CP 1320

[AlexZ]

Hello all,

Excuse for writing in English. My French is very limited. I'm living in the Netherlands and currently flying a Sonex.
Recently I acquired a CP1320 project that was abandoned in the 90's. The airframe was finished up to painting. It'll need some rework, but basically not too much work (haha). The controls need a good check for corrosion. It lacks all firewall forward stuff. So no engine mount, engine and cowling. I already found a good O320 to put up front. With all the Corona limitations I'm not able to pick it up myself. Transport is arranged and the project will arrive in December. So no detailed pictures yet.
In the mean time started the CAD design of the motor mount and the modification of the landing gear.


I'm looking for as much info I can get. A lot of projects are pre internet, so limited information there. Also not that many 1320's are flying. But I'm particularly interested in the F-PNAR. The photos in the gallery show a few parts I'm interested in. I tried to get i contact with Stephane Levevre through this forum, but up to now no answer. Hopefully someone knows his email address?

Alex

[AlexZ]

Made contact with Stéphane Lefevre and already had intensive email contact. Stéphane made a lot of drawings for modifications he did. Luckily for me he agreed to share them.
Last Monday (23-11) the project arrived in my workshop. First thing is to clean of the dust it collected during the years of storage.

[AlexZ]

To tackle the problem with the CG being too far aft fist thoughts where to move the wing a few cm backwards. After examining the work to be done the conclusion was that it is too much work on an existing airframe. So the airframe stays as it it is, but the engine will move 5cm forward. The design of the motor mount is made in 3D CAD.
Pour résoudre le problème avec le CG étant trop loin en arrière, pensez à faire bouger l'aile de quelques cm vers l'arrière. Après avoir examiné le travail à faire, la conclusion était que c'était trop de travail sur une cellule existante. Ainsi, la cellule reste telle qu'elle est, mais le moteur avancera de 5 cm. La conception du support moteur est réalisée en CAO 3D.


A jig has been constructed and the Dynafocal ring ordered at Aircraftspruce.
Un gabarit a été construit et l'anneau Dynafocal commandé chez Aircraftspruce.

[AlexZ]

Managed to do some FEA on the engine mount.
-6G force on the Dynafocal focus point
-Engine thrust
-Engine torque
-Propeller centrifugal moment
-P-factor

Highlighted spots have the highest stress. Maybe add some gussets there.

Basically the mount is strong enough static. A bigger risk is fatigue. Especially with a heavy 2-blade constant speed prop (Aluminum) up front. The pulsating forces from the blades are strong, especially when doing aerobatics. That's why most aerobatic aircraft's have 3-blade propellers.

[AlexZ]

Not much done the last year. Too busy with moving the company and starting up a new production.
I found an Lycoming O-360-A2A. This type has a solid crankshaft, so it will become a fixed pitch instead of a constant speed propeller.
In between the busy work I'm working on the design of the cowling. Some pictures will follow.

Pas grand chose l'année dernière. Trop occupé avec le déménagement de l'entreprise et le démarrage d'une nouvelle production.
J'ai trouvé un Lycoming O-360-A2A. Ce type a un vilebrequin solide, il deviendra donc un pas fixe au lieu d'une hélice à vitesse constante.
Entre les travaux occupés, je travaille sur la conception du capot. Quelques photos suivront.

[AlexZ]

Which cowling is the nicest? Quel capot est le plus beau ?

[Philippe Dejean]

Bonjour AlexZ,

Which cowling is the nicest ?
I think that there is no correct answer as it is mostly subjective...

The top one would be called "classic" by some people and "old fashioned" by others.

A more interesting question, to my sense, is :
"Which cowling is the most efficient accordind to the use of the airplane ?"

If you want to fly strait to some destination, the bottom one, if properly designed would be more efficient (i.e would generate less cooling drag)

If you want to fly aerobatics, that means more often "high power - low speed", the bottom one would be much more difficult to design to avoid both overheating at low speed and overcooling while cuising...

To come back to aesthetic, I would say that paint (colours and drawing) may be as important as original shape.

I know that I didn't answer your question, but I think that a very "nice" but inefficient cowling woudn't be very satifactory.

Good flights

Philippe Dejean

[AlexZ]

Well, I should have asked: Which design suits the CP1320 the most? The aircraft will be used mostly for cross country flying and sometimes a loop or roll.

[Philippe Dejean]

Hi AlexZ,

First, I will remind you a little bit of the history of Claude Piel aircrafts :

When Claude Piel designed his single seater CP20 “Pinoccio”, that first flew in 1951, he intended to make an affordable sport plane looking like the Supermarine Spitfire…
He was asked to make a two-seater version of its CP20. And that two-seater version was the CP30 “Emeraude”.
The “Emeraude” was very popular and evolved into different versions (CP301 to CP1310/CP320), but also an aerobatic version called CP100, that was later renamed CAP10A, that is the origin of the CAP10B, CAP10BK and CAP10C aerobatic aircrafts.

But about twenty years after the first CP30, Claude Piel intended to create the successor of the “Emeraude”, including a strong structure inspired from the CP100, but with much up-to-date shape inspired from its last creation: the F1 Racer base CP80.
This successor of the “Emeraude” is the CP1320.

Even if the original cowling of CP1320, looks quite classic today, I am sure that was not the intention of Claude Piel.
To my sense, the second version of cowling suits much better to the CP1320 airframe than the first more “classic” one… and corresponds better to the intention of Claude Piel to make a fast modern-looking airplane.
As “the aircraft will be used mostly for cross country flying and sometimes a loop or roll” … there is no objection to this type of design.
Of course, this opinion is not necessarily the one of the other people on this site… but it definitely mine.

Philippe Dejean

[AlexZ]

Philippe,
Thanks for your opinion. I'm aware of the history and we share the same view.
For the design I 3D scanned a Sam James cowling on a RV-7 and tried to follow the form. In the RV-7 the engine is positioned lower in the airframe, so had to adjust the shape a bit. I'll also use the air intake from James.

James-cowling-compare-3.JPG (68.1 Kio) Vu 8797 fois

[AlexZ]

To keep track of the build I created a build log. Pour garder une trace de la construction, j'ai créé un journal de construction.
https://eaabuilderslog.org/?s=CP1320