FTFC'25 WWII Saab J21 designed by FlyerInStyle and MiniacRC

[FlyerInStyle]

This is the design/build thread for the j21. I always wanted to design a Saab plane and seeing as I couldn't find a foamboard j21 plan I thought it would be the perfect candidate for the FTFC'25 WWII.

This plane will be th mighty mini size, with a wingspan of 30" and powered by an a or f pack, along with propbably a 3s 850, as balancing might be an issue. It will be just bank nad yank, and hopefully have folding wingtips instead of just removable ones, if needed, so that it can fit iin any car.
So far the design is undergoing minor revisions and overall is almost done.

here are some pics of what it looks like right now

Update:

Here is the build video:

And the long awaited maiden video:

Attached is the current set of plans, which is almost final just needs finishing touches that I feel I am overlooking (beta testing is needed)

I have posted a resource for this, basically everything that I have in this post, even a bit less, but if anyone wants to take a look, its here: https://forum.flitetest.com/index.php?resources/mighty-mini-j21.503/

 

[Jo's squadron]

cool, so you are gonna have some free plans?

 

[Michael9865]

Nice.

 

[FlyerInStyle]

cool, so you are gonna have some free plans?

of course!

 

[CrshNBrn]

I'm always so impressed by you folks that can design plans. I can follow a plan and and cut a ton of foam...but designing? Way beyond my skill level.

 

[FlyerInStyle]

I'm always so impressed by you folks that can design plans. I can follow a plan and and cut a ton of foam...but designing? Way beyond my skill level.

honestly I thiought the same thing, turns out with some basic CAD experience you can get it done, its jsut a lot of work, form there its just doing it better and making optimizations which I am very thankful for @MiniacRC helping me with.

 

[Mr Man]

I prefer 2d cad when designing foamboard airplanes.

 

[leaded50]

My J-21 build approx 800mm wingspan.

 

[Mr Man]

My J-21 build approx 800mm wingspan.
View attachment 246436

😳

 

[Mr Man]

My J-21 build approx 800mm wingspan.
View attachment 246436

Is that for the 2025 wwii design and build challenge?

 

[leaded50]

Is that for the 2025 wwii design and build challenge?

nope, its already built, and have not all things needed for the challenge to show. so Flyer in styles version would be the one to win in challenge?

 

[Mr Man]

nope, its already built, and have not all things needed for the challenge to show. so Flyer in styles version would be the one to win in challenge?

I thought it ended on March 31st

 

[FlyerInStyle]

I thought it ended on March 31st

No, its definitely going on, this is officially entered into it, I believe its march 31st 2025, the 25 signifies the year, so its not over yet.

 

[Jo's squadron]

of course!

cant wait!

 

[FlyerInStyle]

Sorry for the long delay, struggling finding time to do this, will start making plans sometime soon. (Will start with testing fuselage and go from there)

 

[Mr Man]

Sorry for the long delay, struggling finding time to do this, will start making plans sometime soon. (Will start with testing fuselage and go from there.

Cool!

 

[FlyerInStyle]

An update for anyone watching this, I have started unfolding the fuselage plans, this is what they will look like now just time to grind the repetitive work.

 

[L Edge]

This is the design/build thread for the j21. I always wanted to design a Saab plane and seeing as I couldn't find a foamboard j21 plan I thought it would be the perfect candidate for the FTFC'25 WWII.

This plane will be th mighty mini size, with a wingspan of 30" and powered by an a or f pack, along with propbably a 3s 850, as balancing might be an issue. It will be just bank nad yank, and hopefully have folding wingtips instead of just removable ones, if needed, so that it can fit iin any car.
So far the design is undergoing minor revisions and overall is almost done.

here are some pics of what it looks like right now
View attachment 246389 View attachment 246390

If you look at the upper picture, three things can happen. The 2 booms going back have a slot running the full length back.
I assume those booms act as a landing gear and support the tail.

What is going to happen, the slot weakens the booms and any side motion of the plane(tough landing) will bend/break the lower boom and probably cause damage/problems with the tail.

Secondly, I assume the flow from the exhaust(EDF or props) is going to interact with the tail and you lack strength with the booms, worst case is flutter can be caused and rip off the tail. (been there, done that)

If you do a tail strike on landing, ?????????How are you flaring?

I fly Bobcats where the elevator is out of the way of prop/EDF airflow. Still my booms bend. Had to run thin strips inside/outside of boom glued to stiffen the booms from moving side to side which helped calm elevator fluctuations.

 

[Mr Man]

If you look at the upper picture, three things can happen. The 2 booms going back have a slot running the full length back.
I assume those booms act as a landing gear and support the tail.

What is going to happen, the slot weakens the booms and any side motion of the plane(tough landing) will bend/break the lower boom and probably cause damage/problems with the tail.

Secondly, I assume the flow from the exhaust(EDF or props) is going to interact with the tail and you lack strength with the booms, worst case is flutter can be caused and rip off the tail. (been there, done that)

If you do a tail strike on landing, ?????????How are you flaring?

I fly Bobcats where the elevator is out of the way of prop/EDF airflow. Still my booms bend. Had to run thin strips inside/outside of boom glued to stiffen the booms from moving side to side which helped calm elevator fluctuations.

I think he’s gonna put skewers in there.

 

[FlyerInStyle]

If you look at the upper picture, three things can happen. The 2 booms going back have a slot running the full length back.
I assume those booms act as a landing gear and support the tail.

What is going to happen, the slot weakens the booms and any side motion of the plane(tough landing) will bend/break the lower boom and probably cause damage/problems with the tail.

Secondly, I assume the flow from the exhaust(EDF or props) is going to interact with the tail and you lack strength with the booms, worst case is flutter can be caused and rip off the tail. (been there, done that)

If you do a tail strike on landing, ?????????How are you flaring?

I fly Bobcats where the elevator is out of the way of prop/EDF airflow. Still my booms bend. Had to run thin strips inside/outside of boom glued to stiffen the booms from moving side to side which helped calm elevator fluctuations.

yeah there will be a skewer in the hole plus a doubled up tail boom, and I accounted for the fact that the tail will be weaker. Its made for a 5-6" prop, not sure if 6" will fit but it'll land like any other mini plane with a 2 bladed prop, not really worried about that