[[searchwing-fiber]]

After still having major problems with waterproof design, the idea is to start a new fuselage design from scratch in fiber composite technology. This promises the following advantages

  • Waterproof material - foam is not water resistant
  • Possibility to adapt the geometry to our requirements, e.g. camera connection
  • Thin material requires only small holes for camera without obstruction view
  • Fiberwings will pave the way to possible solar cell support for extending range

The big drawback is missing experience with aircraft design and fiber technology.

  • Design a negative lamination mould from Rampf MB-0600 Polyurethan material by milling
  • Mill: Step-Four Xpert 1000 S in the Holzwerkstatt Modellbau
  • CAD: Onshape, CAM: Deskproto, NC: XpertMill (Holzwerkstatt)
  • Glueing of the Rampf MB-0600 for L shape: Rampf EP2306 resin + EH-2904-1 hardener
  • Surface Sealing of the MB-0600 material with Münch Mikon 399 MC sealer
  • Release Agent (Trennmittel): Münch Mikon® Mirror Wax liquid W-99+
  • Alternative Release Agent: RAKU® TOOL AC-9103
  • Laminate 2 layers 160g/m2 GFK (R&G)
  • Epoxyresin from R&G

The Deskproto CAM software needs some RAM depending on the detail level. The Deskproto Software is installed on the breakout.

On 15./19./20.12.2020 we did a first milling test with a small MB-0600 test block

The milling was done aiming at best milling results. So the distance between milling paths and z distance was set to 0.06mm. Schlichten took 2h 50min for the “Z Konstant” strategy and 7h for the “Überkreuz” strategy.

(Friedrich Beckmann, 23.12.2020)

Some initial lamination test with the “Minirumpf” with 2 x 160g/m2 glas fiber with vakuum showed laminates which seem optically o.k. but the laminate is not waterproof. I made three tests with different amounts of resin in the mould. The final weight after the vakuum process is however always more or less equal. The area of the “Minirumpf” is about 3dm with a laminate weight of 21g.

On 4.3.2021 Alex, Björn and I did a lamination test of the 80cm fuselage half.

  • Surface Sealing of the MB-0600 material with Münch Mikon 399 MC sealer
  • 2 x Release Agent (Trennmittel): Münch Mikon® Mirror Wax liquid W-99+ (1 month waiting time)
  • R&G Resin L with EP161 Hardener
  • First layer of pure resin with brush
  • 1 x 49g/m2 glas fiber (brush)
  • 3 x 160g/m2 glas fiber (brush)
  • Abreißgewebe (brush)
  • Lochfolie
  • Saugvließ
  • Vakuumsack at -900mBar for 24h
  • Removal of the laminate from the mould after another 24h

Results

The laminate is not waterproof. After about 10 seconds water penetrates through an optically o.k. laminate.

There must still be air/voids in the laminate although it seems optically in good condition. The fuselage half has a weight of 116g.

First Laminate - Weight 116g

Ideas

A flat test laminate without vacuum shows a closed surface and a simple water test did not show easy water penetration. I think we must find a way to avoid the voids/air in the laminate. I am pretty sure that the voids also have an impact on the strength of the laminate but nothing is tested on that side. So to improve water resistance I have the following ideas:

  • Add an epoxy gelcoat layer. Yachts and gliders have a Gelcoat finishing layer but most model planes do not have that. This will hopefully provide a closed watertight surface layer.
  • Hand lamination without vacuum. The hand lamination will have more resin in the laminate and the surface seems closed. No idea if the voids are reduced or if there is just a closed surface.
  • Vacuum infusion. Compared to vacuum bagging literature claims that voids are reduced with this technique. The VAP membrane technology might be a way. This promises a void free laminate with a high fiber content.
  • Degassing the resin. Is probably useless for hand lamination because bubbles are introduced during the lamination process.

(Friedrich Beckmann, 7.3.2021)

  • searchwing-fiber.txt
  • Last modified: 2021/03/08 12:34
  • by beckmanf