Building a Metal Experimental, the Panther building bolg.


If you are new to experimental aircraft building, it is often hard to visualize the exact techniques that are used to build airframes in the major groups, Steel tube, wood, composite and sheet metal. Companies spend a lot of time showing you how cool their planes are, but until you buy the kit, you don’t see a lot about construction. Wood is an easier visualization for most people, and Steel tube aircraft are often seen and photographed before they are covered. Sheet metal aircraft are a bit more of a mystery to new builders because it is much harder to look at the finished airframe and visualize how it went together in detail without first seeing detailed information, particularly in photos. If you are interested in learning more about how sheet metal aircraft are built, particularly how things like wet wings and control systems are done, I highly suggest following Dan’s Panther Building Blog listed below:

Rachel updates it every few days as the aircraft progresses, and there is a lot of good understanding to be had by following it. Dan is working late into the night every day on the plane and it is at the stage of construction were many components are coming together in their final configuration, a good place for new builders to look, read and understand.-ww

Above, Dan stands beside the Panther prototype at Sun n fun 2012, With 601 builder/flyer Greg Jannaokos. Although the plane Has a steel tube fuselage in the cockpit area that protects the pilot and ties together all the major loads in the plane like the landing gear, motor mount and wing spars, the airframe is otherwise all aluminum construction. Dan’s plan is to teach builders the construction techniques and have them make the sheet metal components from plans or kits, and then have them tie all of the sub components together on the steel tube section that he will supply fully welded and powder coated. Dan’s design is named for the Florida Panther, a rare and beautiful wild cat, a relative of the cougar/mountain lion/puma family.

Two F9F-2Bs of VF-721 over Korea.

Above, Grumman’s version of a Panther. It also has folding wings, is made out of aluminum and started out life with an engine made by General Motors (Allison J-33) This aircraft was used by some OK pilots like Ted Williams, John Glenn and a guy named Neil Armstrong.

If you have this day off from work, and would like to invest a little time in reading, check out the story behind the making of one of the most moving aviation films:  Although I love Waldo Pepper, Spirit of St Louis, and the Blue Max, I still find The Bridges at Toko-Ri my favorite flight film. Todays consumer driven Hollywood requires that every film have 2 or 3 pointless sequels, sold on 30 second tv spots, the story manipulated to tie it into fast food distribution and theme park rides. Todays aviation films like Pearl Harbor barely escape this formula. fortunately you can go back 60 years to a film like Bridges of Toko-Ri and see a real masterpiece that was very closely based in reality. It is not a kind nor uplifting film. it provides no easy answers nor settled feelings. It has a tremendous amount of flying done in Grumman Panthers, long before some thing  called computer graphics made everything we see today fake.

Part of my connection to the film is that it was my Fathers era of Naval aviation. My Father spent many years in Vietnam and two long tours in Korea.  While these both broke his heart and simultaneously hardened him, he has always said that his years at the Naval Academy after being an enlisted man in WWII are what formed him and prepared him for later trials. On his floor in Bancroft hall, among midshipmen, were three other men the were also being formed, Hudner, Stockdale and Lopez. Even at a very young age, in the company very good men, my Father said that these three stood apart from others. Take a few minutes today to read their stories. The links to Hudner and Lopez are from Wikipedia, read the award citation sections closely, they are moving. The link to Stockdale is a story I wrote last year for the Philosophy section of this blog.-ww,_Jr.

( follow the second link to Thomas_J._Hudner,_Jr.)

James Stockdale – Philosophy

Inexpensive panel…….part two.

Note: If the picture is small, try hitting F5 on the top of your keyboard


Here is a look at a very simple panel for our Wagabond. A few days ago it was a brown grocery bag of instruments, some old, some new, and a 8.5″ x 37″ sheet of 6061 T-6 .060″ thick.  I am going to stick it in the plane later tonight.  The actual time to do the layout, cut the holes out, paint it and assemble it was about 4 hours.  Truth be told, I spent several times this long thinking about doing it, contemplating having it cnc routed, trying to think of some clever way of doing it. In the end, the correct answer was just getting out the flycutter, the ruler and a fine point sharpie and going to work on it. I did this after Dan pointed out that I always talk about old school craftsmanship, so I might as well exercise some of it. It pays to have friends who call you out from time to time.


