Simon Chaddock

Thee are many variables to answer this question. Obviously keeping within the specification limits of the motor, ESC and battery is paramount but thereafter even with the same prop type (IC, electric or slow fly) and the same diameter and pitch but of different manufacture may not give exactly the same result. A basic Wattmeter measurement should prevent wrecking the motor but like most things related to aerodynamics there is no simple "best" prop/motor combination as the choice also depends on the design of the plane and to some degree on how the individual pilot wants it to perform.

Looking at that very neatly made plane some things stand out. It has no dihedral so no natural roll stability, no incidence between wing and tail plane (decalage) so no natural pitch stability and the tail plane is small on a short fuselage. All this suggest it will rely heavily on the electronic stability to maintain controlled flight. I may be wrong as after all a quad is not aerodynamically stable and the "electronics" certainly work for them. The question is whether wing mounted control surfaces will act with the same degree of response as the direct power control to the rotor motors in a quad? I sincerely hope my concern proves unjustified.

It does seem a bit odd that all 5 cells have failed to exactly the same voltage. The final check I would make is using a sufficiently sensitive digital meter check via the balance lead that the cell voltages are indeed what the charger is saying. If the digital meter agrees with the charger it would confirm that the problem is with the LiPo and not something odd with the charger. You might then feel more justified in having to replace what is quite an expensive item. 😉

shepeiro I am a little puzzled by some of the aerodynamics. In the front view above the rear of the wing struts are at right angles to the airflow. This will create a significant amount of drag. A wing strut is normally as stream lined as possible as are any struts in the airstream. Is the fuselage intended to be covered in any way? Those two formers creating the wing supports will also create a horrible amount of drag. I appreciate your wings are just 3mm foam but as a biplane there is a simple option to greatly increase their stiffness by using cross brace rigging indeed the original use of a biplane was primarily for this reason as it creates a light & rigid box structure. The wing struts then become simple compression members and are best made of wood. The Handley Page V1500 bomber of WW1 demonstrates how a flimsy looking big span biplane wing could support a fuselage, engines, fuel and bomb load totalling over 12 tons. For your light weight plane I would suggest that the foam wings would be quite adequate when braced with say monofilament nylon fishing line and at the same time allowing the drag producing foam elements at right angles to the airflow to be removed. As an example this huge (by your stands) 1260mm span and heavy (466g) biplane has foam wings that rely almost entirely on the monofilament nylon line "rigging" for rigidity. The wing struts are balsa The wing itself only has to be rigid enough to carry the loads on the short sections beyond the struts. Note that although made from 3mm foam its wings have a true aerofoil section. I would hope that you will be able to at least sand a radius on the leading and trailing edges of your "plank" wing to improve the aerodynamics a bit. 😉 I also note your are proposing using ailerons on both wings. This may make such a small and light plane ever so twitchy in roll.

Surely the full size Optica is a ducted fan. In theory it should be a good design to "electrify" however from what I have seen not all the EDF installations are that good with inappropriate inlet and exhaust duct areas resulting from the cockpit restricting the inlet and a big flat 6 positioned in the middle of the exhaust. In my view a conventional layout EDF does not fit particularly well in the available space. 😉 Just my own observations.

An interesting design but unless I am missing something those wing struts will create a serious amount of drag as will the fuselage unless it is going to be tissue(?) covered. As a biplane even basic cross rigging (nylon monofilament line) would provide all the wing stiffness you would ever need with no other reinforcing required. The biplane configuration was originally selected not primarily for extra wing area but simply as a way of creating a very strong wire braced box structure. By your standards this huge (1260mm span) and heavy (465g) all sheet foam Antonov AN2 has no reinforcing in the wings and relies almost entirely on nylon line scale rigging for wing stiffness. Note its wing has a proper aerofoil section. It would likely pay to sand at least a rounded leading and trailing edge on your 3mm plank wing.

