David Melby's 102.5 Cavalier - Mine will look similar to this day.

A 102.5 is a homebuilt-type plane. It has a wooden airframe covered with plywood and fabric. It's basically a 2+2 seater (ie. there's room for 2 children in the back or some extra luggage if you prefer up to around 55kg). Cavaliers with an engine of about 125HP will cruise along at around 130mph or 140mph (around 210kmph plus).

Check out the progress of my Cavalier by clicking on the links below
Last updated on: 2nd June, 2009

Main Spar Construction
Main Spar, Sub Spars & Wing Ribs
Wing Flaps
Instruments, Panel & Associated Stuff
Chrome Moly Parts
Landing Gear
Fuel Tanks
Component Weights
Test Joints & Tools
Homebrew Comm Antennas
Useful Links etc


I have joined several pieces of 10mm X 75mm Douglas Fir (Oregon) to create some spar laminations of suitable lengths. The longest laminations are 7.5m and as wasn't able to get full length timber, I was faced with "scarfing" shorter pieces together to make up the length. Some photos of the joints and the over-head planer I used to prepare them can be seen further down on this page.

Below are some photos of the construction of the top flange of a Cavalier 102 wing spar - I can hardly wait to get the spar ready to start attaching wing ribs to it!

 Glue being applied to spar laminations
 Laminations glued & screwed ... well, clamped anyway!
 Spar laminations forced down to top of spar bench
 Another view of the clamped spar flange
 Overhead planer for creating scarf joints
 Scarfed spar lamination

One important lesson learned - there's no such thing as too many clamps!

Here are the long awaited photos of the lower spar flange and some other surprises! These photos were taken during December 2000 and January 2001.

 Lower spar flange glued and clamped against the jig
 Spar laminations forced down to top of spar bench
 Upper and lower flanges removed from the jig
 One end of the flanges after a lot of "tapering"
 Upper spar flange complete with a scarf joint
 Wing attach and landing gear blocks "in the raw"
 Attach blocks fitted the LHS of spar
 7.5m of spar flanges, diaphragms etc in my driveway
 A good view of the dihedral

Since the above photos were taken, I have fitted 2.0mm birch ply shear webs to both sides of the spar and some 5.0mm doublers to the landing gear area. Work has begun on the rear spar and drag spars as well as some wing ribs. I have had to re-make some ribs due to my decision to fit reflexing flaps (a 1988 improvement by Stan McLeod) instead of the original split flaps.


Below are some photos of the main spar, sub spars, wing ribs and the beginings of ailerons. The progress so far to August 2001.

 Section of the main spar with the shear web attached
 The completed main spar
 Frame work for rear spars and one drag spar
 The drag spars with the shear web attached
 Centre spar with shear web being attached - rear view
 Centre spar with shear web being attached - front view
 Two sets of wing ribs - sick of routing already!
 Rear rib #10 being attached to the spar - using the nose rib for reference
 Rear ribs #0 - #5 attached to the spar - a couple slightly prematurely
 Rib block glued into place - staples are handy as clamps
 Take the rib block back off again! The drag spar wont fit with this rib here! AAARRRGH!!!
 Aileron ribs in place on the aileron spar - note the strange angle
 Aileron ribs at the hinging point
 Aileron spar with ribs attached - no trailing edge etc yet


The original Cavalier 102.5s were fitted with split flaps, although some builders omitted the flaps completely. The split flaps extend (decend) from the lower surface of the wing and act like a speed brake to slow the aircraft down. The upper surface of the wing does not move - therefore the wing is "split" where the flaps are ...get it! There is a picture here

The later Cavalier plans show reflexing simple flaps (also called plain flaps). These flaps can be set at a negative angle - for example 12 degrees above the top surface of the wing. When set as such, some of the drag created by the washout in the wing should be negated giving a higher cruise speed. It will be very interesting to see what effect the reflexing has. The flaps and flap shrouds should do a pretty good job of modifying the wing chord and increasing the camber to allow much slower flight than the split flaps. That should be great for those short grass strips. I do not know of any Cavaliers flying at the moment with the reflexing flap setup. As soon as I get a flight report, I will put some comments up here.

