Builds & Reviews

191 posts

The Gallaudet Seaplane Project, Pt. 3

by Allan Flowers


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.

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The Gallaudet Seaplane Project, Pt. 2

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”.


T-28 Front Landing Gear Repair Buletin 05-12-2023

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. 1

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.

Jovi’s DC-3 Build Project: Chapter 3, Building the Wing

By Jovi Murek

Hello again, well I’m back at it and building up the DC-3 Wing for this chapter. In this step, we will build up the center section of the wing. This aircraft was designed for nitro engines and, as you know, I am going to convert to electric.

Building the center section required a few modifications needed to be done first. W3 rips required cut out for the retracts, Firewalls got completed with the blind nuts installed. Other changes were needed, but just not now. So, I laid out the Center Spar and glued on the Ply Center Spar together once it cured. Next was to test fit the four plywood ribs and fit it to the building plans. From here I fitted the remaining ribs and fitted the wing mount block and the blocks for the retracts. Next was to fit the TE, (Trailing Edge). In the next few photos, you can see how it was all done.


Now that it all fit correctly and was flat on the building board, I was ready to glue, however, now that I see how it fits, I took it all apart and was ready to modify the main spar to except the retracts. Close to the outer ends of the main spar, I had to remove a section of the spar on both sides. This allowed the mechanics of the retracts to fit. The Top and Bottom spruce spar would be the strength to hold the cut-out section of the main spar. Alone with two strips of 1/16 plywood attached to the spar over the area of the modification to the spar.

DC-3 Fact:
The DC-3 was not only larger than the DC-2, but also much easier and safer to fly. An automatic pilot was installed as standard equipment. The overall design of the DC-3 was so successful that its basic specifications were never changed. Once the first DC-3’s entered service, the speed at which the entire industry converted over was limited only by the rate at which Douglas could produce them.

It was time to put it all back together and test fit all the pieces to make up the center section of the wing. Once I looked it over, and everything was just perfect, I started to glue the parts together with CA glue. Let it sit for a while, (just to make sure) I then added the TE and added some rails to the wing. I also added the dowel pins in place, motor mounts for the retracts. Ok, center section was coming together, as shown:

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A Multiplex Mentor Testbed for Year 2020

A Forty Size (Test Bed) Standard Electric RC Airplane

By Carl Murphy


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.

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Bill’s Deltas

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.

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JR Models Cessna Skymaster Build

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.

The entire instructions.

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


Wing Joiners: Original brass tube replaced by a longer carbon tube.

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.

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Brian’s Huge Amazing 95″ Spitfire

The wait for my dream Spitfire is over.

After having and flying my 80” Phoenix Model P47 for a few months (my biggest warbird at the time), in May 2021, I decided to try something bigger, I ordered a 1:4.75 scale Spitfire (95”). It is also Phoenix Model and distributed by Tower Hobby. Unfortunately, it was on back order and estimated to be shipped in a couple of months. But they have been changing the shipping status month after month, and it is still on back order now.

While waiting for the Spitty to come, I spent time to collect all the electronics and power components for it. I also bought an 80” Black Horse Spitfire from MotionRC (it is still in boxes, a backup plan if I don’t ever get the 1:4.75 scale one).

Then, in mid-September this year, as I almost gave up waiting for the 95” Spitty, and was about to start on the Black Horse. I found on RCGroups, someone in Riverside who had 5 flights on a 95” Spitty ready to fly for sale. I was so excited and, after exchanging texts and messages, the wait is over! I went to Temecula and brought my dream Spitty home.

The plane was equipped with all Hitec HS-645MGs which are analog servos. I changed them to digital D-645MWs except for the rudder, I used JX PDI-6221MG for more torque and less expense.

I also custom made 9 pins quick connectors for the wings and fuselage (picture below).

Here are the specification and setup of the Spitty:

Length:                86” (2184mm)

Wingspan:            95” (2413 mm)

Motor :                 Rimfire 65cc

ESC:                    Castle Phoenix Edge HV160A

Propeller:             Xoar 23x14x2

Spinner:               Falcon 6”

(I will change them to Biela 24x10x3 and also Falcon 6” spinner for more scale)

Battery:                 2x 6S 5000MAh 55C in series (12S)

                             2x 2S 2200MAh LiFE for receiver

                             1x 2S 1000MAh for retracts

Servo:                    6x Hitec D-645MW (2 Aileron, 2 Elevator, 2 Flap) and 1x JX PDI-6221MG for Rudder.

