Bought this from Simon H. just before the December meeting. Will see how far I get before my knee surgery on Feb 9.
During my recovery I will be covering the L19 Bird Dog.
span- 34"
length- 28.5
weight- less than 2 pounds
power- TBD but it will be "enough plus 25%". I usually build until I see the weight, size and prop clearance, then start calculating the power to see what would fit.
colours- still to be decided. "Don't make a decision until you have to". The decision will be influenced by the colours on hand.
Frank
Gentlemen...I started my engine.
Triple checked...there are port and starboard fuselage sides. 8)
F.
Quote from: Frank v B on January 31, 2023, 10:53:38 PM
Gentlemen...I started my engine.
Triple checked...there are port and starboard fuselage sides. 8)
F.
@Frank v B you have passed the first of many steps in becoming a Master Builder: 2 different sides!!
Good luck with the other steps. ;)
canopy structure assembled.
F.
Something that looks like a fuselage.
Note: to make sure the two formers are square I taped triangles to the formers (photo 46).
F.
Hope your recovery from knee surgery is going well Frank..
Hey. Frank the build is looking great. Keep the rebuild on the knee up too. The two will flying soon enough.
Back to building because:
.... the pain from the knee replacement surgery 3 weeks ago is slowly subsiding.
.... the pain and frustration from the new modelling disease (RPAS, TCARS, AGL, etc) is setting in.
Can only sit at my workshop desk for a max of 30 minutes because I cannot elevate my leg and my back starts to hurt.
- finished the cockpit top
- did the wing doublers for the landing gear (plywood to balsa ribs).
- laid down the trailing edge and leading edge spars.
- set the ribs in place.
Good news- the smell of balsa dust is a better pain killer than Oxycodene! ;) . For me balsa dust is more addictive.
Frank
ps: went from 13 pain pills a day to 2 (extra strength Tylenol) in the last week.
Frank Good to see you are getting back into the balsa dust, I am laid up as well, with feet and legs swelling and have to set down to build. I agree with you on this crap that is going on with MAAC and TC, who would ever think this would have happened.
As for pylon racing this summer, I am planning a race in June, just hope I am well enough to put it on and hope to see you at it.
Our club field should OK as we are well out of a no fly zone, with only one registered flying strip about a good 5-6 miles away.
How to curve balsa wood along the grain.
This wing is built a little backwards per the instructions because the airfoil has a Phillips Entry (flat bottomed behind the main spar but semi-symmetrical ahead of the spar).
The wood has to curve up to meet the leading edge.
Solution- 3 passes of a wet paper towel over the leading edge sheeting and the wood curved immediately so I did not have to use clamps. Pins were fine. Clamps can dent/crush this light balsa.
Photo 1- the wing pinned down so the glued trailing edge sheeting could dry straight (overnight). Note: the bottom leading edge sheeting is not glued to the ribs or LE yet because it has to curve up.
Photo 2- three passes of the wet paper towel (on top) and the balsa curved completely into the rib. Note: the wing is held up-side down in the photo. You can see how the water yellowed the top of the wood.*
I believe in miracles!
Frank
*Note: when bending balsa, the curl will happen opposite the wet surface. In this photo the wet wood at the top wants to expand. The dry wood under it does not so it curls away from the moisture.
If you wet both sides, the wood will stay straight. The curls cancel out.
Second wing half.
Deviation from the instruction manual...again.
per instruction manual- build two separate wing halves then butt-join them and add fibreglass over the joint. Problem- there is no continuity between the halves.
per my method
- build one wing half minus the front top (LE) sheeting, place it on the plan and put 2 pins at the center rib. Lift up the finished wing to the required 3" dihedral at the tip. Build the second half directly to it flat on the board at the root. Reason- do not have to build accurately and the center joint will be perfect without any trimming or sanding. Been there!
- ditch the 2 small hardwood landing gear blocks. Replace it with one long one that becomes a dihedral brace at the same time. Much stronger.
Photo 02- note the finished right wing with the two pins at the root and the red thing propping up the wingtip at 3" dihedral per plan.
Photo 06- note the two small landing gear blocks that came with the kit versus the new long, continuous one above them.
Frank
Photo 1- all thumbs beginner- put my thumb through the wing sheeting trying to remove a pin. What a Klutz.
Photo 2- wing taking shape- note the continuous landing gear block acting as a dihedral brace as well. It is wrapped in dental floss and 5 minute epoxy to stop it from splitting. It is still loose. Will secure it to the ribs, top, bottom and sides before the top sheeting is installed.
F.
Installing the landing gear.
