Dynamic Review
 

Wingspan: 46" Length: 37" Wing area: 353 sq. in. Weight: 48 oz (43 with FAUP pack) Wing Loading: 19.5 oz/sq. ft. (17.5 with FAUP pack) Motor: Jeti Phasor 15/4 Prop: Graupner CAM 8x6 ESC: Jeti JES 40-3P  Battery: 8 Cells Sanyo 1900SCR & 1950 FAUP Radio: Hitec 555, Four HS-81 servos Available From: Hobby-Lobby

Introduction

The Dynamic is postitioned by Hobby Lobby as a "Hotliner".  Most of us think of a sailplane-like model, with a wing that is both fast and strong.  The Dynamic, however, is more of a "Sports-Hotliner" - being a traditional, low-wing style, including landing gear, but having a beautiful, straight, double-tapered semi-symetrical wing that would not be out of place on any sailplane-style hotliner! It's thickness and aspect ratio allow for slow, uneventful landings, but is also clean enough to allow this model to fly very fast for it's size and power level. The landing gear means hand-launches are not required, which can be a worry for some pilots, and resembling a more traditional "Sports" model, it attracts a lot of attention at the flying field by the "wet" flyers.

Kit Contents

Hobby-Lobby was kind enough to provide everything that would be needed to fly this review model - including not only the power system - motor, prop and spinner, ESC and battery - but also a Hitec 555 receiver and four Hitec HS-81 servos.   The only additional items required were hinges and hinge tape, glue, and the usual building tools.

Kit Contents Additional components provided

The kit I received was one of two samples that were sent to Hobby-Lobby.  The parts were all loose in a large box, no padding or additional packaging to prevent damage during shipping.  That said, the components are light and strong, and were all in good shape.  Note that every other kit I've ever purchased from Hobby-Lobby has been suitably packaged to prevent damage from shipping.  I don't think this box was even opened from the manufacturer before being sent to me.  There were no instructions either, although I did receive a copy of a plan of the completed model.

As can be seen from the pictures, the molded fuselage is very sleek, and the one-piece wing saves some time during assembly.  The control surfaces are covered and ready for assembly.  The underside of all flying surfaces, and the entire rudder, are provided with a deep red covering applied.  There is a nice sticker that adds detail to the wing.  The landing gear is one-piece fiberglass, and all hardware for the mounting of the wheels, as well as control linkages, was included. One item noticably missing was a firewal, as well as some sort of reinforcement for the landing gear.

Construction

I decided to keep plain white and red color scheme - although trim lines and details are nice additions, most full-scale aircraft are fairly plain.  The only painting I felt was necessary was to color the canopy black.  This was acomplished with some regular Krylon high-temperature matt black spray paint (the type used for touching up grills). I had it handy and, as the canopy was one removable piece, I simply laid it down on a piece of newspaper and added a few light coats.  Note you should always clean the fiberglass surface prior to painting, as there is often mold-release residue remaining on the parts that can prevent the paint from bonding to the surface.  The Hobby-Lobby demo model has some nice pin-strips on the wing and fuselage, but with the bulk of the model being plain white, you could create some very attractive color schemes if so desired.  I was not so ambitious, however!

Without instructions, I made up the assembly sequence as I went along.  I started with the landing gear, which would allow me to work on the model upright on the bench.  Drilling the fiberglass gear was simple, and the included hardware makes short work of attaching the wheels.  I then positioned the gear as shown on the plans, and drilled pilot holes to allow for securing bolts.  I was a little concerned at the lack of any reinforcement material (and none was indicated on the plans) for securing the landing gear to the fuselage.  I went ahead and simply bolted the gear in place, however, expecting this to cause a problem if the model was subjected to one of my typical hard landings!

Gear bolted directly to fuselage

The horizontal stablizer and elevator are simple balsa sheet, covered with a bright white covering on top, and red below.  The white covering is a good match to the fuselage.  There is a provided U-shaped joiner which links the two halves of the elevator together.  To ensure everything would stay in alignment, I actually joined the elevator halves to the stabilzer first, using lengths of 3M hinge tape on the top surface.  I then folded the elevator halves back onto the stabilizer, and marked where the ends of the U-shaped joiner touched the leading edge of each elevator half.  The holes are easily drilled with a small hand drill, and I like to put a drop of CA in the hole to help strengthen that area.  Once the CA had cured, I opened up the holes again by hand, then inserted the joiner into the elevator halves.  The whole process took about as much time as it did for me to describe here.  The slot which retains the horizontal stabilizer is molded into the fiberglass fuselage midway up the vertical stablizer, and is easily cut out with a sharp knife - although I went ahead and used a Dremel cutting wheel to speed the process.  This took only a few seconds, and a few swipes with the edge of a sanding block cleaned up the slot ready for installation of the stabilizer.  I had the presence of mind here, however, to pause and consider that I should probably wait until the wing was attached and square before glueing this component in place!

