Official Freewing 90mm F-4 Phantom II Thread

[Alpha]

Sure, I have a few I could share. The F-4 went through the usual rounds of development, with a couple of fun challenges to overcome along the way. From my experience with previous F-4s in foam and composite of various sizes, we knew that takeoffs tended to "leap" if the undercarriage were placed in the scale position. There's also the matter of the scale main's angle, which is not 90 degrees to the fuse and is instead at an angle we can't replicate without significant additional cost and complexity and reduced strength along the mechanism.

Here's a picture of the departure angle on one of the CNC prototypes, which was too sudden and too steep:




After several adjustments in various places, here can be seen a much more predictable takeoff rotation at a much flatter angle with less elevator input. Much better.





As owners of our F-4s have figured out by now, we also did some special tweaking of the exhaust nozzles to get the thrust line we wanted:




Landing behavior is also important on all the models we develop, so this stage is flown and reflown until it's in the intended sweet spot between flaps, elevator authority, AoA and descent speed, etc.



Sizing control surfaces is also evaluated for positive authority at a range of speeds. Too small, too mushy, too large, too wild. As with landing gear, we take liberties where necessary on control surface outline in order to achieve the primary goal of predictable control.



Almost all the CNCs I work with end up covered in engineering notes written directly on the prototype. Little by little, design notes accrue. Prototypes are worked and reworked until they're Right. This is where most prototypes die.

[Alpha]

The CNC phase is where many changes can potentially occur. The number and degree varies per model, per manufacturer. It's always different, which keeps things interesting.



While CNC prototypes are initially cut using basic profiles, it's common practice among all the factories we've worked with including Freewing to wait until after major flight testing before the scale bits are finalized. In the case of the F-4 I had the benefit of General Stalder's input on the model/s exterior at different stages while it was being drafted. It's not about being strictly scale per se, it's more about "feeling right". He'd know better than I ever could. Based on his input and other resources and references, over time the F-4's exterior shape was finalized, striking a balance between scale fidelity and RC-sized flyability. There are always trade-offs, and we do our best to make the right call on each of the hundreds of decisions along the way. I imagine that in all of our careers, we could talk for hours about the intricacies, complexities, and nuances that differentiate doing our job well and doing our job poorly. It's the same thing over here. There's month's worth of details to talk about. Suffice to say we're grateful for the trust our customers put in us, and we're confident in the record we've established for continuing improvement and advancing innovation all the while at a reasonable cost.



Eventually after multiple prototypes are sacrificed, the molds are made, which is a mind bogglingly huge figure. By this time we better have gotten it Right or else we're Toast.




Then we put everything in a bag, shake it up for 7.9 hours while suspended upside down at a 97 degree angle at 15.05 degrees Celsius with James Taylor playing in the background at 22 decibels, then out comes the final product ready to ship across the world.

[rifleman_btx]

Nice!!!!!!

[T-CAT]

The CNC phase is where many changes can potentially occur. The number and degree varies per model, per manufacturer. It's always different, which keeps things interesting.



While CNC prototypes are initially cut using basic profiles, it's common practice among all the factories we've worked with including Freewing to wait until after major flight testing before the scale bits are finalized. In the case of the F-4 I had the benefit of General Stalder's input on the model/s exterior at different stages while it was being drafted. It's not about being strictly scale per se, it's more about "feeling right". He'd know better than I ever could. Based on his input and other resources and references, over time the F-4's exterior shape was finalized, striking a balance between scale fidelity and RC-sized flyability. There are always trade-offs, and we do our best to make the right call on each of the hundreds of decisions along the way. I imagine that in all of our careers, we could talk for hours about the intricacies, complexities, and nuances that differentiate doing our job well and doing our job poorly. It's the same thing over here. There's month's worth of details to talk about. Suffice to say we're grateful for the trust our customers put in us, and we're confident in the record we've established for continuing improvement and advancing innovation all the while at a reasonable cost.



Eventually after multiple prototypes are sacrificed, the molds are made, which is a mind bogglingly huge figure. By this time we better have gotten it Right or else we're Toast.




Then we put everything in a bag, shake it up for 7.9 hours while suspended upside down at a 97 degree angle at 15.05 degrees Celsius with James Taylor playing in the background at 22 decibels, then out comes the final product ready to ship across the world.

I really enjoy reading about the process and details like this. Thanks a ton for taking the time for writing and I’m sure many other enjoy reading about it too.

[vduniec]

I must get one and do the Coral Sea scheme.

Callie already has it in stock!

[EA-6B Geek]

Thanks for the great answer Alpha! Certainly more insight than I could have ever expected. Truly enjoyed reading that, and those prototype photos are fantastic.

