One Sheet No Waste - Simple Fold Delta

 Hello Everyone,

This article details the design and construction of another in my series of "One Sheet No Waste" designs. The premise for this design was to maximize the use of cut and fold, along the lines or origami.  This design I am calling "One Sheet No Waste - Simple Fold Delta".  For the purist it can be made with cuts, scores and folds only.  That approach leaves a square trailing edge so I have elected to cut the elevons free and reverse them for a more dynamic look.  Some sacrifices must be made in the interest of art.

Here is a picture of the prototype:

I tried one short flight inside the local highschool gym but found it was just too energetic for those confines. It was flying very well for about 5 seconds before losing an argument with the concrete bleachers.  I thought it wise to regroup and wait for siutable outdoor weather.  The good news is that it survived a pretty hard nose impact with very little damage.

There is one twist to the design, literally.  The raised fuselage section has a twist formed in the panels.  The front is folded a complete 180 degrees so that the inside faces are glued back to back, whereas the rear section at the motor mount forms a 90 degree angle.  This was accomplished by removing most of the paper on the inside of that section.  Here is a head-on picture showing the twisted panels: 

Here is a picture of the paper model with which I developed the design concept:

It still has the two small  triangles attached in the motor mount area. They were cut off and made tail skids in the prototype.

Here is the bottom of the prototype showing the tail skids, flag wire main landing skids as well as the running gear arrangement:

On the prototype the bottom panels did not quite come together as I envisioned.  This was an unintended result based on the geometry of the fuselage and wing folding.  I originally intended to correct it in subsequent builds but it actually worked out pretty well as a ventilation channel and the skewer tie in the back makes everything solid so I ended up not changing it.

Here is the prototype "bird" in landing position:

No belly scuffs on MY belly landings!

Despite my continuing "No Waste" theme, I believe this is the first design where every square inch of the board is used and no extra foamboard material was added.

Here are the plans:

This is the bottom side.  

You can right click anywhere on the drawing and print.

The lines marked "S (R)" will have to be transferred and scored on the other side at some point.

Note:  Dollar Tree Foam Board is not exactly 20" X 30 ".  My current stack actually measures 29 7/8" X 20 3/16".  That is why some dimensions are shown "+/-".  Any measurement discrepancies should be made up in the "+/-" measurements.

Note: The elevon dimensions in parentheses were used on my build #3 for more elevon authority,  better high alpha and possible 3D performance.  I will test both versions in the spring.  Either version should work for normal flight with proper throw adjustments. I will use 50% throws for the initial settings for this version.

Well, let's go ahead and build one.

LAYOUT:

Print a copy of the drawing.  Transfer measurements directly to the faom board in this order:

1. Measure the center of the 30" (+/-)  dimension and draw the center line.  Use half of the actual measurement rather than 15".

2. Lay out the tail fins.  Measure 5" from the center line each way along the bottom edge.  Draw a 5" line at 90 degrees from the edge with a tri-square at each mark.  Put a mark at 5" on each.   Mark 3" up from the bottom of the sheet along the centerline.  Draw lines connecting the 5" amd 3" marks. 

3. Lay out the fuselage nose end.  Measure 13 1/2" from each corner along the top edge of the sheet.

4. Lay out the fuselage tail end.  Measure 3 1/2" each way from centerline and mark each of the angled lines of the tail fins.  Draw a line between the two marks.  The resulting small triangles will be the tail skids  

5.   Draw the fuselage fold lines.  Connect the marks from  steps 3. and  4.

6.  Measure 13 1/2" down from the top corner along each side.  Draw two lines connecting these marks with the marks in step 3.  These are the leading edge fold lines.

7. Lay out and draw the elevons.  Measure 9" in from each corner along the bottom edge. Use a tri-sqare to draw two 1 1/2" long lines on these marks at 90 degrees to the edge.  Put a mark at the 1 1/2" point.  Measure  and mark up 2 1/2" from each lower corner along each side.  Draw lines  connecting these marks with the ones at the end of the 1 1/2" lines.

Note: For my third build I increased the width of the elevons by 1/2" to increase the potential for high alpha / 3 D performance.  Those measurements are 2" and 3" instead of 1 1/2" and 2 1/2" in step 7 above..