The wing has pre-drilled, reinforced holes at the suggested CG point, and supplied bolts pass through these holes into threaded holes molded into the side of the fuselage.  This meant it only took a second to attach the wing - there was no margin for adjustment here, which was fine, as everything lined up straight and true.  Besides the quality of the kit components themselves, small details like fit and alignment can make all the difference between a rapid, pleasant building experience, and many hours spent trying to repair poorly fabricated components.

Back to the horizontal stabilizer, it simply slots into place and is retained by whatever glue you prefer.  I like Elmer's Probond for bonding just about any material to fiberglass - the glue foams and expands as it cures, meaning it fills any uneven surfaces, but also requires very little adhesive to be applied.  The one drawback to probond is that it takes a few hours to cure, and an least an hour before the parts can be handled.  A quick check of the alignment of the stabilizer relative to the wing, a thin application of probond to the slot, and the stab was in place!  I had to let the adhesive cure, but no fear - I had a wing to work on!

The first step in preparing the wing is to glue the center portion of the trailing edge into place, which retains torque rods for the ailerons.  A narrow channel needs to be made in this filler piece, as well as the trailing edge of the wing panel, where the brass tubes that support the torque rods will rest.  I use a little grease on the rods to prevent them from binding to the tubes, wing or filler piece, and a little epoxy on the tubes before capturing them in place between the filler and wing trailing edge.  After joining these pieces with a little more epoxy, this filler piece is then further secured by some small pieces of matching covering material that are provided with the kit.  This was applied immediately, holding the parts in alignment while the epoxy cured.

With the torque rods in place, the ailerons need to be installed, leaving a small gap to ensure there is no fouling on the side of the fuselage or the filler piece - which happens to be about 1/8" wider than the fuselage at that point, so as long as it is centered, there will be no issue here.  The ailerons were covered to match the wing, and only require holes for the torque rods, and hinge installation.  I chose a set of Dubro pinned hinges for both the ailerons and the rudder, installing three on each aileron half, and three total on the rudder.  The holes were quickly drilled by hand again, reinforced with a drop of CA, and the alignment checked once again before slotting the wing and ailerons for the hinges.  My handy hinge slot cutter and centering adapter made short work of this chore, and a blob of probond in each hole and on each hinge before pressing into place meant these hinges were never coming out!  A small amount of grease along the moving surfaces of the hinges prevents any residual adhesive from bonding the hinge halves together.

The provided molded wing-tips are easy to install, as they simply slip over the tips of the wing panel, and with just about 1/8" overlap, they left a nice gap at the outer edge of each aileron.  A quick swipe of Probond again before installation, and the wing was almost complete!  I applied a little masking tape to hold the tips in place while I worked on the servo installtion.

Aileron servos installed

The aileron servo installation is acomplished by simply glueing two short hardwood sticks to the sides of the provided aileron mount hole, appropriately spaced to allow the servos to drop in place.  They are pre-drilled for the mount screws, and then the servos are secured in place.  The remained of the aileron control linkages took no time to install - a simple z-bend on the servo side, and a brass clevis on the other, which latch onto a couple screw-on control horns that screw onto the torque rods we installed earlier.   The wing was nowcomplete!  I used a Deans 4-pin polarized connector to split the leads between the receiver and aileron servos, simplifying hookup when installing the wing onto the fuselage.  I prefer a single, robust connector, rather than using the standard servo connectors, as I do not feel these hold up all that well to repeated connections over time.

Tailwheel bushing Tailwheel secured to rudder

When the adhesive holding the horizontal stab had cured, it was time to install the rudder and tailwheel.  The rudder is simply hinged to a couple of wooden inserts that you sand to shape and fit into the trailing edge of the vertical stablizer (which is integral to the fuselage).  These were bonded in place with Probond.  Three pinned hinges were used to attach the rudder - again secured with probond.  The tailwheel needs a small bushing sunk into the lower edge of the fuselage.  I used a small piece of brass tubing that was a good fit to the provided tailwheel support wire.  Probond came in handy here again (no, I don't work for Elmer's!), and the tailwheel was quickly assembled from components provided.

