Tricks & Methods

This chapter is dedicated to the methods and tricks I used throughout my Cozy building journey. By no means are these my ideas… in fact, I learned most of them from builders before me, and friends & neighbors who contributed their invaluable advice to support my goal. Therefore, I am documenting them here and hope they can be useful to the next builder. I wanted to acknowledge and give a BIG THANKS to those who came up with these great ideas – well, you know who you are!

Transferring Drawings onto the Foam

I transferred the drawings onto the foam using a tracing wheel they use for sewing (I learned this from the Cozy forum & various web sites). First, I tack the drawings on the foam with a thumbtack and run the tracing wheel along the lines of the drawing. The spokes on the wheel put a string of ‘indents’ on the foam. Surprisingly, the tracing wheel tracks a straight line quite well even in free hand. Remove the drawings and connects up the dots with a fine felt tip pen. Though the tracing wheel leaves a bunch of holes on the drawings, they are readable and can be reused – wonder how I know (hint… you normally have to re-trace & remake a part if you screw up). Regardless, this method worked very well!

 

 

 

 

 

Rounded Corner Templates

I did not like the inconsistencies of inside rounded corners I made on the Instrument Panel – simply because I do not have that perfect freehand skill – like a professional carpenter. There's got to be a better way… I went to a machine shop and had set of angled templates with round corners made (.125", .25", .5" & .75" radius respectively). The templates are .25" thick aluminum. With the appropriate template clamped onto the top of the inside corners of the Instrument Panel, I used a flush trim router bit and ran it along the edge of the template. I used ˝” diameter bit or smaller – you can find them in most hardware stores or on the Internet. These templates help shape the foam and fiberglass to a nicely rounded inside corner every time!

 

 

Heat Tent

One of the contributors for poor part quality on my parts (discussed in Chapter 4) was due to low curing temperature (below 70F). Therefore, a heat tent, of sorts, was in order. Since my Cozy factory is in a large warehouse without heating and cooling and it would be impractical to heat up the entire warehouse, I needed to find ways to provide local heating.

 

The local heat tent is made up of three 4'x8' foam panels (~$10 each). The three panels provide enough material for a 4'x10'x2' tent (as shown). I also cut up some scrap foam strips and glued them to the tent corners and joining edges - making the tent 'box' much more rigid and sturdy for handling.

 

The heating unit is made up of two 100 watt light bulbs, a small fan (to circulate the air inside the heat tent) and an in-line thermostat. Once the tent is in place, I slipped the heating unit inside the tent and plugged in the power. The heating unit was able to keep the temperature inside the tent within 80F constantly - just about perfect. Time will tell if it is worth the effort.

 

 

 

Home Depot Sanding Stick Special (HDSSS)

I read this from someone's site and followed... I went by Home Depot and picked up several paint stirrers.  They have two sizes - you'll find them both useful. I laid a 8"x11" sand paper face down and brushed on left-over epoxy on its back. I then placed the paint stirrers on the epoxied side - butt up against each other. After cure, I used a razor blade and cut along the edges of the paint stirrers. You'll end up with sanding sticks for all occasions. I used this to sand down the heat duct at the aft spacers (Chapter 5). Worked great!          

 

 

 

 

 

 

 

 

Squeegees VS Credit Cards

I started with a rubber squeegee during my practice lay ups and early part of Chapter 4. I soon got tired of cleaning them - especially when I forget to clean them by the end of the day. Replacements are somewhat costly in the long run. Then I started using credit cards instead of the rubber squeegee (I am sure this is not original). I get a lot of junk ones in the mail all the time, therefore, I have a constant supply of squeegees for FREE!

 

Here's my experience with them:

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Firstly, I can wipe the epoxy/micro off the cards easily and if I forget, I just toss them - they are FREE;

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Note that these credit cards comes in different thicknesses. I like the American Express ones for applying micro onto foam because they are a bit thinner and tend to bend and slide over the foam nicely (ie. they won't dig into the foam). On the other hand, I like the Delta Airlines ones better for applying epoxy on glass because they are a bit firmer;

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Sometimes I trim the credit card into strips for tight places (e.g. applying flox to round off the acute corner at the base of the front seat back in Chapter 6);

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Sometimes I sharpen or dull the contact edge of the card for rubbing down the peel ply or plastics.