8.  Lay out the secondary fold lines for the tail fins.  Measure 1/2" toward centerline at two places on each side from the 5" tail fin fold lines.  Draw in the secondary fold lines.

9.  Measure for removal of the paper on the inside of the fuselage to allow the required twisting. Measure 3" up from both sides of the 7" rear of fuselage line and draw a parallel broken line across stopping about  1/2" from each angled fuselage fold line.  Measure 1/2" toward the centerline at two spots on each side from the angled fuselage lines.  Draw in two broken lines from the nose to the first broken line.  

7.  Check the drawing to be sure you have all lines drawn properly.

It should look something like this:

 Note: This layout is from the first build where I did not leave the paper in for the motor mount area.  There should be a horizontal broken line 3" up the sheet from the two small triangles in the center.  The two longer broken lines should stop there. 

CUTTING AND SCORING:

Transfer all of the "C" (cut), "S" (score) and "S R" (score reverse side) notes to the foamboard.  

Cut all of the "C" lines making sure to stop sharply at the intersections.  You will end up with the elevons and two small triangles as loose pieces.  Save both.

After cutting it should look like this:

Score cut the "S" lines from this side.

Carefully transfer the "S (R)" lines to the opposite side of the sheet and score cut those.  The easiest way to do this is to line a knife up with the line on the first side and roll up to make a small cut on the second side.  You can fold the tail pieces up out of the way to get the back ends of the angled fuselage fold lines.

After making all of the score cuts, cut just throught the paper and remove the back side paper in the fuselage area up to 3" from the tail.

After that we have to double 45 degree cut some of the score lines and deeply crease the others.  The easiest way to indicate which is which is to look on the  pictures below after it is done:

.  

The bottom side:

The centerline and the two leading edge fold lines are double beveled.  That is everything for this side.

Note: This picture also shows the paper removed on the inside of the fuselage all the way to the back.  As noted above it should remain on the motor mount area which is the 3 " area just above the triangle cut-out. Just barely cut through the paper so that it does not tend to fold on the removel line. On the third build  I also added a skim of hot glue to reinforce the cut and keep the 1/2" wide paper strip from coming loose.  Like this:

The Top Side:

The first joint of the tail fin is double beveled.   The second tail fin joint and the fuselage side joints are scored and deeply dimpled with a rounder pen tip.  Like so:

ASSEMBLY:

Assembly is a little misleading because most of the parts are already attached.  They just need to be folded and glued into the final configuration.   Fabrication may be a better term.

Fuselage Fabrication:

We start by folding the centerline over all the way flat to pre-stress the top of fuselage fold line.  This is where the twisting will happen so pre-stressing is very important.  Fold it over and hold it flat for a minute or so to allow the foam to compress.  Like this:

Fold it back open and apply a generous bead of glue right in the center of the joint.  Also put some along the whole width of the front end about an inch wide where it will be folded completely over on itself.   Then fold it back over but only hold the front tight.  The back end will flex to about 90 degrees if you just hold the front.  Use a clamp with a couple pieces of gift card or cutting board material to soften the bite.  Hold a tri-square or any square object inside the fuselage at about 3/4" from the back end (motor mount location) till the glue sets  Like so:

This picture shows the front  clamp in place and the shape we are going for.

Motor Mount:

Next we have to install the motor mount to hold the back end of the fuselage at 90 degrees.  The motor mount is a piece of 1/8" plywood cut to 2 1/4" square and then one corner is cut off.   It looks like this from the back:

First measure and cut the 2 1/4" X 2 1/4" square with a hobby knife.  Then measure 1 1/4" each way from one corner, connect the marks and cut the corner off.  

Measure and draw two lines, one on each face of the inside of the fuselage at 3/4" from the back edge.  Glue the motor mount in on the lines.  

Next cut three small blocks of 1/8" plywood 1" X 1/2" each and glue then in front of the motor mount to brace it and secure it to the fuselage.  They should be glued generously to both the faomboard and the motor mount in the positions shown below:

Now the fuselage will not flex while we do the rest of the fabrication.