Although there was no firewall reinforcement included, and the plans seem to show the motor being bolted directly to the fiberglass fuselage, I prefer to reinforce this area with a ply mount cut to shape.  I cut a disc of plywood, and drilled it to accept the motor mount bolts and shaft.  The ply reinforcement was mounted to the rear of the molded firewall, and glued in place with (you guessed it) ProBond.  The Jeti Phasor only requires a couple of bolts to hold it securely in place, and along with washers to spread the load against the fiberglass.  The motor dropped in place, and it was time to start working on the prop assembly.  Due to the shape of the cutout, the supplied spinner will not seat in the aluminum backplate with the high-pitch propeller provided, a Graupner CAM 8x6".  To resolve this, I had to reshape the spinner cutouts to suit the blades.  This took just a minute with a dremel cutting wheel, but this should be done carefully to ensure the spinner remains in balance.  I also had to leave off the washer that usually rests between the propeller hub and retaining bolt, again in order to get the very sleek spinner to seat correctly.  The provided spinner used a clamp-style collet adapter, which makes it very easy to install and secure the prop to the motor shaft.

Cut spinner to fit Leave off washer

As the connectors are provided installed on both the motor and ESC, these components simply plug together, the beauty of sensorless technology means you only have to reverse two wires if the propeller spins in the wrong direction.  The power system installation was complete, and the model really started to look goodwith the wing and propeller installed!  I had to test the power system, of course, to see what kind of performance I could expect.  A short blast with the provided 8x1900SCR pack gave me almost 30A current draw, for a little under 270W of power!  Total weight looked to be around 3lbs, it would have about 90W/lb static, not bad for a small pattern-style model.

The canopy was already painted as described earlier, but it still needed to be secured to the model.  A provided steel pin allows the front of the canopy to key into the fuselage - a quick hole drilled from the wing seat area below allows perfect alignment of these pieces, and a drop of ProBond secures the pin in the canopy.  The rear of the canopy is held in place by a nice little spring-loaded retractable pin. This is screwed to the inside of the fuselage with the pin extending through a slot, into another hole in the canopy.  Alignment of the latch and holes was quite tricky, but it was worth the effort to get it right, as the canopy was held very tightly and securely in place, yet removal for setup or battery installation is, quite lterally, a snap!

The next step is to install aileron and elevator control horns onto the surfaces, and the associated linkages and servos.  The standard 1/2-sized control horns are installed in minutes, by drilling a couple of holes through each surface to allow the horn halves to be bolted together.  Always ensure the holes in the control horns align with the hinge axis.  The control linkages are wire-reinforced plastic rods that ride inside another plastic sheath.  These enter the fuselage through two molded, streamlined access points, and are then secured to the inside of the fuselage to prevent bowing, and control surface slop.  This I accomplished with - take a guess - more probond!  I have to say, however, that securing these rods with this adhesive is so much simpler than any other type I have used (i.e. Epoxy) as the glue expands significantly while curing, and forms around the sheaths to help form a much more secure bond.  With the control linkages in place, I only needed to attach a couple of appropriately-spaced hardwood rails for the servos, and as I used probond again here, they both needed to cure overnight.  The servos are then simply screwed to the rails, and the linkages trimmed and installed onto the servo arms - I soldered brass clevises to the control-horn ends of the wire linkages, but used simple z-bends to attach to the servo arms.

Elevator and Rudder servos Receiver is mounted below

With the servos installed, I came up with a suitable location for the receiver - just behind and below the elevator and rudder servos - and used some industrial velcro to hold this in place. The last, most important step was to check the CG with a suitable battery.  The provided 8x1900SCR pack slotted down over the landing gear quite nicely, and I was pleasantly surprised to find that the model balanced at the suggested CG point with the battery about 1" back from the motor.  I used some ProBond again to hold the velcro hooks to the fuselage floor.  I also installed a velcro strap in order to prevent the battery from being able to move up away from the floor of the fuselage, and thereby seperating from the velcro that held it in place.

