Jodel D918

[Old Koreelah]

In response to a bit of interest shown on another thread

 

(http://www.recreationalflying.com/threads/airasia-flight-qz8501-missing.128911/page-7#post-471045)

 

here is my Jodel-building story.

 

The Jodel Story

 

 

The Jodel story starts with two French aviation enthusiasts, Edouard Joly and his son-in-law Jean Delemontez. They worked together repairing and designing aircraft before WWII. After the war they combined their names in a new business: Avions Jodel.

 

The first design actually completed and flown was the D9. It was greeted with enthusiasm and within five years 200 of them were flying in France.

 

"...The basis was light weight, together with strength (the design load factor is +9g -4.5g at 600lb.) and simplicity and careful choice of materials. Much thought went into the wing design which is after all the most important part of any aeroplane. Delemontez said, "It had to be simple, an elliptical plan form is the most efficient, like the Spitfire, but it is very complicated to build. I wanted something which was straight forward, so I decided on a flat rectangular centre section of constant chord and aerofoil section which avoided laminated spars, and could be built around a box section spar which was not only extremely strong but was also light. It had to be very efficient also."

 

“An NACA 23012 aerofoil section was chosen for the rectangular centre section, the up-swept tapered, outer panels changed both in incidence giving washout, and in aerofoil section. Thus in level flight the main lift comes from the centre section, the outer panels giving little lift and very little drag. However in the climb and at the stall the outer panels are designed to contribute to lift and stability. ( The former quality because at the stall the outer panels have a positive angle of attack, the latter quality because the inner part of the wing stalls before the outer.) This enables a very low stall and landing speed. So the wing was designed and became known as the "Delemontez trapezoidal planform"..."

 

This came from a history of Jodel written here in Australia by Frank Rogers, who had drawn improved plans which are still used by builders throughout the world. Larger Jodel models were built, carrying up to five people, mostly being constructed from plans.

 

It is a tribute to the design of the little D9 that many are still flying today and the basic design has been extended so much.

 

Frank Rogers' history of Jodels:

 

http://www.jodel.com/index.asp?p=rogers1&articles

 

http://jodel.com/index.asp?p=rogers2&articles

 

http://www.jodel.com/index.asp?p=rogers3&articles

 

http://jodel.com/index.asp?p=rogers4&articles

 

http://www.jodel.com/index.asp?p=rogers5&articles

 

http://www.jodel.com

 

My Jodel Story:

 

I bought my little Jodel D9 because it was the best aircraft I could afford and it offered scope for significant improvements. I have progressively modified it to improve safety and utility, based on advice from Frank Rogers and M. Delemontez- the original designer.

 

First I enlarged the cockpit to fit my 1.94m frame. The fuselage was split down the middle and widened at the cabin by 100mm. The seat was laid back and the turtle deck raised and streamlined. An extra pair of spruce longerons were added to connect this to the firewall, which was moved forward. The floor was lowered about 60mm, streamlined and curved. I added a couple of belly doors for access to the fuel system and rear fuselage.

 

I built a canopy to suit (learning a lot about bending acrylic in the process.)

 

The canopy slides at the front and has radius arms at the back. It can be opened in flight, but airflow makes it want to slide shut.

 

Engine:

 

The original Stark-Stamo engine was at the end of its reliable life and I was persuaded to replace it with a 1600 VW. Despite my protests, they insisted that iron barrels were the only way. I missed that warning bell...

 

A starter motor was a safety priority to me, after the old engine stopped a few times on taxiways. It was more than the inconvenience of having to undo the harness in the tiny cabin and clamber out to restart the donk. Although starting was easy, there was always the danger of making a mistake around a spinning prop.

 

After much searching, I found a tiny starter off a Yamaha outboard. It turned the right direction and I mounted it on the oil-pipe studs at the front of the engine. After some intricate work with an angle grinder, I adapted it to mesh with the ring gear from a Holden 202 Automatic. I have no lathe and had never used one, but made a 340mm diameter spinner on a spindle mounted vertically in a bench vice and shaped with hand tools.

 

Electric start meant I needed a battery and a charging system. I got a Kubota dynamo out of Tennessee and mounted it belt-driven off a pulley on the rear of the engine. To avoid the ugly bump seen on so many VW cowls, next came a low-profile electronic ignition system.

 

After encasing the engine in glad-wrap, I built a streamlined fibreglass pressure cowl around it. Ground testing the engine with the original Hoffman prop showed everything working well.

 

All this took a couple of years; my dream was to fly it to Narromine for AusFly. Other builders would understand the frustration as each Easter came and went.

