Park Scale Models Whim Series SE5a – “The Rupert”

This is a newbie’s build review of the Whim Series SE5a from Zeke Brubaker’s Park Scale Models (“PSM”).  The Whim Series kits are easy-build kits that are a lot of fun to build and would be a great kit for your first balsa build. 

After building several foam board Flitetest airplanes, I wanted to retry my hand at building a balsa wood airplane.  The last balsa plane I built was a “Trooper” glider 40 years ago.  Unfortunately, I do not have a workshop or work space where I can lay out plans and materials on a building board. 

One day, while cruising the “New Items” section of the HobbyKing USA Warehouse website, I saw the PSM Whim Series kits.  These kits have laser cut parts, claim ease of assembly and “… no need to build over plans.”  At only US$30.99, and after a little online research, I figured, “Why not,” and submitted my order for the SE5a.

PSM Whim Series kits are laser kit, meaning that most of the parts to be assembled have already been cut from the sheet by a computer-controlled laser.  The balsa sheets are of good quality and are not warped.  A few tabs, approximately 1 mm wide, hold the part to the sheets.  You cut the tabs with a sharp razor and the part falls out, just like the Flitetest series of foamie kits.  Gone are the days of old kits where the part was merely printed on the balsa sheet and inevitably broke in two as you tried to cut it out.  You also get a plywood firewall, a plywood sheet with control horns and the interplane struts, a carbon fiber rod and a well written instruction sheet (NB:  The PSM website says that instructions are not provided in the kit but are available on the website.).

The package arrived in a sturdy box, well packed with bubble wrap and air bubble cushioning.  The kit arrived fully intact with no damage to the exterior of the box or the very thin balsa sheets.  I laid out the kit sheets, the electronics and other parts, and started assembling the kit.  While the instructions are well written, there are a few minor points missing in the SE5a instructions so I recommend also downloading the P-51C instructions from PSM for useful information on hardware, build tips and other build items.

Construction begins with building the fuselage.  The parts are clearly labeled on the sheet.

After laminating the F2 and F3 bulkheads, you test fit the bulkheads, battery tray and firewall to the fuselage right side.  PSM’s slot and tab construction makes very easy the alignment of the respective parts.  Better yet, the parts fit correctly with little to no need for sanding or trimming.  A strip of spare balsa cut from excess from the sheets is glued to the inside rear of both fuselage sides for extra support.

At this point, I felt it would be a good idea to install the 1811 2000kv brushless motor to the firewall before installing the firewall into the thin fuselage sides.  The top front of the firewall is clearly marked and the top motor mounting hole is pre-drilled with reference lines etched into the wood for the other motor mounting screws.  Once you have installed the motor and are satisfied with the test fittings, you glue the firewall, bulkheads and battery tray together, and then into the fuselage side.

Next step is to attach the fuselage left side.  Again, the slot and tab construction, and laser cutting makes it very easy to build a squared fuselage.  You will also notice that the slots for the firewall angle the firewall down and to the right for proper motor thrust alignment.

You then attach the fuselage tops and the bottom.  If you have built a Flitetest airplane fuselage, you will recognize the overlapping tab construction that again makes construction easy while ensuring a squared fuselage.  To ease connection, I connected the ESC and motor before gluing in the fuselage top front, while the fuselage remained open.  Glued into place, the fuselage is surprising strong for having such thin sides.  Final fuselage assembly including adding 4 triangles around the bottom of the F2 bulkhead to strengthen further the landing strut attach points.  Here, I made a slight change to the plans and added a nose front made from poster board to attach decals of the SE5a signature front radiators.

After the fuselage, you then assemble the wings.  The top and bottom wings follow a similar 3 piece construction.  For both, the center section consists of 2 spars and 2 wing ribs, both with interlocking cutouts to ensure square assembly.  The only difference in construction is that the top wing center section is covered on top with a thin balsa covering for strength.  Using CA glue with a kicker is almost a must when it comes attaching the ribs to the top covering unless you want to spend a long time pinching the leading and trailing edges to the rubs.

