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Nameless V-tail -> 1 Sheet, V-tail 'stick' build as light as possible (Build Log)

JasonK

Well-known member
#1
One thing that is mostly missing from the FT plan line ups is a V-tail (the sparrow is the only V tail that I found). So I am going to scratch build one up and document it here.

General plans include removing all paper surfaces possible (IE everything internal on the wing), using Whte Gorilla Glue instead of hot glue everywhere possible, etc. Going to see how light I can get the air frame. Targeting an A-Pack motor/electronics, as that is what I have available.
 

JasonK

Well-known member
#2
The Wing. 30" wide (full width of the foam-board). I used the Tiny Trainer plans to determine the score cut lines and the wing tip shapes. This was cut as a single piece instead of two parts that are connected. The wing will be straight. I had to make a few positional adjustments based on the TT's wing to reduce the total size and remove the diheadral.

VTailWingInside.png
 
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JasonK

Well-known member
#3
Final Wing -> had an issue with how I weighted everything down while the glue set and the airfoil shape ended up off slight. The glue is strong enough that I would have to remake the wing to redo this (no clean way of taking it back apart).

VTailWingProfile.jpg
 

JasonK

Well-known member
#4
I tested the Triangle shape that I would get with a 110deg tail fin layout and it seemed that it would be strong enough to be a full tail boom. Almost glued my fingers together (the 'use glues' warning on the glue is very relevant for this glue), thankfully some flour seems to have dried it out enough that I can touch things without them sticking.

Currently I have the tail in a jig holding it in shape while the glue dries (one of the downsides of this glue).

VTailCutout.jpg VTailHoldingJig.jpg
 

JasonK

Well-known member
#5
I got the tail glued to the wing (and pulled the flaperon servo wires through as they would be a pain to do after it was glued on). The tail control surfaces have been cut out. I did find getting the tail square to the wing to be a challenge and suspect I got it slightly off, hopefully it will only take a touch of trim (at most) to deal with any issues here. If I plan on rebuilding this, creating some jigs are something I would definitely consider doing to assist with various assembly steps.

I have started working on the Electronics/motor pod. I have it designed to be able to use the same power pod from the Mini-Series planes for the time being.

VtailWingAndTailtop.jpg VtailWingAndTailBottom.jpg VtailElectronicsPod.jpg
 

JasonK

Well-known member
#6
  • Glued in the Wing Servos (and tested)
  • Glued in the Tail Servos (and removed and need to replace, apparently the white gorilla glue will expand through the seams in the servo or I got 2 bad servos out of the box)
  • Cut the pushrods for the tail
  • 3D modeled/printed/installed push-rod guides.
  • Glued the electronics pod on
  • Did a few test throws with some clay for CG testing/throwing
VtailAirframeTop.jpg VtailAirframeBottom.jpg GluedUpServos.jpg
 

JasonK

Well-known member
#7
I got the servos, pushrods, and control horns install, did a quick balance check and the battery can go much farther back then I expected. Just need to work out a closure/access panel for the bottom of the plane and get it out for a maiden flight.

Currently 163g without a battery.
30" wing span.
 

Attachments

quorneng

Well-known member
#8
Your V tail is likely to be a bit short of effective fin area.
If the battery can go back you might consider shortening the nose as well. Remember all side area ahead of the CofG has to be compensated by equal area behind which means there is less 'left over' for lateral stability.
Low lateral stability can make a plane very uncomfortable in a turn with a tendency to go into a spiral dive all by itself. It will recover easily enough unless of course the ground gets in the way first. ;)

This works very well.
Picture5.JPG
The V tail is connected with a single servo as elevators only. It is flown "bank and yank".
 

JasonK

Well-known member
#9
Unless it is just some camera tricks making your v-tail look really small, my V-Tail is huge compared to the one in that picture, the fact that I took a picture straight down top/bottom might be creating some visual context oddities. the fins are at 110deg from each other. there is just under 4" vertical to the fins from the boom, my tiny Trainer has just over 4" of vertical from the fuselage.

side area ahead of the CofG has to be compensated by equal area behind
haven't seen this in any of the design suggestion stuff and will take this in consideration for future builds and if any changes need to be made. but I am sure it isn't a pure cross sectional area = cross sectional area, it is probably a balance thing (cross section * distance from CG).

