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Re: AUDAX

Publié : 12 mars 2015, 18:54
par Bloodhound
I started working on the stabs by preparing the ribs supporting the servo and incidence adjuster. To make sure these will be secured properly, i added small pieces of 1.5mm plywood to reinforce the liteply locally. I drilled the holes and temporarily attached the adjuster and servo using wood screws.
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Baking paper is used to keep the stab jig from sticking to the building board. CA glue doesn’t penetrate the baking paper, and the jig is attached to the board using pins. There’s no need for printed drawings to assemble the structure; all i had to do was tracing 2 perpendicular lines on the paper, align the first 2 members of the jig with these lines and everything else is self-aligning.
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I didn’t want to rely entirely on the ribs to achieve the proper curvature of the leading edges, so during design stage i also added a horizontal former which will help bending the leading edge with improved accuracy and perfect symmetry between the 2 stabs.
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To make the stab structure easy to detach from the jig, the ribs are attached to their supports only in a few points. To prevent any glue running from the joints to accidentally flow into the small spaces between the ribs and their supports (thus making the structure difficult to detach from the jig), all rib supports have semi-circular or oval cut-outs situated directly below the joints. I hope the picture below explains this better:
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A few more pictures showing the assembly process:
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Re: AUDAX

Publié : 17 mars 2015, 18:43
par Bloodhound
Adding the rib doublers:
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Finished stab structure:
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Adding the fiberglass sleeve:
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Detaching the stab structure from the jig:
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Sanding the leading edge following the airfoil shape:
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Preparing the upper surface skin, using 2mm balsa:
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Attaching the upper surface skin to the stab structure:
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Sheeted stab structure (only upper surface for now):
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Re: AUDAX

Publié : 21 mars 2015, 18:45
par Bloodhound
Adding the balsa block for the control horn and the wood block for the stab retaining screw:
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Sheeting the stab lower surface:
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Adding the trailing edge:
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Re: AUDAX

Publié : 25 mars 2015, 18:05
par Bloodhound
The 6mm balsa leading edges are quite stiff and it would be very difficult to bend them following the shape of the stab. I had to soak them with hot water (which makes them a lot more flexible) and let them dry overnight in a curved position.
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It was now quite easy to attach them to the stabs:
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To shape the leading edges accurately, i improvised a tool to help me mark the centerlines on the balsa strips. By shimming it with tape at the bottom and lightly sanding it at the top, i calibrated its height to leave a mark precisely at the centerlines of the root and tip ribs.
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After some careful sanding, the result looks like this:
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Assembling the stab tip blocks and attaching them to the stabs:
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Shaping the stab tips:
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Progress on the stab so far:
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Re: AUDAX

Publié : 29 mars 2015, 16:27
par Bloodhound
Separating the elevators:
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Preparing the balsa hinge lines:
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Attaching and sanding the hinge lines:
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Attaching the stab root balsa block. This will be sanded later to fit the fuselage:
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Weight and progress on the stabs so far:
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Re: AUDAX

Publié : 03 avr. 2015, 18:06
par Bloodhound
With the stabs almost done it's now time to move on to the wing assembly.

All the wing ribs are made of 2.5mm balsa with the exception of the root rib which is made of 3mm liteply. The ribs supporting the wingtube have 1.5mm plywood doublers to reinforce the balsa locally near the wingtube holes and also to connect the 2 spars. This helps transmitting the loads from the main spar to the carbon tube and distributes the loads more evenly through the structure. The root rib also has a blind nut for the wing retaining screw and a doubler near the leading edge where the incidence adjuster will be placed.

The first step was preparing the first 5 ribs by adding the plywood doublers, blind nut and also slightly sanding the wingtube holes to match the diameter of the sleeve.
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The jig assembly starts at the trailing edge which is made of 2 parts so i had to make sure it is perfectly straight.
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I also had to check the perpendicularity of the member near the root rib. Together with the trailing edge, it will define the alignment of all the other parts, so it is important to make these 2 perfectly straight and perpendicular to each other:
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All the other parts are self aligning:
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Adding the ribs:
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Re: AUDAX

Publié : 09 avr. 2015, 20:13
par Bloodhound
More work on the wing assembly:
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Adding the curved trailing edge:
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Adding the aileron end ribs and hinge line former:
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Adding the leading edge formers:
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Assembling the servo box:
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Progress on the wing so far:
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Re: AUDAX

Publié : 10 avr. 2015, 01:11
par Acromaster
Very nice work!
I do appreciate.

Olivier

Re: AUDAX

Publié : 10 avr. 2015, 07:46
par Bloodhound
Thank you Olivier!

Re: AUDAX

Publié : 18 avr. 2015, 15:30
par Bloodhound
Bending the 6x6mm balsa stringers with water:
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I used the shear webs to determine the correct position and distance between ribs along the spar:
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Attaching the main spar balsa stringers:
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The ribs near the tip of the wing are too thin for the 6x6mm balsa stringers, so i replaced them with a balsa former:
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Adding the 6x6mm balsa stringers for the wingtube spar:
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Adding the wingtube sleeve:
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Adding the shear web:
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Completed left wing structure:
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Re: AUDAX

Publié : 19 avr. 2015, 07:18
par claudecuinet
Hello Alex

Awesome job !
You did composite wings for this plane as shown on picture below. Why doing scratch build wing

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Re: AUDAX

Publié : 19 avr. 2015, 07:57
par Bloodhound
Thank you Claude !

The first set of composite wings was very heavy, around 500g/wing. Maybe it was good enough for a few test flights but not for competition flying.

As i said before, all the composite work was done together with a friend of mine who is specialized in composite work and has a workshop. He was very busy molding a jet and a few other projects this winter so i didn't want to bother him with another set of composite wings. Instead of just waiting until he finishes his own projects, i decided to build the balsa structure wings, stabs and rudder and try to get the plane in the air this summer.

We are not going to give up on the composite wings, just need more time to achieve a good weight.

Re: AUDAX

Publié : 20 avr. 2015, 14:19
par Bloodhound
Right wing structure completed:
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Re: AUDAX

Publié : 27 avr. 2015, 16:42
par Bloodhound
Wing structure detached from the jig:
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Sanding the leading edge former following the shape of the airfoil:
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Sanding the excess glue from the shear webs:
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Preparing the wing skin:
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Wing structure and skin attached using polyurethane adhesive and pressed together in the jig:
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A few images of the result:
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Re: AUDAX

Publié : 28 avr. 2015, 13:45
par jclaude
Wahouw! Cool structure.