Radio:                    Tx: FrSky X10S Express (2.4GHz) + R9M 2019 ACCESS module (900MHz)

                             RX: Archer SR10 Pro (2.4GHz) + R9 Stab OTA (900MHz) in redundancy

(In case the main RX browns out, the long range R9 will take over)

I went over and double checked everything.  Then came the exciting and also scary Sunday! The maiden day!!!         

Compared to the weight and location of the batteries (8000MAh) from the previous owner, I use much lighter batteries, but it was still nose heavy (picture below, thanks to Fredrick and Brad!). I decided to maiden it with nose heavy since the weight of the nose was reduced quite significant compared to the original setup from the first owner.

Thanks to Fredrick Lorenz for helping as a wingman in my maiden flight, and also so sorry to folks down the runway, as the Spitty created a big cloud of dust when I tested the power before takeoff.

When the plane lifted off the ground, as expected, up elevator trim was needed, also right aileron. After less than a couple laps of adjusting, it flew straight. Although, I had too much throw for elevator and ailerons so I had to adjust my thumbs movement during the maiden flight.

After the maiden flight, I moved the batteries further back and achieved the CG marked by manufacture, and reduced the throws. The Spitty seems to be happy with that. It almost flies inverted without down elevator.

Thanks to Lewis Dotson for perfectly captured both of my flight videos! Links of videos below.

Also pictures from Tom Gluggio, Pete Kwei and help from other friends!

Happy flying!
Brian Zhuang

Maiden flight:

Flight #6:    

Spitfire landing:

P47 landing:

Mark’s Big Beautiful Jet

The plane is from HSD Jets, and runs on four 90mm fans.  I fly with 4 batteries of 6S x 5000mah. The length is 118 inches, and scale is 1:23.  For comparison, attached is a photo of me standing next to the fuselage.
This plane is easy to control in the air, but difficult on the ground.  The nosewheel has very little steering authority, and there are brakes on only two of the 18 wheels.  So that’s pretty close to not having brakes.  I first flew it up at Hemet, and even there I over-ran the end of the runway.
Then I took it up to the “Best in the West” jet rally.  This takes place on a 3300ft runway, so I was able to complete many flights with no problems.  It was super popular there, even though it is not particularly large or expensive by BITW standards.   The first BITW flight was captured in this video:
I ended up winning two trophies at BITW, “Best EDF” and “Best Civilian Jet” (photo attached).  I would like to bring it to SEFSD sometime, but I think it requires some modification to do that.  Thrust reversing on two nacelles would do the trick, but I’m not sure I will get around to it any time soon.
Mostly I just flew docile flights, although after a few I got a little braver and did several banked passes (45-degree-ish partial knife-edge) along the flight line.  And on the final flight, I managed to sneak in a barrel roll.  
Thanks to Bob Stinson for helping me schlep it up to Hemet for the first flight, thanks to Victor Shamulus for the video, and thanks to Andy Davis at HSDJETSUSA who fedex’d a replacement servo to me the week of the event, which enabled me to fly it at Best in the West.

Otto Steals the Show with his RC Loon!

Flyguy Promotions received a contract from Wide Angle Group in early June to produce a 10 foot flying Loon based on the Minnesota United Loon logo. The Loon was flown as part of the Major League Soccer (MLS) pregame covered by ESPN. Mike Frandsen, Bob Simon, Dave Encinas and Otto Dieffenbach built the Loon in 5 weeks with first flight on July 10. Emily DeJoode, Manager of Ampdraw Hobbies in Encinitas joined Otto as his far corner spotter for the performance. Three rehearsals and the performance flights were flown on August 8, 9 and 10. FAA and FBI approvals were obtained prior to flight operations.

The performance and project were considered great successes by ESPN, MLS and Minnesota United. 

Jovi’s DC-3 Build Project: Chapter 3, Building the Lower Section of the Fuselage

Now that I have completed the top section it is time to move to building up the lower section of the fuselage.  In this process we will also be making a change to the build.  That is moving the servos back to the original position (behind F5 to F7) which was just over the wing, where I had made the hatch for the access to the battery.  You can see that in the drawing.