Did not like the plans so did the reverse. These are torque rod landing gear. Drilled the hole into the hardwood block/spar closer to the center line. The plans showed them on the outboard end. Inboard is thicker and much less likely to split on one of my bouncy landings.
Note: this plane was originally designed for an .049 gas engine which always meant a slower dead-stick landing. As an electric we can do a smooth power-on landing (if you are Glenn). Any bounce will have more energy behind it. That's why all the extra time spent on strengthening the wing and landing gear.
The landing gear was to be slipped into a hole drilled into the hardwood landing gear block. This leaves it open to splitting the wood on a hard (normal?) landing.
Trick: I use a piece of brass tubing and glue the tubing into the hole. Because it is a larger diameter, it spreads the load on a larger surface. Also, after many landings, the hole will never wear larger and start the Lg leg moving back and forth.
Photos show the brass tube, inserted into the wing hole and then landing gear in place.
I have done this on all my scratch-built airplanes including my 60 size pattern plane. It works well.
Frank
ps: sorry for the messy background in the photos. I do this on purpose because it keeps Andy busy mining the background of every photograph. ;D
Lookin' good! 8)
Finishing the wing.
Sand the rectangular profile leading edge. Trick: mark the very leading edge with a magic marker at the tip and the root. Connect the two dots with a steel ruler with a magic marker. This means you can sand to it from the top and the bottom. Leave the line showing. Then you know you have not scalloped the edge. When the profile looks good and smooth, sand the marker line away. It will through most light (white) covering if it is not sanded. Photo 37
Cut the CA hinges. I cut them into rectangles (left pair) Trick: cut the four corners off on each hinge. (right pair). It makes the installation much easier because the corners will not dig in. Photo 40. Do not glue them in until after the covering is finished.
Finished wing- photo 48- it is a very strong wing!! Good. I know the pilot.
Next power calculation and motor selection and installation.
Frank
Good progress Frank
I'm so glad this kit is getting built and thanks so much for sharing it with us all, Frank.
Have you got any idea yet of finishing scheme?
Simon:
re: your "Have you got any idea yet of finishing scheme?"
Yep!
When I started reading Simon Chapman's magazine collection I came across this in an RCM&E magazine.
The main reasons:
- the accents on the fuse are linear , fore and aft. It removes the clumpiness of the nose whenever it is a single colour. (yellow or grey)
- I have the colours- I still cannot drive and do not want to impose on TEMAC"s Three Amigos* who have volunteered to drive me around the city. Oh, yes, as well, I am cheap!! ;)
- it is not the MD** trademarked colour scheme. ;)
Frank
* Mark, Andy, Graham.
** Michael and David- the yellow with red tips.
Gorgeous! My favourite scheme actually! Bravo.
Picking the power system. (Experienced modellers, please stop yawning)
step 1- Gather important background info:
- declared weight of model- 21-28 oz. Note it was designed for a Cox TD.049, a very lightweight but insanely powerful IC motor. Have to pick the top end of the weight.
- space in the nose. The nose ring decides what size motor can fit.
- prop size max- .049's used 6x4 props.
step 2- inrunner vs outrunner? an inrunner has a fixed outside case with the shaft spinning more like an old brushed motor. The outside case can touch the fuselage. An outrunner has the outside bell spinning. It needs space/clearance and cannot touch the fuse. As well, the wires need space to lead back or the spinning bell will sever the wire(s). Don't ask me how I know! ;)
Inrunners- generally-much higher KV* and need smaller props (kv's run from 2500-4500)
Outrunner- lower KV (800-1200), swinging a larger prop- 8-11" for a small 450 size motor.
Step 3- How many watts do we want/need? A watt is VOLTS (11.1v) x the AMPS the motor draws.
Guideline:
Cub-type: 80 watts per pound
P-51- 100 plus watts per pound
aerobatic/3D planes- 150+ watts per pound
Pylon racer: 200+ watts per pound
If your name is Ben Feist or EdEdge: they start to feel at home at a kilowatt (1000 watts) per pound.
guidelines:
"always overpower an airplane. You can always throttle back...if you have to!"
"There is nothing more difficult than trying to fly a marginally powered airplane".
Decision Time
power needed for this approx. 2 lb airplane- 200 watts minimum. (2 pounds x 100 watts per pound)
motor type- inrunner because of the prop size and minimum nose clearance (interior)
My pick
An E-Flite Series 6 inrunner 2700 kv. This is a 400 watt max 36 amp max (burst) motor on 3 cells. It is a 28mm diameter motor same as the old Speed 400 size. I have 4 of these and are amazing in small fast planes. One is in my Nooner pylon racer. Known results at different APC prop sizes:
- 4.1" x 4.1" - 18 amps (200 watts)
- 5" x 5" - 25 amps (278 watts)
- 6" x 4" - 28 amps (310 watts)
Will pick the 6x4" prop so it has bite for take-off. The smaller the prop the more difficult the acceleration for take-off. Again, please don't ask me how I know. ;)
I will team it up with a 35-40 amp ESC.
