Half Sheet No Waste Three Channel Trainer

Hello Everyone,

This is the second build article related to my article tytled "Half Sheet No Waste Series Preview".  I showed three variations in the first picture in the article.  This is the one in the upper right.  I chose it because I have not done a build article for a 3 channel trainer before.  Nor have I done a long wing version in either size (half or one sheet). Although many of the details are the same from one of my designs to the other there are some details that change and are critical to the performance of the aircraft.  Because of that and the fact that some have not seen any of my articles before I will go through step by step from start to finish.  If you follow this article from beginning to end you should have a flyable airplane at the end.

Here is a picture showing the three variations again:

The "Long Wing Trainer" is on the upper right.

This is a picture showing a top view of the prototype (left) and a bottom view of the this (second) build (right):

The prototype has one short flight and was doing well till the set screws on the motor mount vibrated out.  I am waiting for replacements.

The Plans: 

The plans for this build are a simple pencil sketch from which you can take the dimensions and do a layout directly on the foamboard sheet.  For these designs which use all straight lines most of which go from edge to edge of the sheet that is actually easier than transferring a drawing.

Here is the drawing:

This is a scanned file that you can print. 

First left click somewhere on the drawing to select the immage.  Then right click on the immage and select "Print".

So let's get started.

The first step is to take a sheet of Dollar Tree foamboard and cut it in half.  These sheets are theoretically 20" X 30" but they vary by about 1/8".  My current box measures 29 7/8" X 20 1/8".  So to cut a sheet in half you should take half of the actual measurement instead of just measuring 15".  Assuming that we have done that or as in my case we have a half sheet left over from the last 1/2 sheet build, we start with a half sheet. 

Layout:

Measure along one of the 20" sides and mark 4 1/2" and 11".

Then step over and mark 4 1/2" from the second mark, or if you are using a long ruler mark 15 1/2".

That will leave 4 1/2" +/-  to the end of the sheet.

Go to the same corner of the other side of the sheet and this time mark; 6 1/2", 11" and 15 1/2".  Again, you should have 4 1/2" +/- left.  

Rough Cutting:

Take a long straight edge (at least 16") and cut across each pair of marks.  You should end up with two pieces tapered from 6 1/2" to 4 1/2", a piece 4 1/2" and a piece 4 1/2" +/-, all measuring 15" +/- long.

Take the piece measuring 4 1/2 +/- and find and mark the center of one 15" +/- side.   From the same side measure  and mark 1" along each of the 4 1/2" +/- sides.  Take a straight edge and cut from the center mark to the 1" mark on each side.  This is the rough cut for the tail.  

Take the actual 4 1/2" piece and measure 2" from one end along each of the 15" +/- sides.  Use a straight edge to cut off the 2" X 4 1/2 " piece, leaving a piece 4 1/2" X 13" +/-.  The larger piece is for the fuselage (pod), the smaller one is the blank for the motor mount support. 

If you arrange all the pieces in their orignial positions it should look like this:

Note: Your triangular pieces should look narrower.  I mistakenly cut these at 1 1/2" and had to remake them.  I also revised the length of the 2" by 4 1/2" piece from 3" long earlier so that will look a little diffrerent as well.

Wing Fabrication:

Take the two wing panels and stack them.  They should be identical.  If not, put the smaller one on top and trace it onto the larger one.  Take a long straight edge and cut off the excess.

Take one of the two wing panels and lay out the wing camber folds.  On the wider end measure two increments of 1 3/8" from the angled side.  

On the narrow end measure two increments of 7/8", again from the angled side.    

Butt the two thick ends together and transfer the marks carefully from one to the other.

Do the same with the narrow ends.

Take a long straight edge and make score cuts between the pairs of marks on each wing panel.  Like so:

 Note: This sheet does not look tapered because of camera angle.  The wider end is away from us.

Take a rounded object like the pen tip shown and crease the foam deeply along each score cut.  Make 3 or 4 passes so the foam is comperssed clear down to the paper on the other side without damaging the paper.  Like so:

Then take each wing panel and over-flex it so that the creases will fold easier when the glue is applied.  Like this:

Hold each one for a minute or so.

