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ABC STEM Trifecta Group Build

BATTLEAXE

Well-known member
#1
Hello and welcome to a new group build thread. This thread will be based on but not limited to any variation of the STEM prop and slot jets in any variation and mods left to the imagination. The 3 planes designed by students in the STEM program, Alpha, Bravo, and Charlie are up for grabs. Take these planes as stock as they come or build them to the potential limits, no rules, no holds barred.

This is a completely open invitation and all ideas and suggestions are more then welcome. The idea is for us all to experience the hard work and visionary design that went into these airframes by dedicated and truly talented kids, plus these planes are fun to fly. This is also a way we can pay homage for our appreciation for flight and to encourage out of the box thinking in design, building, and finally the flight experience. Push your limits on this even if you haven't flown a prop and slot/elevon style airframe to breaking the glass wall of speed and maneuverability.

Have fun and let the games begin (y):cool:(y)
 

Vimana89

Well-known member
#6
I'm in! I've been waiting for a fresh group build right at my level of building and flying, and as soon as you tossed out this idea, I knew it needed to happen. I gave the mini Scout challenge/group build a try or two, good bird but finicky for my build skill at the time. I tossed around the idea of joining the triplane group build(still have the kit), but set that aside for now. This is the right one for me to jump into, and the right time. My work with my FTFC20 entries and Arrowhead are going fast and smooth, I can build and fly RET, AET, and now elevons, and my building is about the level these little prop slot jets are at. I can get me a speed build kit to save time possibly, maybe mod it or tweak it, load it out just the way I want.

Decisions though...the Alpha is just so classic looking and well-rounded, the Charlie is tempting because it's gentle and easy-going plus looks cool and unique, and the Bravo has so many thing going...for one, it's a delta, probably the lowest aspect delta FT has to offer. For two, the structure and air foil of the wing are something I can study to find better ways to build custom delta wings. For three, it is considered the most challenging to fly and fastest, but what I would really like to do is extend the flight envelope into slow and high alpha by giving it an overpowered prop, because of the high sweep delta wing and canards, it will have symmetrical air flow and good pitch control, which are necessary for high alpha aerobatics. I could potentially cobra that(y).

I'm going to see what others pick and why, and watch a few vids of each in flight, and then think of my build, loadout, and customization options. Then I'll make a choice.
 

BATTLEAXE

Well-known member
#7
I will be going for the Alpha at a 135% scale to fit the C pack and an 8" prop. I was looking at strictly Alpha and marry the wing to the fuse, change the airfoil to a KFm2 just like I did on the FT-22. But now I am thinking of the interchangeability of the wings and I might do the removable wing, one Alpha and one a derivative of the Bravo. Still KFm2 wings with integrated spars, given there will be more space in the fuse I think I might box and double the nose section for durability and lean the Vstabs out just like the 22. I have heard that the control surfaces could use some enlarging so that will be on the list as well.

I am pretty excited about this one considering the Sportster is almost done and I am looking at my sad little 22 and want to replace it. I like the interest so far (y):cool:(y)
 

The Hangar

Well-known member
#9
Nice, I'll be doing the Alpha with a 50mm EDF!! I'm going to change up the shape of the V stabs a little bit to look like an F-18, and probably a few other aesthetics here and there. To save weight I'm going to ditch the removable wing.
Edf - awesome! I’ll scrap the removable wing to save weight as well. Current setup I’m planning on is an f pack on 3s with a 6x4x3 prop! Should have some decent speed with this one!
 

BATTLEAXE

Well-known member
#10
Nice, I'll be doing the Alpha with a 50mm EDF!! I'm going to change up the shape of the V stabs a little bit to look like an F-18, and probably a few other aesthetics here and there. To save weight I'm going to ditch the removable wing.
I'm still on the fence with the removable wing as well. The top plate of the fuse could easily be integrated as part of the wing.

I like the EDF idea. No slot, run the thrust tube all the way back?

Should do 2 50mm EDF's
 

Vimana89

Well-known member
#13
Nice, I'll be doing the Alpha with a 50mm EDF!! I'm going to change up the shape of the V stabs a little bit to look like an F-18, and probably a few other aesthetics here and there. To save weight I'm going to ditch the removable wing.
Sounds awesome, that will be cool to see👍. I'll be doing my build for this as a prop in slot but I really want to make an EDF jet soon. I'm actually thinking the Arrowhead down the road, give it a slick and pointy nose and EDF, although I really like it in its basic form too. I'd like to make some semi-scale EDF jets soon too, an F-94, F-106 Delta Dart, and lots more. Your Alpha build will be quite unique!
 