The photo shows the motor with two parts to the nose ring.
Decision made.
Frank
ps: An indication of how far this hobby has come. This motor is the same size as the old Speed 400 brushed motor at 100 watts Max. This motor has 4 times the power for the same size and weight. EFLITE has a 32 size inrunner motor of the same size for their jets that produces over 1600 watts (over 2 horsepower) or 16 times the original speed 400 motor. I believe in technology... and flip phones! ;D
*a KV is the number of revolutions per volt of input power in a no-load situation.
Thank you for such a clear and well-presented note Frank. I'll keep it as a starting point reference. I had read that inrunners are not for airplanes so the one I have is gathering dust. I'll definitely look to it for future projects.
Thanks for this Frank - Great breakdown!
I will weigh my Fiasco tomorrow, but the kit indicated a weight of about 30oz (about 1.9lbs)
Based on this I selected a 2826 1,100KV outrunner rated at 186W on 3S & a 30A esc.
I was planning on using a 10x5 prop.
I suspect that I'm probably underpowered a little
Thanks Gord and Mark.
Mark- Your Fiasco will probably be fine for your kind of flying. 3D requires enough power to prop-hang. You and I don't do that kind of flying. I suspect it would/could be a handful at 120 watts/pound
It is only a rough guideline.
Now you know why you bought a wattmeter. :)
Frank
Great explanation on power requirements.
You must have a lot of time on your hands to write such epistle. ;)
Keep up the good work.
Guy
Ailerons.
This model uses the old torque rods with a single servo in the center of the wing. See reason below*. Problem- the rod breaks through the balsa aileron, either top or bottom (see photo 59). Here is how I fix it.
Step 1- cut a piece of tubing, either brass or aluminum, that just fits the diameter of the torque rod. Photo 60
Step 2- enlarge the hole in the aileron so the tube fits.
Step 3- place a drop of oil on the end of the torque rod for 2 reasons: i) for easy fitting and ii) so glue will not stick to it. Photo 61
Step 4- epoxy in place, lay a piece of fibreglass cloth over the edge so it covers the top and bottom, add a piece of waxed paper, add a piece of wood on both sides to squeeze the glue and add a clamp. The pin is necessary so the wood will not slide off the angled aileron when the clamps are added. Photo 63, 69.
Step 5- slip the aileron in place to make sure the tube is angled the right way before the glue cures. (photo 67) Remove and add clamps around.
Notice that I do not cut the extra cloth at the trailing edge until after it cures. reasons i) maximum size and strengthening, ii) easier to trim once cured. One pass of a #11 blade. iii) you cannot fold cloth around a sharp bend. It will radius and create two voids between the wood and the cloth, one on top, one on the bottom.
Guaranteed it will not pull apart. I do this on elevators as well when there is a "U" shaped joiner wire.
Frank
*Back Story: The reason torque rods were used was that a mini servo in the '90's was $28.00. A "Y" harness cost $15.00. Individual aileron servos in the wing would have cost $71.00 versus a single servo in the middle at $28...but that was in '90's dollars. Today's equivalent of $140 versus $56 dollars. The price of a fully flyable second hand foamy airplanes today. Now a servo is $6.00 and a Y harness is $4.00..in 2023 dollars. A non-issue.
Fibreglassing the wing center section.
Step 1- sand the area
Step 2- cut the fibreglass cloth. I used 1/2 ounce cloth- bought at a swap meet. See photo 71- note- the narrow glass cloth came with the kit. The wider one is the one I am using. reason- It is better to have the cloth be wider than the fuse so the fuse does not crush the thin balsa wing sheeting. I know the pilot who will be flying this plane. ;)
Step 3- apply 5 minute epoxy to the wing skin wider than the cloth. I use folded foam as a brush (see photo 72). This way there are no sharp edges to pull the glass. Do not brush the epoxy, dab it otherwise the cloth will stretch. Lay the glass cloth over the glue.
Note, like covering- do the bottom first so the top overlaps at the bottom where it cannot be seen. Do not worry about missed spots. Can be filled in tomorrow.
Step 4- apply 2 pieces of waxed paper. Use your fingers to squeeze the epoxy through the cloth. Let it dry overnight. See photo 73, 74
Step 5- repeat for the top glass cloth (tomorrow). Photo 75 shows the top. Note the bottom glass overlaps the top about 3/4" at the leading edge and trailing edge.