Next you will need to fabricate two blocks to set the wing camber.  They are made as stacks of scraps of foamboard of the correct thickness.  For this build we will need one with two layers 3/4" X 1 1/2" and one with three layers 1 1/4" X 1 1/2".  Just cut the pieces to size and either hot glue them or use a wrap of Scotch tape to keep them in a stable stack.  I used tape:  

Then take one of the wing panels and place it on the building board with the scored side down.  Place the larger block under the center panel of the wing at the wider end and the smaller one at the narrower end.  The leading and trailing edges should push down to the board easily.

After a trial fit place a moderate bead of glue in the second scored line and place the wing panel over the blocks again.  Hold pressure on the trailing edge and the two blocks for a minute or so till the glue sets.  

Remove the panel and place glue in the first scored line and place it back over the blocks.   Push the leading and trailing edges down to the board.  Like so:  

Hold pressure on the leading and trailing edges making sure both are in contact all along for about one minute till the glue sets.  When you release pressure both edges should stay down and the centers should be in contact with the bocks.

Note:  Doing the folds one at a time helps keep the middle section at the right angle.  It tends to roll forward if you do both at the same time,

Do the same to the other wing panel.

Wing assembly: 

Place the two wing panels with the two root ends butted together and a 2" support under each wing tip.  I used a couple of rolls of Xmas wrap ('Twas the season).   You could use a couple of thick books, wing tip gages like are provided in many ot the FT plans or anything else that is 2" thick. Like so:

Update 9-30-15:  My original instructions used 1 1/2" under each wing tip for the dihedral setting but I found that to be inadequate.  I modified the prototype to a polyhedral with 2 1/4"at the tips and it flies better.  I am now instructing to use 2" under each tip which will have the same effect.  

Note that the centers of the wing are touching but the leading and trailing edges are not.  

They are gapped about 1/8" at front and back.  That means we have to take half of that off each wing at the center.   

Measuring for the 1/16" trim. (Note: It will be a little more, 3/32 or so, with the 2" dihedral)

Update 9-30-15:  

Trimming with a straight edge.

Woops! a little too much.  

I had to sand a little off the front and back edges to close the gap.

There,  Just right.  

OK.  That's better.  Ready for glue.

Spread a moderate bead of glue on the edge of the foam on one side of the joint and butt them back together. Press down on any high points to get both sides to line up as closely as possible.  Immediately squeegee with a scrap of foam board 

Set up for gluing with wax paper under the joint:

"Ironing" the joint using a pie lifter heated with a heat gun after gluing helps to produce smoother joints. 

Do this top and bottom to smooth out any lumps and bumps.  One side has a sharp edge that can be used to scrape up the bigger hardened lumps.

Appy tape to top and bottom surfaces to reinforce the joint. 

This was put on in two pieces breaking at the second bend to avoid wrinkles.  Lap at lease 1/2".  Let the tape lap over the front and back and then wrap over the edges. 

Split the laps so they do not wrinkle on the other side.

Press firmly as you wrap over for a tight fit. 

Do the same procedure top and bottom.  It is best to do the bottom first so the top finishes without any surface laps visable.

Tail Fabrication:

Next we will fabricate the tail section.  This is made from the last piece cut from the original sheet.  It measured 4 1/2"+/- X 15" +/-.  Earlier we cut the two triangular pieces from one 15" edge.

First measure 3 1/2" in from each end on the straight edge and near the angled edges.  Use the cutting board grid or a tri-square to verify that the marks are square to the straight side.  Score cut the two resulting lines.  Then measure 1/2" from the corner of the straight side along each end and make two marks.  Cut from the score line to the 1/2" mark on each end.  This makes the back taper on the rudders.  It should look like:

The ends should measure 3".  Next measure and mark 1 1/2" to the center of each end.  Place a long ruler on the two marks and draw a light line across.  Then along that line mark 3/4" toward the center and 1/2" toward the tips on each side of each score cut.  

Flip the piece around and make the same two marks on the trailing edge at each score cut.

