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FTFC'18 WWII SAM-7 designed by FoamyDM

FoamyDM

Building Fool-Flying Noob
#21
Thanks all. cg-20%, 2-4° reflex. practice being a tosser ;D get the Glide RIGHT and mark it.

When I watched the video again, It was Nosing over even with full elevator up. Anyway, I should be ready for another go by weeks end.

Plan:
I will build the Simple (B&Y) Wing Version tonight. with steerable rudder and non- retractable 3d printed Gear for ground take-offs. Then take off from a concrete walkway or build a sled...

Updates will be on their way. Sometimes I just don't know what it is with me and CG's... We just aren't friendly. :black_eyed:
 
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Namactual

Well-known member
#22
Yeah, as fast as that wanted to flip end over end it was hard to tell what was going on.

I am sure you will get it worked out.
 

FoamyDM

Building Fool-Flying Noob
#23
Tried a more forward CG on the Front of the Gear, where the CG Calc thing suggests, as a toss glider... and it did OK. It's tough to get a good toss on it. It needs speed to lift and I'm not sure I'm getting it.

CG CALC2.JPG

I'm thinking of making a glide launcher... nah just toss, record and Laugh :D
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#25
As you have given it a glide test and it did not do anything showing a definite CG issue I would recommend that a few taxi tests are in order!

Try getting the tail up, (sorry no tail), and just do little hops and landings to get a feel of where the reflex should be set. Once happy with that it is time to put some air under the wings and aim for a rapid climb to 3 mistakes and check out the control effects. I would have plenty of expo and set dual rates so that I can compare a couple of settings for control throws and adjust after each flight until a best setting is determined.

When the flight testing has been completed it is time to build a second version with all of the improvements, (and none of the wrinkles), oin the original model. Keep the original in flying condition if possible for further developments like retracts and functional rudders Etc.

You are making good progress!

Have fun!
 

FoamyDM

Building Fool-Flying Noob
#26
Thanks Hai-lee. Fluburter - I plan to, however, I was looking to do "A" pack motor versions as that's what I had around in abundance. And the inspiration was a 20 scale version to fly with the k-12 bomber. :D The taxi test was the original plan, but the wheels were too small for the pavement I was on. I am 3d printing some smoother(?) Ones right now. I found an axle from my son's broken formula one racer. I'll turn that into a dolly for a simple version. I have flown an arrow and Viggen very successfully so the controls should be familiar. Putting servos in the simple wing now and I'll build the cart
 

FoamyDM

Building Fool-Flying Noob
#27
I build the Sam-7 "lite". FT Arrow wannabe from the V1.0 build.
Sam-7SVTaped.JPG

2 surfaces, wing tip panels and that's all. I'm going to use this to determine Proper CG on this plane that and a take-off dolly.

Looking around for addition, tips on setting up a custom plane past Hai-Lee's Amazing advice
http://www.foamflying.com/tips.html (Seems like he was FT, before FT.)
 

FoamyDM

Building Fool-Flying Noob
#28
I started but building a wheeled sled... I need to do something more formal.

I modified a few things to this Build, First is I shimmed the bottom of the motor with a tongue depressor piece shoved in the bottom right (looking at the plane) to put the trust line through the top of the wing and a few degrees right to counter torque roll... and tried this out somewhere around 12:30 last night in the front yard. I also added a 500mAh 2S 30C battery to just in front of the back underside of the cockpit and set the elevons to reflex about 10°.

It was a bit dark as I launched it over the grass part of the yard and is seemed to fly a bit (1s), and then wigged out. and it looked like it yaw-spun first and then went nutty. While it's not a flying craft yet. I think I'm on to something. This plane is very squirrelly I think I will attempt to find CoM and CG with string tonight.
 

FoamyDM

Building Fool-Flying Noob
#29
I went out this weekend and saw the "wiggle" action in daylight.

I put about 10° reflex in the rear panels on a 500mAh 2S 30C batt. It appears to have severe yaw instability. So I think if I can work out the instability, I might have shot at making this fly.

I have a video here somewhere. ugh, it's not copying out. The Sam-7 got about 15' out with genuine flight, and then it turned around. I think I'll add a streamer or something just to see it fly and then see what else I can do from there.

Is it sad that I'll call that a win?
I also strapped a Printed Landing gear on the front that I will try tonight.
 

FoamyDM

Building Fool-Flying Noob
#31
I really don't know enough about wing tips to understand how they help the plane except as a drag points and reduce drag from vortex. On this craft they are used for yaw control, but I wonder if I bring the tips rear-ward more, would, that help the yaw stability?
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#32
I really don't know enough about wing tips to understand how they help the plane except as a drag points and reduce drag from vortex. On this craft they are used for yaw control, but I wonder if I bring the tips rear-ward more, would, that help the yaw stability?
First thing to remember is that as a fighter the plane was designed to travel quite fast, rudder drag can oppose such a requirement and therefore the rudders are a little small to keep scale and remain truly effective.

