One Sheet No Waste Simple Fold Delta - EDF Version

Hello Guys & Gals,

Yes, there are a few Gals out there.  We need to bring more in.  I see a lot of family involvment in articles on this site including little girls playing aiplanes with their Daddy (and/or Mom).  That is a great potential change for this hobby for the next generation. There is no reason our daughters should not aspire to the sciences including aeronautics.  

Well, enough philosophy...

This  article describes the EDF version of the "One Sheet No Waste - Simple Fold Delta" that was featured in my recent article.  The notion of an EDF version popped into my head pretty early in the development of the prop version.  There was just this large cavity at the rear of the fuselage that fairly screams, "Hey, there is room for a screamin' jet here"!

PROTOTYPE:

Here are a couple of pictures of the first build resuts:

Originally I was planning to do a short article just describing the differences between this version and the prop one and actually got most of the way through writing it that way.  It was just not coming together in a way that I thought would be easy to build from.  I decided to back-track and make this a stand-alone article rather than require the reader to reference two articles at once and figure out the differences.  

Here is the revised plan:

Left click on the picture to select and then right click to print.

This is the same plan that was used for the prop version except for the air inlet details added at the center of the page and the additional cut-outs on the bottom wing panels to accomodate the EDF at the top right and top left corners of the drawing.  

The building sequence has a number of quirks specific to this version so we are going to start from scratch.  

Well, let's get started:

LAYOUT:

NOTE: I USED THE LARGER ELEVON DIMENSIONS SHOWN IT PARENTHESES FOR THIS BUILD.  If you have a radio with dual rates and expo you can set lower rates for normal flight and higher rates for sport. If you do not have dual rates I would suggest using the smaller elevons.     

The first step is to print the drawing and then transfer all the dimensions and lines to a sheet of Dollar Tree Foam Board.  Some of the lines will actually be transferrred to the other side before they are used but I think it is good to see everything on one side to start.

It should look like this:

Carefully mark all lines designated "S(R)".  These are the ones that will NOT be cut or scored on this side.

CUTTING - FIRST SIDE (Bottom):

Cut and score the remaining "C" and "S" lines respectively.  When you are done it should look like this:

Then do the bevel cuts and deep creases.

The center line and the wing leading edges are double beveled at about 45 degrees.

The "S" lines on the small triangles at the middle are deeply creased with a rounded object.   Like so:

These pictures are from another build just showing the technique.  Run the rounded tip over the score lines three or four times with firm pressure till you depress the foam all the way to the paper on the other side. 

The paper is barely cut through and removed inside the dashed lines on the two areas that will become the insides of ther fuselage (allowing the fuselage sides to twist).  Two inches are left at the rear of the fuselage for engine mounting.  One inch is left at the nose for gluing the tip of the nose together.  Paper is left on the small parts of the fuselage bridging the air inlet for support while twisting..

The cut lines where the paper was removed need to be reinforced with hot glue so they do not bereak in the twisting that forms the fuselage. Just run a light bead along the edge of the paper and squeegee it down tight.  Do all edges that are not also a "C" line.  Not too heavy.  The hot glue will melt the bare foam.  It is best to lay the bead on the edge of the paper then push it over onto the foam as it cools a little.   Like this:

LAYOUT - SECOND SIDE (Top): 

Turn the piece over and using a knife at the edge of the sheet, transfer the double tail score lines to the other side.  Hold the knife on the pencil mark and roll it up to make a small cut on the second side directly opposite the pencil mark.  Use a tri-square to draw two lines up to the cut line on each side.  Score these 4 lines and then fold the two tail pieces back under.  This gives you access to transfer the rear fuselage lines from the back side to this side (the top).  Use a knife at the edges of the sheet again to transfer the layout from the other side.

CUTTING AND SCORING -SECOND SIDE (Top):

Score the sides of the fuselage making sure NOT to continue through the air inlet area.

Double bevel cut the first fold  line on each tail fin (the line closest to the wing tip).  Deeply crease the second line at the tail and both sides of the fuselage.

Make sure all of the cut lines came through this side cleanly.  Use a hobby knife to make sure the corners are all cut free and the parts move freely.

When you get done it should look like this:

Note:  The only double bevel on this side is the FIRST bend on each tail fin next to the aileron cut-out..  The second bend is just a deep score as are the sides of the fuselage.