Use the marks to make 4 cuts all trhe way through.  Make a second cut all the way through at 1/8"or less from the first cut on the side away from the score line.  You should end up with 8 cuts that look like this":

Next make the score cuts for the rudder hinges.  They go from the outer most paired cuts to the center marks on the tips.  Like so:

 (Both ends)

Then flip the piece over.  The elevator hinge cut will be on the other side.  Measure 1 1/2" on each tip again and use a straight edge set on the marks to score cut between the two inner sets of double cuts.  It should look like this:

(Straight edge removed for clarity)

Next we need to make the bevel cuts.  The first two score cuts separating the horizontal stabilizer from the two vertical stabilizers will get double 45 degree cuts.  The leading edges of the elevator and rudders will get single 45 degree cuts.  Like this:

After making all bevel cuts the piece will look like this:

Top.

Bottom.

Next we are ready to fold and glue the joints between the horiz.and vert. stabilizers.  First do a trial fold to verify that they will go to 90 degrees.  

I had to do a little sanding on mine to get rid of a couple or humps.   

After sanding and verifying the 90 degree fit, spread a small bead of glue right in the center of the joint and then a moderate to generous bead on one side of the foam.  Fold it up and hold at 90 degrees using a tri-square or a square cut scrap of foam to hold square.  Immediately squeegee any excess adhesive from the joint.  Hold for about a minute till the glue sets.  Do the same on the other side.

Spread a small bead of glue in the joints of the rudders and elevator.  Use a scrap of foam or the tp of the gun to remove all excess.  If you are using the gun you have to be careful not to melt too much foam.  The goal is to have the tip rub the paper and slightly melt the foam on each side while pushing the glue into the foam.  If you have not done this before try practicing on a scrap.  If in doubt the foamboard scrap method is safer.  The goal is to get the glue thin enough so that the joint moves freely.  

The finished tail section:

Tail Boom Installation:

This step will start to define the shape of ther aircraft.  

First take two skewers and trim them to the same length removing the pionted ends.  

Note: You need to get the heavier skewers that are available.  The ones I am using come from Wal-Mart 100 to a pack for $2 or $3.  I tried to look them up but they are listed as "store information".  They should measure 1/8" diameter and about 11 5/8" long.  After trimming the point off they should be 11" long.  If in doubt you can use 1/8" dowel but I think the boaboo is stronger.

There will be some in the pack that seem really round and hard.  Some will seem splintery, like the bark is separating.  Let Mom use the splitty ones for shish-ka-bobs.  Pick the firm round ones for this.   

Some skewers in a pack will be fairly straight but most will be bowed slightly. Lay the skewers on the work table.  They will naturally settle with the straightest side down. You should be able to tell which side is bowed in.  You want to find and mark that side with a dot on one end. When you lay them on the table the mark should be on the side, not top or bottom, but right on the side.  If you hold them with the dot up and hold them down in the middle both ends should be off the table and you should be able to line them up with a straight line.  Some are just too twisty to use,       

Next take the tail section and stand it with the rudders down.  Mark on the bottom surface 3" from the leading edge along the glued joint on both sides.  This is the back end of the tail boom (skewer).

Now stand it up on end with one rudder on the table.   Align one skewer with the 3" mark and the dot up.  You want all the curvature to go toward the enter of the aircraft.   Hold the skewer in place with your thumb while spreading  a bead of glue about 1" long on one end.  

Let it set till firm then remove your thumb and complete the bead to the end.  Use a pen or something similar to hold the skewer in place till the glue is set,  Then run a bead of glue on the other side.  After both sides are set I like to put a second light pass on the first side and use the gun tip to smooth it out. A little extra weight is worth it here for the extra strength.  

Use the hot tip to melt and spread any ridges or lumps that you get ( like just above the tip in this photo).

Stand it on the other rudder and do the same thing o ther other side.

If properly done you should ba able to sight across the two skewers and they should be parallel.  Like so:

Next measure from the leading edge of the tail 4 1/2" and put a mark on each skewer.  This will be the trailing edge of the wing.

Next we have to prepare the wing to receive the tail booms.   

The skewer is not long enough to reach the front of the wing.  It will be glued to a rib we will add to the wing.  The rib will also serve to triffen the wing.

We will use the two triangular scraps from the leading edge of the tail to make the ribs.   

