There has been many posts and articles on the internet about the dreaded Tail Wag on the Trex-250 and even though I thought I had it fixed as stated in my old post, I was wrong as I recently found out when I finally had the time to try to trim & tune up the heli. On higher headspeed, the tail would “blow out” as soon as I pumped (increased or decrease) the pitch/throttle. Why was this happening? I guess firstly I am partly to blame for improper setup and Align is also to blame for their release of a less than troublefree helicopter. As mine was the first original super combos around and not the later SE versions, problems on the tail was bound to occur.
This time round I tried and rectified a few things. Here’s a note to myself and to you who might be interested as to what steps I have taken so far:
1) Decided to move back to the smaller DS420 servo since it was lighter and tried to eliminate the source of the tail issue rather than to over power it with a larger 520(?) servo.
2) Ensured that the servo was properly mounted on the right side of the boom clips to ensure that the “Pushrod” was straight from the servo horn to the guide to the tail control arm. My old servo location had a bend in the push rod. By having the pushrod bent and not straight, it led to an induced “flex” in the system whenever the servo tried to push the pushrod to the tail control arm. A stiffer pushrod will help even more here. Some people have switched to higher gauge wires or carbon fibre rods.
3) Reduced the Swash Mix from 60% for Aileron/Elevator/Pitch to approximately 50%. Will lower it to 45% if the problem persists. This is actually stated in the manual which I over looked. I guess too much pitch will definately overpower the gyro.
4) Bought & changed to new carbon fibre tail blades and installed them (No this didn’t seem to make a difference to the wag but then again it seems to create less “drag” as compared to the stock curved blades which I used.
5) Bought and changed to the new METAL Tail Control Arm which is much stiffer than the stock PLASTIC control arm which flexes under heavy load which again contributes to the delay and whipping action & tail wag.
6) I already have the new weighted tail blade holders & tail blade holder hub (which still led to the tail wag issue) and I also added additional weights (nut) to the tail blade screws. It helps with lessening the load but this is still not the only source of the problem.
With the above settings, I seem to have been able to increase the GYRO travel rate from +36 to about +50 (Head Holding Mode). This was with me holding the heli and reving up the motor (without the main blades of course). With the increase, I am sure the tail would have a little improvement. Will try to fly her this weekend and see if this is what’s needed to keep her steady as I do some pitch pumps. It’s a little unnerving when the tail is so soft and doesn’t hold well. That doesn’t allow you to do much on it apart from normal forward flights. Doesn’t help when I’m trying to get comfortable with backward flips.
My latest addition to my fleet is Align’s newest micro helicopter, the TREX 250. This little baby captured my interest the first time I laid eyes on it… or rather the first time I laid eyes on the box. My next encounter with it was by reading an article on RC HELI magazine which featured the new comer. What got me interested was that the combo kit came with almost everything that you would need to get this heli up and flying except for a radio, receiver and battery. Apart from those three items, it came with everything like its very own digital servos, 3 for the cyclics and 1 for the rudder and it also comes with a high quality gyro fit even for larger birds.
The build of this heli was done over a span of 2 weeks although I believe you can actually get it done in 1 night since most of the heli was already pre-built. I took my time because I had to order LIPO batteries for it. For those of you who are short sighted and have fat fingers, do be warned… the screws and parts are really really minute! Don’t drop any screws or you’ll spend the rest of the night looking for them! Having said that… the instructions that came with the kit was pretty well written and laid out. Oh might I also add the quality of this kit is unbelievably good with its machined metal heads, carbon fibre parts and basically smooth operations of the tail drive and all head linkages.
I have just managed to fly this baby last Thursday / Friday but found that the GWS receiver which I used was prone to interference (which almost cost me to lose the chopper a few times). I have since changed it to a ‘spare’ 8CH corona receiver which seems to be doing very well.
I was also hit by the dreaded tail wag issue when gain was only set at 51% (head-holding) or 49% (non-head hold). Needless to say, the tail held terribly. I was so sure that I used the correct ‘+’ (plus) shaped horn measured at 5mm but still I decided to try to change it to the ‘o’ shaped horn which seemed to have the mounting point just slightly closer to the center than the ‘+’ shaped horn. Unbelivably, that cured the problem! So if you guys are having tail wag problems, make sure you use the right horn with the Align DS420 servo and Gyro! 5mm is the magic number. you might even want to try 4mm if there’s such a mount point! My rates are not at 65% there abouts and the tail holds like a dream. I have also set my gyro to have a delay of close to 100% since a 0% delay seemed to give me a slight wag. I think the servo might be a little too quick for the tail and gyro to keep up!
Alright that’s all I have to report for now. Btw I’m using a Zippy 1000 mAH battery that’s rated at 25C. It was a little tight for the canopy but that was cured by drilling two new holes just about 7 or 8 mm back from the original holes. The power is good but I will need to try some pitch pumps and see how well the power holds now that my tail wag problem is gone and that the tail holds rock steady!
After a period of slightly over 1 month, I finally managed to put all the needed parts together for my Yak-55. The maiden flight was successfully flown on 21 Feb 2009 under the watchful eye of my flying buddy who was well versed with the plane (seeing that he was the one who influenced us all and showed us how nice this plane flies). This plane is fully 3D capable and I hope to be able to execute some nice clean maneouvers in time to come.
Here are some pictures of my Yak-55, which is basically a 50 sized plane with the following specs:
Just managed to update the RCBuddies.com mainpage and layout plus a host of other stuff like resizing of the gallery picture thumbnails, redoing the gallery layout, updating the software for the Forum & etc.
Also changed the Meta Tags for the site so that hopefully it would not be better placed once google.com has crawled the site with the new titles and descriptions.
Just like on this Site, RCBuddies now have their own Related Videos showing on certain pages or articles. If you have any articles you wish to have placed on RCBuddies.com, do feel free to email your content to firstname.lastname@example.org
The Radio Control model forum which used to be hosted here at OPP has now been moved to its very own domain since it was a little off topic in this domain. I have decided that Ourplaypen.com will purely be a personal website.
The dedicated website for the Radio Control Forum & Gallery has been moved to its very own home at http://www.rcbuddies.com. Its about time the Forum had its own home and I’m glad to inform all members and visitors of the successful migration of all membership and forum postings to the new hosting as of yesterday (12 Feb 2008)
If you are a Malaysian Radio Control fan, do become an RC Buddy and visit us at http://www.rcbuddies.com! Is that a cool and easy to remember name or what!? I’m surprised the domain was still available for registration.