I’m going to assume that were starting with the wing tube socket installed (step #21) and the wings are done with the leading and trailing edge stock installed and sanded to shape.

First we are going to do all of the drilling that we can on a drill press. Drill 4 of the square mount pads and all 4 of the rectangular mounting brackets dead center with a hole sized to the diameter of the bolt your going to use. Carden suggests using 8-32, I’m using 4mm. With the remaining 4 square pads drill a hole for the blind nut, again dead center.

On two of those pads add an additional hole clear of the blind nut. This is the setup pin hole. The setup pin will keep the wings level when the anti-rotation bolts are removed. This is handy while you look around for your socket driver at the field. Its just an affordance for setup & tear-down and not a load bearing part.

Next find the root cap stock with the pre-drilled socket tube holes in it. Mark the center line of the plank and then transfer the locations of the mounting pads to the center line. Use one of the pads and a square to mark the locations of the pads. Cut these out inside the lines. Sand until the pads are a snug fit.

Install the blind nuts in the wing pads. Place the pads into the root cap holes you just cut. The setup pin hole should be pointing towards the tail. Tack glue the pads with some CA. I just did the 4 corners. I’m using polyurethane glue to install the root cap so it will make a good bond later on. Cut the root cap stock in half to make two root caps.

For each wing we need to glue in the wing root cap. To do you have to cut away some of the foam so that the pads are recessed into the wing root. To do this I just fir the root cap over the socket tube and line it up with the center of the airfoil using the center line I drew earlier. Once its aligned I press the pads into the foam so it leaves a mark. Using a Dremel router I cut a deep pocket behind the blind nut so that no glue could enter the back of the nut. Then I set the router to cut the depth of recess needed for the pad and cut out the shape of the square mount pads. Test fit again and it should be good to go. Sand down the tube socket so that its flush with the root cap or even slightly inset.

Now to get a good fit between the wing root and the fuse sides. I think I saw this on FG somewhere else and it didn’t look like it could hurt. Flip the fuse on its side, put the wing tube through the fuse and mount one of the wings on top. I use polyurethane glue to attach the root cap. Make sure to get adequate glue around the ply mounting pads. Glue is going to come through the seams where the mounting pads are so put some parchment paper between the fuse and the wing to keep it from sticking. The glue takes 2 hours to set up so this step takes a while. You may want to label the wings left & right at this time because its hard to tell which is which after the root cap is on.

Resist the urge to trim the root caps, all that extra material is going to come in handy. So now its time to set the incidences. Use a good digital level and an incidence tool. Make sure your table is flat and level. Mount both wings on the fuse with the fuse flat on the table and upside down. Make sure that you got the right wing on the right side of the aircraft and that its underside is facing up. Use the incidence tool to find 0.0 incidence. Use a block of scrap balsa and some push pins to secure the wing in this position. Make sure at least one of the pins goes through the 3/8 square stock in the fuse sides. The soft balsa on the fuse sides is too flimsy to hold the wing and keep it from slipping. Take you hands off everything and verify the level still reads 0. Set both wings this way. The blocks will allow us to move the wing and find 0 incidence again consistently.

Now we have to find the locations of those blind nuts so we can bore a hole in the fuse side to match up with it. I have seen various methods suggested using tape or sharpened screws. This way is easier and, IMHO, more accurate. Use a pin to probe for the hole from inside the fuse. Don’t worry, the pin cant go through the ply block in the wing root so it can’t make big holes in the exterior of the fuse sides. Just the tip goes through the balsa, not the whole thing. The holes on the inside get covered up later. Once you strike pay dirt poke more holes all around to find the extent of the blind nut hole. This will help you see the center when you pull the wings off.

Pull the wings off and you should see spots on the fuse sides peppered with holes. Open up the center of each area with a pin or small drill bit. Make a sand paper drill from 220 grit paper and drill the holes but twirling it. Open up the hole until its the size of the perforated area. Slide the wings back on and check that all the blind nuts are accessible. You should also make holes for the setup pins at this time.

