Building a WEIRD RC Plane... Will it Fly? 

I just custom made a RC jet. How do u calculate were the cg should be?

@@Aerospace_Engineering_Noob 25% back form the leading edge, if the wings are swept from the smaller outer end of the wing, go 25% back from there and then draw a line across and then that’s where CG is

Your problem is that it’s a V tail that is quite complicated rather try a normal tail @michaelrechtin

Try to build a Q200 QUICKIE for your next plane. VERY ODD BUT COOL AIRPLANE.

@@Gabebuildsthings1234or go crazy and make it neutral

doubt that's the issue since they were as large as the old wings

Actually part of the problem is rough air from the rear motor. If he made the fusalage longer and then pushed the tail further away from the blades is would help a ton. Wider tail surfaces might help a bit also but not so much longer. I think the largest issue is they are too close to the front of the propeller. Many pusher airplanes are more rear wing and canard style. But with this style it needs a bit smoother air and longer fusalage to give it a longer lever movement

Combined with the camera sticking out causing huge drag on one side, I'd say that's pretty much the cause.

V's too small for short tail length.

@@newmonengineering The tail doesn't see the rough wind of the rear motor because this plane doesn't fly backwards.

Don't let go, never give up it's such a wonderful life

lmao

"If there's a hole, there's a goal." Wisest words ever said, now said by me 17:50pm 31/05/2024.

ouch

I mean it fits the swiss cheese model

That would be very cool..

My eyes got wide and ears perked up when I heard the words 'CNC foam cutter'

Bro just casually said "...on my CNC foam cutter" like it was nothing 😂. I'm more interested in that than the plane now.

I once tried building something of similar proportions, and it definetly needed more surface area in the rear. maybe even add a third smaller fin on the bottem for more yaw stability.

I do agree! I'm not an engineer but I mess around a lot with foam thingies, v tails are weird, he definitely needs a larger surface!

Why would you do that with the push puller? Sounds like a bit of rockets fallacy

​The two props aren't stabilizing each other but creating the yaw that he notices. Although this won't fix it. Maybe rudder trim needed but he doesn't have a rudder. ​@@BeefIngot

@@shadmansudipto7287 Not sure you got what I was saying. Im talking about power.

Everything said above. A flight controller is an aid it still needs a correctly weighted and balanced plane to fly or it just masks the problems.

How will you, (as a hobby guy) calculate the area required for control surface ? Any thumb rule. Pls let me know

Yea that’s a pretty good summery I recon. A couple of additional notes, the v tail looks to small for the aircraft which could be the source of some of your control issues, and I wonder if there is some funk aerodynamics fighting each other a combination of the prop at the front and the pusher at the back very close to the v tail. Also worth slimming down that fuselage a fair bit too.

@@fliteanalysis4927 Start with building plans that you modify slightly. Orientate yourself on the weight and dimensions of existing model aircraft. Once you have enough experience, build your own models. And light models always fly better than heavier ones.

V tail angle is a combination of the needed horizontal and vertical volumes. There are formulas to help calculate the needed volumes depending on the type of plane. Then there are formulas to help with the conversion from conventional tail to V-tail... you can end up either with 100-110deg or the other way around at 80deg... Having 2 rotating masses at each end sure will increase drastically the inertia of the plane making the tail volumes calculation even more critical. Plus everything else already mentioned

a real pleasure to find you here, a big hello from France and lots of thanks for your fight against the absurdity of certain regulations

@@sylvainponchelet4188 Thank you for the kind words. I shall continue the fight!

The pusher engine was just aft of the wing, which also changes the CG.

en.wikipedia.org/wiki/Contra-rotating_propellers Thats good for efficiency

@@nork7045 dont all of those have both propellers at the front of the plane? what im saying is having 2 propellers in front of each other with such a massive gap means that theres enough space to create turbulence, which would probably reduce efficiency, right?

@@theanomynusguy well, it probably isn't as efficient as an actual contra prop but the 2nd stage of contra props get turbulent flow too. You can only get laminar air flow with very specific conditions and geometries. For that matter all pusher planes' props get turbulent air from the body and wings

@@nork7045 yeah good point

they also have to go through the accelerated air

This. The gyroscopic effects of the props lead to this yawing effect. Similar to prop walk on boats but twice. And without a bigger, vertical rudder there is not enough yaw authority

You're both incorrect. In an aircraft like this, the P-factor (the combination of four different forces all combining to create a yawing moment) is balanced and counteracted between the two props. This is no different than a contrarotating arrangement seen on some Griffon powered warbirds which have no P-factor to speak of, they're just separated on either end of the aircraft rather than being stacked together. The problem here is that unlike a Griffon powered warbird, the two props are not designed for this and are not producing equal amounts of thrust, so the benefit from having contrarotating props eliminating P-factor is not going to be realized as apparently. One of them is in clear air spinning slower and developing ideal thrust, the other is in dirty accelerated air and isn't able to develop as much. Thus, you have a discrepancy between the two props, leading to a yawing moment. The V-tail is compounding this problem, and with a conventional tail arrangement of adequate authority, the P-factor discrepancy would be a non-issue.

​@@Skinflaps_Meatslapperthere is actually a major difference with Griffon engines. On the Griffon, both propellers are attached to the "same place". Here, one is attached facing front and the other facing back. In this configuration, if you look closely to gyroscopic precession, they are actually piling up. If you look each propeller from the motor's mounting holes, they are both spinning CCW. To not have this problem, the rear motor would have needed to be mounted the other way i.e. facing front but it's not possible 😉

@@Skinflaps_Meatslapper i like how you said we were wrong then proceeded to very clearly explain why we are correct...

@@LBJHJP50 If you actually understood and followed along with anything of what I said, then you'd realize just how contradictory your statement is...but you don't, and you're getting completely separate things mixed up together in addition to not understanding the aerodynamics and physics of this in the first place. When you combine your very limited understanding along with your smug attitude, it doesn't really matter what I say after this, you're going to think you're right anyway. I have no interest in explaining what you're not understanding, you won't doing anything worthwhile with it anyway, so enjoy wallowing in that delicious Dunning-Kruger effect with your newfound buddies.

Also are you sure not one of the propellers just act as a break. If they rotate at the same speed it may not actually help. They are not close to each other so I doubt you get the benefits that usually counter rotating propellers give. It also looks like it’s too heavy, not just unbalanced. Further are your motors angled as they should, I suspect the rear engine is just making things worse if you have mounted them straight. You might need to double angle of thrust compared to how it’s normally setup. Depends on the engine rotation whether you should angle front motor left or right. Normally a one should also angle them a bit downward. However with a rear engine messing with all this I can’t say for sure how you need to set it up. Begin with disabling the rear engine and make engine mounts for the front motor angled as appropriate. When you get it to fly with just the front motor running start experimenting with the rear motor. PLA is heavy. Don’t print parts that use any unnecessary material. If you can get away with one wall don’t print more. If you can design a model you can print in vase mode. Do vase mode. I have not yet tested lw-pla but I have a few rolls waiting for some prints.