Flying

With the model fully assembled and ready to fly, it actually took me some time to get out to the field to test it.  Unfortunately, the first attempt met with failure, when after all the usual preflight inspections, I noticed just before takeoff that the elevator looked out of trim.  I adjusted the trim, but the elevator did not move.  I retrieved the model from the runway, and found that the elevator was no longer connected to the servo!  It felt as though the linkage was still connected, but there was no movement at the control surface when the servo was moved.  After closer inspection, I realized the metal core of the plastic control rod had broken at some point internally, and was allowing the surface to pull away from the rod, eliminating any control of the surface!  I was glad I discovered this BEFORE takeoff!

Back in the workshop, I found that the rudder linkages was also damaged.  I removed both control linkages, pulled out the metal core, coated them with probond and inserted them back into the plastic.  It was pretty messy, but the next morning when the adhesive had cured, I pulled as hard as a could on each end of the rods, and could not unseat them.  I was satisfied they would do the job, so they were re-installed, and the model was agian ready for a test flight.

The next attempt was a little more destructive!  As I had not flown in some time, I had a more competant pilot handle the takeoff for me, but before the model reached flying speed, it veered a little to the left (we had a crosswind on our narrow, elevated runway) and just touched the grass at the edge of the strip.  This ripped the landing gear completely out of the fuselage.  Now this was something I had expected when there was no ply reinforcement provided for the landing gear installation, so I was not unhappy that it had happened, but dissapointed that we would not - yet again - get to fly this model!

Damaged gear mount points A little CA, glass, and wood Glass in place, ready for reinforcement block

Although the damage may look significnat, the repair was actually very simple - a piece of masking tape inside the fuselage allowed the broken pieces of fiberglass to be carefully replaced, then secured with CA.  A block of hardwood was carefully shaped to match the fuselage, and a heavy layer of glass applied between it and the damaged area.  These were all attached with probond, and left to cure overnight.

Reinforcement block in place Block drilled and threaded Nylon bolts now secure gear

The new block was drilled to match the existing holes in the ear, and then tapped to match some sturdy 3/16" nylon bolts, and the landing gear was now much more securely attached to the fuselage!  With these modifications, and some flights at a local fun-fly to get 'back in the groove', I was ready to fly the Dynamic for the first time.  It's debut would happen at the Southeast Electric Flight Festival, in June of 2003.

With all of the bugs worked out, the first flight was as simple and uneventful as one could wish for.  Even with the small provided wheels, the model had ample power to quickly get up to flying speed from the grass strip.  I let her climb out without raising the nose, allowing the airspeed to increase to where I was confident I would have no problems if I initiated a turn or climb.  She flew like a dream - reducing throttle and flying slow circuits overhead while I applied a couple of notches of trim, and then back to full power to see what she could do!  It's always hard to judge the speed of a model, but I would guess about 70mph straight and level, with a significant increase in a dive - you can hear the air rushing over the landing gear at high speed!  From full-power level flight, she climbs very well - not vertical, but you can perform 300' loops with ease, and very nice push-overs, hammerheads, etc.  I always like a lot of control throw, and she snaps and rolls very nicely when suitably provoked.  Rolls are not quite axial, but the CG could probably go back a touch.  She doesn't lose much airspeed on final, so you're going to want to lose a lot on downwind and make those last two turns carefully - either that, or dial in some spoilerons to prevent her from floating past you into the next county!  It's not hard to get her down at your feet, however, with some practice.

Ready to fly!

After a few very enjoyable flights on this model, I picked up some Sanyo 1950FAUP cells - these are reported to have as much power as CP1700's, but a little more duration and - the best part - they weigh only 1.1oz/cell.  This meant an 8-cell pack would shed almost 5oz off the ready-to-fly weight of this model!  I made up a pack and headed out to the field, to see what was in store.  I was not dissapointed - power and performance were both up, and she leaps off the ground at a lower - almost uncomfortably lower - airspeed.  I prefer to keep her down until the speed picks up, then let her rise off slowy; but on grass, the drag on the mail wheels requires that you hold some up elevator to prevent the nose from pitching forward (and striking the prop), which encourages her to get airborne in a hurry.  This happens so quickly, however, that you shouldn't worry about it being a problem - if she leaps in the air, just let her fly straight and level for a couple of seconds no matter what may be ahead, until you get up enough airspeed to safely turn or climb as needed.  She has enough power to acomplish this in a very short distance.  What can I say - she looks like she wants to go fly just sitting on the bench; you can't blame her for being so enthusiastic!

