It was a perfect flying day today, so I went out for my first flights of the season. I brought my trusty ParkZone T-28 and bored a bunch of holes in the sky. My first flight of the day was definitely a bit shaky, but I settled in quickly. I certainly don’t consider myself to be an accomplished pilot, but by my last flight of the day, I started getting a little more daring with loops and rolls. I need more practice on the simulator so I can learn how to tie maneuvers together.
Made some progress over the weekend on the Hog Bipe. The top wing is close to being completed. So far, building everything stock and according to plans.
No major issues so far and only one minor issue. The kit only comes with a single piece of 1/6″ x 3″ x 48′ sheeting to be used to sheet the front portion of the top wing. The piece was badly bowed such that I needed to trim it down to just a bit over 2-3/4″ to get a straight and true edges front and back. Fortunately, this was just enough to give me a good glue joint to the top spar.
The top sheeting was also a bit tricky to glue down properly. I started at the left edge and glued the front of the sheeting to the leading edger, one bay at a time, using medium CA and kicker. Once the front of the sheeting was attached, I wet it down with Windex to soften and help it to curve, and then using a toothpick spread TightBond wood glue on top of the ribs and along the spar. I like using wood glue rather than CA for attaching the sheeting to the ribs, especially considering the number of ribs involved in this long wing panel, as it has a longer work time and allows you to fuss and adjust a bit.
I then start at one end and press the sheeting down into the glue on the rib and on then the spar, pinning it as I go. I work one bay at a time and am careful not to let the sheeting buckle as I go. After removing the wing from the building board, I added a fillet of wood glue between the ribs, the spar, the leading edger and the sheeting on the inside.
After letting the glue dry thoroughly, I pulled the wing off the board and after adding the maple mounting blocks, added the bottom sheeting. I used a slightly different technique this time. Here, I preformed the curved shape by wetting with Windex and gently bending the sheeting around the rounded corner of my workbench. It is not critical that the shape of the sheeting be perfect, just reasonably close.
I then applied wood glue to all ribs, the inside of the leading edge and spar and then dropped the preformed sheeting onto the glue. I then pinned the sheeting to the leading edge, and worked the sheeting back by pressing to the rib and spar just like top sheeting. On one side, I worked the leading edge to spar one bay at a time. Although this worked well, I ended up with a slight gap (about 1/32″) between the front of the sheeting and the leading edge on the last two bays on the outboard edge. I ended up filling it in with a bit scrap. On the other side, I pinned the sheeting to the leading edge first, then went back to pin down to the ribs and spar. This worked much better.
That’s all for now.
My SSE project is just about done. All I have left to do is final assembly of the main landing gear and final installation of the electronics (receiver, EEC, BEC). I also need to order a set of batteries so I can do a final balance.
I polished up the main gear bracket and clear coated it yesterday. I was unhappy with the look of the clear coat though, as the polished aluminum seemed to lose much of its luster under it. The only reason for the clear coat was to protect the shine, so I stripped it off with a bit of acetone and buffed the aluminum back out again. This time, I put on a simple coat of carnauba wax to protect the aluminum finish.
I also painted the wheel pants white. I was happy with how they came out, until I came back to check on them and found a hair settled into the paint on one. I will see how it looks after the paint fully dries, but I am likely to do a little light sanding and add one more coat of paint to both before final assembly.
I have not been out flying yet this season and I want to get some stick time on some of my old standby birds before trying a maiden on the SSE, so for now, I will move onto my next build.
With my SSE project nearing completion, I cleared off some bench space and kicked off my next build, a Sig Hog Bipe. I will build it as a “fantasy scale” early Army Air Corps plane with the blue fuselage and yellow wings color scheme. I am also thinking about some sort of custom cowl instead of the traditional Sig style open nose.
Of course I am planning an electric conversion. Sig calls for 6.5 – 7.5 lb all up weight and a 0.60 sized glow motor. For electric motor sizing, I’ll round up to an even 8 lbs and plan on 150 watts per lb, which will put me right at 1200 watts. I want to keep with 6S batteries (22.2v), which will then need to draw about 54 amps.
I like to have the motor on had when I start the build, so I can use the motor mount as a template to drill mounting holes in the firewall before assembling the firewall into the fuselage. I am leaning towards a Cobra C-4130-12 motor. Their site includes a prop chart which lists about 1120 watts with a 13×6.5 prop and just a tick under 1200 watts with a 13×8. The 13×8 prop (drawing 54 amps), is just a bit over the 52 amp continuous limit for this motor, so as long as I am not flying max throttle all the time, I should be in a safe zone.
Battery capacity may be an issue though. I am hoping to use the same batteries here as my SSE. For the SSE, I want to keep to 4000 mAh maximum in order to keep to a reasonable weight. But 4000 mAh may not give me enough flying time for a heavier plane drawing higher current. As always, there are trade-offs with electric set ups, and I need to digest on this a bit before I make my final selection.
Since I have not finalized motor selection, I will get started on the wing panels now. Given my slow build rate, by the time I am done there, I will have settled on a motor and have it in hand. I will be back traveling again this week, so I won’t even be able to start until the week after, though.
