ORIGINAL: GaryHarris
Well I just learned something new and it makes sense. in a way. I always used an iron, tacked down the ribs and did most of my shrinking with an iron and pretty much only used the gun for open spaces that the iron couldn't reach . I would like to hear more as to why using my method is different and adds less torsional integrity. Of course I'm probably wrong, but I'm thinking that tacking down the perimeters and not distributing the load , you would be using less of a "point to point" contact area increasing more wing warpage as in increasing the bending moment created. Sort of like torquing down the head bolts of a cars engine head.
I don't see much of a problem with your technique Gary, if I understood it right. Do you or do you not make sure that iron on covering is firmly attached to the ribs? If yes, it's as strong and rigid as it's gonna get.
Iron on coverings are often polyesters (Mylar is one type). They are usually tensilized which means they are oriented or stretched to add strength and stiffness and also allow them to shrink back when reheated.
Stiffness is a property of any material; it governs things like torsional rigidity. It's a measure of how far some thickness-width-length of something will deflect under a load applied at some distance away (a moment arm). It's an "intrinsic" property. That basically means that stiffness is the same regardless of whether the material is 1" long of 10" long....The 1" long piece takes more force to move than the 10" piece, true enough, but when you normalize for the moment arm, the stiffness is constant
A wing that has closely spaced ribs that has full and good contact with the covering, will have greater torsional strength than one with ribs wider. If the covering is not adhered, then it's like having a long piece of covering...ie- it takes less force to move it. It is really that simple.
Similarly, a surface that has fully adhered covering will be stiffer and stronger in torsion than one where only the perimeter was adhered. The point folks may be missing is that coverings provide the best stiffness and torsional rigidity when fully adhered to a solid surface because they are not allowed to move independently of that surface- ie- there isminimal moment arm
Apologies in advance for the Physics lesson and hopefully it makes sense to you folks