I wouldn’t rely on fishmouthing for any sorting of real loads in a non-welded joint. If you’re intersecting at close to a 90 degree angle you might take up some compressive axial loads but that’s it.With the riveted tube the rivets do provide all the strength in keeping the members together. The problem is that if you only have one gusset plane and the rivets in line on a tube/whatever on that one plane, then it's possible for the tube to rock or wiggle left and right along those rivets. The ways to prevent this are to fishmouth the tubes tight so that they have a snug fit and physically resist movement, or have at least one other contact plane (and preferrable perpendicular or anything but parallel to the first plane) with more rivets so that they prevent the tube from rocking around one point. In such a setup, yes, the tubes don't need to touch at all, but you don't want too much gap or you need gussets with enough stiffness not to flex/buckle/etc.
We're just talking concept stuff here, no one's picking out china patterns. Besides, ...I'm in a happy, committed relationship with the Ranger.If for any reason Fritz stops working on the Ranger project because of this tube and gusset discussion
Out of curiosity, is it possible to get a WAG on the cost of those 3D printed joiners you proposed that would add strength and hold each joint/cluster in precise alignment while the builder affixed the AL gusset(s)? I know they have been rejected, but what could a builder expect them to cost?It would cost the same either way.
Right, I meant rejected for use in this building concept, as proposed by VB.Nothings rejected. When I get around to a building a TnG airplane you can bet it'll have be 3D printed joiners.
There are certainly ways to complicate this with time-intensive parts, printed parts, etc, but I would definitely rather see them not used.
So, about $20 in materials cost for all the junctions in a small plane. Obviously, if we add machine time and setup, it would cost more (i.e. if our homebuilder takes the thumb drive to a local Maker, or if the daddy rabbit for the plans makes the CF PETG joint "framing aids" available as part of a small kit for those who would rather not mess with printing the parts). For this investment we get self-jigging joints where all the tubes in a cluster exit at the proper angles and are held in place at those angles so the builder can rivet on the gussets. And we get some stay-in-place redundancy at each joint. Also, if the design does use square/rectangular tubes (they do have advantages in some applications), these joiners also index the shapes so everything is aligned right. Got it--super. An efficient, new approach to accomplishing a fundamental part of the build.Depending on the size of the joiner and what they were printed with they would probably cost somewhere between .10c and .50c a piece. If there were about 25 of them on the fuselage it'd be around $10 to print them with regular PETG filament. Double that if they were printed in carbon fiber filled PETG. (CF PETG would be gilding the Lilly but I'd probably use it anyway)
Looks like an aluminum KR2. Quite a line of interesting designs. http://www.morganaeroworks.com.au/cheetah.htmlHere is a video of the square tube version, it is yet to have all gussets and skins on the outside added. To me it looks very strong and easy to build as a process.
sorry about video quality
3 things I can see:But if the cleco holes are already located in all the parts, what does the printed assembly aid alignment tool do?
Badly placed? Near an airport?Here is a example of tube and gusset from here in Aus. but this is a low wing and using round tubes. The higher performance version has a square tube version and looks the same.
One of these is famous for flying into a badly placed Ferris wheel. No injuries, rebuilt and flying two weeks later.