14 Apr 06 - Updated the data table.
June / July 1915
|Drawing of the
Rib Hole Cutter
The EAT propeller to be
|Before <- pack of ribs -> After||1 wing set||First wing panel||All wing panels||Fin & Rudder||Stabiliser & Elevators|
|The main Gnome
|Uncovered fuselage with varying equipments fitted.||Painted
|The fuselage covered|
|N° of launches / Time||0||
|Wingspan||53.1 "||1.35 m|
|Wing Area||820 in²||52.7 dm²|
|Flying Weight||~ 5 lb.||~ 2.27 kg|
|Wing Loading||~ 14.0 oz/ft²||~ 42.9 g/dm²|
|Wing Cube Loading||5.9 max. - Trainer (same as full size)|
|Gearbox||MEC Monster Box 6:1|
|Propeller||Wooden 4 bladed 15" x 12" (scale diameter - see photographs above)|
|Batteries||TBD - 4S1P FlightPower EVO20 3700 mAh LiPo|
|Speed Controller||Aveox L160uP - 60A - 4 - 16 cells - BEC & Brake|
|Receiver||Hitec HFD-07RA - PPM Dual Conversion - 7 channel - 35MHz|
|Servos||Elevator - To be determined|
|Rudder - To be determined|
|Ailerons - To be determined|
|Static motor parameters||Predicted 3250RPM @ 14.1V drawing 19.1A, estimated power to weight of 57W/lb.|
|Flight performance||Not yet flown|
14 Apr 06 - I just realised I hadn't updated the data table from my latest thoughts, so I corrected that error.
25 Oct 04 - I can't believe it has been so long since I did something with this model - editing the British Electric Flight Association magazine has absorbed so much of my free time. I have said that I will be resigning from editing the magazine at the Annual General Meeting in March 2006. Hopefully this will allow me time to complete lots of projects I want to do.
All of my original analysis is now fairly redundant as the most sensible battery system now would be a Lithium-Polymer pack and I will be using an Aveox 1406/4Y motor. I hope to find time to reconsider the options based on my original tests below.
12 Sep 01 - I test ran the Astro 40 motor today to determine the best combination of cells to use. I have included the results obtained (& calculated) in a table below. Most of the figures are obvious, however, the Cruise Time is that estimated by ElectriCalc when mild manoeuvres and good throttle management is used. ElectriCalc was allowed to increase the weight of the model as additional cells were added. The lighter the model, the longer it will fly for a given battery pack. I obtained very similar results using RC-2400 cells so I didn't both the tabulate them, however, the duration would increase by about 20% as the weights are almost identical.
|No & type of cells|| Voltage
|RPM|| Power Input
| Cruise Time
| Power Ratio
|12 Panasonic NiMH 2000||12.8||20.8||2950||266||8.9||47|
|12 Sanyo RC-2000||13.2||22.2||3050||293||8.6||52|
|14 Sanyo RC-2000||15.4||27.3||3450||420||8.3||75|
|16 Sanyo RC-2000||17.2||32.5||3750||559||8.2||99|
6 Sep 01 - I have just ordered a dummy engine of scale appearance as well as scale Lewis gun and instruments. These are slightly oversize as they are 1/6th scale, but I'm sure it won't be obvious to the eye. I will be continuing the construction shortly.
20 Apr 01 - I have finished the initial building of the 4 main wing panels and upper wing centre section. The structure is 1/16" (1.6mm) and 1/8" (3.2mm) ribs with 1/4" (6.3mm) x 1/8" front spars, 1/8" square rear spars and a single 1/8" dowel between them. The straight part of the leading edge is 3/8" (10mm) x 1/4" and the trailing edge is 3/8" x 1/8" strip. The wing tip is formed by gluing 3 strips of 3/8" x 1/32" (0.8mm) strip around a former. The total weight of the wing panels so far is 5.4 ounces (153g). I have still to add the leading edge sub-ribs, wing joiners, reinforcing for the struts and tail boom mounts. Using the same method as for the main wing tips, I have just laid up the leading edge section for the tailplane from 3 pieces of 1/4" x 1/32" strip.
20 Mar 01 - I laid out a set of wing ribs for one panel to check I had everything, and decided to take a snap shot for this page (at top). I included a print of photograph showing the full size wing panel to verify the parts. The photograph shows to complete set of ribs for one of the 4 wing panels, including the leading edge riblets and diagonal trailing edge pieces.
19 Mar 01 - Having looked at the enlarged plan I decided that I didn't like the wing profile as it was too thick compared to the full size. I thought about using the RAF 15 section, but it is a very fiddly section and I couldn't be bothered. I decided to reduce the plans Clark Y section to 9% thick and produce the ribs using the sandwich method. You will notice above that 3 lengths of blanks are in the pack. This is because the DH2 wing has a narrower centre chord than the outboard part of the wing. Additionally, one rib (in each panel) stops at the rear spar so is even shorter.
Firstly I made 2 templates for the main and centre ribs out of 1/8" liteply. The edge of these was hardened using Cyanoacrylate to limit changes in shape during the production of the ribs. 51 Rib blanks were cut about 1/16" larger all round than final size to allow for finishing. The reason for the odd number is that only the upper wings have a centre section as the lower wings mount straight to the fuselage. The rough cut blanks are clamped together, then planed & sanded to finished shape (shown as before & after above). The spar slots were cut using a razor saw and a small chisel like knife blade. A piece of glass paper was when glued to an offcut of balsa strip the width of the slot to finish the bottom of the slot. As you can see you end up with a pack of ribs that are almost identical, which is much quicker to make than a fraction of the time the ribs would take if made individually. The back was then disassembled and remade with only the centre ribs as these have a different rear profile. The diagonal riblets and tip ribs will be produced individually as there are only 4 of each. I have yet to decided whether to fit the leading edge riblets, between each main rib, or leave them out. It is complicated by the early aircraft not having them fitted anyway, but if I model a later model it would look wrong without them - I better decide which aircraft to use as a subject.
I needed to make holes though all the ribs to clamp them into a block. I decided that the best way was to make a special cutter from a piece of scrap brass tube (shown above). The tube had the outside chamfered at the cutting end and a slot ground to ½ the depth to allow the debris to leave. This cutter has now made well over 200 holes in a mixture of balsa and liteply with now signs of wear. The only annoying feature is that the debris doesn't get discarded as hoped, it has to be picked out after a few holes. Perhaps if the slot were cut deeper it might work.
11 Mar 00 - This is being built as an enlarged version of the free plan issued with Flying Scale Models, January / February 2001. I did this so that I could fit the Astro 40 I had spare into it. I had the plan enlarged to the next paper size increasing the area by 2 and thus linear dimensions by 1.414 times. At this size it also makes it more practical to fit most of the rigging wires, although not all of them will be carrying load.
I intend to make all the dimensions scale including propeller diameter and Wing Cube Loading (WCL). To maintain the originals WCL of 6.2 to 6.6, the target weight range is 84 to 90 oz. The Astro 40 with Superbox weighs 16½ oz., and 18 RC-2000 cells weigh 37½ oz, leaving 30 oz. for the airframe if I want to hit the lower target. However, I will have a much higher power to weight ratio available (~ x 2) as I don't like the idea of the scale rate of climb of 215 ft/min.
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