 

Despite my best efforts to keep it light and carefully weighing each component, I got a nasty shock when I borrowed some digital cattle scales from a neighbour. My two years of effort was wasted: the beast was hopelessly nose-heavy.

 

With morale at rock-bottom I ripped the whole lot out and spent up large on the engine I had originally wanted. After all that practice, fitting the third motor was much easier. It weighed far less that the VW and had mobs more power. Thank you Jabiru!

 

I designed a new engine mount and tacked it together in a plywood jig- then took it to a proper aircraft welder who did a neat job of it.

 

Building a new pressure cowl around the smaller Jab engine was relatively easy. I enjoy creating complex and functional shapes in fibreglass. Modifying the exhaust system to fit the narrow cowl was harder. No local welders would touch anything from an aeroplane, so I had to do it myself. Not neat, but functional.

 

Aircraft Carrier

 

I modified the plane so I could fold the fuselage around over the wing for transport and storage. The original idea was to be able to do this at the end of a long trip, but I had to make the whole process dependent on the dedicated carrier. This is what it looked like a few years back:

 

 

A summary of innovations in the design:

 

Safety

 

Windows in floor to improve visibility

 

Spring-mounted wingtip strobes resist hangar rash

 

Automatic crash-activated battery isolator

 

Impact padding under seat & canopy (I also wear a helmet)

 

Cockpit double layered with plywood: increased strength, to reduce chance of spruce-inflicted splinter injuries in accident

 

BRS parachute

 

Trim wheel incorporating back-up elevator control

 

Sealed battery, isolated behind firewall

 

Digital CO detector

 

Fire extinguisher plumbed into engine bay

 

Chrome-moly canopy hoops; alloy centre member to carry fence wire over pilot’s head in a crash

 

Impact-resistant 2mm polycarbon windscreen; acrylic canopy to allow break out in event of flipover

 

Landing lights

 

Bright yellow paint above & darker green underneath to improve visibility

 

Fuel System

 

Wing tanks rubber-mounted behind spar, wrapped in kevlar, with vent tubes to wingtips (large-bore to carry pressure pulse in a crash and if inverted, to drain fuel far from cockpit)

 

Wheels

 

6X6 tyres for rough fields

 

Disc brakes

 

Streamlined wheel spats, quickly removable.

 

Tailstrut

 

Home-made, streamlined glass/carbon fibre tailstrut, mounted concentrically with rudder, adding to rudder effect

 

Comfort

 

Fuselage widened 100 mm

 

Cockpit rear section laid back & head-room increased

 

Cabin floor lowered 60mm, widened & reinforced

 

Arm rests stiffen sides & facilitating exit

 

Steamlined canopy to reduce noise

 

Fibreglass seat moulded to pilot’s backside

 

Efficiency

 

Drag reductions- large spinner, wing filleting, streamlined fuselage & undercarriage

 

Engine cooling air exits in the low-pressure zone above the wing

 

Storage

 

Luggage bays- behind firewall & behind pilot

 

Door under wing for access to rear fuselage- storage of empty fuel drum, suit, or backpack

 

Tools & tie-downs stored behind firewall

 

Ground transport

 

Pitot, fuel lines & electrical connections bundled into one “umbilical” allowing fuselage to pivot over wing

 

Loading plane onto carrier & folding for transport takes one person 20 minutes; no controls are disconnected

 

After years of building all these improvements into my little plane, I entered it for judging at AusFly, hoping it might get a mention in the innovation section.

 

I must confess to some disappointment when the judges showed no interest in my offer to demonstrate some of the safety features. A great paint job seems to be more important.

 

Wing

 

All the added weight increased the stall speed. To compensate, the wing was rebuilt larger, to D18 specs and flaps added. The Jodel wing is remarkably efficient, but it’s planform increases the risk of wing drop at the stall. To counter this, wing fences and stall strips were added. The carrier required a bit of surgery to allow the fences to fit. Testing to get the best low-speed landing performance is ongoing.

 

Blunders

 

It’s said that humans possess forty types of intelligence, but that most of us are lacking in one or several departments. After much hard experience, I finally discovered that one of my deficiencies is no capacity to understand how long it will take to do something. (My 5-year house is still unfinished thirty years later. Somehow, my better half is still with me.)

 

With the next Easter far away, I thought there was plenty of time to add one more innovation to my new aeroplane.

 

Efficiency is everything right? Good designers maximize performance. Why waste all that heat from the engine? I read up on exhaust augmentors and became a convert. Augmentors were once common, especially on aircraft built by Canada’s de Havilland. They do a great job of sucking cooling air through the engine.

