Stevo Posted August 6, 2013 Share Posted August 6, 2013 Hi all... I beg of your help One stock AcroWot Foam-e, Stock motor, CoG 75mm as in the plan.. Had to add 20g at the rear though. All control sufaces installed correctly (difficult to do otherwise!!) Problem... Takes off great.. but immediately goes vertical.. Half throttle, level flight, throtlle up and it goes into a steep climb. Around 2mm of down elevator needed for level flight. Bought back down again, raised both ailerons very slightly, and less down elevator needed now but still a bit. This could clinch it... Powered shallow dive (around 20-30 degrees) power of and again she climbs up... OK Doctors - those are the symptoms, what's the cure BTW AcroWot Foamie fans, have you seen this... **LINK** Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 6, 2013 Author Share Posted August 6, 2013 Oooh..No takers?Cog..?? Quote Link to comment Share on other sites More sharing options...
Robin Kearney Posted August 6, 2013 Share Posted August 6, 2013 I'm no expert, but to me it sounds like it needs more down thrust on the motor. If you look side on can you see if it is level or perhaps some up thrust? Does it glide as expected? my mini tyro needed a good few washers at the back of the motor mount to solve this same problem. Quote Link to comment Share on other sites More sharing options...
Rich too Posted August 7, 2013 Share Posted August 7, 2013 I agree, although I generally leave mine well alone! Perhaps I should try it in future. Rich Quote Link to comment Share on other sites More sharing options...
Greybeard Posted August 7, 2013 Share Posted August 7, 2013 Seems like the motor thrust line to me too, I'm not sure that it will be easy to alter though. Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 Thank you Gents! Well it says to me that opening up the throttle and the 'ballooning' seen thereafter smacks of little or no down thrust, so in agreement. But, even in a glide I still need a little down elevator trim to keep it level. My concern here is that it's what it is... AcroWot Foamie and others that I've seen required very little trimming.. battery in ...CoG good to go and... off...! So why was mine nose heavy on a standard recommended 2200mAH pack? Down trim to keep it level? Downthrust to be added? I found it hard to balance either right way up or inverted on my balancing jig.. It would sit level after adjustment, and itf I tilted it slightly down (either on tail or nose) it would stay down! Also the CoG (I'm going to study **LINK** so shallow powered dive, power then cut and model dives... requires *more* weight on the tail? Of course I've no problem with experimenting with it all - that's part of the fun of course and something that I enjoy. Any comments appreciated - I think in the past it was a case of set it on the bench and it's set for life will not apply... a more scientific approach to trimming, Stevo - get your act together, man!!! Quote Link to comment Share on other sites More sharing options...
stuey Posted August 7, 2013 Share Posted August 7, 2013 I dont know if my cg dive method is strictly right but I do this. Get some good height, then into wind power off and a 45degree dive. I am looking for a gradual pull out, not too much though. If you leave some power on the thrust could affect the test. Quote Link to comment Share on other sites More sharing options...
graham dewis Posted August 7, 2013 Share Posted August 7, 2013 Hi stuey It needs some downthrust.. Take off the prop take the motor and glue with some cyno a 4mm washer over the bottom screw hole on the motor you my have to file the washer a bit so that the circlip on the motor shaft does not catch it. Reinstall the motor make sure that the washer is at the bottom of the plane. put the prop back on and go and fly. By the way in a glide the plane will and should loose height so dont trim for level flight with no power on, trim for level flight at the speed you want to fly at with power on then when you throttle back the plane will decend on it's own. I did the above on my Acro Wot and moving the throttle from half to full does not make the plane climb. Happy Flying Gaham Edited By graham dewis on 07/08/2013 10:25:24 Quote Link to comment Share on other sites More sharing options...
Rich too Posted August 7, 2013 Share Posted August 7, 2013 and adding "down" to keep straight and level means tail heavy, not nose heavy! Rich Quote Link to comment Share on other sites More sharing options...
stuey Posted August 7, 2013 Share Posted August 7, 2013 Its not my model btw, was just offering my opinion as far as the cg test goes! I fully agree that it sounds like some down thrust is needed. Quote Link to comment Share on other sites More sharing options...