For both set of wings, the construction uses 2 ribs on each side but no spar for the outer wings.  Rather, the wing consists of a sheet of balsa wood with cut-outs to lighten the wing.  You mark the locations for the 2 ribs and then glue them to the underside of the balsa wing, creating the under-cambered wing.  Again, CA glue and a kicker makes this a much quicker build process.

Lastly, you glue the port and starboard wings to the center section.  For the top wing, you align the leading edges and glue the wing tops to the 2 spars and the exposed half of the center section ribs.  Alignment and fit were very good.  The bottom wing follows the same procedure except you align the rear of the wing cutout with the rear of the center section rib.

After measuring and cutting the cabane struts, and landing gear struts and axle from the included carbon fiber rod, I measured and cut a piece of carbon fiber to join the two elevator halves.  I secured the elevator to the horizontal stabilizer and the rudder to the vertical stabilizer with Blenderm tape before covering.

At this point, the instructions recommend covering the disassembled sections of the model.  While you can use ultralight, heat-activated covering films like Solite, I chose to go “Old School” with tissue paper.  I never liked the plastic look of the films, especially on a WWI warbird.  Uhu Stic glue made attaching the covering very easy, which was then shrunk with a misting of 50% water and 50% alcohol.  The underside of both wings are not covered to retain an under-camber airfoil.  I also made and added on the the engine valve covers and exhaust pipe (scrap balsa; hollow plastic coffee stirrer painted black), port-side Vickers machine gun and breach cover (hollow plastic coffee stirrer painted black; poster board covered with tissue) and headrest (poster board covered with tissue).  Once finished and dried, I secured homemade decals using the Uhu Stic Glue and then sealed the tissue with two light coatings of Krylon clear matte spray paint.

Assembly of the plane is the next step.  I first test fit the cabane struts into the gaps in the F2 and F3 bulkheads.  The front cabane struts easily fit into the gaps but I had a little difficulty fitting the rear cabane struts, probably due to a building error.  However, I was able to work the rear struts into the designed gaps.

After test fitting the struts, I attached the lower wing to the fuselage.  The two wing spars fit snugly into cutouts at the bottom of the fuselage and my wing perfectly aligned with the fuselage.  The plans also recommend adding side bracing to the inside of the fuselage at the wing juncture for added strength (I was able to find sufficient scrap balsa wood in the sheets to cut out braces with the grain perpendicular to the grain of the fuselage, for extra strength.).  After gluing the wing to the fuselage and gluing in the braces, I used clothespins to pinch the inner wing rib, fuselage side and braces together while drying to ensure a strong bond.

After opening up the holes in the included control horns so that the control rods would fit, I installed the control horns into the pre-cut slots in the rudder and elevator.  I next installed the horizontal stabilizer and elevator into the slot in the rear of the fuselage.  There is a tab at the front of the stabilizer that helps you align it perpendicular to the fuselage.  If needed, you can twist the fuselage rear top and bottom to get the horizontal stabilizer parallel to the bottom wing but, fortunately, mine perfectly fit, a credit to good model design.  

I then installed the vertical stabilizer and rudder, and lower vertical fin to the fuselage.  There are slots in the top and bottom of the fuselage, and tabs on the stabilizer and fin that make installation and alignment easy.

Next came installing the top wing, always the most difficult part of a biplane.  However, if you have built a Baby Blender, you can handle this.  To connect the top wing, Park Scale Models uses 4 carbon fiber rods (provided in the kit) as cabane struts with ply wood forms for the interplane struts.  The carbon fiber rods fit into pre-cut cutouts in the fuselage.  They also provide a jig to help you align the incidence of the wing.  I think the jig is supposed to fit on top of the fuselage but my front cabane struts – cut according to the diagram on the plans – were too short.  Again, possibly a building error but as a work around, I positioned the jig to the underside of the top wing just outside the fuselage and aligned the jig bottom parallel to the fuselage top (I would recommend marking your cabane struts where they are supposed to fit into the fuselage as drawn of the plans, hopefully to avoid my error.)  You are then supposed to trim any excess from the cabane struts but the thought of a whirling Dremel cutting disk near thin balsa wings was too much to attempt.  Connecting the interplane struts were easy as cut outs in the top and bottom wings are pre-cut.    