Wing and Tail Assembly:

The next step is to fold and glue the fuselage-to-wing folds.  The nose clamp should stay on while doing this.  Take the fuselage and push it down onto the table forcing both wing panels to lay flat.  Like so:

Both tail pieces should be toward the center instead of one folded under like I have in this picture.  Pick it back up and let the wings sag back down.  Place a moderate bead of glue in the joint on one side and quickly push it back down flat. Immediately squegee the excess glue.  Hold the fuselage down and place a couple of scraps of faomboard under the wing tip. The wings tend to flex back down a bit after gluing and this helps to make them end up straight.  Run a second pass of glue over the joint and squeegee again..  Hold a couple of minutes till the glue is firmly set.  

Repeat the process on the other side.  Keep the scraps under both wing tips till the second side is set.

Next we will set the tail fins.  Begin from the previous position but remove the blocks under the wing tips.  Everything should lay flat.  Fold both tail fins up and check that they will go to 90 degrees easily.  Trim if needed.  Spread a moderate bead of glue right in the bottom of the joint.  Fold it up and hold it with a tri-square.  Quickly squeegee the excess.  Make sure that the bottom 1/2" is against the square.  Hold about one minute till set.  Run a second pass of glue over the joint smothing it with the gun tip to a neat bead.   It should look lke this.

Next use a 68 degree angle gage (from F-22 fins) or make one using a protractor.  You will need to cut off the corner about 1/2" each way because of the double bend.  Spread a moderate bead of glue in the second joint and quickly fold it to the approximate angle of the gage. Squeegee the excess and then adjust the angle with the gage.  Hold till set.  Like so:

Repeat the process for the second fin.

Adding Tape for Radio and ESC Velcro Attachments:

I did not do it on my first three builds but it would be much easier to tape the area inside the fuselage where the radio and ESC will be installed now while it is open.  Start from 6" from the nose and go to 12".  Put one or two pieces of packing tape 6" long on each side to cover the bare foam. Do not go any closer to the nose because you will need to melt out some foam there to make room for the battery.

Back to wings: 

Next we will fold the wing bottom panels under and establish the 45 degree leading edges.  Pick the whole airplane up and fold both wing bottoms under.  Press it back down to pre-stress the leading edge joints. Like this:

Note that the nose clamp  still in place. . 

Flip it back over and open one side. Spread a generous amount of glue along the leading edge joint, around all edges and squiggled about every 3" through the middle.  Quickly flip it back over with both wing bottoms folded.  Hold even pressure over the entire glued side for about two minutes till set.  This will take a little longer than usual becuase the glue is enclosed and insulated.  It will look like the picture above except use both hands for complete coverage of the glued area.

Repeat this process for the second wing.  Again, it will look like the picture above.

The plane has now taken it's form.

Installing Elevons:

The elevons are the two larger pieces left from the cutting operation.  They just get flipped end for end and front to back and get reinstalled where they were cut out.  The wider end goes toward the center and the square corners go toward the front.  After determining the location and orientation make 45 degree bevel cuts on the bottom leading edge of each. Like so:

Then attach them to the top side using a piece of packing tape as the hinge.  Here is a picture of the installed elevon on one side:

Spread a very thin bead of glue in the hinge line and squeegee it out to help avoid delamination in the hinge joint.  I also like to run the glue gun tip right down the joint to melt out excess foam and to spread the glue as thin as possible.  This works if you have a tapered tip (rubber tip removed) like this "Ad-Tech Pro 100" I got from Wal Mart (nice gun at a good price):

Bottom Details:

Next we have to do a couple of details on the bottom side.

The first step is to add a skewer across the gap at the back edges of the wing bottoms.  This stiffens the bottom and locks in the spread between the two wing bottom panels.  Take a skewer that has some natural bend to it.  The trailing edges are at a slight angle and the bend can follow it.  Trim off the pointed end.  You should have about 11" left.  Measure and mark the center.  Hold the skewer in place with the mark in the center of the wing gap and mark both ends.  Spread a moderate bead of glue in the joint and along the edges of the bottom panel where they extend over the fuselage gap. Press the skewer into the glue with the curve following the angle between the two wing bottom halves. Hold till set. Smooth the glue down with a wet finger or foam scrap.  Add a neat bead along the back edge of the skewer and along the back edge of the wing bottom panels all along. It should look like this:

Next we have to lay out and cut holes for the running gear.  These dimensions are based on using a 1500 3S battery as far forward as it will go for balance.  The dimensions I used are shown in the following photos.  All measurements start at the tip of the nose.