PatMc Posted August 7, 2013 Share Posted August 7, 2013 Forget about the downthrust until you've moved the cg back incrementaly as far as you find the model still comfortable to fly adjusting the down trim as you go. Then see what happens to the zooming tendency but also check if it inverted before adjusting the downthrust. Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 As always thanks to all.First remove any trims.. second add downthrust with a washer.. third remove a little weight off tail. Fly and check with zero trims ..Lets hope the wind dies down... Quote Link to comment Share on other sites More sharing options...
PatMc Posted August 7, 2013 Share Posted August 7, 2013 Reverse the order of 2 & 3. Adjust CG & trim interactively before considering downthrust. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted August 7, 2013 Share Posted August 7, 2013 What happens when you cut the power completely Stevo...? Does it glide OK?? If it does its a thrustline issue if not its a CoG or incidence issue.... I've always understood that the Foamie Acrowots fly brilliantly straight out of the box so the need for weight at the rear & a possible thrustline issue is a bit of a surprise.... Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 Yes Steve that's what I thought. I had a WOT4 Foam-e and no extra balancing required! When I balanced it it was nose heavy (not by a little - by a LOT) for the stated 75mm and tha batery was as far back as the tight space would allow. Hence the 20g on the rear. In a gentle dive, power off and it climbs.. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted August 7, 2013 Share Posted August 7, 2013 Mmmmm something not right here then....what battery have you got up front? Does the wing fit into the wing seat OK? Wing twisted? Tailplane misaligned??? You've not fitted the wing upside down or something daft like that...? Could you maybe take it back to the shop & compare it with another model? Or maybe there is another one at your club? As a moulded model it should be consistent dimensionally but it just sounds like something is wrong somewhere to me!!! Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 2200mAH as prescribed... Its the only on that will fit... All seated OK, No misalignments... Am going to double check it all when I get home from work Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 OK.. On the bench.. CoG came out as 70mm and not 75, so a little more on the tail it was. Now balancing dead level at 75mm. prop changed for a 12x6", reading into it all it seems a lot of owners do this, current is reduced, therefore heat (current squared) is too. Top speed sacrifices a little, but I don't care. I have added minimal down thrust with a very thin washer - getting that motor out and back in was a nightmare.. Waiting for the wind to die down. Edited By Stevo on 07/08/2013 18:11:56 Quote Link to comment Share on other sites More sharing options...
graham dewis Posted August 7, 2013 Share Posted August 7, 2013 Stevo Dont forget to set the elevator level Graham Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 OK Here's the score. The prop made a great difference - far more manageable; short take off run and good vertical performance. And a tad of extra downthrust meant that when I whacked open the throttle, it did climb, but not balloon. Anyhow... After the short take off run, (level elevator Graham!!) it shot upwards like a rocket... vertical with just a little up elevator. Same problem. Got Steveo Jr. (Nick) to fly her inverted while he was having a go... and I observed the sticks. Quite a lot of down to maintain inverted IN ADDITION to the down that we trimmed into it to get it to fly level. Given that I'm flying with 2mm of down by default, it was very manageable and not over sensitive. LAnding it, which is always a buttock-clenching experience for me) was a breeze. Over to you aerodynamisists. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted August 7, 2013 Share Posted August 7, 2013 This doesn't make any sense.....it sounds tail heavy with the "down" trim & the ballooning but lots of forward stick to maintain inverted flight points to nose heavy.... What happens in a power off dive? Not necessarily vertical but greater than 45 degrees.....does it pull out on its own (usually indicates nose heavy) or start to tuck & dive streeper (usually indicates tail heavy)? There is something not right here.....you haven't trapped the aileron servo wire between the wing & wing seat have you? That would alter the angle of incidence..... Other than that I'm flummoxed..... Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 And you are puzzled...!!!From what I remember yesterday, an unpowered shallow dive saw it climbing out... Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted August 7, 2013 Share Posted August 7, 2013 .......which would indicate nose heavy..... I wonder if you still have too much upthrust though......that would translate as needing downtrim, balooning AND the need for lots of forward stick when inverted.... Do you have any tubing that will slot neatly over the prop driver at all......? A length of this on the end of the motor might show a dodgy thrust angle..... Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 Intrigued..!I understand what you mean Steve. However just looking at the front you can see down thrust.. but Ill collate all the posts overnight and tomorrow and test out late tomorrow afternoon. Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 7, 2013 Author Share Posted August 7, 2013 Btw.. all incidenes are spot on with nothing trapped or misaligned! Quote Link to comment Share on other sites More sharing options...
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