Frank
Finishing the fuse.
- added the cheek blocks, top front deck and whole cabin structure. This will allow me to futz with the motor installation tomorrow.
- note the wing drying in the background.
Letting it dry/cure overnight.
F.
details
- shaped the bottom balsa nose block. Cut it into 3 pieces with a razor saw so there would be a hatch- Photo 97
- installed the rudder and elevator servos. Photo 98
- made the plywood motor mount. Made it large, held the motor in place and scribed the nose shape onto the back of the motor mount- Cut it to shape. Photo 99
- with a drill, dug out the thick plywood IC motor firewall until I could fit in a Dremel Sanding drum and open the hole enough so the motor could slip through in case of replacement, crash, etc. Photo 00. Oh, yes- the sanding drum started to char the plywood and the smoke alarm went off in my shop. My wife yelled down "are you trying burn us out of our house again". "Sorry Dear."
- Glued the nose motor mount in place and am letting it dry overnight. (no photo, stay tuned)
Frank
The motor is in!
photo 04- The motor mount cured overnight.
photo 06- Oops! the nose ring supplied in the kit blocked the air holes. Queue the Dremel sanding disk to open the air holes
photo 07- the motor can now breathe again.
photo 08- nose is finished.
Hatches How to locate magnetic catches without needing to be accurate.
These rare earth magnets are available at Lee Valley Tools and Princess Auto.
Design considerations. I always put the registration pin or the tongue closest to the prop. The magnetic catches are downwind (rear of hatch) so that the wind cannot catch it and open up. I can prove to you that magnets closures on the front can blow open.
Step 1- drill a random hole on one side of the hatch end. I used the fixed portion of the hatch. Make the hole larger than the magnet, fill it with 5 minute epoxy (photo 52. Note it is crooked. Does not matter), lay a small piece of waxed paper over top and place any flat metal object across the magnet (photo 53). Used a screw driver bit. It automatically pulls the magnet flush with the surface. It cannot sink into the epoxy as it cures.
Let it cure.
Step 2- Locate the magnet on the hatch. I dabbed red paint on the fixed magnet (photo 56) and closed the hatch. It transferred the paint onto the wood of the hatch (photo 57). Take a drill bit about 50% larger than the magnet and drill a hole. Fill it with epoxy, place the magnet in place (photo 58- note magnet is crooked, no problem), insert a piece of waxed paper close the hatch until the glue dries (photo 59). Hatch complete! Note: watch the polarity of the magnets. Don't ask me how I know. :-)
This method is fool proof, no building accuracy required and works perfectly every time. The waxed paper is to avoid oozing glue from permanently gluing the hatch shut.
Frank
Stabilizer and elevator halves.
Problem: these are made of 3/32 sheet balsa. The elevators are separate, then joined with a hardwood dowel. When the glue dried the halves would/could twist.
Real issue- this plane has about 3 times the power for which it was designed. This elevator would split or deflect because only one half has a control horn/pushrod.
Solution:
- add a piece of balsa between the elevators to reduce twist. It adds beef.
- fibreglass* the entire joiner area. Used 1/2 ounce cloth. The waxed paper (again!) allows me to squeeze the epoxy flat and eliminates the annoying glass fibres sticking up. When cured it will be absolutely smooth.
The 4 clamps are to make sure the radius of the wax paper at the leading edge stays tight to the wood. Otherwise an air bubble will form there. Then the only solution will be to cut the bubble out or sand it out.
Have done it all my planes with a dowel or balsa joiner for 35 years. Works well.
Frank
* for 4 summers in University I worked at CS Yachts in Brampton so have been around fibreglass for 45 years. My strengthener of choice.
Wing hold-down bolts.
On a small plane, the blind nuts/T nuts require a fairly large hole in a small plywood plate. Not a good combination.
Trick- drill a bolt sized hole through the plywood plate and install the blind nuts backwards. Hold them in place with a piece of balsa. See photo. In the photo, the epoxy is on top of the balsa and it is slipped under the plywood hold-down plate.
benefits:
- the hole through the plate is smaller, leaving the plywood stronger.
- the back of a blind nut is tapered at the back side. It acts as a funnel to guide the nylon bolt into the threads. Works really nicely.
- the balsa acts as a brace for the plywood. Doubles the gluing surface.
Note the missed centre hole. That's when I went to the double bolts and the reversed blind nuts solution.
Frank
It looks like an airplane. First time assembled.
Trick: there were some dents and scratches in the balsa sides. See photo 71- One pass of a wet paper towel and the dents swelled and disappeared within 5 minutes. Prefer this over filler because covering does not like to stick to light filler.
