Here’s how they used to do high production volume extruded spars for strut braced wings, these are Piper. Very inexpensive if you’re making lots of them.
I saw a program about the Lotus Elise. The procedure from design to first prototypes. The car is almost exclusively made from extruded aluminium. The designer were so hooked on extrusion he even made the pedals as extrusions. Then these extrusions were glued together. I don’t know if the production cars ended up being “all” extrusions, but it was a pretty interesting program.
Extrusions are a good solution to many production issues, not least because the tooling is really cheap. I designed one product in 1992 which went into an extruded box and I paid only about 1k for the tooling. The profile was really intricate, too.
But back to the topic, the aluminium most often used for extrusions can also be anodised, and this is what the aluminium window and door business runs on.
OTOH these components don’t need to withstand fatigue, like aircraft structures do.
Silvaire wrote:
In other words, built up from milled parts.
I a look at my RV-4 spars yesterday night (haven’t looked at them for years). The “web” (or rather attachment for the wing skin) is made from rather thin plate with the flanges bent. It’s the same in that picture, the web forms a U channel. That this plate could possibly be alclad, I don’t know, but it’s 2024 for sure, so it’s rolled. For the -4, the webs are doubled close to the fuselage. In addition the (real) flanges are made up of 5 strips about 1/8 inch thick, stacked on top of each other (they could also be alclad, I’m not sure). Close to the fuselage, all 5 are stacked, but the outer ones are shorter, making the web gradually taper. At the tip, there is only one strip left.
I don’t know what RV that picture is from, but from the -8/-7 the new generation of kits came, with lots of simplifications. On the picture the web is riveted to a pre-made thick plate with lightening holes. This function as flange and “inter coastals” (I think the word is). The inter coastals are attachemnts for the ribs and also stiffens the web so it won’t buckle and crush in top to bottom direction. On the -4 these are made from individual members. I think on the newer kits, the flanges themselves are made, not from strips, but from milled larger stock.
However, the anodized (and pre-made) spars for the -4, are not made by Vans. They are made by a different company, but sold through Vans. They could very well be exactly as that picture for all I know. Milled parts are certainly not alclad, and hence they are anodized, except the web which probably is alclad.
My Onex spars are made a bit like the “new” Vans, with this thick flange/inter coastal member of thick plate. But the flanges are made from angle stock. They are also made entirely of 6061 alloy, so corrosion is not a problem. 6061 is a bit weaker, so they are considerably beefier than vans.
On our RV-14 kit, the spar is all clear anodized. The web is made of sheet aluminium (nearly 1/8 inch thick) which has had lightening and fixing holes drilled and flanges bent top and bottom. At the top and bottom of this web there is a milled piece of aluminium bar stock which has been riveted on.
There are some pictures of the center section on my wife’s blog here
