Some remarks in
RED
My thought with the CNC mill is that a sine shaped web could be easily produced. A machinist would not have to be really good at turning handles on a manual mill to get that particular shape. (Not true) A program could be produced to cut a particular profile, sine or something similar. I have no doubt that there are various machines capable of cutting the profile.
It was not apparent to me that the spirit here was to contrast a dual beam (Box?) spar with a sine spar when I started reviewing the thread. It took a number of questions before that became more clear. I beams and various structures and sleeves were discussed as well making it difficult to recognize the central theme. (The landscaping retaining wall was the only discussion that was way off topic. Yes, we got into a bit of a discussion as to the limitation of beams as we currently see them constructed in our composite wings).
The discussion now assumes a carbon fiber based material and some sort of resin matrix to keep the fiber in line (appropriately arranged). The direction of the fiber can be thought of as analogous to wood grain with various weave and tow patterns possible. The comment was made that controlling the fiber configuration was one of the drivers for the use of adhesive in the construction. (It was? this is false) My question is what would that ideal configuration look like? (There is no Ideal configuration. we would need a lot more information about how the beam was expected to perform)
My experience is that corners in structures can lead to unexpected failures and hence the mention of fillets. It was also mentioned that increased surface area could enhance adhesive performance. (I think you are confusing two issue here. Adhesive performance is measure force over area. So if the beam fails at the part line add more area to allow for more adhesive. More area improves the beam performance not the adhesive performance) I mentioned fillets for both reasons.
I would agree, my questions are also about the basic performance of beams.
A legitimate topic for another thread.
As communication takes at least two , I have to ask how could I have made it any clearer as to the intent of this thread. I think the first 2 paragraphs clearly state my aims.
I was not planing to get into the nuances of machining. There are a host of tools that most folks haven't been exposed to outside of high school tech shop (too bad most of these shop classes are now gone).
I tried to say that any beam assuming that construction methods are the same would be inferior to the sine wave spar, if the material mass was normalized. So the material had no effect on the beams performance between the samples. It was just the geometries of the beam I wanted to look at when trying to explain the performance advantage of the sine wave spar.
In this forum it was natural for the discussion to move to the HSWS and was again eluded to with my comment that guys on the slope don't seem to understand it.
Hammond moved the discussion into the practical realm with his discussion of how he implements the SWS into his aircraft. I mentioned that with the sine wave spar the adding of fiber across the part line is much more difficult with the SWS than the classic box spar. I then mentioned the Boeing patented process.
Corner fillet performance is fully understood so there really aren't any unexpected failures. Improperly manufacturer spars will suffer premature failure.
No the discussion hasn't assumed composite construction. And no the fiber in composite construction shouldn't be thought as being analogous to wood grain unless the tree can be grown in the shape of the end product. (This can be done and has been done with support structures as seen in Old Iron Sides).
Please note that Doc and I try our best to not get bogged down in math (detailed engineering) on this forum. This is not an engineering journal. (BTW I was an aerospace engineer and Doc has his PHD as a material scientist). We both are aware of how quickly we could loose many reading these posts if we got into formulas to make our points. So while we may keep things at the conceptual level we aren't doing it to be condescending to anyone. We are just trying to give as many folks as possible a basic understanding of the issue being discussed. I try to give reference material so that somebody can dig deeper into any subject I'm discussing. If you think Doc and I see thing the same you might want to read some of the heated topics we get into.
All the best,
Konrad