Wing hold-down bolts
I run the wing bolts through a pencil sharpener to make a point. This auto-feeds the bolt into the blind nut. Works like magic.
When cutting bolts (metal or plastic) put a regular nut or a blind nut on the bolt so when you shorten or sharpen it, the screw thread automatically removes the burrs and opens up the threads at the cut.
Photo 83 is of the actual bolts for the Chipmunk
Photo 84 is a sample larger nylon bolt so it is easier to see.
Frank
I had a lot of trouble beveling the joiner between the 2 halves of the elevator because it was ply.
In trying to bevel the joiner, I would sand too much on the balsa sections
Does using a dowel prevent the need for beveling?
Looking great btw!
Mark,
Thanks. Your post contains 2 questions. The easiest one first:
1) "Does using a dowel prevent the need for bevelling?"
No, it does not but it gives you a heck of a head-start.
2) "I had a lot of trouble beveling the joiner between the 2 halves of the elevator because it was ply."
It is only difficult if you use the wrong sanding tool.
Below is the photo of the 4 sanding tools I use: (left to right)
i) loose sandpaper- best for contour hand-sanding of any surface with multiple curves like fuselage bottoms, turtle decks, wing leading edges, curvy transitions like wing fillets. See next post how to do the official "Sandpaper Fold"
ii) Dura-Grit flat file- It has a coarse and a fine side. Great for sanding small straight surfaces. benefit: it allows club member Roger Mason to keep buying model airplanes. ;D
iii) sanding handle- it has foam under the sandpaper so it does not leave hard edges on curved surfaces.
iv) Sandpaper block The best item and best for sanding the leading edges of elevators, rudders and ailerons. A piece of hardwood (1" x 2" x a length) with sandpaper glued on each side- coarse on one side, fine on the other side. This one is 15 years old and still sands like new.
The sandpaper needs to be glued onto the wood, not nailed, not stapled and not held in place. It cannot move or it will self destruct. Use either contact cement or epoxy. Do not use wood glue, it will wrinkle the sandpaper. When glued, place sandpaper side down with weights on top so it dries absolutely flat. Next day, glue the other side.
Important: do not wrap the sandpaper around the block. If you do this the sandpaper will radius at the corner and will cut grooves as you sand. Best way: glue the sandpaper to one surface, let it dry, then trim it around the edges with a knife.
This tool would have fixed your plywood joiner bevel issue in 5 passes and be absolutely straight.
I use other stuff a lot like files, razor planes, X-Acto blades, etc. but these are the major sanding tools.
Frank
The sandpaper fold.
I was taught this in 1972 when sanding the bottom of a racing sailboat*. Sailboat bottoms could only be hand-sanded wet because no surface was straight or flat.
Take a full sheet of sandpaper. Fold it in half one way, unfold it and fold it in half again the other way. It leaves a cross on the paper. Tear any one of the folds from the edge to the middle. Fold it so no two sandpaper surfaces touch each other. This way it does not slip. Sandy surface to sandy surface would destroy itself.
When the piece of sandpaper has lost its edge, use the other side until it is gone, then unfold it and re-fold it so the two remaining surfaces are exposed.
See the photos.
Frank
* For Rob and BJ... it was a Redwing 30 C&C design called "Herself" out of Hamilton. The reason for the name: the owner was Hugh Drake and raced with his wife and 3 daughters.
The person who taught me the sandpaper fold was Dr. Doug Hood. The Susan Hood race in June every year out of Port Credit is named after his daughter who was born while he raced in this overnight race (85 nautical miles) and won the first one.
Covering!!
Prepping for covering:
- sanding all corners smooth, filling dents and imperfections with light weight spackling.
- make sure that all moving surfaces work properly and have clearances. reason: all clearances need to be big enough to allow 4 thicknesses of covering (esp. edge of ailerons)
- all hinging is in place on the ailerons but not glued yet. Hinges will be glued after covering.
- the edges of the rudder and elevator have been angle-sanded. Will be using the covering as a hinging material. The 3/32" balsa is too thin for CA hinges.
- wheels off, no pushrods yet, no control horns. I do those after covering.
- stabilizer and rudder/fin are covered separately and installed after all the covering is done.
Order of things:
fuse- cover the bottom first, two sides next, then top. This is so edges of the covering are least visible.
wing- cover the bottom of both wings first, then the top the wings. Reason- so overlaps happen on the bottom of the wing and not visible.
Colours
Rule- do the lightest colours first so the darker colours will not show through.
try to match the temperature range of different covering. Lower temperature covering (Solarfilm) can be installed over top of higher temperature covering (Monokote, OraCover). It is very frustrating to try the reverse.