Ok, let’s get started in building the bottom section.  The first thing I did was to install the formers into place, making sure all were 90 degrees from the top stringers which were pinned down to the board when building the top section. The wing saddles were also installed at this time too.

At the same time, I installed the push rods guide tube into place.  I installed the servos and worked on the push rods to the correct length.  Once that was completed, I placed the tail wheel support plate in place for a dry fit and made sure that I did have the correct length. As always it was perfect. 

To make sure that it was correct, I connected the servos to my receiver and made sure the control arms were center.  I then completed the rudder and glued in the rudder block to the control rod and again made sure that all was center so I would not have to do it at a later time.   The elevator was done the same way, but I have not glued it yet into position.  If adjustments need to be made, I can do that on the radio.

DC-3 Fact:

The one and only DC-1 served a full career with TWA, then was sold to Howard Hughes.  Hughes sold the airplane to the Spanish government, but the DC-1 met its demise after an engine failure during takeoff in the 1940.   (Guess they didn’t read the “Engine Out” section in the manual)

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Jovi’s DC-3 Build Project: Chapter 2, Building the Top Section

Framing the fuselage Top:  Fun part about building Top Flite kits is that you build right off the drawings. Got wax paper, laid it down and I grabbed all the formers including grooved main stringers.  These two stringers I soaked them in water to create the fit of the curve for the nose of the aircraft.  Pinned it to the board and let it sit.  I also installed the cabin crutch to help form the main stringers.  Once that was done, I then completed pinning down the stringers to fit the drawing.   Next was to place the formers into place just to fit, but not yet glued in place.  Here is where I had to create a hatch for the battery, instead of taking the wings off like I have to do with my Cessna. I replaced two formers.  The formers that come with the kit are 1/8” So I will be replacing them with a ¼ “thick.  These two formers will be used for the opening of the hatch.  The formers that came with the kit are going to be used for the hatch as you will see in this process.

DC-3 Fact:

Without a modern passenger plane.  TWA was not about to let United Air Lines corner the entire market with Boeing’s 247.  TWA initiated a program of their own to develop a modern airliner.  Douglas responded with the most advanced and the most controversial design, namely DC-1.  TWA ordered one unit and in 1933 the first DC-1 rolled off the assembly line in Santa Monica, California.  The DC-1 was bigger and sleeker than any other liner in the industry, including Boeings Model 247!

As you can see in the above photo how the formers were fitted into position.  Starting with the nose of the aircraft is where I started to glue the formers in position.  For the hatch section as I mentioned I am changing the formers with ¼ “thick.  I then cut the two original formers and glued the lower section to the replacement ¼ “formers.  The top half will make up the hatch.  In between the two ¼” formers I cut the middle former to match the hatch and the bottom part, I cut out the middle and only used the sides, also show in the photo.

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Jovi’s DC-3 Build Project, Chapter 1: Stabilizer, Fin and Rudder

By Jovi Murek

Hello Club members, Here I am getting ready to start to build the DC-3.  Starting off with the tail section of the aircraft.  The first part was to make the skins.  Here I took two sheets of 1/16 x 3 x 30 and glued the two sheets to together so the outcome would be 1/16 x 6 x 30.  I created three sheets, two for the stab and one for the fin and rudder.  Now starts the fun part, building!   Now that we have gotten the skins ready, I’m starting to build the Stabilizer.  As show in the picture I have all the parts laid out on the building board and preassembled them before gluing them into position.

DC-3 Fact:

After presiding over various projects including the Matin MB-2 bomber at the Glenn L. Martin aircraft company, Donald W. Douglas Jr, born April 6, 1892, co-founder the Davis-Douglas Aircraft Company in the spring of 1920 with help from David Davis, a millionaire with a great desire to fly.  By the mid 20’s Douglas designs were well known throughout both the civilian and military aircraft industry.

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RC Kites

By Rob Jahnke,
“I have another RC kite I was planning to bring this year. I call it the RC Eagle which is the Revolution Eagle kite created by Joe Hadzicki of Revolution Kites. It has an 8ft wingspan and is powered with a 3S 1500mah Lipo but packs up into a kite bag. You can see the first test flight here:
For the Revolution Eagle kite story check it out here:
The details of the RC Eagle Build are shown in this photo album. 
I make good use of the 3D printer for this project. I am happy to share the stl files.