The first hole goes from 2 1/2" to 6 3/4" and is 1" wide.  It is for the battery:

The second hole runs from 7 1/2" to 9 3/4" and is 1 1/2" wide.  It is for the receiver and ESC:

The third hole runs from 10 1/4" to 11 1/8" and is 7/8" wide.  It is for the two 9 g servos: 

All holes are centered on the wing gap.

Here are the holes cut out:

I have used scraps from the radio cut-out to reinforce the gaps.  Just glue to the bottom side.  The front one will need trimmed about 1/4" for length.

The hole for the battery runs forward enough that it is a tight fit for the battery.  You can take a butter knife heated with a heat gun or over the stove (I use a small pie lifter and heat gun) and gently melt the foam away to make room on each side toward the front.   Not too much and not too hot.  You just want to take about half of the thickness of the foam and not get hot enough to show on the outside.  You can see the melted area in the front opening in the photo above.

LANDING GEAR: 

Main Landing Skids:

The main landing skids are made from one full length of 21" flag wire.  They are bent and installed in such a way that spring tension helps cushion the landings.  

Start by removing the flag and finding the center.  It should be at 10 1/2".  Make a 90 degree bend at the center.  Measure 1 1/2" along each side and make two additional 90 degree bends so that the original bend can lay flat and the two ends stick straight up.  Twist this arrangement so the two ends sticking up angle out at about 10 degrees to each side.  It should look like this:

Next on each side make a series of gentle bends so the half of the wire nearest the second bend makes a gentle arch of 90 degrees in about half of the remaining length.  The second half should stay straight.  The bends should go in the same direction as the first bend is pointing.  It should look like this:

Next make the end bends.  The first is about 1/2" long (width of large needle nose jaws) and bends up.  The second bend is about 1/4" (needle nose tip) and bends back down.  They should look like this:

Next we have to prepare slots to receive the front of the gear.  First mark 1 1/2" each way along the leading edges from the nose.  Hold the gear on the marks and trace both sides of the wire on each side:

The two second bends should match the leading edges.   

Make knife cuts through the paper centered on the marks on each side.  Use a skewer to open slots on each knife cut:

Fill the slots with glue.  Insert the gear and push all the way down.  Refill the slots with glue and squeegee the excess:

Next make a plywood cover plate to reinforce the attachment.  It is a piece of 1/16" plywood cut to 1 3/8" X 3" with two corners trimmed at 3/8" each way.  The larger piece should be cut with a hobby knife and straight edge but corners can be cut with a sharp pair of scissors.  Spread a generous squiggle of glue covering about half of the back surface and then press into place.  The goal is to have a full bed of glue without pushing out the sides.  Squeegee off any that pushes out.  You do not need to run a bead around.  It should look like this:

Now we have to make sockets to receive the other ends of the skids. They are made from triangles of cutting board material ot gift card material glued in place.  

First cut a 1 1/8" square.  Then cut it diagonally with scissors to make two equal triangles.  Drill the center of each with a 5/64 bit.

Measure 3" each way from the center line and 2 1/2" square back from the leading edge on each side of the bottom of the wing and mark the intersections.  Glue the triangles over the marks with the holes on the marks.  For appearance sake make them point toward the front.  They should look like this:

Try to get a full bed of glue under each triangle without too much squeezing out.  Use a skewer tip to pierce the paper then insert the gear ends.  The finished product should look like this:

You may have to do some hand forming or tweeking with pliers to get them to look uniform.  It takes some practice.

Tail Skids:   

The tail skids are made from the two remaining small triangular pieces from the cutting operation.  