Second thing with wing tip rudders is that the closer they are to the CG, (in the direction of flight), the less effective they will be and the more effected by turbulence or crosswind gusts. In other words more twitchy!

Thirdly, Wing tip rudder incidences MUST be parallel to the direction of flight. If the LE of the rudder is "Toed out" slightly the yaw stability is lost totally and actually the craft will definitely oscillate in yaw as the craft is flying in level flight.

Last thing to consider is mass distribution. On the fighter the mass was more concentrated around the fuselage and so the ease of pivoting the craft in yaw did not require huge drag rudders but with the FB the mass is more distributed. (the wings weigh a greater percentage of the weight than the original craft). This "Spread out weight" makes the rudders even less effective in their original form.

Things to try! I will ignore mass distribution as this requires a redesign and is therefore not going to happen.

1. Fly faster. Bigger motor faster prop or the like.
2. Increase the rudder/fin area to get scale responses and not scale look. An old cheat is to use a clear rigid plastic fin extension that is invisible in flight but gives the increased effectiveness. This can also include a fuselage mounted fin or spin also of clear plastic to give a central fixed fin behind the CG point.
3. Add a degree or two of dihedral to the wings.
4. Angle wing tip rudders slightly inwards at their leading edge (1 or 2 degrees only). Whilst this adds to overall drag it has a great effect on yaw stability in that each wing tip rudder has a drag amount and as a wing advances or the plane yaws the advancing rudder has an increase in drag and the retreating one has a marked decrease in drag. the changes in drag oppose the yaw movement and the craft will re-balance due to the drag differential.

I will ponder on the issue further but my main recommendation at this time are to increase the drag rudder area slightly, (5 to 10 percent only and angle the rudders in slightly and equally on each wing tip.

I hope this helps.

Have fun!
 

FoamyDM

Building Fool-Flying Noob
#34
@ Hai-lee
I like 4 a lot. Makes sense too. I've read about the rudder "cheat" (plastic rear-fuselage fin.).
It would be very easy to miss the rudder fin turned inward a hair on the plan. Thanks, I'll give it a try.
 

Namactual

Well-known member
#35
I would agree with the clear cheater stabilizer attached to the rear of the fuse as being the best option. I would just glue a big foam stabilizer to the back there to get it flying and slowly cut it down until it gets unstable again.

It could not hurt, but as close as your stabilizers are to the CG I am not sure how much toe in would help.

You could also try a gyro to help keep it straight. Again, get it flying with a cheater stabilizer, then once cut down to unstable range, compensate with the gyro.

Keep at it, you will get it flying.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#36
The toe is can be very effective if the Rudders are "Shaped". Unfortunately lost internet here yesterday and so could not respond but I wanted to verify that "Toe In" is what is recommended.

The toe in does not make the plane fly any better except that it has a dampening effect of yaw oscillations so less servo input required to keep it flying straight, (Flight stabilisation or not).

If you have a FT arrow or spear or even a similar flying wing design I challenge to to see what happens to yaw stability if you angle the wing tip fins, (winglets), "Toe Out" by a few degrees! You will find it does get a little hairy especially when doing a low speed approach to land.

I think it will all come together very soon.

Have fun!
 

FoamyDM

Building Fool-Flying Noob
#38
Not yet. If you look through my threads. I am very close to a test on my other two builds. I'm hoping for a taste of success before I try this again. but I know the modifications are simple... I might get the modifications on this done one this and the function testing complete. on the others tonight.

No really good excuse except Life.

This is the beginning of School Year and Scouting season, of which I am a Den Leader, and I have been asked to transfer to Scoutmaster. I just started up a D&D campaign too. The beginnings take about a month to become routine. So some focus is devoted there. As usual, when it rains it pours, and there had a been a large convergence of things this past month. As you've seen I still make progress on at least one of these. But the weekends are rarely when it happens this time of year.

Last evening I flew the mini arrow. and after turning my prop the right way, I was in business. Tried to get FPV working, but abandoned it. (The system works, but I was unable switch successfully).

Much heaped on my plate. However, I'm hungry, and still chugging away at it one bite at a time. Something to post soon, I hope it's success, then refinement.
 

rockyboy

Skill Collector
Mentor
#39
I totally understand the 'fall full plate' modern life delivers. :)

Been proceeding much more slowly than I would like on my projects as well, but not too far behind my schedule. Of course my wife just bought all the equipment, stock, and packaging for a small chocolate company over the weekend, so now I have a new thing to distract from hobby time :)

But maybe I can do up some aviation themed chocolate molds on the 3D printer.... hmm.... this could work!
 

FoamyDM

Building Fool-Flying Noob
#40
What do you mean Maybe.... :)

not to distract further, but which planes are you thinking?
F-117,
Corsair,
Nutball,
and.... Mini Arrow/Kraken