Rocket Foamie: SkyFun

[iter]

Man this thing is squirly. I only mange two flights between wind calmdown and dusk--but I adjust control rates down after both flights. I feel I may have a ways to go adjusting the rates down.

Ari.

 

[iter]

Wonderful photos from Jim (qquake2k) from the April LUNAR launch at Show Ranch--SkyFun's maiden flight.

Thank you Jim!

Ari.

 

[philip]

SkyFun crashes over the weekend while flying under propeller power.

While testing the autopilot (https://www.diydrones.com/profiles/blogs/ardupilot-mega-home-page), I lose control of the model and it goes in nose-first.

Ari.

Ari, I was thinking of getting an APM2 autopilot for my rogallo glider. Is that the type you were testing? Would you advise against it given your experience?

 

[iter]

I have an APM 1. I have no comment yet on the autopilot itself. The Windows UI is--and I'm asking my friends Chris and Jordi to forgive me--is a real amateur hour. Some settings take effect immediately, some settings take effect when you press some kind of "commit" or "save" button and others still take effect only the next time you reboot the board.

With this in mind, I know of no alternatives that I'm happier with. I'm continuing to work with my APM board to try to get useful flying out of it. Maybe we can share our experience here and get it to work in our application :=)

I now have a field where I can fly regularly (https://www.sccmas.org/) so I expect to make more progress. It's hard to make progress when you get one or two flights in a month! The new field hosts, inter alia, turbine R/C jets, so my gliders look benign there.

Ari.

 

[iter]

BTW, I love your Rogallo glider. One thing that pleasantly surprises me about it is the vertical CG location. What I hear is that Rogallos are very sensitive to vertical CG location, which is how most Rogallo implementations put the weight on a pendulum low under the wing (hang gliders, trikes, etc.). Yours seems to work fine with the CG quite high up.

I have several Rogallo concepts I'm kicking around in my head. One of them involves an umbrella mechanism. A stick umbrella has most of the parts to open a Rogallo, including a spring and spars. It just has too many spars and fabric that is on the wrong way :=) I'm waiting to finish my L1 flight-test program before I actually build this though :=)

Ari.

 

[philip]

BTW, I love your Rogallo glider. One thing that pleasantly surprises me about it is the vertical CG location. What I hear is that Rogallos are very sensitive to vertical CG location, which is how most Rogallo implementations put the weight on a pendulum low under the wing (hang gliders, trikes, etc.). Yours seems to work fine with the CG quite high up.

Ari.

I am trying to source another g80 engine for a second launch but it is winter here and the launch area is windy and muddy. The short glide time was disappointing but I hope that was not some fundamental flaw in the design but simply because i didnt trim the v-tail properly. I have removed some nose weight and ballast and am trying to source some lighter cardboard tube to save weight on the booster. Ultimately would like to launch it HPR with an onboard autopilot and camera. An umbrella mechanism could be promising with some modification but I used kite material for the wing and carbon fibre for the spars.

 

[qquake2k]

Wonderful photos from Jim (qquake2k) from the April LUNAR launch at Show Ranch--SkyFun's maiden flight.

Thank you Jim!

Ari.

You're very welcome. It was an awesome flight!

 

[iter]

I am trying to source another g80 engine for a second launch but it is winter here and the launch area is windy and muddy. The short glide time was disappointing but I hope that was not some fundamental flaw in the design but simply because i didnt trim the v-tail properly. I have removed some nose weight and ballast and am trying to source some lighter cardboard tube to save weight on the booster. Ultimately would like to launch it HPR with an onboard autopilot and camera. An umbrella mechanism could be promising with some modification but I used kite material for the wing and carbon fibre for the spars.

You may want to test the glider portion without the rocket. We already know that your boost and deployment systems work--there's nothing to gain from testing these again. I find that trimming gliders on the way down from rocket flight is challenging on two counts: one, I can only get a few launches in a month; two, I only get a few seconds (sometimes a minute) of glide out of a boost flight. It's very difficult to trim a glider on a budget of a few minutes a month. A regular R/C model might take 3, 10-munite flights to trim out. At 5 minutes a month, this stretches into half a year.

You may want to do one of two things: either attach an electric motor and fly is as a motor glider, or get someone to tow you up with a bigger R/C airplane. I use electric motors, but if you have a friendly local R/C clud,I encourage you to reach out to them.

Ari.

 

[philip]

You may want to do one of two things: either attach an electric motor and fly is as a motor glider, or get someone to tow you up with a bigger R/C airplane. I use electric motors, but if you have a friendly local R/C clud,I encourage you to reach out to them.

