Composites 101: Carbon Fiber, Fiberglass, etc.

[ebrabaek]

Originally Posted by tmotten

Fair enough. I've decided to go with a female mould for this fairing. Will need to cut some of the inside panel for access though, but that's there for aesthetics only anyway. This will make it easier to layup wet and produce a heaps better finish with no worries about degassing.

What's your opinion on more layers with lighter fabrics vs less with heavier fabrics?

The thickness of the fabric... Is usually determined by the kinks and crazy angles it has to conform to..... Like thinner fabric conforms easier than thick..... But takes longer labor..... Either is fine.. Like what ever you can get the cheapest.... 90% of my projects are done with 6 ounce fabrics.... ( either carbon fiber or kevlar) It`s a great all around thickness to work with..... I use twill. 2x2.

Erling

[Orangecicle]

Originally Posted by tmotten

Fair enough. I've decided to go with a female mould for this fairing. Will need to cut some of the inside panel for access though, but that's there for aesthetics only anyway. This will make it easier to layup wet and produce a heaps better finish with no worries about degassing.

What's your opinion on more layers with lighter fabrics vs less with heavier fabrics?

Twill fabric is fairly easy to "bend" around odd corners, like you see on your fairing. Some fabrics, such as the checkerboard pattern, can be really hard to bend around odd shapes.

[Orangecicle]

I'm looking for a decent vacuum regulator. I've found decently vacuum pumps at reasonable prices, and I'm going to build my own vacuum tanks: http://www.joewoodworker.com/veneering/whybuild.htm

(borrowed photo)

But now I'm looking for an electro-mechanical valve that will cut off the pump when the vacuum hits about 25" Hg. Any ideas? I started trying to find a good regulator, but the only regulators I'm finding are really expensive at over $200, and that doesn't include a cutoff valve to shut the pump down when the pressure gets high enough:

http://www.smcpneumatics.com/irv-series.html



Maybe it's cheaper in the end to just buy a more expensive regulated pump? I don't know.

[trackhead]

Here's my finished project of a custom fiberglass, pop up camper on my Samurai.

[HickOnACrick]

Originally Posted by trackhead

Here's my finished project of a custom fiberglass, pop up camper on my Samurai.

Trackhead,

This is really nice work. I can't wait to see the inside. Did you use foam as your mold? If so, where did you find pieces large enough?

[HickOnACrick]

Originally Posted by Orangecicle

I'm looking for a decent vacuum regulator. I've found decently vacuum pumps at reasonable prices, and I'm going to build my own vacuum tanks: http://www.joewoodworker.com/veneering/whybuild.htm

(borrowed photo)

But now I'm looking for an electro-mechanical valve that will cut off the pump when the vacuum hits about 25" Hg. Any ideas? I started trying to find a good regulator, but the only regulators I'm finding are really expensive at over $200, and that doesn't include a cutoff valve to shut the pump down when the pressure gets high enough:

http://www.smcpneumatics.com/irv-series.html



Maybe it's cheaper in the end to just buy a more expensive regulated pump? I don't know.

I bought a Harbor Freight pump over a year ago. I have used it for multiple projects and it is still going strong. It was on sale at the time for around $130, and I believe building one yourself will cost nearly as much.

[trackhead]

Originally Posted by HickOnACrick

Trackhead,

This is really nice work. I can't wait to see the inside. Did you use foam as your mold? If so, where did you find pieces large enough?

Home Depot polystyrene, the pink stuff.

[trackhead]

Hey Hick, what do you think of those pumps that work off of an air compressor? I have a decent compressor in my garage already.

[flemsmith]

Post # 36 I printed it and was waiting til I actually got the bike running again before I messed with the sidebags. Plastic Enduro's that someone jigsawed an inside corner out of. I've never done any fiberglass work, didn't even know how to buy it. So I read the detailed instructions and gave it a try....unfortunately I was using Bondo gel resin, and it's boucoup thick. It did manage to plug the hole from the inside, but on the outside (which luckily won't show when it's mounted) I still ended up with a thick mess that I couldn't really smooth when 'wet', so I sanded it and went to Home Depot to buy the 3M version, which went on much more like your description.

http://flemsmith.smugmug.com/Other/M.../IMG3678-M.jpg

Here's a pix of the rough dried fiberglass before any sanding or painting. (assuming I did the picture link properly). The green color is from the bondo resin, I can't see using that again.

The main point is that I really do appreciate the great advice available on this site, For almost any topic! Thanks!

roy

[redprimo]

Here are a couple of tips:

Use large diameter shallow containers vs small diameter deep containers to extend the pot life of polyester resin. epoxy is less sensitive to this.