Now we glue the 4 remaining mounting pads to the inside of the fuse. The is the *critical* step. Once they are glued in the incidence of the wing is set and you cant change it. I do one wing at a time so I can have the incidence meter to make sure the wing is at 0. Use 30 minute epoxy, not poly glue, for this step. The poly glue could expand and seize the bolt. Put the epoxy on the back of the pads and screw them in place. Do not tighten the bolts down, just snug them. Check once again that the wing reads 0, it might shift when the bolts go in but I didn’t have this problem. Then just walk away. Wait till the epoxy has cured before moving anything.

Now its time to mount the setup pin. Make the pin about 3 inches long and use poly glue to install it in the wing. You only need it to stick out about 3/8″. If you leave it a little bit longer you can sand it down so its flush with the mount pad inside the fuse when the wing is installed. You may want to harden up the balsa around the setup pin opening with some thin CA. You’ll have to drill a hole in the mounting pad in the fuse side to match up with the pin. I strongly suggest doing this on a drill press. I tried it with a hand drill but the wood tends to ‘climb’ up the drill and mess things up. The drill press took more time but the result was much cleaner.

Last step, add the balsa spacer and the retention bands. This is pretty easy, just glue the parts in place. You’ll probably have to sand and shape the two forward bands to fit. Again I used 30 min epoxy so it didn’t get into the bolts.

This is the after shot, both wings still read 0.0 degrees. There is not slop or wobble at all. The bolts fit but are very snug and its a bit of a challenge to get them engaged properly. I’m going to put a few flight on the airplane and see if things sort of shake/wear into position. I don’t want to mess up a good things with sand paper just yet.

So some background on my experience is in order. When I was 13 I built a 6 foot span Spectra motor glider that I never flew. Before that I was building stick and tissue free flight models. Then there was a long hiatus fro the hobby for high school and college. I finally learned to fly in March of ’06. More recently I built an O2 electric profile and I have designed and built several of my own foamies. I have never built a giant scale airplane. I have about 5 mins of stick time on other peoples giant scale airplanes (Air McNair’s 35% comp arf 330 & Dan Bierlys 40% Wild Hare extra 300). I have never worked with foam cores before or painted fiberglass or used a scroll saw. I have never even started a gas airplane engine. So I’m a Giants n00b and this thread is going to be from that perspective. Its probably going to go into more detail than most build threads out there because its all new to me. The build will be shown in all its ugly duckling stages and any “oops” moments will be posted here.

It was hard to choose which airplane to build. I picked the Carden because I really like the looks of the airplane over the other 260 kits out there. I would have prefered to build a 300 but at this time no 35% 300 kits are out here. I couldn’t imagine spending this amount of time on an airframe that I personally didn’t like the looks of. Its a personal choice and it has consequences. This is more involved than say a Dalton where everything is laser cut for you. I wont be cutting any corners, I want a light, straight, contest grade airplane. Building is a hobby and flying is a sport. I’m as much a fan of building as I am of flying so there was no question, I was going to build from sticks.

The first step for me is setting up a flat straight build table. In fact I need two tables, one for tools and one for the building/layup work. The tables are going to be built based on a design I found linked from FlyingGiants. The build table is long and narrow, topped with a solid core door. The workbench is topped with some 3′x4′ ply that come pre cut from the hardware store.

Building Tables

I found a door at the Home Depot for $42, solid core, 30×80. I went for the cheapest and narrowest door I could find. I rented the miter saw for the project and ended up needing it for two days to get finished. You kind of have to cut as you go as not everything is going to be cut exactly right. After the first table was finished I discovered that the saw wasn’t square, it probably had 1-2 degrees of bevel. Make sure you square your saw before you start. I got the work table and all the legs for the build table done in one day. I had to make a couple of extra trips out for 2×4′s. The second trip the wood I got was softer than the first batch and that just sucked. I ended up throwing away 3 pieces and going back to Home Depot for more wood. The design is really solid and the 33 inch hight is sort of magic. Its tall enough for standing and short enough to sit at.

