RE: [ATM] Carbon Fiber for Spider Vanes

["Dream - Telescopes & Accessories, Inc." <shane@dreamscopes.com>]

Peter,

Sure.  I've got a part in the oven so I'll try to answer this now.

There are quite a few resins with styrene in them so be careful.  Epoxy, to 
my knowledge, never has styrene but the chemists in the composite's 
industry are always creating new resins so there could be.  I know mine 
doesn't.  However, I have a 55 gallon drum of a one part UV curable resin 
that does have styrene.  I use that with vacuum infusion process because 
that process is sealed and doesn't allow the dangerous and very odorous 
styrene to get into the room.  Think model glue from hobby kits when you 
were a kid.  Now think of spreading out a 20 square foot area with it.  If 
you went through the 60's, you'd probably like it...  Unfortunately it is a 
health hazard, joking aside.

If your resin has styrene in it, it will eat the home depot stuff...

Number of layers is just that.  Let me know what ounce weight the goods 
are.  This should have been given on the product when you bought it, 
oz/yd2.  Two layers of 24oz is thick.  Two layers of 4.0 oz is fairly 
thin.  Two layers of 0.75oz is like cheap toilet paper...

Don't use too much of that Super 77.  Remember, it is now getting mixed in 
with the resin you use.  The resin may be affected by the Super 77.  You'd 
have to check with your resin manufacturer.  Just call them and ask them if 
the 77 stuff causing any issues with their resin or do you still get full 
properties even when 77 is part of the lay up.

They use that same technique when laying up 50-100+ foot yacht (among a 
great many other parts, across industries).  There are often corning or 
vertical segments.  This is for infusion though.  Infusion allows all dry 
goods layers to be laid in first, flow media is added or part of the fabric 
and/or core, then all is bagged and pulled to a full vacuum.  Once all air 
is evacuated, resin lines are opened and the part wets itself out, all 
inside the vacuum bag, so no fumes or health problems.  Infusion can be 
somewhat easy but some times it is very tedious.  I've found that it can't 
give me the resin contents I want.  Not in my R&D on it so far.

Putting weight on it helps but are you doing any vacuum bagging materials, 
like peel ply and breather?  Use these and the weight will help push excess 
resin into and through the peel ply and into the breather.  If you really 
want to reduce your resin content and feel you will be making projects like 
this for quite a while, you might want to invest in a small vacuum.  Just 
make sure you buy the right product.  It has to be a vacuum pump that is 
meant for continuous duty.  I found a small 1/8th HP pump on e-bay many 
years ago but now I also have a 1HP vacuum pump.  For me having more than 
one is very useful, for numerous reasons.  Vacuum bagging definitely 
complicates things just because it is a lot of extra steps.  Buying the 
materials in small quantities will probably add up for a weekend warrior too.

Try rounding all edges of your bearings so the fabric turns the corners 
more readily.

Vacuum bagging won't make stiff, woven goods do tricks.  Some times it can 
help but making parts with cut outs like that are usually multi step 
processes.  They are doing a great many composite parts with injection 
molding.  That's not an option for you though.  Injection molding is costly.

No, you really shouldn't have to worry about the Tg if you paint it a light 
color: white, cream, etc..  That's what a lot of kit plane guys do.  They 
use resins that are as little as $15/ gallon and have a Tg as low as 120F.

Fundamentals are very important and I have yet to mention some of the very 
basics.  Clean or keep clean any parts you plan to bond to.  If you use 
epoxy, buy an accurate scale, something below 1 gram accuracy is 
good.  Epoxy is very sensitive to improper mixing.  It won't react 
correctly unless it has the right amount of material.  Polyester, 
vinyl-ester and the like don't really care how badly you mixed them.  They 
will either cure faster or slower based on which way you incorrectly mixed 
the two parts of the resin.  Just mixing the resin in the cup is an "art" 
in itself.  Scrape the sides every five or seven turns, scrape the mixing 
stick at that time too.  Mix for two minutes or if you are like me mix for 
three to four.  Not taking an extra minute on stir time and having a $1000 
part fail due to that fact will makes a person slow down a little.

There are numerous other fundamentals.  There are numerous books on this 
subject and of course, there's the Internet.

I have to run.  Thank you.

Sincerely,
Shane Santi
Dream - Telescopes & Accessories, Inc.
http://www.dreamscopes.com
610 - 365 - 2833

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