Sep 13, 2018     PK training       Category: C03 Training

where I start as a builder...

I like building as much (and maybe more) than flying. I've worked in wood (helping with EAA's Bleriot reproduction), in tube (overhauling and recovering my 1946 PA-12) and in aluminum (the BD-4 and RV-6a). In February 2016 I took a SportAir workshop on composites, and that gave me the confidence to consider a composite. The daily discoveries from working in composites should make the build all the more enjoyable.

The Cozy is also going to be different in that it is plans built. All of the more popular amateur built aircraft are kits; most of the work is in assembling supplied parts, and the sub-assemblies become an airplane. With the Cozy, you build the parts. If it comes out wrong, you figure out what went wrong, trash the first effort and work to build it better. I figure I'm going to end up with 1000 lbs. of airplane, 1000 lbs. of scrap.

My building and flying experience was in Hartford Connecticut, coached by expert aircraft mechanics working at Pratt & Whitney, Sikorsky, Kaman, et c. They wanted to keep me safe, and that started with safe from my lack of experience. I learned standards of work more than anything else:
- Check against plan dimensions before, during and after
- A hole is a precision cut
- Every rivet is a 4 step process
- The only approved shortcut is the published procedure, because that way you don't do it over
- Every aircraft regulation was written in blood
- Et cetera.

The biggest challenge will be doing this build without the support of the close circle I have relied on in the past. I think I'm starting to build that network here in Florida, and I'll work on the networking during the build.

I bought and experimented with fiberglass, foam, epoxy and fillers. I'm like most new workers in composites - wow, how amazingly strong a good layup can be! The experiment pieces are below - the wing section, gear leg fairing and "T" section were done at the Sport Air workshop. The 3-ply load-bearing tablet was done per instructions in the Cozy plans. I used the "poor man's pre-preg" of wetting out the weave between sheets of 4 mil plastic sheeting.

I am using two types of epoxy - Aeropoxy for load-bearing laminations and West Systems for the fill-and-sand work (500 hours of a typical Cozy project). {Later edit - I ended up building a library of different epoxies, with toughened, fuel proof, super clear, et al.)

  Dec 28, 2020     Plans Review - (100 hours)       Category: C03 Training

I started looking at other build logs:
Jean Pierre Alagnoux at https://www.flickr.com/photos/cozyjpa/albums/with/72157699427033972 (78! albums) and
Wayne Hicks at https://ez.canardaircraft.com/www.ez.org/pages/waynehicks/index.html

Based on the very best advice I jumped to work on painting and now electrical. As this project gets out of sequence, I need to get comfortable that all steps were done in prior chapters. This is taking a long time, particularly when I seek comprehension of each step done on the very best projects, the ones that were not satisfied with the plans. I don't know that this should count as build time, but it is one heck of a time vampire.

  Jan 21, 2004     Test layup #2 - Confidence - (1.3 hours)       Category: C03 Training

In all, this is a pretty basic layup, and it went by a lot faster than I expected. I incorporated my changes from the flat layup. This time, I stippled with a brush to remove all visible bubbles, even the tiny ones present in the epoxy due to mixing. I also incorporated a trick suggested by several other builders, that you not only use plastic underneath the layup to protect the bench, but also on top of the peel ply. The plastic allows you to perform a final squeegee step to remove epoxy and air bubbles and prevents air from being reintroduced. This worked very well... for the top surface. Well, you can see the results. The 4mil plastic is actually not all that malleable in terms of compound corners, which this layup contains. I discovered the hard way that it was difficult to bend around the edges without it pulling the top surface off the foam block, or lifting the peel ply right off the layup.

This caused all sorts of problems. First, by picking the peel ply up it created a peel ply air pocket. That's not a big deal because the peel ply doesn't stay there, but it DOES mean there is an area where peel ply didn't touch the layup, so I would have to sand this spot and I would also expect extra epoxy buildup here. This area is circled in red.

