In light of the disappointing entry in the CO2/electric class at the 2022 scale indoor nats, I vowed to build something to enter in 2023.
The Bristol Superfreighter is a subject I have long wanted to model, but it is impractical for rubber. A span of 36" was chosen so that I could
swing a pair of 5" props without having to cheat and move the engine nacelles outboard. Using a pair of Voodoo 25 motors (combined thrust 50 grams)
this would mean a target weight of 100 grams, so I would have to build it light.
As it turned out I wasn't able to enter the model at the Nats as I couldn't get it trimmed in time. When the photo above was taken, a few details had yet to be added (including the cockpit windows) but the plan was to do that after trimming. As it turned out, the model got damaged a couple of times and is currently awaiting repair.
the fuselage is a box using 3/32" sq. longerons with 1/16" formers above and below. There are just two 1/16" sq. stringers top and bottom
with the corners covered with light 1/32" sheet. I pre-formed the sheet to the required curve using the technique described by Tom Hallman in this YouTube video,
(though I used a larger diameter rod).
The multi-spar wing uses ribs that are flat between the spars so that the ribs don't show through the tissue. The section between the leading edge
and front spar is curved, but covered with light 1/32" sheet.
The wing was covered before assembling to the fuselage. The nacelles were added, the motors installed and all the wiring connected and
guided out below the centre section. Access to the motors is by removing the tops of the cowlings, as shown. Note the considerable amount of side thrust
incorporated, as found necessary in previous electric models.
Here is the wing now assembled to the fuselage and faired in - the fuselage top was the last part of the model to be covered.
The tailplane and fin have a symmetrical section with flats sanded
between the leading edge, spars and trailing edge, again to stop the ribs showing through the tissue.
The cockpit section is removable for access to the Zombie controller and 200 mAh battery. After this photo was taken, I moved the battery box back one bay
as the model had come out nose-heavy.
The model is airbrushed with Xtracolor enamels and all the cheatlines are cut from painted decal sheet, as are the large BAF titles. Final weight came out at a shade under 100 grams. The two Voodoo 25 motors had plenty of power to fly the model, but initial test flights outdoors showed a tendency for the left turn to tighten up as the power ran down resulting in a couple of heavy arrivals. The join between the cowlings and the nacelles proved a weak spot, and I have had to glue them back on twice now. This has also lead to wires being separated and I have had to remove sections of tissue to make repairs. I will have another go though - maybe it will work better as an outdoor model than an indoor one. I'll keep you informed.
DPC Models Airco D.H.5
Well, this wasn't in my carefully curated model building plan.....
I was fortunate enough to win a DPC Models De Havilland D.H.5 kit at one of our local indoor meetings, took it home,
opened it, and before I knew what I was doing it was on the building board. It's laser cut, so progress has was rapid.
Span is only 16", but due to the fairly low-aspect wings, it's quite a
substantial model. It's a quirky plane with its octagonal fuselage and reverse stagger.
The structure was as as per kit apart from some extra gussets, plus I cut the main undercarriage V-struts from 1/64" ply then faced them with 1/32" balsa both sides and sanded
to a steamlined section. Wire pins were inserted at the top to engage with holes in local fuselage sheeting. Covering is all Martin Dilly Japanese tissue, steam shrunk and given two coats of banana oil.
The model was finished with Xtracolor enamels, which dry glossy, allowing decals to be easily applied. All markings were cut from painted decal sheet and applied (in layers for the roundels - first a white disc, then the blue and red sections). A final misted coat of Tamiya matt varnish from a rattle can gave a nice, hard-wearing matt finish. Power is two loops of 3/32" rubber with a 6" IGRA plastic prop.
I had a go at trimming the model in our small school hall and nobody was more surprised than me that it coped with the necesarily tight circuits without any trouble at all. I didn't need any gurney tabs or tip weight to keep the left wing up in the turn. It seems the reverse stagger layout in conjuction with the type's generous dihedral leads to a very stable aircraft. For proof, see the video of a test flight below (thanks Lurk!)
1/20th scale De Havilland D.H.5 for electric power
One thing leads to another....
So, I ordered the Windsock Datafile on the D.H.5, read it through and became increasingly attracted to the idea of doing an open electric model as a backup for the 2023 scale indoor Nats, in case I couldn't get the Superfreighter to circle safely in the hall. To clinch the
deal, I had a brand new Voodoo 15 motor, matching cell and a spare Zombie controller in the drawer just looking for a home.
Some rough calculations indicated that I stood a fighting chance of getting a 1/20th model with a wingspan of 15.3" out at close to 30 grams.
Richard Crossley advised me that substituting a 5" prop for the supplied 4" folding one would actually boost performance a touch, so that's what I did.
Also, it looks more realistic, being close to scale size.
I drew up the plan from scratch based on the Windsock Datafile - the only intentional change being a tiny increase in dihedral. Rib spacing is scale and there are no fewer than 85 riblets.
