HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Dec 10, 2012, 11:29 AM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,324 Posts
@papaalpha - your photos look brilliant!

I've just finished my Radian retro makeover (Bergfalke Rad'ster) and now can get back into my ASK-13. Your K13 pilots, aluminium skid colour and detail looks great! Yes, our weather is in the tank here too, snowy, rainy, freezing winter.
studioRS is offline Find More Posts by studioRS
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 10, 2012, 06:18 PM
Registered User
Joined Oct 2012
51 Posts
The skid is not just aluminium colour - it is aluminium!
I always epoxy on a very thin piece of what was an aluminium venetian window blind vane/blade. It is less than 1mm thick and can be cut with scissors. It allows take offs (when aerotowed) and landings from the roughest of tarmac runways with no resultant damage. One can also put a bit on the tail skid.
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Dec 10, 2012, 07:51 PM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,324 Posts
Quote:
Originally Posted by papaalpha View Post
The skid is not just aluminium colour - it is aluminium!
I always epoxy on a very thin piece of what was an aluminium venetian window blind vane/blade. It is less than 1mm thick and can be cut with scissors. It allows take offs (when aerotowed) and landings from the roughest of tarmac runways with no resultant damage. One can also put a bit on the tail skid.
That is such a great idea, venetian window blind.
studioRS is offline Find More Posts by studioRS
Reply With Quote
Old Dec 16, 2012, 02:41 PM
Registered User
Joined Oct 2012
51 Posts
Well another 3 test flights today , all with violent 'bunting' i.e., going up and down. sorry no photos but forgot my camera. Wind about 12 to 17mph. My fellow flyer that was with me said that he had had a similar problem with a model and that he could only fix it by setting the angle of attack/wing incidence on the model of the main wings, not as scale but so that the tailplane and main wings were virtually horizontal with the fuselage. Anyone else come across this phenomna and any cure?
My Bocian has a scale incidence of the main wings (see photo) and flys fine but maybe has a scale wing (from a freebie plan on scalesoaring.co.uk) . I had always thought by altering the angle of the tailplane incidence I could fix the problem but I am not convinced now that this is necessarily the case although one would have thought it should do. Help!
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Dec 16, 2012, 04:20 PM
Registered User
dion9146's Avatar
United States, KY, La Grange
Joined Feb 2006
1,712 Posts
A picture of the root really doesn't mean anything unless lined up with the tail.

All of my airplanes with a fixed stab are set at zero. Most stabs set to negative (or positive) are done so to make up for other bad designs characteristics. Stabs with anything other than zero are just wasted drag IMHO.
dion9146 is offline Find More Posts by dion9146
RCG Plus Member
Latest blog entry: Big Gull plan pics
Reply With Quote
Old Dec 17, 2012, 07:39 AM
Registered User
Joined Oct 2012
51 Posts
Apologies dion9146 as yes should have included the tail in the photo which I have now done. Your comments confirm my co flyers experience and checking my other scratch builds (see pics) confirms for a basic aerofoil keep the main wings incidence horizontal with the fuselage and 1 or 2 degrees tail incidence at most.
I will now set to and carry out the modifications with more enthusiasm.
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Dec 17, 2012, 07:52 AM
Registered User
dion9146's Avatar
United States, KY, La Grange
Joined Feb 2006
1,712 Posts
For what it's worth, decalage, CG, and other trim adjustments always seem to be a matter of preference and strong opinion.

http://www.rcgroups.com/forums/showthread.php?t=1766381
dion9146 is offline Find More Posts by dion9146
RCG Plus Member
Latest blog entry: Big Gull plan pics
Reply With Quote
Old Dec 17, 2012, 08:24 AM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,324 Posts
Does this help any or furthur confuse all? Tailplane incidence indicates, -2 deg.

Q. So, by your photos, I can see that the main wing incidence compared to tail looks the same as the Bocian (although, it might very well be different and I just can't see it), should the K-13 main wing be tilted forward (ie TE turned up) so it is more parallel to the longitudinal axis?

