Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Tue Aug 16 2011, 07:14PM

If you are having to ask these questions, you will be better off using glass fibre.

You'll probably want 'S' type woven glass (woven rovings)

You need to know exactly what you are doing in order to take advantage of the properties of carbon.

I assume you'll be using a wet lay-up, with epoxy, rather than pre-preg, but you will probably still benefit from vacuum bagging if you have access to a pump.

What is this for?

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Aug 16 2011, 09:02PM

I was afraid someone was going to say that.


like this pic:





elaborate please...


Yes as I make mostly flat sheet or compression molding for fiber glass.


Go here -> , youll see.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Tue Aug 16 2011, 09:08PM


I'll elaborate later, for now I'd suggest using glass, with a view to maybe 'moving to carbon' once you've got everything else (electronics, etc) sorted out.

(EDIT: Carbon won't neccesarily make it any lighter, but, if done properly, may make it stronger)

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Aug 16 2011, 09:15PM

Ok that sounds good , pic posted above.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Tue Aug 16 2011, 09:29PM


You're on the right lines there, maybe a finer weave/lighter cloth....but get the method 'sorted' using glass before moving to carbon. (Just my 2 cent's worth)

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Aug 16 2011, 09:39PM

Can you give me an american source to buy this kind of stuff, i mostly buy Tap plastics and automotive FG stuff.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Tue Aug 16 2011, 10:10PM


I'll look into it tomorrow (I've had a drink or three now), but West Resins might be a good starting point for a google search (I know they do resins, not re-inforcements, but it still might be a good starting point).

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Aug 16 2011, 10:43PM


TY.

Re: Differences between good fiberglass, and good Carbon fiber.
2Spoons, Tue Aug 16 2011, 11:14PM

I bought some carbon/kevlar tube for my kayak paddle from here
They've got all sorts : glass, carbon , kevlar, basalt, and mixed materials. In cloth, tube, etc.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Aug 16 2011, 11:44PM

Ty, but what does pics per inch mean ? it says 17x17, is that the width of each weave?

In the above pic, each "strand bundle" of fibers is 0.040 inches wide, with the plain weave.

1/17 = 0.059" so this is a more coarse weave than what i already have.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Tue Aug 16 2011, 11:56PM

I imagine you will probably want a carbon/kevlar mix eventually, but just stick with 'S' glass for now. (Fairly fine weave/low weight)

Re: Differences between good fiberglass, and good Carbon fiber.
2Spoons, Wed Aug 17 2011, 01:28AM


A nice explanation from the same site

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Wed Aug 17 2011, 11:17AM

Some interesting reading here, including comparisons between E glass, S glass, carbon and kevlar:

Re: Differences between good fiberglass, and good Carbon fiber.
Proud Mary, Wed Aug 17 2011, 11:37AM

Not so fast, Boy Wonder!

Fink BF, McCullough RL, Gillespie JW, Induction Heating of Carbon-Fiber Composites: Thermal Generation Model, Army Research Laboratory, ARL-TR-2261, September 2000.



EM interactions involving the carbon in carbon-fibre composites feature in a number of journal papers.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Thu Aug 25 2011, 06:48AM

This is facinating!

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Sun Dec 18 2011, 06:16AM

Ive broken a whole lot of Carbon fiber and fiber glass im now considering laying up my own CF, im reseaching this all-over again, any help is appreciated.

I see a lot on Ebay.

EDIT: im thinking of a Carbon Fiber/Kevlar mixed 3K fabric, 2X2 twill, and a -60, 0, +60 layer, 5.7 Oz., on balsa, with an epoxy wet lay-up.


Stiffness and strength are most desirable.

Im still trying to figure out the differences in the "K" numbers, i see 1,3,6,9,12,24K's but dont know what they mean in terms of strength/stiffness. iknow thats thethread count for bundles and that more strands means a thicker cloth.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Mon Mar 19 2012, 04:18AM

ok ive got 6 yards of S type fiberglass, and 3 yards of 644Ksi CF with a good hard epoxy coming in the mail.

ive researched a lot more, practiced laying up FG, im getting prettyt good at flat stuff. (and screwed up a whole lot too.)

ive got 2 savox digital servos, 2 castle 50 ice ESCs, and an AR6115e reciever, 2 eflite power 10's and a STM32VL and another STM32F4, 3 lipo's at 11.1volts, 2200mah.

im on my way to North Dakota IARC 2012!

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Mar 20 2012, 08:56PM

ok so the thickness of the 3 layer crap fiberglass is 0.029" and the balsa frame whieghs in at 61 grams, with the top layer of FG it now whieghs 230 grams, with 230 sq inches and 169 grams of FG that means 0.735 gams per sqare inch.

Re: Differences between good fiberglass, and good Carbon fiber.
Dr. Slack, Wed Mar 21 2012, 08:00AM

If you're going for specific strength, that is strength to weight ratio, then one of the most important things is to use the right amount of resin. Too little, and the strength suffers, you risk delamination under load. Too much (and this is dead easy for the amateur who will tend to use "a bit more for luck", what people over 45 in the UK call the 'Enry Cooper Brut 33 effect) and the weight suffers.

Pre-pregs are more expensive than wet-lay, but tend to have just the right amount of resin on them (which is why people use them). Do consider vac-bagging.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Wed Mar 21 2012, 05:50PM

Vacuum bagging is essential for max. strength to weight ratio.

I believe I mentioned this earlier in this thread.

