In reading about wing spar stress (specifically "bending moments") I read the statement below referring to the diminishing bending moment of different wing planforms:
"....a wing needs to be twice as strong at the root as it is at 1/3 the distance from root to tip. The outer half need only be half as strong as it is at 1/3 the halfspan. And these ratios are basically the same for all planforms. The bending moment at the root is four times greater than at midspan. Making the wing twice as strong at the root than at midspan is not enough. It will still break at the root, before it breaks at midspan"****
I understand the principle being discussed here but I cannot make the math work to verify this statement although I did discuss it with an engineer friend who stated he thought it sounded plausible. It seems to me that the diminishing bending moment progressing outward from the root would diminish less than stated above; does the issue lie in how the load in calculating how the load is distributed down the wing???
For those who know something about this, any light you can shed on the statement above would be greatly appreciated! The ramifications of this statement are very important when building a spar of adequate strength without excessive weight.
****Bending-Moments
"....a wing needs to be twice as strong at the root as it is at 1/3 the distance from root to tip. The outer half need only be half as strong as it is at 1/3 the halfspan. And these ratios are basically the same for all planforms. The bending moment at the root is four times greater than at midspan. Making the wing twice as strong at the root than at midspan is not enough. It will still break at the root, before it breaks at midspan"****
I understand the principle being discussed here but I cannot make the math work to verify this statement although I did discuss it with an engineer friend who stated he thought it sounded plausible. It seems to me that the diminishing bending moment progressing outward from the root would diminish less than stated above; does the issue lie in how the load in calculating how the load is distributed down the wing???
For those who know something about this, any light you can shed on the statement above would be greatly appreciated! The ramifications of this statement are very important when building a spar of adequate strength without excessive weight.
****Bending-Moments
