I just bought a Phoenix Aircraft Models CAP 232-40. The reason I bought it is that it seemed a nice kit and the all up weight claimed in the box was 1600g. I thought it was a very light model and that maybe it would be worth trying an electric conversion so I bought it. When it arrived home I inmediately saw that the weight would never come close to what they said so I decided to go the glow power way. The kit is of decent quality and it really needs little work to assemble meaning that you can do very little to add weight. I have it now with the motor mounted (an OS 46 FX) and it weights 2100g. To this weight I have to add all servos (5 servos) and hardware related (pushrods,links,etc..) receiver and battery pack to complete the model so I think that the model will finally go to 2400g if I use a light pack. This is 800g more than what the manufacturer says, 33% more. I am not saying that this model is not going to fly right, because it is a decent final weight and I know I can use a smaller motor, I can use micro servos and receiver, but it is impossible to get near the 1600g. Why do some manufacturers lye in their specifications?

I said 33% and it is 50% more than claimed.

Where did you buy it? I was looking to buy one but can't find a place that sells it in the States.

Sorry I can´t help you. I am from Spain.

May help us if you convert the "G" to "US"

>Just the ones who can't do simple conversion math.

Mfr's all lie. Do you really think you can produce the HP that OS claims with their engines? Uh, no. It's just an unfortunate side effect of competition that people start stretching the truth in their adds because the other guy did, then they did, then the other guy did, then they did... Pretty soon you have a Piper cub that does 200 mph( 322 kph).

Converting grams to U.S. pounds
1600g x .0022 = 3.52 lbs.

Actually, technically they wouldn't be lying. If you leave it in the box and toss it over a cliff, I'm sure the terminal velocity would reach 200mph.

Manufacturer don't lie, they merely deceive, enveigle and obfuscate.

28.35 grams = 1 ounce

454 grams = 1 pound

Good morning all and welcome Joan, to RCU.


First, let me say that many Mfg's weight claim is a best case scenario. Perhaps the first scratch built prototype came in at that approx. weight using hand picked balsa. (OK, a stretch perhaps but benefit of the doubt).

Then you contract a builder in Viet Nam to build the model for export.
It is becoming well known that Viet Nam has no balsa, or a very heavy cross breed of it. Then instead of light ply you get laminated mahogany, also much heavier. Combine this with hardware that is heavy too, and mostly un usable, and a glue that looks like hot glue, and heavy.

The point is I can see how the weight can just balloon up if left to chance. I'm sure the importer/designer asked the company in Viet Nam what the approx weight would be, and they were lied to.
This is a very common occurrence in the East, where you are told what you want to hear, by a very large majority of business's.


Phoenix, J-Mar, are both equally consistent in producing products that are inferior and over weight, but value priced.

Clearly we can and have voted with our wallets and demanded better quality.
From the looks of the quality of the new breed of ARFS, example, Hangar 9, Yellow Aircraft, World Models and Morris to name a few, we modelers have changed the face of RC today. Due in large part to bulletin boards such as RCU and others where manufactures are bombarded with instantaneous product reviews and real life flight tests.

So in closing Joan, it is very rare to see a completed aircraft come out at or near mfg's recommended weight.

There is though, light at the end of the tunnel. Electric aircraft are so weight critical that manufactures have done a much better job of advertising more accurate weight info, and then reaching it. Electric modelers have from the beginning demanded it, and voted with their dollars very quickly, forcing mfgs to fix it or discontinue it.

OK, sorry 'bout the diatribe, good luck to you and the Cap.

It is normal in some parts of the world to list the weight of the completed airplane excluding anything that doesn't come in the kit. In other words, the weight listed for the completed model does not include the engine, prop, servos, receiver, switch or battery.

Since the engine,prop and radio for a 40 size airplane would weigh about 800 grams (28.2 oz.), the weight stated for your kit sounds pretty accurate, given the standard they used .

How do you know which standard they used, ready to fly weight or bare airframe weight? Well, if a 40 sized CAP ARF weighed 3.5 pounds ready to fly, with 1.75 pounds of engine and radio included, it would have to be filled with helium!

This is not saying that ARFs don't frequently come out heavier than the advertised weight. They do, but not 50%. Or even 33%. Come on guys, if it sounds too good to be true...

