Grimace
Well-Known Member
I'm still toying with ideas to make a plane cheaply. Stuff like selecting fabrics based on the generally-available widths of material is not escaping me... By that I mean I'm considering that if a single ply rolled out across the span can cover from the trailing edge at the top all the way to the rear spar, then you can make the wing with minimal excess/waste. Simplicity of construction is also a large concern.
The thought that I'm toying with right now is based on a box-spar with flat surfaces all around and bonding the three thirds of the wing (fore, mid and aft) independently to the wing, one at a time.
The advantage would be that the unidirectional spar caps need to be encapsulated by cross-plies to prevent delamination. So, by bonding the sections individually, you could then lay a single ply of 45+/- knit over the entire wing to encapsulate the spar caps.
Why not just make a full skin? Or a top and bottom half and bond them together? Because that will require either a female mold with cores vacuum-bagged precisely for the step at the end of the core to mate up with the spar... or else a male mold with a step built in. If you do it as three separate pieces (front, mid, rear), there will be no "steps" needed to accommodate the spar because each third of the wing will have its own termination point.
Assume, for a moment, that you built the wing in pieces... that you made the leading edge up to the spar as a "D" with the left (flat) portion bonded directly to the spar. And you then made the middle sections, top and bottom, and bonded it to the spar. And then bonded the rear/false spar to the back.
And let me add that I know that in the greater scheme of things, a few dollars here or there isn't a big deal. However, I do believe that it adds up and that if a grand or two can be shaved off the cost of a light/cheap airplane at the cost of a couple knots, then that's a pretty cool and worthwhile thing at the lighter end of the experimental spectrum.
I know most planes are not built this way, but it does seem simple. Does anybody see any glaring structural issues with this approach?
The thought that I'm toying with right now is based on a box-spar with flat surfaces all around and bonding the three thirds of the wing (fore, mid and aft) independently to the wing, one at a time.
The advantage would be that the unidirectional spar caps need to be encapsulated by cross-plies to prevent delamination. So, by bonding the sections individually, you could then lay a single ply of 45+/- knit over the entire wing to encapsulate the spar caps.
Why not just make a full skin? Or a top and bottom half and bond them together? Because that will require either a female mold with cores vacuum-bagged precisely for the step at the end of the core to mate up with the spar... or else a male mold with a step built in. If you do it as three separate pieces (front, mid, rear), there will be no "steps" needed to accommodate the spar because each third of the wing will have its own termination point.
Assume, for a moment, that you built the wing in pieces... that you made the leading edge up to the spar as a "D" with the left (flat) portion bonded directly to the spar. And you then made the middle sections, top and bottom, and bonded it to the spar. And then bonded the rear/false spar to the back.
And let me add that I know that in the greater scheme of things, a few dollars here or there isn't a big deal. However, I do believe that it adds up and that if a grand or two can be shaved off the cost of a light/cheap airplane at the cost of a couple knots, then that's a pretty cool and worthwhile thing at the lighter end of the experimental spectrum.
I know most planes are not built this way, but it does seem simple. Does anybody see any glaring structural issues with this approach?