Now we are ready to start the folding process.  It begins with the twisted fuselage. 

FOLDING:

The first fold is the tricky one.  It will form the fuselage into a twisted triangular tube.

The joint needs to be pre-stressed so that the foam is ready to form the angles easily.

Turn the piece bottom side up.  Then fold it completely over on itself at the middle line.  You will need to support the middle details to make sure they fold evenly with the remaining length.  Hold firm pressure for a minute or two till the foam compresses and relaxes. Like so:

I am using one hand so I can take the picture.  Use both hands to spread the pressure over the whole joint.  Pay special attention to the middle part with all the cuts.  Keep everything in alignment and flat for now.

Next, unfold the center joint and spread glue first on the 1" paper left on the front tip and then a generous bead inside the double bevel joint down the center line all the way from front to back.  Fold it back over but this time fold it all the way tight only at the front tip. Use a couple of hard pads like gift card or cutting board material and a clamp to hold the nose together.  A meduim binder clip or a couple of spring clothes pins would work for this.  Let the rest of the joint flex till the back end of the fuselage is at about 90 degrees.  It should look like this:

Next (while the glue is still hot) push it down to the table while spreading the wings out and carefully making sure the air inlet pieces slip freely through their cuts.  They will now be inside the fuselage as the wings continue to push down flat.  After the wings are flat push them together till the two halves of the air inlet bottom meet in the middle.  Hold this position for a minute or two till the glue sets at the top of the fuselage.   When you release it the wings will flex back some but the fuselage should hold it's shape.  Like this: 

 Make sure the two wing panels come together in the middle.

When the fuselage has set pick the plane up and fold the lower wing panels in.  Ideally they should meet at the bottom all the way along the joint while the top wing surfaces meet in the air inlet.  If the top wing surfaces meet first and keep the bottom panels from coming together, use the bottom panels as a gage to trim the top panels to match.  If the bottom panels come together first a little can be trimmed from each side of the lower wing panels (half of the total overlap from each) with a straight edge till they just meet. 

When you are satisfied with the fits between the top and bottom wing panels it is time to glue the fuselage side joints.  Set it up again with the wings unfolded and the fuselage pushed down to the building board.  This time place a 1/4" to 3/8" spacer under each wing tip.  I used scraps of 1/4" plywood but two layers of scrap faomboard on each side will do.  The point is to flex the wings upward as the fuselage sides are glued because they will flex back a little when you release them. It will look like this (again):

Pick if up and spread glue in the fuselage side joint on one side.  Push it down to the table again.   Make sure the blocks are under the wing tips and that the upper wing panels are tight together in the air inlet gap.  Immediately squeegee any excess glue.  Hold for a minute or two till the glue sets.  Repeat with the second side.  Take the blocks out from under the wing tips. The wings should now lay pretty flat on the table.

Turn it over.  From the bottom the top wing joint should be tight.  Flex the joint open and place a moderate bead of glue in the joint.  Let it spring back tight or push it together if necessary and squeegee any excess top and bottom. Place the wing back flat on the building board and make sure the two panels meet up for height as the glue sets.  Hold for a minute till the glue sets.  

Turn it back over and add 3 layers of tape across the joint.  The first should be about 2" long, the second about 4" and the third about 6".  Keep the tape toward the front because the back part will be cut out later.  Like this:

This picture shows applying the second layer.  This joint needs a lot of strength since it will be the main connection between the wings.  At this point you should also add glue to fill in any gaps in the fuselage top joint.

Next fold the two lower wing panels back over the bottom.  They should meet as a tight joint in the middle.   If there is a small gap it is OK.  The joint can be filled with glue. Fold them back open one at a time and spread glue in the leading edge joint and on the bottom wing panel. The glue should go about 1" from the edges all around plus a generous squiggle through the center.  Like so:

Quickly fold the wings back together and immediately press it down firmly to the building board.  There will be no spacers under the tips this time.  Hold firm pressure with both hands over the whole glued area for a couple of minutes till set. Make sure to hold extra pressure toward the nose.  It tends to flex up more there.   This will take a little longer because the hot glue is enclosed in foam insulation.  Like this (but use both hands - I needed one for the photo):

When the first side is set repeat with the second side. Also spread a moderate bead along the edge of the first wing at the center joint (not enough to squeeze out). Fold it together and squeegee any excess at the joint.  Repeat the holding down procedure.  When you release this it should be rock solid and dead flat.     

