Builds & Reviews

By Rob Froyd

2025 09 03

Introduction: I was at the Silent Electric Flyers of San Diego model airplane field on Labor Day. I witnessed a crash of, I think, an aerobatic Extra 260. The pilot was very good at slow 3-D flying and crashed on his second flight near the runway. Sometime after the crash, I went over to his pit table to find out what had happened. He said that he lost radio control of his aircraft. I looked at his radio installation and saw a mounting orientation with the antennas that I had never seen before. We had a short discussion. He felt that his mounting method was fine. I decided to do some investigative research on the subject and share it with the club.

Research: I used Google to search for information about the 2.4 GHz, 2 antenna, diversity receiver installation methods. Here is what I found:

1) The actual antenna portion of the wire coming out of our receivers is just the tip, without the coaxial/plastic casing. That tip is normally ¼ of the wavelength of our 2.4 GHz transmission frequency. And here is that calculation (1/4 * c / f). c is the speed of light and is 300 E6 meters / second.

Antenna Tip Length = 1 /4 * (300.0 E6 meters /second 2.4 E9 Hz)

Antenna Tip Length = ¼ * 0.125 meters

Antenna Tip Length = 31.25 mm

2) Angle: Always route the active tips at a 90-degree angle to one another. This will ensure that at least one antenna” is close” to the optimal angel of the transmitter antenna. Note: The ideal orientation of one transmitter antenna and one receiver antenna is when they are parallel to one another, (example both pointing straight up from earth ground as one possible orientation). “A weaker orientation is when the antennas are perpendicular to one another. Very weak when they are pointed ends on, directly at each other” (John Salt, April 2025, Section RC Antenna Gain, Polarization, Diversity, & Direction).

3) Separation: I found two references for this. Google AI describes Minimum separation as ¼ wavelength and recommended separation as 1 to 3 wavelengths (12 to 37 cm). From John Salt, April 2025, Understanding RC Antenna Operation & Placement, https://www.rchelicopterfun.com/rc-antenna.html “Recommend distance of separation by most manufacturers is the full wavelength distance or more. So, with a 2.4 GHz radio system, having the RX antennas on board the aircraft separated by about 12cm or more is a good practice if possible.” Also, if a pilot follows the Futaba Receiver manual (Example, R7008SB), a diagram shows each antenna coming out of the case at 45 degrees to the case end, with the two antennas forming a 90-degree triangle. I measured the length of my Futaba receiver antenna, (case to start of theantenna tip), at 10 cm. If you orientate the two antennas according to the drawing in the manual, the hypotenuse is the (square root of 2) x 10 cm = 14.1 cm. This meets the recommended separation (antenna tips) of 1 to 3 wavelengths.

4) Clearance: Keep antennas free from contact, and away from carbon fiber, metal, batteries and motors.

5) Exposure: Ensure the active tip (31 mm) of each antenna is fully exposed and unobstructed.

What I saw in the Extra 260: Two antennas were running straight out of the back of the receiver, towards the tail of the aircraft. One antenna wire with tip was perfectly straight and held in place with some shrink tubing. The other antenna made a 90 degree turn just before the tip, but ran right next to the other antenna, also held in place with shrink tubing, The separation between the two tips were less than a quarter inch at the closest. I believe this is not meeting the minimum separation distance and is not at all optimal. There was a satellite antenna module, but I could not see it and didn’t know the  routing of this module’s antennas.

Examination of my own aircraft:

Extreme Flight 540T 48” Wing-Span: I routed the two antennas using a rotated V, running towards the back of the airframe. I was able to make the two antenna tips perpendicular to each other, one tip in the lower left of the fuselage, and one tip in the upper right of the fuselage. Separation of the tips is roughly 12 cm. I have some servo wires running to the back of the airframe, and the antenna tips are separated from the wires by about 2 inches.

E-flight Eratix 3D:

I routed this in a 90-degree triangle pattern with good separation. However, one of my antennas is running along a carbon fiber wing strut. This is not proper, I will need to fix this.

Research Links:

https://futabausa.com/wp-content/uploads/2018/09/R617FS.pdf

https://futabausa.com/wp-content/uploads/2018/09/R7008SB.pdf

https://www.rchelicopterfun.com/rc-antenna.html

The above is a prelude to Randy’s maiden voyage videos of his new Blackbird below.

