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

Avions Claude Piel, CP1315 CP1310 CP320 Super Emeraude, CP30 Emeraude, CP80, CP1320 Saphir, CP70 Beryl, CP60 Diamant, ML250 Rubis
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 Sujet du message: Building a Super Diamante without flaps
MessagePosté: Sam 22 Sep, 2012 11:40 pm 
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Inscription: Jeu 14 Avr, 2011 10:17 am
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Localisation: Maraetai Beach, New Zealand
Hi Everyone,

I have just read an article in the EAA magazine from many years ago, where an Emeraude builder discussed the option of building his Emeraude without flaps. Evidently the plans gave him a choice - flaps or not.

As the Diamante is basically a scaled-up version of the Emeraude wing I can see no reason why I couldn't build my Diamante without flaps.


1 - Easier.
2 - Quicker.
3 - Less weight.
4 - Cheaper.
5 - Less mechanical fittings to malfunction.
6 - Fewer parts to check and maintain.
7 - Reduced risk of passengers standing on flaps that were not designed to take their weight.
8 - A stronger wing structure.

I could think of a few more, but you get the idea.

As for flight characteristics - I would anticipate no change to either the take-off, climb or cruise handling.

As for stall speed, there appears to be only approximately 5 mph difference in stall between flaps up and flaps down speeds. This is not significant in this class of aircraft.

As for the approach speeds, I would anticipate very little difference, maybe a little more of a 'float time' in the round-out and touchdown but not very different.

Over the years I have flown many types of light aircraft both fitted with flaps and without flaps. For example the Piper Cub has many models with and without flaps and they all basically handle the same with no major differences or problems.

Yes, of course I would probably need to maintain my proficiency at side-slipping but this is the way I learned many years ago and it would present no problem. As an instructor I have been surprised by the number of modern-trained pilots who have never been taught how to side-slip and this makes me sad - after all you never can tell when this skill might come in handy.

I am aware that the use of flaps will allow me to descend at a steeper angle and at a slightly slower approach speed into a runway with obstacles to clear on the approach, but I reason that for this to be required it would mean that I was attempting to land at a pretty short airfield, given the excellent short-field performance figures published for the Diamante, so why would I (not being insane) want to land at such a short runway anyway?

I would be interested to know if the Diamante has ever been built without flaps? Are flapless plans available?

Also would be keen to hear anyone's views on this subject.



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 Sujet du message: Re: Building a Super Diamante without flaps
MessagePosté: Lun 24 Sep, 2012 2:01 pm 
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Inscription: Mer 29 Juin, 2005 2:15 pm
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Hi Barry,

Obviously the Diamant cruises and handles very well with the flaps at 0 degrees, and would do as well or possibly even better with no flaps at all (cleaner wing profile and thus less drag).

You listed some advantages, and I agree with you on these points. I would rather try to list the disadvantages of the absence of flaps to check if one of these reasons is important in your own case.

1 – Higher stalling speed.
2 – Higher approach speed.
3 – Flatter maximum approach slope.
4 – Higher landing speed.
5 – Higher take-off speed.

Number one and two are not a problem from my point of view. A higher approach speed can be seen as a rather a good thing on very crowded airfield…

Depending on the airfields to land on, number three can be very annoying. Some airplanes operated in mountains have no flaps but they are specially fitted with airbrakes… Some of them of very simple design are very effective. The landing speed is not reduced, but the airbrakes can lower L/D ratio at approach speed down to about 3, and retracted anytime when needed…

Number four means stronger undercarriage to survive to faster speeds on bumps, stronger brakes and/or longer runways. Not really a problem on a large nice airfield.

Number five means stronger undercarriage to survive to faster speeds on bumps, more powerful engine and/or longer runways. Again, this may not be a real problem on a large nice airfield.

However, the Diamant is designed to fulfill the French amateur built aircraft regulation (CNRA) and this regulation imposes the aircraft to demonstrate its ablility to fly over a 15 m (50ft) obstacle situated at 600 m (2000 ft) from the rolling start point.
On grass runway, at MTOW, with the less powerful engine recommended, a long pitch propeller designed for cruise and no wind, flaps may reveal quite useful. Of course, if the regulation that your own plane has to comply with is not so demanding on that point, no flaps can be a good solution.
As far as you maintain your proficiency at side-slipping, you shouldn’t need to add airbrakes.

I don’t to know if the Diamant has ever been built without flaps… and if flapless plans are available. Jean-Claude Piel (BIG) should be able to answer this question.

Philippe Dejean

Les fourmis sont des guêpes comme les autres !

 Sujet du message: Re: Building a Super Diamante without flaps
MessagePosté: Lun 24 Sep, 2012 10:49 pm 
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Inscription: Jeu 14 Avr, 2011 10:17 am
Messages: 19
Localisation: Maraetai Beach, New Zealand
Hello Philippe,

Thank you for your reply.

Yes I agree with your comments. I will explain further some points. I want to use the Diamant as a 2 x seat touring machine with a good economical cruise, but able to operate from most airfields around New Zealand. The normal minimum runway length of licensed airfields here is 2000 feet. If I was planning on a fishing or hunting trip in the mountains I would either get a professional to take me in or would hire a Cessna 185 or DH Beaver myself and not use the Diamant. Although there is not much chance of this because my hunting days are probably over as I leave it to my younger son to provide us with venison or wild pork.

I have decided to use a Lycoming 0-320 of 160hp. Also I intend to make a smooth, more streamlined nose cowling complete with simple manual cowl flaps to help control low-speed cooling. The propellor will be a Catto composite prop, 3-bladed with a pitch setting (fixed pitch) of a good compromise between fine and coarse setting (an all-round performing medium range pitch). My research has shown that this engine power and propellor combination will be very suitable for an aircraft in the Diamant's speed and weight operating range and I do not want to go to the extra trouble, weight or cost of a CSU prop.

I have considered fitting either air brakes or spoilers (like a glider) but these features would mean further modification and weight, which is something I am trying to avoid, although spoilers would be both simple and attractive.

In short - I am looking for a strong, simple to operate 2 seat touring machine with good capacity for baggage, tent, picnic hamper (we have lots of nice beach airfields in NZ).

Yes, I believe the approach without flaps will be at a higher speed, but not much higher. Also to clear an obstacle on the approach I would sideslip (as you pointed out). As for take-off, with an engine of 160hp and a good power to weight ratio it should get off the ground quite quickly.

Your point of the cleaner wing profile and less drag from a flapless wing is well taken, and this aspect appeals to me, plus the opportunity to make the inboard area of the wing stronger by longer ribs and ply covering top and bottom. I could also increase the chord of the full-length ribs nearer the fuselage slightly to enhance the curve of the outer wing/aileron lines. This would also look more pleasing to the eye as an attractive elliptical shape, which improves the drag management of the wing.

I will draw a sketch of what I am proposing and do what you say - ask Jean-Claude for his comments.

Thank you for your help,


Barry G

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