After both wings are glued flip it over and cut out the triangle on the top wing to match the cut-out on the bottom in front of the EDF position.   Use a straight edge and draw lines from the corners of ther upper wing opening parallel to the lower wing opening on each side.   

Cut out with the straight edge and hobby knife.

Top View: This will allow more free air flow to the EDF.

There are two triangular pieces in the air inlet that need to be set into place.  These will make a channel for the ESC wires and help divert airflow to the EDF.  First fold them out and spread glue in as much of the joints on each side as you can reach with the glue gun.  Then push the two lower tips together and center them in the opening as seen from the bottom. Hold till set. Like this:

Finally, trim a wedge of foam off each side to make a slot for the wires.

Next we will glue the tail fins.  Fold both up out of the way.  Spread a moderate bead in the first (double bevel) joint and hold it vertical with a 90 degree gage.  Squeegee any excess glue.  Add a neat bead to the glue side with the glue gun.  Hold till set.  Like this:

Spread a lighter bead in the second joint and fold into the approximate angle before squeegeeing any excess.  Imediately hold in place using an angle gage cut for the purpose.  I used 68 degrees because I had it from a F-22 build.  You can also use 60 degrees from 30/60 a triangle.  Make sure to make the angle gage it ahead with the corner trimmed off so it fits into the double bend corner.  Like so:

Repeat for the other fin.  

Turn the plane over and add a small neat bead of glue along all of the joints between the upper and lower wing panels.  Use the gun tip to smooth them.

INSTALLING ELEVONS:

The elevons are installed in the same locations they were cut from but they are reversed front-to-back and end-to-end.  The square corners that came from the back go to the front.  The wider end that was cut from the outside corner flips to go on the inside next to the tail fins.  This changes the trailing edge from what was a square sheet to tapered on both sides for a more dynamic look.  They will look like this:

Closer up they should look like this:

Once you have the locations and orientation established make a 45 degree taper cut on the bottom leading edges of the elevons.  Then attach them with strips of packing tape cut to the full length of the elevon and centered on the hinge line.  Reinforce the joint with a light skim of hot glue inside the bottom of the joint squeegeed out tight per the FT method.  

EDF ASSEMBLY:

The EDF I am using is 64mm in diameter (inside diameter).  The exhaust tube is made from a small powdered creamer bottle (mine is a 15 oz. from Aldi's but I think most generics are he same).The bottle is cut at 1/4" and 5 1/2" from the bottom.  The bottom cut just fits over the EDF inlet end.  The middle cut is at the narrowest piont of the bottle and matches the ID of the EDF at 64mm.  

15 Oz. Creamer bottle.

Find a suitable object the right height and then rotate the bottle to mark.

Ready to cut.

The EDF is inserted to determine the location where the wires will exit and a small rectangular hole is cut for the wires.   The EDF is reinserted with the wires exiting the hole and the tube is attached to the EDF with hot glue all around.  This makes a light, durable, compact unit that can be moved from model to model easily.

Here is a picture of the assembled EDF sitting roughly in position:

EDF SUPPORTS: 

The fuselage has to be prepared for the EDF installation.  A bulkhead needs to be made to receive the back end of the exhaust tube and some room needs to be made at the front to allow the EDF end to recess half way into the fuselage.

First find a suitable piece of scrap and trace the rear fuselage opening:

Cut the triangle and then find the center of the open side.  Draw a half circle 65m in daimeter (or to match your exhaust tube) and cut it out.  I had made a template for the prototype so I was able to trace that.

 You also need to trim about 1/4" off the tip that fits into the fuselage.  That will provide an opening for the antenna later.

Apply hot glue to the two srtaight edges and fit it into place even with the back of the fuselage:

Squeegee any excess off the outside and add a moderate bead on the inside of the joint.

Next make a piece 1" wide and 2" long with 45 degree cuts on both ends.  This will glue in as shown to make a compartment for the receiver.  Make sure it does not interfere with the EDF exhaust tube.  Trim it a little shorter if necessary.  It should be just a little short of the circle.