By Steve Manganelli

One of (6) Teams of the 2024 Competition works on their model

Each Spring Quarter, University of California San Diego (UCSD), Mechanical and Aerospace Engineering Department (MAE), conducts their capstone aircraft design class (MAE-155B) for soon to graduate Mechanical and Aerospace Engineering students. Teams of 4 to 6 students are provided a proscribed electric R/C Model power system consisting of 3S1800 Lipos, an appropriate ESC and small outrunner motor. They are provided receivers, economical servos and transmitters that are reused year to year. The rest of the aircraft design/development is up to them!

The class ends in a competition to be held Friday, June 13^th at SEFSD’s Mission Bay Park Field. The competition will begin at 0800 and conclude before Noon. The field will be closed to sport flying during this time. This year, the models will carry a combination of bulky low density cargo that is to be deployed in flight and high density cargo that must remain in the aircraft. My worries about mid-air deployment were allayed by the fact that the low density cargo was an empty cardboard box, at most ½ the size of a shoe box. The competition scoring is based on dimensions of the box and weight of the carried payload.

Last year’s event took place on June 14^th and was quite an adventure for test pilots Dennis LaBerge, Glen Merrit and myself as none of the models had been flown prior to the competition. This turned out be fortuitous as most of the models were unflyable without some remedial work.  After last year, the 3^rd year of the Class/Competition I got tired of seeing the students trying to correct the same mistakes on the field that should have been corrected at the building  board. Excessive control throws, backward surface directions, poor servo geometry, crooked hinge lines, improper landing gear longitudinal placement, incorrect Center of Gravity, etc. plagued most of the models brought to the field. This past May 13^th I trekked to UCSD and did something about it : I prepared and gave a guest lecture to Dr. Hwang’s MAE-155B Class entitled “Pratfalls of R/C Model Design” showing typical mistakes we’ve seen at the field and how to get it right on the building board to generate a competition worthy aircraft for the contest.  Feel free to join Dr. Hwang, Lab Manager Paul Arcoleo and their (6) Teams of students and test pilots Jim Bonnardel, Dennis Laberge and myself as we tame the wild blue skies in the name of community service and higher education.

Steve Neu

Urs sent me this—the Swiss made a 66lb giant indoor model with a 8057motor on 12cells. The thing is huge but looks easy to fly—- Not sure how you transport it………

By Steve Manganelli

The annual Design-Build-Fly (DBF) Competition is just weeks away and SEFSD is helping San Diego State University (SDSU) get prepared. Myself as technical advisor and Safety Officer Steve Neu, Pilot will be at the upcoming International Competition in Tucson beginning April 10^th. The Competition pits the top 110 Aerospace Engineering undergraduate college student teams from literally around the world! Never mind March Madness, this is April madness!

The American Institute of Aeronautics and Astronautics (AIAA)  sanctions an annual competition called “Design-Build-Fly requiring student designed electric powered cargo carrying R/C model. The specific rules change every year so not only is there no continuity from graduating students, but each year’s new rules create new challenges. This year’s rule set pays homage to the full scale X-1 supersonic flight test program circa 1948. SDSU will not be building a B-29 to carry “Glamorous Glennis” to supersonic glory, but their own version of a launching aircraft to carry a small glider (less than 0.55 lbs, not to worry) and deploy it so it lands in a specific location to attain bonus points. The glider cannot have any R/C controls but may have GPS or other very modern means to guide it to the “bonus box”. For more info on DBF rules go here : AIAA Design/Build/Fly Competition | AIAA .

Team Aztec Aero’s prototype X-1 Launch Aircraft, the Ehecatl (Aztec God of wind) made it’s first flight on February 20^th, 2025 in capable hands of SEFSD Safety Officer Steve Neu. Prior to that, I took it through the wringer, setting control throws, proper center of gravity, security of installed equipment, etc. One of the required missions to carry simulated fuel (16 Oz water bottles) on wing pylons was accomplished on the day of the first flight without much drama as the students built a good flying model. The relative scoring depends on how much weight they carry and how fast they can fly on the 1000’ racetrack course. We will optimize our cargo weight and speed on subsequent test flights. The real excitement is X-1 deployment mission!