First we have to do the layout.  Measure across the tail from outside to outside of the two skewers.  The theoretical number is 8" but the folds tend to add a little.  Mine measures 8 1/16.  We have to measure half of that number or 4 1/32 each way from center at the front and back of the bottom side of the wing.

Top:

And bottom:

Hold 4 1/32 at center.  Mark "0" and 8 1/16". 

Next we have to make the ribs.  Take one of the triangle pieces and hold it on one pair of marks.  Mark the leading and trailing edges and the positions of the two wing folds.  Like so:

Take a foam scrap about 1" wide and use it as a gage to mark the depth of the wing at the center.

Use the gage to mark the depth on the triangle at the two wing fold marks.

Mark square up from the wing fold marks.  Draw lines across the top and then connect to the laeding and trailing edge marks.  Like this:

Cut the piece out and check the fit.  Make any small adjustments needed so it fits flush to the bottom of the wing and tight to the under side of the wing surface.  MIf something does not fit make a replacement from scrap if necessary.  Once you have a good fit on the first side try it in the second.  If the wings are uniform it should fit both places.  If so, trace it to the second triangle and cut the second rib.  Glue both in holding the marks on the wing on the wingtip side of the rib.  Spread a small bead of glue on thehe edge of the rib and position it.  Then run a nice filling bead on both sides.  Keep it fairly small  but use enough to fill in any small gaps between the rib and wing.

Next take the tail section and line the marks on the booms up with the trailing edges on each side and mark the position of the fronts of the booms on the bottom edges of the ribs.

On one side spread a moderate to genrerous bead of glue on the bottom of the rib from the mark to the trailing edge of the wing.  Set the skewer into the glue with the mark on the skewer at the trailing edge.  The other skewer should be touching the wing near the other rib but do not wory about alignment of the second side at this time.  Immediately use a wet finger to smooth the glue on each side of the skewer.  Keep the dowel in the center of the rib and hold till set.  

The second side will be off by however much the skewers were bowed.  Spread glue on the second side and align that skewer with the rib the same way.  You are straightening both skewers in the process.  If everything is straight the two skewers should be parallel as you sight scross and the tail shuld be parallel with the wing viewed from center front.

This looks good (sorry a little out of focus)

If the tail is straight the skewers will be parallel and vice versa.  If not, not.

The tail a boom installation is complete.  We are ready to fabricate and install the fuselage (pod).

Fuselage (pod) fabrication and installation: 

The fuselage is made from the 4 1/2" X 13" +/- piece that was cut at the beginning.  First measure and mark  1 1/4"  and 3 1/4" on both 4 1/2" ends.  Then measure 3/16" toward the center from each of those marks.  Score cut the resulting 4 lines. Remove the 3/16" strips.  It should look like this:

Do a FS style "B" fold ("the sides go beside the bottom plate").  I like to put a light bead of glue on both foam edges so the paper is glued the foam at the corner.  Then run a small bead inside the corners and squeegee that tight.  You will end up with shape similar to an FT power pod without the tabs and angles.       

Next we have to lay out the cuts that will fit the pod to the bottom of the wing.  

Start by marking 1" each side of the center of the wing at the leading edge and trailing edge on the bottom of the wing.

Next hold the pod open side up against the marks with one end at the bottom point of the trailing edge.  Mark the bottom point of the leading edge and the positions of both wing folds on both sides of the pod. Measure from the back to each leading edge mark.  They should be the same.  Adjust to the average if needed.

Try to be as precise as possible through this whole process so both sides match.

Then take a scrap of foam about 1" wide and use it as a gage for the depth at the center of the wing.  Like so:

This will be the depth of the cuts at the leading and trailing edges. First use a tri-square to mark a light square line across the pod at the leading edge marks on both sides Use the gage stick to mark the depth at the leading and trailing edges on both sides.  Make sure you use the same mark from the stick on all 4 for uniformity.  Then draw a line connecting each depth mark to the closest wing fold position mark at all 4 locations.

Complete the layout by measuring up from the leading edge line in two places and drawing a second line corresponding to the top wing surface.  The end of the slot should be square to match the edge of the sheet at the leading edge.  Cut all the way through on all the marks shown.

Hint: It is easier to make the short end cuts with a hobby knife first.  Then start the longer cuts from that point out.  Make sure to use a straight edge for the longer cuts.