Above: I put all the instruments on the pilots side. The plane has dual controls, but I just wanted things organized in front of the pilot. The plane has been flying with stick controls and a center throttle. I am leaving the sticks alone, but moving the throttle to the left hand side. For some reason, I like throttle on the left with sticks and throttle in the right hand with yokes. I can fly either configuration either way, but it feels awkward.

From the left: The button is the starter. I do not like key starter switches, they are prone to bad contacts, and having your key chain hanging from it will lead to bumping the switch off in turbulence at one hundred feet AGL (ask me how I know this.) The button in this position can be hit with the left index finger without the hands moving from the stick or throttle. I wire this to be capable of being cranked only when the master is on. (the master is on a lower subpanel.)

The next column is topped by the volt meter. I do not like nor condone the use of ammeters. In this case, if the volt meter reads 12.8, just the battery is working, anything above this shows that the charging system is on line and ahead of the power demand. In operation this shows 14.5 volts or so.  Below this is the hole for an on-off-on snap action, MS rated switch for the ignition. This does not run through the master. It runs directly from the battery (with a 30 amp fuse 2″ from the battery, protecting the line from burning in a dead short, but never allowing the fuse to blow from running the ignition.) Again no key here, the plane is parked with this switch and the master in the off position. This has the least connections and contacts, and thus is the most reliable way of doing it. (I do have a remote, very loud security warning system for the plane, it has a three digit security code: 3 – 50 – 7.)

Next column, a 12 volt turn coordinator. I only put this in because I had it laying around and it was the easiest way to put a skid slip ball in the plane. I look at the ball more than any other thing in a plane. Dan tells me he never looks at one, and wouldn’t bother to put it in. I really doubt that not having one is the secret to Dan’s airmanship, so I will just keep putting them in my planes. Under it is an altimeter from a 1970s Cessna.

The next row is a used airspeed with a range that is close to the planes envelope. I had removed a 200 mph true airspeed that was in the Wagabond. Under it is the Stewart Warner 82636 Tach. 

The next row is three autometer mechanical gauges. Top is oil pressure, oil temp and EGT. There is a 1/4″ hole below the EGT for a mini DPDT switch so I can have two senders, one in each side of the exhaust.

Next column starts with a suction gauge that is only plugging the hole until I buy a micro radio to put in the hole. Beneath it is a mechanical MAP gauge, and under it is a CHT from a certified plane, probably something WWII vintage. Notice that none of the gauges for the engine have electrical sending units. Yes, there are probes, but these are non powered bi-metal senders, not the kind of senders associated with electrical instruments or glass cockpits.

Williams axioms of instrumentation:

 A) It is only as reliable as the sender; In the last 10 years, every instrument error I have seen on builders projects or worked on, was related to poor electrical senders. It doesn’t matter how great your glass cockpit is if the specified senders suck eggs. I am not suggesting electrical things are bad, but they are not fool-proof.

B)  I would rather have no instrumentation than have ones that occasionally gave false information. Anything that cries wolf often will have you doubt the warning when something really is going wrong. One of the things I hate about automotive O2 sensors running lean/rich gauges is that they read “green” (normal operation) when the sensors fail or lose their ground, which happens a lot. As an absolute design requirement, nothing in real aircraft instrumentation reads OK when it fails.  IFR Flight instruments actually display flags when they fail, it’s that important.

C) It is better to have little information about a reliable part than the reverse. By deleting the TC, EGT and using less expensive gauges I could make an even simpler panel that would cost $275 or so. I am setting the Wagabond up with a $1,000 overhauled MA3-SPA carb. These have excellent mixture distribution, and they don’t ever run lean unless you command them to do so. I don’t need 6 CHTs and 6 EGTs for my engine. I believe that anyone who has a $1,000 6 egt/cht monitor keeping tabs on a $275 motorcycle carb is making a serious judgement error.

