SlingShot Build Thread

[Wayne]

Yep - You need to land a printed plane well.

I think 3 oz of ballast is not enough to be much of a concern, and I also don't expect it to have much if advantage in our racing.

These planes are pretty darn quick and make clean turns. The races will be won and lost in the turns. Getting a tight turn is always key. With us all flying the same basic plane it is going to be a lot of fun.

 

[OribaSJ88]

Yep - You need to land a printed plane well.

I think 3 oz of ballast is not enough to be much of a concern, and I also don't expect it to have much if advantage in our racing.

These planes are pretty darn quick and make clean turns. The races will be won and lost in the turns. Getting a tight turn is always key. With us all flying the same basic plane it is going to be a lot of fun.

That's a couple of ounces per square foot. Worth a try. My versions already approached 14 oz/sq-ft. Perhaps something strapped to the outside for an experiment. How to locate ballast inside for a race is a little more of a challenge. The use of a sleeved pushrod that goes along the side of the fuselage would free some space under the wing. The old school methods would print pockets at the CG that get filled with shot.

 

[Wayne]

I like the DLG method where they put the mass on a stick and slide it back into the CG position and secure the stick. Not sure how well that would work on this model, but think there is room for that sort of thing.

 

[gnichola]

@RafaelAvila what sort of throws do you have set on these?

 

[Wayne]

90 degrees flap. The rest pretty normal.

Mark did some testing and confirmed that extra elevator through when in full crow is not a bad idea. I may make a custom mix that increases elevator when in crow. You would not want all that elevator when racing.

 

[smirkracing2024]

90 degrees flap. The rest pretty normal.

Mark did some testing and confirmed that extra elevator through when in full crow is not a bad idea. I may make a custom mix that increases elevator when in crow. You would not want all that elevator when racing.

Wayne, I have crow on many of my planes (including gliders, hotliner, pylon racers, etc). I usually don't need more than 15-25% down elevator compensation even at max crow to keep the plane level.

That amount of down elevator is within the range I'd use for general flying and possibly even racing (I've not done a lot of racing though, so not sure). Can you share a bit more about either % or degrees of elevator you are using for crow vs for the race flying?

 

[Wayne]

Yeah, we will get you the numbers. I was sort of teasing gnichola with my answer.

For the slope flying it is a good idea to have about 80 degrees of down flap as we use it for glide slope corrections on landing. We sometimes need that massive amount of drag for the spot landings.

We mentioned the extra elevator for the crow setting as it is a bit unusual for this plane when it is in higher lift situations. It is very normal amount in more common lift levels.

I'll try to get some rough measurements from mine and share them here.

 

[zeo0nie1]

Is the 3mm x ~500mm CF tube + a couple steel wires meant for the elevator linkage? If so, How do you secure the wire into the CF tube? Do you have to use epoxy?

 

[RafaelAvila]

Is the 3mm x ~500mm CF tube + a couple steel wires meant for the elevator linkage? If so, How do you secure the wire into the CF tube? Do you have to use epoxy?

Yes, those parts are used to connect the servo linkage to the elevator.
I normally rough up the music wire with coarse sandpaper first, then make a few small grooves in it with pliers. After that, I bond everything together using medium CA glue.
For a cleaner finish, you can slide a piece of heat shrink tubing over the joint once it's finished.

 

[zeo0nie1]

For me, this is the most complicated part, as it requires a bit more attention during assembly, especially with the flap servos.

Yeah, this was too difficult for me. I stripped the mounting screw because I couldn't get a good angle on it.

I ended up E6000-ing the flap servos into place, with some tape around the servo to maybe make them reusable.

 

[RafaelAvila]

that works, thats why i allways mount the servos first

 

[zeo0nie1]

I'm curious how you all set up your controls. I was going to set up butterfly with the throttle stick as input, are there other configurations I should consider? Snapflaps? Flaperons?

 

[Yotaman1985]

Forgive me if I missed it somewhere but for the wing mounting screws, do you just drill the hole out slightly and screw the nylon screw directly into the print? Or am I missing something?

 

[smirkracing2024]

I'm curious how you all set up your controls. I was going to set up butterfly with the throttle stick as input, are there other configurations I should consider? Snapflaps? Flaperons?

I am going to program in:
1. crow on the throttle stick (personal preference is 100% throttle = 100% crow, many run the opposite of that)
2. snap flaps on a switch, but probably leave them on most of the time

That's about it. Not sure flaperons would add much given crow is available. If the flaps had been bi-directional I would also have added full-span ailerons but they're not, so that's out.

 

[gnichola]

Forgive me if I missed it somewhere but for the wing mounting screws, do you just drill the hole out slightly and screw the nylon screw directly into the print? Or am I missing something?

The printed holes have threads, just screw the screws right in there.

 

[Yotaman1985]

The printed holes have threads, just screw the screws right in there.

Ah, mine didnt want to screw in but Ill take another look at them. Thanks

Just looked and my holes definitely dont have threads in them.

 

[Wayne]

We tend to run a tap down the holes if you have one. Chances are you will need to clean up the hole with at least a drill bit to get the screws to go in.

Mixing - I have only the basics and crow on mine.

For racing I use about half the throw I'd use for sport flying. But some care here as crow does eat some of the elevator throw, so flip out of race throws to land.

Play with snap flap and see if you like it. Most planes only want a very small amount of down camber when pulling full elevator. If the plane does not feel better when you test it, then do not use it. I do not recall feeling much difference with this model and snap flap, but it may have been my mixing and the flying conditions that day. With this airfoil I would expect there to be some gains from snap flap.

In general I think folks will be fine without anything fancy, but this is a great class to experiment and learn from, so please give it all a try!

 

[zeo0nie1]

Mine screwed in surprisingly well, I thought that they were pre-tapped. Using a metal bolt with the same size and thread is supposed to work well for tapping it in a pinch.

I've done -100% throttle = full flaperon on other planes, was going to try the opposite here.

No use for just pure, non-butterfly flaps?

Thanks for the help, all. Ail pushrod has dried, just about done.

 

[smirkracing2024]

Mine screwed in surprisingly well, I thought that they were pre-tapped. Using a metal bolt with the same size and thread is supposed to work well for tapping it in a pinch.

I've done -100% throttle = full flaperon on other planes, was going to try the opposite here.

No use for just pure, non-butterfly flaps?

Thanks for the help, all. Ail pushrod has dried, just about done.

I intend to program the regular flaps at very low levels, maybe 15% and 30%, primarily for the purpose of buying time if I get out past the lift. Basically, a (mild) rescue switch. So just adding a touch of camber for more lift, in case it helps. Apart from that not sure what else I'd do with the flaps other than airbrakes on landing.

 

[Wayne]

A camber mix (aka thermal mode) is a GOOD idea. We get about 30 seconds at the start of the race to grab as much altitude as we can before the start of the race. The more you can get the quicker you enter the course.