I neglected to take a picture of the cuts separately but if you slip the slots over the leading edge it should look like this:

Make small trim cuts if needed (i had to on this one) to get a good fit on both sides.  

When you are satisfied with the fit adjust it to the 4 marks on the wing and run a bead of glue along all the joints you can reach with the gun.  You do not have to remove it, glue the edges and reinstall since the connecting points are so long.  That is a lot of glue surface.  Use the gun tip to form a nice even fillet.

You can take a skewer and put about a 1" heavy bead of glue on one side at one end and reach inside to spread it on the joints if you want but there is a lot of surface on the outside.  I do not think inside glue is necessary.  

Guled up.

Looks the same on the other side.

Measure up 3/4" from the bottom corner and back 1 1/4" along the top edge of the nose on both sides:

 Cut off both corners to look like this.

Note:  Your nose will look a little longer than the one shown in these pictures.  I actually cut the pod piece to 12" and 3" as I did in the prototype.  This plan calls for 13" and 2".  Therefore your nose will be 1" longer.   There are four advantages:  1. You can use a smaller battery for lower overall weight.  2. You have more room for adjusting any battery for balance.  3. If the battery is back from the nose you can put a piece of foam (like carpet backing) in the nose to protect batteries in case of hard landings.  4. There is more room for wires.  So your plane should turn out a little better than mine.      

Next we are going to make the nose closure.  It is made from a scrap that is carefully cut to 2" X 3 1/2".  Measure in 3/16 from both long sides and one short side and make score cuts. Remove the foam.  The layout should look like this:

 Fit the piece into the nose with the short end slot down.  The paper should lay over the foam ends nicely.  Mark the points of the first angle on both sides.  Transfer the marks to the back side and score cut the back.  Open the cut and make back cuts a little less than 45 degrees on both sides of the cut.  Here I am making the second back cut. 

Insall it again and check the fit as it folds over the first angle.  Everything should firt tight with the paper covering the edges of the foam.  If all looks good do the same with the second angle.  Here I am scoring the second cut.

And folding it open ready to cut the bevels. The second cut needs only about 15 degrees on the back cuts since it only folds to about 30 degrees.  

This picture is  a little fuzzy but here I am marking 3/4" back from the center of the second angle marks for the end cut.  The edges are all slotted and the two folds are scored and beveled.  All that is left is to cut it to the final length. The nose only goes 3/4" past the second angle, leaving access for installing the battery.  

 It will cut at the 2" mark.  I used the board grid to square the cut,  This end stays square (no bevel).  

Do a trial fit.  All the edges of the foam in the nose area should be covered and the nose folds should match the angle cuts.  Everything should be neat an snug. 

Here is the finished piece with glue spread in the two folds ready to reinstall.

 Do not put glue on the edges yet.  This is just to set the angles.  Put it in place and let the angle glue set. Then remove it and fill in the glue at the angles if there is any gap.  Install it again till that glue sets.  Mark the back edges where the paper lays over the foam.

 Then remove it and spread a light bead of glue on all the foam edges up to the marks on each side.  Quickly reinstall the nose piece and press it into place using a scrap of foamboard.  You just want to push the paper into the glue and flatten it to the foam, not push the foamboard in and dent it or depres it so you see the line.

Use the scrap to push it down all the way along.  

Next go inside the nose and reinforce all the joints with a heavy bead of glue.  You can get a little sloppy here where it does not show.  I cut a piece out of foamboarb with an angle so I couldreach the top joints.  I put  bead of glue on the edge and reached in spreading it along the joints.

After everything is glued erase the pencil marks.

Next we are going to wrap the nose and exposed pod edges with packing tape.  These areas get a lot of handling with removing and reinstalling the battery.  Also, the nose will get an occasional bump in a less than perfect landing so tape reinforcement is advisable.  It also secures any loose edges from the nose construction.  One layer is OK on the exposed edges of the top of the pod sides but I like two on the nose.

Cut two pieces of tape just a little shorter than the distance from the leading edge of the nose to the back edge or the nose piece.  Stick it to the top edge of the side with the same amount hanging over each side.  Wrap it down over the outside first working from the center out and keeping it wrinkle free.  Then wrap tightly over the top and down on the inside working from the middle out.  It is more important to keep tight as you wrap over the top than to be absolutely wrinkle free but you should be able to do both.