The Deagostini looks favourite. I could find no Diablo manufacturer only quite a big turbine jet kit called Diablo by CARF models that are manufactured in Thailand with distributers worlwide.. I would guess the unusual nose intake is somebodies way of hiding the exposed cylinder head on the Deagostini.

Nigel Some 25 years ago I hand swung a Gipsy Major in a Tiger Moth many times and that 78" prop looks enormous when you are standing close in front of it. At least the starting "impulse" magneto has slightly delayed timing to reduce the likely hood of a back fire ripping the prop out of your hands. Technique is everything. .

I note the "Gipsy" Laser 200 goes the right way round, clockwise when viewed from the front, and thus matches the scale offset cowling air intake. . A rare combination or is that just a "show" prop?

Oh! dear. You might need a rain coat next week.

Don't forget the brushless motor will need a brushless ESC. You could simply select a brushless motor that is recommended to turn the same size prop as the original 480 with the same voltage battery. The brushless will be quite a bit lighter so it may require some internal adjustment of the battery position to maintain the CG.

With the continued fine and calm weather I managed an early morning flight with the Super Cub still on its 1000mAh 2s of 37 minutes 17 seconds. This duration gives an average current consumption of just 1.8A or about 14W. However being so light it means a slightly less impressive 26W/lb. This is aA figure well above that I achieved with the plane designed for endurance. It achieved a figure of just 8W/lb! Obviously the Super Cub needs more power, actually 3 times, to overcome its relatively "draggy" airframe.

A very nice day so I took the opportunity to fly a bit of an odd ball. Looks like a simple pylon pusher and I suppose it is but it has quite quite sophisticated aerodynamics. A 60" Depron wing and a well streamlined 3D printed pod and pylon. The ESC is in a ducted channel in the pylon. With 333W available through its 11x7 prop for an all up of 853g (1.88 lbs) means 177W/lb although even that is not really stressing the 6000mAh 3s LiPo in the nose. It glides very nicely too. Only its second flight but of just 10 minutes as a firm landing damaged the nose cone. The flight used very little of the battery capacity suggesting it should manage at least an hour of "cruise".

I suppose to anyone intending to build such a "twin boom" plane that the booms have a small section so are pretty delicate when compared to a conventional jet with a rear fuselage that carries a tail pipe. For the Vampire/Venom in particular in a crash if the booms are too strong they simply pull out of the wing. It thus becomes a choice as to whether boom or wing is the easiest to repair. 😉 My booms are just hollow Depron so I chose the boom repair option and at the same time saved tail weight. An important consideration as the inlet duct efficiency is compromised if the EDF has to be placed well forward in the fuselage for CG reasons. Note my EDF is virtually at the back of the duct favouring a gently sweeping inlet configuration. By contrast on the full size Venom due to the length of the DH Ghost turbojet the inlet configuration was rather restricted but then it was not an EDF where the inlet is critical.

I will resurrect this very old (2013!) thread as my sub 250g 40" Super Cub is still flying! It actually weighs 242g and its weight is "writ large" on the wing! On a very calm day a week ago I flew it with a "good" 1000mAh 2s and managed 22 minutes. I stopped because there were some noticeable gusts causing it to end up going backwards! On landing the cells showed 3.85V at rest so a bit longer should be possible, maybe 30 minutes? Just need one of those rare in the UK really calm days. Still not bad for an 11 year old super light Depron job. As an aside on another web site they started a STOL challenge that required a take off and landing within a very limited distance. Both of which my Super Cub can easily achieve BUT it had to do it carrying a "payload" of 200g. I then realised this would virtually double its flying weight. I know it is structurally strong enough to carry such a weight but I fear for the resulting STOL performance. Oh well perhaps next time.

It is worth remembering that with a foaming LW-PLA filament the final bead properties are a function of both temperature and flow rate. In some types of print 250 degrees and a 50% flow work well giving a full 0.8mm wall thickness, on others 230 degrees and a 45% flow gives a thinner 0.6mm wall but the bead is a bit stronger as it leaves the nozzle so is less likely to leave holes on a complex print. Like all things 3D printing there are lots of compromises.

frank I think your original post said it was "geared brushed". Any chance you could use the old gear box & prop? Although a direct drive with a suitable kV motor will be rather more efficient.