Next we have to make a little extra room for the front end of the EDF to recess into the fuselage. (This may not be necessary if you are using a smaller diameter EDF).  Trial fit the EDF and note where the radius of the front end of the EDF hits the sides of the fuselage.  Mark the tightest spot on each side.  Also note that the centerline of the EDF is below the bottom of the wing.  The goal is to melt enough foam from the inside of the fuselage to let the EDF move further into the fuselage till the center of the EDF is even with the bottom of the wing. remove the EDF and use a large spoon heated with a heat gun or over an electric range  till it will just melt the foam. Melt a shallow dished area where you marked the tight spot.  You should melt about half the thickness of the foam and then do a trial fit.  Go a little more if necessary.  Be.careful not to use too much heat or melt too deeply so that it shows on the outside.  It souold look something like this:

BATTERY COMPARTMENT:

Next we will make the battery compartment. 

The battery goes as far forward as possible in the fuselage. It is inserted from below and recessed into the tapered nose of the fuselage as far as possible.  I have chosen an 1800 3s which is a little bigger than the prop version took.    The EDF takes more power and also needs more nose weight.  The 1500 3s used on the prop version recessed flush with the bottom. This battery will hang down about 3/8" below the wing.  It will have a tapered block of foamboard on each side with two velcro straps across to keep the battery snug in place.

The first step is to lay out and cut the battery recess hole. It starts at 2 1/2" from the nose.  It is 4 1/4" long and 1" wide.

First layout:

Then cut: 

The pencil marks in the picture above show where the 1/2" wide paper will have to be cut away so the foam can be melted in that corner. Enough foam needs to be melted to allow the 1800 3s battery to recess into the fuselage all but 3/8".

Next we will make two tapered blocks for mounting the velcro straps.   They are made from the two larger pieces cut from the corners of the lower wing panels in the initial cutting stage.  

First mark a center line along the longer dimension.  Make a very shallow cut on the line just through the paper.  Then let the blade follow the cut sideways to slice a tapered wedge piece off.  Like so:

The heal of the knife is following the paper on the other side as closely as possible.

Flip the tapered wedge over and glue it onto the other half to make a tapered pad the full width of the original piece. Some trimming or sanding may be needed to even out any humps. It should look like this:

Trim the ends of the smaller piece flush if needed.

Make a second one from the other cut-out piece but the opposite hand.  

The two wedges are glued down with their thick edges next to the hole and the wider part toward the back. Run a bead of glue all around.  Like so:

You can also see the melted areas of foam at the front corners on each side.

Here I am using a small pie lifter heated with a heat gun (you could also use a kitchen knife heated over the stove) to melt the foam away to make room for the battery to recess into the fuselage.  Be careful not to get too hot or hold too long.  You do not want to make a dent on the outside.  Melt away about half the faom thickness on each side and then check the fit.  Melt a little more if needed.

EDF STRAPPING: 

Next we will install the velcro strapping to hold ther EDF and battery in place.  The material I use is hook on one side and loop on the other.  It is 3/4" X 35' "Hook and Loop Strapping" and costs about $7.00 from Harbor Freight (1/2 X 30' Velcro brand $15 at Lowes or Home Depot).

For the EDF we will need two pieces 3 1/2". two pieces 1" and one piece 5".  The two 3 1/2" pieces have half of their lengths glued to the inside of the fuselage.  They are glued at an angle toward the back where the fuselage is wider so they do not interfere with the exhaust tube.  Here is a picture with both installed:

Spread glue on about 1/2 of the length on the loop side and then press into place aligning with the corner of the receiver compartment and the back corner of the lower wing panel.

This shows glue spread just before installing.  We want enough for full coverage when it is pressed into place.  

Next place the EDF in place with the wires centered in the top corner of the fuselage (straight away in the picture). The front of the EDF should be about 1/4" behind the edges of the air inlet openings and the back of the exhaust tube should be about 3/8" past the rear support.  Then place the two 1" pieces of velcro on the glued in velcro straps in the positions shown.  

Spread glue on the sides of the 1" pieces toward the EDF one at a time and press them against the sides of the exhaust tube.  Hold till fully set.. Then gently peal the ends of the 3 1/2' pieces back and roll the EDF out.  Run a small tight bead of glue all around the edges of the 1 " squares to solidly secure them to the exhaust tube.  Reinstall the EDF.  Pull the ends of the 3 1/2" straps around while holding gentle pressure on the exhaust tube till the hooks and loops engage.  The EDF and exhaust tube should be held securely in place with no wobbling or slack. It should look like this:

Then take the 5" piece and attach it to the outside of the 3 1/2" piece on one side.  