Do the same to the other side.

Next we will wrap the nose.     

Start by cutting a piece of tape about 6" long.  Align one side with the back edge of the nose closure with the ends running out to the sides.  Like so:

Split both sides with a knife or scissors in line with the nose closure fold and then fold the resulting tabs down tightly over the sides and around the bottom starting with the back and working towards the front. 

Put a second piece aligned with the bottom edge of the nose closure and overlaping the first.  Split the sides again and fold the upper one first then the lower one which will just fold back along each side.

Next use two 5"pieces of tape to wrap all the way from top to bottom around the front of the nose.  Start one piece on the bottom allowing it to cover all of the ends that wrapped over from the top.  Let it wrap around the tip of the nose past the first bend..   Start the second piece with about 1" hanging over the back edge of the nose closure. Wrap forward over the nose and lap onto the bottom.  Align carefully so that the two pieces are parallel to the sides and do not run off at the edges.

Note: I used one 8" piece instead of two 5" pieces but alignment was difficult.  

Use a knife to trim the sides of the 1" overlap at the back edge of the nose closure.  Wrap it over the end and onto the inside of the pod to seal that edge.   

Cut several pieces just long enough to fit inside the bottom of the pod and cover the entire bottom, overlapping at least 1/2" on each piece. This will be the base for the velcro attachments inside the pod. 

Wing Tip Launching Grip:

 Next we will install the wing tip hand launching grip.  It is composed of a piece of 3/16" dowel 1 1/8" long mounted through the wing tip with a cutting board reinforcement on the bottom.  

Start with a 1" strip of cutting board.  Cut off a piece that will fit in the middle section at the wing tip.  

Drill a 13/64" hole through it leaving about 1/4" to the edge.  Glue it right at the edge with a full bed of hot glue.

Use skewer piont to start a hole through the foam from the bottom till you just pierce the top paper.  Then push it through from the top and work it around to complete the hole matching the drilled hole in the reinforcement plate.  

Then cut a piece of 3/16" dowel.  Slightly taper both ends with a sanding block.

Insret the dowel from the top till it just penertrates the reinforcement plate.  Then apply a moderate bead of hot glue all the way around close to the wing surface by twisting the dowel as you spread.  Continue twisting and slowly push down till the same amount sticks out top and bottom.  It the bead was fairly uniform you should be able to form a flatish donut shaped glue bead on the top surface byjost twisting.

Tha looks OK.

Then run a bead of glue arount the dowel on the bottom side to secure it to the reinforcer.

The finshed product.  

Motor Mount:

Finally we will fabricate and install the motor mount.  It is made from the last piece of foam left from the cut-out and a 2" X 1/12" piece of 1/16" or 1/8" plywood.  .  The foamboard is 2" X 4 1/2".

 Take the foamboard and measure 3 inrements if 1 1/2" along one 4 1/2" side.  Square the marks across and score them.  Then do the layout shown below:

Update 1-20-15: I have revised the layout below to produce 4 degrees down thrust.  This amount will help to counteract balooning at high throttle. 

Cut off the excess material as shown:

Cut double bevels on the score lines at a little less than 45 degrees.  Bevel the two 1 1/2" edges to match the sides when folded.  When all cut it should look like this:

Do a trial fit holding it against the cutting board grid or a 2" square drawn on a piece of paper.

The two corners should be spread at 2" and the other end should be centered on the grid.  If all is good pick it up and spread a generous bead in each double bevel.  Quickly place it back on the grid and hold in proper alignment till set.  Pick it up and fill in any gaps in the glue.  Hold it against the grid again to assure proper alignment.   Check both sides of the foam edges.  Trim as necessary to get it to lay flat both ways.    

Layout on the wing:

Make two marks at 1" from center line and 1/2" from the trailing edge of the top of the wing.

Make a center mark on the front edge of the motor mount support.

Then spread glue on the bottom edges (longer side) and set it in place with the two corners on the marks and the center mark at the wing center line.  

