One Sheet No-Waste Twin Tail Boom Series.

Hello again out there....

This article is about a series of planes I have designed around a single concept.  The concept is using a single 3/16 dowel cut in half to make twin tail booms in a  One-Sheet No-Waste design. My goal was to make a small, light, slow flying plane that could be flown in the local high school gym.  I am not sure that I was successful in reaching that goal because the resulting airplanes though small and light are not very slow. They are pretty fast and nimble instead. 

UPDATE 1-13-15: I was contacted by Hillbilly30 who has built  #2 from the second plan below.  He has included a description with photos and a video in an FT Forum posting.  He has more flight time with his build than I do with the entire series.  He made a couple of changes.  He used carbon fiber instead of wooden dowels.  He moved the battery to the top of the wing.  He added 4 1/2 degrees of down thrust to fix balloning at full thrust.

Hilbilly30's flight video:    

Note: this is best viewed at full screen.

Thanks Tad

End of update.

The planes were developed in the order they are numbered.  I am presenting them out of order in this article because #3 ended up being the best overall performer and is the one I will most likely feature in the build article.

This is #3 of the 4 designs I have developed so far:

Top View:

And bottom:

#3 Has a 31" wing span with a straight leading edge and tapered trailing edges.   It uses Wing "A" shown on the plans below.  

The plans are a simple pencil sketch with dimensions drawn at 1" = 20" on an 8 1/2 X 11 sheet:

The major dimensions can just be transferred to a 20" X 30" sheet of dollar tree foam board.  Rather than put all of the details on the full sheet I started by dividing the sheet into the larger rectangles then doing the smaller layout on each piece.  I think it is easier that way since you are always measuring from a corner or edge.Like this:

(This set is the rough cuts from the drawing below for Plane #5 added as an update at the end of the article) 

For plane #4 in the series (below) I decided to make a two channel trainer.  It is made from the same plans as #3 above but uses wing "B".  I  reversed the wing so that the leading edge is tapered and the trailing edge is straight (This could be done as a 4 channel with less dihedral as well.).  It looks like this:

Top: 

And bottom:

For this two channel version I increased the dihedral to 6 degrees (1 1/2" block under each wing tip).  It does not have ailerons but banks very nicely in a rudder-only turn and returns to level flight quickly when the controls are returned to neutral.  It can fly either fast or slow and so I think it will be a good first trainer.  It is probably a little quicker at full throttle than most of the store bought "Trainers" out there but at half throttle I think it would compare favorably to most.

Now, backing up a step...

There were two eearlier versions before #3 and #4.

Here are versions #1 (left)  and #2 (right):

These both have 40" wing spans.  

Plane #1 (left)  was my my first  disign in this series, the concept plane.  I started out thinking that the wing would be strong enough if I just scored and bent it similar to whart was done on "Olde Speedster".  The wingwas cut out and the bend lines were scored strongly on the bottom side.  The  camber was made by placing two scraps of foam under the center at the wing root and only one under the tip.  This did not produce as much camber as the Olde Speedster and the wing is longer.  It was evident after assembly that the wing was too flexable and would fold in flight so I added a single layered "spar panel" to the bottom of the wingspanning the two fold lines and glued to the .  That stiffened it considerably but I still got some stress wrinkles on the top of the wing in the first flight.  I added 6 skewers to the bottom to reinforce it.  I have not flown it since the reinforcement but it is considerably less flexable in static testing.  I think it will hold up. If I re-build this one I will use the FT method and fold the leading edge with a spar similar to #2, #3 & #4 but thinner.  That will do away with the need for reinforcing.

Bottom view #1(after reinforcing):

I added two skewers through the pod, one in front and one in back of the bottom "spar panels.  I then added two at the back edges of the spar panels centered on each boom dowel.  Those also pierce the pod for additional stability.  One was also added to each of the leading edges (also piercing the pod).  

The good news is that it is very fast and the ailerons are very responsive.  It will roll sharply almost at the top of a vertical stall.  This is the best high speed performer of the group.  Stall speed and landing speed are higher due to the thinner wing however.  

I still have to add the hatch cover to this one.

Plane #2 bottom:

Planes #1 and #2 were built from another plan:

Plane #2 was built with a thicker wing section.  It uses the FT wing assembly method of attaching the bottom panel to the leading edge of the top panel, cutting the 45 degree back-cuts and folding.  It has two spars on each wing creating a boxed spar.  This is very much stiffer than #1 was and did not need any reinforcement. 

The tails on my prototype #1 and #2  were made from separate pieces instead of one piece folded.  This allowed the vertical stabilizers to step back and the rudders are behind the trailing edge of the elevator.  I think I like that appearance better but the one-piece version is stronger.  The tail surfaces are also larger on these two.  I plan to make another #1 with the FT folded wing and the one piece tail to see how that works out.  I think both changes will be fine. I am showing the one piece folded design in the plan above and will probably us it on all future versions..

Both #1 and #2 have straight leading edges and tapered trailing edges (WIng"A")  but either could be built just as well with tapered leading edges and straight trailing edges (WIng "B") for a differednt look.  

Miscellaneous notes:

The ailerons are larger on #1 than on #2 and it is also more responsive.  The plan shows the larger ailerons. Less experienced pilots may need smaller throws or higher exponential for less touchy performance.

The landing skids on all four versions are similar.  They are for landing only and prevent ground scuffing.  Plane #2 was the first I did the skids on and you will notice that the main gear attachment is well back on the wing.  When I did #3 and #4 I moved it forward.  On maiden flights #2 was the only one that nosed over on landing so I am going to use the more forward position for all 4 in the future.

You will notice a short piece of dowel and plastic reinforcements on the left hand wing tip of each version.  These are for hand launching.  You just grip the wing tip loosely between your index and ring fingers and let it hang at your side (pivoting back).  Give it about 2/3 throttle and swing discus style straight ahead (not up as you might expect) and you are flying.  You do not need to throw hard.  The motor will do the work. 

For all four versions I used additional scraps to make some items such as the nose and hatch covers, spars and the motor mounts. 

The longish noses are needed for balance. The batteries are either 1000 or 1250 and are positioned right up at the nose.  Plane #1 actually has a 1250 and still needs $1.50 in quarters at the nose to balance.  I will try a 1500 instead for the next flight.

One added value feature:

These things stack for easy transport...

NOTE:  Look for the construction article within a week or so.  

UPDATE (11-04-14):

I have made version #5.  It is similar to #1 but has the stronger FT style folded wing and tapered leading edges. It also uses the folded one piece tail.  It looks like this:  

This picture shows the landing skids on the ground as they would be after landing.  

Equipment:

Servos: (2) or (4) 9gram

ESC: 20A - 30A

Motor: Hobby King Donkey ST2204 1550 kv; Turnigy 2822/14 1450 kv

Motor Lead Extensions: Make (3) to fit 3" to 4"

Supplies:

Dollar Tree Foam Board: (1) sheet plus a few scraps

3/16 Dowel: (1) pc 36" plus (1) pc 1 1/4"

Flag Wire: (4-5) pc 21"

Hot Glue & Gun

Bamboo Skewers: (2) pc 3"

Packing Tape

Velcro

Used gift cards or flexible cutting board.