My son’s self-designed airplane (the Cow)

[Foamforce]

My son is 11 and he’s been watching me build for the past few months now so he wanted to do his own design. He calls it “The Cow”. Most decisions are his based on what he’s seen me do and I tried keeping my mouth shut as much as possible, although I talked him out of more than a few bad and overly complicated ideas. It turned out as a conventional low wing design. I’m not sure how the single bevel wing will work out. I predict that we’ll get it to fly, after a few adjustments, but that it will have low rudder authority. We’ll see! What are your guesses as to the outcome?

 

[MrClean]

Ought to work, If the dihedral is enough. My oldtimers is acting up, can't remember the name, something like K-pal. It's not Long Haul but this one seems to be named that. No other info and shoot, on pinterest.

 

[MrClean]

AHHHHH, google image search.

D-9 Jodel
D-9 Jodel Wikilink

 

[Foamforce]

Thank you, that’s very cool! I’m going to show him this tomorrow. It’s neat knowing that there’s a similar real airplane out there.

 

[Foamforce]

Speaking of which, the dihedral is a pretty high angle, but not very long. In glide tests and manually setting the rudder, it seemed to turn as expected, but not super fast. I figure if it’s lacking roll authority, he could start by making the rudder bigger, or just go ahead and add ailerons. He’s learning TLAR engineering.

 

[quorneng]

Gliding is one thing but my guess is you will find the motor torque an significant issue with such limited roll authority from a limited dihedral low wing and short tail moment for the rudder. It may require significant right thrust on the motor and with such a wing section down thrust as well.
We all learnt by lots of trial and error.

 

[Fred Pena]

I think it could fly, may not fly great but an awesome attempt from an 11yo, if that was my boy Id be quite proud of him-

 

[MrClean]

Before striking everything and adding ailerons, add dihedral in them wingtips. I've seen model Jodels fly fine with rudder and elevator only. The flat poriton of the wing is a little shorter but try the dihedral first, then shorten the span on the inner panels. Man, I wish this was an all foam wing. Would make chopping so much easier.

 

[Foamforce]

Here are a couple more photos. Thanks for all the suggestions! We’re going to try it like this and then make adjustments based on how it goes. We’ll be considering all your suggestions and we’ll post a video for diagnostics!

 

[Adui]

Need flight reports!! THAT is cool! I wish my kids had such interest at that age (I really did try in this hobby. Not so much in many others I should have, but I tried with RC)_

 

[Tench745]

Here are a couple more photos. Thanks for all the suggestions! We’re going to try it like this and then make adjustments based on how it goes. We’ll be considering all your suggestions and we’ll post a video for diagnostics!

Something to remember, dihedral gives the plane roll stability but more importantly, it allows something known as yaw-roll coupling. This is when a rudder input will also roll the airplane and this is a behavior we want in a rudder-only plane.
Not enough dihedral and you will have a hard time keeping the plane from rolling over on itself and diving for the ground (instable) but the rudder will also be less effective in actually turning the aircraft. Too much dihedral and your wing isn't generating lift as effectively and it will also constantly be wobbling around in the roll axis like a pendulum. To my eye it looks like your wing needs a bit more angle to the wingtips, but I could be wrong. Try it out; it will be a great experiment/lesson no matter what the end result.
For a reference point, I just recently built and maidened this plane. This little guy's wingtips are angled at 30° from horizontal and it flies beautifully as a 3-channel plane. Just enough roll coupling for solid turns and enough stability I can let go of the sticks and it'll just do lazy circles until I tell it to stop.

