Hi Guy's,

Firstly, I built my Impact during the last few month's of last year. The build was finished a few day's before Xmas day ( Great excuse to get out of the house.........Right! ). Needless to say the first proper tank of fuel was put through the model, in the air!
I should point out at this stage, that the revised/update vertical former which was included in the latest (at that time) instruction manual, had been fitted. However after landing on the second flight, I noticed a vertical crease running from the top seam to the bottom seam on the right hand side (viewed from the rear) of the fuselage but around 4" (100mm) in front of the vertical fin base former (everyone still with me?). After contacting CARF via e-mail, they replied by saying that I had experienced rudder flutter which could have been caused by loose pull/pull cables or the hinges coming loose. After checking both of these items and subsequently ruling them out, I replied with my findings to be told yet again that there must have been a failiure of some kind [&o]. I started to give more and more thought to the issue as to what could have caused the flutter in the first place. Fortunately for me there are members in our club with much more knowledge on this issue than myself so went digging for answers. I firstly spoke to one member who also flies fullsize and thankfully he agreed to look over the model for me, he agreed that there wasn't any slop in the closed loop system & that the hinges were still very much in place. Next, he commented on the fuselage aft of the wing t/e by saying "wheres the support for the fuselage?" there really needs to be a horizontal ladder type arrangement through it's length to support all the side loads exerted on the fuselage in flight, not to mention the slightly compressive nature of a traditional pull/pull cable system, things started to make sense. He then explained that the combination of the engine pulse, no aft fuselage support, compressive qualities of the closed loop and flight loads/speeds etc, could actually induce the flutter effect on the rudder, which may have started what's (rightl or wrongly) described as "panting". "Panting" has been described to me as like a rippling/wave effect travelling down each side of the fuselage until it finds a weak spot and in my case was as perivously described. I also spent many many hours in discussion with another close friend/fellow member of our club over the issue of flutter in general and realised that it it one of the most discussed issues in the aviation world and has been debated and played around with for years. Another major contender for the title of "Best possible cause" is the component weight for each moving surface, ideally the moving surfaces should at least balance on the hinge line also the hinge line arrangement can actually induce the effect as well. As I had now gathered quite a large amount of information on the subject, I decided to e-mail my findings to CARF and suggested the horizontal ladder down the length of the fuse to which they replied by saying that they would assemble another kit and fly it against their factory original during a reps meeting in the following weeks. Anyway, time passed and they eventually replied by saying that neither airframes showed any problems so therefore my claims/ideas were inconclusive. So much to my surprise, I realise that they have announced the "problem" on thier web site and have stated that the ultimate fix for the problem is guess what, a horizontal fuselage former! What a shocker [X(]. This is an EXTREMELY shortened version of the complete scenario, which did include heated exchanges between myself and a major player at their factory. My experience of their customer service is one I wouldn't like to wish on anyone, oh yes I did receive an offer of a discount on a new fuselage but have decided to decline and fix my fuselage.
Anyway, fixes are all done which include:- Horizontal balsa ladder down fuse, removed l/e from rudder and replaced with a conventional bevel edge, 5 hinge pins instead of 4, 45 degree fin brace extending to the stern post and notched in. I built a replacement rudder from basla and sheeted then covered but it came out heavier than the original [&o] so decide to run with the stock rudder and no ballast in the front mass balancer. Had two fantastic flight with it today, which included snap rolls for the first time! Still in tact .
My fellow club members shot some video of it today so hopefully I'll be able to upload it for you soon...................................watch this space!
One mans experience!?

Regards

Andy.