Mini hopper

Files for my planes:
iforce2d.net/sketches/stacked...

[@iforce2d]

Disregard my 'advice' about the CG check, I'm not so sure about that now.

[@marc_frank]

i think your technique "measures" the center of pressure?

[@boxlessthinker1973]

Looked cool though! I thought it was a static measurement but I’m no expert!

[@jakeharms1386]

I think it's pretty good advice. At the least it should be a good rough start. Also if you want to fix the "keeps rolling" you can add some dihedral and/or some sweep to your wings. More vertical surface on the tail (or a more acute v-angle) would help too, although that's sort of a more secondary effect.

[@marc_frank]

@@jakeharms1386 at least you know something is very wrong if the tail leads ... 😅 fine adjustment most often done via flight feel anyways

[@Zagitta001]

I find it really funny how Chris spent a ton of time, effort and money on making his CNC to very tight tolerances.... Only to machine nothing but foam 😂

[@rjung_ch]

I like the red rings you add for a second on scene switches, really helps out. This is a sweet little plane, well, 1.5m little 🙂 Cheers and thanks 👍💪✌

[@big5astra]

At 14:00. It would seem that all planes (of this type of design), when you hold it under the wing at the balance point, will always lead with the fuselage when moving it up or down. The reason is that the horizontal stabilisers at the back of the plane will have greater resistance to moving through the air when you lift it or drop it. And the lever of this force relative to the position your are holding the plane under the wings, will tilt it so that the nose leads the way when moving it up or down. And I don't think one can deduce any sort of resultant aeroplane stability etc from this phenomenon. This type of movement will occur even when the balance point is way off the correct CG position.

[@AerialWaviator]

The Mini-hopper has the look of a wise-owl head-on(🦉1:25). I really like the looks of both twin hopper designs. Your CNC foam slicing technique is definitely an order of magnitude more advanced with this hopper. Result is almost like a professionally manufactured kit. A useful tip (15:05) for ensuring the centre of aerodynamic area is behind the centre of mass. Learnt a similar technique when flying model rockets (where big noses can be bad). Another way to find the centre of aerodynamic area is cut out shadow plane view (2D) from stiff paper, or cardboard. The centre of mass of this cutout will closely align with where aerodynamic centre should be (ie: find the balance point). Better nut safety. Similarly a side view 2D cutout) can be used to determine yaw stability. (ie: will it weathervane when moved sideways) You might need to configure a control mix for rudder and elevator (20:25), and/or for throttle-pitch coupling (22:25). Flight on 2nd day looked so much smoother. Speedybee currently offering a U$35 F405 wing flight controller that seems to be good value. (is Ardupilot capable) A side-effect with V-tails related to roll inputs is control deflections create opposing torque forces to that of ailerons when rolling-in/out of turns. This can create a lag in yaw-effect as turns started, stopped. With an inverted-V (/\) the torque forces of tail and aileron control surfaces align instead of oppose each other. Effectively the roll-rate is a bit better (/\) / less (V) for the same control surface area and same amount of deflection. Inverted-V's tend to tricker to deal with on takeoff/landing making them more prone to damage.

[@marc_frank]

if you had told about where you bought the 30mm foam, maybe that would have created more demand which would have meant that they wouldn't have taken it out of the inventory? 😅

[@robertstark3326]

That is a beautiful plane and a great design and build video. I like old-school construction techniques but have 25 years of experience working CNC mills so I understand completely the desire to use it. What a great project. The plane has such graceful lines I love it. Happy flying.

[@Pete-tq6in]

Adverse yaw seems to be the cause of your bank and yank problem. If you've not done it already, program some more differential movement into the ailerons, more up movement than down. Also, try feeding a bit of rudder in when you roll. Pro-roll rudder as you enter the turn and once the turn is established, neutralise the ailerons and balance the turn with rudder and elevator. Some people like to program the rudder to operate with the ailerons but I like to keep them separate because that means that axial rolls are more doable. With regards to the pitch coupling with throttle, try changing the thrust-lines of the motors. If you're getting pitch up on throttle application, add some downthrust.

