Scale Soaring UK

The last few wet days has seen work slowly progressing. The ribs were attached to the bottom spar. The false leading and trailing edges were added and trimmed. The joiner tube was threaded though W1, 2 and 3 then blocked in between the spars. The upper spar was then glued in place before adding the webbing. 1/16 ply webs were used back and front of the first five bays and hard 1/16 balsa webs to the back of the spars all the way out to the tip.
Brian.

Nice, Brian.

Yesterday I attached the front underside sheeting forward of the spar. After trimming I added the ¼ plywood hard points to the root rib for the incidence peg and the front and rear retention pins. I then pinned the wing to the building board to hold it straight and then added the front upper sheeting forward of the spar to complete the D-box.
This afternoon, after trimming up the D-box sheeting, I have added the rest of the upper surface sheeting back to the false trailing edge including the airbrake opening.
The wing is now upside down on the bench waiting for me to fit in the servo mounts, the block reinforcement at all the aileron and flap hinge points and the servo wiring before I sheet the underside.
Brian.

The wing build has progressed quite a bit in the last few days. I have installed the servo mounts and wiring in the wing shell. I have also added all the balsa hard points for the ‘hinge-point’ hinges to the false trailing edge. The remaining underside sheeting was added and servo access hatches formed followed by the balsa leading edge. I then started on the flap, incorporating a plywood trailing edge as well as balsa hard-points for hinges and the horn. The aileron has been carved from stiff but light balsa and seems to fit well. I am now just waiting for the glue on the top sheeting of the flap to set before final sanding.
I always have difficulty in setting up and drilling the holes in the wing and control surfaces for the ‘hinge-point’ hinges. As I have ten on each wing it was a job I was not relishing. I have ended up making a drilling jig which will allow me to drill at right angles to the TE and at the correct angle into the surfaces. As you will see from the image below it comprises a wooden frame with two brass tubes to guide the drills. The smaller tube takes a 3mm drill for the hinge shank and the larger takes a 5.5mm drill for the clearance hole at the surface for the hinge knuckle itself. I have tried it out on some scrap wood and it seems to work just fine.
Brian.

How have you arranged the ply TE Brian?
Is it 1/16” ply butt jointed to 1/16” balsa, then add & sand top skin to get a ply TE?

I’ve currently got a solid balsa TE on the Albion flap, but wondering if a built up one with ply strip would be an improvement or not.

Peter

Hi Brian

I have been using a variety of "jigs" to drill hinge holes for years and it really does make the job easier and more accurate. May I suggest a slight mod to your jig to make things even easier?

Draw a line on the top of the jig that is centered on each of the brass tubes to use as a reference. On the wing, or whatever part you are hinging, assemble the fixed and hinged part in the correct orientation and mark the locations of the hinges and then using a soft pencil and a set square extend the marks forward and rearwards just far enough so that they are visible when the jig is in position. It is now a simple job to align the mark on the jig with the mark on the model to ensure the holes for the hinges are in the correct position and the holes in both parts line up.

Stay safe.

AEB

Peter, absolutely spot-on. I don't feather the balsa sheeting before gluing - I simply pin the sheet in place and clamp the trailing edge below a long piece of spruce. When the glue is set I plane and sand the sheeting down to the ply trailing edge.

John - good call mate. I have drilled all the holes for the flap by peering down the tubes to find my location marks. I will now go out and make the adjustments before I do the aileron. By the way the jig works perfectly and I have the neatest set of hinges EVER.

The flap end the ailerons are now basically complete and have been taped temporarily to the wing. The wing tip was glued in place and carved to a pleasant shape (the full size machine had tip plates on the wings and these, on the model, were constantly getting ripped off when landing in heather and tussock grass). I have checked out the fit of the wing to the fuselage and I am pleasantly surprised that everything lines up perfectly.
As mentioned above I have drilled out the mounting holes for the flap using my home made jig and a dry check shows that it fits well and gets the amount of movement I was expecting.
Brian.

Brian,
The flap hinging looks very neat.
I will be very interested to see the result on the ailerons (top hinged?) as I may well give the installation method a go myself.

Do you use a mylar strip to cover the lower gap when flaps are not deployed?
I tend to use bottom hinged flaps & with a small bevel for up flap deflection, there is only a small top gap.
Swings & roundabouts no doubt

Do you think that your built-up flap arrangement is likely to be any stiffer than a solid balsa TE?
I like the idea of the ply TE to get a well defined straight edge & the overall assembly is probably a bit lighter than solid balsa - depending on balsa density. Harder grade balsa no doubt equates to stiffer, but heavier.

Peter, I often use bottom hinging when I need the flap to come down to the vertical. In this case I only need the flap to slow the model down and to provide additional lift on approach, the air brakes doing the rest. The main use of the flaps on this model is to work in conjunction (and in opposition ) to the elevator. I will cover the gap on the underside with white mylar.
The flap is built with medium grade straight grain balsa and are quite stiff and definitely lighter than a solid alternative. However the aileron is carved from hard, but light, straight grained balsa as it is rather long and quite thin towards the tip and I didn't want it twisting in flight.
After I have completed the covering and hinging I will attach a thin strip of white vinyl along the hinge line just to tidy it all up.
Brian.

The right hand wing is now basically complete barring the covering. I finalised the root rib area, installed the incidence peg, wired up the connector plug and drilled the retaining peg holes. The bare wing half, including flap and aileron weighs 1lb 3oz less than the original right hand wing. I am sure that the film covering is not going to weigh anything like that so I am quietly pleased so far.
I have now pinned down the spar for the left hand wing (remember left hand, left hand .....) and I will start the fettling of the wing ribs in the next couple of days.
Brian.