stupid fiberglass questions

[Aaron]

I'll post a pic tonight, but I did my first layup this weekend, just a simple 6 ply BID layup to check technique.

 

Rutan's book says it should be 10.5 -11 Oz, anything heavier and you're adding useless weight to the plane. my first one checked in at 11.5, so I have some work to do.

 

My question is this-how do you get the dang air bubbles out? I'd stipple and stipple and stipple, but it only seemed to add bubbles after a point. should there be _NO_ bubbles at all or are a few acceptable? the bubbles are less than 1 mm across. There are no white patches of glass.

 

Any thoughts or tips would be appreciated.

[dust]

Don't stipple at all, can't remember the last time i stippled, only in hard to reach inside corner where glass wants to fall out.

 

wet out layers 1 to 4(one at a time of course), pour epoxy on, move it around with your sqeegee. put the 5th layer on, and no epoxy. Go have a 1/2 cigarette, come back and it will be wet out. put the sixth layer on go have the other half, it should be wet out. if more epoxy is needed lightly brush a little on, not until clear, just brush a little on, go sweep the floor a little.

 

Drag the squeege accross the layup with some preasure and lift up in middle of layup, if there is a line, too much epoxy, if no line = good.

 

If you want add a little heat with hair dryer on top layer, but just not too much as you could dry it out too much.

 

You will the epoxy liquify rapidly.

 

What is right squeege preasure, if the layers are moving around = too much, see you should have bought my hair dryer.

[John Slade]

can't remember the last time i stippled

I feel for ya, Mike

 

Aaron - you might like to try the 'poor man's vacuum' or 'plastic peel ply' technique described in my tips section http://kgarden.com/cozy/tips.htm

 

I learned about this method part way through my fuselage and have used it ever since. It gets rid of all the pesky pinholes which are caused by the tiny air bubbles. I believe this tachnique makes for a lighter, stronger part.

 

The technique Mike describes works best with a low viscosity epoxy like MGS, straight out of the hot box at 110F. Follow his directions, peel ply where specified in the plans for bonding, then add 4 ml plastic and squeege with a hair dryer. If there are any white areas returning after the squeege passes add more epoxy. Use multiple strips to cover complex curves. Dont worry about the creases from the plastic folds. These mostly go away when you squeege, and those that dont can be easily sanded off after cure. Peel the plastic off after cure and you'll see a nice smooth gloss finish. Peel the cloth peel ply off and you're ready to bond. If you need to bond where you didnt put cloth peel ply, sand the smooth epoxy surface. No problem trying to sand in the weave because the weave is compressed flat.

 

Try it. You'll like it.

[Aaron]

From my smoking days 1/2 cig is roughly 4 mins, thanks for the insight (yeah I should've bought your hair dryer...)

 

So with the hair dryer, no more tiny bubbles?

[John Slade]

>So with the hair dryer, no more tiny bubbles?

 

Not until the wife throws you in the pool for stealing her hair dryer. Once I borrowed it, then put it back. Caught hell when she came outside 20 minutes later with it stuck to her hand. Another 30 minutes cure time and I'd have been home free.

 

I went through two wives and three hair dryers before trying the heat gun that came with my shrink wrap machine - much better, and no more trouble with the wife.

[dust]

i think your problem was the stippling, no stipply,just move the epoxy around/ squeegee and get the extra out on the last layer or layers on thick layups (most of the plane is just 2 or 3 layers), and the heat just makes it lighter, but isn't necessary. Glass wets out better from below, thats why you leave bottom wet.

 

We tried a heat gun and ours was too hot, 1600 watt hair dryer was the trick, (for us)

 

This is too much writing, plane day is saturday, he he he

[Wayne Hicks]

Aaron:

 

I am a faithful stippler. And with good reason. First, the education chapter says to stipple the layups. Second, the Rutan composite video explains that stippling is a necessary part of laying up fiberglass. But why stipple?

 

Stippling does 3 things:

 

(1) On the first layer, it helps to compress the fibers (BID especially) against the micro slurry and foam. It displaces the very tiny air bubbles trapped in foam by the micro slurry. It allows the micro to wick up to the glass to make the most effective bond.

 

(2) Stippling removes most of the air bubbles. BUT WATCH OUT! Stippling TOO HARD WILL PUT AIR BUBBLES into the layup.

 

(3) Stippling draws the excess epoxy up to the surface so you can remove it with the squeegee. This is especially important when laying up multiple layers of cloth. A layer of cloth will absorb epoxy only up to its saturation point. What doesn't get soaked up is EXCESS. If you don't get it out, it's EXTRA WEIGHT. You draw out more epoxy by stipling and squeegeeing than you can do by only squeegeeing. By drawing most of the excess epoxy to the surface first by stippling, you don't have to squeegee as hard, thus you lessen the chance of disrupting the cloth.

 

Sounds to me like you've been stippling too hard. Try going a little softer on the brush.

 

Like I said, I'm a faithful stippler. I stipple and squeegee every single layup. I'm not a big fan of leaving alot of epoxy for the next layer to soak it up.

 

So for layups with multiple cloth layers, I stipple the first layer and squeegee moderately, leaving very little epoxy for the next layer. So little in fact that the next layer of cloth will not totally wet out. I then ADD IN (pour on or brush on) j-u-s-t enough epoxy to wet out the final layer.

 

I also use a heat gun religiously to heat up the areas that I'm stippling and squeegeeing.

 

Yeah, it takes longer to stipple and squeegee each layer, but I've been rewarded witk low parts weight throughout the build process.

 

So STIPPLE! But go easy. Squeegee. And use gentle heat.

 

================================

Wayne Hicks

Cozy IV Plans #678

http://www.maddyhome.com/canardpages/pages/waynehicks/index.html

[tim2542]

I'm just a chapter 5 rookie but I've found that I don't stipple much either unless there are more than 2~3 layers, then the stipple roller from wicks works very well for bringing epoxy up from below, which I think may be the key to getting a light lay-up with many layers. Tim