D) Mechanical gauges with needles offer unique information. I can watch a mechanical oil pressure gauge and if the needle flickers while going up I can tell the bore of the oil pressure relief isn’t smooth enough. You can see rate of change with a needle. Watch the hand on an altimeter in climb. If it is moving as fast as a second-hand on a clock, the plane is climbing 1,000’/min. human eyes are very good at watching rates of change. If your watching climbing EGT on a needle, as it slows you can guess where its going to peak far better than looking at a number displayed on a screen.

E) Electrical instrumentation lies depending on voltage and grounds. If you have electrical instrumentation, warm up the engine, run it at a steady rpm and note the oil pressure. Then take the charging system off line. You need to be aware that many systems will read different numbers depending on if the system is seeing 12.8 or 14.5 volts. Digital electronic systems run between 0-5 volts, and they are particularly susceptible to poor grounds, mediocre crimps and very slight corrosion on connections, three things that happen is homebuilt aircraft. More than one pilot has been on the edge of a heart attack aloft when watching his oil pressure sink to zero, only to find out later it was just a bad ground on an electrical sender.

F) Mechanical instruments are Bad-Ass. On my workshop shelf I have a manifold pressure gauge that reads to seventy five inches of manifold pressure. (22 pounds of boost) It is from a Lockheed P2V-7 Neptune which had 3,700 hp turbo compound radials. It glows in the dark because the numbers are painted on with radioactive paint. There is a pretty good chance that this gauge flew in the cuban missile crisis or attacked the Ho Chi Minh trail. If it could talk, it would tell you that the cold war wasn’t always cold, and it would remind you to think about the people who fought it, but it can’t say anything. It just sits out there, night after night, its faint green glow quietly remembering thousands of hours aloft, in the company of men, men now mostly gone…. In another 15 years, all of the glass cockpits of today, all the MGL stuff from South Africa, all the I-Pads built by virtual slave labor in China, all the garbage like Blue Mountain and Archangel will all be lining the bottoms of landfills accompanying used diapers and copies of People magazine featuring the Kardashians. 15 years from today, my MAP gauge will still be quietly glowing, trying to remind people that there was a time when being an aviator was about skill, reliability under pressure and courage.-ww

Bruce Culver’s Fokker XXI project concept.


Builder Bruce Culver wrote the note in blue below. He is kicking around a replica of a historic, but somewhat unknown, WWII fighter.  The letter caught my eye because it has some elements  I can comment on from personal experience. I included a three view and a spec. sheet from the original aircraft. These planes fought in one of the least understood facets of WWII, the ‘winter war’ , a 105 day savage conflict between the Finns and the Soviets. In spite of fantastic Soviet numerical superiority, the Finns fought them to a halt in minus 40 degree temps. Their national pride soared, but they learned the bitter lesson that they could count on no allied support beyond gestures. My comments on the project are in green and follow the letter-ww

“This is outstanding, William – thanks for letting us in on the secret that the ancient steam gauges I want to use will be pretty cheap because no one wants them anymore. I wonder what the backup system is for those glass cockpits if you have a major electrical failure – if the fancy panel loses power, you have NO instruments at all. And as you mentioned by implication, nowadays few instructors teach students to fly by the feel of the airplane. I KNEW I should have learned to fly in the ’60s….. Well, there is a lady who teaches around here in a decathlon,,,,,

I want to build a simple LSA replica fighter using the Loehle P-40 as a starting point and ending up with a Fokker D.XXI as the preferred design. I have tried three times to order the information pack from them and still don’t have it, but so much for customer service. Nonetheless I’d like a plane that will be fun to fly, safe and won’t break the bank at Monte Carlo. I also want to build the whole airplane and the engine, so I know what’s in both and can check better for problems, maintenance needs, etc. It will require a complete rework of the kit fuselage, but this gives me a chance to reinforce the cockpit area. One of their customers wrapped their P-40 prototype in a ball getting too slow on landing and stalled it in, but he almost walked away….. The pictures ain’t pretty. So, it’ll be wood, but good wood. The great thing about the Loehle P-40 and the Fokker D.XXI is I can leave most of the kit as it comes in the box and change only the cockpit and forward fuselage areas, so flying characteristics should be the same as the kit design.