Cover the biggest pieces first- wings, stab, fuse, fin/rudder. This is so you can use cut-offs of the larger items on the smaller ones.
The filler is drying overnight so the covering will start tomorrow.
Frank
Covering
Gentlemen, start your heating irons.
prep work:
i) make sure you have enough covering for the model. See photo 98 of half of my collection. Found it. (red, white, black, grey)
ii) always use a brand new blade. The new blade is in the red knife for covering. The next to new blade is in the blue knife for wood trimming. Photo 95.
note: the green masking tape...to stop the knife from rolling off my desk. 5 Years ago one rolled off and stuck straight into my thigh and hit a vein. The blood circle on my pants was 6" in diameter. That's not what hurt. Trying to explain it to my wife did! ;D
iii) this plane uses two colours on the wing. Grey inside half, red outside half. To give it a flat surface for the transition I sistered the ribs in that area. Attached 3/16" balsa to the ribs and held in place with clamps. Photo 96. When dry, will trim it to the shape of the rib. A lot simpler than making templates and pre-cutting the wood.
iv) did some final filling. Here is a photo of the filler I bought at Home Depot. There are about 3 brands. Pick the one that feels empty. It is the good light-weight one. See photo 97. I apply it with my fingers. Easy to shape.
Did I tell you to use a new blade to cut covering? ;) Otherwise it tears and hooks.
Frank
starting to cover:
Wing
- cover the inside corner of the ailerons first...always. Doing it later will be ugly! Photos 99 and 01
- lay the covering over the wing and tack down one corner (size of a quarter). Stretch the long side (leading edge) and tack that down.
- lightly stretch the covering and do the opposite two corners so 4 corners are stuck to the wing.
- attach each of the 4 sides between the corners carefully. Goal: to make it as flat as possible...without wrinkles... without shrinking it. Photo 03
- clean up each corner, do overlap edges at the leading edge or trailing edge by about 1/4". Photo 28
Note: do not shrink the covering with a heat gun until all the covering is in place, properly sealed and trimmed. reason: Both sides of a surface should be shrunk at the same time or the wing will warp. Not too risky on this model but guaranteed to ruin your day if you are covering a 2 meter glider wing.
Frank
Covering the wing continued
- cover servo protrusion first. This way it will be covered when the main sheet is added. Note- it is off-centre. See photo 29
- tack down the 4 corners. Do not go past centreline of the wing. This needs to be slit because of the dihedral. See photo 48
- do the edges completely around the perimeter. Note: none of the center was tacked down onto the ribs. This will be shrunk in place when heat gun is used.
- Photo 50 shows the top and bottom done. Note: nothing has been shrunk yet with the heat gun.
Doing the red tips
- cut the overlap with a metal ruler. Photo 52. Note the ruler is upside down. It is more accurate that way because of the cork glued onto the bottom. That space allows the knife to wobble.
- start at the colour overlap so it is absolutely parallel to the rib line. Then tack the 2 overlap corners, then seal the colour overlap completely....If you forget, the seam will pull apart when you go to shrink the covering. Don't ask me how I know.
Wingtip
- pull it as hard as you dare and tack it down on the high point of the tip. Photo 80. Instead of tacking down the corner, only tack the high point.
- OOPS! Pushed my thumb through the trailing edge.....just so Mark will feel better about doing it several times when covering his latest project. Moved it back together again, and glued a doubler onto the bottom between the 2 ribs. Clamped it in place. Photos 83, 84
Time to quit while I'm ahead. Let it cure overnight.
Frank
The wingtip
Always tough because of the curves involved.
Do the bottom first. Hold the wing between your knees with the wingtip up. Pull the covering as hard as you dare, touch the covering iron to the film as you stretch it around the curves. Photo 93. Try to bring it halfway up the tip. Only the front of the wingtip needed the covering slit to get it around. Photo 94.
Do the same for the top covering. This encounters greater curves.
This covering has not been shrunk yet. Only sealed at the perimeter.
Trick
Finding the hinge slots- when the wing is done, hold the aileron beside it and cut the hinge slots in the wing. Photo 98.
When you cover the aileron, do the reverse and transfer the wing slots onto the aileron.
One wing half done both sides.
Frank
Oops.
Two mistakes:
1) the red tip looked looked angled on one wing. I made the joint 90 degrees to the trailing edge, not the leading edge.
Fix- cut a small strip of red with a ruler , make the angle and overlap it to correct the mistake. See shots 00 and 03.