I made some good progress on the SSE. The last bit of covering has been finished, and the blue trim has been added. I am real happy with the color scheme, but the covering job itself I only give a barely passing grade to. Several dust specks are trapped under the covering, some minor wrinkles here and there, some scratches and rash, some dents in the balsa, and lots of places where (despite my best efforts) more wood grain is showing than I had hoped for. Oh well, I continue to learn and I am confident my next covering job will be better!
I finished off the cockpit with some black electrical tape for combing. I opted to forgo adding a pilot, mainly because I did not have one handy. The canopy was trimmed and installed. It’s not perfect, it was a little scratched to begin with, and I glued it on slightly off center. I intentionally left the back of the canopy a little long so I could trim to a clean fit. I trimmed close with a cutoff wheel on my Dremel and hand sanded the rest. While I got a nice clean fit, some of the sanding dust sneaked its way under the canopy, so short of cutting the whole thing apart, there is no way to get it out!
The motor has been installed. All servos have been installed, all control surfaces are hinged and installed, and the control horns installed. The kit supplied control horns install with #2 pan head screws. The sharp points of the screws stick up past the control horn backing plate, so I carefully ground them down with the Dremel.
The stab braces, which I assembled and polished some time back, were painted with clear and installed.
I am replacing the kit provided tail wheel assembly with a Sullivan Products one as it’s a bit more rugged. I installed the required t-nuts to attach the mounting bracket during fuselage construction, but I need to file a small notch in the bracket to clear the stab braces. Instead of a wheel collet, I decided to try silver soldering a pair of #2 washers to retain the tail wheel to the axle (the kit instructions recommend this as an option). This was the first time I tried this, but it turned out to be quite easy (no pictures of the intermediate steps though).
So, what’s left:
- Paint the wheel pants
- Final polish and clear cote the aluminum landing gear
- Landing gear installation
- Pushrod installation
- ESC and BEC Installation
- Receiver installation
- Set control throws
Back at the start of this adventure, I really agonized over the motor selection. After going back and forth on RCGroups (http://www.rcgroups.com/forums/showthread.php?t=1988642), I ended up going with a 6S configuration and motor that will let me pull about 900 watts with an 11×7 prop, or around 1000 watts with a 12×6. Overall, this might be a bit more than I need, but how often do you hear complaints about having too much power?
The down side, though, is that I am coming in a bit heavy. Without the battery, I am pushing 4 lbs. A 6S battery will likely add another 20 oz or so, so all up flying weight is likely to be around 5.25+ lbs. About 1/2 a pound over Sig’s target weight. I’ll have at least 160 watts per pound (good), and a wing loading of 19.7 oz/sq. ft. and a wing cube loading of 9.5. On the high side of acceptable for a sport plane, and I don’t plan to fly3D, so I am guessing I will be OK.
I haven’t bought my batteries yet, but mockups with some weights are showing me a bit nose heavy – which would be a first for me! I am fairly certain that I will be able to get the balance right by adjusting the battery pack location, but worse case, I’m sure that any weight I might need to add to the tail would be trivial.
Not too much new progress. I got the right wing panel and the right aileron covered. One more aileron to go and I will be done with covering. Why leave just one aileron? Well, I found myself rushing with the right one, and predictably I am less than satisfies with the results. I have just enough red covering material for the remaining aileron, so I can’t recover the right one (and I have nothing left for mistakes on the left one), so I decided to call it quits for today.
I haven’t had much build time lately, but was able to get back into the workshop this weekend. I am close to being done with covering the SSE. I have to say that covering continues to be my least favorite part of building.
I covered the rear half of the fuselage bottom and sides with white Monokote and all went well, but the turtle deck turned out to be a bit of a problem. It took me three tries to get it right, and in the process of ripping off the covering on the first two tries, I ended up denting and dinging up the balsa at the top of the fuselage sides. It’s hard to see in the picture, but unfortunately is quite noticeable in person. I’ll add some blue accent trim later, hopeful that will hide the dents some.
What looks like wrinkles in the picture below are actually reflections.
The rest of the fuselage and empennage covering went fairly smoothly. Despite my best efforts to vacuum and clean every surface (including the use of a tack cloth), I did end up getting a few dust specks under the covering. Ugh!!
I got one wing done before deciding to call it quits for the day. So I’m down to one wing and the ailerons left to go.
Got a few hours of building time this weekend and I started covering the SSE. I really dread covering, so I tend to put it off and find other things to do. I am at the point on the SSE where I ran out of other things, so covering begins.
This will be my third covering job and my first time working with Monokte as opposed to AeroLITE (Stevens Aero branded version of Solite) which I used on Stella and my SA RV-4. I had two rolls of Monokote (one white and one red) lying around that I was intending to use on my SIG LT-40 (I lost interest in that project once I got past the trainer stage of flying and never did get the plane covered).
