The LZ-132 Black Eagle

An inexpensive, easy to make indoor R/C blimp. Complete construction article by David Lewis.

LZ-132 Black Eagle
R/C Semi-rigid

  • capacity: 7.5 cubic feet
  • length: 65 inches
  • weight: 7 oz ready to float
  • endurance: 120 minutes
  • # of channels: 3 (throttle and 2 axis vectored thrust)

 

PRE-KITTING

Note: Make the longerons and gimbal from 8 to 9 pound stock. Everything else can be 6 pound. Cut out the parts shown on the balsa patterns Fabricate two pulleys and three wheels from balsa. Build the ballast box from 1/16 balsa

Disassemble prop/gearbox. The plastic which is glued to the front and back of the motor to support the propshaft has excess material which should be cut away with a Dremel. Epoxy the motor lead to the plastic to prevent motor tab fatigue. Balance propeller in horizontal and vertical and reassemble

Set aside the following parts:
  • 4 pieces 1/8" square x 36" balsa (straight grain 8 to 9 lb)
  • 36 pieces 1/8" square x 32mm balsa (crosspieces)
  • 30 pieces 1/8" square x 42mm balsa (uprights)
  • 2 pieces 1/16" x 118" x 22mm balsa (gimbal front)
  • 2 pieces 1/16" x 8mm x 12mm balsa (motor yoke top and bottom)
  • 2 pieces 1/8" x 8mm x 133mm balsa (motor yoke sides)
  • a few strips of 1/16" square for the diagonals
  • 4 pieces 1/16" o.d. brass tube(l.5. 3, 6, and 10mm long)
  • 2 pieces 3/32" o.d. brass tube x 2.5mm long
  • 031" o.d. straight pins

David with his indoor blimp at the 1997 Toledo show. The blimp is fast, responsive, and a real crowd pleaser.


Full size plans can be ordered from the E Zone's plans service.

 

CONSTRUCTION

Build two sides on top of each other over the plans. Remove the sides from the plan and join together using the 32mm cross pieces to form the basic box. Don't put in the top and bottom diagonals yet (easier access). Glue the tailposts together and make a slot in the center. The elevator control cables will pass through this slot. Glue the 3/32 o.d. brass tubing into the gimbal sides. Glue the straight pins and balsa standoffs onto the the 1/16 x 1/8 gimbal front pieces and bind with thread to form the rudder shaft. Attach both gimbal front pieces to one gimbal side only.

Top pulley is rudder, side pulley is elevator. Sig 6" diameter rubber propellor drilled out and covered with condenser paper

A close-up of the gimbal. The prop and motor are allowed to swivel 180 degrees in both axes. It looks confusing at first, but the plans make it easy.

Dry fit the yoke around the motor using the 8mm wide strips of 1/16 and 1/8 balsa . Drill a hole in each yoke side to receive the 1/16 o.d. tubing (6 and 10mm long) and cement them securely in place. The motor is a press fit inside the yoke. Glue the yoke together in situ. Shave down the 1/8 side faces of the yoke to give clearance in the gimbal and glue on the other gimbal side, trapping the yoke in place. Make sure the yoke/motor/gear/prop assembly swivels freely up and down through a 180 degree arc. Epoxy the elevator pulley onto the 1/16 x 10mm brass tube (CA could wick into the bearing). Glue a piece of scrap balsa between the elevator pulley and the motor yoke. Install the M-shaped fairlead on the side of the gimbal and two straight ones on the tailpost.

Slip the 1.5mm long tubing over the top rudder shaft and the 3mm long tubing over the bottom rudder shaft, epoxy the tubing to the tailpost and wrap with thread. At this point verify that the gimbal swings left and right through 180 degrees very freely. If not, check to make sure that the rudder shafts are collinear. Glue a piece of scrap balsa between the rudder pulley and the gimbal.