Here's some notes I received from Stan McLeod including comments from a competition glider pilot:

Having the ability to go to negative flaps is like changing to a high speed airfoil while in flight. The stall speed is higher, the drag is reduced mainly induced drag and the attitude of the fuselage is changed which also reduces the fuselage drag. Are stall and cruise speeeds inceased appreciably ? what % (average)?? Stall speed at "cruise speed" isn't too important, ,just remember to put them back to neutral or down when leaving "cruise mode".

This from a very highly quallified ,competition ,sailplane driver:
All high performance gliders have camber changing flaps, usually coupled to the ailerons so that the whole wing changes. Landing say +35, slow flight say 0 or +8 and high speed -8 or -12 degrees. Are stall and cruise speeeds inceased appreciably? Well it is hard to say but I used to fly a glider that had no flaps at all and it had a top speed of about 75 mph. Now with camber changing flaps and laminar airfoils the VNE is 151 knots, 174 mph for smooth air and 116 knots, 134 mph for rough air. The difference in competition is huge. Newer gliders are much higher than that. While flying I'm constantly changing flap settings; +8 for thermalling, then +2, then as I speed up,0, -8, then -12.

Here's an explanation of why reflex flaps work, as the glider pilot alluded to.

A) When an aircraft leaves the ground, it has enough lift to fly!
B) As speed builds to cruise, lift also increases (unnecessarily)
C) At cruise, in order not to climb with the extra lift (more than is needed to fly), we put the nose down and essentially dive off the extra lift
D) This puts the fuselage in a nose down, tail up attitude which produces high induced drag
E) Reflexing the flaps dumps that extra (unwanted) lift, allows the fuselage to attain a more level, streamlined attitude, consequently reducing drag and allowing increased speed
F) This will also, to a degree, lessen the drag created by wing washout

1) Stall speeds will increase with the flaps reflexed - not a concern in level cruise flight
2) Reflex flaps are intended to be used only on long cruising flights, not circuits or short local flights
3) Reflexed flaps must be returned to neutral at the cessation of cruise flight
4) Only gentle manoeuvres or level flight with reflexed flap

 Suggested flap settings (for your operations manual)

During my searching around, I did find some real world experience relating to other aircraft types:

TAS test in a Lancair 235 at full throttle
reflex 8 deg - 170 knots
reflex 6 deg - 173 knots
reflex 4 deg - 170 knots
reflex 2 deg - 164 knots
I'm not sure what the usual full throttle speed of a Lancair 235 is.

Various Maules use a 7 degree reflex flap setting for an extra 3 to 5 knots cruise.

I have seen a claim of a Bearhawk gaining 10 knots in cruise speed using 5 degrees of reflex.

I also believe that various RVs use a reflexing flap system, but I do not have any data on any performance gains. If you do have, please let me know.

 Reflexing flap diagram

I know of at least two builders who have decided to use reflexing slotted flaps of their own design (have a look at the links at the bottom of this page). The hinging method appears to be a bit more complicated, but they expect a few benefits from the modification.


I wasn't satisfied with my existing instrument panel bow. It had been made with a different instrument layout in mind, but I now wanted another 10 mm of height for instrument clearance. Even though it was a bit of extra work I am happy that I have a little bit more room to rearrange my instruments into the order I want.

 Rebuilt instrument panel bow in progress
 Close up of panel bow laminations
 Here's my initial "loose" instrument panel design
 Pitot tube and static vent tube (based on that described by Tony Bingelis)
 Volt and Amp meter waiting for an enclosure and instrument face
 Capacitive fuel gauge - although you can't really tell yet!
 Stick grip pattern thanks to Mr Nylex!
 In case of finding a tornado in the cockpit, you might need this!