 Pull it snugly around and attach it to the outside of the one on the other side: 

The end result is a full wrap of velcro strapping and the EDF should not move.  If you can wiggle it at all loosen the straps and reinstall them more snugly.  

BATTERY STRAPPING: 

 The battery strapping is considerably less complicated.  We will need two pieces 4" long and two pieces 1 1/4" long.  Attach the hook side of each 1 1/4" piece to the loop side of one end of each of the 4" pieces.  Like so:

Loop side up. 

Next spread glue on the 1 1/4" piece and on about 1 1/4" of the far end of the 4" piece.  Then press them in place spanning the battery hole and attaching to the tapered blocks on each side.   The two 1 1/4" pieces will end up glued to the tapered block on one side and one end of the 4" piece will be glued to the tapered block on the other side.  One will be toward the front of the battery hole and the other near hte back.  They should look like this:

The one in the front is opened and the 4" strap is rolled onto itself ready for the battery to be installed.  The one in the back is in the closed position.

LANDING GEAR (SKIDS):

Tail Skids:

These planes are easily hand launched so the landing gear consists of simple skid arrangements meant to protect the belly of the plane from damage in belly landings.   They are light weight, aerodynamic and are not very noticable when flying.  

The tail skids are made from two short pieces of flag wire mounted to the two larger triangular pieces (3 1/2" X 1 3/8") left from the original cut out.

The two triangles are first glued to the bottom of the wing just ahead of the ailerons and 2" in from each wing tip.  First make two marks on the bottom of the upper wing panel at 2" from the wing tip on each side  Like so:

Then glue the longest side of the triangle (the diagonal) down on the marks.  Like this:

Run an exta bead of glue on each side for extra strength. 

Next measure 1 3/4" from the back corner of the skid support and use a skewer to pierce a hole at 90 degrees to the bottom edge of the skid support.  The hole should pierce the whole thickness of the triangle plus the first layer or the upper wing paper but not the second (top) layer.  It should look like this:

Next we have to make the two wire skids.  Start by cuttintg two pieces of flag wire 4" each.  Use the wide end of a large needle nose pliers to make a 90 degree bend at 1/2" from the end of each one.   Measure 1 3/4" from the bend and make a mark.  This portion will stay straight.  The remaining 1 3/4" will receive a series of slight bends creating a gentle arch of about 15 degrees in it's length.  Make two.  They should be able to lay flat on their sides and should look like this:

Next we have to prepare a slot in each of the the skid supports to receive the wire.  Take the tip of your glue gun and carefully melt the foam from between the two layers of paper from the skewer hole to the back corner of the support.  Like this:

Do a trial fit.  The bent end should fit into the skewer hole and the straight part should lay in the melted slot:

If all looks good remove the wire.  Fill the skewer hole and the melted slot with glue. Immediately insert the wire and push it down to the bottom of the slot.  The glue will push up on each side.  Wet your finger and smooth the glue down over the wire.  This may take two or three strokes and you should wet your finger before each.  The glue will stick and burn if your finger is dry.  Use quick strokes so your finger stays wet.

Spead a light second pass of glue over the wire and smooth it down as well.  It should look like this:

Repeat on the second side.

Nose Skid:

The nose skid is made from a single 21" flag lire.  Remove the flag.  Then make a 90 degree bend at the center (10 1/2").  Next measure 1 1/2 " from the first bend each way.  Make a second 90 degree bend at each of those marks so that when the first bend is laying flat on the building board the two ends are sticking up and angled out about 10 degrees each from the center.  It should look like this:

Next start at the second bend and make a series of slight bends to form a gentle arch on each side going away from you in the picture above.  The bends should total 90 degrees in about half of the remainig length.  The resulting piece should look like this:

The remaining straight ends should be roughly parallel to the building board.

To finish the piece we need to make two bends on the end of each wire.  The first bend is about 1/2" from the end (use the widest part of a large needle nose) and is bent upward.  The second bend is about 1/4" from the first (use the small end of the needle nose)   and bends back downward.  It should look like so:

When you make the second bend the 1/2" piece that was pointing up ends up pointing the same way as the unbent wire did.  This knotch and spring tension lets the end of the wire stay anchored in it's mounting hole.