Ari.

That is a good suggestion. It has taken a few years to get to this point. The whole process of building and sourcing parts then having the right opportunity to launch is very time consuming.

 

[The Rocket Kid]

Between dry summers and California politics, rockets are hard in the San Francisco bay area.

Tell me about it:dark: The politics are wrose than anything out here:eyeroll: Thats why I launch with TCC. You bet it's a drive but it's worth it.

 

[iter]

[video=youtube;k6tptx4_b6o]https://www.youtube.com/watch?v=k6tptx4_b6o[/video]

First flight at the new field. I'm happy with the launch and boost trim. I strip the gears on one of the servos on this flight and the model dives nose-in. (It's hard to see in the video--the model gets small quickly)

Damage is minimal (mostly the fore cardboard tube and nosecone) but servo stripping precludes additional flights today.

Initially in this project, I worry a lot about stripping servos. After half a dozen of trouble-free flights, I decide that servo stripping is unlikely. Then I strip a servo :=)

In addition to waiting for new servos, the drag is that I glue on these plastic servo arm protectors. Now to get to the servos, I must remove them and glue them back on.

I'm happy about how little damage the model incurs in this crash.

Ari.

 

[iter]

Work... it gets in the way of rocketry. I finally get to repairing the servo. Here's what it means to strip a servo--a tooth is missing on one of the gears.

My plan--after replacing the servo--is to use a shorter arm on the servo (moving the pushrod closer to the servo axis). I'm using only a small fraction of the available servo travel, the glider being so sensitive. Using a shorter servo arm means I use the whole available range of motion and decrease the stress on the servo at the same time.

Ari.

 

[R&R Model Aircraft]

Work... it gets in the way of rocketry. I finally get to repairing the servo. Here's what it means to strip a servo--a tooth is missing on one of the gears.

My plan--after replacing the servo--is to use a shorter arm on the servo (moving the pushrod closer to the servo axis). I'm using only a small fraction of the available servo travel, the glider being so sensitive. Using a shorter servo arm means I use the whole available range of motion and decrease the stress on the servo at the same time.

Ari.

Use only metal gear servos. They are a very small weight penalty for the strength they offer. I use only Hitec metal gear servos on the Delta and Gamma Star models for just this reason. HS-82MG for the Delta and HS-65MG for the Gamma. Never had an issue and we fly under full thrust for some aerobatics (well, I don't. My friend / test pilot does as he is far better than I am )

David

 

[iter]

Thank you for your advice David. Your kits are a great inspiration to me. I'm looking forward to the Switchblade!

I've already covered up the servos on the Mk4 (the servo covers are glue-on, hard to get to). I'm also repairing the larger Mk3 (photos at the top of this thread). I might replace /its/ servos with the HiTecs you recommend.

This is the first servo I stripped in my 20-year R/C carrier. My feeling is that some builders use metal gears as a crutch. Most cases where I see people strip servos are sloppy designs. This is certainly the case with my glider. Originally, I use the default outer hole on the servo horn and adjust rates down in the transmitter. I eventually get aileron rate to 30% and it still feels twitchy. The real solution is to use a closer hole and full travel. The hole I use now is over 50% closer to the shaft, and I get the same aileron travel as before with less than half the torque requirements and higher resolution. If I strip another servo on this glider, /then/ I go to metal gears :=)

Also, I like to avoid flying the glider under boost, if I can at all. I interfere if I see it going too far from vertical, otherwise I let it fly itself up to apogee. My skills are far below your friend's, and I the faster it's flying, the harder it is for me to control.

Ari.

 

[R&R Model Aircraft]

Also, I like to avoid flying the glider under boost, if I can at all. I interfere if I see it going too far from vertical, otherwise I let it fly itself up to apogee. My skills are far below your friend's, and I the faster it's flying, the harder it is for me to control.

Ari.

Download the Delta Star manual from my website and you can see how we have it setup (R/C wise). We use a combination of exponential control and dual rates. Also, on boost, we use the throttle control as kind of a large trim control for the elevator. The Delta Star (chime in here anytime, John :wink has a recurve airfoil to help with pitching that sometimes requires a bit of finesse depending on wind conditions.

First time I flew Delta Star (John Boren's original kit), it was "Holy S***!", hence the use of settings I could deal with.

Good luck!

David

 

[iter]

One successful flight today on a D12. My guess is 100'-150' of altitude.

