Tag Archives: ARF

Almost Ready to Fly models.

Final Tweaks To H9 Cub ARF

Well I planned to spend an hour or so with the final tweaks to the H9 Cub ARF this weekend, but it turned into quite a bit more work than I thought. I started by checking the balance with my Vanessa balancing rig. If you have never used a Vanessa rig, it is a simple tool for finding the center of gravity for any plane (I’ll post a bit more about my setup and its use in the future).

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I turns out that I needed to shift the battery pack as far forward as possible to get close to balance. This shouldn’t have been a surprise since the motor and ESC combined together are lighter than the glow engine this plane was designed for. The battery more than makes up for this, but in the location I originally placed it, much of that mass was behind the firewall.

No problem, since there is plenty of room in the cowl to slide the pack forward, EXCEPT… I now need to turn the pack around and face the wires towards the back as there is no way to reach the plug inside the cowl. No problem, EXCEPT… the battery wires from the ESC don’t quite reach far enough to connect with the battery. So, now everything has to come apart so that I can add about 1-1/2 inches to the ESC battery wires.

I do realize that is typically never a good idea to lengthen the battery to ESC wires, but 1-1/2 inches should not be much of a problem and the total wire length from ESC solder point to battery connection at the pack is still only about 8-1/2 inches (anything over 12 inches typically requires additional capacitors to be added).

Everything back together and I try the balance again. It is much better, but still about 5/16 behind the ideal location.  Note: The forward mark in the photo below is the ideal location at 3-1/4 inches behind the leading edge. The mark behind it represents where the plumb bob should point to mark that spot (compensating for the fact that it is offset by 1/2 of the dowel thickness that the plumb bob string is hanging from).

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It will take about 5 oz or so of additional weight to get the balance on the money. But since the plane is already coming in overweight by about 11 oz, I think I will call this close enough. Note, I was a bit surprised by how much overweight the plane is until I discovered that the combined weight of the battery, motor, ESC are about 8 oz heavier than a glow engine sized for this plane (although I would have that at least some of that would have been offset by eliminating the fuel tank, the receiver battery, and the throttle servo though).

So, after the better part of a Saturday afternoon (and a bit of Sunday morning), the balance is finally done. Now just a few minutes to set the control throws. The elevator goes quick enough, as does the rudder (although it is not possible to get the full travel called for without hitting the elevator, reconfirming that this older ARF is not at all up to today’s standards).

The ailerons however are another story. The ailerons must be set with a differential throw to prevent severe adverse yaw tendency inherent to both full size as well as model Cubs, with a greater down aileron throw vs up. No problem, I installed the servo arms at an offset angle (as called for in the manual) which will build in the differential. In addition, I am using a 6 channel receiver with a separate channel for each aileron, allowing me to fine tune the travel for each. EXCEPT… at full down aileron throw, the pushrods are binding against the mounting hatch (did I mention that the quality of this ARF).

This turned into another lengthy trial and error project of trimming the aileron hatch, adjusting the initial angle of the servo arms, and adjusting the travel limits separately for up and down motion for each aileron. Nothing extraordinary complicated, but time time consuming. You can see in the photo below the notch that needed to be cut in the hatch to allow full pushrod travel without binding.

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At this point, I am calling it done! I’ll give here a good once over to make sure everything is secure and all fasteners are tightened up before taking here out for a maiden, but I am definitely getting tired of fussing with this ARF (I guess I got what I paid for!).

Hanger 9 80” Cub ARF

Several years back, I picked up and older Hanger 9 80” Cub ARF. It was unassembled, and all the parts were there, but in truth, it could best be called fair condition. The covering was badly wrinkled, the plastic windscreen was a bit dented, and the fiberglass cowl had a crack in the bottom. But the price was right, so I thought I’d give it go.

Compared to newer ARFs, this was quite crude. The control surface needed to be hinged, the wing mounting dowels and bolts needed to be drilled, and all the clear parts cut out, trimmed, and installed. The dummy engine bits were just white vacuum formed plastic and they too needed to be cut, trimmed, glued to the cowl, and painted. Pushrods needed to be assembled from balsa dowels and piano wire, and even the tailwheel wire needed to be bent to shape from straight stock piano wire.

I started picking away at it as a fill in project, and (of course) converted it to electric power, using a Turnigy G46.

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There are some scale details I have yet to add (like non-functional wing struts), but she is finally about ready to fly. Not too much to look at, but I am hoping she will be a good flyer.

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Looking forward to some warmer (and drier) weather to try her out!

Rebel Ready To Fly Again

The guys at Motion RC took care of me after my Rebel crash and provided me with $50 store credit to offset damages, which more than covered the cost of a new fuselage kit.

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Everything else was salvageable, so this was the only replacement part necessary for the plane itself.  For piece of mind, I will scrap the battery back from the crash since it appears a bit damaged. So in the end, my only out-of-pocket cost is under $30. Not bad.

Reassembly was easy. The fuselage kit comes complete with plastic for the nose gear, a new canopy, tail and nose cones, and even servo extension cables pre-installed, so this was mostly a bolt together job. The nose gear strut and the pushrod connecting the nose gear steering servo were both slightly bent, but easy to straighten.

After reconnecting the ESC to the fan, I wrapped the connections tightly with electrical tape. That should keep them together.