Scaling and Comparing Performances of Aircraft Models (2D/3D Wing Loading)

[This article was borrowed from the April issue of the Ampeer.  Thanks to their Editor: Ken Myers]

By Andrej Marinsek

1. Introduction

Many years ago (Model Airplane News, Dec. 1997) an article was published in this magazine titled “3D Wing Loadings” (Three dimensional wing loadings) by Larry Renger; it was recently published again on the internet in a slightly cleaned up version. Its different approach to a specific modeling subject is interesting but, as it will be shown later, has some problems. The concept of the 3DWL, though correct in one respect, has otherwise rather limited reach and leads to some vague interpretations and questionable conclusions. The 3DWL persists around in different forms and publications and seems to be, nowadays, the most advertised and supposedly even the only appropriate approach for estimation and comparison of some model performances. This is somehow surprising, so it needs to be addressed in some way.

2. General remarks

Coherent units from the International System of Units (SI) are used in calculations as they are clearer. In most cases only one unit is attributed to a certain physical property and numerical transformations are simpler or not needed at all.

Instead of the term weight (W), which is strictly speaking, a kind of force, the expression mass is used (designated by the letter m), which is the proper name for the physical property measured in kg (lb., oz., etc), and is employed in all calculations here.

3. Agility of models

The motion of models in the air can be on one side described by the words like “agile” or “hot” or “docile” or “flyable” or whatever expression is used to appreciate the performance of models in flight. However this can be pretty undetermined and subjective.

On the other hand, some objective (given by numbers) performance parameters exist. With regard to the lateral axis of models, some performances directly depend on the lift force. These are the minimal speed in horizontal flight vm (stall speed), the minimal absolute turning (or circling) radius Rm and the minimal relative turning radius (RTm), which will be defined and discussed a bit later.

Also, some settings (such as the center of gravity) and a number of model properties, for instance wing profile, low/high wing, aspect ratio, tail (distance from the wing, area, position), the size of rudders, propulsion, thrust vectoring, etc. considerably affect certain performance parameters.

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Servo Twitching in Large RC Planes

By Mark Davis

I recently had a problem with a servo randomly twitching, and was able to solve it, so wanted to share what I learned.  It is a large plane and there are 10 feet of wire between the Rx (Spectrum 12310T) and the servo (Hitec 7950TH “ultra torque”).   Because of this, I ran 17 gauge power/ground, and used MR30 connectors (instead of 20gauge heavy duty extensions with normal servo connectors).   But even with this, the servo exhibited erroneous twitches, especially when moving.


I found the problem could be remedied by placing (near the servo) a capacitor across power & ground, or a signal booster, or both.  This problem depends on the servo also, and for example the D625MW did not exhibit the same issue, and needed no remedy.  It appears that this is because Hitec 7950TH (“ultra torque”) draws high current for brief snippets of time, and thus causes large power transients.  These will appear also on the ground, and therefore the PWM signal can be affected.    A power bypass cap by itself fixed the problem.   A signal booster by itself was helpful but not entirely reliable (Spektrum and Hitec both make them).  I believe the best solution is to use both a supply capacitor and a signal booster, based on the oscilloscope plots below.  


First, some background information and definition.  

When ground currents are present, we have to designate a specific point as “0 volts”.  In text below I treat the ground at the receiver as the definition of 0v.  The oscilloscope probe was connected with its ground near the servo, 10ft away.  So it is not necessarily at 0v, by this definition.

The oscilloscope horizontal scale (time / division) appears in the upper left of the screen next to the letter “H”.  The vertical scale for each channel (volts/division) is shown in the lower left of the screen.

When a servo was connected, it was connected without load or with light load (sitting upright on a table, or in some cases on its side, so the arm was just lifting the weight of the servo).

The capacitors I had on hand were 8200uF 10v, and 4700uF 16v.  Since my system runs on 2S LiPo, this is sufficient voltage.