Next came installation of the landing gear.  The landing also uses carbon fiber rods that also fit into pre-cut cutouts on the forward bulkhead.  The axle is also a carbon fiber rod, which I tack glued before lashing it to the landing gear struts with nylon thread and securing with CA glue.  Dubro 1.23” micro wheels finished off the landing gear, poster board glued to the outside of the wheel to make the look like fabric covered spoke wheels used in WWI.  There is no rear landing gear strut provided so I made one by splitting in half a wooden coffee stir stick, painting it black, cutting it to length and then gluing it in place.

At this point, I installed the 3.7 gram servos.  The plans do not show where the servos should be placed but other articles note to place them as close to the front as possible.  A photo of the SE5a built by the designer showed the servos just forward of the rear bottom wing spar so I glued my servos in the same location.  For added strength, I had not cut the bottom wing spars where they cross the open fuselage underside but the servos still fit perfectly in the space.  If I was to build Rupert again, I would place the servos one bay forward, behind the firewall for better weight distribution.  A Du-Bro Micro Push Rod System (Item # 847) provided the push rods, pushrod housings, Micro E/Z Links and Mini E/Z Connectors. 

Lastly, I added the final detail touches:  “Rupert” – a 1:16 pilot from Easy Built free-flight models (item # P09) held in place with two 3/16” magnets from RadioShack – one glued to the back bulkhead and one to Rupert’s back – so I can remove him if necessary; and a scratch built Lewis machine gun and foster mount made from scrap balsa and control rod wire, also held to the top wing by 3/16” magnets.

Now for the important stuff:

Specifications & electronics:

                Controls:  3-channel (throttle, elevator and rudder)

                Motor:  Hextronic 18-11 2000kv Brushless Outrunner motor (10g)

                ESC:  HobbyKing 6A ESC 0.5A UBEC

                Battery:  Zippy Flightmax 350mAh 2S 20 C battery

                Propeller:  GWS EP5043 5x4.3 electric propeller (recommended by Park Scale Models)

                Wingspan:  20.5 in (521 mm)

                Length:  15.75 in (400 mm)

                Wing area:  151 in² (97,419 mm²)

                All up Weight:  Target:  3.7 oz. (106 g)

                                        As built:  3.77oz (106.8 g) flying weight

                                                       3.84 oz. / 108.8 g with Lewis gun

                Wing loading:  Target:  3.5 oz./ ft² (10.9 g/dm²)

                                       As built AUW:  3.6 oz./ft² (11 g/dm²)

Costs to build:  Total costs runs about the same as a Flyzone micro-SE5a:

• Park Scale Models Whim Series SE5a (HobbyKing USA Warehouse only) http://www.hobbyking.com/hobbyking/store/__64239__Park_Scale_Models_Whim_Series_SE5_a_Balsa_Kit_US_Warehouse_.html?strSearch=se5 US$ 30.99;

(also available from Park Scale Models: http://www.parkscalemodels.com/shop/item.aspx?itemid=42; and,

in the UK: http://www.micronradiocontrol.co.uk/parkscale_whim.html#ps-se5a);

