Elevator Travel

[Bcone1381]

https://bearhawkforums.com/forum/bea...-model-details

Post #7 on this thread points out that the elevator travel for the Bearhawk Companion is 35 degrees instead of 30 degrees. A comment by Mark Goldberg says "Bob had us increase the elevator up to more than 30 degrees on all the models."

My plans for the Patrol says 30 degrees. Did I miss a change someplace? What precipitated the change?

[Mark Goldberg]

Bob just thought we ought to give it a little more up travel. On all the models. It is not critical to do this on your plane Brooks. The worst case scenario is BIG guy alone in the front seat with very forward CG. That BIG guy is not you.

But if there was an adjustment to achieve a little more than 30 degrees up travel it would be fine to do it. Mark

[Bcone1381]

Thanks Mark

[Flygirl1]

Although keep in mind, I think you are creating the same scenario by being low on fuel. I have found on occasion when I have been low on fuel and trying to do a full stall landing I run out of elevator before I get there. We are experimenting with VG's on the horizontal stab to help correct this.

[Chewie]

Somehow I thought you always did wheelies? Now I know why.

[Flygirl1]

Chewie, I did in the Citabria, but having flown a few thousand hours without flaps, still getting used to using them and for some reason I have not mastered the perfect wheelie in the Patrol. Also 3 point full stalls are almost effortless in this plane.

[svyolo]

My kit was delivered about 18 months ago. The control horns are mechanically limited at about 35 degrees. Seems like a degree or two shy of that, but maybe I am not measuring it from the correct place. The control horns hit a tube at that point. I don't know about older kits.

[spinningwrench]

I can get about 32 degrees on my Quick Build Patrol before the control horns hit.

[Battson]

For those who have QB kits with 30 degrees up, are we able to modify the stops in the tail (non-strutural welded tube between the longerons) to allow for more travel? Is there a Bob-approved way of doing this?

[Mark Goldberg]

It would not be hard to modify before fabric. But on a flying airplane it would seem hard to "adjust" anything. I will try to ask Bob when we speak next.
Mark

[nichzimmerman]

Regarding elevator travel, should there be control stops at the stick or are the stops at the elevator horns sufficient?

[nichzimmerman]

I just called Bob and will answer my own question. Rudder and elevator need no stops at the controls, only at the control horns in the tail. Of course, ailerons need a stop at the stick.

[Nev]

I’ve copied this across from the recent thread here,

The bell crank is not 90 degrees(it's like 96/84 or something) to the elevator and if you put them on backwards, the bellcrank will hit the empennage tube that acts as a travel limit too soon and you'll have half the deflection you need in pitch up and twice what you need in down. This results in running out of elevator for flare at slow airspeeds, especially with much of any flaps in or a forward cg. If you measure the deflection before you go fly you'll catch it if it's wrong.

The plans don't seem to call for this slight offset, but my kit is that way, as are a couple other kits I had measured when I ran into this issue.

I’ve just measured mine and the bellcrank appears to be exactly perpendicular to the elevator. Mine is a recent 4-place B model, so perhaps this is a more recent change, but an important point that you’ve raised.

I measured 37 degrees up and 19 degrees down when it hits the stops. So on mine the elevators may be interchangeable in theory, however in practice there is only way that results in the trim tabs fitting properly.

[Battson]

I measured 37 degrees up and 19 degrees down when it hits the stops. So on mine the elevators may be interchangeable in theory, however in practice there is only way that results in the trim tabs fitting properly.

This is something the CAA airworthiness inspector will almost certainly want to confirm before signoff, at least sighting evidence that you've achieved the required control defection.

[James]

An interesting thread - I didn't realise the elevators could go on backwards. As I unwrapped them from my kit, I just assigned them left and right sides, based on the drive arm for the trim tab. Obviously it had to point down.

So anyway, I checked my elevator deflection today - I get -21 down and +31 up, so that meets the numbers on page one of the plans. +37 up Nev - that sounds like maybe the more recent B model kits have had the tube moved forward a touch already?

James

[James]

File back the stopper bars, or maybe sneak a small amount out of the torque arms?

I notice that the way the torque arms are manufactured, one side has a flange and one side doesn't - so you might only be able to get more deflection one way.

Let me know if you reckon it's worth me doing anything to increase the range of travel - I'm only going with an O-360 and I weigh 80kgs, so I can't see fwd CofG being an issue for me :-)

James

[Battson]

Definitely NOT the horns (torque arms), adjust the stoppers.

[James]

Yeah Jono, my first thought was just to leave the whole setup as-is, like I said forward CofG won't really be an issue I'm thinking.
I don't want to start grinding into the tube wall.
Or maybe I might carefully stove in the tube with a rounded chisel, without bending the airframe.

[Nev]

+37 up Nev - that sounds like maybe the more recent B model kits have had the tube moved forward a touch already?

I believe so James, a recent change I think.

[PaulSA]

My quickbuild elevators came with the trim tabs welded in place ready to be cut out - so there was only one way they could fit .....

[robcaldwell]

I've been following this thread wondering if I did something wrong. Did I unintentionally swap my H stabs and elevator?... My B model kit came with the trim tabs welded in, so I think that defined the orientation for those. But can the H stabs be switched? I suppose so, but it seems to me that they are both mirror images of each other. I do think that the stabilizer struts could be swapped. Not sure if that makes a difference.

[James]

Yeah, I tried and failed to fit them one way, and then I realised that the holes had been drilled from the factory on an angle, probably deliberately, and they would only go one way.

Still the hoz stab installation was about 3/4" lower on the RH side than the left, so I just packed the LH bolt for the carry through tube down a bit, and hopefully it'll pull up with the struts and stays.

Does anyone know if the new profiled stabs have the profile symmetrical? My wooden ones are. Maybe that's the next evolution of the design :-)

James

[Archer39J]

Measured 35 up and -20 down on my B fuselage (10B), probably slightly more with the angled supports in the elevator which I didn't correct for. My trim arm interferes with full up deflection so I'll have to address that.

I recall swapping my horizontal stabilizers back and forth a time or two. The seemingly easier install had the fwd elevator profile section misaligned with the h-stab profile by about 1/4" proud when the elevator was neutral. Switching them around and everything lines up perfectly, but it was a tighter fit.

[Nev]

My trim arm interferes with full up deflection so I'll have to address that.

Mine did the same. I made a new one and drilled the arms onto the horizontal connecting tube at a slight angle to the bellcrank. So now the trim arms and the trim bell crank are not in direct alignment when viewed from the side.