Thompson
studioRS is offline Find More Posts by studioRS
Reply With Quote
Old Dec 17, 2012, 09:29 AM
Registered User
prodjx's Avatar
Joined Jan 2007
4,711 Posts
I think something else is going on with these bunting issue's. Like the c of g. I know the K-13 is forward swept so that would tell me that the c of g at the root would be closer to the LE. I have flown a full sized K-13 and it was a very pleasant glider to fly and I would think the model of it would be too.
prodjx is offline Find More Posts by prodjx
RCG Plus Member
Reply With Quote
Old Dec 17, 2012, 03:49 PM
Registered User
Joined Oct 2012
51 Posts
Yes studioRS I am now halfway thru fixing the main wing at zero incidence and tail will be 1 degree. On reflection I recall I had a bunting issue with my Oly 2b and only fixed it by uplifting the trailing edge of the main wings by one quarter of an inch and then found I could remove most of the nose weight. I think the problem has to be the main wings stalling when thrown off the slope, then it dives, then you recover, then it stalls and on and on. Therefore if the main wings can maintain flight I am sure I will then be able to get the battery and weight away from the nose so that the dives arn't so dramatic.
Yes I got checked out for aerotows in a K13 in my youth to then fly solo in a Slingsby Swallow on aerotow and the K13 was and still is a great all round recreational and trainning glider.
I have to conclude that with this sort of 84'' span of model and much less than quarter scale; with a simple Clark Y profile taking into account the Reynolds effect it has to be main wings zero incidence and tailplane virtually the same. The next flight should let us know!
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Jan 04, 2013, 04:34 PM
Registered User
Joined Oct 2012
51 Posts
Following adjustment of main wing incidence and that of the tailplane - see pic had another go on the slope with first throw and the model went to ground as had accidently flicked on the airbrake switch putting both ailerons up!
Next throw and whilst the model climbed nose up a little I managed to get relatively level flight although was still bunting but not as aggressively as prior flights so I thought I would bring it down and reduce the ATV on the elevator.
However at some point I must have cracked the rear fuselage just in front of the tail as when I threw it again I noticed the rudder was off centre and in the second of looking down at the trim for the rudder the model went down vertical from about 30ft like a spent rocket!
Only into the long grass and repaired this evening for another go sometime but I have to say I have never had a model that seems to be balanced on such a knife edge centre of gravity with such an extreme nose drop although the wings stay perfectly level.
I was using the heavier 5 cell battery and interestingly I did find an online c of g calculator that puts the c of g exactly where I had determined it.
I still think the model is inherently tail heavy but the only way I can fix such now would be to slice of the top half of the fuselage to reduce the the fuselage inners/members or maybe shorten the fuselage half/one inch or so. Very frustrating when one finishes a nice looking model that is already looking weather beaten before its even flown properly. Still I have never been beat yet by my home builts but this one is taking me close to the edge!
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Jan 05, 2013, 07:39 AM
Supersonic Engineering
GordonTarling's Avatar
UK, Greater London, Uxbridge
Joined Mar 2001
3,103 Posts
Thompson - loving your build of the ASK-13 - my first glider flight was on one of those out of Lasham, UK. Saw your earlier mention of Sugarbush - did you ever get to fly there? We were visiting friends who own a B&B there in September last year and just HAD to go for a flight in the club ASK-21 - it was ace!
GordonTarling is online now Find More Posts by GordonTarling
Reply With Quote
Old Jan 05, 2013, 08:42 AM
Registered User
Joined Oct 2012
51 Posts
For anyone using this plan I would suggest that you cut away fuselage formers and any weight to the fuselage rear of the c of g as much as possible as despite adding more lead today my model still succeeded in burying itself near vertically from 50ft (see pic) and to add more nose weight would only make the model too heavy to ever be a decent soarer even if flying with no faults.
papaalpha is offline Find More Posts by papaalpha
Reply With Quote
Old Jan 05, 2013, 08:51 AM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,324 Posts
I say one more go at it!
studioRS is offline Find More Posts by studioRS
Reply With Quote
Old Jan 05, 2013, 08:54 AM
Klassische Segelflugzeuge
studioRS's Avatar
Northern Vermont
Joined Jul 2010
1,324 Posts
Quote:
Originally Posted by GordonTarling View Post
Thompson - loving your build of the ASK-13 - my first glider flight was on one of those out of Lasham, UK. Saw your earlier mention of Sugarbush - did you ever get to fly there? We were visiting friends who own a B&B there in September last year and just HAD to go for a flight in the club ASK-21 - it was ace!
Thank you on the build, it is my first and going slowly. I've been sidetracked with CAD drawings lately. The ASK-21 or Blanik at Sugarbush both look nice to fly in. I've never been up yet... Will try this summer.
studioRS is offline Find More Posts by studioRS
Last edited by studioRS; Jan 05, 2013 at 09:40 AM.
Reply With Quote
Reply


Thread Tools