Hello out there. It has been a while....
This is a new article related to one I published earlier this year ("One Sheet and Two Sheet No Waste Flying Wings"). the pervious article detailed a series of flying wing designs all based on using one sheet or two sheets of Dollar Tree foam to produce a flying wing with no waste left over. This article is in the same spirit but using four sheets instead of one or two.
First I should report that I have flown several of the earlier designs successfully. They all fly well if properly balanced and powered. As expected, the more tapered designs fly faster with higher performance. I will update the earlier article or publish separate flight videos when available. Unfortunately I am better at designing and building than at video production, but I am working on it.
The basis of this design is to first make two larger sheets by joining two pairs of standard 20" X 30" Dollar Tree foam board along the 30" sides to make two sheets 30" X 40" each. One larger sheet was used to develope a design for one half of the airplane. The second side was then made as a mirror image of the first to make the 80" wing span. The resulting design has a span of 80" and weighs 1365 g. (3 lb) with landing gear and two 2700 batteries. Appearance is very similar to my previous designs but not an exact scale-up due to the different sheet proportions. Sitting on my kitchen table it looks like this:
Updated photo 12-13-14:
This is the one that was white on my kitchen table. It has about 20-25 flights on it. The orange and yellow paint is oil based spray. The bottom is all orange with black spray trim. The stripes are black duct tape.
(end of update)
Here is my foamie storage rack with three "80s" in various stages of completion. The upper most one is the one that was on the table. It is ready to fly:
I will feature the rack in another article. I placed mine in a little used window alcove but it would fit nicely in any free corner as well. It has 36 positions and could hold that many models if they were all small. I currently have 22 models and 6 free positions including two on the floor.
This is how I built it:
Take four sheets of Dollar Tree foam. Join them in pairs along the 30" side to make two sheets 30" X 40" each. Use the standard tape and hot glue method described in many of the FliteTest builds. If you are making a template make a third double sheet.
After gluing and squeegeeing I use a pie lifter heated with a heat gun to "iron" the glue. This makes for much smoother joints:
Measure the dimensions from the drawing below onto the edges of one sheet and connect the marks to complete the longer lines on the plan below (solid lines only). Lay out the 2 3/8", 7 1/2", 9", 9 1/2" and 11 1/2"dimensions and then draw in the interior lines. Lay out the CG marks.
Note: "C" is for cut and "S" is for score. Broken lines are for reference (and do not need to be drawn in).
UPDATE ( 10-18-15):
I have replaced the photo of a full sized plan shown in the original article with a more accurate pencil drawing in pdf format. You can click on the two sheets below to print a copy of my original drawings:
The two drawing sheets should be assembled on the match line by trimming the two corners marked "Remove" and then matching up the corner lines. Scotch tape the joint front and back to make the full drawing. That produces a plan that is equivalent to two sheets of FTFB joined on their 30" sides. You then have to transfer the drawing to the joined DTFB sheets using the measurements shown.
(End of update)
Note: If you are making a template for possible second build (suggested) put all dimensions and the "S (score) and "C" (cut) marks on it. I would also recommend making a separate tail template so you can trace the wing cut-out.
Lay the second sheet against the first and transfer the marks to produce a mirror image. (You will be doing this twice if you are keeping a pattern). Rotate both pieces 90 degrees in opposite directions repeatedly to trànsfer all marks for a mirror image. There are only a couple of marks on top and bottom edges so you can just measure these if you prefer (I did). Connect the marks on the second sheet to complete the plan for the second half. The 3 interior lines will have to be measured from the edges and drawn in. I used a 12" plastic triangle to square interior lines from the edges
Cut or score on all lines indicated. You will end up with pieces as shown below:
First sheet above, second below:
Take the two lower wing pieces and flat join them by the standard method as shown below:
Above are the pairs lower wing panesl ready to join. Note that the 90 degree corners are all down on the page. That is hard to pick up from the picture due to the camera angle. Note that the sharp point of the larger piece should meet the corner of the smaller one. The other end may mis-match by 1/4" to 1/2". Below are the two completed lower wing panels.
Note: The positions of the lower wing panels are shown in broken lines on the upper wing panels on the plans.
