Collaborative Design Challenge – Working Together to Create a Plans-Built Design

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wsimpso1

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Symetric airfoils are good for tail planes and wings of aerobats that do a lot of negative g. For airplanes that are mostly about going places and positive g's, use of foil that makes minimum drag at cruise Cl is a much better choice.

Next, I believe that a segmented wing is going to be enough heavier than a simple wing that the bigger shipping packages will be worth it. Repeat after me- Weight is the enemy. Let's take the example of a 25' span. 4' of fuselage means the sem-span skins will be 10.5', and breaking them into three pieces, means 43" segments. If the chord is 4', the wing part will be 36". So you will have 43" by 36" skins instead of 126" by 36". I just did a quick check, and you will easily add 12 pounds to the empty weight from this "short cut" alone just in extra glass in the parts and adhesive to put it together.

Next, this thought of "we can put the ribs at joints and allow us to take out some rib cap weight to make up for it idea" does not wash. Sorry, composite wing ribs don't really need any cap that you can reduce. The primary job of the ribs is to keep the top and bottom skins from going way from each other. The wing skins have enough shear load capability by themselves to transmit the aero forces to the spar if the skins will just hold shape. Well, we put in 3/8" to 1/2" cores to make the skins hold shape and may not need any ribs between root and tip. The ribs only have caps on them to attach the skins to the ribs. A fillet corner and 2" wide 2 BID tape lapping from skin onto rib on each side of each rib is customary and usually overkill, but you can not get the rib to stay put without it.

The biggest reasons to have internal ribs in a composite wing is to contain fuel/baffle it and for anchoring bellcranks/control surface pivots. For these reasons, you will put the ribs where you need them, and then what do you do? Place the wing joints where the ribs are supposed to be? Use extra ribs?

Next, if it is a wet wing, getting the damned thing to seal with all of those joints could make for major fuss and more weight. Then, by the time you put on enough fairing compound to level the surfaces after the wing assembles a little crooked, well, you will have some more weight, which is the enemy. My guess is 20 pounds min weight gain for this scheme.

Now for tooling of wing skins, I hotired blue foam, jigged it straight, and bonded in a layer of roof flashing for a hard surface. Tools do not get simpler than that, and they were quick to build. These tools will not travel well, but they will make several copies of their intended parts, and the parts well travel well.


Billski
 
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