ASK13 1/3 Scale**

[Bovin]

It is going to get a big glider! Nice build! The kit looks very sophisticated .

Vincent

[Peter Balcombe]

Tow release servo plate

Last few bits of main structure now added, including rear longeron sections, wing root skin supports etc., plus removeable tow release servo plate now secured with screws.
With the tailplane seat now complete, I trial fitted the stabiliser together with elevators & rudder structures taped on - just for fun

Root skin support

With the basic fuselage structure now more or less complete, this will now be put to one side whilst a start is made on the wings.

Root skin support

Tow release servo plate

Rear spine joint doubler

[Peter Balcombe]

On with the wing ....
Once the 1st pair of main spars spliced up from 1/2 x 1/4” Spruce strip to make the full 2.5m length, these should be tapered on the front edges from about inboard end of the aileron to give 1/4” Sq. at the tip (as detailed on the drawing detail sketch).
In parallel, the 2 main spar web pieces are joined & then the lower spar glued to the front of the web, aligned with the spar lower edge.
It is worth checking that the ribs can be slid onto the spar web/lower spar before using any glue as I find that the slots on both need to be cleaned up to remove cutting char deposits & also angle the rib slots a little to allow these to take up the required non-90 degree angle to the spar.
With the spar assembly positioned over the plan, the ribs can be glued in place, using the building tabs on most ribs & bottom of spar web, it is easy to check everything is seated & the ribs are angled correctly. Addition of the false leading edge sections allow the individual rib angles to be set up nicely.
Note that in common with most large printed plans, the CNC cut parts are of slightly different size, so the plan is used for information & a guide to the arrangement, rather than a precise mirror.
I tend to start by the fitting a few ribs to set the basic structure shape & then fill in spaces with the remaining ribs.
Note that all ribs can be dropped in from the top - although you need to remember to fit the servo plates between two pairs of ribs as they are fitted!
So far, I have fitted most of the centre section ribs as shown below.

[Jilles]

Some comments on Peter's remarks on slots and drawings
Ply is manufactured with a tolerance like any other manufactured item e.g. 1.5mm ply can be between 1.4-1.6mm When 1.5mm ply is specified I make in general 1.6mm slots in the nc parts. Sometimes parts meet under an angle and the slots needs to be even wider. There are NC cutters that can be programmed to cut bevels etc but would be very expensive.
In principle I do not make the slots wider for angled parts but leave it to the builder to adjust. than there will be a neat fit, making the slots wider to fit the angled part could result in a sloppy fit.
Printed large drawings on paper are a pain. They shrink or expand due to temperature and moisture. When you print the LH and RH wing they both are the same but you build one wing first and start the other 2 weeks later there will be a difference. There is the option to print on a polyester type of print media but at a price. Another advantage is that glue will not stick to it. The material is transparent so you can use both sides of the same wing drawing for LH and RH wing.
In the past when drawings were printed on a drum from a transparent original the paper print was on the outside of the drum making the print 3mm longer per meter than the original.

Cheers

Jilles

[Peter Balcombe]

Thanks Jilles.
All of the ribs have now been fitted to the initial structure, plus the top aileron hinge spars & facing and the top brake box area support spars.
Adding the root end ribs needs a bit more care as although the building tabs give a vertical reference & the nose tabs define the location on the false LE, the drawing/measurement has to be used to used to ensure ribs remain parallel to the others as there is no notched spar web inboard of R6. However, the rib notches for the drag spar can be used as an alignment check as you go.
Note that the root rib is set at the dihedral angle of 4.5 degrees as shown in the plan detail sketch. Small tapered ply spar web pieces (W13) are provided to fit between R1 & R2 so these can be initially used as gauges when adding the root rib R1.

[RobbieB]

'....................Printed large drawings on paper are a pain. They shrink or expand due to temperature and moisture. When you print the LH and RH wing they both are the same but you build one wing first and start the other 2 weeks later there will be a difference........'

One of the reasons I build large wings like this:

Not quick but no errors.

[Peter Balcombe]

With the top drag spar in place, the remaining root spars can be cut & epoxied into place.
Then, when the top has been completed, the wing is briefly turned over to fit the lower drag spar - again fixing with epoxy.
Once the epoxy has cured, the wing will be turned back to sit on its building tabs whilst the drag spar web pieces are attached.

[Keith]

Peter why are you using so much epoxy, when pva is fine?

[Peter Balcombe]

Keith,
I’m only using it on the root spar system & joiner tube joints for maximum strength in these higher stress areas.
Only other place I tend to use it is when splicing spars - for same reason.
I use Aliphatic glue everywhere else for wood joints (because it sands nicely if required) & white PVA for applying ply skins using the ‘ironing’ method.
Peter

[Jilles]

For my PVA is a no no to structural items, Like Peter epoxy and Aliphatic glue is what I use and PVA only for planking to be able to use the iron on method. Aliphatic glue also sets faster so you can go on with the project. PVA is not moisture proof and will let go in time. Not a problem for indoor projects but I live near Brisbane Australia, most of the time hot and humid. From experience the UK is not that dry either. I intend to fly my gliders for a long time. PVA also stays a bit rubbery what is not handy with sanding
Here we can get a special PVA for exterior use that may be more moist resistant. I tried this once but it does not work so well with the Iron on planking method.

Cheers

Jilles