Circa 2004
Progress lately has been slow (isn't it always?) largely due to the difficulty in obtaining suitable steel for the landing gear (5" X 1/2" 6150 steel) or an alternative at a reasonable price (i.e. spring aluminium or fibreglass). In the meantime, I obtained some 4130 Chrome Moly steel to make most of the required fittings, hinges, joysticks etc. The engine mount is missing at the moment due to the lack of engine (probably a Jabiru 3300  would be a good proposition). Below are a couple of photos of the metal pieces I have managed to create so far. (April 2002)

 A selection of metal pieces - aileron hinge parts and the flat pieces for a dual control stick setup
 The elevator control horn - I intend to connect pushrods instead of cables for elevator control
 A selection of metal pieces - main gear brackets, wheel allignment shims and parts for the nose leg structure
 A drawing based on Stan McLeod's notes for control sticks ahead of the spar
 Continued details of my control stick setup and behind the spar mounting bracket

I plan to mount my control sticks behind the spar instead of in front of the spar. There are several reasons for this. I want the feel of the controls to be the same on both pilot and passenger side. Where the controls are hinged in the middle, like in many Jodels and the earlier Cavaliers, the "feel" is different from one side to the other (reversed infact). This is really only a relatively minor consideration. The revised control stick setup will also save a small amount of weight as a short length of pushrod can be eliminated along with some of the workings required for aileron control. I may well use up the weight saving by using pushrods for the ailerons. Some of the obstructions in the footwell area can be removed - less chance of that camera or something else getting tangled up at some inopportune time. My initial tests suggest that I will not have to make radio calls in a high voice on climbout. I may have to change the elevator horn shown in the diagram to on top of the outer tube depending on how the bellcrank is arranged further back.


I had major problems getting the corect width steel for the main gear legs. I could get any spring steel I wanted as long as it wasn't over 4" wide or I wnted 6 Tonne of the stuff. Great!!! Nobody around here had any knowledge of how to make fibreglass gear legs so I travelled to mainland Australia to go around a few aircraft wreckers to look for, say, Grumman Lynx legs or anything that might be made to fit. I did find some Cessna 150 main legs for about $1,500.00, but they were deemed expensive and not particularly suuitable. A friend even researched possible sources of steel in the US when he travelled there for his work, but to no avail. I found some steel eventually in Melbourne at a spring works auction so I asked my brother who lives nearby to go and get me some ...and as Murphy was in attendance yet again, my brother arrived just after they had sold all the steel and were starting to auction off the machinery. I can hardly describe my despair at that time as I had been looking for the material for so long only to have the first sight of success evaporate.

I even contacted a well known spring works in Tasmania to get my "awning brackets" machined and heat treated. I got the proverbial run-around for several months. Then I thought that a proper aircraft engineering firm may be a better choice to get my gear underway so I contacted an aerospace engineering company to build me some gear legs, but the circles became even more viscious and the whole process was infuriating. However, all was not lost. As I continued searching, I came accross a spring works in South Australia, Industrial Engineers and Spring Makers  and they had just what I wanted. Apparently Industrial Engineers and Spring Makers import materials for Cavalier landing gear legs to use in their manufacture of springs and towing apparatus. They were very helpful to me and were happy to supply me with a couple of 1m lengths of 5" wide spring steel, a 1m length or so of 1" round bar and enough steel for the nose leg fork. Brilliant!! Truely a pleasure to deal with.

 The long awaited steel finally arrived in July 2004

I have researched a few cutting methods like laser cutting and plasama cutting in a water bath (as well as water jet cutting not available here until very recently). Anything with heat involved will most likely produce a heat effected area in the steel of 1mm or more that has to be removed before bending etc, so these methods seem to be out of the question. After all the trouble getting the steel and trying to find someone who could cut it I decided that I must return to my original philosophy which is "Do it yourself, because nobody else will do it yourself". I found a slightly damaged metal cutting bandsaw at the local second hand store and set about doing a few repairs, putting the saw back together and building a foor stand for it. I have some good quality bi-metal blades and a small stack of 5160 steel so let the chips fly!