Take the upper and lower wing halves and join them at the leading edges. This is similar to the method shown on many FT designs.
First lay the pieces together outside side up (no score lines this side) and tape the joint.
Align the corners very carefully. Then tape and trim:
Fold the wing at the taped joint and trim the 45 degree bevels at the leading edges of top and bottom sides:
Make a small cut to control the end of the bevel on the top panel. The outer wind leading edge is not beveled:
Take a pen tip or similar object that has a well rounded end and depress the edges of the scored lines pretty deeply. Use 3 or 4 firm passes. The foam should be compressed almost to the opposite side. Pay special attention to the butt joints which will be harder than the rest of the sheet. Just use more force there. You may have to relieve them with a knife first.
Checking the spars for uniformity:
Stack the 4 spars together and make sure they are all the same height at both ends. If they are not all the same trim until they are. I had to take a thin shaving off of the narrow end on one piece in this set:
Just after trimming. I taped the spar down to a straight line on the board to keep control and then used the long straight edge to trim. It was only about 1/16" wider at one end but uniformity matters:
Glue the spar pieces just inside of the depressed areas of the two wing bending score lines. They both go on the center section of the top wing. It is easy to spread the glue if you lay the spar flat with one edge in place, hold it down and spread glue along the joint. Then just roll it up into place and onto the glue. Make fine adjustments before it sets.
The long points of the thicker ends should go down and they should not extend beyond the wing sheet. They do not have to connect at the center of the wing. The two spars in combination with the two wing surfaces will end up making a boxed beam spar that stiffens the wing, and uniformly controls the shape of the airfoil when everything is glued. The joint between the two top and bottom wing surfaces make the strength at the wing joint.
Put an extra pass on each side of each spar for extra strength. Be careful not to get any glue into the prepared fold joints at this stage:
The completed spar installation:
Prestressing the folds:
Fold the wing at the leading edge and scored lines to pre-stress the folds and make them easier to bend when gluing. Continue to fold the wing together into the final shape. Unfold back to a mostly flat condition.
Spread glue quickly along the two scored lines (only) and quickly re-fold the wing back to the final shape. Hold pressure along the spars as though they were glued too. Hold for a couple of minutes to allow the glue to set to pre-form the bends at the scored lines. Make sure the spars are in contact with both wing surfaces.
Note: This step is critical to getting good glue joints on the spars. (Same picture above)
Open the wing again and quickly spread continuous beads of glue first along the leading edge and then both spars. Quickly close again and hold the bottom wing surface on flat surface. Keeping pressures against the spars till the glue dries. Everything is glued except the trailing edge. (Same picture as above)
Spread a generous bead along the trailing edge of the lower wing using the glue tip to spread the gap slightly so the glue ends up between the top and bottom surfaces. If the joint is tight put a couple of scraps in to hold it open as you spread the glue. Like so:
Place the wing on a flat surface again and hold till the trailing edge glue is set. Then spread another bead along the outside of the trailing edge joint spreading it with the glue gun tip to make a uniform light convex bead.
The boxed spar is created in the process. The spars should be in contact and firmly glued on both top and bottom wing surfaces for their full lengths:
Setting the trailing edge extension:
The trailing edge at the center of the wing is part of the upper surface so it would extend back and below the bottom of the wing if nothing is done. We are going to use the score cut shown on the plans to bend it up to allign with the wing bottom.
First open the joint and spread a moderate bead of glue:
Then use a straight edge to hold it in allignment with the bottom of the wing:
Squeegee as soon as you have it at the right angle.
Iron the joint if needed and reinforce with packing tape. The purpose for this is to allign the trailing edge with the lower wing surface between the ailerons so that there is not a pitch down effect. It helps to neutralize the attitude of the wing in flight and reduces tip stall (by reducing center wing lift).
The completed wing. Everyting should lay flat on the table except the aileron which will flex:
Repeat the above procedure for construction of the second wing (opposite hand of course).
