The Fan Project

Spent ~2 hours making a jig to make the template in the below picture, which I'll use to make a depth cut of 3/8" in the mirror box for the fan control switches.

After positioning the template I made last night, I clamped it down with two clamps (one of which is seen in the pic), and routed out the area for the fan control panel. I slightly overshot my target depth of 3/8" at 7/16" but the amount of overshoot is inconsequential. Before making the cut, I double checked the positioning of the template, and triple checked the depth of the bit, and made absolutely sure the depth stop on the plunge holder for my router was tight before proceeding. On the router bit, I made sure the set screw in the depth stop was tight so that the bearing would not walk up the shaft which would result in cutting into the template, and by extension, exceeding the template perimeter on the mirror box as well. Ask me how I know to check this! If I screw up here, fixing the veneer would be quite a laborious and time intensive process. I can do it, it's just very time consuming.

Also of paramount importance is to make sure the top of the cutting bit is above the surface to be cut. If it is just below the surface by a fraction of a millimeter, a fibrous cut would result, and could damage the veneer.

The cut went well. Perfect. I couldn't be happier with the results. So I put the mirror box back in the rocker so I could clean up the area.

Next, I prepared the cut area with masking tape for chiseling out the rounded corners so they are perfect 90° corners. The masking tape helps me see where I need to chisel. The corners being 90° makes veneering easier, and it looks visually consistent with the square nature of the mirror box.

After chiseling, I sanded down the edges so that the sides look straight and clean with respect to the corners. Here, it's important to frequently vaccum the sand dust, otherwise it compacts in the corners and prevents the sanding block from reaching into the corners. I actually had to use a chisel to get the compacted sand dust out for vacuuming. The bright shop light is to help me see that the corners are in fact, straight with the sides.

Then I again put blue masking tape around the fan control panel, for coating with epoxy, of which there will be two coats. This seals the newly exposed wood, and prepares the area for veneering as epoxy bonds well to itself. I do not want epoxy seeping into the wood during the veneering process, which can result in veneer failure.

After chiseling, I sanded down the edges so that the sides look straight and clean with respect to the corners. Here, it's important to frequently vaccum the sand dust, otherwise it compacts in the corners and prevents the sanding block from reaching into the corners. I actually had to use a chisel to get the compacted sand dust out for vacuuming. The bright shop light is to help me see that the corners are in fact, straight with the sides.

Then I prepared the veneer by taping together two 6" strips of Cerejeria. Since I am positioning the grain pattern to be parallel with the rest of the mirror box, this puts the veneer diagonally, which is why I need two strips of Cerejeria as my rolls of Cerejeria is 6" in width at approx 10 feet long. After taping together the two strips, I put the template I built on it to trace out the rectangle cut-out.

Then I applied blue tape along the entire backside so that the veneer would not split and crack along the grain lines during the cutting process. I also lined the perimeter of cutout with blue tape so tearing would not occur at the corners.

After cutting the veneer, it was time to position it to check fit, and adjust as necessary. The torn corner on the lower left is no problem and won't show in the final result.

For adjusting the final fit, especially with delicate veneer, I staple down a piece of fine grit (220) sandpaper and slowly sneak up on the final fit. During this step, I taper each of the four corners of the entire piece so the fit is not as fussy. This is not a concern and won't be seen in the final result.

Then, I laid down the epoxy, and ironed down the veneer using three counterweights so the entire veneer undersurface makes contact with the epoxied surface on the mirror box. You can see how the veneer pretty much exactly lines up with the diagonal grain on the mirror box, as evidenced by the arrows:

Then I cut out a piece of freezer paper using the template I built, so that the clamping shims I plan to use, which are made of wood and seen in this picture, do not bond to the veneer because of bleed through, which I anticipate will occur and will not be a problem.

The clamping process, which is a little weird here just because I grabbed the first piece of wood I saw in my garage, which happened to be the circle jig I made for my router. I did not feel like going out to the shed to get a smaller and more square piece of wood. Epoxy does not require tremendous clamping force. I do not make my clamps tight when I veneer as I don't want the epoxy spread out too thin.

