Roll Trim Servo

[Vandy12]

Anybody still flying a VEZ with the KPS-15II trim servo in the wing?  My refurb project had no electric trim, so I'm about to install one.  I came across a working servo, but am curious about the 3rd (signal) wire...plans and drawings only show the simple +/- servo wires and the DPDT switch.

Not sure how I should proceed ....or maybe consider the newer RAC servo(?).

Thoughts?

[easyrider]

A Vari maybe different but in 10 years and 1,300 hrs flying a Long EZ I have never used roll trim
Easyrider

[Joe Person]

Brian,

Better way is to use the "omega"-shaped composite spring ("Wright/Hanka Spring") with something like a Allen actuator to drive it.  You make the spring yourself.  This Cozy builder's site has a good description:

http://cozy.basol.net/chapter17.htm

Trim the roll of you Eze to neutral using Gurney flaps (neutral ailerons), and install the spring system above.  Lower drag.  Have had this for 600 hours on my Eze, and it is great.

[Vandy12]

I've looked at that before - looks like a pretty ingenious design....But, I'm looking to have trim authority and not 'reset' the stick to a new neutral position.  i.e. have trim IN while still having full travel both directions of the stick.  I will research further though - thanks!

[Rick Hall]

Brian:

I may be missing something, I can be dense at times, but the Hanka roll trim "omega' hoop still allows full aileron movement via the stick, even with trim applied. I do understand setting neutral roll tendencies via Gurney flap(s) first though.

I have the build/layup schedule I can email you if you like. Aside from eliminating binding from the plans springs, the failure mode of the hoop is fairly benign. Not opposite, and full, aileron trim if a per plans bungie spring fails.

Rick

[Vandy12]

Rick - thanks for the offer - I'll take any and all inputs when trying to decide on courses of action.  If you would, please email to:

brianstrack@gmail.com

Thanks again - I'll let you know!

Brian

[Rick Hall]

If I had any brains, I'd post the drawings/pix for others

First pix is the layup/dimension schedule.
Second is mine before slotting for the clevis pin. The clevis area is ~.75" wide, the spring portion is ~.62" wide.
Third is an install in a Cozy-IV
The servo is a RAC T2-10a, mounted on a right angle bracket on the main spar.

I used a 3" PVC plumbing connector fitting for the 4" diameter. Butted (and hot glued) some 3/4" MDF onto the 3" fitting to set the height (and inner width) of the ears. packing tape, peel ply, and assortment of pins/levers/wedges/weights to hold the layup down while it cured, then I squared up one side on the table saw before removing the cured spring from the mould.

Rick

[LongEZDaveA]

I installed the stock roll trim springs between RT1 and the RT2s.  I installed a servo to position RT1 via switches on the stick.  I use the roll trim multiple times on every flight.  When you change power settings, roll trim is a must.  If you don't have roll trim installed, how can you take your hand off the stick to do essentials like reading a map or using a relief tube?  It's best to have/use roll trim such that the aircraft does not roll when you take your hand off the stick for whatever reason.  Your autopilot servo will appreciate you using your roll trim before engaging it.

[MikeD]

I have just finished making the "Wright/Hanka Spring" but with changes to the build/layup schedule because I didn't want to go out and buy a new roll of BID, I'm using up my left-overs

I have used a sandwich construction of BID and CF (I’ve reduced the BID layups and replaced with CF in the ratio of 2:1. i.e. reduced BID by 4 and replaced with 2 CF) but am now wondering if this would be too stiff.

Does anyone have a rough idea of how stiff this should be BEFORE flight testing? E.g using a spring balance to expand the spring by 1 inch, or something like that!

Regards

MikeD (U.K.)

[Rick Hall]

No idea  I can measure mine, but it'd be in inches and pounds, not millimeters and stones 

I question using carbon in a spring, as carbon is rather stiff and brittle. It apparently works in this application though, but I don't know of any flying examples. I may test Kevlar at a later date, may.

The RAC servo puts out 40 lbs, if that's important. And if the spring is too stiff, you know you can sand the hoop narrower after first flight.

Do you know of a flying canard? Compare stick force, even if on the ground. Plans bungee springs, or the hoop.

Not much, hope it helps. And do let me know if I should measure my spring. But I may need to trim mine too, so...

Rick