You may have a small amount of trimming to do on the joining edges of the wing bottom surfaces to make them exactly even with the top surface at the trailing edge. This should be done carefully with a straight edge and very sharp knife since you will most likely be shaving a very thin peice to nothing as you go forward:
Next it is time to join the wing halves:
Above is a trial fit. With the wings laid flat the bottom surfaces should make contact for their full lengths. The top surfaces should meet at front and back and be gapped about 1/8" at the thickest point. Put 2 or 3 short pieces of Scotch tape on the bottom and then try closing the top. Everything should be tight with one tip rasised about 4" or 5 " from the table. That is the dihedral angle produced in the process of forming the wing's top surfaces. If all looks good put a full layer of packaging tape on the lower joint making sure to hold the joint tight. Then bend the wing open about 60 degrees and glue all surfaces. Quickly fold the wing back together and hold pressure till set. Fine tune the fit between the two halves trying to get all surfaces to match evenly before the glue sets (must be done quickly). It will help to place a half-used roll of paper towels under the raised wing so both hands can be free to "work" the joint. Immediately squeegee the excess glue from the top surface to prevent any lumps and bumps. Go over the top joint with an additional light pass of glue and squeegee again to fill any gaps. If you get any mis-match run a sharp knife through the joint and re-align as you reglue.
I always go over the glue with a hot iron before taping. I use a small steel pie lifter and heat it with a heat gun and then iron the joint. The rounded tip helps to remove any small bumps and ridges left from squeegeeing and lets the tape lay flatter. Don't stay too long in one spot or you will start to melt the foam.
Note: This is also good for getting rid of rough edges of glue if you didn't squeegee soon enough. You can also use it to tighten up edges where paper has started to delaminate:
I recommend double tape at the wing joint. If you get any bubbles between layers just pierce with a knife tip or stick pin and press the air out working toward the hole from all sides.
The completed wing:
Next we have to make and install the tails:
Here is one tail blank with the wing cut-out marked (I cheated and used my templare and traced it) :
After cutting the wing gaps out measure half of the width of the bottom part. Score it and fold it back on itself, like so:
Score, glue and fold. Then cut off the little triangle at the back. (Save it for squeegeeing.)
Use scraps to add a 3rd layer to the other side of the "skid":
Then mark and score the 45 degree bend for the top of the wing. I just used a metal ruler that is 1 1/4" wide and alligned it with the corners of the cut-out as shown:
Depress the scored line very deeply on this fold, going over it 4 or 5 times. Otherwise it will be hard to hold the 45 degree bend. Spread a generous bead of glue and hold the 45 degree bend using a triangle or foam scrap cut for the purpose. Use a scrap under the bend to compensate for the skid doubler. Squeegee the excess and allow to cool. Put a second pass of glue and squeegee again while still holding the angle. It should be pretty stiff after that. Make the second one opposite handed.
Here are the two completed tails along with the template. This is the third build using the same template:
Lay out the locations and install the tails.
First measure out 9" from the center of the wing at two spots on each side and draw a reference line. This is the outside side of each tail. Then just slip the tails over the back edges of the wing and allign with the reference marks. Run a bead of glue along the inside side while double checking the allignment. Squeegee it in tight with a scrap of foam. The little skid triangles work great for this since you want to force as much glue into the joint as possible. Check for square with the wing top surface and glue the second side. Make sure the lower front tip alligns with the top fin (viewed from front) and glue it all around the same way Like so:
Layout on the right. Trial fit on left.
Glued and holding.
Checking alignment of the skid with the upper part of the tail. (This was from an earlier build when I added the third member to the skid after installation.) This looks OK, ready to glue.
The tails installed, top above and bottom below:
The skids look splayed here because of the camera angle. They are actually parallel. This shows the third layer on the skids.
Next: Power pods and landing gear:
The next step is to install the three power pods and landing gear. One is used for the power pod and nose gear. The other two are to support the main gear. All three start as standard FS power pods. The center one gets the back triangle ends cut off square since it will be used to "push" the battery into the nose. The other two do not get the motor mounts installed but do get a foam panel to close the angled end. In addition you will need to build and install the fuselage nose section that houses the batteries.