Next run a small uniform bead around the 3 sides of the motor mount support and gererous beads in the joints inside the support.  Use a scrap to spread a generous amount of glue at the inside front joint.

Before installing the plywood motor mount cut a hole about 1/2" X 1/2" in the wing near the center ot the mount support to allow the motor wires to pass through later.

Then cut a piece of 1 1/6' or 1/8" plywood 2" X 1 1/2".. Hold it in place against the back of the mount support and trace it.

.  

Cut of the excess.  Spread a moderate bead of glue on the back edges of the mount support and quickly press the plywood mount into place.  Use a wet finger to flatten or a scrap of foam to remove any glue that squeezes out.   Run a generous bead to fill in between the mount and the wing and then an even covering pass that is smoothed by the gun tip.  

The completed mount.

CG Points:

The CG point is at 30 -35% of the MAC (Mean Areodynamic Chord).  Since the trailing edge is straight I will reference it from there.  The measurement is 3 5/8"- 3 3/4" from the trailing edge.  For convenience of field balancing we will use a point 1" outside of the tail boom support.  I use a small dab of hot melt glue which can be found easily by feel.      

Here are several views of the completed airframe:

Running Gear:

This trainer has a simple 3 channel control system, throttle, elevator and rudder.

Here is a picture of the motor installation, along with servos and control rods for the elevator and rudder:

The Park 250, 2200 kv motor mounts centered on the motor mount both directions.  The motor power leads pass through the motor mount and the wing under the motor mount on their way to the ESC inside the fuselage (pod).  You will probably have to add 2" or 3" to the motor wires before installling connectors and inserting them so the connections to the ESC can be made in the receiver access hole.

The 5g servos are mounted at the trailing edge of the wing directly in front of the control horns.  The servo leads transit the top surface of the wing at approximately 45 degrees prior to penetrating the upper wing surface and entering the pod near the receiver position thus avoiding the need for extensions.  Tape them down for control, durability and airflow.

The receiver and ESC are mounted in the pod at the thickest part of the wing.  There is an access port in the bottom of the fuselage at that point for installation and service of the receiver and ESC.

Here is the receiver / ESC access port on this build.  It starts at 3 1/4" from the back of the pod and is 2" long. It is 1" wide centered in the pod. 

Velcro is placed on the sides of the pod inside this opening to attach the receiver and ESC.  Packing tape should be used behind the velcro for durability.

Here is the receiver and ESC installation on the prototype.  The pod on that build did not go to the back of the wing so the motor wires are exposed.  Otherwise the gear installation would be the same.  Note where the servo wires penetrate the wing in this space. 

The 1600mah battery is mounted almost all the way up to the nose in the forward part of the fuselage.  It can be adjusted as needed for balance or a diffferent size can be used (additional nose weight might be needed for a smaller battery).

This is the 12" pod and shows a 1500 2S battery (too heavy).  Yours will be 1" longer and the battery will be 800 2S or 1000 2S  .  Adjust the battery size and location for proper balance.   Once the battery location is set insert some low density foam like carpet padding in any empty space in front of the battery in the nose to provide a cushion for the battery in case of a hard landing. 

The control horns can be made from gift cards or flexible cutting board material as detailed in my related article referenced below.

Here are four pictures of the sequence of making the control horns from cutting board:

First cut a 1" strip of cutting board using a straight edge and hobby knife.  Then cut 1" squares carefully using a pair of scissors and the cutting board (or lay out with ruler and tri-square).  Then carefully cut diagonally from corner to corner with scissors.  Then cut the corners off as shown.  Cut one and then use it as a pattern to cut the rest.  Then stack the blanks together matching the edges that will be drilled and the side that will insert carefully.  Then drill 3 evenly spaced holes as shown.  Drill the outer two first, then carefully align the middle one between. 

Push rods are made from flag wire available at Lowe's or Home Depot.  The fabrication method is detailed in my related article referenced below.

Note the directions of the bends.  The fact that one is a "Z" and the other is a modified "Z" causes them to oppose each other and prevents them from coming loose.  You have to twist a 1/4 turn to get them in and they would have to twist a 1/4 turn to come loose.  Ain't gonna happen.  The "V" bend in the middle gives you a handle for the twisting and lets yo make small length adjustments without having adjustable hardware,   See the related article below for details on making these adjustable push rods. 