Conclusion

The Dynamic is a beatiful model, with very nicely constucted components, that goes together easily and flies as good as she looks.  The lack of instructions and the few overlooked items (landing gear reinforcement and motor mount) as well as couple of defective parts (control linkages) have been addressed by the distributor, and are easily atrributed to the "beta" status of the kit I received.  The model certainly performs as advertised, and I would not hesitate to recommend this model as a good entry into hotliners for those comfortable with a sports model, for example, or a good entry into pattern and sport flying for those used to hotliner or pylon style models.  I fall into the latter category, and I can say that this model has the capabilities to let me practice some basic sports and pattern manaeuevers, but having compact dimensions that will mean it will make it out to the field on a regular basis.  It also draws a lot of attention when flown!

I'm here if anyone wants to discuss this. I love this model, especially on 8 1950FAUP's!
..a

1950FAUP's
 

Hey, Andy, nice report. Have you established a point where you would no longer consider using the 1950FAUP's (Amps-wise)? Tex.

I've heard they're good for 70A in short bursts. I have no idea how hard I can push them for sport flying.. but I intend to find out! :)
..a

Idle thoughts ...

Will it take 10 x 1950's?

With a little extra effort on the behalf of the manufacturers, it would either make a nice low parts count kit or a decent ARF. No instructions in the kit and losing the gear before take-off suggests someone, somewhere needs to do better ...

Coming uncovered would make life easier in the long run - fitting 'naked' wood tailfeathers being easier than ditto for covered ones springs to mine here.

Otherwise, looks fast standing still.

D

It would take 10x1950, for sure. I don't think the motor would, though? What do you think?

Good thoughts on the kit. I discussed with HL last week during a trip there - theirs still had the LG bolted to the fuse as I tried first - they must have a great field and a careful pilot! :) I'm not quite so accomplished..
..a

Andy
It was great seeing you last week. It is also great to see the review of the Dynamic. Thanks for the good work!

Well I just got my Dynamic as a christmas gift and started working on it the other night, what a great looking model! I got the whole recommended set-up so I'll be powering it with my new (and first brushless) Jeti 15/4. Routed out the air intake and exhaust scoops tonight (did you guys do this on yours?) and drilled out the required holes for the motor. I noticed that because the front of the Jeti motor is not completely flat (has a small 1/8" protrusion where the bearing seats on the front) the motor doesn't actually fit flush against the fire wall, I was just a little worried that when I tightened down the mount screws that it would possibly bend out the glass in front, but I guess it's pretty strong as mine has the updated plywood reinforcement already glued in place which I was happy to see.....one less thing to do! But overall I think it will go together nicely. Anyone else building and/or flying a Dynamic besides Andy? I'm amazed this model isn't more popular as the price isn't outragous at all.

Scott

Make the hole where the shaft comes thru large enough to accept that raised portion of the motor, otherwise it won't be straight..
Yes, I opened up the air ducts.

How is your landing gear secured? Please pay careful attention to that part of my review..
..a

Thanks Andy, I will enlarge the hole, I was originally going to do this but thought it was getting a little too close to the mounting screw holes, looks like I will use all 4 screws instead of 2. As I said my kit has the reinforced ply on the fire wall but they seem to have decided against going with a reinforcement for the gear, the glass looks a little thicker in that area but no wood. I really like your idea of using nylon bolts and threading the wood so I will do the same. I'm also trying to think of a nice paint scheme for the fuse, if I do I will post a pic.

Scott

Do reinforce the gear mount points. I can't believe this area has not been improved.

As to the motor mount - if the ply is thick enough, just remove that material around the shaft, at an angle (use a dremel) so that you don't have to worry about the mount holes on the front. Even if you go too far, you can use small washers on the front side to prevent the screws from pulling thru..
..a

Well I haven't been able to do much on the Dynamic but at least I got it painted, I had so many ideas and looked at too many pictures of other design schemes that I couldn't decide, so I just grabbed the pin-striping tape and got creative. The hardest thing about this design was getting it exactly the same on the other side. Was initially going to use an airbrush but went with regular canned spray paint, it came out great though. Sorry for the muddy pics, my digi-cam died and all I had is my web cam!

Scott

the tail

Wow.. nice paint job! I haven't even bothered with mine, but now I have inspiration..
.a.

b-e-a-u-t-i-f-u-l..............