(left below) All clamped down. Tomorrow evening, I will veneer the edges. That's always a little more involved but do-able.

(right below) The clamps were removed after 24 hours, and the fan control panel veneer was sanded down to provide a smooth mating surface for the side veneer. I sanded down the epoxy squeeze out along the 90° edges using folded up 180 grit sandpaper so that the side veneer would seat properly and uniformly. Any scratches from sanding across the grain will not be visible since it will be under the side veneer.

The faded color of the veneer is normal in the sanding process and it is not a problem.

A wipe down with denatured alcohol shows me that the sanding looks complete to me. I'm now ready to start cutting the side veneer. Tonight, I will only do the long sides. The short sides will be veneered tomorrow. It's easier to clamp two sides at a time, instead of four.

 I prepare the veneer by covering a side of it with blue masking tape to hold it together during the cuts. Veneer cut down to the small size of the sides will crack along the grain- no getting around this. The blue masking tape is a must to hold the tiny strip of veneer together, especially since I'm cutting across the grain. Then I put the veneer down into the fan panel to mark my cuts with a pencil.

After I've cut my strips and test fit them, I'm now ready to epoxy them in. For this kind of veneer project, I prefer epoxy out of the freezer. Aged epoxy out of the freezer tends to be viscous, which is perfect for this particular veneer run. Epoxy running down the sides and pooling on the surface is not what I want. Plus, viscous epoxy is tacky, which I like for vertical veneering since the veneer stays where I put it. 

I do not remove the blue masking tape when putting the veneer in. Doing so will tear the veneer apart and make the job 1000x times more difficult.

All epoxied in. I have blue masking tape to stop the strips from shifting when I put the clamping shims in. The masking tape also prevents a piece of veneer from running on top of the other since I have two pieces buttressing each other on each side. The freezer paper prevents the wood shims from joining to the veneer.

All clamped up. An unusual clamping situation, to be sure, but this gets the job done. Especially important are the corners- veneer in corners tends to be weak because clamping is difficult in those places. This clamping arrangement ensures that the edges at the corners are clamped. Tomorrow, the short sides will be veneered.

Ok, after 24 hours, I removed the clamps for the side veneer and immediately was met with the consequences for being lazy with the clamping surfaces. Normally, I use freezer paper on any clamping surface, as you saw when I made the wheel barrow handles, where the acrylic blocks were wrapped with freezer paper.

The epoxy bonded to the wood shims that I used as the clamping surfaces. When I saw this, I realized I was probably not going to be able to veneer the short sides tonight. I have a lot of work to do to clean this up.

About 40 minutes later, after careful manipulation of a razor blade and a wood chisel, I cut the wood shims from the cured epoxy and removed them.

After a little more work with the wood chisel, I cleaned up excess cured epoxy from the edges. Now I'm ready to start veneering the short sides. An unexpected result, as I did not expect to veneer the short sides until tomorrow. It's not completely cleaned up, but this is good enough to start veneering the short sides. After the veneering process is complete, I will do the final clean up and a sand down, which will make the veneer blend into the mirror box.

The ridges look high on the veneer. I want this, as a too low ridge could expose the Baltic birch plywood. The extra height is to give me a margin of error when working the veneer. It's also a little easier to cut, as the degree of difficulty increases the narrower you cut veneer.

Here, I'm ready to lay down the epoxy. Like last night, I've used aged epoxy from the freezer for a nice viscous lay down of the epoxy. I've prepped and cut the veneer, which are backed with blue masking tape as seen off to the sides in the picture below. I've also learned my lesson, and masked my shim blocks with freezer paper to prevent bonding to the epoxy.

All clamped up. A most unusual clamping solution, but this ensures the entire veneer surface is clamped down, including the edges.

