bladder molding are readily available on rcgroups, where you might even find a thread or two of mine.

Example reject carbon tube, weight approx. 12.4g going by memory, holding 7.5 pounds at the end, without failure:



The tube held the weight out to the end of the boom, but my wrist did not. I tilted, and they fell off. I wasn't strong enough. Hard to work a camera with one hand and hold the tube with the other. Taken with a GoPro, so a badly distorted picture... Sorry about that!

Gerald

G_T said:

Adhesive Bonded Joints for Composites
Adhesive Bonding of Aircraft Primary Structures
Adhesively Bonded Joints for Fibrous Composite Structures
Composite_Repair.pdf
Composite Structures, volume 25, 1993
DIAB Guide to Core and Sandwitch
Effects of Flaws and Porosity on Strength of Adhesive-Bonded Joints
ESA Adhesive Bonding Handbook
(R&G) Faserverbundwerkstoffe Composite Technology - Handbuch Edition 06 09 (or any later ones which may be better)
Further Developments in Design and Analysos of Adhesive-Bonded Structural Joints
Introduction to Composite Materials
MGS L285 Properties
td_en_vergleichsdaten_kohlenstofffasern_engl.pdf
Tech Tip 24 - Bonding to Al
The Curse of Nylon Peel Ply

Click to expand...

This is an awesome reference ; thanks so much for the direction!

TopRamen said:

I could send you a few small samples of some various FG cloth weights to mess around with.

Click to expand...

Received these today ; thanks! My wife will thank you as well, because working with this will require me to clean off one of the good workbenches in the garage, which inevitably results in me throwing out a bunch of someday (never) projects.

dhbarr said:

Received these today ; thanks! My wife will thank you as well, because working with this will require me to clean off one of the good workbenches in the garage, which inevitably results in me throwing out a bunch of someday (never) projects.

Click to expand...

Awesome!