I have been putting some serious time into Sketchup for a new project. Since nobody on RC Groups reads this blog I think I can get away with posting pics of it here as examples before I mention it over there. Ok, on with the tips:

Make components of everything symmetrical. I do half the wing, half the elevator, half of the sides etc. Don’t duplicate anything, just make a component and copy it. Here you can see a shot of the new project and what you see is exactly 1 of each component in the drawing. This is the best way to cut down on your workload.

If something would be more convenient as a whole object, say a whole wing or the elevator use make a group out of them. This way they can be selected and manipulated as if they were one component without the duplicated geometry penalty. The Outliner is your friend here. You can rename groups and rearrange the group hierarchy in the outliner.

Sketchup makes it really easy to extrude things into 3D. Resist the temptation to make all your parts 3D. In the long run its just so much easier to manipulate things in a 2D plane than in 3D. It will save you a lot of work. You can place everything in 3D of course but you have to remember to keep things the right distance apart (3mm or 6mm depending on the depron or foam thickness your shooting for). You run into so many problems making geometry changes in 3D that its just safer to keep everything in 2D. If you have something complicated that would be easier to work out if everything were in 3d try making a copy of all the components and use the “Make Unique” option so your changes wont affect anything else. Usually you can work it out in 3D and then copy the changes back to the 2D parts.

If stuff suddenly stops forming nice surfaces its because all the points are not in a plane. Finding the offending point or points can be hard. A quick trick to see which points are off the plane is to use the scale tool on the component. If the scale tool even lets you stretch the component vertically its not a flat surface. Stretch it vertically and the high points will be exaggerated and you can find them easily. Here is an example where one of the circles is 0.1mm higher than the rest. Hard to see but with the scale tool its easy.

Don’t embed cut out marks in your components treat them like an overlay instead. It took me a while to grok why this is important. At first I was applying lightening holes and assembly cutouts right to the component geometry. This had lots of undesirable effects, It broke up the geometry and making changes was very involved. Now I apply cutouts as an overlay using a separate component. Then I group the cutouts and the main component together. Now I can play with changing the construction cutouts without affecting the component geometry. Also things like lightening holes that are supposed to be very similar can be a single replicated component. You can even lay them down with the move/copy tool. Another bonus us that scaling now works correctly. If you have a 3mm cutout in your component is probably a hard value that you don’t want to scale if you scale the component. Just extract all of that stuff out into a separate component and it wont scale. This is great for shrinking or stretching plans.

I gave up on doing tiled plans. Sketchup doesn’t support it natively and there is no good solution that I have seen yet. You can print plans at Kinkos on the large format printer and save yourself the trouble. The large format black and white printer will print up to 36″ or 90cm wide by however long you need, It’s a drum fed laser. An F3P model will cost you between $8 and $10 depending on how well you use the space. If Sketchup suddenly supports this i may reconsider but having the plans printed is very convenient.

Lastly get Bezier.rb before you get too involved in doing any curves. When its correctly activated you’ll find it in the menu; Draw ->Bezier Curves. This is the secret to nice bubble canopies and the other tricky curvy bits. Its a must have. I just wish it was in there from the beginning and it had an icon in the toolbox. Just assign it a hot key (I made mine ‘C’ since its rare that I draw a circle).

My biggest Sketchup time saver? The Spacebar is the default shortcut to get back to selection mode from whatever tool you using.

Look for plans of the new airplane as soon as I get one built and tested. At the rate I’m getting things built and flown it might not be till late January.

So in the hope that there will be more kits on the market in the future and more people building kits I put together some suggestions for the people who make the kits to help them sell a few more. This isn’t meant to get down on anyone or get negative. I’m sure anyone still making kits is in it for the love of the hobby. I know there cant be a lot of money in it.