 

Generally, they worked well for me. You may want to try them out... Just make sure you use the junk credit cards and not your significant other's . As a matter of fact , I think I am going to write a thank you note to American Express and Delta Airlines for the free squeegees...NOT!

 

Removing MG-4 Bushing from the Rear Landing Gear Bulkhead

This is one task I do not wish any builder will have to face. However, if you must, this is one approach that made my life a bit easier. According to plan, MG-1, MG-2 and MG-4 need to be floxed in place to support the landing gear shaft. As I did mine, the MG-1 moved (mysteriously of course) just a bit during cure, such that the landing gear shaft will not go through.

 

After I popped off the MG-1 plate, the bushing was still in tact. To push it out, I used a knock out punch for the task...

 

A knock out punch is a tool commonly used in the sheet metal manufacturing processes for shearing a pre-determined hole (size & shape) in a sheet of metal. It will provide a nice clean hole compared to using a jig saw or band saw. A knock out punch consists of a base, a pre-shaped die (i.e. the punch) and a threaded screw through the center of both components. The punch comes in round, square, rectangular shapes and in variety of sizes. As you tighten the screw (shown), the punch will eventually shear a nice clean hole out of the sheet metal.

 

 

 

 

 

 

 

I used the same idea for pushing the MG-4 bushing out of the LG bulkhead, except I reversed the orientation of the cutting die (shown). As I tightened the bolt with a socket wrench, the back of the punch pushed the bushing (nice & flat) forward until it was flush against the glass. I removed the punch, added a drop of oil on the exposed bushing that is close to the glass, reversed the punch direction and worked it back in. By repeating the process a couple times, the bushing came right out!!!           

 

 

 

 

 

 

 

Applying and Smoothing Flox

I picked up the general approach to this technique from one of many web sites I read (don't remember who's) before I started building the Cozy. It turned out to be one of the techniques, that I used often, for making smooth flox fillets. Here's an example of how I make my flox fillets:

 

I was applying a flox fillet around an aluminum hard point, but this technique works on just about any fillet application as called out in the plans. I first applied DRY flox around the edges of the aluminum hard point. Its a bit lumpy and does not have to lay perfect. Just make sure there is an even amount (roughly) along the fillet edges.

 

 

 

 

 

 

Right before I was ready to glass over the hard point, I use a soft brush (or a brush with longer hair (i.e. >1" or so) and dip it in pure epoxy. Remove excess epoxy from the brush by sliding it over the edge of epoxy mixing cup as you always do. Then brush over the DRY flox LIGHTLY. The flox will absorb the epoxy from the brush and 'melts' (smooth) to shape nicely. You'll get the hang of it once you have done it...

 

 

 

 

 

 

Apply pre-wet glass over the entire hard point and fillet. Touch up the fillets lightly with the soft brush, to desired perfection.

 

 

 

 

 

 

 

 

Fitting a Small Washer in Tight Space

There are times that you need to hold a thin washer in really tight spaces such that you can fit a bolt or rod through it. A good example is in Chapter 12 when installing the elevators to the canard. There is no room (even for pointed nose pliers) to hold the washer on its sides nor can you grab onto its flat surface while trying to push the rod through. Here's how I did it:

 

I used a small piece of masking tape and stuck it to the edge of the washer - now, the washer is dangling by its edge. Lower the washer in the slot, stick the bolt or rod through the center hole of the washer, pull off the masking tape and you are done. Its simple and works great!

 

 

 

Brushes, Re-use Or Not-Re-Use

You will find many discussion in the archives regarding re-use or not-re-use of the brushes. I always felt that brushes are cheap, especially when you wait for a sale from Harbor Freight and stock up. I used it once and tossed, no cleaning, no mess... Besides, I tried to clean the brushes a couple of times and can never re-use them because they stiffed up like a chisel afterwards.