 

I could not understand why they had fallen out of favour so, armed with the results of NACA research done in the 1940s, I built a matching pair each side of the forward fuselage, exiting beside the cockpit. They added about 4kg, but flight testing with them installed and then removed showed 4% faster climb rate and better cooling. I was so pleased with my own cleverness I put up with the ear-shattering howl as the engine came on song.

 

After my first long trip, to Temora, the first thing I did was buy a good NC headset.

 

This reduced the horrible noise, but I soon removed the augmentors, re-routed the exhaust under the cowls like everyone else, and didn’t notice the marginal loss of climb performance. Cooling is still okey, because the low-pressure zone above the wing helps suck plenty of air through.

 

Anyone want to buy a hardly-used, top brand NC headset?

 

An ag pilot once told me that the tailwheel has to take a lot of punishment. Ignoring this hint, I went ahead and replaced my robust, but heavy solid roller with a light, streamlined Bunnings-grade plastic one. It failed on my first trip. An after-hours hop over the fence of Temora’s lawn-mower repair shop yielded a Victa front wheel which got me home. After three more Bunnings wheels I fitted one off a wheelchair and all is well.

 

Performance

 

At MTOW my D918 can get off the ground in 160m, but the landing run is considerably longer.

 

It is now a useful long-distance tourer- as long as I keep luggage to a minimum. My wife helped me cut down our 1970‘s Big-W tent so that it slips over the left wing; no poles required, saving weight.

 

It’s a delight to fly. Cruising high above the turbulence I can fly hands free and steer it with movements of my head.

 

Best cruise speed is a compromise: keeping under the 100kt limit of the Jodel and above the Jabiru’s vibration band at 2400rpm.

 

At 2800rpm (90+kt) it burns 12.5 litres per hour.

 

At 2600- (80kt) burns 10 litres. Fifty litres gives a safe range of 320nm. Experimenting with my improved new CHT/EGT gauge might stretch this beyond 350.

 

 

 

 

 

 

 

 

 

 

[Stoney]

A fantastic story Old Koreelah, thanks very much for taking the time to write about your experience.

 

I doubt that I will ever build my own plane, but I take my hat off to those of you that do.

 

I can only imagine the feeling of the first flight in a plane that you have lovingly laboured over for so long. I wouldn't think that there would be many things that could equal it.

 

I am impressed with the design features built in, it sounds like you have thought of everything.

 

I particularly like the safety features of fuel venting, plumbed engine fire extinguisher, BRS parachute and crash activated battery isolator.

 

(I have been working on a crash activated BRS parachute, but I think I have just found a flaw in my thinking)

 

Again, a big thank you for sharing your story, I found it inspiring.

 

 

[Downunder]

Nose reminds me of a FW190D...gear off a Stuka...? Canopy off a p51 ...and wings off one of those "clipped" spitfires....

 

How do you find the spats and are they fixed with the wheels moving up and down inside?

 

 

[SDQDI]

Nose reminds me of a FW190D...gear off a Stuka...? Canopy off a p51 ...and wings off one of those "clipped" spitfires....How do you find the spats and are they fixed with the wheels moving up and down inside?

Awesome question downunder. I was hoping he would share a little more about them especially the differences with economy ect.

OK I hope you have some pics of the spat build?

 

 

[Old Koreelah]

Nose reminds me of a FW190D...gear off a Stuka...? Canopy off a p51 ...and wings off one of those "clipped" spitfires....How do you find the spats and are they fixed with the wheels moving up and down inside?

Sounds like I got bits out of an old Warbirds parts bin! The reality: I was no doubt influenced by those iconic designs.

The canopy, like everything else, is my own design. It took months and I still didn't get a perfect curve on the perspex.

 

After a lot of reading about aerodynamics, I built the spats the hard way. Two months grovelling around under the wing in 40+ degree heat. I wrapped the UC in glad wrap and built up "planks" of Klegecell to shape them. Then lots of shaping with hand tools, a few layers of fine glass and cut thru them vertically. They are mounted on the axles and slider, and open quickly for inspection. They come off totally in a couple of minutes.

 

I was never a fan of ugly big wheel spats but thought they'd help extend the glide if the engine failed. I did extensive testing with them on and off and was amazed at the difference they made:

 

At 2800rpm speed increased 4%, fuel burn reduced 8.43%.

 

At 2600rpm no noticeable speed benefit, but fuel burn down an amazing 13%. That must be the cruising sweet spot.