First the end results:
With landing gear and power gear installed:
The pods installed without gear, rear view:
Note: Nose socket, power pods, landing gear, servos and power set -up to follow as updates later this week
The next step is to build and install the nose fuselage and pods:
The nose pod is similar to a FT Power pod but bigger enough that a power pod will slip inside from the back. My power pod plan was printed from one of the plans I downloaded from FT and is slightly big. I have added 1/16" to both height and width so there is a little clearance. You might want to build the power pods and adjust if needed. Here is the plan i used:
Note the small change in the power pod plan. This allows the 45 degree end to be installed without trimming the pod.
First build rthe three pods. They should look like:
Install the motor mount with tape ( I like two layers) and cut the angled end off square on the one that will become the power pod. Trim the rest ot the tabs off that end as well. Install 45 degree ends on the other two. They should look like:
Then make the nose socket. Check the dimensions of your power pod and increase the width and / or height on the socket by 1/16 or so if necessary so it is not too tight. Here is the plan again with the pieces cut out.
Hint: the 45 degree end panel can be left a little long and then cut to fit after assembly.
Guled and holding square:
Installing 45 degree end and holding against table. Spread glue lightl\y in the foam edges and fill the small void at the corner,. Then insert the end and hold against the table for a flat finish. Push down on the end panel till set. Then run a bead in the inside joints:
Trial fit above. Spreading glue below.
Holding against table above. Gluing inside joints below.
Trim the 45 degree end flush the cut about 1/8" out of the center to fit against the wing bottom:
Measure 1 3/16" each way from center line near the nose and about 9" back. Do a trial fit to make sure you can see the marks. Spread glue lightly on the edges of the pod and glue it on the marks holding it 1/4" from the front of the wing at the corners. Take a scrap about 1" X 6" and squeegee the inside corners a least 4" from the back so there are no lumps inside (allows pod to insert). Run a full pass around the outside and squeegee. Do a second light pass and squeegee again to build a slight bevel for strength.
Measure and mark 1" from center line each way near the tail. Insert the power pod with the motor mount aligned with the trailing edge and centered on the marks. Trace the pod tabs onto the wing.
Use a straight edge to extend the marks 1/2" toward the back. Lay out the 3/16 " width and square off the ends. Use the straight edge going inside the nose socket to control and cut the outer marks. Complete the cut-outs and do a trial fit. The pod should insert into the slots with the motor mount about 1/2" behind the trailing edge and then slide forward (allows pod to slip over rear mounting dowels). Finally insert the mounting dowels per the FT method. Extend them as far as you can without poking through the wing top panel (about 2"). I like to poke a small hole in the bottom of the wing at the front end of the skewer hole so the glue can go all the way. Fill the hole till glue comes out then insert the dowel. I like to have a tip on both skewers to get full penetretion. Squeegee the excess glue. Cut off at 1/2" after glue sets.
This model will use a larger motor so we will have to add a second fire wall. It will be 2" X 2" and will be glued to the original one before taping. The excess will be allowed to run over on the top (skewer hole) end so the tape can still be wrapped at the bottom corners, Like so:
Next we install the main gear pods:
These are centered on and cover most of the "skids" and are held 1/4" from the front of the wing. To center them sinply cut 8 pieces of foam scrap 1/2" wide by 1 1/2' or 2" long. These are simply glued to the bottom of the wing on each side of the skids. One pair goes even with the front edge and one about where the rear tabs are on the pod.
Cut 8 spacers:
Glue spacers on each side of skids at tabs:
Hold pod 1/4 " from leading edge:
Use straight edge to control cuts:
Measure 4" amd 10 " from the back and 1" up on both sides of each pod.
Install the pods and pierce through the pods and into the skids half way from each hole on each side side till they meet. Install skewers and trim to 1/4' TO 3/8" on each side.
Next will be landing gear:
This airplane is larger and heavier so a more substantial set of landing gear and attachments is warrented. The wire hanger landing gear featured in one of my earlier articles will not do. We will be using 1/8" mild steel wire and plywood support blocks.
Start with the mounting blocks. The landing gear will attach with skewers and rubber bands but we will use a plywood block to keep the gear from denting itself into the foam. We will also install the skewers in a more secure fashion.