If the battery can go back you might consider shortening the nose as well.
Yup, I have thought about this already, still want to verify how it files. I could also flatten the fuselage, there is about 2x the vertical space compared to my absolute need. I definitely figured this might go through more then one rendition until I am completely happy with it.
 
#11
i also did that in my university life and this give me so much memories. now it's time to refresh my memory and try again to create a new one. thank you
 

JasonK

Well-known member
#13
And a flight of the plane (not the maiden, didn't have someone to video tap that, but it flew the same the first time). Only issue is that it pitches up under power so I need to do one of the following: down angle on thrust, throttle -> down elevator mix, or figure out how to change the motor mount to be more in line with the vertical CG.

Other then the pitch up under power, it flew wonderfully. (I mostly flew as a bank/yank, didn't try much rudder, but I might need to tune down the rudder as rudder + aileron can turn inside of a few wing widths - and end up a bit nose down).

 

JasonK

Well-known member
#15
zero throttle - I get a _great_ glide... you can see it at the end of the video were I had to 'go around' again so I could actually land at my feet. Do you still think that might be an angle/GC/Trim thing? the Airfoil is a fairly standard FT airfoil (based on the Tiny Trainer's, and it is connected flat bottom to the flat top of the fuselage).
 

Sero

Well-known member
#16
zero throttle - I get a _great_ glide... you can see it at the end of the video were I had to 'go around' again so I could actually land at my feet. Do you still think that might be an angle/GC/Trim thing? the Airfoil is a fairly standard FT airfoil (based on the Tiny Trainer's, and it is connected flat bottom to the flat top of the fuselage).
Could be. Try it to find out.
Move the battery/CG back a bit and you should need some down trim to compensate, the down trim will keep the nose down with speed.

The flat bottom FT airfoil has up incidence, which creates more lift with speed. Shim the bottom back of the wing about 1 millimetre (Popsicle stick) where it meets the fuselage.

All easy adjustments to try. Just do a little at a time so there are no surprises.
 

JasonK

Well-known member
#17
The flat bottom FT airfoil has up incidence, which creates more lift with speed. Shim the bottom back of the wing about 1 millimetre (Popsicle stick) where it meets the fuselage.
Can't do this.. it is glued together with stuff that is way stronger then the foam (White Gorilla glue).

I believe it is throttle related more the speed, as even at low speed when I give it throttle it noses up and when I cut, the pitch up stops before it slows down (basically instantly).
 

Sero

Well-known member
#18
Can't do this.. it is glued together with stuff that is way stronger then the foam (White Gorilla glue).

I believe it is throttle related more the speed, as even at low speed when I give it throttle it noses up and when I cut, the pitch up stops before it slows down (basically instantly).
Yes sorry I hadn't noted that your wing was glued. I can't seem to hear the throttle of the plane in the video so it's hard to judge when your pitching up from that or stick input.

It still can pitch up from the reasons I mentioned as the prop wash will create more lift as it goes over the wing and make the tail more effective. I'm not saying that it is because of those, but in my experience, I have seen that.
 

JasonK

Well-known member
#19
yup, thanks... it is rather quiet.. you can hear it on a low fast flyby, but when up in the sky, I don't hear anything on the field either. throttle related pitch up was mostly being countered by me by hand, that video wasn't really to reflect the up-pitch issue. I actually showed someone else on the field by 'hands off'ing and it did a nice loop.
 

Sero

Well-known member
#20
yup, thanks... it is rather quiet.. you can hear it on a low fast flyby, but when up in the sky, I don't hear anything on the field either. throttle related pitch up was mostly being countered by me by hand, that video wasn't really to reflect the up-pitch issue. I actually showed someone else on the field by 'hands off'ing and it did a nice loop.
If it's that strong it could be a combination of things too, but thrust angle would be on the top of my list.
Half the fun figuring things out. Best of luck!