2) The red on one aileron did not match the wing. Cut a piece of red, one edge with a ruler, line up the line and attach it with heat. Photos 06, 07, 08
The wing is now done. Now it can be treated with the heat gun.
Frank
Trick- how to remove the backing from a piece of covering.
One method- poke your X-Acto #11 blade into a corner of the backing (photo 09), pull up and to the right with the back edge (not the sharp edge; photo 10). It will peel it.
Frank
Heat shrinking the covering:
When doing the heat shrinking, I do one wing half at a time both top and bottom.
Notice my left hand (photo 12) is adding twist so that the trailing edge is higher than the leading edge. (wash-out). I hold this twist while shrinking both top and bottom.
Wash-out adds stability to the wing. When nearing a stall, it will force the middle of the wing to stall first. The tips keep flying and stops the plane from flipping onto its back.
Reason: In general- a wing stalls when the angle of attack is about 15 degrees*. By adding twist to the wing of about 2 degrees, it will have an angle of attack of 17 degrees before it stalls. When the inner wing stalls, the outer halves are still flying by 2 degrees.
Wing is finished- ready for servo installation and hinge glueing.
Frank
ps: the Northrop flying wing YB-49 has a wash-out of 7 degrees to make it fly.
ps2: corrections made to stall angles courtesy of "Full Size Fly Guy"
Solarfilm hinges.* How to make them.
This is a hinging technique I use on smaller planes (less than .10 size) and it works wonderfully well. Not good for high speed yank-and-bank planes but good for reasonable speed models... even though my 150 km/hr Nooner uses this on the elevator and ailerons....no problem.
Description: Covering is done on one side. When the surface is covered on the other side, the two glued sections at the hinge will fuse and become the hinge.
Advantages
- for thinner stabs/rudders where it is hard to cut a slit in the balsa for a CA hinge.
- gapless. Improved turning. There is no gap for air to leak from the high pressure side to the low pressure side.
- no cost, no out-of-stock situation.
Steps
1) Cut/sand a bevel into one of the surfaces. Usually the elevator. The angle allows the deflection.
2) Cheat! I place 2 small strips of celluloid tape to hold the surfaces together. See photo 14.
3) Cover the bottom of the stab first while the elevator is folded double (180 degrees full "up"). See photo 18. Attach the stab covering then work up the hinge area and then the bottom of the elevator while folded 180 degrees. Photo 19.
4) do all the detail work (edges, tips, etc.)
5) Do the top sheet. I did it in 2 halves. Attach to the stab first, then while holding it in maximum deflection, attach the covering to the elevator. Make sure to heat the hinge line so the covering will fuse glue side to glue side (top to bottom)
6) Do all the detail work.
Photo 22- full "up" deflection.
Photo 24- full "down" elevator.
Frank
* the name comes from Solarfilm which is/was the brand name of the film of choice in the UK. Their version of Monokote.
Faking it.
Here is how to not waste time trying to make something symmetrical. The black nose of the fuse needs to look symmetrical.
Step 1- cut a piece long enough to cover the area. Make sure it has a straight edge.
Step 2- follow the lines of the black around one side of the fuselage until it looks good.
Step 3- cut slits across the nose so it can overlap to form a curved surface across the top of the fuse. When attaching the covering, start at the back and work forward. This way the overlaps are down wind.
Step 4- Cut the opposite side. It does not need to be accurate. Note inaccuracies at the right side of 26 (left side of the fuse).
Step 5- Cut a strip with at least 1 straight edge and make the curve to cover the ragged edge. Photo 27
Enough to meet the 50/50 rule. Finished photo is 29
Frank
Final Details:
cover the nose hatches.
1) Fresh air!- drilled a hole in the front with a progressively larger drill bit. Final opening with a Dremel sanding drum both from the front and the inside.
2) covering the two hatches with film.
3) faking the inside with Dollarama paint. One coat worked fine. Photo 37
Frank
Mid-course correction
I did not like the way the turtle deck (curved fuselage top behind the canopy) was designed so I built ahead and am now forced to deal with it.
(Wrong) Original Approach- the plastic canopy was one piece all the way from the firewall back to the rudder fin. The fin was to be glued on top of the flimsy plastic canopy as shown in the first picture. I know the pilot who will be flying this plane. It will not last...especially with 3 times the power for which it was originally designed.
New Approach- build the turtle deck out of balsa and cut the canopy apart as if it were a normal canopy.
The second photo shows the fin structure with balsa attached to both sides so the covering will stick to it.
The third photo is the fin structure held in place on the fuse.
Will have to fake the curve someway or somehow. Stay tuned. ;D
Frank
@Frank v B , concerning the "Will have to fake the curve someway or somehow."
