One thing I have learned with the VHB (Very High Bond) tape is that it responds best to pressure.
With that lesson in mind, I used the VHB tape on the detail pieces. Today I did a few of the panels that are on the bottom of the skin and working my way along.
The steps, as I learned bonding the skins, is simple...
1.) Rough up the surface (sand!)
2.) Wipe clean
3.) Apply tape
4.) Use fingers or roller to promote adhesion
5.) Gently remove paper backing
6.) Apply to roughed up/sanded/clean surface
7.) Apply pressure (clamps)
Here's my progress this afternoon...
The second time around seems to have worked.
After letting the VHB tape set for four days, it was time to get the inner skin ready.
I wanted to make sure I got a good bond, so I roughed up the skin with some 120 grit sandpaper on the mouse sander...
I then went up to some 220 grit sandpaper...
Then I used the buffing pad (looks like a brillo pad) to clean up and give the skin a smooth look. Remember, parts of the skin will be visible once the outer piece is glued out, so we don't want and sander lines.
And then it was time to remove all the paper backing from the tape on the outer skin. This is very slow, delicate work...so if the furry pets are around, lock them up. This is a BAD time to be jittery so make sure you have gone easy on the coffee!
Here's the back of the outer skin with all the paper backing removed, ready to bond...
Here's the end result...using the coin slot holes to line the skins up, I started clamping there and working my way outwards.
I actually started to run out of clamps so I had to spread them out a bit.
The clamps will stay in place for the next day or two so the adhesive can reach full strength.
Well, live and learn...when I went to peel off the paper backing on the 3M adhesive, most of the adhesive came up with it...
It took about an hour to remove all the tape and adhesive.
I took a good look at the skins and realized I should have sanded more aggressively. Whatever is built up on the surface of the aluminum, despite cleaning with acetone, needs to be removed.
Today I sanded the skin down with 120 grit sandpaper using the mouse sander. I sanded until I had the surface scratched and shiney...
And after wiping away any dust/residue, it was time to dig out the tape, razer and scissors and go at it again...
I'm going to let the tape set for 24 hours. Since the tape is pressure sensitive, I used a small socket to roll on the tape, helping the bond.
Tomorrow I'll sand the other skin panel, where this will bond to.
The assembling of the skins is one of the things that all R2-D2 builders fret over.
No one wants to skins to not look right. They are two layers of aluminum and create the beveled look that R2's doors and panels have.
Some use silicone. Some use JB Weld, 3M #77 spray adhesive or any of the instant-mix/fast drying epoxies on the market. All have their pro's and cons.
I used silicone before but it was a bit too thick for my liking.
I used JB Weld on smaller panels and hinges in the past with mixed luck.
3M #77 spray adhesive didn't work very well for me on my first set of skins. I wound up dabbing in a lot of Super Glue in areas that didn't bond well or cracked a few weeks later.
On my first R2, for the rear skins, I used Loctite's 1 Minute Epoxy. A spiral syringe mixes the components and as you would imagine, dries quickly. And to date, it has worked very, very well. The only pause I had using it on the front skins is the adhesive is very watery. With the many panels and doors of the front skins, I just wasn't comfortable using it. I didn't want to deal with drip lines and the sort.
One thing a few of the other builders found is the 3M VHB (Very High Bond) double-sided tape. At 2mm, its very thin and requires a gentle hand to apply. This is the kind of adhesive some use for auto detail pieces, such as trim and so forth.
So I made up my mind and decided to go for it.
First up was to clean the back of the outer skins up, which would require wiping them down with acetone and sit outside to dry for an hour.
After the skins were try and clean, it was time to apply the tape to the skin.
The tape is a bit wider than the panel lines in some spots. Since the adhesive clumps off easily if you aren't careful, I applied the tape then trimmed with a razor blade in the tougher spots.
I'll let this sit for the next 24 hours before the fun process of peeling the paper backing off....then....carefully lining up the skins and clamping together.
Tonight I dug out the center vent surrounds and internals. Putting these together isn't so much difficult as it is a sort of logic puzzle.
The internals are all pre-laser cut and fit together, some areas more snug than others. From my experience on the first R2, I decided to go with Super Glue this time around. It dries fast, clear and holds very well. I used the end of a small screwdriver to tap stubborn pieces into alignment.
I started with the top vent and glued the pieces together, first the base...and then the vent slabs, starting with the two that are the toughest to get at...the bottom and second one. I laid them in place then used the brush to apply Super Glue to the edge.
The lower vent internals required a lot of filing to fit inside the surround piece. Its slow work but with a Star Trek: The Next Generation marathon playing on the ScyFy channel, the time passed quickly!
Yesterday I had to stop work on installing the legs since one of my 12 volt batteries had to be recharged. I use two to create the 24 volts needed to release the Globe motor brake. Once I had that done, I was able to rotate the shoulder hub to the desired position.
I also dug out the R&J dome and placed that back on the frame. R2 is looking sharp!
Next up will be to work on the skins and center vents.
Today I decided to give R2-D2 #2 some attention after largely sitting in boxes for the past few weeks. With R2-D2 # 1 operational, I have pondered many things I would do differently on the the "uber" model.
One thing that has always been a hassle has been putting a screwdriver onto a screw after the fact. While putting together some of these pieces, later on down the line, you need to get at them. Such as the center vent rails...
Ah much better!
I repeated this with the Utility Arm Carrier back plate. The tiny 4-40 screws are much easier to get at with the hex wrench.
Another idea I am going back to is the Globe Rotary motors. The beauty of this newer frame design is that Jerry has kept the old mounting holes from the original frame. Thus I am able to use my original mounting hardware in the new frame.
Next up was to put together the legs and ankles from JAG. He includes a new mounting plate which makes bolting them together a cinch. In the "old" days, we used 4 aluminum spacers and could be a challenge to line up and screw in!
Next up was to mount the legs to the shoulder hub. This went together very slick, largely thanks to doing it all before! I even mounted up my aluminum shoulder horseshoe...
Essentially the only big pieces I am missing are the outer feet. Asides that, its all small detail pieces that I may opt for lighter, resin alternatives.
That's where # 2 is at now!
