SF33 1/6 scale

[Tonyw51]

Hi Peter,
Thanks for your comments, I just feel uncomfortable with the lack of bracing from the attach point through the butt joints. I have covered the the Fin and Horizontal Stabiliser with 0.5mm ply which has added very little weight but it has stiffened the parts and spread the loads. See attached



I am happy with the Du-Bro hinges which have fitted quite well.

Looking forward to your updates.

Cheers,
Tony

[Peter Balcombe]

Just made up a couple of cowl cheeks.
Only a plan view of the cheeks showing internal hollowing out is shown on the plan, so have plumped for 1” height in side view with freehand curves. Balsa block is roughed out then sanded to give outer curves.

I will now Glass the cheeks to give some strength before hollowing out & fixing in place (centreline on the hatch edge!)
(The fuselage will also be glassed to provide a painting surface rather than try to apply film).

[Peter Balcombe]

The 2nd wing is now also about ready for covering although aileron horns still be made & fitted.
Meanwhile, I have applied 2 layers of lightweight glass cloth to the cowl cheeks, sanded smooth & then waxed prior to making a backup plaster mould before digging out the majority of the balsa from the resultant shells - just in case
Once I have cut a nose aperture on each, the cheeks will be epoxied to the cowl hatch & then the relevant part of the hatch sides cut away to allow cooling air to be directed into the motor/ESC.

The fuselage has also been glassed & given an initial dust with primer to see how much further work is required prior to painting.

[Peter Balcombe]

With removable motor access hatch fixing sorted using pegs and magnets, the cowl cheeks were epoxied to the hatch so that they straddled the join line.
A liitle bit of joint reinforcement later, the cheeks can be used as finger holds whilst removing the hatch.
With the fuselage glassed & rubbed back, it's nearly ready for painting.

[Peter Balcombe]

Fuselage primed and then given a couple of coats of SigMarine gloss white, cockpit given a (short) pilot figure and canopy glued on with Canopy glue.
Tail feathers also covered using HK covering film (with slightly contrasting colours/paterns top & bottom to help with model orientation).

The wings have also had the aileron servo & spoiler installed prior to covering with the same HK heatshrink film.
The outrigger legs have also be fitted after drilling a locating hole in the spruce subspar at the inboard end & then removing a narrow strip of the balsa skin to accept the leg after covering. The outboard end of the legs are retained by small plates screwed into the hardwood sub-spar/main spar.

[Peter Balcombe]

With the tail feathers glued in place, its time for the first overall assembly.
Power train and wheels to fit, but nearly there now.

[Tonyw51]

G’day Peter
That’s looking good. I am interested in the glassing of the fuselage, what weight and cut did you use? I figure that is the way to go as the fuselage is very light in structure and a laminate of glass would be a very beneficial move

Cheers
Tony

[Peter Balcombe]

Hi Tony,
I used the standard 25gsm lightweight wing skinning variety, with just a single layer, essentially done as 2 sides with overlap along top & bottom centres.
Resin applied sparingly over the cloth with a brush, making sure that everything was fully wetted out.
Rubbed back before applying a dust coat of primer to help see & correct the worst imperfections (particularly around wing roots) before brushing on a couple of coats of Sigmarine white.

[Peter Balcombe]

Power train now installed.
I am using an old Dualsky XM3548 brushless motor with XC4018 ESC supplied by a 3S 2200mAH Lipo.
(There is plenty of space to fit a larger capacity battery if needed).
With a fixed 2 blade 9x6 Master Airscrew prop, this combination gives just over 300w on the wattmeter, with just over 30A at full throttle.
Max motor efficiency current is 35A, so a little more is available, but max current is 40A.

With the model (currently still less it’s tailwheel assembly & Rx) balanced (2200 battery fully forward), the overall weight comes in at 1.8Kg (4lbs), including about 200g of lead hot glued to the bottom of the motor bay.

Currently trying to find a tailwheel assembly with a bracket small enough the match the fuselage rear end, which can also be fitted with a 15mm tailwheel. (Cliff May need to 3D print a slightly smaller version of the Commercial unit I have!)
Also need to find & fit a couple of small outrigger wheels - otherwise it’s about ready to commit to aviation once a receiver has been fitted & set up.