The signal boosters I tried were:

  • Spektrum Signal Line Voltage Booster SCMCP
  • Hitec Signal booster HRC58496

I have grouped scope traces into 5 sections:

Section Servo Capacitor Across power/ground Signal Booster included
1 7950TH No No
2 7950TH Yes No
3 7950TH No Yes
4 7950TH Yes Yes
5 D625MW No No

First see picture 1B below.   I put a scope on the signal wire.  You can see the servo is approximately centered here, with a 1.5ms positive PWM pulse.  But you can also see frequent artifacts.  I didn’t immediately notice a very regular period, but they seemed to occur every 4-10ms.   Unfortunately I didn’t capture the power line here, but from later plots I believe it would show exactly the same artifact at double the magnitude (I’ll explain why later).   

Now consider the structure of one such glitch.   It appears the servo decides to draw a large amount of current for about 50us – 200us, depending on which glitch we are looking at. This pulls down the power line voltage, and pulls up the probe ground (servo ground).    The signal is looking into a high-impedance FET, and so draws insignificant current, and so should have insignificant voltage drop even over 10ft of wire.   This explains why we see the oscilloscope voltage go negative at the start of the glitch; the signal wire remains at 0v but the probe ground “bounces” up due to the current being dumped into it.   The voltage appears to be asymptotically approaching a steady state value (with the expected exponential shape) by the end of the 200us.   This steady state should be the current of the servo times the wire path resistance.  Then when the current draw stops, the inductance of the wire keeps pushing current for a small transient.   Thus, the opposite effect will occur;  The voltage of the local ground will dip below 0v and so the signal wire sitting at 0v appears to go positive on the oscilloscope.  Note that this positive glitch can be quite high.  This plot has 1v/division, so the first glitch captured here is around 1.6v, which I’m guessing is quite close to the detection threshold for a PWM pulse.

Picture 1B:  No capacitor, no booster

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Bill’s New Jet

My latest purchase is this Xfly T7A from Bitco Hobbies or Banana. I got a pre-purchase deal for $150 on a recommendation from Chris Wolf’s youtube channel. I love this thing ….65mm edf, fixed gear and 4s 2200 lipo.  Nicest flying jet I own. Fast very nice finish and sounds great.  I highly recommend it. Bill A.

My First and Only Out-Of-Sight Flight

By Steve Manganelli

The term OOS or “Out Of Sight” is a Free Flight Model Aviation term referring to a model catching a thermal that carries it up and out of sight, generally never to be seen again.  I can’t imagine the melancholy feeling of watching the product of your hard work disappear before your eyes. On one hand, you have validation of your model building skills; on the other, sadness at the loss  of your creation. I’ve heard stories of models turning up in a cornfield some miles downwind of the field years later or what not, but that is nothing like my OOS experience!

For my story, turn the clock back to about 1971/2, before I could afford the luxury of Radio Control. As a geeky 11/12 year old, with friends of similar ilk, if it flew, floated or ran, we had to play with it…or destroy it. My friend Jeff and I had a motto : “cure it or kill it”. All of our experimental unguided air vehicles either had to fly successfully or be demolished in some spectacular fashion.

One day, a foam wind-up rubber band powered airplane with a span of maybe a foot and a half had reached that point of no return.  It was doggy as a rubber powered model and by then I was experienced with balsa, dope and tissue and knew how to do better.  This foamy was called “Major Roscoe Hawks Amazing Flying Machine” (MRHAFM).  Actually I remembered the name a little differently but with the miracle of Google I actually found one under vintage toys, circa 1971 and no, I didn’t buy it so I could relive the soon to be described stupidity!

MRHAFM  has roughly the proportions of a high wing Cessna. Clearly if a rubber motor was enough to fly it, a Cox .049 should be oh so much better! At least we had enough sense to chop off most of the nose and epoxy on a scrap of 1/8 plywood for a firewall; surely it would need some up thrust so we did that too! Next, we bolted on a cantankerous Cox “Golden Bee” 049, the kind with the larger gas tank for a 6 or 7 minute run.  In control line models, this particular engine never did more than couple laps before it quit, but for MRHAFM, we figured 10 or 15 seconds would be more than long enough to pile drive this wannabe ice chest into the ground in some spectacular fashion! In retrospect, the fuel pickup of the engine was probably on the bottom instead of the outside as needed for control line, but no matter. A final check out of the flying machine suggested it might still be a little nose heavy (ya think?) so a couple of cox glow plug wrenches were taped to the tail. Perfect, off to the nearest vacant lot we went.  No need to ride our bikes to one of our control line fields (aka the nearest school field), no landing was expected on this flight!