[andrew_flyguy]

The CNC phase is where many changes can potentially occur. The number and degree varies per model, per manufacturer. It's always different, which keeps things interesting.



While CNC prototypes are initially cut using basic profiles, it's common practice among all the factories we've worked with including Freewing to wait until after major flight testing before the scale bits are finalized. In the case of the F-4 I had the benefit of General Stalder's input on the model/s exterior at different stages while it was being drafted. It's not about being strictly scale per se, it's more about "feeling right". He'd know better than I ever could. Based on his input and other resources and references, over time the F-4's exterior shape was finalized, striking a balance between scale fidelity and RC-sized flyability. There are always trade-offs, and we do our best to make the right call on each of the hundreds of decisions along the way. I imagine that in all of our careers, we could talk for hours about the intricacies, complexities, and nuances that differentiate doing our job well and doing our job poorly. It's the same thing over here. There's month's worth of details to talk about. Suffice to say we're grateful for the trust our customers put in us, and we're confident in the record we've established for continuing improvement and advancing innovation all the while at a reasonable cost.



Eventually after multiple prototypes are sacrificed, the molds are made, which is a mind bogglingly huge figure. By this time we better have gotten it Right or else we're Toast.




Then we put everything in a bag, shake it up for 7.9 hours while suspended upside down at a 97 degree angle at 15.05 degrees Celsius with James Taylor playing in the background at 22 decibels, then out comes the final product ready to ship across the world.

I seriously enjoyed reading every bit of that - anytime you want to post more stuff like this, please do! :)

[rifleman_btx]

"Eventually after multiple prototypes are sacrificed, the molds are made, which is a mind bogglingly huge figure. By this time we better have gotten it Right or else we're Toast."
Exactly why I say keep the models affordable, or they will never make a profit. As in all aspects, power needed and just airframe cost.

[dahawk]

This is awesome. Great to learn how the sausage is made! A great process. Amazing the value we get with all the engineering hours and production costs involved not to mention free shipping.

Thanks Alpha !

Hawk

[Alpha]

Happy to share a small peek, guys. I hope if anything it enhances our appreciation for the models in our garages (or kitchen tables?). For competitive reasons I can't go too deep in detail, but what I'm sharing has been meted out over the years so it's already public knowledge.

Dahawk, speaking of hours and costs, as a quick example our 90mm F-4 comprises approximately 650 parts and subassemblies in more than 10 different materials from over 20 suppliers and took over a year to develop with a multi-national team, yours truly included. Manhours are measured in the thousands. None of that includes the actual mold costs, material costs, production costs, labor costs, shipping costs to warehouses and shipping to the customer, spare parts inventories and warranty costs. I recall similarly in the past Tom has mentioned the deep effort behind what we do, not to boast or lament, but purely to underscore our assertion that we're undeniably in this business to serve our customer family with leading products.

Of course many businesses these days especially in hobby markets are in similar situations and also leverage all their passion to grow the hobby. So give a pat on the back to your friendly guy at the LHS, too. Best of all, share the hobby with a friend or two or ten!

[PhantomNut]

Is the Navy gray version that is coming all gray on top including the vertical stab? Also, are the nose and canopy frame going to be painted gray as well? I'm hoping it will just be all gray and white.

[rifleman_btx]

Doubt it from the factory pics.

[themudduck]

Why wouldn't the entire top of the fuselage be gray? It would be easier/faster/less expensive to paint it all one color.

(with the exception of the tail cone - and I mean, the anti-skid parts could be stickers...)

[Rhitchy]

bonjour les amies pour ce belle avion freewing f4 d quel est le poid maximun il peut transporter?

pour une motorisation en 6s 12 pales et esc 155 gekko

[Grady.c]

bonjour les amies pour ce belle avion freewing f4 d quel est le poid maximun il peut emporte?

pour une motorisation en 6s 12 pales et esc 155 gekko

Here I translated it:
hello friends for this beautiful aircraft freewing f4 what is the maximum weight it can carry? for a motorization in 6s 12 blades and esc 155 gekko

[themudduck]

Well, there is probably some misunderstanding in the translation. I mean, what I am thinking is that when Rhitchy said he's looking for "the maximum weight" he probably means "the largest most powerful EDF system" -- and my feeling is that instead of looking for "what is the largest most powerful EDF you can put in the Phantom" a much better question would be, "what is the system that provides the most power for the least weight". In other words, look for the most efficient system, not the heaviest.

Trying to figure out the heaviest largest possible EDF is a losing game - general speaking this means more current draw, which means a larger heavier battery is needed, which results in less flight time and a heavier airframe which takes away the advantage of greater thrust. A never-ending spiral in the wrong direction.

