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Re: 1/4 Scale Charlesworth ASK13

Posted: 01 Dec 2019, 13:50
by John Vella
RobbieB wrote:
01 Dec 2019, 12:49
Peter, why would you want an anti-servo tab on a servo operated control surface?

Set up as that, the servo is trying to move the elevator up and the tab is trying to push it down again. Anti-servo tabs are designed to put some 'feel' into the stick with a pilot on the other end of it, not a servo. It's just making the servo work harder.
Robbie, the reason for doing it is because it imitates the movement of the full size K13. On my Charlesworth K8 as the tailplane is normally left rigged the push rod comes from a quadrant on the fuselage under the tailplane. The tab movement thus follows the full elevator travel in a scale antibalance fashion. This scale setup has worked well for many years. In the event of derigging one mini lock nut on the end of the push rod is undone. Regards John.

Re: 1/4 Scale Charlesworth ASK13

Posted: 01 Dec 2019, 20:49
by RobbieB
I'm very familiar with the operation and principle of Flettner-type trim tabs in all their guises - numerous years experience with them on big ship's rudders was my first introduction and experience with those boys.

My point is, why introduce something into a model, purely in the interest of scale that is not in the best interest of a servo doing its best to operate the control surface - it's a servo, not a human. It serves(no pun intended) no useful purpose other than scale fidelity and will have a detrimental effect on the servos performance and power consumption.

Scale versus logistics? In this case, for me, logistics wins hands down - all cons and no pros.

I now await my lashing from the Scale Police with baited breath...........................

Re: 1/4 Scale Charlesworth ASK13

Posted: 01 Dec 2019, 21:18
by Peter Balcombe
Robbie,
As I said earlier, the trim tab operation happens to be scale, but was chosen to simplify model rigging - slot the tailplane on without any need for separate elevator or tab linkage connection :D
(Same form of operation on the original Charlesworth Olympia 2b plan & my VV400 flies very well with a standard analogue servo).
Peter

Re: 1/4 Scale Charlesworth ASK13

Posted: 01 Dec 2019, 23:04
by John Vella
Robbie, if you look at the pics of my K8 you can see that the Flettner Tab system is quite a noticeable feature. I am modelling a scale glider and the extra load on the elevator system is minimal and my servo and double battery system is well able to cope . PS the elevator loads on the full-size are rather light, and the system was put in to deal with ham fisted abinitio pilots. Regards John.

Re: 1/4 Scale Charlesworth ASK13

Posted: 05 Dec 2019, 10:41
by Peter Balcombe
Moving back to the wings, I have have progressed the LH wing top surface around the brake box & covered the D box to the start of the last bay.
Next job is to tackle the root end which tapers down towards the next rib.

Re: 1/4 Scale Charlesworth ASK13

Posted: 07 Dec 2019, 23:41
by Jilles
Hi Peter. nice touch that scale like operating trim tab. However it is working the wrong way. When set to a certain setting the trim tab should move the opposite way to the elevator movement. If the elevator moves up the trim tab moves down relative to the elevator and the other way around
All Schleicher models from K6CR to ASK13 had this feature except those with the all flying tail plane like K6E
If the glider needs down trim the elevator needs a down thrust that is achieved by the trim tab going up.
I did experiment this on a full scale K8, by keeping the stick(elevator) in a fixed(blocked) position. One can then control pitch by the trim tab only. but moving the trim lever forward resulted in nose up and they other way around.

Re: 1/4 Scale Charlesworth ASK13

Posted: 08 Dec 2019, 09:32
by Peter Balcombe
D box & root end skinning now complete on the LH wing, with aileron still to be cut out, LE, tip and all rib cap strips to be fitted.

Re: 1/4 Scale Charlesworth ASK13

Posted: 08 Dec 2019, 10:47
by Geoff Pearce
Looking very nice Peter,l

Re: 1/4 Scale Charlesworth ASK13

Posted: 08 Dec 2019, 15:57
by Peter Balcombe
Many thanks Geoff.
This wing is from the new CAD version of the Charlesworth wing design, so Cliff Evans should now be able to supply the parts as an alternative to the original Charlesworth version.
The wing spar assembly uses interlocking ribs & spar webs, plus top & bottom spars, rather than the Charlesworth method of making up the spar box & fitting rib sections to front & rear. The false LE is also notched for rib tabs & the ribs have pre-cut spar notches. Building tabs on each rib should ensure the correct washout is automatically built in.
The RH wing is from the original Charlesworth short kit set, so the maiden will soon identify any differences :o

Re: 1/4 Scale Charlesworth ASK13

Posted: 01 Jan 2020, 11:29
by Peter Balcombe
A bit more work over the last couple of weeks.
The main visible progress is that I have decided to replace the solid hollowed out hardwood nose cone as suggested on the plan with two CNC parts cut to form an interlocking 1/4" Ply nose assembly cruciform which is then drilled out to take a commercial tow release.
The cruciform is epoxied to a backing plate to allow bolting/glueing to the fuselage front former whilst still allowing good access to the release mechanism.
Church roof can be added before the outside is filled & shaped to the nose profile.
The photos show the basic structure with small balsa blocks added to support the front drilled joint, plus a claw type release fitted.