ORIGINAL: Ram-bro
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?
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.