Crafting Main Wing Test Piece for Primary Glider

Crafting Aileron Test Piece for Primary Glider by No Mold only Sheet Work - stockroom

Recommend watching the previous report first.

weight is 2100g, lenght is 1200mm

Introduction

Since we had some experienced crafting by making aileron, next created a main wing that was expanded to be almost similar.

-materials-

・hinoki stick for main spar flange and truss diagonal member

・balsa wood sg 0.15 5mm*5mm for rib and shear panel stifner member

・balsa wood plate 5mm thickness SG 0.2 for rear spar stifner

・birch plywood 1/32in for rib assy gusset

・GFRP plate 2 ply #200 GF cloth ±45° angled for rear spar web and Dbox panel

・single skin 2mm styrene sheet composite with GFRP(#200×2)

・styrofoam 20mm thinkness for forming torque tube 

・PP shrink film 15μm thickness for skin

assembly

rib

Like the aileron rib, made a frame and glued the parts on the it.

But near the leading edge, it has high curvature and balsa wood was broken. So this point made by laminating three layers of thinly sawn balsa.

laminated balsa

main spar

When making torsion box, it is necessary to work by putting hand inside the box, I adopted a truss structure. However, with these dimentions, D box shear stifness redued about 26% even though it is not particularly light compared to the GF web. So I need reconsider box structure and crafting method.

When GF web, box GJ is 8.57*10^5, when truss beam box GJ is 6.38*10^5

torsion box

This is a typical structure called D-box. Shear panel is conposite. Birch plywood is often used but it is so expensive. We made this panel from GF plate and styrene sheet. The GF plate is not a sandwich and is only pasted on one side. Styrene sheet is used to increase thickness to prevent shear buckling so this sheet face outside of box and GF plate is glued to strength member such as rib and spar flange.

balsa ribs are glued to main spar and styro ribs are cutting by hot wire like aileron torque tube. And attach the stifner bitween ribs to prevent shear buckling. When I was D box sizing, I most cared shear buckling stress.

when about 600Nm torque is added, shear stress is 1.5MPa and buckling stress is 4.77MPa
I feel K value is large but there is a margin of safety

Inner box, the far side wall is front panel

After gluing panels, glue the front panel of D box. this is GF plate #200×2. Styrene block for leading edge shaping is pasted on here. Front panel and top, bottom panel are conected by chopped GF epoxy patty to to trasmit shear flow. This work is neet to putting hand into the box.

 

rib attachment and rear spar

Attach the ribs to main spar. It is difficult to crimp. When do this, wind the tape adding to tension. but it is less force for enough crimping so I need to think anoter way.

after attached ribs

After glued ribs, attached rear spar that is consist of flange, web, stifner. 

 

Conclusion

Film rapping and D box face coating is later.

Following the aileron, we continued to work without using molds, but it is not suitable for multiple production. 

Since the styrene panel is very soft, it is hurt easily such as strike something or our nail. So face must be coated early in assembly.

Crafting Aileron Test Piece for Primary Glider by No Mold only Sheet Work

Introduction

For building a primary glider, made an aileron piece to practice actual craft.

-materials-

・balsa wood sg 0.15 5mm*5mm for rib member

・birch plywood 1/32in for rib assy gusset

・GFRP plate consists of 2 ply #200 GF cloth ±45° angled for torque tube and trailing edge

・balsa plate sg 0.15 2mm thickness for torque tube rib

・Styrofoam 20mm thinkness for forming torque tube 

・PP shrink film 15μm thickness for skin

1200mm lenght and 450g weight. I feel it can make 350-400g weight by refining

subassembly

rib

fix wood blocks on the pinted drawing

Prastinc wrap and block's green tape are used to not glued rib assy with table or block.

birch plywood is so expensive in japan that some ribs used gfrp gusset for saving it

Gusset form is 18mm radius half circle for standardization and efficiency. GF plate gusset doesn't match to look of wood member.

Torque tube assy

making GFRP plate

GFRP plate is made from room temprature curing epoxy resin. Squeezed resin to make resin ratio 35-40%. Afeter curing, divide this for required size.

styroform is cut by hot wire

Innner tube rib is composed by 3ply 2mm thickness balsa wood that is angled 0/90/0° . At first I made it 2ply 0/90 but deformed. maybe by moisture.

Gluing them at the designed intervals and cutting styrofoam by hot wire using the both sides rib as guide line. Attach 3 side to rib first( torque tube has 4 side) like next picture back right. For getting torsional stiffness, each side panels must connect by strength member. So between these 3 side panels, making fillet made from epoxy resin with chopped glass fiber and thickener talc.

Be careful of the angle

the last side is attached after glued latter ribs.

this panel also connected by fillet. When assemble this tube, it is necessary to make each panel size slightly bigger or smaller so that assembly errors can be absorbed by epoxy fillet.

Lastly, making trailing edge by gf plate and Urethane foam and wraping by shrink film.

I actually wanted to install the hinges and horns but it is after the main wing assy is completed.

Conclusion

 I wanted to create 3 dimentional objects using sheet or plate work. Without using any mold as much as possible. But I noticed that making multiple pieces of same thing like split main wings, it makes more sense to avoid terrible work by paying the cost of maiking one mold.