First: Cut three rectangular 1/16" plywood blocks. All three are 2 3/4" long. Two are 2" wide and one is 2 3/8" wide. Like this:
These will glue to the bottoms of the pods but first we have to install the skewers that will hold the rubber bands. These will be similar the FS method with a couple of key differences. One: The skewers will be inserted through the bottom foam board instead of above it. Two: The skewer holes will be completely filled with glue. As we install the skewers glue will be pushing out the other side and will coat that end of the skewer. It will have to be quickly wiped away.
First the layout:
On the center pod measure from the lower 45 degree corner back 7/16" and 2 7/16" and put marks at each side. These will be the skewer locations.
On the two side pods first measure 5 1/2" from the back (where the motor mount usually goes) and put a mark on each side. This is for the front edge of the plywood block. Then measure 3/8" and 2 3/8" from that mark back toward the same end and and put two additional marks each side. These will be the skewer locations.
Pierce the skewers at the marks THROUGH the bottom sheet of foam instead of through the sides above the bottom sheet. Push a sharp skewer through from each side keeping as square as possible about half way till they meet in the middle. Remove the pointer skewer and cut one with square ends 1" longer than the pod width at each location (4 @ 3" and 2 @ 3 3/8"). Fill each hole with hot glue till it is comimg out the other side. Insert the skewers till they are centered collecting the excess glue with a foam scap. clean up the wet end of the skewer by squeegeeing till clean. This will pretty much fill the void around the skewer and glue if to both sides of the paper.
The plywood will be glued right on top of this making everything solid.
Everything is tight and solid.
Here are the completed mounted pods with gear supports ready for gear:
One of the side pods:
This is the inside of the pod showing the skewers going through the foam instead of being exposed inside the pod. This prevents them from moving as the foam is crushed buy the rubber band pressure:
Next the landing gear itself:
I started by finding some scrap 1/8" steel wire that I cut from an old oven rack. It is mild steel instead of music wire and so would not be good for a much heavier model like the old nitro planes I used to fly but easier to bend and strong enough for these lighter foamies.
After cutting and sanding to clean the old baking residue I ended up with 10 pieces 15" long, just right.
Start by making a triangular layout on each of the plywood gear supports. The two rear points are about 1/8" behind the rear skewer and 1/8"from each edge. The front one is about 1/8" in front of the front skewer and centered. The nose gear is wider thatn the mains. This will be a guide for the bending.
My bending tools are home made from an old broken square shank screw driver and a small cheap pry bar. They look like this:
Lay the first wire against the layout and mark the length of the first leg.
Make the first bend using the triangle as a guide for the angle:
Make the second and third bends to establish the base triangle and position of the main wheel strut:
Fine tune the angles till it lays flat and looks uniform. The nose strut should be centered and angled forward 30 degrees. The main struts are the same as this but the short leg of the triangle is shorter and the strut is at 90 degrees. Measure 4" for the nose strut and 3" for each of the main struts and then make two 45 degree bends 1" apart for the wheel offset.
Measure 1/4" more than your wheel radius and make the final 90 degree bend for the axel.
Note: This is a typical bend being made. The crow bar does the holding. It has a hole drilled at 45 degrees right at the tip so the wire can be bent past 90 degrees if needed. The slot in the screw drived does the bending. The bar always has to be past the bend on the free part of the wire or it will get trapped. You sometimes have to start a bend with the screw driver on one side and then move it to the other to finish. It takes some practice...
One finished piece. Checking everything for alignment:
You can use the cutting board to check for square . This needs a slight twist on the triangle base and a little more on the axel. Everything should be parallel to a line on the board unless it is meant to be angled.
The completed set. Checking everything for alignment and the nose gear for 30 degrees. The most important part is that the axel and the short leg of the triangle be parallel. That will assure straight wheels. Everything looks good:
Mounting the gear:
The first rubber band is inserted through the triangle and hooked over one rear skewer. Then it is wrapped around the short leg of the triangle 3 or 4 times and then hooked under the second side of the same skewer, all under tension. That band is then hooked over the front two skewers holding the front of the triangle down.
The second band hooks onto one of the front skewers, wraps around the strut once, hooks under the second front skewer then under each of the two back skewers. This holds the front of the gear firmly in place.