After 24 hours of clamp time, I removed the clamping shims and masked off the perimeter with blue masking tape to protect the mirror box veneer while I sand down the high edges. I started with 180 grit sandpaper affixed to a sanding block I made. When I sand delicate edge veneer, I always start with a high grit to gently sand down the sharp edges that, if caught in a lower grit sandpaper, can tear. Once the edges are smooth, I dropped down to 100-120 grit to get the edge flush with the mirrox box surface. This takes time, patience, and many small breaks.

If any small pieces splinter off, I save them in a small bowl in case I need to epoxy bare patches later (I didn't need to for this project). Yes, the mirror box veneer  has scratches from the sanding. This is OK and a normal part of the process. The blue masking tape limits this, to save me time repairing the veneer.

The edges are pretty much down to where I want them. Now it's just a matter of taking off the masking tape so I can get a better look of where I need to sand. In the picture below, you can see raised epoxy that bled along the long and short sides, from the veener that was clamped. This is why I take the masking tape off, as the mirror box veneer helps me spot the raised epoxy and decide on a strategy for the next step. What the picture below tells me is that I need to knock the epoxy down, and blend the edges since they look choppy. This is normal.

While I'm knocking down the raised epoxy, I check my work frequently by vacuuming and wiping down with denatured alcohol so I don't sand down and through the mirror box veneer! If the veneer very near the edge of the fan panel starts to look gray, I know I've gone too far, and I stop. Veneer turns gray before you go through it down to the plywood.

I decided to take a break from sanding. At this point I still need to work on blending the edge, but I've put that on hold to switch to making a model for the fan buttons to test my placement. The top button is for the front fans (corner fans) and the bottom button is for the back fans. This makes sense, because when you look at the top of the mirror box, as one often does when behind it and the scope is pointed 45 or below, you are looking at the top of the mirror box, and each button physically corresponds to the location of the fans they represent, as seen from the top.

I did not want to have to think when toggling the fans on off. For example, I did not want to have to think, left for back fans, or was it the right button for the back fans? The button placement eliminates any ambiguity.

The above model was my first try. After the 2nd model, I made one more adjustment, and went ahead with placing the pilot holes. My first and second model had holes that were slightly crooked on the vertical axis. Notice how the buttons are too close together in the below picture, unlike in the first model where they were too far apart. 3rd time's a charm right? Below are the pilot holes.

Next, I drew a center line along the entire length of the fan panel to help me center my battery voltmeter. Then I masked around this area, and drilled four holes, and cut out the rectangle with a jig saw.

After all the holes were cut, I finished blending the edges- much better. The edges are softer now, and looks visually consistent. Now I'm ready to lay down a few coats of epoxy a few hours apart to really strengthen the veneer, and to seal the exposed wood from the cut-outs. I've remasked the area and brought the masking tape closer to the edge. I'll be laying epoxy on the mirror box surface close to the edge, so that the edge is sealed with 1/8" overlap to the mirror box surface. This is OK, and won't show in the final result.

The small 3/8" hole is for the 5.5mm x 2.1mm charging port that I'll use to charge the battery.

After a few hours of sanding down the epoxy using the 120-150-180 grit progression, the area is is wiped down with denatured alcohol to prep it for the first base coat of polyurethane, which is what Steve used for his top coats. I can already feel that the veneer is tremendously stronger with a epoxy coating on it. It just feels consistent with the rest of the mirror box, and feels like it is part of the mirror box to my fingertips. The epoxy makes a world of difference in how the fan panel looks and feels with respect to the mirror box.

The area is masked off and the first coat of polyurethane goes down. Most people would probably stop here, and call it good. I can't, because despite using the same finishing material as Steve did, one cannot overcome the ~5-6 year time gap, during which the top coats Steve put down have AND the veneer have aged. I will never be able to exactly match the aged veneer and top coats if I stopped here.

t took about 6 tries to get to the point where I was almost satisfied with the finish, using a variety of methods from brushing on the finish, wiping on the finish, and finally, spraying it on.

I'll start on the wiring and soldering in the switches + volt meter tomorrow after I try one more coat to get it matched up with the rest of the mirror box. I'll not post pictures of the wiring. Who wants to see pictures of solder joints? Will post a picture of the final completed assembly in a few days.