I’ve read all the flame wars of Ultacote vs. Monokote and bought the Monokote on the advice of a friend who was helping to get started in RC. So far, I am finding Monokote to actually be a bit easier to work with than AeroLITE. Mainly, this is because it is a bit thicker making it easier to handle and less prone to burn-through when shrinking. It also does not fold over and stick to itself the way AeroLITE does. It clearly is a lot heavier than AeroLITE and would not be appropriate on a small park flyer. I have not tired any compound curves yet, which most seem to claim is Monokote’s biggest weakness (at leas as claimed by the Ultracote crowd!).
So far, I have the rudder and elevator covered in red and the rear half of the fuse bottom in white.
I’m giving my covering job a passing grade so far, but barely. Most of my problems are related to surface prep. I spent way too much time sanding and filling (see my Lessons Learned post), but as you can see, it really did not pay off. Simply put, I need to develop a lighter touch when working with balsa during the construction phase. This includes not only a lighter touch when sanding, but also more care in handling the pieces prior to covering.
I tend to be a bit too critical of my own work, but I also look at every project for learning opportunities and for things I can do better next time!
I continue to plod slowly long on my SSE build. I have the basic construction completed and I am just about ready to start covering and final assembly. While I still have not learned how to get my builds done as quickly as a lot of the other guys I see posting on RC sites, I have learned quite a few lessons along the way.
Lesson 1: Be Selective with Kit Supplied Balsa
The 1/16″ sheeting supplied with the kit for the wing D-Tubes (the sheeted portion of the wing ahead of the spar) turned out to be a bit marginal, with a large knot running through several sheets in the same place. I ignored this and used them anyway, only to find that those knots caused a large local dimple to form between the wing ribs. Note this was not a “starved horse” kind of sagging you sometimes can get between the ribs, but more of a dimple localized around the knot. Being the fussy builder that I am, I decided to fill the dimple with a bit of balsa filler. This worked great on one wing panel, but not so good on the second, leading to Lesson 2.
Lesson 2: Know When To Stop Fussing
When fussing with the dimple on the second wing panel, I kept filling and sanding and filling and sanding trying to get the surface to blend smooth. All this filling and sanding lead me to sand the surrounding sheeting too thin, and I ended up poking a hole through the balsa. Ughh! I originally tried to patch just the local area, but this lead to another cycle of fussing. So in the end, I gave up and just carefully cut the sheeting off the outer two bays and replaced it with new wood.
The final product is acceptable, but I do have a but of starved horse look between the ribs. This is a result of too much sanding trying to get the surface smooth. which leads to Lesson 3.
Lesson 3: Less Is More When Sanding
When it comes to sanding, always remember that less is more. You can always go back later and take another swipe or two, when you’re really convinced that you need it, but you can’t put back material (at least not easily). Even though I was careful to use a long flat bar, too much sanding leads to thinning of material directly over the ribs producing a wavy look in my wings.
I also ran into a problem when sanding out the fuselage hatch. When blending the front of the hatch smooth, I was not paying enough attention to the “other end” of the sanding bar, which in turn lead to a nasty groove being cut near the back of the hatch from the back corner of the sanding bar. This lead to another cycle of filling, sanding, and fussing (see Lesson 2), which again resulted in material being sanded too thin. In this case, I plated on some 1/16″ balsa scraps to build material back up, and then blended it smooth. You can see below that I misted on a very light coat of gray primer to help guide my sanding (i.e.; the primer is left behind in low spots).
Once again, what I ended up with a less than perfect, but hopefully acceptable (we’ll see after the covering is applied). Which leads to the most important lesson learned yet …
Lesson 4: Any Mistake Can Be Fixed
A good friend who helped me to get started in RC once told me: “Don’t worry if you make a mistake, any mistake can be fixed”. I repeat that mantra to myself all the time while I am building, especially when things start to go bad. Mistakes are part of the building process. We all make them, even the best builders out there. Mistakes can be fixed and they can be a learning opportunities for the future. Sometimes they cost us some money (if a new part or material needs to purchased), but mostly they just impact time (and maybe a little pride) and it is part of the overall experience. Remember that this is a hobby and we do this for fun, so don’t fret if something goes wrong, just fix it!
One of my projects from last summer was an attempt at a foamy scratch building with a Fan Trainer EDF built from Dollar Tree foam board. I patterned it after the 150% scaled up version of the plans found in this build thread: http://www.rcgroups.com/forums/showthread.php?t=426281.
This was my first attempt at both EDF and at building with foam. The building process went well and I kind of enjoyed working with foam.
The total investment in foam was about $5 (including scrap and re-work). I powered it with a Detrum 70mm Fan combo from HobbyPartz.com which includes the fan, motor, ESC, and servos for under $50. All in, with batteries, and a 4 channel receiver, total investment was under $100.
Unfortunately, it did not survive its maiden flight. The wings were simply not stiff enough and fluttered badly. Apply enough power to keep the plane flying, and the wings flapped like a hummingbird. Back off the power, and there was virtually no control. I ended up lawn-darting and disintegrating everything from the wings forward (sorry, no picture of the damage).
Oh well, nothing ventured nothing gained. The electronics and fan escaped unscathed, so the total loss was under $10 (and a little bit of pride). I have a few ideas for how to use the fan and other bits from this attempt in a new creation!