More important, I found it very difficult to actually do the squeegee work in the lower portions, under the complex bends. Because of this I ended up with much more epoxy on the top of the peel ply than should be there, and it became impossible to remove - epoxy doesn't stick TO peel ply, but a 0.5mm sheet of it on top of the peel ply with fingers down through the mesh sure HOLDS it there. I'd have to sand the excess epoxy down, then sand the peel ply off to be sure it was fully removed before doing another layup.

In all, I think I will leave this trick to flat layups or areas where there are gentle curves and great benefit to be had, like on the wing surfaces. Nonetheless, the layup was a success - it's epoxy rich and ugly as hell, but it easily held my weihght, and I don't think I really need to practice sanding - I'm moving on.

During the layup I was also reminded of a complaint I forgot in all the fuss in the flat layup - loose fabric strands. These get all OVER the place if you let them get onto your brush, gloves, or squeegee. I think in the future I willl simply take the hit and add an inch or two to each cut to keep these away from the areas I'm working in during the layup. I could do a temporary selvedge with masking tape or similar, but because the BID is so malleable, I keep having problems with my 4" cuts becoming 3" strips, even when I roll the fabric; cutting things oversized will prevent problems there in the future as well.

  Jan 21, 2004     Test layup #1 - flat layup - (3 hours)       Category: C03 Training

Some advise you to dive right into the first real chapter, but I wanted to proceed with the confidence layups for three reasons:
1. I wanted to show them to family members.
2. The plans say the flat layup (six plies of BID) can be useful later, and I believe them (grin)
3. My first few feet of the BID were warped beyond my satisfaction for actual use, despite the ability to reshape BID. This gets them out of the way.

I'm glad I did. My epoxy effort only wet out the first three layers of the BID because (hardy har har) I tried doing all six at once. Oops. I also had problems with the epoxy setting up too quickly - I was using Fast hardener to test for this very thing. Slow is probably too much in the wrong direction - I only needed another 5-10 minutes. I will probably mix Fast and Slow in the future - this is allowed for MGS. I will try again tomorrow, this time with more epoxy and wetting out each layer one at a time.

I am now using a roughly 30/70 mix of Fast and Slow. Since I am measuring by weight, my process is not rocket science. I place an empty cup on my scale and zero it. Then I fill the cup with as much resin as I think I want, by eye, allowing for the fact that hardener will join it. I weigh this, and look on my chart for the closest matching weight, then add a drop or two of resin if I'm not on an exact number. The chart gives me a final weight with the hardener, so I then just add equal squirts of each type of hardener in the ratio I want until I reach the target weight. I can get 1 drop at a time out of the pumps if I'm careful, or accuracy to a third of a gram (one drop's weight) in the entire batch.

This is a really easy and fast method of measuring out epoxy. If I want it to cure a bit faster, I lean more (or all the way) toward Fast hardener, and vice versa for more setup time. And there's basically no cleanup involved - the pumps don't drip or leak, and if they get gunked up over time I'll just replace them. The only drawback is that my scale only goes up to 500g, or about 17.6 ounces. That's about a medium cup full of resin - a 16 fl. oz. cup would contain more than the scale could measure. This is OK with me - I don't intend to work with that much at a time anyway, for fear of exotherms. I would rather mix 2-3 smaller cups to get the desired quantity.

My flat layup turned out to be 10.5 ounces, which is on the lighter side. I don't attribute this to an excellent layup but rather to the higher amount of tiny bubbles present. I don't really have any large air bubbles to speak of. However, I did have a large number of tiny bubbles that none of the pictures show well. There's enough there to be a concern (15% or so, I'd say) but the opacity isn't all from that - I peel-ply'd one side and that's the cause of the milkiness.

I also have some fabric dings I made with the squeegee while doing the layup, and some embedded aluminum foil bits and streaks on the back side where epoxy crept underneath the gap between my two sheets of foil (I laid foil over the plastic on my bench to see how well it peeled). None of these issues justify doing this layup over again. In the future, I will focus on my stirring technique for the epoxy mixing step. I believe this is where the tiny bubbles were introduced. Also, I have rounded the corners on my squeegee to prevent them from catching the fabric. Finally, I'll only use plastic instead of foil.