Dear friends,
first of all, sorry if my English is not as good as I would like it to be.
I have decided to build a Mustunt IV, I am just starting and I am in the phase of preparing templates, profiles, materials, etc.
I am transferring all the parts from the plan to DXF files to be able to laser cut the parts and by the way have the plan digitized, I think it is more operative and I like to have my plans like this. (See Picture 1)
Well, so far no problem, just a little work with the PC and correcting small errors of measures that do not match in the plan, etc.. I think nothing serious (or not?).
But I have found a small obstacle that really has me blocked and I don't know how to move forward.
When I was going to define the templates to make the ribs, I realized a surprising thing: the profile of the root rib is not symmetrical and that of the marginal rib is symmetrical (see Picture 2). Of course, this generates several issues:
a) It also makes the profiles different. (See Picture 2)
b) Is it a drawing error or this plane really has such this kind of airfoil (asymmetrical in the root and symmetrical in the marginal, and also in one part it is widening)? See the lower lines of the airfoils in Picture 2.
c) After giving a lot of thought to the matter, it turns out that if we make the root rib symmetrical and reduce it in the X axis to 80% and in the Y axis to 75%, the result is that we obtain the almost exact marginal rib. (See Picture 3)
All this leads me to the conclusion that perhaps some deformation must have occurred at some point in the treatment of the original image of the plane, unless of course the original design included these strange profiles, which I do not believe. I am almost 99% sure that this is the way I will follow: make the root rib symmetrical and from there take out all the ribs; applying the percentages of reduction and distance between ribs is not complicated in this case. Another option would be to make the marginal profile asymmetrical, it is not difficult either, dividing each rib in upper and lower part. What is clear to me is that I really don't know how to go about making all the ribs using two different profiles and also one symmetrical and one asymmetrical.
What do you think?
On the other hand, a doubt, in a wing with dihedral the ribs must be vertical or at 90º with respect to the spar? (See Picture 4). I think the right way is to place the ribs 90º respect the spar (drawing below).
Thank you very much for your comments and help. I promise lots of pictures
Greetings to all