First sunrise flights and why I NEED roll trim!

eg: stopmotion, new-york, street
First early morning flights in cold weather. My Revo had a nasty turn in it which I tried to adjust using the manual trim tab. While it was a nice calm morning to fly, the darn turn made it hard to focus on improving my skills. Wasted a lot of time on the ground adjusting a manual trim tab. I've used the roll trim feature on Larry's trainer and it's a dream compared to this. Added it to my Christmas list for this trike.

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12 Comments

  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Drew you seem to have a constant left turn on all speeds. That is not what a roll trim is mainly for. Roll trim in trikes like P&M and Revo are mainly for adjusting for roll torque that gets introduced due to change in speed or engine power. As you go from 60 mph to 100 mph, it is possible but not necessary that your trike will develop a slight turn. That can be corrected with roll trim. Roll trim should not ideally be used to correct a wing tuning issue where you have a turn in the wing at all speeds and power settings. That problem should be corrected by tuning the wing itself as a best practice. In other words learning to tune a turn in the wing is still a good skill and you should not try and take shortcuts to that. Larry can teach you how to tune a turn in the wing that exists at all speeds and power settings quite well. Make sure you understand how to do that by the time you get your license. Its a question asked in the oral portion of the exam.
  • Larry  Mednick
    by Larry Mednick 3 years ago
    On the contrary, the roll trim should take care of it so long as the turn is not too bad. If I'm not mistaken Drew bent the tab the wrong way. you bend left to make it roll right. Very counter intuitive.
  • Glade Montgomery
    by Glade Montgomery 3 years ago
    My Rival-S is so perfectly balanced it's ridiculous. Though roll balance does change slightly at different speeds, it's so moderate I can easily dial-in the perfect correction via a simple change in pointing angle of the front wheel. Regardless, I am anxiously anticipating a more elegant in-flight method for adjusting roll, so I am definitely planning to acquire Larry's motor-trimmed wheel pants. I am simply waiting for Larry to provide a price, at which point (assuming the price is as reasonable as I expect it to be), I intend to order.
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    Abid - you are 100% correct about tuning the wing correctly. Larry has this wing flying dead straight most of the time. I've posted other videos showing this. On this day it started with a bit of a left and I adjusted the manual trim tab in the wrong direction making it worse, as Larry points out. The next day I flattened out the tab and it flew dead straight again. Another session on another day it had a bit of a right turn in it! Not much and I could take it our with a slight turn of the nose wheel as Glade points out.

    The roll trim would allow me to quickly make adjustments in flight to take out slight imperfections and know right away if I was helping or hurting the situation and adjust the other way.

    My flying has been in mid 60s in high humidity to bone dry conditions in the mid 20s and everything in between. I'm sure these conditions are effecting the wing a bit. I do love my Rival-S though and wish EVERY flight was hands off stable like my friends RV9...but then again he doesn't have a fabric covered flex wing.

    I flew in KZPH in Larry's trikes with roll trim and it was a very nice feature to have. Like you said - not meant to repair imperfections in the wing but to deal with those small daily anomalies - it's nice feature to have.
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Humidity will effect the sail but it should effect both sides equally. Basically once the wing sails settles, it should not be changing so much day to day. Larry why should he be having different turns on different days after so many days. Is something moving around. Its doesn't make sense that one day he felt a left turn and the next a right. I could see if it was consistent or if it developed a turn to the left at very high cruise speeds etc.? You sure something else isn't happening. May be a hanging up BRS strap around the keel or haul-back cable being pulled to one side somehow??
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Glade that is as it should be. Your wing sail has settled in and there should be hardly any use for trim. As you say it would help when going from slow to fast and usually you will see that with a properly setup wing and trike if there is a turn going from slow to fast, it will be to the same side all the time
  • Larry  Mednick
    by Larry Mednick 3 years ago
    Abid,we have been dealing with turns showing up in wings for as long as I've been flying. And truthfully the lighter and more sensitive the wing is the more susceptible it is to picking up a turn for no good reason. When you have a very unresponsive wing you can Hang a camera off the side of it and not having a turn. So that is one of the benefits of other wings.