The tension on the second band can be adjusted as needed for wheel alignment.
The nose gear should be angled 30 degrees forward:
The main gear should be at 90 degrees:
The completed gear using a set from my first build with wheels installed:
Note: I will do a separate article on the wheels. They are 3 1/2" diameter. They have 4 layers of foamboard cut with a circle cutting tool and foam pipe insulation cut with a home made foamboard miter box and pop rivet hubs that are drilled out to 9/64".
UPDATE 12-30-14: I found this landing gear attachment method to be too flexible. The gear was fine for take-offs but would buckle on landings. After two or three flights I decided to glue the two pods that hold the main gear to the wing. I also glued a set of 1/8" plywood blocks in place to permanently secure the landing gear to the pods. The first block was cut to fit snugly and glued inside the wire base triangle of each gear set. A second triangle was cut to match the outside dimensions of the wire base and glued over the first. A bead of glue was then run around the outside of each wire triangle to secure it to the plywood. This arrangement has held up to more than 20 subsequent landings. The only remaining issue is lack of stearing. That is a tricky problem with the angled front gear. I am still hinking on that one. So far I just point for the center of the runway then go out and pick it up where it stops.
This is a picture of the gear modification:
I left the skewers in place in case of glue failures. I did have to use it on two sets of gear when the paper delaminated from the pod as a result of hard landings making the gear wobbly again. Rubber bands kept me flying till I could get to the repairs.
(End of update)
Next, Servo Set-Up:
Since the elevons are pretty long I wanted to put the control force near the middle. The servos will be mounted out 12" from the main gear pods.
First measure 12" at two spots from the outside of the pod. Draw a line in the box spar area. Measure 3 1/2" back from the leading edge. This is the outer front corner of the servo positioned putting it within the boxed spar.
Hold the front corner of the servo on the marks and trace it.
Carefully cut them out using a sharp hobby knife.
Go to the center of the wing inside the nose pod and cut a hole in the boxed spar area to retrieve the servo wires. First measure 10 3/4" and 12" from the trailing edge. Then make cuts using a long knife about 1/4" from each side of the inside of the nose pod between the two marks. Then cut across on the two marks to make a rough square cut-out. When done you will be looking into the boxed spar cavity.
Note to self: I should put this cut-out on the plan and then it would be done when the parts arte cut.
Reaching in with the long knife:
The completed cut-out. Fishing the second wire through the cut-out:
Next we have to add 24" of extensions to the servos. I had 12" on hand so I just added two to each. Put a dab of hot glue to hold the joints tight:
Stand the wing on end and feed the wires into the servo hole letting them drop past the center of the wing in the boxed spar cavity. Insert the servo into the prepared hole. Fish the wire out through the cut-out tipping the wing over on it's nose if necessary so you can see the wire as it slides forward. I used a short piece of flag wire to make the "hook" in the picture.
This picture actually shows fishing the second wire. The first one is already taped down with about 1 1/2"piece of packaging tape on it's side of the center line. Repeat the process for the second wire after securing the first. Put an extra piece of tape over both.
After both wires are taped you can adjust the servos and glue them in. They should be inserted till they are flush with the wing at the bottoms and out just enough on the gear ends so you can use a screw driver on the servo arm screw. Put generous tabs of glue on the 3 projecting sides to secure.
This position will minimize drag.
Energize the servos and mount the servo arms.
First drill out the holes to 1/16" to accept the flag wire push rods. If the end hole is too close to the end skip it and go to the second. If they are all close just do every other one, You should have at least two, three is better.
Next mount the arms with the screws provided. If they will not go in at 90 degrees and have to be angled forward or backward favor the one that is the least angle. If they are about equal favor the front.
Next the elevon control horns:
The control horns I use are based on a design I featured in my related article below "Control Horns From Gift Cards". The original concept was to cut gift cards into sections and use the pieces to make control horns. I ran out of gift cards so I now use the same pattern to make them from flexible cutting board material. Start by cutting 1 1/4" strips with a knife and straight edge. Then cut off 1 3/4" sections using a good pair of scissors and a pattern. Then simply cut then on the diagonal by eye with the scissors. You end up with a bunch of right triangles 1 1/4" X 1 3/4". You then nip the corners as shown in the drawing using a pattern. Then drill 3 evenly spaced holes as shown, again using a pattern. If you do not have a pattern the first one you make will be the pattern. You should mark it with Magic Marker and keep it for future use.