 

[luvmy40]

Something to remember, dihedral gives the plane roll stability but more importantly, it allows something known as yaw-roll coupling. This is when a rudder input will also roll the airplane and this is a behavior we want in a rudder-only plane.
Not enough dihedral and you will have a hard time keeping the plane from rolling over on itself and diving for the ground (instable) but the rudder will also be less effective in actually turning the aircraft. Too much dihedral and your wing isn't generating lift as effectively and it will also constantly be wobbling around in the roll axis like a pendulum. To my eye it looks like your wing needs a bit more angle to the wingtips, but I could be wrong. Try it out; it will be a great experiment/lesson no matter what the end result.
For a reference point, I just recently built and maidened this plane. This little guy's wingtips are angled at 30° from horizontal and it flies beautifully as a 3-channel plane. Just enough roll coupling for solid turns and enough stability I can let go of the sticks and it'll just do lazy circles until I tell it to stop.
View attachment 236312

I love this little guy! Would you be willing to share the plans?

 

[Piotrsko]

Put upward pointing tip plates on the wing if you need to, but a sucessful glide says it ought to fly somewhere you can tolerate the slow turn rate an a dead calm day. You can also sometimes increase the turn by adding up elevator momentary

 

[Inq]

Outstanding!
Considering what I've seen on the forum of the oddities that can fly fine... Monty Python Castle, the little Cartoon planes... I think his has an excellent chance of flying. I'm thinking the week link will be the skinny fuselage will get bent and end the day. Take some popsicle sticks and duct tape and weights for C/G fixing and you'll be the Super Dad.

As its fun and gratifying when they create their own (without Dad helping) here is a link that might give him simple guidelines. The stuff at the top might discourage him, but the two plane drawings and design form about half way down might be something that guides him.

https://rcplanes.online/design.htm

 

[Tench745]

I love this little guy! Would you be willing to share the plans?

This is a down-scaled version of Hilmar Lange's Phat Phil (Original balsa plans available here https://www.flugmodell-magazin.de/downloads/handliches-balsa-modell-im-vintage-look/) I have emailed the original designer, and if he agrees I will be drawing up a set of plans for my smaller foam version to share with everybody here.

 

[Foamforce]

We maidened it today. It flew better than expected! I initially flew it but then my son took over in the buddy box. On the next flight he took off and landed it. He was excited.

Rudder authority was adequate but not acrobatic. Elevator authority was good. 2s was inadequate but a 3s 550 flew pretty nicely. I’m going to try some 3s 650s that I have next time. It’s a slow flying plane. I think there’s a lot of drag. We’ll also mess around with the CG. We got fairly lucky and it flew pretty well with the CG as is, but we’re going try it both ways and see how it goes.

Anyways, it went pretty well! Our next step is tuning and deciding what changes we need to make. Thanks all!

 

[hankflies03]

nice! great success! and as the entire forum says when we see a new plane...

 

[MrClean]

Cg forward a bit, weight up a bit, that's a lot of wing. Maybe some wingtip plates angled up a bit? Good first effort. I've had things that didn't have much authority or penetration that turned out to be just a CG too far back. Had one that I screwed up perfectly, a Delta with Elevon control. CG was so far back only the running engine was keeping it straight. More fuel I used the more trouble I was in. Got it close but over the tall grass and cut the engine. It floated down level. No airspeed I didn't have any control. Landed flat on that tall grass landed like a leaf was sitting there a foot over the ground on bent over pasture grass.
Check where the cg is and move it a couple percent forward. Give it some more power and maybe, just a little more weight. But, a more forward CG might solve everything.
good job.

 

[Piotrsko]

Howsabout scabbing on a bit more rudder? Otherwise, since it flew reasonably, I would mostly leave it alone until it breaks then start messing with cg and other things.

 

[Tench745]

We maidened it today. It flew better than expected! I initially flew it but then my son took over in the buddy box. On the next flight he took off and landed it. He was excited.

Rudder authority was adequate but not acrobatic. Elevator authority was good. 2s was inadequate but a 3s 550 flew pretty nicely. I’m going to try some 3s 650s that I have next time. It’s a slow flying plane. I think there’s a lot of drag. We’ll also mess around with the CG. We got fairly lucky and it flew pretty well with the CG as is, but we’re going try it both ways and see how it goes.

Anyways, it went pretty well! Our next step is tuning and deciding what changes we need to make. Thanks all!

Awesome! So glad to hear it has been a positive experience for you. Keep it up, and keep having fun!