My point is, Fokker D.XXIs didn’t have glass cockpits, so I can cheerfully go for the unwanted orphan steam gauges. And a Corvair engine, probably a basic model as it will power an LSA. And remember, there is always a place for knowledgable troglodytes…..”

Fokker D.XXI.svg

General characteristics


Bruce, I like the basic idea and the XXI is a well proportioned aircraft that could be scaled to fit the task. At 28″, the Corvair is narrow enough to fit inside the radial cowl as long as the scale was bigger than 62% (5/8ths). At the Zenith open house dinner this year, Mike Loehle and his wife sat at the table with Myself, Becky Shipman, Dan Glaze and Dave Gardiea. Mike was there to support his covering and painting systems. In recent years, his kit company, just like all others, has felt the pinch of the economy. In years past, Loehle has provided 100s of builders very highly regarded kits, but the company operates in a very scaled back capacity from the peak years. If you sat across the table from him you would understand he still cares about builders, but has trouble justifying a full-time communication staff person. A good friend at out airport has a Loehle P-40 that is about 90% done. Let me say that this aircraft is way to lightly constructed for Corvair power. It is intended for two-stroke rotax engines only. Many more things would have to be beefed up than just the front fuselage.

As an alternative approach, think about the WAR replica aircraft. My next door neighbor built and flew a FW-190 powered by an 0-200. We also had one of these airframes fly on a Corvair in Europe a few years ago. They are 1/2 scale, and are too small except for medium and small pilots, and they don’t have the wing area for LSA. But, the wooden ‘dehavland box’ construction, fared in with non-load bearing foam and glass has merit. A number of one-off 5/8th scale fighters have been made this way. In St Augustine there is a 70% Hawker Hurricane that is probably made from this technique. For wing structure, you may wish to get a look at how KR-2s are made. 10 years ago a group of KR builders tested a new airfoil, and had coordinates for an 18% thick root section. This could be laminated into a very strong box spar. There are a number of low wing wood aircraft that could be studied for ideas like Jodel/Falconair single seaters. You can always look at a steel tube fuselage with wooden formers and fabric, it is possible to make a very shapely plane this way. Even if you don’t yet know welding, a challenging and unique aircraft like you are considering will require learning a number of skills. -ww


Zenith 750 Builder Blaine Schwartz


Below we have two photographs of builder progress from Blaine Schwartz of Texas. Blaine is a Zenith 750 builder, and he is headed to Corvair College #22 March 9-11 at KGTU in Austin, Texas, in less than 10 days. At the College, he is going to assemble and test run his Corvair powerplant. It features a set of 2850 cc pistons and cylinders from us, a set of Falcon heads, and a bottom end featuring a Roy bearing. Blaine has already purchased every Gold System option that we have for engine building. Additionally, he picked up a powdercoated 750 Mount from us and a number of the other required pieces for this 750 installation. Success doesn’t happen by accident, it is the end result of planning and action. If you have not yet signed up for Corvair College A#22, the registration is still open for a little while longer and we’ll be glad to have you. The Central Scrutinizer Ken Pavlou is planning on shutting down online registration  3/1/12 at 23:59 EST. Sign up today and set yourself on the same path that Blaine has followed, which put him in a position of success this year.

There are many ways to clean the case but pressure washing is a good start. Notice that Blaine has his cases sitting on wooden blocks to prevent them from having their mating surfaces touch anything that could scar them or affect their fit. Pressure washing Corvair cases with all their nooks and crannies will leave you just as wet as the cases.

Above, Blaine’s 750 fuselage on the gear. His engine mount is powdercoated gray, our standard color. We are bringing several of them to the College, along with many other installation components, and many boxes of Gold System components. If you are headed to the College, we highly encourage you to order the things you would like in advance for pickup at the event. Although we are bringing a lot of stuff, we almost always sell out of many of the popular items.

Blaine’s field of expertise is the management of very high end aviation systems procurement. The man seriously understands how to plan an aircraft project. Getting organized is second only to getting started. Corvair College #22 in Austin is a great place to get your aviation plans in gear and going.

Be there, Aloha.