5 Ways to Sell More Kits

1. Offer kits that people want to FLY and build. This should be the obvious part but its not happening. Example: Yak’s are hugely popular but there isn’t a single 50cc Yak kit on the market this winter. Update your kits with interlocking parts and prefabrication. Its not enough that you convert and old design to laser cutting, the parts need to interlock to make building easier. Doing menial tasks like beveling hinge lines are boring and take a lot of time. Prefabrication by machine saves build time and gets better results than many can archive on their own.
2. Offer complete kits. Or offer a complete, super high quality hardware package to complement a builders kit. Complete kits included EVERYTHING an ARF airplane would have had. This helps with estimating costs for the builder. A complete kit with hardware shouldn’t cost any more than a similar ARF (why should it?). With an ARF the costs are clear; with a Kit its hard to estimate what the project will ultimately cost. A key kit selling point is that you can get higher quality hardware than an ARF. Offer what you would want on your personal airplane.
3. Provide manuals online. Preferable in HTML with high resolution photos. This lets the builder see what they are in for before they buy the kit. It helps them feel confident that they can complete the project. Update the manuals as needed, HTML is easy to update. HTML manuals can be linked to in a build thread and the images can be more detailed and helpful than the smaller images in a PDF.
4. Provide help with Finishing. For the new generation of ARF buyers that have never built a kit the most difficult part is finishing. Have an ‘official’ color scheme and publish templates for cutting the covering. Provide some Vinyl Graphics (great free advertising!) with every kit. There is general lack of good covering and painting information out there right now that needs to be addressed.
5. Leverage the community. Encourage builders with a variety of skill levels to build your kits and post build threads online. If someone wants to do a build thread get involved and support their efforts. Accept constructive criticism and learn from their mistakes to improve your product. A good build thread can be better than the manual that came with the kit. Link to good build threads from your website.

I wish I was building an MX2 this winter but I may have to wait a few more years before kits of that airplane get produced.

And the wind is blowing, from the North West at between 4 and 8 mph in gusts. I was nervous about the wind, these were not ideal conditions. Still it was better than most days, it always seems to be windy here. The field is deserted and it hadn’t been yesterday and thats a very good thing. I put the wing on the Magpie, turn on the transmitter and connect the battery. Even if I don’t fly I should at least do some glide tests to check the center of gravity, right?

I did a range check and then gave the plane a gentle push. Too gentle. The second time, with an even shove the Magpie glides smoothly about 10 feet and comes to rest flat on the grass. No damage, the controls seem to be working properly and the CoG is just fine.

I throttled up the motor and held it at full throttle for 10 seconds and then shut it off. I felt the motor, it felt warm. It smelled of that burnt electric smell but all seemed to be in working order. I hoisted the airplane over my shoulder and held it ready for launch. I throttled up maybe 1/2 throttle, the airplane tugged at my arm and wanted to go free. My throat was dry. “Launch the plane, right hand to the stick… Launch the plane, right hand to the stick…”, I thought it over in my head. Go!

The plane leaves my hand and goes straight forward. Right hand on the stick. Its turning left into the wind. Its done a complete 180. Now its tracking cross wind towards me, my car and the trees at my back. Gotta think fast. I cut the throttle and glide in for a smooth landing about 10 feet from the trees. My heart was beating a mile a minute, I did it, success!

I got 7 more flight in before 6pm on a single charge. No crashes, bad landings not even a broken prop. Each flight got longer and more controlled as I got more confident. I did lazy eights, a couple of loops, then an outside loop I even flew inverted for a bit. In short I had a blast!

I would like to thank Roman Michael Möller for their work on Flying-Model-Simulator. Without 15 hours of time spent in their Sim I know things would have gone much worse.

More to come as I get time to write it…

Sport Wing

I used a different technique for applying the strapping tape to the sport wing that worked well. Join the wing as before (I used 5 min epoxy this time). Next split the wing cradles at the front into a top and bottom halves. Take some 150 grit paper on a sanding block and sand down the ‘speed bumps’ that remain on the wing cradles from where the groove is cut into the wing for the strapping tape. Cut both pieces of the strapping tape and apply them to HALF the wing, top and bottom. tape the ends down if necessary. Wrap the wing in a length of parchment paper to prevent it sticking to the cradles. Put the wing in the cradle and weigh it down. Don’t be afraid to use lots of weight, I used a sheet pan to help spread the weight out evenly. Wait for the glue to cure and then repeat on the other half of the wing.

