Extra Slim

3 Jun 00- Wings folded up in flight - fuselage became a lawn dart - written-off.

extraslim02u.gif (10299 bytes) extraslim03u.gif (8120 bytes) extraslim04u.gif (8765 bytes) rip.gif (3013 bytes)

N of launches / time 88 18 hours 45 mins


Wingspan 48 in. 1.22 m
Wing Area 708 in 45.7 dm
Flying Weight 4 lb. 13 oz 2.19 kg
Wing Loading 15.7 oz/ft 47.9 g/dm
Motor MDS 48 Pro with OS 40/46 muffler (the motor is 3db quieter than with the MDS muffler).
Propeller APC 12" x 3" (310mm x 95mm)
Receiver Micron Competition - PPM - 7 channel - 35 MHz
Servos Elevator - Futaba S-3001
Rudder - Futaba S-3001
Ailerons - 2 JR 517 - mixed to give flaperons.
Throttle - Hitec HS-101
Static performance Never tested with the MDS 48 Pro.
Flight performance OS 25FP - Underpowered for the type of model. Climbs out about 20. Maintains level flight at 1/3 throttle. Loops from level flight at 1/2 throttle down to about 5m diameter loops (with flap mixing). Extremely good roll rate.

MDS48 Pro - Climbs out at 90 (vertical). Maintains level flight at idle. Loops from level flight at idle down to about 8m diameter loops (with flap mixing), larger diameter must be due to increased weight. Roll rate as before.

Originally powered by an old OS 25 FP and a 9 x 6 propeller (at 10,400 rpm) and a flying weight of 3lb 12oz wet. The wing is a 13% thick symmetrical section. Even with this engine the flight envelope is amazing but vertical performance is poor. However, on a positive note it only registers between 70 and 76 dB at 7m keeping the locals happy.

12 Jan 99 - Unfortunately I had a mishap last weekend and stalled the model, whilst doing a low slow inverted pass, and "landed" vertically nose down. The impact snapped the wing main spar at the port wing / fuselage joint. It will be fairly simple to repair, once I get my work area sorted out & find time. At the time of the accident the model had flown 53 times and been in the air 10 hours 27 mins.

2 Jul 99 - I have just finished the repairs to return the model to flying condition. The repair consisted of 4 pieces of " square hardwood mounted inside the existing spar. These are tapered at the ends to try and reduce the stress concentration at the repair. I have also fitted my spare MDS48 Pro with an OS muffler (as it's a lot quieter) and slightly larger fuel tank. Whilst I was at it I fitted a crude steering tailwheel as I knew I would need the weight back there. Even then I had to lead to balance the model - 75g (2.6oz) of lead to the tail & 45g (1.6oz) to the starboard wing (to offset the engine). The total increase in all up weight (including fuel) is 485g (17oz) and is mainly due to the motor. Despite the extra weight the increase in power to 1.6hp will more than compensate.

3 Jul 99 - Managed to get a flight in after returning from a model air display. I wish I hadn't as the conditions were a little gusty & I hadn't flown this model for a while. Set-up the engine, lined it up, a gust came through & the model took off, I over corrected & hit the ground hard. The undercarriage legs & propeller took most of the impact, but the RX battery tried to leave the wing through the bottom skin & hatch. The repair only took about 20 minutes to do & that included checking for other (less obvious) damage.

3 Jun 00 - Whilst flying today, the wings decided to touch tips above the fuselage. They then swung back and departed the model rearwards. All the servos were mounted in the wing (as normal) and detached themselves from the controls on the fuselage. The engine was pulled to full throttle as the wings detached prior to the servo detaching itself at the ball joint and the elevator and rudder were no longer connected to the servos. The fuselage now uncontrolled and at full throttle flew as well as can be expected and accelerated into the ground about 20 from the vertical. Numerous sites of impact damage were made in the wings and fuselage, and it would be quicker to build a new model than to repair this one.

I think I'll build the twin version with 2 electric motors as an experiment. I have a couple of 650 motors which may fit the bill. When I decided further what I am to do, I'll create a new webpage for the new model.

[ BACK ]