The tank was fully fueled, the engine started and the needle valve was peaked to screaming pitch. MRHAFM was released gingerly into the wind. A steep climb ensued as the unreinforced foam wing bowed to foretell anticipated disaster, but instead she arched over on her back, we figured heading for a glorious “figure 9”. Our anticipation of a full power, straight in crash was quickly dashed.  Instead, the 100 foot loop was completed missing the bushes by mere inches and another giant loop was begun, still tracking straight into the wind! This time, the bottom of the loop was maybe 20 feet off the ground and another loop started. By the third loop, Jeff and I looked at each other in unstated disbelief : “why is this thing still running?” . But run she did. Successive loops gaining more and more altitude and for some reason, continuing to track straight into the wind. She climbed higher and higher until after about 3 minutes or so, we lost both sight and sound of her; MRHAFM was gone, out of sight!

Our ecstasy quickly turned into consternation as the thought of what will happen when she ran out of gas began to go through our heads. Unlike a lightweight well-trimmed free flight model which will lazily glide down to a soft landing when it’s OOS thermal lost it’s hold on it, we knew MRHAFM would come down like a rock when our now best-engine-ever ran out of fuel. A car windshield or hood? Someone’s roof? Our chosen event venue was a vacant lot in the middle of a populated area. When last seen it was more or less over a cemetery, but we decided not to chase after it to find out where it came down, instead left the scene smartly with mischievous grins on our faces and in at least my case, a grand model airplane story to remember and recount nearly 50 years later.

President’s Corner for June-July 2021

Happy Days are Here Again!

Click for a short video

Hello fellow SEFSD members.  I am happy to say, now that the state of California is opening 100%, we are now open to continue our activities starting with our club meeting and a Fun Fly on Saturday June 26th.  Spill the Beans will be the Fun Fly! As far as serving hot dogs, that will happen on our July meeting – so just one more month to go for goodies.

This also means that everyone who is fully vaccinated should no longer need to wear a mask.  However, those remaining unvaccinated should continue wearing a mask until you are fully vaccinated.  SEFSD is not going to enforce this rule. Instead, you are on your honor to use best judgment while following state and local guidelines.

Since this is our first meeting of 2021, you will finally get to meet the new board members which include your new president, me, Jovi.  This is very exciting for me to meet all of you.   During the past six months I have met a few of you at the field on Saturdays (which is the only available time for me to fly, something that I am going to work on and try to get out more often).

So I thought I would give a brief description of who Jovi is.  So let’s get started:

I started with RC airplanes back in the mid 70’s. At that time, you had to build your airplane (Old School) and it took some time before you could actually fly.  My first club was the Torrey Pines Gulls.  I would head out to the glider port and spend a Saturday afternoon when the winds were blowing.   There were full-scale gliders (no hang gliders were around at that time) as well and it was fun.  The first glider I learned to fly was the Wind Ward with a KRAFT radio. The Hobie Hawk was my best glider to fly.  It was fast, it could climb in the thermals, it soared over the cliffs and if you did it right, catch your plane with one bounce to slow it down.  From the mid 80’s to mid-2000, I spent hours away from flying.

I was lucky to travel the world with the company’s I had worked for.  I spent 3 months in Korea working with Samsung’s D Ram chips.  The town I stayed in was called Onyang which had no American food to speak about.  I just lived off French fries and OB beer at this one watering hole. Half way thru my tour I found a restaurant that had steak and A1 sauce on the table. The steak was good!