On the first two builds I used these doubled. For this build I am upgrading to tripple.
Here are three of the triangular pieces with one laid out to be the pattern:
Above is the trimmed and completed horn. The three pieces were first cut to shape then glued together and then drilled to make a pattern. I made a second one and used this one as a drilling pattern. It does not matter exactly where the holes are only that they are the same side to side (wing to wing on the same build).
Next, installing the elevon horns:
Start by measuring from the tip of the servo arm to the side of the main gear pod. Measure and mark the same distance from the side of the pod at the rear. Then take a straight edge and project this line onto the elevon. Using the straight edge make a score cut from the hinge line to 1/4" from the trailing edge of the elevon. Take a skewer and open a slot on the score line, removing all foam down to the paper for the full length of the cut.
Then make a trial fit. The control horn should fit all the way down to the bottom paper and the holes should line up with the hinge joint:
Remove the horn, fill the slot with glue, reinsert the horn and squeegee any excess. Make sure it is against the paper (check with finger pressure) and that the holes are in line with the hinge line before the glue sets. Also make sure it is 90 degrees to the elevon. Then run a bead all around and fill any void left in the slot.
Next we will make and install the push rods:
For this step you should have the servos powered.
The push rods are made from one piece of flag wire. First take the flag off and cut the wire in half. Then make a tight "Z" bend on the end of each wire. Insert one wire into one of the servo horns and let it run back to the elevon horn. Measure 2" forward from the hinge line and mark the wire. Use this point to start the "V" bend. The "V" bend should be made with the thickest part of a large needle nose pliers. Clamp the needle nose on just past the mark and bend away from the wing about 45 degrees. With the same grip bend the wire back the other direction at 90 degreed. Move the pliers past and up against the second bend, then bend the wire back in the original direction. You should end up with a straight wire with a 3/4" x 3/4" "V" in the middle of it. The "V" should point away from the wing.
Take the wire off the servo and use it to make another. The only difference is that the fist "Z" bend should be in the opposite direction. Like so"
Both "V"s are pointing down and both "Z"s are pointing out.
Insert both wires into the servos with the "V" bend pointed away from the wing. Set the elevon to the initial setting (3/8") positive by placing a foam scrap in the gap as shown in the picture:
While holding this adjustment hold the push rod against the elevon horn and mark the hole position. Bent the rod a sharp 90 toward the center line then complete a modified "Z" bend with the end pointng away from the wing. Cut off the excess. Grip the rod by the "V" and twist it till you can insert the end of the modified "Z" into the top hole on the horn. Push it in and allow it to rotate and snap into position. Repeat on the other side. If done properly you should have two elevons in the 3/8" positive position with two snug push rods.
Check the gap after removing the foam scrap. It should still be 3/16" on both sides.
Later you can make small adjustments by opening or closing ther "V". This usually requires adjusting all 3 bends.
Finally on to the power gear:
Here is the complete power set-up:
My Power Gear:
Air 3010B 1300Kv (Hobbby King) (over 1600 g potential)
8 X 3.8 Prop (will test 9" and 10")
Red Brick 50A ESC (HobbyKing)
Two 2700 mAh 25C Zippy Compact batteries (with parallel connector cable, home made)
Two Turginy TSS-11MGA Servos (Hobby King)
Fly Sky FS-T6 radio:Elevons, 50% throws and 50% exponential
Note: This power set-up tests at 1375 g with full batteries.
The model weighs 1425 g ready to fly.
The batteries just stack and push clear to the front of the nose pod, totally enclosed. The total available draw is 135 A and I am using 26 to 30 so they should stay cool. If they heat up I will have to work on some sort of ventilation and possibly a bigger pod to do it.
I will test other props to get thrust over 1425 for unlimited vertical.
Thrust is parallel to wing bottom. I want to play with small up thrust to compensate for high power.
I am planning additional articles on:
Foam wheels with pipe insulatoin treads.