[@TheRoulette77]

great to see another craft up and flying ! great vid brother

[@tomsunhall]

rReally nice models, love seeing the evolution of your shape. Very elegant!

[@FPVBENNY]

The plane has a beautiful shape, great work!!

[@nige5572]

Nice build! You might try programming some differential into your ailerons, helps a ton with the adverse yaw, or the "wanting to go straight" tendency when you bank.

[@iforce2d]

For now the ailerons are on a y-cable, but when I put a flight controller in I will use differential aileron

[@mike_oe]

20:10 that is what V-tails do due to the inherent adverse yaw of the lay-out. Inverted V-tails helps yawing, but they are not a good choice for your fuse/mainwing setup. If you're doing a twin motor plane, you could consider dual tail booms integrated into the nacelles. 110' is the normal angle for the inv. V-tails to get a balance between yaw and pitch stability.

[@KF99]

It’s nice you have new projects and ideas to build. Mini Hopper would be quite similar to my 2022 twin engine plane, I hope it would fly again soon after repairs.

[@TheDIMONART]

Chris, some steel wool and scotch -brite will help you to remove rust from HGR rails and ball screw. And don't forget to grease them weekly. HGR rail guides are very sensitive to high humidity and rust.

[@RJMathiyazhagan]

This is exactly what I’ve been waiting for!.Great video 💥

[@rjung_ch]

Wow, that pilot nearly got you there Chris 😉

[@kermets]

Thats a great size plane to whip out for a quick fly after work etc......good job

[@senorjp21]

Wow you live in a beautiful place

[@markgreco1962]

Another great video

[@FarmerFpv]

Twins always fly great. My favorite two planes are twins. The Twin Otter and The Twin Bronco. I have them in 1.9-meter wingspan and also have 900mm versions. Both are incredible FPV platforms. The Mini Hopper looks great! I would put your Vtail more vertically. It will soften the pitch and help the nose go around in turns. when yanking and banking. The V-tail seems rather flat which gives more pitch control and less roll and yaw control. I was always told to go a few degrees more vertical on my V-tail builds. It has always had better yaw coupling in turns.

[@mattiaslaserskold137]

Love your videos!

[@boxlessthinker1973]

Great job!!

[@yusuftasdemir6722]

You have great works, you are doing very successful work, congratulations.

[@Mike500912]

I'm thinking the susceptibility in roll is due to the lack of dihedral (?)

[@Pluzzie]

Cool plane! especially it's a v-tail

[@6227836jschulz]

I like to mix some water with Polyurethane Glue. It foams up and hardens fast, which is good for filling up those spar channels.

[@6227836jschulz]

I tend to mix it with a popsicle stick and smear it in.

[@iscluiscaduk]

beautiful airplane.

[@theflyingfool]

I think the roll sensitivity is due to the very fine dihedral. In essence you have a neutral wing that will be keen to continue rolling until you input a *little* anti-roll aileron. I flew an anhedral wing once and boy was it twitchy! I couldn't take my eyes off it for a millisecond and had to fly it all the time, constantly correcting. Very tiring... Thanks for the video and it was interesting to see the build as well as the test flights.

[@EnglishTurbines]

Looks great....It will probably behave better once the FC is onboard. The giro will help smooth things up....What brand are those tiny quad ESCs rated at amp wise?...😳😏😳🇬🇧

[@iforce2d]

The ESCs are 30A rated. Can't seem to find them available these days which is a real shame because they were super cheap and have never let me down. There's a screenshot in this video at 2:13 if it helps. kzbin.info/www/bejne/mWfEdKqJfdeSn9Usi=2Za26qMn86ODSwi1&t=131

[@EnglishTurbines]

@@iforce2d URUAV.....I'm amazed they are driving those big motors rated at only 30 amps TBH. Thanks for the info. I'd like to try some digital ESCs on my planes and I need small, light ones...🤔👍😏🇬🇧

[@xsbiggy6349]

Might be a good idea to place a few navigation leds on it so if does dip below the horizon you can spot it a bit easier

[@theafro]

sounds and looks like excessive sideslip might be the culprit for the handling issues, and would be more noticeable on a turbulent day. the v-tail doesn't help, they can be pure evil sometimes!