 

 

 

[jeffd]

hey old koreelah that was a great read im up in qld near gatton and fly out of coominya flight training do u get up this way much ,i will certainly be looking at any jodel close up in the future ,a two seater will be nice to have but a single seater like that would be something special i reckon

 

 

[Old Koreelah]

Even better than having a nice little plane is having somewhere safe to keep it. That's often half the cost, Jeff.

 

Might see you at Trevor Bange's on March 14-15.

 

 

[jeffd]

i will be there actually will keep an eye out for u , is the d9 the only jodel approved for raaus would 1 of the 2 seaters qualify

 

 

[Old Koreelah]

i will be there actually will keep an eye out for u , is the d9 the only jodel approved for raaus would 1 of the 2 seaters qualify

Quite a few Jodels fly with numbers. A few D9 single seaters and quite a few 2-seat D11s and the odd D18, but there are larger ones about.

 

 

[microman]

Just noticed the posts re the D918 - you really have made the aircraft fit your requirements. You may remember meeting me in NZ at Taeri a couple of years ago. For the sake of jeffd and any others in Oz who may be c0nsidering the D18, mine is fitted with a Rotax 912S - it cruises at 100kts @5000 rpm, and climbs at 1000 ft/min fully loaded. The D18 design is fantastic - problem is the underperforming VW engines most of them have. With the Rotax (or even a Jab) they really get up and go and they fit within the NZ microlight category so no problems with RA-Aus. Mine is 302kg empty with an MTOW of 530 kg.

 

 

[Old Koreelah]

Nice to hear from you Graeme! The D-18 is a great design. My iPhone pic of yours scored a double-page spread in our magazine after my trip to Taeri. Per capita I bet your country has more flyers and much more innovation than this one.

 

We don't hear much about flying in NZ. Tell us what's been going on.

 

 

[microman]

The growth area for aviation in NZ is definitely microlights - lots of GA pilots fed up with the cost of maintaining a GA aircraft and the stringent (and expensive) medical requirements are migrating over. We are fortunate here that CAA's only involvement in microlights is the initial inspection and annual registration - everything else - licensing, instruction (done through clubs, not flying schools), mods etc, is controlled by RAANZ (Recreational Aircraft Association of NZ). We are also very fortunate that the definition of a microlight is extremely generous - MTOW under 600 kg and stall under 45 kts and it is a microlight.

 

Our club has over 170 members, two club aircraft (P92 Tecnam and Rans S6) two hangars and a settled base at Rangiora airfield. Because of our mountainous terrain, one major growth area is in aircraft such as the Zenith 701 and the Savannah - several of our members have imported these aircraft from the USA and they delight in landing on mountain strips and in riverbeds (much to our disgust - we have to stick to decent-size paddocks and actual airstrips).

 

However even we are not immune to increasing bureaucracy and costs - Rangiora is now an MBZ with landing fees ($10 a day or you can pay a lump sum for the year).

 

 

[Old Koreelah]

We often look across the Tasman with envy. Maybe you could use this pic as your avatar:

 

 

 

[DonRamsay]

OldK,

 

I'm also planning to go to Trevor's for the Clifton Fly-in. I'm planning on leaving from YCNK early on Saturday morning with my route taking me via Scone/Quirindi/Gunnedah/Narrabri/Moree. Probably fly back Monday morning.

 

I was going last year but the weather beat me on the day and it just wasn't worth the risk.

 

Hope we do better with the weather this time. Look forward to catching up again - its been a while.

 

 

[Old Koreelah]

OldK,I'm also planning to go to Trevor's for the Clifton Fly-in. I'm planning on leaving from YCNK early on Saturday morning with my route taking me via Scone/Quirindi/Gunnedah/Narrabri/Moree. Probably fly back Monday morning.

I was going last year but the weather beat me on the day and it just wasn't worth the risk.

 

Hope we do better with the weather this time. Look forward to catching up again - its been a while.

Great to hear Don! Saturday March 14 is our monthly FlyDay, so we start the day with a BBQ breakfast at QAC clubhouse. I plan on heading north after that, and there may be one or two others from our club. Looking forward to seeing you there.

No rush, we have all day to get to Clifton.

 

 

[DonRamsay]

Great to hear Don! Saturday March 14 is our monthly FlyDay, so we start the day with a BBQ breakfast at QAC clubhouse. I plan on heading north after that, and there may be one or two others from our club. Looking forward to seeing you there.No rush, we have all day to get to Clifton.

This just gets better and better. I'll see you at Quirindi!

What time will the bacon be ready?

 

 

[Old Koreelah]

This just gets better and better. I'll see you at Quirindi!What time will the bacon be ready?

0800... and say nice things to the weather gods!

 

 

[facthunter]

The BOM is a non prophet organisation. Nev