Make sure your servos are centered. Glue the balsa bellcranks to the servo wheels and install both servos. The servo mounting ears are clamped between two 1/8 square crosspieces. Do not remove the rubber grommets from Cannon servos (they maintain case alignment). Then these crosspieces are glued to the uprights. Remove the heat shrink tubing from the speed control. Install the receiver and the speed control. These two items just rest on a crosspiece with a piece of Scotch tape applied to the bottom. Additional weight can be saved by removing the receiver from its case and hardwiring servos to receiver. Install the switches and flex leads to the motor. Center the trims on your transmitter. Do not install the battery yet but temporarily hook it up off to the side and center the servos. Rig the control cables and check operation. Add remaining diagonals, pilot figure and thread loops.

1/24 scale plastic car driver (Fujimi 11003) hollowed out with a Dremel. Control stick is the receiver antenna. Baggage compartment behind pilot holds Radio Shack cordless phone Nicd (23-173).

 

ADJUSTMENTS AND RIGGING

Build the left and right main gear subassemblies fiat over Section B-B. Glue the wheels to the gear struts. Attach the landing gear to the gondola and add the jury struts. Relax and admire your ship up on her gear for the first time. Switch on the radio and crack the throttle to low idle. When you pull back on the right stick, the motor should point down to lift the blimp (opposite of HTA elevator). Observe free movement and no interference with full stick throw in all directions. Patiently adjust as necessary. Glue a short length of thread from the flex leads to the top longeron to prevent slack from falling into propeller arc. Spray some silicone lubricant into spray can cap and use a pin or toothpick to wet the portion of control cable which passes over the fairleads. Also dab some on the gear shaft bearings.

Perform final installation of battery. The battery must be well secured to the airframe so that in case of collision it does not fall out and create a hazard to persons/property. Find and mark the center of gravity. Glue label with name, address and phone to bottom face of gondola. You may wish to weigh the completed gondola now and make a note of it. It will be in the neighborhood of 95 grams (3.35 oz) without battery.

 

ENVELOPE CONSTRUCTION

For maximum performance fabricate envelope from half mil aluminized mylar. One mil will hold helium better but imposes a weight penalty. 1.5 mil party balloon material is the heaviest but will minimize helium consumption. Mylar should be handled gently to prevent wrinkling, crinkling or creasing. Mylar bonds to itself when it is ironed. Do not use hot melt tape -- it doesn't make the seam any stronger

Cut two pieces of mylar oversize and lay them one on top of the other, plastic side facing in (aluminum side facing out). The plastic side is slightly dull. If you are not sure, trial stick some scraps together to see which way they stick the best. Cover your dining table with a cloth (the cloth texture will emboss the seam). Set your MonoKote iron on 3.75. Place the mylar pieces on the table and lay the template on top of them making sure both layers of mylar extend out to the trim line all the way around. Now quickly run the iron around the perimeter staying outside the trim line. This tacks the three layers together. Use scissors to cut out the parts. Smooth everything out and double check alignment. You may now want to use Scotch tape at three or four points to keep everything lined up. Mark the center of volume station on the mylar with a felt tip pen.

Firmly press the iron flat on the mylar about 1/4" in from the edge and slide it out away from the seam. This takes about one or two seconds. The embossing will show where the bond has occurred so you don't miss a spot. Lift the iron, move it along, allow a slight overlap and repeat. Do the entire circumference except for about 3/4" at the tail. Put a wide strip of tape on both sides here. This area around the opening is where the bag gets handled during inflation. The helium jet during inflation will cause wear and tear without a reinforcing doubler in this area. Keep this tape flat and smooth as you apply it. Use little squares of mylar packing tape to stick the thread shrouds to the envelope. Locate the shrouds so that the center of volume lines up with the gondola CG. Very important: Leave some thread sticking out past the top of the tape, loop it around and tie it. You may wish to weigh the envelope at this time and make a note of it (should be around 55 grams or 1.94 oz).

