Joe M
Member
The local club's annual float-fly event is just around the corner (August 18th) and I'd like to bring something a little larger and more interesting than what I've brought in past years. One of our club's most talented builders is planning on finishing and flying a 1:7 scale Nakajima A6M2-N that he's been working on since 2012. Here's a link to his build thread on RCU for those interested, it's a genuine work of art: Royal Zero Kit Build into Rufe
So when the 3DLabPrint Seiran briefly went on sale for $16 last month I figured it was a good opportunity to try getting my own Japanese WWII-era seaplane ready for this year's event. At the very least it'll be a fun way to use ALL of the build platform on the ol' 3D printer. Also I imagine it will really make Gerry's Rufe look great in comparison. I'm scaling the model up by 50%, which makes it 1:7.64 scale with a 63.2" (1605 mm) wingspan. Not quite 1:7 scale, but close enough for me. The increased size also makes the wing slightly less of an issue, since 3D printed planes tend to run heavy. The recommended cubic wing loading factor of the 3DLabPrint Seiran is 14! That's a lot! At 63" I would have to break 180 oz (5.1 kg) to match that. As estimated I'm guessing my final WCL will be around 11-12, which is still high, but manageable. I'll also be covering the 3D printed parts in kraft paper and polycrylic to add strength and ease the painting process.
Here's a whole boatload of specs and weight/cost budgets:
So far I've printed and roughly assembled the wing:
Huge, isn't it? That's 856 grams of filament including the ailerons. I still have to do some solvent welding between the panels due to some curling as the result of an inadequately heated enclosure. I don't usually have to worry about PLA parts curling, but these were just too huge not to (the wing chord is >15.5" at the root!) The extra holes and servo extensions are for water rudders, which will be installed in the floats. The single large water rudder on the original design looks super flimsy, and dual water rudders just make more sense at this scale.
Currently I'm printing the floats, which have required slightly more print process modifications than the wings, though it looks like they should come out strong at about 400 g/each. That would give me 844 grams of weight allowance for the fuselage and battery holder, which should be adequate. I'm expecting to go over the 300g weight budget on the covering and paint, though given the 5+ kg of thrust as long as I can keep the WCL under 12 it shouldn't have a problem rotating off water... I hope.
Now to start covering the wing!
So when the 3DLabPrint Seiran briefly went on sale for $16 last month I figured it was a good opportunity to try getting my own Japanese WWII-era seaplane ready for this year's event. At the very least it'll be a fun way to use ALL of the build platform on the ol' 3D printer. Also I imagine it will really make Gerry's Rufe look great in comparison. I'm scaling the model up by 50%, which makes it 1:7.64 scale with a 63.2" (1605 mm) wingspan. Not quite 1:7 scale, but close enough for me. The increased size also makes the wing slightly less of an issue, since 3D printed planes tend to run heavy. The recommended cubic wing loading factor of the 3DLabPrint Seiran is 14! That's a lot! At 63" I would have to break 180 oz (5.1 kg) to match that. As estimated I'm guessing my final WCL will be around 11-12, which is still high, but manageable. I'll also be covering the 3D printed parts in kraft paper and polycrylic to add strength and ease the painting process.
Here's a whole boatload of specs and weight/cost budgets:
Scale: | 1:7.64 |
Length: | 53.7" (1363.98 mm) |
Wingspan: | 63.2" (1605.28 mm) |
Wing Area: | 794 sq. in (51.2 dm^2) |
CG: | 4.3" (109 mm) from LE |
Airfoil: | LHK508 |
Motor: | SK3 5045-660KV |
Battery: | 4S 2200 x2 |
Prop: | Xoar WWII 15x10 |
est. power: | ~1100 W |
Weight (est.): | |||
Printed Parts: | 2500 g | ||
Wing | 856 g | ||
Floats | 800 g (est.) | ||
Fuselage | 770 g (est.) | ||
Battery Holder | 80 g (est.) | ||
Cover/Paint: | 300 g (est.) |
Power: | 911 g | ||||
2200mAh 4S 45C | 273 g | x2 | 546 g | $64.28 | |
SK3 - 5045-660KV | 280 g | x1 | 280 g | $44.64 | |
CC Talon 90 | 85 g | x1 | 85 g | $65.32 | |
Electronics: | 235 g | ||||
Corona DS939HV | 12.5 g | x2 | 25 g | $13.42 | |
Corona DS339HV | 32 g | x4 | 128 g | $36.92 | |
OrangeRx R920X V2 | 16 g | x1 | 16 g | $20.58 | |
Rx Voltage/Temp Module | 6 g | x1 | 6 g | $1.11 | |
Servo Extensions | 15 g | x4 | 60 g | $9.99 | |
Total: | 3946 g (139 oz) | $256.26 |
Wing Loading: | 25.2 oz/sq.in (77 g/dm^2) |
WCL: | 10.7 |
W/kg: | 278 |
W/lb: | 127 |
Est. Flight Time: | 5.3 minutes |
Est. Current at Max | 80 A |
Est. Static Thrust: | 177.4 oz (5028 g) |
Est. Thrust/Weight Ratio: | 1.26:1 |
Est. Max speed in level flight: | 61 mph (99 km/h) |
Est. Stall Speed: | 25 mph (41 km/h) |
So far I've printed and roughly assembled the wing:
Huge, isn't it? That's 856 grams of filament including the ailerons. I still have to do some solvent welding between the panels due to some curling as the result of an inadequately heated enclosure. I don't usually have to worry about PLA parts curling, but these were just too huge not to (the wing chord is >15.5" at the root!) The extra holes and servo extensions are for water rudders, which will be installed in the floats. The single large water rudder on the original design looks super flimsy, and dual water rudders just make more sense at this scale.
Currently I'm printing the floats, which have required slightly more print process modifications than the wings, though it looks like they should come out strong at about 400 g/each. That would give me 844 grams of weight allowance for the fuselage and battery holder, which should be adequate. I'm expecting to go over the 300g weight budget on the covering and paint, though given the 5+ kg of thrust as long as I can keep the WCL under 12 it shouldn't have a problem rotating off water... I hope.
Now to start covering the wing!