Vintage Rodel ASK21 Glider Kit

[mlachow]

I have acquired a vintage Rodel ASK21 kit. Probably from the 1990's. The wing is sheeted and while the plans show a blade joiner, the kit comes with a fiberglass tube / 20mm steel tube joiner. The hole for the fiberglass tube is drilled but it is not glued in. It appears that there is a thick balsa sub-rib in the wing close to the end of the tube. The root rib is ply and some extra thickness of balsa.

The joiner tube appears to be some separate package included with the kit and it also includes some laminated carbon fiber or black glass plate material. I think the intent is just to glue the fiberglass tube to the root and sub-rib. The carbon fiber was for securing the tube if you did not have the rib in the wing.

Does anyone have any experience with this kit from the past? Weaknesses or problems with this joiner system.

They also have a 7mm hole drilled in the back for an alignment pin. But here is nothing I can see in that hole for gluing other than the root rib.

[L-spatz55]

Hi, dear......,
Rödels old version of the ASK21 had blade joiners, which later was changed to the steeltube joiners.
To glue the fiberglass tube into the wings, Rödel recommended PU glue. ( Polyurethan wood glue that expands when drying)
This is perfect for Styrofoam.
I have a Rödel Ka6 4.2m which uses the same joiner. In fact the Ka6 wing and the Ka21 wing are the same.
Seems to be a proven sytem, and i have not heard of any problems.
I have the old version of Rödels ASK21, still with the blade joiners.
Flies really nice, and is a good thermal glider!!
Happy landings
Markus

[mlachow]

Thanks for the reply. The old instructions do not mention PU glue. Or the scanning and translating misses it. I'm not sure PU was even commonly available back when this kit was made. I can see where that would be great for bonding to the foam but the important part is the rib and root rib. I was considering either T88 or West Systems G-Flex. It looks like there is quite a bit of space to fill around the tube in the foam area.

[Jolly Roger]

I would definitely go with an expanding glue like PU, as it will fill all the gaps between tube, foam core, skin and ribs, making one integral structure. It worked really well on my Rodel Ka6. I just took care to mask off to allow for the glue squirting out.
I also made a simple wooden jig to hold the tube in position with the correct dihedral and square to the root, as there was a fair bit of play between the tube and rib holes.
Fantastic model. It’s still my favourite flyer. Have fun!

[Jolly Roger]

Here’s a link to my Rodel Ka6 build, which may be of interest as it shares the K21 wings.
viewtopic.php?t=1141&hilit=Ka6

[mlachow]

I had some carbon braid in the shop that fit the tube. I put that around the glass tube and now it is a little bit better fit in the hole in the wing.

Looks like a shared wing. Looking at various drawings, it's not quite a ASK21 wing as the wing sweeps back just a little but too much. The fuselage roots are parallel and I'll just put in the tube 90 degrees to the root. I need to get some fresh PU glue.