All attempted deployments of the X-1 made so far have been successful as long as you count “success” as the X-1 disengaging from the Ehecatl on command. Unlike the rocket powered full scale X-1 which matches thrust/speed with the B-29 before releasing, our unpowered X-1 glider appears to rocket backwards as it is released which makes sense. The release height is mandated as 200’ to 400’ so the little X-1 being deployed from the 6’ span, 10 lb Ehecatl looks more like a hatch cover falling off in flight and blowing downwind than a deployed air vehicle! To date, we’ve tried (illegal) radio control on the X-1 to get a handle on it and several configurations of X-1. To see more, come out and watch our final test flights scheduled for Sunday afternoons between now and the competition. In the picture L to R are Jackie Hernandez (Treasurer), Layla Spangle (Aerodynamics Lead), Jenna Schrady (Systems Lead and Chief Engineer), Bryan Ramirez (Manufacturing Lead), Ryan Kataoka, and Kevin Vu (Report Lead).

The students are named in the article. Seth has the clear glasses, David Yount the blue sun glasses and Nicholas no glasses and sometimes hat. In the picture “…Pre_Crash_all”, 2nd from right, is Paul Arcoleo, UCSD Engineering Lab Manager. Madison is only female pictured.

By Steve Manganelli

On February 17, 2025, a group of UCSD Aerospace Engineering students completed an important milestone toward an even more ambitious project: design and construct a Vertical Takeoff and Landing (VTOL) model aligning with the academic specialty of UCSD Professor John Hwang. The first I heard of it was via an E-mail from project lead and Senior Aerospace Engineering major Seth McLaughlin on January 5^th, 2025 : “Our practice-building  (non-VTOL) prototype was complete and could we schedule a test flight with you?”

I have seen enough student built aircraft to know better and volunteered to visit my alma mater UCSD to conduct a bench inspection of the aircraft prior to seeing it on the flying field. It’s a good thing I did as I sent the team consisting of Seth, Madison Purcell, David Yount and Nicholas Orndorff back to the drawing board with numerous modification recommendations all of which if not implemented would have caused the aircraft to be non-flight worthy. Among the usual excessive control throws, shaky hinge lines and dubious servo-control surface geometry, their 6’ X 12” chord foam wing lacked any kind of spar. It nearly folded by supporting it fully loaded by the wing tips which is equivalent to 2.5 Gs, a realistic turn being closer to 5 Gs. I also had them rearrange the batteries into more S and less P and a commensurate propeller to get closer to 100 watts in/lb.

My return site visit on February 10^th approved the modifications and set the date for the maiden voyage. We did a successful taxi test, got the requisite control throws (and expo) greatly improved all the control surface hinges and pronounced the run-up test good to go. The model was assembled at SEFSD field, a final Center of Gravity check and control wipe out test performed and placed on our newly manicured runway. The students were as nervous as kittens! The throttle was advanced and she smoothly lifted off after about a 50 takeoff roll : no drama at all. The kittens became very happy cats as I brought her around the pattern again and again…and a low camera pass. “Should I try a roll?” Wasn’t great but it did it. My students were ecstatic. Other than some non-obvious errors on control surface hinging and servo connection, the plane flew straight off the board; a tribute to their underlying design skills. I never even touched the trims! The model flew almost as well as my commercially fabricated sport models. I brought her around to a no-brainer landing at a very slow speed and the question arose : what next?

With the design/flight goal met there was discussion about what to do with the model which sort of belongs to the school…hmm. We started recharging for flight #2 and I asked : “anyone have any R/C modelling experience?” Seth mentioned he had flown a Radian and participated in some TPG event at Torrey Pines. Perfect, you’re going to fly it next time! No dissenting meows from the other cats. After another smooth takeoff and climb to altitude, I handed Seth the transmitter with the model heading West. Seth made a couple of circuits of the field; so far so good. On about the 4^th pass heading East I thought he was going to do another low glamour pass down the runway as I had done ; apparently not. After passing us standing at the fence, a final turn North did not arrest the descent with elevator and she plowed in pretty hard : oops! Well, now we know what to do with it. Seth and company were still happy with the outcome and now cleared to begin design and fabrication of the VTOL capable version. Watch here for news of it as it has to happen before the end of the School year (mid June) as they all graduate. I look forward to another opportunity to help San Diego’s next crop of Aerospace Engineers getting their feet wet at our Mission Bay Park Field and contributing to SEFSD’s important community service paradigm.

This video is a very nice attempt to accomplish solar flight.  In the article below that, in 2005, the “SoLong” accomplished it to set a record of 48 hrs. of continuous solar flight.