Even with the new, short servo throws, the glider seems twitchy at 100% aileron rate. If this trend continues, full displacement on the stick is going to produce about 1 degree deflection of the ailerons :=)

No photos of the flight, but here's a photo of my new nosecone. Fun fact: Estes 34mm nosecones have an inside diameter that exactly matches the outside diameter of LOC 29mm tubes.

Ari.

 

[cwbullet]

Pretty neat. I had one but the motor melted the foam.

 

[iter]

Two flights today on D12s at SCCMAS.

I have two elevator trim settings--one for boost (neutral lift) and glide (up elevator). I even have a sticker on the fin to remind me to use the neutral-lift setting on takeoff. On the second flight, I realize immediately as the glider leaves the rail that the elevator is on the glide setting. The model performs two inside loops what seems like inches off the runway. I manage to pull out and land it safely, if slightly off centerline :=)

I'm happy to report that even though these wild aerobatics, the servos are OK. The closer holes seem to be working.

Ari.

[video=youtube;hPvYUhtlpNU]https://www.youtube.com/watch?v=hPvYUhtlpNU[/video]

 

[kjohnson]

To avoid having to rely on stickers that are on the model (that may be 50 or more feet away) to remind me of boost settings, I set up my models so all the switches flip forward. All it takes before launch is a quick feel or look to check. It's now part of my pre countdown routine to feel the switches.

kj

 

[iter]

I like your idea kj.

My setups are "forward fast, back slow." Throttle and elevator are obvious; flight mode forward is zero lift, flight mode back is up elevator; high rates forward low rates back. This is where it breaks down, as I'm taking off on low rates.

Ari.

 

[kjohnson]

Reading that again I left out something.. I set it up so that on boost all switches are forward. Very quick to flip them all before the count.

kj

 

[iter]

Reading that again I left out something.. I set it up so that on boost all switches are forward. Very quick to flip them all before the count.

That's my understanding of your original post.

I have ignition on the throttle stick, so almost everything is forward for launch--except dual rate switches.

Ari.

 

[iter]

Five more flights this morning at SCCMAS; 2 on D12s, 3 on D11Ps. D11s surprise me by giving the plane noticeably less oomph on the way up. They are both nominally 17-18 Ns, but the boost is visibly slower and apogee is lower on the D11s.

I'm happy that even though I have a lot of room for improvement in my landings, the glider needs no repairs after the 5 flights today.

Ari.

 

[iter]

I come home to find a huge box on my doorstep. What can it be?



Lots of foam...



These are wing cores for the upscale version! Thank you https://www.flyingfoam.com/



Love the compound curve intersection lines. These are the result of dragging a hot wire along fairly simple curves. I recoil in horror at the thought of having to draft lines like this for a built-up wing.



Currently-flying wing for scale next to the L1 ship. That's a 56mm body tube. 43" wingspan, 35" root cord.



Ari.

 

[JoeG]

Cool!!

 

[Minimum_Wage]

Looks really cool. What kind of foam is that?

I love the idea of using a body tube as the fuse. I have a R&R Gamma Star kit on my workbench but would love to make a foamy like this to get some flight time on before trying the balsa version.

Mike

 

[iter]

The Gamma is a beautiful kit.

The foam is "1# EPS," as in 1 lb per cubic foot.

Each core weighs 270 grams. Together with the nosecone (105g) and the body tube (200g), the components in my picture weigh 845g. If I want to stay under the FAA definition of high power, I have another 655g for covering, electronics and motor. H54 (target motor) weighs 209g, so that leaves just about a pond for the rest of it.

Feels doable.

Ari.

 

[TheAviator]

If you're looking for a test motor for your L1, the CTI G54 is an awesome motor and nearly identical to the H54. The H54 has another 6 or 7 N-s of impulse.

Can't wait to see the big one go. Good luck!

 

[aerostadt]

I come home to find a huge box on my doorstep. What can it be?

Iter, You've got camber! I've been just cutting flat foam with a hot wire. Do you tell the company the kind of air foil you want?

 

[iter]

Brian--I have two G54s sitting in a box alongside an H54 :=)

Aerostadt: Yes. You send them a drawing or the planform you want, the tip airfoil, the root airfoil (they can be different, or at different angles for washout), what type of foam you want and they cut it for you.

Incidentally--the airfoil is NACA0015, 0 camber. I worry more about symmetry on the boost than L/D on the glide, so I go with a symmetric, 0 camber airfoil. I care more about structural integrity than L/D, so I make the airfoil thick.

Ari.