Rodelmodell 4.2 meter ASK-21 build help

[JackA]

I am currently building a 4.2 meter ASK-21 from Rodelmodell. I'm new at building scale sailplanes and the instructions that came with the model are in German so I don't understand a lot of the writing on them. I have translated most of it but don't see any instructions for control throws. I know a lot of you guys on this forum are very experienced with these types of aircraft. If anyone out there can help me with that I would greatly appreciate it.

[Steve P]

My 6M had no guidance either. Companies like this more expect the builder to set up throws to their own liking. Can lead to some trepidation for sure. When you get close to being done I’m happy to jump on a zoom call or something video so we can look at it together.

You’re probably gonna want all the up aileron travel that those wings give. One approach is to add a good amount of exponential when you set it up for the initial flight. That way if you go with throws that are too large at least the sailplane will not be super sensitive around the center of the gimbals. And, you have plenty of control if needed. Better too much than not enough! No more than a half inch up and down on the elevator and likely a good amount of aileron throw since they’re out on the end of a fairly large chord wing. Start with aileron differential about 50% down compared to your up travel. You may find you only want 25% down travel when you get the plane all sorted.

For your landing mode you may want a very small amount of down elevator mixed to full up spoilers. This is one that you’re going to have to refine over subsequent flights. Test your landing mode at altitude so that you are certain how the plane behaves before you actually try to land.

You likely want a rudder to aileron mix in your thermal mode. Remember on tow you do not want any rudder mix. Rudder on tow is not good.

Hope that $0.02 helps.

Here is mine…. https://forum.scalesoaring.com/forum...a-and-assembly

[JackA]

Thank you Steve for that information. It will certainly come in handy when I get to that point. I've been going back and forth about how I want to install the control for the elevator. I have just about figured out how I need to do that but has been a pretty big sticking point for me. Also, I want to use a pull-pull system for the rudder which will be the first for me. I think once I get all of the tail section complete the rest will be much easier. Thanks again for your reply and great information.

[mlachow]

I did a quick measurement on my Rodel Pilatus B-4 which is 1/4 scale. Probably similar construction, airfoils, size is in the same ballpark so travel measurements are probably similar..

Ailerons were 12mm up, 10mm down in a more aerobatic mode and 12 up, 8 down in a thermal mode.
Elevator travel is around 15mm up and down. Elevator compensation for spoilers is 3mm up
Rudder travel around 35mm. Normal mix is 5mm with full ailerons but thermal mode is 10mm with full aileron.

[Steve P]