Talk Composites - The Forum for Advanced Composites

Manufacturing a box-spar

http://www.talkcomposites.com/Topic31967.aspx

By student00 - 2/9/2019 2:08:49 PM

I am very new to aircraft structures so excuse me if my questions dont make too much sense, anyway here goes:

1) I understand that the spar is a structural element that extends the entire length of the wing, it carries majority of the load experienced by the wing. From my googling, I have seen different shaped spars, some are like circular rods while others look like rectangular beams? Is this correct or am I confusing it with some other part of the wing?

2) What does "box-spar" mean? does the box refer to the box that also includes the ribs, etc?

2) How are "hobby" spars made (I mean not for a passenger aircraft, but lets say for a smaller UAV) ? Are they wrapped around one male mould and then pulled off after curing? Are they hand wrapped around the mould? (I am interested in techniques that arent too expensive)

3) From what I have read, I have seen Invar and steel moulds being used, this is quite expensive. For a more economical option, could I use a foam tool?

4) I have read about sacrificial tooling but havent quite been able to understand it. Could it be considered for making a spar?

Thank you!
By SleepingAwake - 2/10/2019 4:52:19 PM

 
student00 - 2/9/2019 2:08:49 PM
I am very new to aircraft structures so excuse me if my questions dont make too much sense, anyway here goes:

1) I understand that the spar is a structural element that extends the entire length of the wing, it carries majority of the load experienced by the wing. From my googling, I have seen different shaped spars, some are like circular rods while others look like rectangular beams? Is this correct or am I confusing it with some other part of the wing?

2) What does "box-spar" mean? does the box refer to the box that also includes the ribs, etc?

2) How are "hobby" spars made (I mean not for a passenger aircraft, but lets say for a smaller UAV) ? Are they wrapped around one male mould and then pulled off after curing? Are they hand wrapped around the mould? (I am interested in techniques that arent too expensive)

3) From what I have read, I have seen Invar and steel moulds being used, this is quite expensive. For a more economical option, could I use a foam tool?

4) I have read about sacrificial tooling but havent quite been able to understand it. Could it be considered for making a spar?

Thank you!

Not into the RC stuff anymore but as far my understanding goes:

Yes, the spar is the structural part of a wing. a box spar can be a square section type thing, but i think often times it is a D section which basically turns the first third or so of the wing from the leading edge into the structural part of the wing. you want a box section and not an I-beam because a closed section will be much better in terms of torsional stiffness. Therefore you want a mix of +/-45° Layers for torsional stiffness, and unidirectional fibers for the bending loads.
A box spar can be made by wrapping structural fibers around a cnc or hot wire cut foam section, which is then fillered and sanded to get a smooth surface. or idealy you make a negative mould in which you make the parts to get a smooth surface on the outside directly. Forget invar tooling for home projects...

hope this helps as a starter...