Scale – Aubert PA-20 Cigale

Summary: PA-20 Thoughts, Prototype Flights, Scale Documentation, Short Kit Link, Photos, Videos

I’ve known about the Aubert PA-20 for several years as my friend, Winn Moore, built one from Mike Nassise’s plan.  That was a smaller span, maybe 20″.  It was a pretty decent flyer.  But I started to take it seriously after several years of watching Pat Murray do very well in Simple Scale and Golden Age Monoplane.  It became apparent that these plane MUST be able to score two minutes virtually every time they fly as these events are “total-of-three-flights”.

I started thinking – you know what else needs to fly two minutes every time?  2-Bit models.  These are small “commercial” Old Timers:  generally high wing and ROG capable.  What if I was able to design/build/fly a Scale High Wing Cabin model with similar dimensions to a OT Commercial model?  One of my favorite Old Timers is the Jimmie Allen Sky Raider; a 26″ span model with about 100 square inches of wing area.  They fly very well.

I began to seriously investigate this after the 2023 flying season – I needed to find a very simple High Wing Cabin with just the right proportions.  That’s when I recalled the Aubert PA-20.  I did some calculations and it turned out that it is very close to the proportions of the Sky Raider.  At the same 26″ span, it is virtually the same!  And, it has slab sides, an inline nose, a straight wing, simple landing gear, and NO wheelpants and NO STRUTS!  So, it was off to the drawing board (virtual, of course; a CAD drawing board).

I looked at the Nassise plan; I looked at the Walt Mooney plan (Peanut – Feb ’75 Model Builder), and I looked at the real plane specs (May ’38 L’Aerophile).  And I looked at what photos I could find online.  Most of the photos that turned up were of later versions:  the PA-201 and PA-204.  These were rather successful post-war models and for a short time, I toyed with the idea of developing one plan that covered most of the versions, but it turned out there were just too many changes made post war.  I would stick with the pre-war one-off PA-20.  This could do double-duty in Simple Scale and Golden Age Monoplane.

I drew up the plans over winter and cut the prototype short kit at the end of March.  It took way too long to finish the plane, but it was done in the middle of May, ready to fly.  On a breezy day, I took it into my back yard and purposefully under powered it with a single loop of 1/4″ rubber – just something to do my traditional low power testing for glide and cruise.  with a small tweak tot he tail and to the thrust – but no nose or tail weight – I had it cruising around the back yard on very minimal turns – 100-120 hand turns.  From these very low-powered flights, I could tell this was going to be a flyer.

Two days later, the weather was projected to be perfect at our local flying field, so Winn and I went up there for a day of testing.  We were not disappointed!  The weather was, indeed perfect:  low 70s temps and virtually no wind; only very light shifting breezes.  I made a motor from 1/16″ rubber – 5 loops – just one (standard) increment above the 1/4″ test motor.  With a small lump of clay installed in the nose, I was rewarded with wonderful flights.  I was getting about 1:20 on 1200 turns.  Later, I switched to a 24″ motor from two loops of 3/16″ (one more standard increment increase).  The best flight I recorded was a 1:40 flight on a 1:30 DT.  That is, it took about 8-10 seconds to land after the DT went off.  (My self-timing methodology:  1- Start DT, 2- Launch, 3- Start watch.  Launch takes place about 2 seconds after starting the DT, the watch starts about 2 seconds after the launch.  The watch said 1:38, so it was probably a 1:40 flight.)

This model seems to be ready for the task.  A couple more tweaks to the motor length and I should have a contender.  This just might work out!

SCALE DOCUMENTATION
There is very little documentation for this pre-war model.  There is a one-page contemporary write-up in the French publication L’Aerophile (May 1938).  This has a 3/4 front view included (shown below) and basic dimensions and a lot of French text that I didn’t bother to try to translate.  Write-ups like this rarely have color information, so that is unknown.  I was able to find one more contemporary photo with a young lady standing next to the plane.  Of course, it is in black and white, also.  But both photos look to be of a light color.  Mike Nassise’s plan specifies yellow, but also is careful to say it is of no known aircraft.  Any contemporary light color should suffice for your scale work.  I used a light cream domestic tissue and printed details in black.

The registration number shown on my model and on the plan is accurate.  How do I know?  Well, the number is reported here:  http://www.airhistory.org.uk/gy/reg_F-24.html  Scroll down to the bottom (or do a search on the page for Aubert) and you will find the PA-20 and registration number.  There was only one PA-20, so this is it.  The color of the registration number is not known.

For the style of the registration number I relied on photos of the PA-201 and PA-204; the post-war resurrection of the design.  There are at least two different aircraft with the registration number in an outline style, so I used that.

Fin Details – there is a photo of PA-201 No. 1 showing the tail.  I have replicated that layout on my plan.  This includes the wing logo design that was recreated for me by Mike Smith.

(short kit available HERE)

Here are some photos and videos.

pre-production plan and wood

nose sheeted with 1/64″ balsa

from May 1938 L’Aerophile

laminated tail outline with multiple spars for DT hinge at scale elevator location

showing peak on top of fuselage at wing trailing edge

showing top peak onto rear of wing

wing center section in place showing fuselage peak transitioning onto wing, diagonals are for tissue anchoring.

rough assembly

noseblock with 3D printed “breakaway” prop, 3D printed hub, and 3D printed spinner encasing a modified Nason clutch.

BMK Band Burner DT installation

showing the model and original PA-20

all-up weight without rubber (DT installed)