Re: Strainers


Phil Lankford
 

You should just put the word “DON’T” on it because whoever is looking at it is already thinking about using it as a step, even though it doesn’t seem to lead to anywhere. 

Phil


On Jan 22, 2018, at 1:10 PM, Sam Hoskins sam.hoskins@... [Q-LIST] <Q-LIST@...> wrote:

 

Put a NO STEP decal on the strainers.  I once had an army officer try and use mine as a step and it broke.  Was able to fly it home and the repair was no big deal.

I say do it per plans. Like Jay mentioned, I think the reason they are close to the fuselage is to better exert torque to the elevator and torque tubes. Did you know  there was a Q-200 fatality due to failure of the mid-elevator support.  Yes, the builder did a poor job of executing that part of the construction process, but I could see a sparrow strainer adding more stress and wear to the mid-span pivot.

And yes, it is good practice to make it adjustable during flight testing.  I think the sparrow strainer design, as provided in the QAC Q-200 plans, has way too much angle of attack.

Sam Hosksins

On Mon, Jan 22, 2018 at 10:32 AM, jay@... [Q-LIST] <Q-LIST@...> wrote:
 

A few of reasons:

1. To exert the same torque, the attachment arms would have to be lengthened (to retain distance from hinge line) which would make them more fragile. I am aware of at least one incident where a strainer, built per plans, broke off in flight by shearing the attachment arms. I have beefed mine up, so even if a 10 year old stepped on it, it probably would not break.

2. The strainer trims out the moment caused by the under-camber in the trailing edge of the LS-1 airfoil. It cancels this force when in neutral trail. However, when the elevator is deflected down or up, the strainer resists this deflection. The resistance introduces additional torque that must be overcome by the torque tube. Having the strainer inboard near the attach point of the steel and aluminum torque tube doubler means less load on the foam outboard of the strainer. Maybe that is the reason that the D-fly requires an extra beef-up on the inboard end of the elevator.

3. Any assymetry from side to side has minimal roll impact when mounted inboard, not so outboard

4. Like Jim said: It works just fine where it is.

Cheers,
Jay Scheevel, Tri-Q, still building


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