I wired up the switch panel, and this is is the pic where I tested everything to make sure everything looked OK to me. A few things first. 

1. The mirror box is upside down.

2. The bottom is the back side of the mirror box.

3. You can see the switch panel on the lower left of the picture.

4. I have dimmers as fan controls wired in, in addition to on/off switches because there's no dimmer that quite works for the switch panel because of the layout. 

5. The top is the front side of the mirror box.

 I have a pair of wires that run to the switch panel from the front side of the mirror box. That pair of wires connects to a pair of ~18" jumper wires via spade connectors at the front-side of the mirror box and those jumper wires run to the battery, so the mirror box can go up and down on the alt axis without wires snagging, and the mirror box can be removed, since the 12v battery sits on the rocker floor. You can see the wires coming from the top of the picture, which is the front side of the mirror box. This will become clearer in the next pictures.

I cut the depth dimmer casings in half because the case was way too deep at 1 1/2". I superglued the circuit board in place inside the case. In the pic below, I had the tailgate down to make sure I had enough slack for the back fans. Here, you can see the reasoning behind my choice of placement for the dimmers. When the scope is pointed at the sky, the dimmer closest to me is for the back fans (fans behind the mirror) and the dimmer further away from me is for the front fans (corner fans). This roughly corresponds to their actual physical placement in the mirror box.

Moving the tailgate up and down, I can see the wires are just fine and don't snag on anything.

One of the pictures show a view of the pair of wires that run to the battery- this is the mirror box front.

On another picture, You can see the connection to the battery from the mirror box in the below picture. I determined length by moving the scope all the way down on the alt axis, and cutting the wires to that length + 2 inches for slack.

I made a battery strap out of 1/16" thick aluminum sheet at 1 1/4" width and 18" long. I used the battery to help conform the alunumum to the battery by bending it around the corners. The next two pictures show the battery in the rocker.

One of the pictures below show what the dimmers look like in terms of accessibility. As the scope goes up in alt, the dimmer closest to me controls the back fans behind the mirror, and the dimmer further away from me controls the front corner fans.

I'm pretty much finished. This was a 1 1/2 month project for me, mostly because it took so much time and effort to match the veneer up with the rest of the mirror box.

A few things:

 1. The top on/off switch controls the front corner fans- a simple on/off switch.

2. The bottom on/off switch controls the back fans behind the mirror.

This roughly corresponds to their actual physical placement in the mirror box as seen from the top of the mirror box.

The 5.5mm x 2.1mm port is for charging, If I forget to charge the battery before a dark sky site trip, I can simply plug in the scope to my truck using my charger with a cigarette adatper wired in to charge the battery, or I can run it off a regular extension cord by plugging one of my 12v AC to DC charger to an extension cord.

Final comments, after testing: 

I tested the fan set up, and found that indeed, I do need the dimmers as a high frequency oscillating type of motion can be observed in the eyepiece with the dimmers set to max. So I experimented with different dimming settings, and found that having the back fans set to 1/2 and the front fans set to full worked the best.

The front corner fans being high above the mirror, cushioned with neoprene strips + lots of wood to absorb the vibrations, do not produce any kind of vibrations in the image, even set to full. This is verified by turning off the back fans, and observing with the front fans set to on and off with the dimmer on all the way.

I'm glad that I have simple on/off switches, as it allows me to keep the dimmers exactly where they're at, so I don't have to adjust them every time I use the scope, although I do plan to have both dimmers set to full during the cool-down phase.

But the problems I was having with the mirror still holding heat after several hours of cooling have all but disappeared. So, this project achieved the goal of quicker cool down time.

As for battery run time. The math was right, which is about 9 hours with the fans on at full speed. The battery was at 62% after 5 hours. This was verified with my Klein Tools multi meter (12.2 volts).

With the fans being turned down when observing, the battery should be good for 2 nights of observing on a single charge OR one full all nighter.