[@andrewmack4830]

Thank you. Very interesting. How do you get the time to undertake such wonderful projects?

[@Kaglorna]

when all mass is concentrated under the wings, the pitch will be very sensitive because the inertia from the CG to keep it going straight is so small. That with short tail makes it squirrelly. And since the center of gravity is symmetrical with the wing height, it will just roll and not bank when you roll. A higher mounted wing and longer tail to allow for the battery to be more forward would fix that.

[@jeffbluejets2626]

As quoted previously, checking the cg while flying is easy enough. Fly around 1/2 speed and trim for level flight. Enter 45 degrees down flight ......... if nose pitches up , cg too far forward(nose heavy)....if nose pitches down, tailey. Preflight can be done using wing high points on the chord. Tapered wing takes averages. Close enough but I always like to make things a bit nosey rather than tail heavy for first flight.

[@RobisonRacing68]

It's a pretty bird Chris! It's also nice to see you still flying with the FlySky transmitter. Is it the same one it's always been? No, couldnt be. Looks like a newer model. Is the "rp;; and keep rolling" because of ninimum dihedral? Anyways, I like this one. :)

[@paulking7019]

Have you tried changing the rotation of your props? Obviously this is not a twin boom or a P 38 lightning. The XP-38 the propeller rotation was initially inward, elevator buffeting began to appear & the rotation was reversed to outward rotating to try to alleviate the problem. (Even my 1700mm P-38 has its props rotating outward like this).Your props look to be rotating inward (top of the prop arc rotating inward to the fuselage). Maybe try outward. It might direct some air flow outward and away from the flat V-tail. Moving your battery forward might help a bit too. When you add the FPV camera to the nose, you might have enough weight forward to tame some of the pitching.

[@jakubzabocki6182]

i'm inspired to make some like that, its very nice

[@aviatrix2]

You need to add a degree and a half or so down thrust on both motors to correct the pitching up with throttle. As long as you keep turning both props clockwise, you will need a similar amount of right thrust on each motor to correct the yaw thrust effect. However, the yawing thrust is easier to correct if you reverse one of your motors and run it CCW with a left-hand prop.

[@darkobul1]

That with drill bit was great. Why not on foam.

[@PiefacePete46]

My first reaction (before he started cutting) was "twist drills have no side-cutting rake built into them". Then I woke up... on something soft like foam it's not needed! If you were prepared to sacrifice a drill bit, you could even grind a ball-nose end on it.

[@christopherleveck6835]

Give it a couple degrees of actual dihedral and youll flatten out that roll tendency.

[@marekkonieczny8492]

Great video, thank you. Could you tell us what airfoil profile you use, what wing angle of attack and what weight of glass fabric to cover the model? . Enjoy your flights

[@iforce2d]

Search for "NACA 4 digit airfoil generator" and try these numbers: T/C: root 14%, tip 11% Camber: 2% Max camber position: 45% About 2 degrees incidence between wing and tail, although this is small enough that you could just make it zero and trim the elevator. I use 50g/sqm glass and West Systems epoxy.

[@alttabby3633]

Another great looking plane! If your looking for something to put in the description, I would suggest a link to the cad files.

[@FPVBENNY]

Did you try if the CNC also works with EPP? It is not as stiff, so it might be more difficult.

[@AndrewNewton]

What is the V-Tail angle? Looks quite flat like the AtomRC Swordfish

[@PiefacePete46]

Like @rjung_ch, I think the red rings are a neat touch. That's a nice looking aircraft... sad to hear it doesn't give you the "Jolly's" you wanted! I have always liked the look of V-tails, but they seem to add some unique characteristics, even in full sized aircraft. Could it be something like that, which might be very frustrating to tune out? @AerialWaviator has some more definitive thoughts. I don't got no 'sperience wth them... only hearsay. You've got to grab those flying opportunities when you can... the weather this summer has been the most erratic I can recall. Thanks

[@StewardsNotes]

Super cool design! I'm wondering what software you use for preparing your GCODE for 3D operations?