The area in front of the cockpit is quite complex - not helped by the offset machine gun. Access to the motor and controller is by removing the upper cowling.
Short-nosed WW1 models like this lend thenselves very well to electric power as you can put all the
weight where you need it, i.e. right at the front.
It was quite a squeeze getting the controller and 90 mAh cell alongside the motor and still be able to fit
on the upper cowling, but I just about managed it.
The yellow tape is present to try and stop the wires flexing
too much, especially while changing the battery, hence avoiding fatigue fractures.
The model was covered in white Esaki tissue (I still have a few sheets left) apart from the tail surfaces, where I used Martin Dilly's Japanese tissue
due its less severe shinkage. After steam shrinking, the components were given two brushed coats of banana oil.
I used Xtracolor P.C.10 enamel for the upper surfaces and their “clear doped linen” for underneath and am very happy with the colours (though it's a shame all the schemes are rather dull). They are both gloss finish to help decal application, so after all the markings are on, you have to spray over a mist of matt varnish (I used a Tamiya rattle can). Roundels are built up from cut-out discs of painted decal film, as normal for me. I couldn’t live without my Olfa compass cutter! Rigging is fishing nylon. One problem with having the cowling tightly packed with the motor, battery and controller was that there was simply no room for a 3D dummy engine, so I used a printed paper version instead. It looks fine from a distance, though is guaranteed to lose me a few scale marks.
This model was actually finished before the DPC kit as I was rushing to get it finished in time for the 2023 Indoor Nats. Sadly I was unable to get a qualifying flight, as even with the motor turned up to maximum power, the model would not climb much above head height from a hand launch. Thus I never got a qualifying flight - frustrating, as the model looked nice and stable, even with its scale sized tailplane. My fault for building it too heavy.
After the Nats, I removed the motor and replaced it with a Voodoo 25, which weighs exactly the same and has an identical motor mount. Importantly, it can deliver 10 grams more thrust. Test flights at the May Old Warden meeting were successful with this power unit and the model cruised around nicely at well below maximum power.
Peanut scale Heinkel He 45
The story behind this one is a little unusual. My next peanut scale model was going to be a Blackburn Dart, but during a clear out of my cupboards and drawers prior to
moving to a new modelling den at the other end of the house I found these old wing ribs and wingtip laminations. I had absolutely no idea what model they were for!
Trawling through the many reference folders on the computer I eventually discovered one dedicated to the Heinkel He 45 with a partly drawn peanut scale plan created back in 2008.
It seemed a shame to waste all that work, so construction commenced!
Here are the bones ready for covering. To save weight I didn't do separate ailerons or elevators on this model, but hinged the
rudder to aid trimming. Weight at this stage was 6.8 grams.
Weight after covering and applying a coat of banana oil was 8.9 grams.
Thw components were all airbrushed using Xtracolor enamels and the decals applied before assembly. All markings are cut from painted decal sheet apart
from the fin logo which is a laser printed decal. As the Xtracolor enamels are gloss (which makes decal application easy) a final thin coat of Tamiya matt varnish
was applied using a rattle can.
The distinctive exhaust pipes were a bit of a challenge. My final solution was to laminate them from strips of thin balsa around a form to give the correct shape and when dry, sanded them carefully to a round cross section. The functional rigging is fishing nylon.
Initial trim flights were made with a loop of 3/32" rubber installed and after adding a little nose weight it looked very promising, circling left within the confines of the hall. Only snag was that the rubber cross section looked a little small - even on 1000 winds the model wouldn't go above head height. Next time out I'll go up to 0.105" rubber to give it a bit more power. Weight came out at 18 grams all-up, which is about the same as my Blackburn Ripon.
Ray Malmstrom Bi-Star
The Trinity flyers had organised a informal competition for Ray Malmstrom models for December 2023, so I picked through his many designs
to find something suitable to build for it. Taking advantage of the “re-sizing
allowed” rule, I decided to go on a bit of a nostalgia trip and build an 80% Bi-
Star. The original was published in December 1973 as one of those free plans
stapled into the centre of Aeromodeller. I would have been 16 at the time and
built it straight away. I think it flew OK but I don’t remember any details.
The original span was 17.5”, which becomes a handy 14.5” when scaled to 80%.
I reduced wood sizes more or less proportionally. For example, 1/20”
sheet fuselage sides instead of 1/16”, tail surfaces 1 mm sheet and upper wing
spars now 1/16” x 1/32” etc. I covered using
Dilly Japanese tissue and then airbrushed a thin coat of Tamiya white
acrylic before adding some decoration.
The registration G-AZMF is the same one Ray used on his prototype. Lettering
was done using laser printed decals and the blue and red markings are cut
from painted decal sheet (as usual)
The finished model was a touch over 19g with rubber on board. Initial
hops in the garden showed it was nose-heavy so instead of adding trim tabs to the
tailplane I glued a strip of 1/16" sq. all the way along the top of the tailplane trailing
edge which did the trick (not added when this photo was taken). Indoors it flies very nicely on a loop of 1/8" rubber.