A quick follow-up on the T-28.  Over the last several years I've been tweaking and trimming on it.  After having the wing break instead of popping off a couple of times I rebuilt the wing mount, increasing incidence slightly and beveling the rear former so the wing would slide off cleanly in a tip impact.  I made a new noseblock with a Gizmo Geezer nose button so I didn't have to fiddle with shims.  I've pretty much settled on a ~16g motor made up of 1x36" loop of 1/8" plus 1/36" loop of 3/16" rubber, which will safely take up to 1800 turns and seems to pull the model up nicely.

I flew it in fairly windy conditions last Sunday at the Lone Star Squadron's Spring Opener meet in Gainesville TX.  It handled the winds nicely, best flight was 80 seconds with some help from rising air.  A bit of video from that flight is at:  https://www.youtube.com/watch?v=KV3tm4Tv-aw&t=235s

Mike

That would be great Mike.  I'm sure we'd all like what you put together.
Tom

I vote for that too! With Mike's upcoming Wendell Williams racer maybe that would be our demo candidate. How about it Mike?
signed,
The peanut gallery

On-top of the model being exceptional, the stab incidence adjustment screws are fantastic. I need to keeps these photos handy when I build.

Bob

The strings are static discharge wicks to mitigate RF noise generated by electrical discharge from the flying surfaces when flying in certain precipitation conditions (see https://en.wikipedia.org/wiki/Static_discharger).  On the model they are just short lengths of sewing thread with a blob of canopy glue on one end and a little folded strip of tissue on the other to simulate the mounting hardware.

Interesting thing - on the real aircraft the wicks on the left surfaces are on top, on the right they are on the bottom (see picture).  I'm guessing this is because the elevators and ailerons are interchangeable side-to-side, but I could be completely wrong...

AK, I measured the incidences using a pair of l-squares and a ruler, then used my 20th-century trig to calculate the incidence angle.  There are some simple-to-make incidence meter designs floating around, I just haven't invested the time to make one yet.

Cheers,

Mike

alfakilo wrote on Jul 30^th, 2018 at 7:13am:



Tom's already answered a couple of your questions - here's a little more:
1 - Oz-in is a measure of torque - it's a more reliable way of tracking how much energy you've put in the model.  Since the rubber doesn't completely return right away from a winding you'll get less torque at the same number of turns on subsequent windings of the motor.  Using the trimming tips Tom linked you can find out what torque overcomes the model's stability, and wind to under that torque regardless of the length and thickness of the motor you're flying with.

2 - The stab is adjustable using 0-80 nylon screws.  On this model there are two screws holding the stab to the model at the stab's spar, and one screw at the front that adjusts the angle of the stab (see pics).

3 - The Gurney flap under the left wing is there to keep the left wing up as the model turns left.  Glide testing showed the model wants to turn left, so I put the Gurney on to tame that a bit and try to keep it from rolling into that turn in the initial burst of power at launch and climbout.

There are lots of great trimming methods - peruse the NFFS Tech Library at https://freeflight.org/library/technical-library/ and the Pensacola Free Flight Team archives at http://volareproducts.com/?page_id=1686 for all kinds of great hints, tips and knowledge from folks much smarter and more experienced than me...


Cheers,

Mike

Absolutely outstanding, Mike!   You've created another winner for certain.

Neal

My gosh, Mike your T-28 is EXCEPTIONAL! Viewing your video and pictures posted have left me in a more than elevated state of bliss and amazement. In particular the pic entitled "flyout".
Kudos Mike!

Neo
"The Envious"