Sloping Off - March 2005
The Plank
A Free plan review by Terry Antell
The plan was published in Q&EF, November 2004. It's one of those double side prints, which I hate. Years ago we had to pay to have the plan copied (well, I didn't, actually). These days, computers and scanners have overcome many copy problems.
I copied the ribs and the fuselage. The other side had both wings detailed. I like home copy/printers. Why? Things don't stretch like dyeline printing, great!
The model is an electric semi aerobatic job. The span is 40", a sod of a span. I started by splicing hard and soft wood together to form the hard and soft spars.
In Q&EF it's called, "Plank in a box". Well, I decided not to build the box as it was only used to transport the model. My Ford Focus Estate will take at least 6 feet in length, so, with a very small span, it wasn't needed.
As is usual for me, I decided to build in a little more strength!!
I cap stripped the top of the ribs.
Used hardwood spars (not soft balsa).
Added softwood tips.
Added corner fillets for strength.
Added 1mm ply under the wing area on the small fuselage.
Instead of a standard 400 motor I used a 400 size brushless with
7 x 1300mah NiCad's (instead of 700mah suggested).
Yep, the weight increased; still, I knew the brushless motor would take the strain. With extra weight came a little faster flying speed! The wing is 1.5, mm thicker than the plan, that's top to underside. The cap stripping I added to the ribs accounted for this. In turn I realised that this will cause extra drag.
The radio component locations are not shown on the plan. As I was building a one piece wing I decided to fit a JR R700 receiver in the wing centre section. Two servos (Mini) are fitted to the wing, each controlling one elevon. The extremely small boat shaped fuselage houses the motor, speed controller and 1300mah battery pack.
The elevons are from stock trailing edge (solid) balsa. What a fag to have to build the control surfaces from stock strip balsa. Yes, they would have been lighter, but weaker.
Besides holding the wing, the fuselage accommodates the vertical fin.
Many years ago, me and another modeller, Norman Childs both bought a flying wing 60" glider. It was a French import! They named it Tetras 1 (or was it II?). Anyway, it was a bugger to fly. I remember how it used to oscillate (porpoise) something awful if it went too fast. Flown too slowly it would suddenly drop its nose.
The Plank does all of these things. I've now added to the list, sudden loops or violent tuck under when flown on full power. On the good side, it will fly inverted, roll, loop (inside and outside), bunts (and any other bodily function).
All this on a 42" span model, using a 400 size brushless motor and 6"x 3" folding cam prop. It cost me about £26 for the balsa and hardwood.
The plan can be purchased, via Q&EF, for £8.00.
