Newbie questions

General Composites Discussions Composites Talk
#1

First off, forgive me if these questions are answered in some blatantly obvious location I’ve been doing alot of research but so far keeping up with 3 boards worth of information is difficult.

I’ve been wanted to learn how to lay glass and CF/Kevlar for a while now so I’ve decided to take the plunge over spring break. My first project will just be a flat piece of CF to get the feel for it after that I was planning on doing an Overlay for my TI-86 cover. Pics of it can be found here:
http://wongablog.co.uk/wb-images/ti86.jpg
and here:
http://education.ti.com/images/products/accessory/translucent/colors/bluecalc.jpg

The case has a soft 90 degree curve around three edges with very rounded corners. The plan is sand the area’s with the rubber “feet” down after removing the rubber pieces (they fall off all the time). After that use some sort of filler to fill in the logo area then sand to a level finish.

This is where a question arises, there is lots of info on laying CF but I haven’t found a clear explanation on how you would handle those rounded corners with the cloth while maintaining continuity, also when you come to the edge of whatever you are laying over do you just resin it then cut and finish it down in the end or is there a way to wrap it? Basically how do you make the edges look nice and clean without hiding them.

Finally, just want to make sure my shopping list is accurate:

Standard protective gear(glasses, gloves, mask)
Acetone
Brushes for resin(1/2" or 1")
Roller (not sure what size, probably fairly small)
Resin(or glass)
CF (or Kevlar, or Glass Fabric, or whatever else)
Disposable stuff to measure out resin and the like/stir it
Body Filler of some type(have to research if there are different types/which way to go)

Not planning on working with molds quite yet so I’m not worrying about the chemicals necessary for it. Most questions have been asked and answered but I guess I couldn’t find the right search terms for dealing with rounded curves like that or similiar situations where you need the fabric to move in a way it doesn’t want it.

Thanks

#2

There are a few things to think about when making a small part with tight curves out of carbon.

  1. carbon resists shaping. for something like this you’ll need some type of compression aid (to be discussed later)
  2. The type of resin you use for the final product will matter because of the clearances in the part to the calculator.

because of the clearances that you’re dealing with on such a small part, I’d suggest that you do worry about making a mold and use epoxy and here’s why:

it’s sucha small part, you can practice on it. epoxy has a much smaller shrink rate than polyester. It will be more expensive, but in the quantities that you’re talking about for just that piece to start out with, it’s not going to break your bank. The difference in resin costs alone may be around 20$/Gal to start out with. I would suggest using the west systems 2:1 medium kick mix to start out with. slow kick will take overnight, and you won’t have the patience for that and fast kick may, just may be too fast for you starting out.

BUT, i suggest that you find some other plastic parts to practice on even before this one. any plastic part in similar size and shape will suffice

for something this small you won’t need a “tooling surface coat” but i do suggest that you mix some white dye (for epoxy resins) with some of your resin for your first coat. This is to have a uniformly colored surface which can be inspected very easily when you pull the mold from the plug (plug = original part (JIC))

so you have a white tooling surface, you have the resin, I would suggest simply using an 8 to 10 oz plain weave fiberglass cloth for the mold and use perhaps 8 layers. you won’t need too thick of a mold for a small part like that. and now you have yourself a mold.

then you can wax and wax and wax and wax and pay attention to the corners and curves, those are always the most overlooked parts of mold release prep.

There are a few details that i’ve left out such as after laminating the mold, how do you get it out. I’ll let you think about what i’ve just told you for a little bit and post back up when you’re ready for the next step.

This is a perfect sized part to practice on. and there’s a little more to the entire project that you may think, but we’ll little at a time. When i get home tonight i’ll make another post with the next steps.

I think i’ll have to make an episode I post later simply because i just want to make sure you know how to prep the plug also. Your materials list looks OK for now, we’ll expound on that as I go as well.

#3

Thanks for the detailed reply Jeremy. I went to west systems website at
http://www.westsystem.com/webpages/productinfo/guide/index.htm#resin

And I could not find a 2:1 medium dry mix, I however did find a 3:1 slow dry.

#4

haven’t forgotten about you… well maybe a little… i’ll post up as soon as i can… gotta run to the office.