BN-2 Islander

[Ady Hayward]

Hi folks.

I had the good fortune to be invited to a recent indoor flying session hosted by the Ashford (Kent) model club. I saw several KF winged machines fly very nicely and at the end of the meet a good friend challenged me to come up with something for the next meet 2 weeks later.

With a challenge like that who could resist. Due to a very tight budget I had to build using what was in the build area so a depron model was to be built. The only suitable motors available were two 12mm brushed inrunners for 2s operation previously attached to a MPX Fox so a simple twin was envisaged.

The Britten-Norman Islander was chosen due to its simple lines, ample wing area and cavernous fuselage all easy to carve from a sheet of 6mm depron. I chose a wingspan of 27.5" (700mm) which worked out nicely as that meant the scale wheel size would be 1"(25mm) of which I had sufficient for this aircraft.

Adrian

[Ady Hayward]

Part 2.

I found some nice 3 views online and expanded the image to the correct size and traced the fuselage outline, and took measurements for the wing and tailplane. The engine nacelles, undercarriage legs, fin and rudder were traced too and the tracing transferred to the depron by laying the tracing paper face down and drawing over the line to deposit the graphite on to the depron. As the nose block and nacelles were to be laminated these parts were cut out, trimmed to shape and drawn around to create the remaining laminations. The fuselage formers were measured from the screen image and drawn directly on to the depron sheet for cutting out. In all about 1/3 of a half sheet of 6mm depron was utilised, and a small amount of 3mm plywood. Assembly was very quick using evo stick solvent free adhesive for the laminated parts and foam safe C/A adhesive for all remaining glue jobs. The wing was also very simple to make using a full section of 6mm depron to the plan form. I then cut out the top section of full span 1/3 chord from the leading edge to make the KF section (Kline–Fogleman) **LINK**

I let a piece of 3mm diameter carbon rod into the top of the main wing section before sticking down the upper section to complete the assembly. The nacelles were hollowed out to take the can motors and the wiring exit points were marked and cut out of the wing before the nacelles were glued into position. The wing and nacelles were sanded to shape and the ailerons were marked and cut out and the torque rods were made and fixed into position, followed by the ailerons being hinged and re attached making sure they have full and free movement.

Adrian

[Ady Hayward]

Part 3

The fuselage was assembled ensuring all was true leaving the bottom sheeting off until the nose block, tailplane and fin were fixed in place and control runs sorted and stowage for the lipo (850mAH 2s in my case) and place for the 20A brushed esc. The wing was then attached, servos installed and the lower sheeting added and all sanded to shape. The windshield was taken from a section of a 1.5litre soft drink bottle. The undercarriage legs were then glued into slots cut through the nacelles and wing and wheels added ensuring they are free to rotate. the noseleg was made from 20swg wire bent to shape and glued into a slot cut into the nose block.

The whole thing took 6 evenings to produce and weighs just under 200g minus lipo. As seen in the pics to follow, I use a full 6 channel Faast receiver. The plane was maidened outdoors (Thankfully) and was found to be very lively on the controls with a surprisingly good turn of speed. She showed a tendency to tip stall if pitched too rapidly, or slowed too much so a steep landing approach was used to maintain airspeed before a gentle flare where she settled down nicely. It seems the tip-stally nature is down to the upper section of the wing is too narrow, and should be nearer 50% chord instead of the 30% chosen initially. This has been remedied and has much improved the characteristics. More flights will follow when I am able, meanwhile some colour and detail will be added.

Adrian

[J D 8]

Like it.

[john stones 1 - Moderator]

looks good Ady

nice job, strange looking props

what sort are they ?

[Ady Hayward]

Hi John D and John S and many thanks for the compliments. The props are GWS ones as supplied with the Cargotrans (C130) kit. The props are 3"x2" in size and are made for the 12mm brushed inrunners used.

Best regards

Adrian

[Ady Hayward]

Hi Folks. I managed to get out for a short time and explored the flight characteristics a bit more thoroughly. The modification to the wing top surface in extending the top section to 50% chord has improved the low speed end considerably. There is much less wing dropping tendencies and a stall can be reached in the normal manner, albeit with a sharp wing drop. This is easily recovered in a few feet using rudder and pulling out gently. She will turn quite tightly before departing such that she could be flown indoors, but not recommended due to the speed she can achieve. Loops and rolls are possible from level flight, with a rapid rate of roll to both the left and right. Landings need a bit of distance just to get everything stable in the descent with the flare and touchdown not showing any tip and nose grazing tendencies.

My thoughts... a nice sporty little outdoor park flyer and needing to be maybe 30% bigger and with a lighter wing loading for indoors. I will probably go for a built up wing with a clark Y section and a bit of washout factored in.

Adrian

[Simon Chaddock]

Ady

That's very nice.

It will be interesting to see what difference in flight characteristics result from a 'conventional' wing section.

I know some people swear by KF wing sections but my lightweight park flyers manage very nicely on simple 'Clark Y' types.