Le Forum Avions Piel, consacré aux Pierres Précieuses. Super Emeraude, Beryl, Saphir, CP80 etc .

pbuford · Posté le: Mer Mai 07, 2008 5:38 am Sujet du message: cp-1320

i'm in the us building a cp-1320 but don't speak french
have questions about aircraft
need some help with changes that i wont to make
if anyone could help you have my great thanks

cp1315 · Administrateur Inscrit le: 07 Sep 2004 Messages: 1878

pbuford · Posté le: Mer Mai 07, 2008 10:44 pm Sujet du message: cp-1320 engine and speed

has anyone put a bigger engine on like a lycoming io-360 with c/s prop
will this fly faster the the plans say

cp1315 · Administrateur Inscrit le: 07 Sep 2004 Messages: 1878

Hi pbuford

You are on a forum with a lot of people, please, if you want to receive some information, i will advice you to be a little more courteous.

Thanks

Laurent

pbuford · Posté le: Jeu Mai 08, 2008 2:05 am Sujet du message:

i'm sorry but i don't know what you mean
i just asked a question

Gregaroulettedequeue · Posté le: Jeu Mai 08, 2008 6:22 am Sujet du message:

Hi pbuford

Welcome on the forum.

What a good choice for you to build a CP1320. A long project but the plane is really wonderful.
So, about the engine, I don't know if you have the french or the canadian version, but in fact you can put on the Saphir engines from 150cv to 200cv. I only know the caracteristics of Mr Holleville's CP 1320, which have a lycoming 0-320 with 160 cv version, and it reach a good 140-145 kts at cruise speed (75% of full power). For the other version I don't know exactly which cruise speed you can reach with a 0-360 and constant speed propeller. The only one I know is Mr Casabo Saphir, Mounted with 0-360 and CS prop but I don't have his caracteristics. I will try to find information
Best regards

pbuford · Posté le: Jeu Mai 08, 2008 11:55 pm Sujet du message:

thanks for your post and efforts
my plans are canadain but there are in french
how isit to fly stall and land
phil

Philippe Dejean · Posté le: Mar Mai 13, 2008 10:56 am Sujet du message: Speed vs Power

Hello !

It is rather easy to calculate the speed with a bigger engine on a known airframe :
Provided that the propeller efficiency is supposed to be optimised for cruise, and that the cruise angle of attack is small,
A good approximation is to say that the speed varies with the cubic root of the power.

In other words if you replace a 150 HP engine by a 180 HP (+20%) you should not expect an increase of speed of more than 7%

On the other hand, the distance you can cover with the same tank is reduced by about 14%...

Just to say...

Enjoy Flying

Philippe Dejean

Philippe Dejean · Posté le: Mer Mai 14, 2008 4:12 pm Sujet du message: speed vs power #2

Hello pbuford !

Just to precise the previous message, and provided that all the problems due to the overpowering of a Saphir airframe are solved, we can calculate the following performances related to the power of the engine :

- on the left, the rated power of the engine,

- in the middle, the best possible cruising speed (no extra drag added to the first prototype) à 75% of rated power and propeller efficiency = 80%,

- On the left, the endurance with 140 litres (37 US Gallons) of AVGAS and sparing the 45 minutes for safety.

HP kt Nm
160 150 544
180 156 490
200 162 444
260 176 343
300 185 293
360 197 235
400 204 204

Of course, I would not dare mounting a IO-720 in front of a Saphir firewall without competely redesining the airplane, but this is just to show the consequences on speed and endurance :

To fly 204 NM, the 400 HP Saphir would take exactly one hour, burning 80 litres (21 USGallons) of avgas
On the same flight, the standard 160 HP Saphir would land 21 minutes later, but would have saved 9.5 USGallons of avgas...

To fly 544 NM, the standard Saphir would take 3 hours and 38 minutes
On the same distance, the 400 HP Saphir would have spared 57 minutes of flight, but would that be enough to refuel 2 times?

Conclusion : Large overpowering is not the right way to fly fast.

A much better way is :
1/ to reduce drag to the minimum (not forgetting the drag induced by the engine cooling),
2/ to reduce the mass to the minimum (better climbing rate, reduced lift incuced drag...)
3/ to keep the fuel flow as low as possible (for money of course, but also to reduce the mass of fuel to be lifted...) by choosing a low specific fuel consumption engine.
4/ to fly higher (I mean to fly at the best altitude for ground speed taking into account distance and wind, but very often that means flying at a higher altitude than usual...).

For this purpose, if I had to repower a Saphir in North America, I would choose a 200HP turbocharged Deltahawk diesel engine with a CS propeller, and design the most streamline cowling that I could...

By the encreased power 200HP instead of 160 HP, but also by the turbocharging at medium altitude (let say 8,000 to 10,000 ft) and the reduced cooling induced drag I think that a corrected speed of 180 kt at cruising altitude could be obtained without reducing endurance.

Anyway... Enjoy flying !

Philippe Dejean

Hi pbuford !

You Wrote