Lay-up is also pretty critical too.

S type glass will be much easier to achieve good results for a beginner than carbon.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Wed Mar 21 2012, 08:01PM

i think ive got the E and S glass lay-up pretty much figured out, ill try CF next. i like the vacuum bag examples ive seen on you tube, but that all looks expensive. and what is that nylon dispersing fabric they use called?

since CF is so much more valuable that FG, id like to use CF where needed, then FG to unify the whole stucture. so i wonder how i could make I or Square beams, or may be i should just buy the CF tubes/rails, and lay-up my own FG?

RC foam.com (for CF)

ive also just got my 0.375 gallon epoxy from UPS, that will last me quite awhile.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Wed Mar 21 2012, 08:45PM


Ideally you want to go for cylindrical, spiral wound unidirectional, or something similar. Maybe google carbon/composite mast lay-up?

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Wed Mar 21 2012, 09:10PM

i need to strengthen largly flat structures, so round tubes maybe difficult attach? right?

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Wed Mar 21 2012, 10:25PM

Foam sandwich could be the solution.

tubes do give the best stiffness to weight ratio, though.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Wed Mar 21 2012, 10:53PM

Ive been using about 1.4mm thick balsa for this reason, then FG'ed both sides.



round, sqaure or I beam?



EDIT: i just finished the FG layup for the main tail fins, i just learned another lesson: fold the unfinished edge under itself, like a hem, so the fray isnt visible. i dont like the plain weave. Ive got the CF all in 2x2 twill. Plus i got this one just right, the amount of epoxy isnt to much or too little, my rolling technique is good! ive got the heater on and IR temp sensor, as its expected to get cold tonight.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Sun Mar 25 2012, 08:57PM

ok i see how to do large layups now, ive made them too dry, too wet and just right. so ill be making more tonight, my FG and CF fabric arrived friday so ill be using s-glass from my new supplier for the first time tonight.



that water pipe keeps the balsa fins from curving while wet with epoxy.




Painted black, electrics and mechanics present. (The small circuit board is for basic flight control and intelligence, the large STM32-F4 board is for autonmous intelligence and sensor aquisition.)

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Mon Mar 26 2012, 11:35PM

Looking good, Patrick. Hope you found some of the advice useful.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Tue Mar 27 2012, 01:54AM

yep i did!

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Sun Apr 01 2012, 04:37AM



I found this source which explains some of the trade offs of the differetn fibers.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Sun Apr 01 2012, 08:25AM


Yep. Pretty much says 'S' type glass and epoxy is a good 'all round' material, especially for early development of a project, due to ease of use and cost. Carbon and kevlar 'may' have some advantages in specific applications, but there are trade offs, eg brittle failure of carbon. (glass is tougher and will survive more 'crash landings', but some weight savings 'may' be possible using carbon).

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Sun Apr 01 2012, 11:49PM

im trying to figure out the advantages of each, and if a hybridization would be useful. like kevlar/carbon to resist cracking.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Mon Apr 02 2012, 01:48AM

If you need to save weight, carbon will help stiffness, but at the expense of not being able to survive a crash landing.

Kevlar is usually added where impact/abrasion resistance is required. I'm not sure it will be appropriate in this instance.

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Mon Apr 02 2012, 03:24AM

Im building version 2 now, it should whiegh in at around 250 grams. As opposed to version 1's 631 grams. Ill use Bass wood, Balsa, and CF. Then ill do some destructive testing and well see if i need kevlar.

Doesnt the kevlar/CF hybrid resist the CF's tendency to crack and fold up?

Re: Differences between good fiberglass, and good Carbon fiber.
Carbon_Rod, Mon Apr 02 2012, 04:39AM

In general, thin-wall carbon tubes are cast in a vacuum bag around a metal mandrel to remove excess polymer. They usually remove the metal form because it would add negligible structural strength to the item.
Likewise, balsa wood offers little over foam for structural support.

Kevlar has quite a few issues I won't discuss here, but it can make the material more flexible in general...

Based on the scale:
* Polystyrene foam board
* Carbon tissue-paper or adhesive vinyl model aircraft skin
* Enforce with long-strand stock from an RC shop selling carbon-fiber wing struts
* The EDF thrust vectoring nozzles are mostly plastic lined foam

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Thu Apr 05 2012, 01:27AM

Ive just setup the first FG S2 type 9 inch duct. the S fiberglass and the MAX1618 epoxy are far superior
to the E glass and general purpose finish epoxy i was told to use.

the S glass is real nice, doesnt fray, almost negligiable in stiffness before wet-out. the new Max epoxy is so easy to wet. Just laying the glass cloth out and it draws the eoxy in better at 75 F than the old epoxy at 95 F. i expect this one to have some minor defects as its the first round ive made out of FG, but i plan to make 10 to 15 of the ducts as theyre the first parts to get broken off while flying into window and door openings.

The thin epoxy also drips out and prevents excessive build, for much lighter parts than my previous method.

Re: Differences between good fiberglass, and good Carbon fiber.
Ash Small, Fri Apr 06 2012, 11:54AM


The kevlar will 'hold things together' when the carbon fails.


I did suggest using 'S' glass right at the beginning of this thread. Who told you to use 'E' glass?

Re: Differences between good fiberglass, and good Carbon fiber.
Patrick, Fri Apr 06 2012, 05:12PM

no one, the cheap E-glass was all i could get, and i needed the first prototype and practice in the first 4 weeks of class.