You will get better results with spraying pva by not thining it and spraying with a non hvlp gun. The best pva gun I had was an old binks model 7.

Tape down some heavy plastic over a table and lay your cloth flat to wet it out then pick it up and place it in the mold. On choped and thicker cloth pour/paint some resin on the plastic before placing the cloth on the table. Large pieces of pre wetted cloth can be transered to the mold by rolling or folding up the cloth to avoid streatching and distortion. Doing this will speed things up and can help reduce resin pooling in the bottom of your mold.

Tap Plastics in California is a great resource for all things composite. their house brand of epoxy is very similar to system 3. In addition to the 3 hardeners having different working times the most important difference is they produce 3 different levels of stiffness.

[HickOnACrick]

Originally Posted by redprimo

Here are a couple of tips:

Use large diameter shallow containers vs small diameter deep containers to extend the pot life of polyester resin.

Do you have this backwards? I am under the impression that the greater the surface area exposed to air, the shorter the pot life??

[bxr140]

He might have been talking thermal runaway? Dunno.

[redprimo]

Originally Posted by HickOnACrick

Do you have this backwards? I am under the impression that the greater the surface area exposed to air, the shorter the pot life??

Not for polyester resin. Polyester resin is an exothermic reaction and heat is also an accelerant to the reaction. if you contain the heat it will go off faster. That is why resin in any bucket always goes off before the lay up. Likewise if you use a large diameter bucket and increase the surface area and minimize the thermal mass you will extend the pot life. My tip about pre weting the cloth is also a way to extend the pot life. The pre wetted cloth if left flat will not go off as fast as the resin in the bucket.

I used to have my own pattern and mold business and before I had any employees large layups would get a bit crazy. I would mix resin and paint some on the mold then wet out a piece of cloth and fold it up and transfer it to the mold and un-fold it but not roll it out, then pre wet another layer and leave it on the table while I rolled out the first piece of cloth.

I have never used a paint roller to apply resin, it is too slow. I aways pre-weted the cloth by pouring the resin on and then using a bondo spreader to move it around. When I mention rolling out the cloth I am refering to using a ribed metal roller to get rid of any air bubbles.

All that I have written also applies to epoxy but the effect of using a shallow bucket on 40 minute epoxy is less than on polyester resin.

You may be refering to high humidity reacting with epoxy resin and making it kick faster. I live in California and have no experiance with this so some one who does will have to chime in.

[HickOnACrick]

Originally Posted by redprimo

Not for polyester resin. Polyester resin is an exothermic reaction and heat is also an accelerant to the reaction. if you contain the heat it will go off faster. That is why resin in any bucket always goes off before the lay up. Likewise if you use a large diameter bucket and increase the surface area and minimize the thermal mass you will extend the pot life. My tip about pre weting the cloth is also a way to extend the pot life. The pre wetted cloth if left flat will not go off as fast as the resin in the bucket.

I used to have my own pattern and mold business and before I had any employees large layups would get a bit crazy. I would mix resin and paint some on the mold then wet out a piece of cloth and fold it up and transfer it to the mold and un-fold it but not roll it out, then pre wet another layer and leave it on the table while I rolled out the first piece of cloth.

I have never used a paint roller to apply resin, it is too slow. I aways pre-weted the cloth by pouring the resin on and then using a bondo spreader to move it around. When I mention rolling out the cloth I am refering to using a ribed metal roller to get rid of any air bubbles.

All that I have written also applies to epoxy but the effect of using a shallow bucket on 40 minute epoxy is less than on polyester resin.

You may be refering to high humidity reacting with epoxy resin and making it kick faster. I live in California and have no experiance with this so some one who does will have to chime in.

Cool. Thanks for clearing that up. Do you think one could pre-wet some layers, then toss them in a fridge for 30 minutes or so until he got all the layers ready, then lay up he piece?

[ebrabaek]

There are a lot of good user input in this thread. A subject that most books....dvd's or course's don't cover..... "The spills and thrills" But as with many people trying their own phase of work..... they venture out to try new things.....and all are not good.... and so it goes that mis information.... Or things that is not necessary the way things work correctly can be misinterpret, and discourage others that thought this is the way. So with all these different advises......available....I encourage all to test new methods ( wherever they are found) on a test batch of any kind.... Before moving onto the piece you are making.......as you are running a risk of destruction and failure...... Which to the newcomer can be detrimental. Many things work great...but perhaps not for each project... So that goes for every project.... Test your methods on a ....uuuummm test bed before moving on to your project...... That said.... Onward with the layups.....

Erling