Alan Cocconi and a group of friends met up for a couple days in 2005 to do what had never been done: be the first to fly 48 hrs non-stop on solar power alone.

Continue reading →

Continue reading →

By: Stephen H. Nussbaum, SEFSD Member since 2010.

BACKGROUND:

Have you ever been caught by surprise when your model suddenly takes a dive and ends up in a heap in the middle of the runway? It’s happened to me and more than once. We probably experienced a stall due to the air flow over (and under) the wing being too slow to generate enough lift to keep the airplane flying. In all real, certified airplanes, the FAA mandates that there is a stall warning bell or buzzer that alerts the pilot when the plane is flying too close to the “stall speed”. When this alarm sounds, it’s time to take action by adding power and/or if you have enough altitude, drop the nose in order to regain the necessary air flow over the wing to generate the lift needed to maintain flight. Sometimes when the alarm sounds your wheels are just a few inches above the runway, ok land already.

In a real plane, the pilot can see his true airspeed on the airspeed indicator. He can get a good idea by monitoring this indicator that his aircraft is moving forward at a safe speed. That is, a speed that guarantees sufficient lift. RC pilots we don’t have that critical piece of information.

I set about to change that for my models and I wanted to share the results of my efforts with you guys. I have developed a stall warning system that will provide you with a true airspeed display and issues a warning tone when you’re flying too slow and are at risk of stalling. I refer to it as a “system” because it’s it’s made up of a few components although it’s not that complicated. My hardware design resides in the plane but to complete the task it also relies on the telemetry capabilities of the Spektrum radio product line. The telemetry capability is key here because this is how the measured airspeed gets transferred from the plane down to the controller for your observation. The controller also allows you to program the minimum speed threshold, unique to your model, that will be used to sound the alarm (or vibrate the controller) if the speed drops to that level. That’s how the stall warning is implemented.

This system features the new airspeed sensor and associated hardware. Along with the Spektrum telemetry and transmitter features, it provides the following benefits:

1.       True airspeed readout on the transmitter’s LCD display range is 0-35 mph.

2.       An optional voice announcement of the airspeed at 5 or 10 second intervals

3.       A selectable warning annunciation when the airspeed drops below the user programmed minimum speed threshold. The alarm can be a combination of a tone, vibration, or voice message

Putting this system together will require soldering skills. Jumper wires need to get soldered to a few through holes in a pcb. The sensor cable needs to be extended since you can’t buy one that is long enough to run from the sensor out on the wing into the fuselage center section where it terminates at the electronic module that reads it. Also, you’ll need to have basic modeling skills that include fishing the sensor cable though the wing and mounting the electronics. 

Continue reading →

The CAL FIRE OV-10 Bronco.

By Steve Belknap

Back in the early 2000s, our club (SEFSD) hosted a yearly event that we called the Mid-Winter Electrics.  It was a 2-day event that showcased the latest and greatest in electric powered RC planes.  There was open flying, demonstrations, etc.  We also had vendors that would come a long way to attend.  One of the regular vendors was K & A Models of Albuquerque, NM (no longer in business).  Ken Williams would showcase his expertly crafted kits.  I bought a few of them and recently completed one, the OV-10 Bronco.

It was a pleasure to build such a well made kit.  Everything fit perfectly.  The fiberglass work was second to none.  I made many modifications to mine mainly because I wanted more power, retractible landing gear and functioning rudders.  More details about these mods later.

I chose the CAL FIRE markings because I liked the look better than the typical camouflage you see on most military aircraft.  It turns out CAL FIRE has a whole fleet of these stationed all around California.  CAL FIRE uses the OV-10s as the primary command and control platform on wildland incidents.  I found there was one stationed at the Ramona airport so I modeled mine after that one.

Please see the video of the first flight.

The specs are:

Wingspan:  43.5″
Weight:  64oz
Power:  (2) Cobra C-2808-26
Prop:  (2) APC 8x6E & 8x6EP
Battery:  4S-3000 mAh Li-Po

The power system chosen makes about 600Watts.  This gives the plane 150W/lb.  During the first flight I was mostly using less than half throttle.  Performance was excellent.

Continue reading →

• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 2
• The Gallaudet Seaplane Project, Pt. 1

The Gallaudet’s First Flight.

The Gallaudet’s First Hop off the Water.  Click below for a video of the first time on water.