The tie rod between the rudders is made from flag wire.  The tabs that anchor it are made from cutting board material.  It looks like this:

The holes for the tabs are made by inserting a skewer point at least 1" at 1/2" from the bottom of each rudder.  The wire is made with two "Z" bends spaced so the vertical parts of the bends hit the center of each rudder when they are set straight.  You can use the vertical stabilizer just below the rudders as a gage.  First make the wire with the bends.  Then make the anchor tabs as showm on the sequence below.  Then insert one tab by filling the hole with hot glue and inserting.  Then insert one end of the wire into the first tab  Then put the second tab on the wire and fill the second hole with glue.  Then insert the second tab making sure it goes in square to both the wire and rudder..  

Note:  It is not possible to install the wire if you glue both tabs in first.

This picture shows the sequence for making the tabs from a 1" strip of cutting board:

The cuts are all made with scissors.  The thicker end is about 3/16" wide.  The narrow end is 1/8" or less.  The hole is 1/16" reamed a little. The corners are nipped for appearance.

Initial setup should be with both ends of the control rods at the outer most holes on both ends.  Start with 50% rate and 50% exponential and adjust to your skill level.  Beginning pilots may want to start at 35% rate and 50% exponential.  If you do not have dual rates and exponential start on the 3rd (inner most) hole at the servo and the outer most at the control surfaces. 

This should complete your model...

 Variations:

 There are several variations that can be built from this plan.

1. Trainer:  The Swept Wing 3 Channel trainer (described above).

2.  Sunday Flier: A Swept Wing 4 Channel.  To make this variant reduce dihedral to 3 degrees by not trimming the wing root before joining wings.  Use 3/4" blocks under wing tips leading and trailing edges. Add the ailerons shown on the plan.  Cut them after joining the wings.  Place all servos directly in front of the corresponding control horn under the wing at the CG.  CG is same. 

3.  Trainer:  A Straight Wing 3 Channel Trainer.  Use wing "A" instead of Wing "B".  Measure CG at 1 3/4' from leading edge anywhere along wing.

4.  Sunday Flier: A Straight Wing 4 Channel. Use wing "A" instead of wing "B ".  Measure CG  at 1 3/4" from leading edge anywhere along.  Follow #2 above.

5. Sport: No dihedral (two options, wing "A" or wing "B").  If you want a more aerobatic model you can eliminate dihedral altogether by trimming the root end of each wing slightly at both the leading and trailing edges and going to nothing at the middle. It will take 1/16" or less so proceed carefully.  The easiest way is to use a sheet of sand paper on your building board and stand the wing on end.  Holding the wing straight up the leading and trailing edges should touch and the middle should be gapped about 1/16".  Drag it across the sand paper 3 or 4 strokes and then check. Repeat with the other wing. Stop when the wing lays flat with no gap.  You can do this with either wing "A" or wing "B".  After wing assembly follow #2 and #3 above.  CG is the same.   

Following the variations notes above you can build 6 different airplanes from this single plan.  Each has significantly different appearance and /or performance charactoristics.  

 Gear: Trainer or Sunday Flier

Motor: M2222 2850kv 55W 17g motor from eBay (or similar 15 to 20 g motor, 55 W to 75 W

ESC: 10 A 

Servos:  5 g

Prop: 6035 SF trimmed to 5" (Adjust to your motor)

Battery: 800 2S or 1000 2S

Update (9-30-15): After flight testing the slower version is pretty fast and sporty for its size,  You may not want or need to go thethe higher power / speed version. 

Alternate Gear:  Fast Sunday Flier or Sport 

     More power, speed & weight - Lower low speed performance

     This set would be more suitable for 4 channel variants  

Motor: Turnigy DonkeyST2204 1550 kv

ESC: 15 A

Servos: 5 g

Prop: 7035 SF

Battery: 1000 3S (or other per your preference - balance)

Well, that is it.  You should be ready to fly.

If you build this and have any questions or see any discrepancies please contact me through the "Comments" section below.  

If you build please send pictures and any other information you like to my e-mail: dhark69@gmail.com

Good luck and happy flying!

Dan