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- This topic has 11 replies, 7 voices, and was last updated 6 years, 7 months ago by john thompson.
08/05/2016 at 9:25 am #77602Denny DockParticipant
Repairing my 720 Creschendo that I splattered at the Nats last week…Here is what I think happened.
Hit the rear end of a Pick-up at the 2015 Nats(tried to piggyback off Larry D).He maxed …I didn’t) Knocked the wing off with 1/2 the pylon. I don’t think I got it put back together correctly.The LEFT wing tip was forward making it go hard right. Will measure after major repairs.
Denny08/09/2016 at 12:25 pm #77616
I guess it was a lousy NATS for Crescendos. My Class A Nos version stalled off the top of the climb on the first flight and stalled all the way down, which it does from time to time. I’m beginning to think the leading edge is too pointy. I am pretty sure on the plan that I have it shows the bottom on the wing completely flat, but I was looking at the three-view in the Zaic Yearbook last night and it showed the leading edge with a fair bit of upsweep or Phillips entry. So this winter I plan to build a new wing with that and a few other changes. Denny, what does the leading edge on your model look like?
Attachments:You must be logged in to view attached files.08/10/2016 at 6:55 am #77619
Simon . For some further information on the Crescendo go to SAM1066.org left hand list August New Clarion click on this, it will bring up a list of previous years . Go to Feb 2010 to see an article that I have written about this model . You will see that the actual winning model used a slightly semi symmetrical section . if you wish for more info please contact me via the personal link. Not sure how one does this with new system .
I have plan drawn up by Ron which shows all , I would be happy to send you one .
John08/10/2016 at 10:26 am #77621
Thanks for the tips! I have actually been reading through all your articles on power models in the New Clarion, but I haven’t got back to 2010 yet. The articles are great and I think it’s amazing that you manage to build so many power models! I loved the piece on the Vector Director!
For the Crescendo, I believe the plan that I have is the one that Dave Draper drew up as it has all his notes on it and does show both airfoils. It hadn’t really occurred to me to build the one with the semi-symmetrical airfoil. The flat bottom airfoil looks right and glides very well, most of the time. My plan is to make the leading edge blunter and, as most people over here do, split the wing spars with webbing in between. Those changes, I hope, will cure the sporadic stalling. It doesn’t stall off the top that often, but when it does it won’t recover. I suspect the auto rudder helps the transition considerably, but we re not allowed to use any form of auto surfaces in nostalgia gas, even if they’re shown on the plan.
Regards, Simon08/11/2016 at 1:01 am #77623
Simon . Yes ,that is the plan that Ron drew up . Stalling try a tubulator on the Tailplane about say 6/7 mm back from LE , this helps sometimes , also a blunt nose ( just sand away some of the nose , and retissue that bit ) . This is something you can try without rebuilding . If you use RDT ,you can provoke the stall by slightly altering the climb , but then bring it down safely , thus seeing if you have a fix or not . I have not had that problem , but I did with a San De Hogan which I never really cured . The model(engine ) is really too big for my arms to hold safely now , so I have not pursued a solution .
The Crescendo I have ,is now powered with a Nelson 15 side exhaust which does increase the crime (Oh dear ,predictive text ? Climb ) rate somewhat. All good fun .
John08/13/2016 at 2:10 pm #77633Denny DockParticipant
I checked all three sizes of my Crescendo’s…nothing out of the ordinary with my LE. entries…About what the Draper plan shows.I did try putting some Polyspan 3/4 in strips in an X pattern on my 720…I think it helped making it more rigid.
Denny08/13/2016 at 11:32 pm #77635Steve JensenParticipant
Can anybody see Simon’s attachment? I can’t.08/14/2016 at 4:41 pm #77665HANK SPERZELParticipant
Simon were you flying a Okibird at the Nat’s?