By Allan Flowers

ASSEMBLY:

With this model, all the major components are separated from each other so the struts and rigging become the heart of the assembly process. It was necessary to design and construct a large wooden fixture to accurately hold things in place during this time. Rigging is multistrand .031” stainless wire from McMasters-Carr and each element had to be made and fitted individually. Sullivan rigging connectors and clevises provide adjustment – with 75 pound fishing swivels to keep the wires from being twisted. Better and much cheaper than turnbuckles.

Continue reading →

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 2
• The Gallaudet Seaplane Project, Pt. 1

By Allan Flowers

WINGS:

The laser cut parts for ribs, etc. were the basis of the wing construction. This design has L-cut steel fittings at the strut & rigging locations. The main spars are 10mm carbon fiber tubes and there is a 3/4” wiring tube in each wing (thin wall aluminum on lowers, paper tubes on uppers).

The aileron servo housings were a special task and each one is wired with high capacity extensions and capacitors. I am using Hitec standard size servos (HS-645mg). Right hand wiring separate from left side to allow exponential throws. The wire leads eventually will be routed through junction boxes and into grooves on the insides of the cabane struts to the RX in the fuselage.

There is a triangular lifting frame on the upper wing, based on the Gallaudet D-1. Steel fittings for this were necessary in the top wing’s center area.

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 2
• The Gallaudet Seaplane Project, Pt. 1

By Allan Flowers

FLOATS:

The main float was built up starting from a basic plan view panel and covered with .001” Fliteskin sheeting.

Continue reading →

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 2
• The Gallaudet Seaplane Project, Pt. 1

by Allan Flowers

FUSELAGE DETAILS:

The cockpit shroud was formed from aluminum sheet over a wooden form, annealed and bullied into shape with a dowel. It’s not perfect (first attempt was a failure) but the cockpit combing will hide the worst of it .

Continue reading →

Steve Manganelli’s Seasonal Decorations

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 2
• The Gallaudet Seaplane Project, Pt. 1

by Allan Flowers

The REAR FUSELAGE:

Because of the unique power system, the rear fuselage must be supported on the central tube that the propeller hub rides on. A fiberglass tube is glued into the wooden structure to engage with the aluminum tube.

A narrow hatch gives access to the rudder and elevator servos and the linkages to two jackshafts that drive pull-pull cables to the control surfaces. It also provides a place for a bolt that prevents the rear fuselage from rotating on the tube.

Continue reading →

Maybe some of you have seen my smaller version of this plane flying at our field.  This one is really worth watching:

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 1

by Allan Flowers

Early CAD models, Etc.

There are multiblade propellers available in the size needed (e-Calc) but the hub would need drilled out for a nearly 2” diameter mechanical system. Therefore the propellers and hub would have to be hand fabricated. Not having the ability to NC mill the unit, it would have to be made largely of laser cut wood and aluminum sheet. The thing would have to hold together at up to 7000rpm without flying apart – so accurate balancing and mechanical strength were critical.

The early CAD designs were eventually married to the available components from McMasters-Car and B&B Manufacturing (maker of sprockets and belts).

The idea was to make and test the drive system before embarking on the rest of a two year’s long build.

Eventually an APC propeller was selected (22x10E) and two were purchased. These were fixed in a mold where resin collars could be cast around them. This element was cut off and finished. In the meantime, my laser cut metal and wood parts had arrived and the hub unit was assembled.

Using a crude wood test fixture, I determined the inter shaft distance between the sprocket centers. Later I was informed about a website calculator which verified my empirical test results to within .05mm.

As the hub was being created and balanced, it was necessary to design and build the forward fuselage portion, to complete the drive system. This would enable a test of the drive unit – a critical step to determine its feasibility. The system would have to produce sufficient thrust and not fly apart.

The hub unit needed to act as a fan to bring cooling air past the motor which, being located rather far back in the airplane, could be prone to overheating. The final part is designed as a centrifugal pump and should keep the motor fairly cool.

As the CAD design progressed, other components were being finalized for fabrication. One item was the nosecone which was a challenging part to make. Ultimately a 3D printed part was made by Thomas White, a prominent scale modeler on the East coast who has large scale 3D printing capability.

The fuselage was built around the aluminum tube upon which the propeller would run. The forward part was completed and the tube, motor and drive system installed for testing. I needed a “test sled” to hold everything and allow thrust measurements to be made.