Jim

I'm with you JRF. I bet the weight of the airframe with no equipment is 1600 grams. Which is pretty light! It IS too good to be true that a .40 size airplane with engine and radio weighs 1600 grams. Unless it's made from..well I can't even think of a material light enough to come out at 1600 grams ready to fly on a plane this size. Let the buyer be ware especially when dealing with not so well known companys.

They could also blame it on typographical errors. Many imported plans/instruction manuals/box lables are filled with errors...always have and always will. And they could be lying, but I doubt it.

Yak

Just for your info you will also find that the wing area is often wrong. It's not because they are lying they just figure it different. Here in the US wing area is main wing only but in some contries it includes the area of the tail. Also when they do the area its MAC x span and they sometimes do not subtract the area of the fuse.

Is it not true that in this country it is the projected wing area and includes the area where it passed through the fuse?

RCPAUL

The most common way to figure wing area is to add the root chord to the tip chord then multiply that by the distance from the fuselage side to the last rib. If you include the fuselage area the number may not even be close, for example my heilo stallion has a wing chord of 16-inches and the fuse is 11 inches wide thats 176 square inches that doesn't lift anything. If I used the SAME WING PANELS on a fuselage only 5 inches wide would I have less wing area?

The best way to measure wing area - that is the most accurate way to find lifting area on virtually any airplane, is to include the area that passes thru the fuselage. It does not matter that there is no wing-shapped cross section there.

The plain fact is - wings create a low-pressure zone above them. This low pressure zone overlaps onto the fuselage with an intensity amazingly close to the pressure value that would exist if there were just a plain wing there. It is generally within a 10% difference. This can be verified by wind tunnel tests, flight tests, or just comparing computations based on wing area to actual performance

When figuring total wing lift, a difference from perfect wing lift of 10% over say 10% of the wing area( the part "in the fuselage") results in a total lift difference from actual lift of 1% (10% x 10% = 1%).

Compare this to ignoring the wing area "in the fuselage" You ignore all the lift that is really there (90% of lift a wing "would" give". Thats a 9% difference in lift from what a plain wing would do(90% x 10% = 9%).

When evaluating a plane - a 1% difference can be ignored for initial evaluation, a 9% difference you ignore at much greater risk - and error. The method that outcast gives is neither the most common or the most accurate. Anyone who designs airplanes seriously - from BVM to Boeing - understands this.

Anymore of this should be taken over to the aero forum.

Sorry gotta disagree, not all fuse designs create lift. Also from what I remember from my fluid dynamics classes {granted it was back in the 70's} the shape of the junction at the wing intersection as well as the location of the wing all affect lift performance. As speed increases compressability becomes a factor, as well as the need to maintain a laminar boundary layer over its surface. But hey thats what makes this fun.

What you say about wing fuse interference is true - and those things account in part for the 10% variance in pressure I mentioned. That does not justify ignoring the low pressure that is experienced by the fuselage and the resulting lift.

It does not mean that the pressure values jump from a lifting low-pressure over the wing to some higher value right at the wing root and across the fuse. Pressure fields are omnidirectional and tend to equalize between different pressures. Think about it, if there were high pressure over the cockpit of your given plane and low pressure over the wing right next to it, the flow would tend to adjust and equalize with a local airflow component moving away from the fuselage- and you'd end up with very similar pressures over wing and fuse.

If I'm wrong, how do you explain the fact that calculations of performance using my method for wing area turn out to be so accurate on virtually everything flying?

Not only isn't a laminar boundary layer necessary, it isn't a factor on almost any model much bigger or faster than a 2m glider. On models, laminar flow is generally a bad thing, as laminar flow stalls sooner and creates more drag than turbulent flow at this scale.

Compressibility isn't even relevant, although planes designed for it, say the F-16, show how well the lift distribution continues over the fusalage.

It really is a discussion for the aero forum, so I'll quit this thread. If anyone wishes to discuss further, go post in the aero forum.

JRF,

It is right that the box simply says weight. It does not say weight ready to fly, but I have not seen any other kit that is only putting the weight of the hardware supplied.

The weight of the hardware supplied is of approximately 1800g. I have not installed the wheel pants that seemed really heavy(80 g) and have changed some hardware to reduce weight. I will finish it next week and will post the final weight.

Joan:

You'll find that many oriental kits designed for the home market are listed that way. Here in the US, I notice that many of the Kyosho kits list airframe only weights.

Jim