How about 1/16 sticks to fake the curve.
Alternatively, 1/32 sheeting.
Other option, foam block shaved to shape.
I am running out of ideas...
Guy
Guy,
My options are still open..except for the foam* option..... "Don't make a decision until you have to".
Have started to build the ribs. See photo. Note that I build them without shape, let the glue dry, then shape them.
My first option is to use sticks because this is a compound curve (up/down, sideways). Will probably put covering film over the structure.
Sheeting can only handle one curve.
Frank
* foam, when sanded, has a habit of sticking to clothes, showing up on living room/dining room floors...leading to the wrong conclusion...."get rid of the model airplanes" as opposed to "stop using foam". I can't win. ;)
How about BBQ skewers or dowels?
Also - Why did you choose to cover most of the plane before building this section?
I'm finding that in the few kits I've built, that I sometimes don't understand the order the instructions are saying to build in.
I don't always follow those instructions, but understanding different builder's methods will help me make better decisions
How about a custom 3D printed turtle deck? You'd get the shape you want and the infill could be minimal to keep it light. You'd just want it in something like ABS so it doesn't warp in the hot sun. I know plastic is sacrilegious to a true modeled, but it's also a solution😀. Your build is really great Frank!
re: questions:
Mark
- How about BBQ skewers or dowels? They tend to be heavy versus balsa. Balsa is also easier to sand (read as : "easier to sand out errors")
- Why did you choose to cover most of the plane before building this section? Sometimes problem solving issues need to spin around my head for a while. It is not really out of sequence because the top is covered last in the covering sequence.
Gord
- 3-D printing the back end?- You are coaching someone who uses a flip phone. ;)
20 minutes later the stringers are in place and drying over dinner. No foam dust particles. Will work out fine.
Frank
Geoffrey DeHavilland would be proud Frank!
Thanks, Gord.
Final assembly:
I always use the following 3 step method to attach the wing, stab, fin/rudder to get perfect alignment without needing to be an accurate builder.
Step 1 - attach the wing properly with screws and leading edge dowels. Try to get it as true to the fuse as you can...by eye. Let everything dry/cure
Step 2 - attach the stab/elevator so it matches the wing when looking down the nose (the airplane's, not yours!) with one eye. I never measure from a desk-top to the wing/stab. Let everything dry/cure.
Step 3 - Attach the fin/rudder assembly and tape a triangle to the stab/fin while the glue sets. Photo 75. Let it cure.
Note in the fin attachment I used toothpicks to act as a bit of a key into the stab. Photo 74
As long as the wing/stab/fin are in alignment, it doesn't really matter whether the fuse is straight. This way there is no coupling* in any aileron/elevator/rudder movement....beyond the flaws in the airplane's design.
Frank
* "Coupling" is when surfaces are not parallel or square to each other. A movement in one (pitch, roll, yaw) will cause a movement in another. Example- A misaligned stab will cause some roll when deflected.
First photos... assembled!
Still have to do some details
- clean up covering
- attach pushrods
- make and install tail wheel
- install the electronics permanently
Cute as a button...with a snarly 300 watts* going through it! ;D 8)
Frank
* Still have to weigh it with the electronics/battery in place.
Note: 300 watts is exactly .4 horsepower! Yes, a little overkill.... because I can. ;)
She looks beautiful Frank!
Thanks Mark.
Final details done:
- wigglers are attached to servos (rudder, aileron, elevator)
- faked a tail wheel
- installed the ESC (35 amp)
- installed the battery tray and Velcro
- installed the receiver
Interesting: the plane balanced on the CG without the battery. Had to put the battery as close to the CG as possible. Not in the forward hatch.
Done!
Frank
Final stats.
Plane weight 24 oz ready to fly.
E-Flite inrunner 6- Max power 400 watts
Watts per pound- 267
Original objective from my first post: "power- TBD but it will be "enough plus 25%". "
"Missed it by that much" on the good side. Actual result: "Enough plus 50%!!
Conclusion- it will fly...vertically!!
May have to use the throttle. ;D
Frank
https://www.youtube.com/watch?v=oPwrodxghrw
Frank Race it!!!
Maidened the plane at Monday's BBQ for Canada Day. Took off well but spit the prop at about 4' altitude right after take-off. Did a Sullenberger on dry land. (Could not make it to Teterboro)
Used the same prop but with a normal collet prop adapter. It flew well and fast. Flew hands-off after trimming it.
Neat project.
Frank
Photo 1- the retrieval crew found the plane. Looks like Andy had to go to the bathroom. :)
Photo 2- found the prop stuck in the grass about 20' east of the runway.
Andy's great photos of the maiden.