 

FLYING

Connect the shrouds to the thread loops on the gondola. Load some ballast into the box and slide it into the gondola at the CG. Open the primary valve on the helium tank. Stick the helium nozzle into the tail and secure it with strips of tape on the outside to seal the connection and prevent air entrainment. Hold the envelope up and bend the fill nozzle to the side to let the gas in slowly. Minimize flutter where the helium enters the bag. A bag should never be filled near 100% capacity because slight pressure will tear the seams. Allow a little margin for subsequent changes in temperature and barometric pressure. As soon as the ship comes off it's wheels, stop filling. Close primary valve and then bend the nozzle to the side to release remaining pressure. Pull out the nozzle and seal the opening with Scotch tape. Add or remove ballast to achieve neutral buoyancy and turn on the transmitter. Switch on the receiver and then the arming switch and check the controls. Take off and make a few circuits of the room to get warmed up and then bring her in to fine-tune the buoyancy until the helium reaches room temperature Place a wood or tape cover over the ballast box and slide it back and forth until the ship hangs level. Strap down the ballast box and make sure the cover will prevent ballast from spilling in the event of a mishap. Remove the battery whenever you transport the gondola. This will put less stress on the landing gear.

The Black Eagle leaves the dining room/airport for a training mission.

David Lewis
dlewis(at)usginteriors.com
4027 Rocky River 26
Cleveland, OH 44135
(216) 251- 2517
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Mar 01, 2012, 08:46 PM
Registered User
Charlie ricker's Avatar
Sweet plans!
Mar 02, 2012, 09:17 PM
Potential Future Has-Been
LZ-132 would have been a Hindenburg sized zeppelin. This looks more like one of the Alberto Santos Dumont type semi-rigids that predated the zeppelins.
Mar 06, 2012, 06:10 PM
Registered User
Charlie ricker's Avatar
I loosely based my home build off this, my gondola is 21 inches long and 2x2 inches square.
Sep 26, 2016, 05:52 PM
Registered User
Does any one know where to obtain these plans still? The weblink just leads to a 404 error and I believe this would be a good project to get my feet wet into LTA craft building. Thanks.
Sep 27, 2016, 10:21 AM
Go small or go home
ruzam's Avatar
That design is nearly 20 years old now. I don't know if it would make sense to build it as described with today's parts.

For example the pully system would more simply be replaced with directly connected micro servos (one servo mounted on to the arm of the other servo), and the heavy ni-cad replaced with a lighter lipo. Lighter receiver, etc, etc. The gondola pictured there is listed as 95 grams (without battery!!). That's pretty heavy for a simple balsa stick truss. In my opinion anyway.

The envelope design is a simple two side pancake pattern. You should be able to mock that up from scratch with the given the dimensions. You know roughly how big it should be and the final deflated weight (55 grams) should be about the same. This is one area of the design which really hasn't changed over time. Once you have your envelope constructed you're set for all your future LTA designing.
Sep 28, 2016, 09:18 AM
Go small or go home
ruzam's Avatar
Quote:
Cover your dining table with a cloth (the cloth texture will emboss the seam).
Now that's an interesting tidbit. I've been having trouble of late with seams that aren't fully bonded. My iron has an automatic shut off and I don't always notice that it's cooled down until after I've run it along a seam. Sometimes I think I run the iron too quickly on others. It's still warm enough to smooth out the seam, partially bond it and 'look' bonded. That is until I pressure test and a section of the seam lets go resulting in a messy post build repair.

A textured embossing might be the trick ensuring a good bond the first time.
Mar 31, 2019, 09:06 AM
Registered User

The LZ-132 Black Eagle successor


The Black Eagle design was based on the blimp kit sold by John and Carol Piri. I loved the kit but the swivel of the motor wasn't enough to satisfy me.

I'm designing a new blimp right now using a latex balloon for the envelope to reduce size and weight. Here is a comparison table of mylar versus latex:

MYLAR
lift (g) -- volume (dm3)
2 --------- 14
32 ------- 71
66 ------ 125

LATEX
lift (g) -- volume (dm3)
6 --------- 7
10 ------ 15
51 ------ 56
Last edited by David Lewis; Mar 31, 2019 at 09:10 AM. Reason: data table formatting
Mar 31, 2019, 04:04 PM
Go small or go home
ruzam's Avatar
How did you arrive at your numbers? I've never weighed latex with consideration for use in a blimp, but since I'm always on the edge of my payload limit, those numbers are significant.

I would never use latex without a coating (like hi-float) to contain helium leakage. The extra coating will add more weight to the latex. Is there still a clear benefit after that?

I have a number of designs I want to try that would require internal buoyancy envelopes wrapped in a skin to get the shape and form I'm after. Maybe latex innards might by the ticket.


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