Vimana89

Well-known member
#14
Alright. This is what I'm thinking for my entry. Option one: Stock Bravo speed build kit, ditch the removable wing if it's possible with the kit. I probably don't want to toy with the aerodynamics like add any winglets. Option two: Since I want super high alpha, go completely scratch/custom, down size the plane a tiny bit, and nix the complex air foil for a one sheet wing. Proportions and layout would be the same, it would still be a Bravo in all other respects. Either way, I'll have an aggressive 3-4 blade prop, and I'll be keeping the canards on this one for pitch stability.
 

BATTLEAXE

Well-known member
#15
I just did some more detailed measuring, because I have to narrow the score cavities for the FB thickness in the folds I will be able to fit a 9" prop. Which is perfect for the 9x6 electric only prop I have to play with. Plus the center of the motor shaft sits below the wing so it creates just enough clearance. I am stoked!
 

BATTLEAXE

Well-known member
#16
After thanksgiving dinner tonight the tryptophan kicked in and knocked me out for a couple of hours, and I haven't been able to sleep since. So out to the bench I go while everyone is in bed. My original plan was to fit an 8" prop in this thing and after doin some rough math I figured going to 135% was gonna be the answer. Printed out the plans and started to put the tiles together and found that I could fit a 9" prop instead, bonus right?

Then I got to thinking about weight and size compared to the dimensions of the FT-22 which will fit a 9" prop at a 25" wingspan at considerably less FB then the Alpha at 135%. Plus I just purchased a couple of 8" props to fit my V2 of the 22 which would go to waste if I am using 9" props on this. So I went back to the calculator and figured out a new scale dimension to go with that will fit with a frogs hair of wiggle room for a 8" prop was 122%. With a 13% drop in size, plus doing a fixed and not interchangeable wing, I will be saving over 13% in weight, plus the weight saving in the wing design itself. The real bonus is that it brings the wingspan down to 29.25", which will fit the entire top fuse plate/wings on one sheet of FB.

Printed out the new plans and tiled them together and it all works out. It pays to check and double check in the prep stage to dial this stuff in. Now I am truly stoked!
 

Vimana89

Well-known member
#17
After thinking about it and conversing a bit with @CarolineTyler after seeing her do high alpha with the Bravo on Phoenix sim, It is apparent that a rudder is needed for crazy high alpha(That's how I've been able to do it so far on RET planes). I'm rethinking which jet I'll build, as the VS on the Bravo is designed poorly for the addition of a rudder, and because I have no experience yet in 4ch and was going to wait a bit on attempting one. I'm now leaning towards Charlie...don't get me wrong, the Alpha is probably a bit more fast and maneuverable, but there are practically NO GOOD VIDS I can find of people flying the Charlie! I've come across one decent maiden of the Charlie that was actually by @FoamyDM (good stuff!), but not seen a vid with longer flight time or really trying any aerobatics. I'm interested to see what this plane is all about :unsure:.
 
#18
Alright so I've started doing a bit of work, to get my some of my thoughts in order when I'm modding a plane, I like change as much as I can before I trace stuff on to foam so I make changes to the paper templates and write notes for myself for later on.
I'm going to be building the plane primarily around the top plate piece. Some of the changes I made were-
I cut off the "ears" that go around the servo and ditched the servo hole altogether.
There is one big tab that goes around all the cutouts that serves no purpose other than making the alignment for a few parts slightly easier, so I cut it off.
To save weight I'm making the elevons part of the top plate instead of gluing them on later, so I taped them down where they would sit if I glued them on.
P1280314.JPG
 
#19
After thinking about it and conversing a bit with @CarolineTyler after seeing her do high alpha with the Bravo on Phoenix sim, It is apparent that a rudder is needed for crazy high alpha(That's how I've been able to do it so far on RET planes). I'm rethinking which jet I'll build, as the VS on the Bravo is designed poorly for the addition of a rudder, and because I have no experience yet in 4ch and was going to wait a bit on attempting one. I'm now leaning towards Charlie...don't get me wrong, the Alpha is probably a bit more fast and maneuverable, but there are practically NO GOOD VIDS I can find of people flying the Charlie! I've come across one decent maiden of the Charlie that was actually by @FoamyDM (good stuff!), but not seen a vid with longer flight time or really trying any aerobatics. I'm interested to see what this plane is all about :unsure:.
Nice!!
 

BATTLEAXE

Well-known member
#20
Got pretty much the same done, just a different direction,
20191014_190427.jpg

This here is the shape of the main top plate, It will be cut from 2 different sheets of FB and joined at this forward line, with a skewer spar sandwiched between the 2 halves. The elevons will also be attached to this layer, not separate pieces...
20191014_190501.jpg

Fold the 2 insets forward and this will be the top layer of the KFm2 wing back to the rear line shown here. The top and bottom layers will be glued together with spray adhesive just like I did on the 22.