Hank08/15/2016 at 8:42 am #77675
A Nelson .15 on a Crescendo; Yikes! Mine really hauls with its nostalgia era OS .19 which turns 15,000 rpm with an Apc 8-4. I won A nostalgia gas at the Eastern States Championships with it on the weekend — four maxes and dropped three seconds on the fifth. It was windy and turbulent and every flight ended up in the soybeans, but at least I didn’t end up in the top of a very tall tree like my nearest competitor! The model flies a lot better at Geneseo than it does at Muncie and actually recovers from the stalling most of the time. Thanks for the tips John, I will sand the leading edge and see if that helps. I believe glue-on turbulators are not allowed under the nostalgia gas rules over here, although there’s no real reason you can’t overlap the polyspan covering to get a bit of turbulation. I can’t see my attachment either; or anybody else’s photos, so I guess Alan is still getting the bugs out on that. Hank, I didn’t fly my A/B Okie Bird at the Nats. I was test flying it on Sunday but it was really windy and it was hard to figure out how it would go. However, I flew it over the weekend at the Eastern States Championship and got it going fairly well. It really honks with the Cox Conquest. Thanks for all the comments everyone!
Simon08/16/2016 at 11:18 am #77679Mike SchwartzParticipant
Bob DeShields has built and flown Crescendo’s from .02 size to C ships. Here is the trim settings he uses. Bob uses the Jay Jackson plan for the Crescendo which is the best one to use. Aerodyne has the plan, which they got from Bob. The cg is at 85 percent, which is right at the front of the wing trailing edge. Start the wing incidence at 5/32. Use the flat bottom airfoil. The leading edge of the wing and stab has a small entry with a basic rounding of the leading edge. Add a turbulator upper spar to the first third of the wing which NOS allows. No turbulator on stab. Swept forward wing tips add washin. Need to have 3/16 washout on both tips for 1/2A size, 1/4 on larger models. Add add 1/16 washin on right inner wing panel on 1/2A looking from the rear, 1/8 on larger models. 2 degree’s left thrust. Keep stab as light as possible. The shorter the nose the better the power pattern. We also use the shortest nose possible on all our models. The wing covering needs to be as stiff as possible due to the flex in the wing under power due to the high aspect ratio of the Crescendo wing.
Mike08/21/2016 at 2:40 pm #77690Fred TerzianParticipant
Gentlemen, This is my first effort to respond to comments on the Forum. I am curious about the discussions concerning Ron Draper’s “Crescendo”. I originally started building his ’56 winning design back in the late eighties-early nineties using plans provided by John Pond. His plans were “copied” from the Zaic Yearbook, which was probably copied from the Aeromodeller rendition right after the W/C win (Cranfield?). After starting to build the fuselage, I realized Pond’s plans showed two different lengths on his top and side views. Luckily, I was in touch with Ron Draper around the ’95-’96 time frame, and this was approaching the 40th anniversary of his winning flights. He sent me a copy of his re-drawn plans, with lots of extra detail and the two airfoils he used (one flat, one undercambered). I believed it also confirmed that the main wing spar was set on the bottom surface and not inset as shown in the Zaic three-view. I received Ron’s permission back in ’96 to include this plan on the NFFS list, and as far as I know, it is still available, although possibly in “digitized format”. I’m sure this is the plan that John Thompson refers to, and I have no idea what the Jay Jackson version looks like. Using a copy of that plan Harry Klarich (recently deceased) provided a “short kit” through Klarich Custom Kits. His business is now in limbo until family members decide what they want to do
Fred08/22/2016 at 1:43 am #77691
Chaps . The main spar on the winning model was inset from the bottom , then a strip of 3/32 was glued to the bottom of each rib, thus covering the spar and sanded to the ” semi symmetrical shape . Ron according to conversations I had with him, was determined to try a wing with no turbulator spars on the top or bottom .I have never seen another one, aside from mine and the one Ron built for the 50th anniversary . where we had some pics taken at the SAM gala at Little Rissington in 2006 . The original was stolen in 1957 on a OOS flight , the rebuild accidently got chucked out when his loft was cleared . He is now about 88 and we talk occasionally on the phone.
As a matter of interest I always felt that the tissue sag between the ribs on the bottom produced a near flat bottomed section , compared to a regular build with the spar on the bottom producing a slight under camber with tissue sag ?
This is all 60 years ago ,but still having fun with toy airplanes. Which I might add I consider a hobby, not a sport !
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