Next we are ready to mount the nose skid to the airplane.  The base of the skid mounts at the nose of the airplane like this:

First make marks at 1 1/2" from the nose along each leading edge.  Put the two bends on the marks.  The first bend should also be at the center line.  Trace both sides of both legs of the wire.  Remove the wire and make a knife cut between the trace lines on both sides.

Use a skewer to open slots on the knife cuts:

Fill the slots with glue and insert the wire base.  Fill the slots again till they are completely full.  Squeegee the excess.   Let this set well before putting any tension on the wires.

Next we have to make the anchor points for the back of the skids.  They can be made from gift card or flexible cutting board material.  These are from cutting board.  First cut a 1 1/8" strip. Themn cut a 1 1/8" square from a 1/18" strip.  Then cut it daigonally into two equal triangles.  Finally drill a 5/64" hole in the center of each.  You will have two pieces like the ones on the right below:   

Next lay out the positions on the bottom wing.  They are mounted 6" apart and 2 1/2" from each leading edge.  First hold the rule at the back of the battery slot with 3" on the center line.  Mark 0" and 6".  

Then measure 2 1/2" from each leading edge and mark the intersection of the two measurements.

Make a dot at the intersection of the two dimensions and glue the two triangular pieces so that the drilled hole is on the dot.  Keep the two long sides lined up for appearance sake.  Glue the two triangles with a full bed of hot glue but trying to avoid any excess squeezing out the sides.  Once the glue is set use a skewer tip to pierce the paper.  Then insert the bent wire ends into the holes and let them penetrate the foam.  The tip will go through the two layers of paper between the wing panels but should not go through the top.

The finished nose skid should look like this:

You may have to do a little hand bending to get the curves to look uniform from side to side.

You create spring tension when you insert the wires into the anchor holes.  This makes it more rigid and lets it absorb most of the shock of landing.  It is pretty effective in protecting the under-slung EDF and servos from landing impacts.

I added a 1 3/4" X 1 3/4" square of 1/16" plywood set in a full bed of hot glue over the nose gear mounting position.  This helps to transfer the landing force to the air frame.  Run a small bead of glue all around the edges to secure it to the wing surface. You can see it in several of the following pictures.

The air frame is now complete.

GEAR INSTALLATION:

The gear installation is pretty straight forward and can probably be done by a moderately experienced builder from these photos and a couple of notes:

The overall gear installation, bottom view:

The battery and EDF with it's attached exhaust tube are strapped into position with velcro.

Close-up of battery and nose details:

 The battery is strapped in with the battery to ESC cables folded below (actually above). 

The ESC is attached to the inside of the fuselage just behind the battery:

The ESC  motor wires pass through the slot made in the fuselage above the air inlets:

When the EDF is in place the wires are in the cavity above the exhaust tube in front of the receiver.

The receiver is attached with velcro in the pocket made for it in the very top rear corner of the fuselage:

The ESC BEC wire is routed along the top corner of the fuselage to the receiver.  The servo wires are routed as shown.  The servo wires are taped down everywhere except the last loop before the  receiver.

Here is an overall view of the rear half of the underside showing the EDF strapped in place along with the servo and linkage installation:

The servos are mounted starting about 3/4" behind the front of the EDF so that the power wires will be long enough to reach the receiver without extensions.  This also makes the control wire linkages fairly short which is good for stiffness.  The only down side to this location is that we are putting weight behind the CG which will require ballast in the nose. That is a good trade-off I think.

The servos and control horns are mounted at the same angle as the control wire to minimize resistance. 

The servo holes are cut all the way through the wing and then patched the top with a piece of foamboard paper and tape.   You have to tip the servo on an angle so you can get a screw driver on the servo arm screw.  

This photo shows the servo and control linkage installation from the prototype:

The methods used are detailed in three articles in the Related Articles section below.  They are "Adjustable Wire Push Rods", "Control Horns From Gift Cards" and "Parts From Flexible Cutting Board".  

This photo shows the fully recessed servo.  The far side is flush with the wing.  The near side is raised just enough to get a screw driver on the horn screw.  

The wire is flagwire available from Lowe's or Home Depot (they are the little flags used to mark utilities on the street).  The "V" bend in the wire allows you to make fine adjustmants without having any adjustable linkages.

