1.8m Fibreglass ASK 21 Glider

[Jackson T]

I've wanted to make a scale glider for years, but never actually did it because I wasn't sure how to make a cheap fibreglass fuselage. I recently experimented with a new idea that I think will work, and decided to make a small ASK 21 as my first fibreglass project. The ASK 21 was chosen because it has a much lower aspect ratio than most gliders, making it easier to make a smaller scale glider.

Reserved for specs

The fuselage will be made from a plug of styrofoam sheets hot glued together and sanded to shape. Cornice cement, a plaster-like substance will be poured over the plug to make the two part mold. For mold release I'm using a $3 tin of Dubbin boot polish from the grocery store, which worked well in my test. Here's some pics of the progress so far.

 

[Jackson T]

The foam was breaking off at the tail, so I glued some balsa on to get a proper shape

 

[Jackson T]

The majority of the surface was covered in packing tape and cardboard was taped along the centerline of the plug. Next will be pouring the plaster, I'll hopefully get it done this arvo.

 

[Jackson T]

A lot has happened since the last post! Long story short, the cornice cement set too quickly and the cardboard struggled staying on, so I decided to lay the fibreglass directly on the plug one side at a time. I added some boot polish to ensure the fibreglass would release easily.

Two of the guys from work wanted to buy one, so I decided to use the fuselage halves as molds to make more. There were some ripples from the tape on the inside of the molds so I had to do some filling/sanding to smooth them out.

I also slightly over-trimmed one of the molds at the tail, so I put some tape on the inner surface and put some epoxy on the outside. When the epoxy cured I pulled the tape off and sanded away the excess.
I tried to do the layup using small plastic rectangles to push the resin around instead of paint brushes, but it didn't work very well in the concave mold surface. It worked great when I fibreglassed the plug. As a result I ran out of time and didn't get the third layer of cloth in. There are also a few spots that didn't get enough or have too much epoxy because it started gelling before I could fix it. I should be able to fix up the dry spots and put the last layer in on top of the cured first and second layers, so it should all work out ok.

The part came out very easily using two coats of boot polish as the mold release. The big dirty smudge on the part is because one of the layers of cloth had heaps of dust in it from storage. It will be painted later, so it shouldn't be a problem. I placed a tape line around the edge to avoid any dribbling epoxy bonding to the outside of the mold.

 

[Baron VonHelton]

I thought you'd went out for tuna at the Greasy Spoon there for a minute.....