Frank I am not sure you can interpret a kV from the number of magnets and coils but if the original motor was geared then you are going to need a pretty low kV motor for an ungeared substitute. You will need to examine the motor specs to find one that is happy to turn an appropriate diam and pitch prop at the chosen power (Watts). You will likely find a suitable out runner will be quite a bit more powerful and lighter than the original geared brushless. My own experience substituting a brushless out runner for for an ungeared 480 brushed whilst retaining the same prop and voltage gave a 25% increase in max Watts coupled with a 40% reduction on motor weight.

If the financial investors predictions are correct the tariffs in their present form will not last that long but in the meantime everybody suffers.

This shows the rather cramped installation of the ESC, Rx and battery. The final result all painted. Not perfect but not too bad.

It a bit like software updates on a PC. They happen but how often are they followed by another update just a week later presumably "curing" something that the previous update created! My Spektrum DX6i is in the state it was 10 years ago when I got it second hand. No software updates for me!

andy I used to use UHU POR it is foam safe but has a problem particularly when used for planking as it does not ever set "rock" hard. The result is a POR glued joint joint will not sand properly smooth. This is bound to be a requirement when using multiple planks to create 3 dimensional surfaces. The best solution I have found is CIA Technicqll Polyvinyl Adhesive. It "holds" fairly quickly but does take 12 hours to set rock hard. They make a range but the one in the yellow tubes is transparent, XPS foam safe and sets hard. It is available on Ebay. I hope this helps.

I built the new nose back to a former in the undamaged part of the fuselage however as this was behind the bifurcated inlet. although this would make the join simple it would also mean parts of the inlet ducting would have to be reprinted and a large area of skin cut away. Upon reflection I decided to repair the damaged inlet ducting using flat bits of PLA sheet printed for the purpose. Although this would mean the duct would not have aa smooth a surface as the original from over lapped joints the PLA is only 0.15mm thick so I judged any airflow disturbance would not be too serious. This meant quite a big part of the rear new nose ad to be cut off! The next task was to try to arrange that the fuselage skin was cut so new nose exactly matched the fuselage to allow a "skin to skin" glue joint. It was never going to be possible to achieve this all around the fuselage and the inlet duct at the same time so the join was limited to a few major areas glued and held in place with masking tape. With the plane resting vertically on its nose it was left for 24 hours for the glue to dry. There were several areas where the skin did nor meet so individual "inserts" were required to be glued in. At least the 5mm XPS is easy to cut and sand to shape. After a good few hours of doing this and some light weight filler I was satisfied the nose was as secure and the air intakes were as smooth as possible. The original windscreen and cockpit canopy will be reused. Next comes the task of squeezing in the ESC, Rx and battery box into the cockpit area. At least I knew where it all originally went. To be continued.

Unfortunately my Hunter F6 met with ground, quite fast and almost straight down. A true nose plant but all my own fault. I had forgotten that determining orientation at distance with an all black plane can be a problem particularly when close to the ground. However as is usual for a foam stressed skin construction it crumples and absorbs the crash energy. This means the remainder of the airframe is completely undamaged and still operational. It will simply need a new nose making. The tricky bit will be arranging the damaged area so the nose can be stuck on. The new nose built as a half shell over the plan. When complete it is rigid enough to be lifted and the other side built on the same way. This is exactly how the original was built so the "new" is no heavier than the "old". More complex than the nose repair of the Skyray so not a 3 day job! To be continued.

Welcome Brit in Brazil I too have a Lidl conversion but my favorite is a FX707s Albatross conversion. Still a relatively cheap "chuck glider" but is bigger, flies (and glides) rather better than a Lidl so much so it is actually worth fitting a folding prop!😉 Any pictures?