First measure two spots 2" from the wing tips just in front of the elevons and just behind the wing bottom panel on each side.  Glue the longest side of each triangle down on the marks.  The shortest side of the triangle goes to the back and should go just to the elevon hinge joint.  Squeegee both sides and then add a neat bead of glue on each side, smoothing with the gun tip.   Like so:

Next measure 1 3/4" from the back edge of the skid support and make a skewer hole about 3/4" deep.  It should be square with the bottom edge of the skid and just pierce the first layer of paper on the wing. Avoid piercing the top of the wing or pushing far enough that it marks the top.   Like tihs:

Use the tip of the glue gun to melt a slot from the hole to the back of the skid support.  Like so:

Then make the wire skids.  First cut two pieces of flag wire 4" long.  Make a 90 degree bend at 1/2" from one end on each.  Like this (lower right):

Next leave the first 1 3/4" from the bend straight and make a series of gentle bends to form a gradual arching bend through the remaining 1 3/4" of each piece.  The arched bend should be in palne with the 90 degree bend (it should be able to lay flat).  They should look like this:

Do a dry fit to make sure your hole is deep enough and at the right angle. Then fill the skewer hole and the slot with hot glue.  Insert the 90 degree bend into the skewer hole and lay the straight part in the glue pushing it down to the bottom of the slot.  Smooth the glue over with a wet finger.  Be quick so the glue does not have time to dry the finger and stick (and burn!).  Run another bead over the top and smooth it down as well.  The finished product should look like this:

There is quite a bit of glue over the wire.  

RUNNING GEAR:

Next it is time to install the running gear.  The completed insallation should look like this:

This picture is from my third build with the wider elevons. The gear insallation should be pretty straight forward and can probably be completed from the picture.

Here are a couple of pictures of the servo, push rod and control horn instalation:

GEAR NOTES:

I will add just a few gear installation notes:

1. The battery should be flush with the bottom or very close.  

2. The long black velcro is double-sided from Harbor Freight.  One side is glued on and the other has a short hooked piece glued on under. Similar products are available at Lowe's or Home Depot.  

3. I put 3 velcro loop squares on each side of the battery to make a snug fit and eliminate movement and vibration.

4. There is a long self adhesive velcro strip (about 3" each) for attaching the receiver and ESC in each side of the radio bay.  A series of 1" squares will do.

5. The control horns are made from cutting board material or gift cards per my related article below.

6.  The adjustable push rods are made from flag wire per my related article below.  Make sure they clear the prop. Mine clear even though they do cross corners of the prop space. It is better to put the "V" bends closer the back making them more effective for twisting the wire into the control horn.

7. My motor and mount are straight.  It might benefit from a little down thrust since it is mounted above the CG.  A washer or two under the lower screws should do it.

8.  Elevons should be set with about 5 degrees positive as an initial setting.  They can be tweeked from there after trimming out on the initial flights.

SPECS:

Length: 21"

Span: 27 1/2"

Wing area: 2.3 SF

Weight (with gear & battery)  453 g / 16 oz.

Wing Loading:  7.0 oz per SF

Thrust: ( with the listed gear)  560 g. at 14 A

CG:  8"(mild) - 9" (sporty)  from nose.  (I added 4 quarters in the nose and got mine about 8 1/2")

Flight time (anticipated): 8mi. at full - 12  min. av.

 GEAR:

My gear includes the following:

Motor: Turnigy 2826 -10  1400KV

Prop:  7038  

ESC:  30A w/ BEC (20A would do)

Servos:  (2) 9g Tower Pro SG90

Battery: 1800 3S 25C (151g.)

Radio: FlySky FS-T6 (any radio with "Elevon" function or mixing will do) (dual rates and expo a plus)

SET-UP:

The only set-up adjustments available are for the elevons.  My initial set-up has the push rods on the last holes on both the servo and control surfaces.   For the standard elevon version (1 1/2" and 2") I am using 65% Rates and 50% Expo. for both channels.   I am using 5 degrees positive (reflex) for the initial set-up.  The net elevator throws are +15 degrees and -5 degrees.  I will tweek it from there.  For the enlarged elevon version (2" and 3") I will start at 50 % rates.

This is a quick build and the gear is very reasonable.  Why don't you give it a try?

Please let me know if you do.   Send pictures to: dkark69@gmail.com

UPDATE 3-1-15:

I had received a comment from phacious saying that he had built and flown one of these with neon lights added.  And get this, his maiden was a night flight.  Now that is confidence.  Evidently all went well and he was kind enough to send some pictures:

You may note that he arranged his gear a little differently.  Hey, whatever works for you.  Didn't he do a spectacular job? I think the lights are really cool.  Nice work!  

Thanks phacious!

End of update.

Good luck with your spring flying!  It is not that far away,

Dan