# What could be done to reinvent the Affordaplane to a more homogeneous project?

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#### Speedboat100

##### Banned
Kite is not ready. Details need time as it has to be lite.

Cellar is also pretty chilly as is the weather here.

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#### blane.c

##### Well-Known Member
Supporting Member
You know "homogenous" --- not afraid of --- "very happy people".

#### Speedboat100

##### Banned
You know "homogenous" --- not afraid of --- "very happy people".

Homo Sapiens....is loosely....a thinking man.

#### Tiger Tim

##### Well-Known Member
I’ve been sort of sitting on this idea for a while now, but I wonder if it would be worthwhile to build a narrow fuselage from bent channel instead of extrusions. If you had a big enough brake in your shop you could make the channel yourself, controlling wall thickness on each part for best weight while being strong enough. The quick sketch I attached is more intended for CNC cutting and a kit but it gets the idea across. The upper and lower channels have the gussets for attaching the uprights cut right into them and all holes would be pre-drilled (I also included a sort of code for the holes that could prevent a kit from being put together incorrectly). DIY channel also allows for a taper in your fuselage, again putting lightness and strength where they’re needed. The rough CH-701 shape was just chosen as an example here, it’s all just rough and conceptual at this point.

#### Victor Bravo

##### Well-Known Member
Supporting Member
@*($*(F%M#*$% !!!

I was already spending the money I was going to make on this idea !

This is a very good idea, and would bring the A-plane concept much closer to having some "real airplane" panache, gaining efficiency, and shedding weight like Billski is always haranguing us about.

063" sheet aluminum, with strategically placed doublers that nested inside or outside the main channels, can be riveted together with AN solid rivets and a hand squeezer. Saves money, weight, and gives you a better structure.

The channels can be Alodine-dipped or wash-primed or chromated before assembly in a narrow home made tub or trough... no spraying toxic vapor, no paint booth, but no corrosion.

The great part is that these channels can all be easily made on a common press brake, us ing nothing more than a laser or ink marked bend centerline at the location of each bend.

This idea is VERY well worth exploring, fine-tuning, finding flaws in the idea, and moving forward with if possible.

EDIT: And the tapered cross section... F!(#*NG brilliant !

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#### rtfm

##### Well-Known Member
A really intriguing idea. What a pity I don't work in aluminium.

#### Mohawk750

##### Well-Known Member
Interesting concept, I see the merits particularly if it was to be produced as a kit. You will need a pretty substantial press brake to bend those long channels out of fairly heavy gauge material. That will make it unworkable for any homebuilder, plus all the diagonals will be different widths with flanges other than 90 degrees and if the top and bottom channels are not identical the diagonals will have to taper as well.

This is a very good idea, and would bring the A-plane concept much closer to having some "real airplane" panache, gaining efficiency, and shedding weight like Billski is always haranguing us about.

I've reviewed a few A-Plane build logs and some builders try to save weight by replacing the 2x2 upper and lower tubes with 1x2 and atching the gussets with 3/16" stainless pull rivets only to find out they are nose heavy and end up with a chunk of lead bolted to the tailpost!

I think the airplane needs a basic redo on the layout to accommodate the size of engines most people end up putting on them. Use the 1x2 in the tail with rivets but make it a bit longer, Move the wing ahead a couple inches and wrap the leading edge with aluminum from the bottom over the top to about the 25% chord line. If you don't like looking at the flying truss go ahead and cover it with fabric. You won't make Part 103 but you'll have a better airplane,

#### Tiger Tim

##### Well-Known Member
Glad you guys like it, the idea is the latest evolution out of my 14-year-running sketchbook of ways to improve* the A-Plane. I had channel on my mind for a while but the taper I think is the real revolution and the key to this whole affair. It would give a bunch of strength but also make room inside for control mechanisms and stuff. I hope Fritz still lurks, he’s always clever with developing this sort of stuff.

*sometimes ‘improving’ is just a matter of making something more amusing to me. There’s a whole line of flat, scale-ish warbirds in there starting with the Afforda-Stang then including the Mildcat, and a profile Corsair that’s totally bonkers in every way... on purpose.