UPDATE!!!! (25 April 2009)

 Finally made a small amount of progress by making a pattern for the main gear leg
 After 45 to 50 minutes of sawing!
 After another 55 minutes or so of sawing!
 Both main gear legs cut out and ready for grinding, filing etc
 A selection of metal pieces - main gear brackets, wheel allignment shims and parts for the nose leg structure

The second leg only took 60 minutes to cut out. If I had to do a few more I could get the time down a bit further! Now I have to trim the legs to final shape, round off the edges, drill a few holes, bend to shape and try to find someone who will heat treat them!

The 5160 seems to cut fairly well using the medium speed setting (120 FPM). This might seem a bit fast for 5160, but I suppose that my feed rate must have matched up fairly well at that speed. A small amount of coolant/lubricant makes sure that the steel gets only just barely warm to touch. I needed a paint brush to get rid of the chips so that I could still see the lines on the steel. I re-marked the lines white as the darker colours are impossible to see through loose chips and coolant.


Continental/Rolls Royce O-200 - hotted up with electronic ignition etc - needs some more research and results will be placed here.
Well, actually, there's some good Continental engine information on the  Bowers Flybaby Page

Jabiru 3300  - 100/120 HP with a 2000 HR TBO 83.5kg (184lb) with most bits attached, but may be too light (is that really possible?). I have tried to calculate the length of the engine mount required for a Jabiru 120HP engine, but I haven't quite come to terms with weight and balance calculations yet. Maybe an extra 5 or 6 inches??


Fuel for the Cavalier is carried in wing tip tanks holding a total of around 130 litres. This gets the fuel away from the cabin and adds to the stability and probably speed of the aircraft. Ron O'Neil, the builder of VH-SLZ (also an SAAA Technical Officer) said that he had flown in Minicabs and other aircraft similar to the Cavalier (without the tip tanks). He said that the tip tanks on his Cavalier made it a far more stable aircraft and a pleasant cross-country machine in comparison When you live in Tasmania, cross-country and cross-water ability is important. Have a look at the map and see how much water is between Tasmania and mainland Australia - 240km or 150 miles. If you set off in your Cessna 150 from North West Tasmania and head North West or North East for an island (to give yourself a false sense of security about being close to land) on the way to Melbourne in Victoria, you will be in the air for around 2 1/2 hours. A nice comfortable window seat in an aircraft that you don't have to fight is real handy and then you can sit back, relax and admire the view.

Stan McLeod has designed a new style of tanks that were included in his latest plans. These tanks are slightly larger by my estimation and have and upturned fairing on the outboard edge. There are some photos on the Cavalier-and-Jungster Newsgroup  if you are interested. I'm not sure how much drag reduction would be involved in the new style tanks over the old, but the extra bit of fuel might just be enough to get you over the fence. I have heard reports of similar upturned fairings/winglets being added to other aircraft and it has resulted in a decrease in roll rate, a slughtly reduced stall speed, an overall increase in stability, but no significant increase in cruise speed. Stan suggests that the new style tanks should be easier to build, have less drag and look better. Obviously beauty is in the eye of the beholder and I quite like the look of the old style tanks.