[@iforce2d]

Fusion 360.

[@chrispychickin]

ill bet the throttle pitch couple would be helped a great deal moving to a 6x5.5 or 7x6. bigger disk area (2x8" dia is huge IMO) on these small twins seems to lead to a lot of ballooning when combined with how much power even little 2206s are able to pump out. Possibly needs a degree or 2 of down thrust also. But it looks like you've got a great design, with the need for a couple tiny tweaks. What's the incidence setup? that rather flat v tail + short coupled tail is possibly the reason for pitch sensitivity - a big horizontal stab to wing ratio. Would also play a part in the "rolling into the turn" issue (though i expected the vertical fin underneath would have negated any of that... they don't always behave predictably in that position in my experience, something to do with aerodynamic shadowing, or dirty air off the wings downdraft?

[@qwertasd7]

Can it be mader under 250 gram regulation (smaller) with fpv?

[@zinahe]

Hi, thanks for sharing. How did you decide how far apart the propellers should be placed? Cheers,

[@iforce2d]

Ideally you want them as close to the center as possible. So figure out what the max prop size you'll be using is, and just place them so that the props will not hit the fuselage.

[@GNARGNARHEAD]

I can't help but wonder how'd it go with differential thrust steering and just using the tail for pitch 🤔

[@EnglishTurbines]

I can tell you, useless. It's an iNAV idea on twin motors and frankly, it's a bad one...😳🙄🇬🇧

[@dwiranu5394]

I'm still curious about the location of this runway on Google Maps. Any clues? Landmark or whatever?

[@patrickradcliffe3837]

Instead of using CF tubing you should look into using CF strips. It will give you a stiffer wing and not having to cut a gaping hole for the spar. 13:28 you should already have idea where the CoG should be by what airfoil you using and the center of lift of the airfoil dictates where to start for CoG 17:26 I'm guessing here that you V tail is to flat just from a mk1 eyeball sees. 20:11 you need to setup aileron differential and mix in some rudder what happenings is when you roll in ailerons the high wing has more drag causing adverse yaw.

[@wideyxyz2271]

❤💥💫

[@kalle123]

bl motors with 2000kv. That is hot.

[@iforce2d]

They did get kinda warm actually. Prices these days are making me just use whatever I had sitting around.

[@user-oy2oh7yp3w]

Ребята вы просто молодцы! Как можно с вами связаться?!

[@obennett100]

How about RC the dolly with a return to home function?

[@KwongKan]

I think you can get away with waaaaaaaay smaller props for the size

[@Smt_Glaive]

Ha are you talking about? The prop size is perfect

[@iforce2d]

Yeah I think 6 inch props would be sufficient.

[@Dread-I-Productions]

:)

[@BlixYTube]

Hi

[@Sp3ktral22]

Your planes roll because you don't have much dihedral designed and built in to them.

[@knowledgebyte]

Agreed. Either add some swept tips or a new wing with more dihedral. That flies exactly how say a Chris Foss Phase 6 or middle phase aerobatic model would fly. Invert it and see how it handles. More of a fast slope soarer model. I bet without the motors it would make a good slope soarer for windy days.

[@abruptlyblunt]

right now banggood has the NX3 3D Gyroscope Flight Controller on flash sale for $13 usd and the HobbyEagle A3 EVO 6-Axis Gyro Flight Controller for $24 usd, personally i'd rather spend a few dollars on a fixed wing flight controller instead of hassling with scavenged drone controller on a fix wing......

[@iforce2d]

Almost all my FCs are Omnibus F4 pro which run Ardupilot, so they can do both equally well.

[@lasersbee]

14:50... With the Plane horizontal It seems to me that it is air pressure pushing on the Larger tail surface area that makes the tail lag behind the finger (CG) points. I still don't get the idea of that test. Seems that any plane held at the CG and horizontal will exhibit the same effects.

[@PiefacePete46]

It is a checking balance of inertia at the nose vs air resistance at the empennage.