• Hextronic 18-11 2000kv Brushless Outrunner motor (10g), package deal price: http://www.hobbyking.com/hobbyking/store/__64239__Park_Scale_Models_Whim_Series_SE5_a_Balsa_Kit_US_Warehouse_.html?strSearch=se5 US$ 8.71;
• HobbyKing 6A ESC 0.5A UBEC, package deal price: http://www.hobbyking.com/hobbyking/store/__64239__Park_Scale_Models_Whim_Series_SE5_a_Balsa_Kit_US_Warehouse_.html?strSearch=se5  US$ 6.81;
• GWS EP5043 5x4.3 electric propeller [US$0.75 each X2] http://gwsprops.com/direct_drive.htm US$ 1.50;
• 2mm Gold Connectors 10 pairs (20pc) [for motor / ESC connection] http://www.hobbyking.com/hobbyking/store/__30663__2mm_Gold_Connectors_10_pairs_20pc_US_Warehouse_.html?strSearch=2mm%20conn US$ 2.43;
• Female JST battery pigtail 12cm length (10pcs/bag) [for ESC to battery connection] http://www.hobbyking.com/hobbyking/store/__50017__Female_JST_battery_pigtail_12cm_length_10pcs_bag_US_Warehouse_.html US$ 2.07;
• Turnigy 1370A Servo 3.7 g / 0.4kg/.10sec X 2, package deal price of US$2.84 each: http://www.hobbyking.com/hobbyking/store/__64239__Park_Scale_Models_Whim_Series_SE5_a_Balsa_Kit_US_Warehouse_.html?strSearch=se5 US$ 5.68;
• Zippy Flightmax 350mAh 2S 20 C battery X2 [US$3.30 each] http://www.hobbyking.com/hobbyking/store/__20654__ZIPPY_Flightmax_350mAh_2S_20C_USA_Warehouse_.html US$ 6.60;
• Du-Bro Micro Push Rod System (Item # 847) http://shop.dubro.com/p/micro-push-rod-system-qty-pkg-2 US$ 5.72;
• Du-Bro 1.23” Micro Sport Wheels (Item # 123MS) http://shop.dubro.com/p/1-23-micro-sport-wheels US$ 2.36;
• Easy Built Lite Olive Drab tissue [Figure 2 sheets for safety at US$0.65 per sheet] http://www.easybuiltmodels.com/ebl.htm US$ 1.30; and
• Easy Built 1:16 pilot, item # P09 (“Rupert”) http://www.easybuiltmodels.com/spare.htm US$ 4.92.

TOTAL, excluding shipping:  US$ 79.09.

Flight Report:

I maidened the Rupert on a fairly calm day.  The PSM SE5a flies very well in a calm with good stability due to the dihedral in the wings, and plenty of power with a brushless motor putting out around 4 oz. (113.4 g) of thrust (something lacking in the Flyzone SE5a).  The 3-channel controls with no ailerons takes a little relearning after flying 4-channel planes, but she was well behaved with only a little trimming needed.

However, with an All Up Weight of only 3.77 oz. (106.8 g) and a wing loading of only 3.6 oz./ft² (11 g/dm²), the Rupert is not a big fan of wind, as I found out when a gust suddenly appeared.  She handles wind fairly well for such a light plane but she much prefers the calm.

As I fly solo, there is no flight video.  However, there is a flight video of the companion Fokker D VII on the Park Scale Models’ web page, http://www.parkscalemodels.com/shop/item.aspx?itemid=43, which was pretty examplary of my flight.

Conclusion: 

Is this a good first airplane? No.  Although she is light and stable, the balsa is very thin and, therefore, inherently fragile.  Better to learn on an EPO, high-wing, pusher trainer that better absorbs the inevitable crashes.  Is this a good second or third airplane?  Absolutely yes.

Is this a good first balsa-build kit?  Unquestionably, yes.  The balsa sheets were of high quality, as was the laser cutting of the parts, and arrived intact and not warped.  Assembly was easy with well-fitting parts and straightforward, clear instructions.  The cost is roughly on par with a Flyzone 14.3 in (363 mm) Micro SE5a, but flies much better and is one you can have pride in having built yourself. 

If you do not want to deal with attaching a top wing, there are several monoplane models from which to choose, including a Piper Cub, a P-51C Mustang and an F4U Corsair.  I recommend these kits to a first-time builder or an experienced builder who is looking for a fun, low-cost and easy-to-build kit.

Tally-ho!