    But even those wings do have turns that come and go. I talked to Shane Duncan at airborne about this very subject a couple of years ago when I visited the factory. He was experiencing the same phenomenon as well and wanted to talk to me about it.

    So speaking of humidity if both sides of the sail shrink for example and especially if you've tightened up certain battens on one side of the wing and not the other as part of your tuning, the effectiveness of those tension changes will become altered as you add 1 mm to a tight batten and 1 mm to a medium tension batten. In other words those changes do not keep their effectiveness equally But in a perfect world if you had identical tension on both leading edges and identical tension on all the battens and P factor was completely zeroed out And the keel remained exactly between the two wingtips, then when the sail changed size you would not pick up a turn.

    In fact tuning your wing asymmetrically to eliminate a turn makes the wing even more susceptible to changing on a day-to-day basis.

    Most of the time the true evil has to do with the keel being offset, and reshaping battens, tightening the sail on one side are Band-Aids over getting the keel to center up and equalizing the billow of both wings. therefore using a rudder trim tab system fixes the problem at the source.

    You have been running trim tabs on your Delta Jet IIs with great success. It truly is a fantastic way to tune your wing. I suspect for wings that will respond to such a mechanism this will become the new standard moving forward. It just works too well not to use it.

    Lastly if Throttle input is causing a roll, that is something that should be adjusted in the thrust line.

    I would never want to own amother REVO without roll trim. To me it's right up there with speed trim.
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    I am not saying roll trim is un-meritted. I was just thinking that having a turn to the left one day and then without a change having a turn to the right at the same speed the next might be suspect but you know your wing better. I don't believe we had that kind of thing happen even with Reflex 11 to my re-collection. We definitely had turns but not turns switching day to day.
    Actually Todd took off the trim tab from his DJ-II because he does not need it. So the trim tab is only on one DJ-II right now. I think if I did roll trim on the fly dynamically, I would probably put it in the wing instead of the carriage somehow because of various reasons. I would definitely not say that re-shaping battens to be significantly different from one side to the other is good thing. That is indeed a band aid for an unsymmetrical sail or something.
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    Abid - before I left KZPH my wing was symmetrical. The parachute bridle was interfering with the keel pocket mobility. We fixed that and in the process took apart the wing and made sure both sides were identical from a batten perspective. The only things tweaked are the tip battens. When it flies straight and level it does so between 65-80 mph. Below and above it develops a slight turn to the left - which is not unexpected as you mention. However, there are days when the wing seems to have a mind of its own and the manual trim tab does help. The only issues: 1-having to go fly to find out you have a turn - land and adjust the trim tab and 2-fly again to see if it made it better/worse and by how much. It's a trial and error method that is effective but slow and tedious. With limited flying time available already due to shorter days and temperamental weather, every minute counts.

    So I guess if you are lucky enough to have a wing that is 100% perfect every time, great and there is no need for roll trim. However I've flown in 3 Revos (1 R11 and 2 Rival-S) and all of them needed some tweaking in flight. Nothing major just a nudge here or there. The VALUE of having something that is fast and effective IN FLIGHT which would allow me to keep flying is pretty hard to argue against.

    Of course having a wing track straight and true would be great and my first choice...but as Larry mentioned it's becoming hard to find that level of stability in these sensitive wings.
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    You should definitely get roll trim Drew. Hopefully your sail will settle in soon. It takes a few hours for the wing sail to stop stretching etc.
  • tom speirs
    by tom speirs 3 years ago
    SOMETIMES I FIND THE WAY THAT THE FRONT WHEEL IS POINTING MAKES A DIFFERENCE ........BUT THEN AGAIN WHAT DO I KNOW !!!!
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    Tom - Yep...I had a problem early on keeping the nose wheel straight. I've learned to fly with it straight now and only adjust the angle depending on if there is a turn or not. Also - how the nosewheel effects or initiates a turn is also not intuitive and take a little trial and error to figure out. Good advice to keep in mind!
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