I have been all over Europe, Brazil and even down in Malaysia!  I arrived in Kuala Lumpur at 3:00 am after a 22 hour long flight, needless to say I was ready to get out of the aircraft, but I was not expecting on the humidity at 3:00am and the heat…OMG.  During those times my mind was still on model planes and during the off times I would be building a TopFlite kit and would spend years building it.   But as the years went on I would fly here and there.  I would have a nitro airplane out in the sand dunes to go fly around. It was a challenge with sand, thick sand, but having balloon tires, a 90 size 2-stroke engine and a tune-pipe turned out to be no problem!  Out by Lake Mead they have a runway setup for models, but not many fliers would show up. Plus it was 100 degrees when I was flying, so it was nice to be the only one and having the background of the Lake Mead was sure nice.  Took my toy trailer out Lake Mead RV Village; yeah, those were the days!  The field is still there.  Today I work for General Atomics where we build the new launch and arresting gear for the new Ford Class Carriers using electromagnetic systems. To be exact, they are called Electromagnetic Aircraft Launch System (EMALS) and Advanced Arresting Gear (AAG).   I invite you go online and check them both out, they are very cool.   Today, I’m back full speed with my RC planes and I am all electric – no more nitro.  I am a scale type person who just loves to fly straight and level, but I’m still working on loops and rolls!!!

I would like to take a minute and talk about safety when flying and this happened a few months ago, but it still worth mentioning:

Heads-Up”, which has three meanings:  Adjective – showing that you are very aware of what is happening around you and it also goes for heads-up football.   Noun – a message that tells or warns someone about something that is going to happen as an example, gave him a heads-up that an investigation was pending.   Interjection – used to tell someone to look up because of possible danger or to clear a passageway.   Out of the three definition of heads-up we are more commonly known as to Interjection.   There are times out at the field, you hear heads-up and sometimes we just don’t look because someone say heads-up, especially when the voice projecting heads-up is not all that loud and, in most cases, we keep our conversation going with a fellow pilot until we hear from other pilots on what just happen.  Aircraft down….

As part of the club’s safety, we need to Shout Out heads-up when your aircraft is in danger and you are over the pits or parking lot.   The end of March there was an incident, well names don’t need to be mentioned……Ok, fine it was me and I was flying my Hawaiian Air.  Take-off was perfect, then 30 seconds into the flight I was in trouble.

One of my favorite old movies is “Animal House” 1978, starring John Belushi as Bluto and in the movie is this one seen where Bluto and D-Day were helping Flounder getting revenge for having Flounder cleaning out the horse stalls and doing push-ups over a horses surprise.   D-day hands Flounder a gun and Flounder goes into Dean Vernon Wormer office where the horse is and as Flounder is squinting his eyes pointing the gun at the horse, which he then points it, in another direction and fires the gun.  But the sound of the gun, killed the horse.  The prank-related accidental death of a horse belonging to Omega member and Reserve Officers’ Training Corps cadet commander Douglas C. Neidermeyer.

Bluto and D-Day run into Dean Vernon Wormer office and the first words coming out of Bluto mouth was, “MERRY CHRISTMAS”.    D-Day goes and says, “There were blanks in the gun”, Bluto again says, “MERRY CHRISTMAS”.   Those same words came out of my mouth when I was in trouble and I yelled it for all to hear.  As I got some control over my Hawaiian Air I again yelled out “Christmas”.  With seconds I had Dennis coming over.  I hear Brad in the background, “you in trouble Jovi” ……Yes was my response.  Dennis got it under control, gave it back to me and still, I was as nervous as I have ever been.  Brad finally took control and landed her safely for me.  Happy was I.  I needed oxygen after that ordeal.

Mark came walking by me and he mention to me how effective I was in yelling “MERRY CHRISTMAS” and how everyone was alerted of the situation at hand.

Here is what happened to me, I relied on the gyro.  When I took off, I thought I had the gyro on, but as I was heading downwind and when I turned base, that is when I notice I was in trouble.  My Airliner was climbing and I’m looking straight up in the sky and flying over the parking lot and Sea World Dr.   I was able to get back over the field.   I have learned that I cannot depend on the gyro all the time in which I did depend on it. It’s a nice feature to have but something that one should not always rely on. So, I am going to learn to fly without the gyro and just keep it for safety…if that makes sense.

However, the morel of this story is when you’re in trouble, it is most important to be yelling out loud heads-up or Merry Christmas!  Remember you must stay north of the fence line at ALL times.  You should never be flying over the Parking lot or the Pits, for the safety of our club members and guests!