 

I got a chance to talk to Paul Stowitts (who prefers to re-use his brushes) a while back and picked up some of his cleaning techniques. I then realized I missed a couple of cleaning steps... A bit later, I included those missing steps and to my surprise, it worked very well. The brushes stayed softer than new ones and NO loose hair ever again - I like it!

 

Here's what I did for cleaning and preparing the brushes for re-use:

Step 1 - After use, I squeezed out the residue epoxy with a paper towel (those 1/2 sheet ones or whatever I can get my hands on). I normally squeezed it about 3-5 times, using the same paper towel.

 

 

 

 

 

 

 

Step 2 - I soaked a new paper towel (those 1/2 sheet ones) with Acetone and wrapped the wetted part over the used brush.

 

 

 

 

 

 

 

Step 3 - I tucked the whole thing inside a sandwich bag and wrapped it tight around itself.

 

 

 

 

 

 

 

 

Step 4 - I squeezed the brush part between a vise or some weight. BTW, you do not have to kill it with the vise.

 

The next time you need a brush, just take it out of the vise and unwrap the plastic. I like it, not because of cost reasons. It turned out to be a much softer and smoother brush and works better than new ones. As I mentioned, no loose hair either.

 

 

 

 

 

Drilling a Straight Hole

There are times I need to drill a hole vertically through a cylindrical part, such as a tube (Chapter 16) or a bolt (Chapter 13). For one reason or another, the V-block was not handy, the part was too small or the hole just did not need to be THAT perfect - one of those quick tasks... Here's what I do...

 

As shown (left), I was drilling a hole through a AN3 bolt for a cotter pin. I first clamp down the bolt in a vise and place it under my drill press. Then I lower the drill bit against the top of the body of the bolt. Then I slip a razor blade (or a straight metal ruler) between the tool tip and the bolt body. If the blade is level, the drill bit is dead center to the apex of the bolt. On the other hand, if the blade is tilted, you are off center. Move the vise (with the bolt) a bit until the blade is level. A simple, but very effective technique.   

 

 

 

 

 

 

Center Section Spar & Wing Match Drilling Bit

To use this Tool set, you must have an access hole on the under side of the Center Section Spar (per plan). In addition, you are given the locations of the wing bolts in Chapter 14 Page 5. I drilled a 1/4" hole at each of those locations (i.e. Aft face of the center section spar). Then I transfer a matching set of these 1/4" alignment holes onto the forward face of the center center spar. Note that the FF alignment hole does not have the same BL location as the AF ones (hint: look for the 2.02" dimension).  These alignment holes were intended as a guide for drilling the matching hole between the Center Section Spar and Wing hard points such that the bolts comes out perpendicularly to the aft face of the center section spar. Once you have the wing and center section spar lined up and secured, then this Match Drilling Bit will come in handy as follows...   

 

The Match Drilling Tool set comes in 2 parts - the funny looking (customized) drill bit and the 1/4" drill attachment rod.

 

 

 

 

 

 

 

I used an collapsible magnet to hold the Drill Bit and stick it through the access hole at the under side of the Center Section Spar. Then I maneuver the drill tip through the 1/4" alignment hole at the aft face of the Center Section Spar.

 

 

 

 

 

 

Then I feed the 1/4" drill attachment rod through the 1/4" alignment hole (at the forward face of the Center Section Spar) and into the back end of the Drill Bit. Now the Drill Bit is hanging between the two 1/4" alignment holes of the Center Section Spar. Pull out the magnet.

 

 

 

 

 

 

Carefully rotate the 1/4" drill attachment rod such that its flat face sits against either one of the 2 set screws. Use an extended Allen bit (as shown) and tighten the set screw. Attached a hand drill to the end of the drill attachment rod and start drilling.

 

 

 

 

 

 

 

It is important to note that a more powerful drill works much better. I used a DeWalt 7.8A drill instead of my other Skill 3.5A electric drill. It cut down my drilling time by 75%. It may be a good idea to make a trial run on a scrap piece of aluminum - just to get a feel for the Tool before going for the real thing!