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Twin Boom Tiny Trainer (single pusher prop)

duckduckgoose

Well-known member
#1
So I've recently built a twin boom replacement tail for my Ft explorer (yet to maiden) and really like the look of twin boom tail designs. I have a very much loved tiny trainer which has done pretty well, I even had fpv set up and got pretty high up. It has had its tail broken off and re glued twice and I decided it's time had come for some radical experimentation. THE TINY TWIN BOOMER. I have no idea where this will go, but its worth a shot. I'm a strong believer in the TLAR (that looks about right) method. So I'm sure I'll learn heaps along the way. IMG_20190521_185032-01.jpeg IMG_20190522_131945-01.jpeg
 
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duckduckgoose

Well-known member
#3
Finally, a use for the glider nose. So as this was my first ft plane, I made every thing the plans said to even though I wasn't going to use the glider nose. This will now be the nose of the Tiny twin boomer ( TTB ). In order to make it fit the angle of the power nose (now facing backwards) I needed to cut the angled tabs on the side back.
IMG_20190615_201157-01.jpeg
 

duckduckgoose

Well-known member
#4
Here is the completed fuselage. I glued the inner section into the nose section. I love how battered and filthy the (used) power nose looks against the (unused) glider nose. This plane has seen things... IMG_20190615_201847-01.jpeg
 
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duckduckgoose

Well-known member
#5
HERE COMES THE BOOM(S)! So I'm just using what happened to be around me for the tail booms. Carbon rods would be preferable but I found some thin aluminium garden stakes that had a plastic coating on the outside. Once the plastic was off, I found it was light and still very rigid. And it also glued well to foam board. I cut the booms the same length of the fuselage (because TLAR). IMG_20190615_210012.jpg
IMG_20190615_205901.jpg
 

duckduckgoose

Well-known member
#6
A-TAIL OF TWO BOOMS...? I'm going with an inverted v-tail (or 'A' Tail) mostly because it looks cool, but also because I have a couple v-tail planes already so I am familiar with the programming. Also, it means I still only need two servos on the tail instead of a more complex twin rudder setup like the bronco. I used Triangle Calculator ( https://www.calculator.net/triangle-calculator.html ) to figure out how long the two surfaces need to be. I decided to put the two booms 38cm apart under the wing and the angle of the tail to be 120 degrees. Just plug in the measurements and angles you know, and it gives you the length of the two other sides of the "triangle". I made the tail 15cm deep (with 5cm folded over with a C fold for added strength) and 22cm long as it worked out. Then I marked the lines on 5he wing as square as possible and glued them straight on.
 

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whackflyer

Well-known member
#7
Yes! Someone else has the same idea as me! I’ve been wanting to build a twin boom TT for a long time, but it keeps getting pushed off my build list (cuz who doesn’t have a big long build list and keeps finding cool new projects to build)
I’ll be watching!
 

duckduckgoose

Well-known member
#8
Added the servos on the tail. There is plenty of room in the nose to balance the plane so I put the servos directly on the tail as far back as possible to add more tail weight

IMG_20190615_235456.jpg
 
#13
Just plug in the measurements and angles you know, and it gives you the length of the two other sides of the "triangle".
I looked into how to convert something to a v-tail a few weeks ago and was surprised to find out that's not really how the aerodynamics work out. I initially assumed like you that it just needs to match area as viewed from the original profile. http://www.charlesriverrc.org/articles/design/markdrela_vtailsizing.htm Summary: Your v-tail needs the same amount of area as your regular tail, and the angle is a little more complicated. It sort of makes sense in retrospect (you can't get the same control with less surface area), and the angle works out like equal power mixing of signals.

Also, I like the way my little inverted v-tail plane flies and looks. Good choice. :D
 

duckduckgoose

Well-known member
#14
I looked into how to convert something to a v-tail a few weeks ago and was surprised to find out that's not really how the aerodynamics work out. I initially assumed like you that it just needs to match area as viewed from the original profile. http://www.charlesriverrc.org/articles/design/markdrela_vtailsizing.htm Summary: Your v-tail needs the same amount of area as your regular tail, and the angle is a little more complicated. It sort of makes sense in retrospect (you can't get the same control with less surface area), and the angle works out like equal power mixing of signals.

Also, I like the way my little inverted v-tail plane flies and looks. Good choice. :D
I honestly didn't even think much about it but I'd say it has more area than the old tail so hopefully it should be fine, otherwise there always a razor blade to chop it down a bit haha
 

CapnBry

Well-known member
#16
Looks good, frankenstein all the tiny trainers I say! I also always appreciate when someone builds with materials they find at the hardware store instead of just jumping right to using a ton of carbon fiber tubes. The greatest part of FliteTest planes are going from I'd like to build an airplane today to flying without having to keep a stock of a buncha different shapes and sizes of exotic materials (materials that I can't go get right now).
 

duckduckgoose

Well-known member
#17
Looks good, frankenstein all the tiny trainers I say! I also always appreciate when someone builds with materials they find at the hardware store instead of just jumping right to using a ton of carbon fiber tubes. The greatest part of FliteTest planes are going from I'd like to build an airplane today to flying without having to keep a stock of a buncha different shapes and sizes of exotic materials (materials that I can't go get right now).
Funny thing is, I originally bought the garden stakes a year or so ago for a massive kite project I was working on. The kite never worked, but hopefully this does!
 
#18
I honestly didn't even think much about it but I'd say it has more area than the old tail so hopefully it should be fine, otherwise there always a razor blade to chop it down a bit haha
The other bit is that with a 120° angle it decreases the vertical stabilization quite a bit. 110° gives you a ~1:2 vertical to horizontal area ratio while 120° gives you 1:3 which is a much bigger difference than it seems like it should be. One thing I liked about making my v-tail is that it was really easy to iterate on the tail though. Adjust the numbers, and fold a single piece of foam. :D
 

duckduckgoose

Well-known member
#19
The other bit is that with a 120° angle it decreases the vertical stabilization quite a bit. 110° gives you a ~1:2 vertical to horizontal area ratio while 120° gives you 1:3 which is a much bigger difference than it seems like it should be. One thing I liked about making my v-tail is that it was really easy to iterate on the tail though. Adjust the numbers, and fold a single piece of foam. :D
Thanks for that, maybe if it needs more vertical stab I could put a single vertical fin up or down. Or just cut and glue like you said. Hopefully get a chance to maiden today or tomorrow
 
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