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Since I had everything out on the bench, I decided to replace the “T” style battery connecter with an EC3 (I don’t the way the “T” connectors spark when you mate them). The EC3 was tight fit through opening in the fuselage, but with a little coaxing, it squeezed through.

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Of course, this meant I had to pull back the pre-installed servo extensions to make room. I was a little concerned about getting the throttle connector and servo extensions back through this tiny hole, but using a length of nylon pushrod sleeving, it was easy to fish them through.

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Everything else then was just bolted/glued in place. Since there was a small crack in the original canopy, I decided to use the new one provided with the fuselage kit. Like last time, I carved a small bit of foam from the underside of the canopy to allow for battery clearance. The plane rebalanced with about 1.3 oz in the nose (like last time).

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For good measure, I will re-verify all my control throws, but there is no reason to expect anything has changed since the wing and tail were undamaged and no changes were made to the electronics. Here she is ready to re-maiden.

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Now I just need the weather to cooperate!

Crashed My Freewing Rebel Today :(

Well after a very successful maiden last week, I had a very unsuccessful third flight today. After about 2 minutes in the air this morning, the EDF quit in flight and I ended up “lawn-darting” her in.

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The battery had plenty of charge left so it wasn’t a brown out due to a low battery. I could still move the control surfaces, so I know it wasn’t due to loss of radio signal. I assumed either the motor fried or something went wrong with the ESC.

After getting her home and doing a bit of disassembly, I discovered that the motor to ESC wires had come loose!!! How does this happen in flight? They must have been loose from the factory.

Unfortunately, the connection is hidden when the fan unit is installed and I never thought to remove the fan to check the connections. After-all, I never had anything go wrong on bench tests before her first flight. It just never occurred to me to even think about checking the ESC connections.

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Well lesson learned! From now on, I will be double-checking all connections and mechanical joints on any ARF I happen to buy.

To make matters worse, I had a new 4S 3000 mAh pack (only used once before) in the plane that got a bit crunched too. The pack is deformed and feels a bit squishy (not like its puffed), so I think I am going to trash the pack. It’s not worth the $37 to risk fire with a physically damaged pack.

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I sent pictures and a description of what happened to Motion RC (where I bought the plane). Maybe they will take pity on me and help me out here. If not, I can pick up a new fuselage for $50 and get her back in the air without too much trouble.

Maidened My Freewing Rebel EDF Today

My wife bought me the Freewing Rebel EDF for Christmas this past year. I have been slowly building up the courage to get her into the air and finally took the plunge today. I had two great flights despite all my nerves and shaking hands – thank god for expo!

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She’s definitely faster than anything else I’ve flown, but really stable and well behaved. Take-offs were uneventful, except she feels a bit sluggish until it picks up speed, and needs a bit more take-off roll than any of my prop planes. In the air, she was very predictable and responsive on low rates. I didn’t do anything fancy, but never felt like I was out of control, and at full throttle, she was tearing up the sky! With half flaps, landings are a breeze, really no harder than my old T-28. I did not try full flaps. Flight times are a bit short, I am getting about 3-1/2 to 4 minutes with a 3000 mAh 4S battery, with ending capacity at about 20%.

This was my first Freewing plane, and overall, I am very impressed with the quality. I did end up fussing with the elevator a bit. The stock setup had two pushrods, one for each elevator side inserted into a single hole in the servo arm. While I am sure that this would work fine, I was having a hard time getting both sides of the elevator to travel identically and could only het about 10mm total travel (vs the 16mm recommended).

To address this, I made up a new custom pushrod set by silver soldering two wires together and replacing the clevis links with Du-BRO micro links . I also slightly trimmed the foam ahead of the servo to provide clearance for the pushrods. Most of the control surfaces on this plane use low friction nylon hinges, but the elevator is a standard foam hinge, and felt a bit stiff. So, for peace of mind, I replaced the stock servo with Hitec metal gear servo. Finally, I used a slightly longer servo arm to get a bit more travel. All together, these small changes got the elevator travel up to the full 16mm, aligned, and moving smoothly.

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The battery compartment is a very tight fit. The receiver and wires fit, just barely, behind the battery cavity. I needed to trim a small amount of foam from the front in order to fit the pack without mashing the battery wires.

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With the 3000 mAh battery, the plane needed about 1-1/2 oz of weight in the nose to balance. Before gluing on the nose cone, I cut a small hole in the nose, then mixed some lead shot into a bit of 30 minute epoxy and “pouring” it into the hole.

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The only other fussing required was getting the aileron throws set properly. The right aileron had about 3-4mm more travel than the left. Since there are no empty spots on the 6 channel receiver, there is no choice but to join the servos on a “Y” connector. There is no way to trim one servo separately from the other. I’m not sure if the problem is with the servo, or (more likely) with the position of the control horns relative to the hinge line, but to fix the issue, I simply moved the right aileron pushrod to the outer hole on the control horn, and left the left in the middle hole. Travel is now aligned to within 1-2mm.

I probably am fussing a bit more than needed, but fussing is what I do!

I also got in a bunch of flights with my trusty ParkZone F4F today. This continues to be my no-fuss, no-muss plane. Like their tagline says “Just Fly”.

On the other end of the spectrum is my E-flite Hurricane. This is my “repair after every flight” plane. I had one fairly good flight with her today, but landed a bit hard and pulled the right landing gear mount out of the foam (again). No damage to the foam and, in truth, this is working the way it is supposed to (easier to glue the mount back into the foam than it is to repair a broken wing!).