The laser cutting included the floats and rear fuselage parts so I moved ahead with those things while finishing the front fuse. Used extensively throughout was a .01” resin composite sheet (brand name – Fliteskin). This is a waterproof, very strong sheet material assembled with expanding Gorilla Glue. It is light enough and nearly bulletproof. I tried to economize on the wood structure but the weights are still a bit more than desired.

One necessary study involved how to transport a finished RC airplane in my little car. After making a rough model of its interior, I could digitally maneuver the plane model into the “car”.

Allan

You are probably not like me. You can probably land one of these T-28’s without buggering up the nose gear.  I re-glued it a few times .  It was beyond re-gluing as the foam gets a bit soft after repeated beatings with terra firma.  The plastic insert was fractured in 2 places as well.

The red arrows show fracture stress points at sharp edges of the plastic molding.  Note also, the oil  covered belly.  These round engines ALL leak  😉

So I made a scarf plate out of .063″ 6061-T6 aluminum as I did not have any 2024-T3 around.  Hey, it’s what I had!  It’s pretty small so it does not weigh much.  Kind of a hack job but, it does the job of spreading the loads out to undamaged airframe foam.  Note the screw hole.  This helps couple the load from the plastic molding.

Scarf plate attached.  Note I cut away some foam on the starboard side to match the port side.  Note the screw.  I used a bead of silicone around the perimeter to spread the load from the flat aluminum to the uneven foam.

The back lighting made this picture difficult. Note that there is a gap between the nose strut and the aluminum scarf plate.  I’m sure this will be bumped into on landings and take the load off of the broken, glued, beat up plastic molding.  If you zoom in you can see the bead of silicon glue.

So, we’ll see how well this holds up and hopefully it won’t form any more stress concentration points. 

See you at the field,

Bob K

• The Gallaudet Seaplane Project, Pt. 7
• The Gallaudet Seaplane Project, Pt. 6
• The Gallaudet Seaplane Project, Pt. 5
• The Gallaudet Seaplane Project, Pt. 4
• The Gallaudet Seaplane Project, Pt. 3
• The Gallaudet Seaplane Project, Pt. 2

By Allan Flowers

This project started almost a year ago on a Google Image search when I discovered a very strange and interesting airplane. Having been thinking of starting a new project, I was intrigued by this odd challenge.

The Gallaudet was powered by a mid fuselage propeller driven by a ring gear – by no less than twin Duesenberg engines. The first version of this design, the D-1, actually flew in 1916 and was a proposal for the US Navy, which subsequently commissioned the Gallaudet Company (Connecticut) to build two more, the D-4s. One later crashed when the propeller failed, killing the test pilot. The other flew for several years, ending its life as a Schneider Cup racing plane. These were quite large planes, with wingspans of about 48 feet.

My first design was to be 1/6th scale at 96” WS. Along with the issue of the unusual drive mechanism, the ability of the single main float to provide sufficient buoyancy for a 20lb model was a concern. My CAD program has a mass properties function but it wouldn’t give me consistent answers so I solicited some help from fellow modelers on RCSB where I had started a “build thread”. Based on their calculations, combined with measurements of my Scion (which had to be used to transport this thing), I decided to consider a different scale. Around this time, a gentlemen who had seen the build thread, sent me some info from WW-1 Aero Magazine, which showed a drawing of a smaller Gallaudet proposal for a “hydro scout” (also from 2016). It had a 28 ft WS and larger a tail-fin and ailerons. This plane could be made in quarter scale with a larger float but smaller wingspan than the D-1.

The United States was soon involved in WW-1 and lost interest in the hydro scout programs. Thus the Scout was never made but the drawing had enough detail to interest me in a build.

The early CAD designs established the parameters of the drive mechanism and enabled a search for components, mostly from McMasters-Carr – which provides CAD models to download and pop into my system. The main parts were the roller bearing and sleeve which could be slid over an aluminum tube which would join the front and rear fuselage sections. Also important were some thrust bearings and seals to complete the drive.

Next was finding sprockets and belts to power the thing, and a suitable electic motor of small enough diameter to fit in under the main aluminum tube. That boiled down primarily to a few Hackers and Neumotors. The final choice was a Neumotor driving 13 and 44 tooth sprockets through a 15mm belt. Because of the gear ratio, a high KV motor was a necessity. E-calc was very helpful in researching the motors, ESCs and propellers. The later was a big challenge because there are no multiblade props that would work with the unusual hub design.

