Ultra-Tote Field Box Modifications

In this write up we are going to take a brief departure from our J-3 Cub Build series and build the Hobbico Ultra-Tote Field box  – but with a few customizations!

The Hobbico Field Box has been around for a number of years and includes some great equipment that compliments anyone with a nitro RC plane.  When I purchased my first glow-fuel plane, I also purchased the Hobbico Ultra-Tote field box.  It includes a number of necessary items; an electric starter and a glow plug wrench to name a couple.  The kit also includes a nice 7Ah 12 volt lead acid battery for powering the included electric starter and wired glow driver.

However, I decided I wanted to make a few modifications along the way!  Once the basic box was built according to the manual I came up with a better way to secure a gallon of glow fuel in the caddy.  I started by adding a one inch high by 3/8 inch thick piece of basswood that serves to keep the fuel jug from being able to slide out of it’s intended location.  To hold this securely in place a simple zip tie was used to secure the handle of the jug near the top of the tote box.  Using a zip tie in this location, helps to “wedge” the fuel jug in place preventing it from slipping or sliding around during transport.

Next, I came up with my own design for a “power panel” of sorts.  I added an “always hot” charge plug so I could charge the lead acid battery without having to remove it from the field box.  I also added a couple of voltage meters, a current/amp display for the glow driver and a master switch that powers the entire panel.  There are two main 12 volt power sources, one of which is tied to the master switch but the one on the far left is always hot – directly tied to the battery which can be used for charging or as a power source for an external charger at the feild!

I also installed a current limiting device that allows me to adjust the amount of current (amps) the glow driver is allowed to use.  More amps equals a brighter glow.  I set my current to be a little brighter than a standard 1 cell NiMh glow driver is able to deliver.  I added a deans plug to the included wired glow driver so I could use this as needed and unplug it when I was done using it.  I also added a two foot extension to the glow driver cord for a little more length. To wire everything together, I used a power distribution board.  (Any distribution board suitable for a mini quad copter will suffice.)

I also opted to mount a 4 cell (yes that’s right – a 4 cell) lipo to the included Hobbico starter.  Going the “wireless” route here means you won’t have to worry about any power cords getting caught in the propeller.  The 4 cells gives a little more power and RPM for the starter to use.  The jury is still out on the long term effects of essentially overdriving the motor by a few volts. It usually just takes a blip or two of the switch before the motor is running.

Another modification I made along the way, was to add a screw to the carry handle, which will serve to hold the transmitter in a convenient location when starting the plane.  This allows me “hands free” access to the transmitter while starting the plane so I can run up the throttle trim during startup.

The ultra-tote also includes a nice electric pump in the kit.  I mounted this on the side of the Ultra-Tote and used a servo extension to wire it to the power panel.  If I ever need to replace the pump, I can just unplug it and wire up a new lead and plug it back into the power panel.

So far these modification have been working quite well and is making my plane fueling/starting procedures much more convenient!  Much of the fun with this hobby is making things work they way YOU want them to!  I’ve included a gallery of photos below.

Until next time, happy flying and RC’ing!

Sig J-3 1/4 Scale Cub Build Series – Part 7 – Nose Section Formers, Firewall & DLE 40 Twin Motor Mount

In part 7 we will be installing the nose formers and sheeting, the engine firewall and making a motor mount spacer for the DLE 40 twin cylinder gas engine.

Start by finding the nose formers from the die cut balsa supplied with the Sig kit.  Take measurements from the plans in order to properly place them on the nose section of the fuselage.  You will need formers F2, F3, and F4.

You will notice in the above photo I added some additional scrap pieces of balsa to help hold the formers in place as the glue dries.  In the photo below, I also added a 3/8 piece of basswood just behind former F2,  this will give the engine mount bolts a thicker piece of wood to bolt to.

Also add a block of wood behind the firewall under the nose area inside the cabin.

Glue together the two 1/8 inch thick die cut plywood firewall pieces together and allow to dry.  Make sure you use a enough glue so it squeezes out of the edges, we want a good tight bond here!   Wipe of any access as you add clamps around the edges.  Set aside and allow to dry overnight.

The DLE engine manual provides a drilling template that helps determine the placement of the DLE twin cylinder engine on the firewall.  Tape this in place on the firewall lining it up with the thrust lines you transferred from the plans.

Once the firewall is dry, you can now glue it to the main fuselage.  Test fit and sand as need for a nice easy-snug fit.  Once satisfied with the fit, use clamps and glue this in place.

Once the firewall has been installed, we will need to make a couple of spacer blocks for the DLE 40 twin engine to allow enough clearance for the mufflers.  Use the provided drill template to cut some spacer blocks and drill holes for the bolts you will be using large enough so they can slide through easily.  Now is a good time to drill the holes on the firewall and test fit the engine.  I ended up making two spacer blocks for just a little more clearance.

Once satisfied with the fitment of the engine, we can move on to sheeting the nose formers F2-F4.  The kit supplies some 1/8 thick balsa for this.  However, I found it easier to use two layers of 1/16 balsa.  Use wood glue in between the layers.  Use a number of rubber bands to hold the sheeting securely in place as it dries.

Once the sheeting is fully dry, trim the excess with a razor saw and sand smooth.

That’s it!

In part 8 we will be installing the rear formers!  Things are really starting to take shape!

Sig J-3 1/4 Scale Cub Build Series – Part 5 – Gluing Rear Fuselage Together

In part 5 we will look at gluing the rear parts of the fuselage together and completing the rest of the truss frame work.

Start with securing the top view portion of the plans to your work bench and cover with plastic.  Make sure it is as flat as possible.  Next, position the front of the fuselage over the plans matching up the positions of where the main formers are shown on the plans to where they are located in the fuselage.

Once the front of the fuselage is securely in position, you can begin to shape the tail end of each fuselage side as shown below.  To get a perfect angle while sanding, transfer the angle from the plans to each fuselage side.  I used a 2×4 sanding block that had been squared on all for sides and using a piece of wax paper, slowly sanded the angle to the line I had transferred from the plans.

Keep testing fitting the tail ends together as you sand to the line.  You may mind that one piece is slightly longer than the other.  The most important part of this process is that the tail ends of the fuselage are lined up as accurately as possible and match what is shown on the plans.

Glue the ends together using wood glue and small clamps.

Once the tail pieces are dry you can begin filling in the rest of the truss framework.  In the manual they recommend starting from the tail end and working forward toward the nose.  Since we installed gussets in part 4 of this series, we can simply cut and fit the 5/16 square stock pieces and slide them in place where the gussets are positioned.  I used thin CA to tack the pieces in place and then later brushed over the joints with wood glue. (One note, when cutting the bottom pieces that are placed into the gussets, cut a second piece at that time that’s exactly the same for use on the top portion of the fuselage side.)

For the top portion of the fuselage sides, the process is pretty much the same.    When gluing in the top portions of the square stock, I placed a construction square at each side of the fuselage at the glue point. This will help ensure that your fuselage remains square as you glue the pieces in place.!

You will also notice, I added in some additional 3/16 balsa filler in front of the 5/16 square balsa pieces.  This will be used for some additional bracing when we glue in the rear formers in the next step.  This won’t add very much weight but will help increase the gluing surface when installing the rear formers F8 – F13.

Once everything has been tacked in place with thin CA, brush over the joints with some wood glue and let dry overnight.

In Part 6 of this build series we will be installing the rear formers and top stringers!