On my bench I have the Top-Flite Bonanza which I started back in late 1998.  This was built to take a Satio 120 four-stroke.  Wingspan 81” and the length, 63.6” also included are the following:

  • Robart Air Retract w/scale Robart Struts
  • Scale Navigation lights that work off two 9-volt battery’s
  • Scale Interior Cockpit that is all removable

As time went by, I really never complete my Bonanza.  But as of late, I got my hands back into it.   She is almost ready to go, however I have a few things that need to be done, one is to replace my flap servos.  I had to replace the v-tail servos.  When I was moving them, I notice that the servo arm was going around in oblong circle.  Not good.  Change them to newer Hitec servos and were back to perfection.   Theses retracts are old and not holding pressure.  It is holding pressure for a good 10 minutes in which I only need about 6-7 minutes…. Maybe some risk here…I’ll keep working that problem.

The biggest task I had was figuring a way to change batteries without taking the wing off like I have to do with my Cessna 182.   The Canopy is bolted down with four socket head cap screws, problem with that was getting to those bolts.  I removed them and now I have a quick latch to remove the Canopy.  You’ll see what I mean in the pictures.   It’s actually very cool how this works.  I can put the wing on and I don’t need to hook up the connectors or the air lines.  Once the wing is bolted, flip the Bonanza, unlatch the Canopy, remove the interior and I have access to everything in the aircraft.  Hooked it all up, connect the airlines and place the interior back into place.  Where the fuel tank would have been are where the batteries now sitting.

Balancing was next, I did a rough balance and she seemed to be good with the batteries mounted up front.  Out at the field on T-28 Race’s, April 10, was the day she was going to maiden!  Complete check out was preformed and she was now certified to fly.

Brad did the maiden flight!  She took off like an F-14 Tomcat heading towards the Sunset as seen in “Top Gun”.  As he was trimming her out, he was noticing the balance may be off.  She acted very weird.  He flew her around and she look very nice up in the sky, you think it was a full-scale Bonanza.  Time was running out and Brad was preparing for landing.  She came and touch down and just rolled down the runway.  I was happy, but the next flight, I am going to dial in the balance and hopefully that helps out, which it should!

Ok, I have made enough noise!

Grab your planes, batteries and radio, and let’s go Flying and looking forward to seeing you all at our Monthly Meeting!


JR Models DeHavilland Mosquito

It’s Mosquito Season!

By Steve Belknap

Steve with JR Models Mosquito

Recently I finally put together my JR Models Mosquito kit.  I bought this kit, and one other, from former club member Fred Harris maybe 15 to 20 years ago at one of our club swap meets.  It had spent enough time on the shelf.  Time to build.

Original box lid

The kit was made in the Czech Republic 25-30 years ago.  The craftsmanship is excellent but the instructions (below) are a bit primitive.  The fuselage, inner wings, & nacelles are all one piece of molded fiberglass.  The outer wings are built-up balsa and the tail is balsa sheet.  All very lightly built.

The entire instructions

Here are the original specs:

Span:  49 in.
Length 37in.
Weight: 45 oz.
Motors: 2 x Speed 400
Battery: 7 cell Sub-C Ni-MH or NiCd

I looked through the kit and planned my modifications, of which there would be plenty.


First was the obsolete power system.  A Speed 400 brushed motor gives an actual output of about 50 Watts due to its 50% efficiency giving a total of 100 Watts of power out for two motors.  The plane is supposed to weigh nearly 3 pounds.  This would have given just over 30 Watts per pound.  I was looking for something more like 125 to 150 Watts per pound.  So I went to the Ecalc calculator and found a Cobra C-2814/12 motor that would give me just that.  I decided on a 4S-3000 mAh Li-Po and APC 7×5 counter-rotating props.  I also bought 7×6 props when I want to go faster.

The Ecalc calculator told me I would get 300 Watts per motor out.  A total of 600 Watts.  I also checked the performance chart on the Cobra motor page and saw that the actual tested output would be closer to 350 Watts per motor after calculating an efficiency of 80%.  This would be a total of 700 Watts and would give me about 175 Watts per pound.  (My total weight turned out to be 4lb., not 3lb. as suggested on the box.)  On the 4S pack the current would only be 30A per motor, or 60A total. I used Castle Talon 35 Amp ESCs.  This turned out to be a very good power system.

The Cobra motors did not fit the aluminum motor mounts supplied so I made new ones from .040″ carbon sheet.

The correct size spinner was hard to find but I finally got them from Ebay.  Turns out Ebay has a huge selection of RC parts.  Much better than Amazon.

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