#### Tiger Tim

##### Well-Known Member
all the diagonals will be different widths with flanges other than 90 degrees and if the top and bottom channels are not identical the diagonals will have to taper as well.
If the ‘caps’ (for lack of a better term) of the channels were the same width on every component you could have a depth stop on your brake; push the pre-cut sheet in until it hits the stop then bend 90°, assuming the parts were milled/lasered/waterjetted with a good bit of accuracy then the web of the channels will stay compatible with each other. Really just adds to how it begs to be kitted. I don’t think there’s enough taper in the top and bottom keels to have to think about the diagonals being bent to anything other than right angles, they should torture into shape easily enough when riveting them together.

I don’t know I feel there are any clever and elegant ways to attach spars, landing gear, or engine mounts to this truss of channels yet.

#### Mohawk750

##### Well-Known Member
LoL! keep those creative juices flowing....and with that in mind....

Why not just run the 2x2 tube through the tablesaw to make it a channel. Now you have access to solid rivet all the gussets and nest the diagonal tubes side by side in the bottom of the channel with a single bolt. You've just eliminated the equivalent of one complete longeron tube and all the stand-offs for the diagonals!

#### nestofdragons

##### Well-Known Member
Bend plates have one problem. Having the bend tool that is long enough. Most tool are not longer than 1m. Mine is only 0,6m.

#### Tiger Tim

##### Well-Known Member
Bend plates have one problem. Having the bend tool that is long enough. Most tool are not longer than 1m. Mine is only 0,6m.
You’re right, it would need a mighty big brake. Some sheet metal shops could probably help out but admittedly it’s probably best as a kit that gets cut, drilled, and bent at the manufacturer.

The tapered channel ‘keel’ idea is an evolution of an idea I had where a whole Ultralight kit could be shipped in packages no longer than 2 metres (a little over 6 feet) but I’m not sure if fuselage structure could or should be spliced at the rivet clusters like it would need to be for such short parts.

#### Victor Bravo

##### Well-Known Member
Supporting Member
The tapered keel parts have another advantage. You can nest the pieces together for shipping, stacking several parts with only a small increase in length.

With the taper, you can also have a two-part keel that overlaps, without a separate joiner piece.

#### Mohawk750

##### Well-Known Member
The Butterfly was a Belgian kit (started as a hangglider but evolved into a very ultralight motorized airplane) which could be assembled with rivets in two weekends.
Pou-Guide - Un ultra-léger très ultra-léger: le BUTTERFLY
I was intrigued by the use of "thermoformed polystyrene" used for wing ribs on the production models. I can see certain advantages in the forming of flanges for stiffness and simplified attachment to tube spars. The sheet material could possibly be used for a formed leading edge and bonded to the ribs with adhesive. Hard to beat a light gauge aluminum formed rib for strength to weight but it appears polystyrene is viable in a light aircraft construction. Once you have the form you could knock out dozens of ribs is a short time inexpencively with thermoforming.

Anyone have any experience thermoforming aircraft parts?

#### rotax618

##### Well-Known Member
Would be necessary to do a FEM analysis and check for torsional resistance for the lightweight truss.

#### erkki67

##### Well-Known Member
if possible I'd rather print the ribs today.

#### erkki67

##### Well-Known Member
The bent sheetmetall into chanels with the brackets is indeed a viable idea.

3-4' long sections can be hold by most bending brakes.

Cnc routed, watercut or lasercut parts would make the kit manufacturing a breeze, and even assembly would be possible within a few days instead of months or years.

#### Hephaestus

##### Well-Known Member
I'd be cautious about any heat formed plastics myself...

HIPS - 3d printed version of polystyrene - has a glass transition temp of around 88c - meaning that's when it becomes malleable and permanently can be deformed.... at lower temps with pressure applied - it'll still deform.

I know of one thing I printed in hips that permanently deformed inside a car on a mild-er arizona day...