Looking for the maximum power output with a lighter system is usually the best way to go.

.

Eh bien, il y a probablement un malentendu dans la traduction. Je veux dire, ce que je pense, c'est que quand Rhitchy a dit qu'il cherchait «le poids maximum», il voulait probablement dire «le plus grand système EDF le plus puissant». vous pouvez mettre dans le fantôme "une meilleure question serait," quel est le système qui fournit le plus de puissance pour le moindre poids ". En d'autres termes, recherchez le système le plus efficace, pas le plus lourd.

Essayer de trouver le plus gros EDF le plus lourd possible est un jeu perdant - en général, cela signifie un tirage plus important, ce qui signifie qu’une batterie plus lourde est nécessaire, ce qui réduit le temps de vol et la cellule plus lourde. Une spirale sans fin dans la mauvaise direction.

Rechercher la puissance maximale avec un système plus léger est généralement la meilleure solution.

[Rhitchy]

hello I put my question in more clear my current engine is 1680 kv freewing engine a 155A controller 12 blades the current weight is 4831 grams this plane did not yet take off


what is the weight of your f4 with engine in 6s ?


what is the maximum weight of this airplane ?

[themudduck]

I used Google to translate and I have no idea if that French translation will make any sense at all. Maybe I don't make any sense at all. What do you guys think?

I have a friend in my club who sees the solution for every plane: a larger motor. He put a 70mm fan into the little 64mm Panther, with a larger 4S battery. Guess what? It made an even LARGER hole in the ground!!
He has a 25-size balsa Piper Cub, he put a 60-size Thunder-Tiger motor in it and it flies at about 125 mile per hour. And the wings ripped clear off in level flight! So he rebuilt it and put a 90 in it.... with aluminum struts "so the wing won't break like it did last time".

[themudduck]

hello I put my question in more clear my current engine is 1680 kv freewing engine a 155A controller 12 blades the current weight is 4831 grams this plane did not yet take off


what is the weight of your f4 with engine in 6s ?


what is the maximum weight of this airplane ?

Hello Rhitchy,

According to MRC, the 6S model (9blade fan, 130amp) should weigh about 3600gm including the battery. The 8S model (12blade fan, 150amp ESC) weighs about 4000gm.

I don't know what the maximum weight will be, but its a good idea to try to have the minimum weight possible. If your plane is not taking off then my guess is that 4831gm is too much!

Bonjour Rhitchy,

Selon MRC, le modèle 6S (ventilateur à 9 lames, 130 ampères) devrait peser environ 3600g, batterie comprise. Le modèle 8S (ventilateur 12 lames, ESC 150 ampères) pèse environ 4000 g.

Je ne sais pas quel sera le poids maximum, mais c'est une bonne idée d'essayer d'avoir le poids minimum possible. Si votre avion ne décolle pas, je pense que 4831g est trop!

[Rhitchy]

Well, there is probably some misunderstanding in the translation. I mean, what I am thinking is that when Rhitchy said he's looking for "the maximum weight" he probably means "the largest most powerful EDF system" -- and my feeling is that instead of looking for "what is the largest most powerful EDF you can put in the Phantom" a much better question would be, "what is the system that provides the most power for the least weight". In other words, look for the most efficient system, not the heaviest.

Trying to figure out the heaviest largest possible EDF is a losing game - general speaking this means more current draw, which means a larger heavier battery is needed, which results in less flight time and a heavier airframe which takes away the advantage of greater thrust. A never-ending spiral in the wrong direction.

Looking for the maximum power output with a lighter system is usually the best way to go.

.

Eh bien, il y a probablement un malentendu dans la traduction. Je veux dire, ce que je pense, c'est que quand Rhitchy a dit qu'il cherchait «le poids maximum», il voulait probablement dire «le plus grand système EDF le plus puissant». vous pouvez mettre dans le fantôme "une meilleure question serait," quel est le système qui fournit le plus de puissance pour le moindre poids ". En d'autres termes, recherchez le système le plus efficace, pas le plus lourd.

Essayer de trouver le plus gros EDF le plus lourd possible est un jeu perdant - en général, cela signifie un tirage plus important, ce qui signifie qu’une batterie plus lourde est nécessaire, ce qui réduit le temps de vol et la cellule plus lourde. Une spirale sans fin dans la mauvaise direction.

Rechercher la puissance maximale avec un système plus léger est généralement la meilleure solution.

No, I just want to know how much it can carry with my engine is a plane that I'm not yet flying

the maximum weight it can carry?