The green control horn is made from flexible cutting board material but can also be made from exhausted gift cards.    

CG and BALANCE:

The CG is 8 1/2" from the nose.  This corresponds to two points that are 10" apart (5" from center line) and 2 1/2" from the leading edge of the wing (measured 90 degrees from the leading edge):

I put a small dot of hot glue pressed down with a wet finger on the bottom of the wing so these can be found by feel for field balancing.

I usually try to balance by positioning gear and avoid adding balance weight.  This design does not allow that since the wings and fuselage are so strongly tapered and there was only room for the gear in certain spots.  For this one I added the weight of 6 quarters at the nose:

They are recessed into the lower wing in stacks of 3 and held in place with packing tape or hot glue.  Just position one in the proper location, trace around it and cut out with a hobby knife.  You need to remove the lower wing panel foam and both layers of paper between the wing panels to get them to come out flush.  You can also add up to 3 additioal quarters in the nose in front of the battery if needed.  I would tape them together and use a little hot glue to keep them in place.     

ELEVON SET-UP:

Since this is a flying wing it needs some positive angle (reflex) on the initial settings for the elevons. This should be about 5 degrees for an initial setting.  That is about 1 1/2 times the thickness of the foamboard at the back end ot the wing cut-out: 

The safest way is to make a 5 degree gage using a protractor.  

You can also eyeball it and get pretty close.  Just make sure both sides are the same.  

If you used the smaller elevons (1 1/2" and 2 1/2") you should increase this angle to about 7 degrees.

After dialing in trims on the maiden flight you can make final adjustments for neutral trim. 

SPECIFICATIONS:

Length: 21"

Span: 27 1/2"

Wing Area: 2.3 SF

Final Weight:  516 g  (18.2 oz)

Wing area: 2.3 SF

Wing Loading 7.9 oz per SF

Thrust: 500 g +

GEAR:

My gear consists of:

EDF: 64mm 4500 KV from Amazon (thrust test 500 g+ on 3s full charge @ 25A)

ESC: 30 A w/ BEC

Battery: 1800 3S

Servos: (2) Tower Pro SG-90

Radio: FlySky FS-6S

Receiver: Hobby King  HK GT2R (light wgt 3 channel, binds to FlySky, $7)

Update: 3-25-14: Thrust figures above revised to 500g (earlier figures had incorrectly stated 900g).  These claimed 750g but do not come close to that.  If anyone out there knows of a 64-65 mm EDF that produces significantly over 500g and is not $100 please let me know.  I would like to be in the 700 to 800 range. 

(End of update.)

FLIGHT TESTING:

I have flown the prop version for one short indoor flight in the local high school gym.  It flew well but was too fast for the small space. 

I have not flown the EDF version but it should have similar characteristics to the prop version.  As with all EDFs I would expect a little less ability to recover from bad low speed maneuvers.  EDFs just do not have the torque to punch and go like props do.  I would also expect higher top speed. Fans are made for speed.   

I am waiting for good weather to do more extensive flight testing.  The snow is gone but so far it has been too windy or raining or just too cold.  I expect it to break any time now.  I will do an update with flight results and video if possible when weather permits.

I expect good things...

Update 10-7-15:

I have flown the EDF version several times over the summer flying season.  It flies well and responds to the controls well.  The EDF version is more stable because of less torque effect than with the prop version (short wing span).  

I added another $1 in quarters to the nose to move the CG forward.  The throttle needs to be kept fairly high for basic aerobatics.  It glides into a nice gentle landing under about 1/4 throttle.  The EDF does tend to collect grass clippings.

I also added a quick spray can paint job and some black duct tape stripes.  Here are the results: 

And, oh yea, the EDF sound is really cool at the flying field!

(end of update)

Good luck with building.  

If you build this or any of my other designs please drop me a note in the comments here or by e-mail with pictures at:  dhark69@gmail.com. 

Spring is here!  Let's FLY!

Dan

Update:

Here are three pictures of a build by WoodyIn MD with minor modificatoions:

Woody changerd the fins to "A" configuration, did not cut and reverse the elevons, had to put his 40 A ESC on the outside and, oh yea, he added the "Boogle Eyes" (Nice touch Woodie!).

Nice paint job.  It looks like some kind of venemous geometric insect!

I hope it flies like one.

Nice build Woodie.  Good luck with your up-coming maiden!