Stan McLeod (the designer) has listed the reasons for his inclusion of tip tanks in his Cavalier designs below:

1) Improved lateral stability
2) Reduced drag, increased lift - higher cruise, lower stall
3) Safer due to fuel removed from cockpit
4) More cockpit room due to #3 above
5) Increased aircraft strength due to better load distribution
Instead of all the weight being in the center of the wing, trying to break the wing in 1/2, the weight is distributed more evenly with the fuel on the tips. Visualize a weight in the center of a stick bending the center  "down" and the ends "up" (center of the fuselage down and wing tips up). The aircraft is actually stronger with tanks full rather than empty. It's interesting that most airliners have fuel all over the place but they use the tip fuel last in order to maintain weight distribution.
6) Nicer/modern appearance

 Suggested fuel management procedures (for your operations manual)

My tank plug as it stands is for the old style tanks and my intention was to use it as a male mold. However, I am now planning to extend the outboard edge of the plug as per the new style tanks, but without the upturned fairing. That way I can make two tanks or two molds from the one plug and add the fairing later. I'll probably get ssome flack, but I'm tempted to leave the fairing off ...we'll see, I haven't decided yet.

 Tip Tank plug under construction
 Tip Tank plug (2 halves) completed and ready for modification (again!)
 Tip Tank plug under modification - no new pictures yet


Due to the price and availability of Spruce in Australia, I have used Douglas Fir (Oregon) instead of Sitka Spruce to build my main spar along with the rest of the wing structure. I made some initial calculations to try and work out how much heavier the wing would be as a result of choosing heavier timber, originally intended to be Hoop Pine, and since Douglas Fir has a similar density of 520 kg/m3, the results should also be similar. I have not reduced the size of any of the wing components to compensate for Douglas Fir being slightly stronger than Sitka Spruce, choosing to accept the weight penalty and not get too confused with a heap of new measurements.

Below I have some weights of some of my wing components.

The weight of the main spar (front and rear shear webs in place and inside rear of spar coated with spar varnish) - 24kg (52.8lb)
A small amount of weight will go once the spar is trimmed to the shape of the ribs. For comparison, Stan Mcleod said that his Spuce spar weighed 49lbs.

Hardwood blocks built into the spar
Landing gear attach blocks - 1250g and 1260g
Wing attach blocks including diaphrams - 482g and 475g
Centre Block excluding diaphrams - 525g
Rudder cable blocks (added next to centre block for use of Cessna pedals) - 82g and 82g

Original panel bow (Spruce) - 162g
Replacement bow (including small ply shims needed to fit to existing structure) - 217g
The replacement bow is slightly larger being 20mm wide instead of 18mm and is 11mm taller - weight gain 55g.

I remade my aileron spars to correct an error in the taper and slight bow in the original spruce ones - weight gain 130g.
Original aileron spars (Spruce) - 790g
Replacement Douglas Fir spars - 920g

Rear Spars (tapered for scarf joint to centre spar) - 1403g and 1382g
Drag Spars - 715g and 746g
Centre Spar - 1872g

Rear Wing Ribs (0-6 Hoop Pine ply & 7-10 Coachwood Ply)

Rib 0 - 507g
Rib 1 - 348g
Rib 2 - 253g
Rib 3 - 263g
Rib 4 - 203g
Rib 5 - 240g
Rib 6 - 209g
Rib 7 - 132g
Rib 8 - 130g
Rib 9 - 133g
Rib 10 - 125g

It looks like Douglas Fir is 10% to 15% heavier than spruce in this case and should create only a small weight penalty, especially since I'm only using it for the wing.

Main Gear before cutting out: 1m of 5" X 1/2" 5160 Spring Steel - 12.4kg
After cutting out the first leg, no holes or rounded edges - 8.0kg
Looks like about 50% heavier than commercial aluminium legs which are listed at 11.4kg (25lb) a pair. These are 1" thick though and so have twice the frontal area. That's an extra 155 cm2 (about 24 square inches).