Empenage

For the empenage (thats the tail feathers) I stuck to the directions for the most part. The dowel that came with the kit was a bit bent so I swapped it for a carbon fibre rod of the same diameter. For the rudder and vertical stab I beveled the edges into a point. For the horizontal stab/elevator I used a single bevel as suggested in the instructions. Make sure you use a fresh blade for making the bevel cuts. Cut against a straight edge with the knife pointed ‘in’ towards you.

Fuselage

I added the wing saddles and servo plates to the fuselage. I moved the servo mounts about 3 inches forward of the location given in the instructions. This was something of a judgement call. Most people on RC Groups note that the model comes out tail heave. Also I would have needed servo extensions (an item missing from the required parts list!) to put the servos that far back. Whenever you move a servo further from the control surface you increase the amount of flex in the pushrods. To counter this you need to stiffen them or add guides. The elevator pushrod travels far from the fuselage so guides would need to be pretty big. I’m leaning towards using bigger diameter carbon fibre rods instead.

The manual calls for applying some thin plywood planks to the top-center of the wing. These take the load of the rubber bands and stop them from being crushed. I replaced this with some extra strapping tape that I bent to fit around the leading and trailing edges. I’m not sure how this will work out, they may be too narrow.

Working with 5 Minute Epoxy

I did all the assembly work with generic, hardware store, 5 Minute Epoxy. Here’s some suggestions if you’ve never worked with epoxy or never worked with epoxy that sets this fast:

• Work with a kitchen timer. Set it for 5 minutes and start the countdown before you start mixing.
• Mix vigorously for 30 seconds.
• Buy a bag of cheap Popsicle sticks for mixers/applicators. Try the crafts section or a crafts store.
• Apply as little epoxy as possible, scrape off any excess. Epoxy is heavy and it won’t penetrate.
• At 2 minutes to go do not apply any more epoxy from this batch to the work, its too late.
• At 1 minute to go clean any epoxy off your hands with rubbing alcohol.
• Finally as always, do a test bond before you do the first piece of your airplane.

For jobs bigger than a couple of square inches (like wing strapping) I would go with a 30 minute epoxy so you have more time to get things in position.

Covering with ‘Wing’ Tape

‘Wing’ Tape is actually Acrylic packing tape. Its thin, light, sticky and very frustrating to work with. You don’t really get a chance to reposition this stuff if you put it down wrong. I actually broke off part of the rear fuselage trying to reposition some tape. It doesn’t do compound curves well. You have to make lots of small cuts.

I did the fuselage first and it took nearly 3 hours. By the time I was don’t the adhesive spray was starting to loose its tackiness. I don’t want to do that again so I’m trying something different on the wings. I basically stopped working on the model on Sunday because I didn’t want to mess with the tape anymore.

Battery & Charger

The battery and charger showed up today. I chose, a Thunder Power Pro-Lite 2100mah 3S pack that weighs in at 5oz. the ’3S’ part means thats its 3 cells in series, this is also written as 3S-1P to denote that its one bank of series cells with no other bank in parallel. 3S-2P would be 2 banks of 3 cells in series, joined in parallel, confused yet?

The charger I got is a Hyperion EOS 5i. I have about zero fear of taking things apart so I took a peak inside. It looks well built, the case is all aluminium and the buttons are sealed. There are 2 black heat conduits of a material I can’t identify that connect to the back plate of the charger to what I assume are mofsets (voltage regulators). There is some sort of thermal interface material between the conductor and the back plate. I didn’t want to break the interface in case it is a pad so I didn’t take the back plate off.

Removable input cables would have been nice. I could have used a different set to connect to a PSU and saved the alligator clips for charging from a field battery. I don’t like alligator clips or bare connectors on a cable, they make me nervous.

