Bob Cotsford Posted July 7, 2016 Share Posted July 7, 2016 Commiserations BEB, you had a good go at a model of an aircraft that looks to be designed in such a way as to make everything as hard as possible. The pusher motor so close to the elevator must create a blown control effect, over sensitive under power, under sensitive without. Remote elevator and rudder on outriggers braced by wires- an invitation for flex and poor response. Slow bipes do seem to respond to rudder control better than to ailerons especeilly where the ailerons are on one wing only, perhaps this is model is a candidate for coupled aileron/rudder? I agree with Martin, it sounds to have been nose heavy with elevator response enhanced by the prop blast, but possibly affected by a flexible structure? At least enhanced until you cut the power. But what else could you have done in the circumstances? You are an educator, put this one down as a practical lesson that should help others attempting this model Quote Link to comment Share on other sites More sharing options...
will -0 Posted July 7, 2016 Share Posted July 7, 2016 Aw that sucks Did you use the rudder at all? Quote Link to comment Share on other sites More sharing options...
Lindsay Todd Posted July 7, 2016 Share Posted July 7, 2016 Well that's a shame, I'm sure the bits can go in the 'come handy sometime box'. Sometimes its better to trash it beyond repair and go through the painful exercise of trying to figure out what to do to prevent it going pair shaped again. I suspect battery moving around might well be the culprit given the varied levels of control authority, short coupled bipes can be very sensitive. Time to get something new on the building board quickly I would say.Linds Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted July 7, 2016 Share Posted July 7, 2016 Lindsay is right I think, BEB. Perhaps regarding the battery but IMHO most certainly about the 'building board'. Why not your Ballerina? I remember you did start the "Sans Tutu" already. Hakuna matata Chris BRU - BE / CTR Building Board Control Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 7, 2016 Share Posted July 7, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 7, 2016 Share Posted July 7, 2016 Real shame BEB, that looked lovely. Any chance something was loose/flexing? Cheers Danny Quote Link to comment Share on other sites More sharing options...
IanR Posted July 7, 2016 Share Posted July 7, 2016 Put some of the non-slip mat down flat on your worktop then place a battery on top. Now, if you apply just a small amount of downwards pressure you will find that the battery just will not slip from side to side. A clubmate uses this method of retention for 6S batteries and performs all kinds of wild gyrations with no problems. Providing a Velcro strap is applying sufficient downwards pressure I can't see the battery moving at all. BEB's earlier photos show 2 Velcro straps which is surely enough. Additionally, from BEB's description, it sounds as though he never got a chance to throw the model around sufficiently to move the battery. I think the problem lies elsewhere. BEB, thanks for another great build log and for having the guts to show us all the results of your unsuccessful maiden. I am reminded of Danny F's Spitfire. Hats off to you both. Ian Edited By IanR on 07/07/2016 15:35:48 Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted July 7, 2016 Share Posted July 7, 2016 That was a lovely model BEB, you can certainly be proud of that. What a real shame though. You had a real contrast in ele response between power on and power off. Looking at the layout:- There would be a good blow across the elevator with power on, and far far less with power off. Do you think the fact that the vast majority of propwash would go under the tailplane with virtually none above would have an effect? I'm thinking either a pressure difference above and below, or down ele really catching the propwash and up ele seeing none. In glide, could the tailplane be masked by the wings and therefore be very ineffective? Quote Link to comment Share on other sites More sharing options...
Martyn K Posted July 7, 2016 Share Posted July 7, 2016 Hi BEB Perhaps the CG was too far forward if there was no elevator response or it was very sluggish on Elevator and Aileron Martyn Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted July 7, 2016 Share Posted July 7, 2016 I suggest having a good look over the parts and see if it may be repaired. I had a 46 inch aerobatic model suffer a mid-air. The wing was sliced in two and the fuselage badly damaged back to the leading edge of the wing, and split aft of that. It's now back flying again! Mike. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted July 7, 2016 Author Share Posted July 7, 2016 I don't think the CoG could be too far forward for a couple of reasons: 1. Where is was. ie where the instructions said to put it, was actually quite credible - likely to be neither badly forward or backward. 2. I do not see how it could become nose heavy beacuse the batteries had to be located hard up against the nose to get the CoG in the "right" place. They couldn't move any further forward. A couple of people have spoken of an unresponsive elevator - thinking about it if I've given that impression I'm sorry as strictly speaking that wasn't the case - or at least it wasn't until I cut the power! With the prop running the elevator was responsive - if fact it was damn twitchy! Symptomatic of a rearward CoG not forwards. The nose-down behaviour was a trim/rigging issue I think - not nose heaviness. My biggest regret with this model is that I didn't put the incidence gauge over the wings and tailplane priior to trying to fly it! Just my thoughts of course. We'll probably never know for sure - which is a bit unsatisfactory, but hey-ho such is life. BEB PS That Maxford Brisfit looks awfully nice (see, you can't keep a good aeromodeller down!),.... But looking at the Maxford build videos on YouTube a lot of attention is paid to the wing and tailplane incidence on it. I really don't want another exerience like the DH2! Ah, to Biff, or not to Biff. That is the question,..... Edited By Biggles' Elder Brother - Moderator on 07/07/2016 18:04:01 Quote Link to comment Share on other sites More sharing options...
Don Fry Posted July 7, 2016 Share Posted July 7, 2016 BEB is innocent! Poor person was subjected to information overload. Don't expect too much detailed explanation from the grossly overloaded brain, ( no quips please ). The only logical thought he had was to get it down in one(ish) piece. And he failed. And the bits won't tell many tales. On the plus side, a little room is freed up, and he has a spare bit of radio. After a thorough elf an safety check of said suspect kit. From bitter experience, a maiden model, with a desire to roll and dive, added to any other issue, is a one flight experience, except if luck intervenes. I did, past sense, fancy one of these. Any positives out there? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted July 7, 2016 Share Posted July 7, 2016 Had a chat with my friend who reminded me that my comment after maidening his version was that I felt it was tail heavy at the "book" C of G position and he added a substantial amount of lead to move it forward a small distance, whereupon it flew quite nicely - albeit noisily! This was with a 4500 mAh 4S battery. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 12, 2016 Share Posted July 12, 2016 Real shame that Dave - looked an interesting project ;-( Ive just received one of those sound modules, and fancy putting it in a Vampire, foamy jet ( glider ) - anyone know if there are jet "sounds" available, or if you can add your own sound files somehow ? Quote Link to comment Share on other sites More sharing options...
IanN Posted July 12, 2016 Share Posted July 12, 2016 Posted by Tim Mackey on 12/07/2016 08:27:13: Ive just received one of those sound modules, and fancy putting it in a Vampire, foamy jet ( glider ) - anyone know if there are jet "sounds" available, or if you can add your own sound files somehow ? Sounds downloadable from the supplier - although the downloads page is not particularly easy or intuitive to get to, in the first instance They do an ME 262 **LINK** Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted July 12, 2016 Share Posted July 12, 2016 Ah thanks Ian.... off to give it a go now. See what u mean about their website Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 12, 2016 Share Posted July 12, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 12, 2016 Share Posted July 12, 2016 Written by Andy Sephton, so you know it will be a cracking read Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.