Practical vs realistic weight question
 

here is a question for the gallery. I have noticed and watched quite a few of the larger planes ...mostly warbirds, fly on Utube. What has become obvious to me is that the planes are lighter than they need be. Watching the B1 Bomber build here, the builder wants the weight so that the plane is not a floater or doesn't get pushed around . What are your thoughts on this?Are we as builders of these larger planes lost in the past or subscribe to old theory that lighter is better when it comes to our larger "Non-3D" airplanes.

RE: Practical vs realistic weight question
 

i flew a 1/3 sopwith pup for years, hardy able to fly it at 31 lbs if there was much wind, once i got the weight up to 37 lbs was able to fly in 25 mph winds with no problem

RE: Practical vs realistic weight question
 

I had a similar experience with my 22-1/2# Nosen Cub. Darn good plane that one. Was very smooth handling in a breeze. Something those 14# Cubies couldn't handle.

Bedford

RE: Practical vs realistic weight question
 

Weight is like nearly everything else in an airplane...

It's a trade off.

Change the weight, change the characteristics of the airplane.

Are we "lost in the past", or "subscribing to a modern theory"? Neither, imo. What we're doing, as builders..or at least what, imo, we SHOULD be doing..is studying, researching, and learning through experience just exactly WHAT changes with weight, and how, and why...and then building TO that understanding.

We learn, through experience, what traits we like in an aircraft....and we learn, again through experience, that our preferences may change depending upon the type of aircraft, or what we expect to do with it.

With that knowledge, we then consider wieght like any of the other eleventy-nine things we consider when building...it's an aspect of the plane that impacts the plane's behaviour...and we manage it to do the best we can to create the behaviour(s) we want in the given aircraft.

RE: Practical vs realistic weight question
 

have you seen the video of the 1/4 scale Spitfire , taking off and landing.....like a kite?I figure or speculated that a bit more weight would make that plane handle better.

RE: Practical vs realistic weight question
 

More of what you are seeing is the benefit of higher Reynolds numbers.

The Strength to weight ratio is going the wrong direction with every ounce that is added. Until high strength materials and the knowledge of how to utilize them become commonplace it is probably better for all of us to deal with the "float factor".
The 75# Super Decathlon that Ken And I are flying is a floater but it would not benefit by having a more scale wing loading.
All of this would have to be on a by case basis. I don't think that a general statement can be made about whether models need more or less weight. I just know that at my age lighter is better when it comes to handling these things.:D

RE: Practical vs realistic weight question
 

I like this thread........interesting and good stuff....Ron

RE: Practical vs realistic weight question
 

This is a really tough one for me. I do, generally, subscribe to the "lighter is better" theory (even though I don't practice it with many of my models) but there are certainly limitations and instances where it is not better. Take for instance the previously mentioned video of the 1/3 scale Spitfire. Reports would indicate, and the audio corraberates, that it was very windy that day. To my eye the airplane definitely could have benefited from more weight on that day, and maybe more power too. However, I would bet that on a calm day that airplane could emulate the full size very, very realistically. Where I live and fly we have a considerable amount of wind for much of the year so I tend to like my airplanes heavier simply because they penetrate better and, therefore, look more scale to me. However, they do have to fly faster than scale which is a sacrifice I make to better deal with the wind. It is simply my opinion that an airplane flying too fast but flying a smooth line looks more scale than one flying at a more scale speed but getting bounced all over the sky. Ideally what I would like to have is a lightly loaded model and dead calm air but how often does that happen?!!!

RE: Practical vs realistic weight question
 

a warbird that floats and bounces around just doesn't seem right. Watching the Top Gun videos it appears that many guys by choice or not are building bigger and heavier models, because they do fly better.....all except the WWI warbirds, there is no hope for them. Castle, explain higher reynolds #s and our strength to weight factor as you see it. Do you truelly see a problem with ballasting a plane?

RE: Practical vs realistic weight question
 

Reynolds numbers are dimensionless numbers that in the case of wings give a relative idea of how many molecules of a gas will react against a surface and for how long. The bigger the area and the deeper the chord give more molecules more time to react to the load applied against them ie the wing which translates to more lift for any given speed.
The Strength to weight ratio is a comparision of material density to its ability to resist a force without failure. Lead has a very low strength to weight ratio while carbon fibers have an extremely high strength to weight ratio.

As for ballast it is strictly on a case by case basis. A very large airframe built out of light ply and nothing else would be vulnerable to failure while a lite ply framework with carbon fiber bonded to it would perform at a much higher level safely.
Also fittings and other load carrying parts would have to be evaluated. Very few modelers have access to high heat treat and exotic alloys for their models. This really shows up in retracts when they are overloaded.
Having watched some heavy models fly with plywood tongue wing joiners layed flat I would not want to see an ounce of excess weight added to them. Also concentrated loads from ballast can cause localized failures. That is why we used water filled wings on full size sailplanes rather than bags of lead shot placed on the cg in the fuselage. Also it allowed for dumping the ballast prior to landing reducing the strain on the airframe and landing gear.

RE: Practical vs realistic weight question
 

One of the things I have been told (as an aspiring competition scale pilot) with the WW1 airplanes, which is what I am flying now, That many try to fly them too SLOW. The rational here is that if you keep the speed up, then you are less likely to get downgraded for eratic flight. I think in general, a WW1 aircraft is very lightly loaded so it is just the nature of the beast that they will be tougher in the wind. Although, my 1/4 scale DVII does not fly really light even though it only weighs 18#. Certainly not a floater. For as much detail I have, it is one of the lightest ones I have heard of.
My direction though now is WW2. I think just the shape of the heavy metal birds helps with smoothness for competition but as for weight, I still prefer light. I think a lighter plane will be more tolerant of a mistake and may help to make it last longer. Especially at take-off. I have seen quite a few planes lift off early and stall. Poor piloting was the fault here, but a lighter plane would have been OK.

RE: Practical vs realistic weight question
 

Castle, great explanation, thanks. When you see the build on the B1 bomber, what are your thoughts there when it comes to weight? Grimmace, now you are kinda getting into the age old argument of sclae speed. WWI wabirds are naturally draggy and with a light wing loading. Ballasting one of these birds could be bad because of the potential for structural failures. So when it comes to bigger is better and reynolds #s, is bigger better or just things happen slower and are easier to see?

RE: Practical vs realistic weight question
 

Send me the link to the B-1 build if you would please.

RE: Practical vs realistic weight question
 

http://www.rcuniverse.com/forum/m_4672497/tm.htm

sit back and get ready for a treat. At least 50 utube videos