Some test joints I have made using FGI ES180 epoxy and some other miscellaneous jigs & tools:

 Test joint #1 - Douglas Fir
 Test joint #2 - Douglas Fir
 Test joint #3 - Part of a gluing ability assessment test
 My home made ply scarfing sander with tilting table
 Metal Cutting Bandsaw - picture here soon


The beginnings of a Comm antenna the plans of which appeared in a Kitplanes Magazine article a few years ago. This was made for a friend's metal aircraft. I intend to do a similar thing for my Cavalier, only the antenna will be embedded in the tail fin:

 Balsa core - side view
 Balsa core - end view
 Balsa core with copper tape added
 Closer view of the core and copper tape
 The core and tape covered with fibreglass and epoxy
 The radio end of the antenna ready to fit the base and BNC connection

Theoretically, copper tape of the correct length could be fitted to the ply on the leading edge of the tail fin to make a good low drag antenna. Of course, a ground plane of some sort would most likely need to be fitted under the antenna and any metallic finishes kept well away from the area surrounding the antenna (eg. some fabric finishes may contain metallic substances). RST Engineering. has some information about this sort of antenna and a heap of experience in getting such things to work correctly.

I am currently working on a bent half wave dipole antenna design. The intention is to be able to make the antenna from copper tape similar to the one above so that it will be light weight. Being "bent", a full half wave could be fitted inside the tail of the aircraft or inside the aft fuselage and the longer antenna, compared to the usual quarter wave whip, should give better transmission and reception.

 The beginings of a bent dipole antenna prototype - weight of parts 50 grams

It is intended that the final antenna will be covered in a layer or two of fibreglass for support and to provide some mounting points. From the size that I have made this one, it will not fit inside the tail fin of a Cavalier. In order to do that, I would need to make the antenna a bit more rectangular in shape.

A friend has come up with a great design for a half wave vertical end-fed dipole antenna. His prototype weighs 44 grams all up. This antenna is omnidirectional and could be happliy mounted on the leading edge of the tail fin for a "no drag" installation. Having the antenna back there also insulates the occupants and instruments etc a bit form electromagnetic radiation. I will post some details of this antenna here soon.

 Coil for the SL No-drag, extremely light weight aircraft Comm antenna


17 April 2009 - Due to an excess of work to try and get through along with a series of family and personal health issues over the last couple of years, my progress on the Cavalier has been virtually non-existent. Every now and then someone emails me with a question or comment which prompts me to get the plans out think about the next step I need to take. I certainly haven't lost interest, rather I am frustrated at the lack of progress on this project along with a couple of other projects. While I was being frustrated with my inability to get any steel for the landing gear (not much point in continuing the build without the prospect of getting any landing gear) I did manage to build a small plywood boat  and there is another big fibreglass one on the way, but progress on that too has fallen victim to all those problems.

Do you reckon these things could fly? Have a look at a couple of aircraft register searches I found. Apparently there are quite a few Cavaliers of various denominatons registered all over the world and the proof is here at Airport-Data Cavalier 102.5s  and here at Airport-Data Cavalier SA102.5s

To learn about the history of the Cavalier 102.5 and its development, please visit my History Page

To see how other Cavalier builders are going, take a look at the pictures on The Builder's Photos Page

Do you like the Cavalier picture at the top of this page? Well, David Melby (the builder of that aircraft) is building another one! Have a look at his great construction pictures, hints and tips at Building the Cavalier 102.5

To see what can happen to you if you don't get out enough, or if you need a distraction, go Garage Flying

To find out about some other Cavalier builders and owners around the world or where to get plans, please visit the Cavalier Home Page

There's a heap of very useful homebuilt aircraft infromation on Ron Wanttaja's Sea and Sky Aviation Page


There is now a discussion group for Cavalier & Jungster Builders!
The group has been established for sharing information between builders, builders questions, material sources and qualities for the SA102 to 104 Cavaliers, Super Cavalier, Jungster 1 biplane and Jungster 11 monoplane.

Visit the Google Group now at Cavalier-and-Jungster.


This page will be updated with pictures and information regarding the construction of my SA102.5 Cavalier regularly/irregularly as time and photos permit. In the meantime, if you have some helpful hints or some Cavalier photos I could use, please don't hesitate to email them to me at


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