I am bored today! I work databases at a national retail outlet so I have to be here in case there are any problems with the website or store POS systems however hardly anyone else is here and so unless something does crash I have NOTHING to do.
So I will kill time giving you answer that is probably far too long. Still, I think you raise very good points and I would actually enjoy addressing them with and I have the time so…
Oh yeah! It is getting built!
LOL! To quote one of my favorite TV shows, “Failure is always an option!”
Well the trick in aircraft is not absolute strength but the strength to weight ratio. If you build a very light structure then a lot of absolute strength is not needed. Several tricks come into play there. 1) Stresses generally go around the edges of a structure so that is why the parts are basically just outlines. That results in a vast reduction in weight with a very small reduction in overall strength 2) Now add the flanges around the edges (making each part a virtual L-angle) and again you buy a lot of added strength for small amount of additional weight.
- “Honey combing” - adding structure inside a nominally hollow part to keep the strength to weight ratio higher. The printer software does not do true octoganal “honeycombing” like on full size aircraft but the prictured crosshatching is something that is very easy to do with 3 printing. Well at least with the Cura software I am using it is very easy to do.
- a spar does not live alone…there are three spars (leading edge, main and trailing edge. All combined into a virtual box by the ribs.
You lost me on the “seams”. Do you mean where individual parts join together? If so, I think I have that under control with 1) How the parts ‘notch’ together - note how the slot in the main spar is filled by the aft rib sliding into the spar slot from the rear - then the forward rib sliding into the combined notch of the spar and aft rib. Now the spar is now solid (except for the the radiused lightening holes) 2) Adhesives today are quite impressive. It is quite easy to have a bond stronger than the actual part. So put adhesive on those ribs before you slide them in and now 3 individual parts became one part
Well, we will see. Before I dove in I did some test prints with honeycombed PLA and I was very impressed with the strength to weight ratio, Again though, I think I have all the angels covered but “failure is always an option”
On a totally different note, the single biggest problem I am having with printing verses other methods is tolerances. e.g. I those ribs are drawn 3/32 thick as well as the slot in the spar however I widened the slot 1/64th to allow a little room. The ribs came out MUCH thicker and would not go into the slots- not even close!
I found I have to watch the slicing software and do the math 1) the slicer software wroks in millimeters and I am doing standard 2) as the initial layer height and additional layer height in the build up may not come out evenly (to the millimeter) and the software will round up. I expect machines to obey! When I say 3/32 I mean 3/32 and NOT “>= 3/32” ■■■■ it! Stupid software!
Thank you so very much! I really appreciate that! I really do! Yet I have soooo much more to learn!