Weight Report

I will have a full weight report at the end of the build. The Instructions claim the final weight will be 12oz without the battery. Right now its up to 5.6 ounces. The running gear will add another 5oz so its going to be tight.

• Make sure you get the strapping to lay flat on your work surface before you apply it. It it wont lay lay by itself its going to have enough force to curl away from the foam.


• Find the middle of the strapping and crease it! This stuff doesn’t go around corners very well so you have to bend it where it turns at the centre of the wing..


• You need tape to hold it down, particularly if you use Polyurethane glue. However, you can remove the tape once the glue had dried. It won’t adhere well because there is no adhesive on the rest of the foam. You can then sand over the strapping area for a really smooth finish.


• Don’t forget to sand the tape.

I’m not sure Polyurethane is the best glue for this and it tends to push the strapping away from the foam as it cures. The tape I uses didn’t adhere well enough to keep it held down. On the underside of the wing I used too much glue and it bubbled up in some places. Luckily I caught it and pushed it back down before it cured that way.

By the time I did the fuselage I had it down. The only different with the fuse is that there are no channels cut into it to guide you. On the up side you can sandwich it with anything moderately heavy you have lying around to make a tight bond. I’m gonna play with this technique when I do the sport wing. I think with a bit of parchment paper and the wing saddles you could get perfect strapping tape application, more on that later.

I have actually been gearing up for this for a couple of weeks. I already have the radio (a Spektrum DX6), the motor and speed controller. The only bits still on the way are the battery and charger and they should be here by the weekend. Hopefully I’ll have the airplane built by the weekend.

The Magpie is a park flyer/trainer with a 46″ wing span (40″ for the sport wing) made from EPS and Depron. EPS is Styrofoam, like the cheap coolers you get at 7-11. Depron is a more finely textured foam, like that used in sign board or meat packing trays.

The manual (see a pdf copy here) recommends 5 Minute epoxy for bonding the foam parts together. I wasn’t too keen on using epoxy. I have used it in the past and it can be tricky. You have to mix it exactly 50/50 and with a 5 minute set time you have to work fast. It makes a very strong bond. Its also relatively heavy and weight doesn’t fly.

I looked for some alternatives and came up with Polyurethane glue in the form of Elmers Pro Bond / Ultimate. This stuff activates with water and can be cleaned up with soap and water before it sets (neat hu?). It foams and forms bubbles as it cures and tends to push the pieces you are gluing apart, not a good thing. As I had never used this kind of glue before I did 3 test pieces to see how it works. I did the first with too much glue and held it together with rubber bands. The second I used less glue and just pressed the foam blocks together. The third I used blue painters tape to hold the blocks and used even less glue.

The best results were with minimal glue and tape. The rubber bands bit into the EPS and twisted the blocks. The press fit blocks were pushed apart by the expanding foam. So use tape and use as little glue as possible. This stuff seems to set up stiff in about an hour and you probably have 15 mins of working time to set and tape the parts. The directions say to wait 24 hours for it to fully cure.

Enough about glue, on to construction.

The manual recommends cluing the wing halves together first. Doing the fuselage looked easier so I did that first. I used the painters tape to stick the cuttings from the taper on the rear fuselage back together. This make a sandwich and make everything uniform so when the two halves of the fuselage were glued and taped together they were as straight as possible.

I didn’t have a 44″ flat surface in my apartment to set up the wings on so I put my white board on the floor and covered the middle of it with Parchment Paper. Parchment paper is superior to wax paper in every way. Mosses himself couldn’t get from one side to the other. CA glue will actually bead up on it and refuse to set.

I did the slow fly wing first. Its a bit tricky to get the halves to meet up perfectly. I joined the bottom of the wing with lots of painters tape and then applied the glue to the joint. Then I flipped the wing upside down and placed it on a large tissue box so that the wing tips weren’t touching the ground. In that orientation gravity applies gently pressure to the bond to keep the parts together. The roll of tape and sanding block ad a little weight to the equation.

I’m going to let the parts cure overnight. Tomorrow, strapping tape…