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Post by sean on Apr 14, 2007 11:47:50 GMT 10
Andrew, some more rambling about differential :-)....
You could use differential to fix the Drongo's pitch down with aileron, but in my opinion using that method it's hard to know what the results will be like in the air.
In my mind, mixing a bit of up elev with aileron is easier to get your head around. Yesterday, when flying the Drongo, I found that if I coordinated a small amount of up elevator with aileron the pitch problem disappeared. So knowing that, if you mix in say 10% up with left and right aileron you should go some way towards fixing the prob. You can then fine tune that value over a few flights to get it spot on. It's also a good idea to assign a switch to turn the mix off in case it makes things worse and the plane's hard to fly.
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Post by thevon on Apr 14, 2007 13:36:04 GMT 10
Sean to clarify - mine doesn't have any AD set yet. So quite likely it will benefit from negative AD as does Glenn's. When the down aileron moves more than the up, it should cause a similar effect to mixing in some up elevator? I think I have to do it by varying the up and down end points (throws) as I don't think my radio allows it's AD function with Elevon function.
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Post by sean on Apr 14, 2007 13:57:06 GMT 10
Hi Andrew,
Negative AD will make it worse, no doubt about it! You'll need positive AD (that is the the up going aileron needs to move up by more than it does now).
I'm sure Glenn's Drongo benefits from negative AD, as does my Bat, but having flown your's I can say without doubt that it needs positive AD (which on a flying wing is the same as a bit of up with aileron). If you make the down going aileron move down more that the up going aileron moves up, then that's exactly the same as mixing in down with aileron, which will make matters worse. To see what I mean, look at your plane from behind, give it full aileron and feed in a bit of down. With the controls like this, you can see that the down going aileron goes down more than the up going aileron goes up.
My only guess as to why your Drongo pitches down with roll is that the ailerons already move down further than they move up, it might be worth measuring the movement. The Drongo needs a tiny amount of elev throw, so even a slight difference in the up/down movement of the ailerons could cause a big pitch with roll.
The only other possible explanation could be an overly rearward CG, but if that was the case I think it would be completely unflyable.
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Post by thevon on Apr 14, 2007 18:24:24 GMT 10
Ah, yes, I get you. I was thinking back to front, ie dropped aileron causes camber and more lift - not the case with a plank or swept wing. My mistake. I'll try it positive.
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Post by ding on Apr 14, 2007 18:40:52 GMT 10
It's worth mentioning that I don't think most people measure and verify that their control throws are correct. Ie that at full deflection the amount of throw is identical. This can make for some whacky happenings as you increase control throws.
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Post by thevon on Apr 14, 2007 21:22:57 GMT 10
Guys I blocked the Drongo on the kitchen bench and used a ruler to measure the up and down throws. Embarrassed to say that yes, they were neg AD ... ie travel was approx 14mm up and 19mm down. So I've set it back to equal each way. Will see how that goes! Wont' be tomorrow though - the Seabreeze wind forecast is terrible this week but it might come good for Friday.
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Post by ding on Apr 14, 2007 22:32:35 GMT 10
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zipper
> 50
Off The Edge Sailplanes
Posts: 88
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Post by zipper on Apr 15, 2007 22:42:13 GMT 10
If only we had some wind down here, I would give your settings a go on mine to see what effects it has. I am getting itchy fingers to give it ago.
Glenn
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Post by thevon on Apr 16, 2007 13:23:10 GMT 10
Yeah Glenn, we need wind up here too! On Friday it wasn't really enough. When I was first trying the Drongo in really strong wind at Easter, even without any fine tuning it was insanely good. I can really see why people fly these things. It was the most exciting flying I've done. I can't wait to try this DS thing with it .... !
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Post by sean on Apr 16, 2007 17:47:43 GMT 10
Hey Andrew, looking at Seabreeze.com it looks like Sunday at Mt Mee might be a goer, fingers crossed!
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Post by sean on Apr 16, 2007 17:49:33 GMT 10
Hey Glenn, where abouts in the Byron area do you fly?
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Post by thevon on Apr 16, 2007 19:38:30 GMT 10
Hey Sean, Glenn (Zipper) is from west Sydney. Dunno if he gets to Byron. Eric (Ezza) is from Byron and he knows the sites down that way.
Yep it looks good for Sunday but the forecast can't be trusted! I might be able to get away on Friday again and I'd like to do some work clearing those spikey dead trees sticking up on the left side of the slope. Greg (from Peachester) might be able to come along - he was a huge help when we did some clearing of the slope last time. Need to make room for those enormous dive-passes!
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Post by sean on Apr 16, 2007 20:09:20 GMT 10
Woops, Sorry guys!
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Post by ezza on Apr 16, 2007 21:39:43 GMT 10
Hey Glenn, where abouts in the Byron area do you fly? Hi Sean, I mainly fly a few sites along Coolamon Scenic drive, Possums, Powerlines, Montys and the lookout that is mentioned in the flying sites section, of the Windsock website. These sites work on anything from ESE to NW. During the spring it blows Northerly most days of the week. Possums is a great site with a huge grassy bowl and easy landing. You may have to share it with the paragliders, if the wind is light. Most of these sites, and the others along this ridge, are on private property....so care must be taken. Flying up at the lighthouse, particularily the hanglider launch pad, has strong clean lift in a SE. There basically is no landing zone at these sites and usually plenty of tourists....so be careful. Lennox Head is good in ENE to NW. If you walk up to the top of the hill and fly off the cliff, the lift can be very strong. Skennars head is also good in anything from SSE to ENE. If you guys are ever down this way let me know. Eric
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Post by sean on Apr 16, 2007 22:18:24 GMT 10
Hey Ezza, I lost a Halfpipe flying at the top (cliff) of Lennox Head, it was about 30kts and got caught in turbulence during a landing attempt. It ended up in the thick bushes behind the cliff, it's still there I presume I didn't see exactly where it went in and the bushes are impenetrable. It was an awesome flight before that happened though, but I don't think I'd brave it again after losing a nice model there... (the Halfpipe was really quite sweet). I like the look of Skennar's Head, nice grassy landing area. The sites on Coolamon scenic drive sound awesome, any hints as to where they are? Also, are the land owners OK with out of towners such as myself flying there?
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