Great flying but lots of wind noise.  Turn the sound down but not off.  Some effects added.

Bob Kreutzer’s MQ-9, as documented in previous issues of the newsletter, is nearly ready to take flight.  I don’t think he has too much to fear from the Russians hence his confident attitude.

Here are a couple of the latest pics.

Continue reading →

A Forty Size (Test Bed) Standard Electric RC Airplane

By Carl Murphy

Introduction

This article begins where all the rest of the articles, tests of as specified by the manufacturer and flown only a few flights, ended.  Real world flying, where parts fail, break, wear out, fly off or don’t match the specifications.  Not shiny new hopes with failures censored out, and, what it costs, the net cost per hour of flight.  Follow along and try these easily available combinations for yourself.  And why I have been declared a bad example where ever I fly by Radio Control.

Before ever starting make sure the airframe is set up right, with components that last, then begin the tuning of the propulsion.  The setup of of the airframe follows.

By propulsion we are describing the whole package, motor, propeller carrier, propeller, motor-controller (to include any internal programming) and battery.  They have to match a specific RC airframe, location and flying style.  Ten motors were flown, seven direct drive outrunners, three geared inrunners, varying the input voltage from 3S LiPos through 5S and matching the propellers.  Several more motors, some defective, some obsolete, were rejected after bench tests.

Some combinations were later flown in more suitable airframes, see the parallel Fun Cub and the economic comparison of outrunners verses inrunners articles.

If you read a vast majority of magazines articles and their Internet equals, with the exception of competition machines, matching propulsion to the airframe is a neglected art.  You get an entirely false interpretation that the author chose, and demonstrated, the best, on the first try.  It becomes a form of censorship by omission not comparing equipment.  And the tests don’t go long enough to demonstrate stuff wearing out.  I haven’t even decided on the center of gravity or control surface throws at three flights, they are publishing everything is great at that much/little experience?  Which has led to the current acceptance that cheap equipment is just as good a real, no risking a quality/efficiency comparison.  Although many can set a motor-controller for braking the propeller to a stop when in-flight with the motor off, as for setting the motor-controller timing, it’s which-craft (zu Deutsch Wechseleri) to most.

Continue reading →

Bill Allen has been a club member since the 90s and loves delta wing jets.  He’s made the coolest jets from some of the most mundane materials.  His early jets were made from Dow Blue Foam and the recent jets are now made from $1 Foam Poster Board.  Below are some of his creations from the last 20+ years:

Blue Foam A4, 2004

How some of them were launched in 2001.  Piggy backed on my Sig Kadet Sr. (Big Red).

Late 90s Skyray delta pushers.

Continue reading →

This will be a brief description of my JR Models ARF Cessna Skymaster build.  Although the kit was made in the mid-90s, in the Czech Republic, I only built it in 2021.  I bought it from Fred Harris many years ago at one of our club swap meets, along with the JR Models Mosquito I built and wrote about previously.

I took no pictures during the build so I’ll supplement with pictures from the finished plane.

First, I present the highly detailed and thoroughly informative instructions.  Yup, that’s it, all you get.  Much creativity was needed putting this plane together.  Although the instructions were minimal, the fiberglass work and wing builds were exceptional.  The equipment placements shown are a mere suggestion which I mostly ignored.

The main fiberglass parts of the kit are shown on the drawing near the title box.  You can see a fuselage with stub wings and two tail booms with rudders.  The wings and horizontal stab are prebuilt out of balsa and covered.  A hardware package was included.  Formed windows and landing gear were also supplied.

Wingspan:  49″
Length:  36″
Weight w/LiPo:  3lb 11oz

Wings

This plane was designed to be powered by two Speed 400 brushed motors.  That would only give the plane about 100 Watts of total power.  I wanted to use more like 300-400 Watts of brushless motors.  The wings did not have any kind of spar, just ribs and balsa sheeting.  This required more substantial wing joiners than the short pieces of brass tube supplied.  I used much longer carbon tubes.  To get them further into the wing structure, I needed make holes in two more of the ribs.  I sawed teeth on the end of the carbon tube and used it like a hole saw to drill through the ribs.  Slow going but it worked.  The longer joiners also made it possible to have the wings removable.  Tape was wrapped around the carbon joiners in a couple places since they were too small for the holes in the fuselage.

The wing servos were a simple job to install.  Hinge tape was used to attach the ailerons.

Continue reading →