Small Flying Arts

Warm, rather stiff breeze from the wrong direction and a crowded field (rc giant-scale glider guiders were taking advantage of the conditions) forced me to wait all afternoon til things quieted down. I was able to get two comfortable flights.

I followed OZPAF's suggestion about less incidence (a change is nearly impossible on this model) with a 1/32nd sq x 4" Gurney strip on the bottom of the stab TE. With 700 turns, I was rewarded with what can only be called a "perfect" flight of about 30 seconds. The left climbout was quite shallow, with NO hint of a stall and three circuits. Glide was also very nice - shallow and flat, turning left.

About 40 minutes later, 750 turns went in. Left climb, a bit steeper than the last flight to about 50' - again with no hint of a stall - transitioning smooth as silk to a left glide and a greased landing (this one was flown directly on our main flying field). Flight was about 40-45 seconds. About the only niggle is that the power turn could be a bit wider (~ 60 feet). Glide circle is about 80'.

Next is a light finish and canopy, then a flight with the present motor on full winds and then a bit more motor x-section (4 strands of 3/32nd).

:D :D :D

Well... the prop plug doesn't fall out from its own weight, but the added down thrust was still insufficient :| .

Last Sunday turned out to be hot, and practically breezeless, so out I went for another try. I was even able to draft my confuser guru and FB to video the "fright". 700 turns on the two-strand 1/8th x 12.5" motor produced the following:

https://youtu.be/IFcOZBf9x0k

John (OFPAF) suggested that I take out a bit of incidence and/or add a bit more nose weight. I don't care to add more down-thrust as it already looks funny, and changing the decalage will be a PITA. The glide is as near perfect as one could hope for, so it seems my best bet would be to use a Gurney strip on the bottom of the stab/elevator.

High winds forecast for the next 5 days, so I've got time to spare.

While making up some new motors for this puppy, I "discovered" that the prop plug was not fitting tight enough (actually, it falls out under its own weight!) most likely due to the shims added reducing the depth of the plug. This most likely caused the thrust trim of the recorded flights to change.

I've swapped out the shims with a full surface wedge plus a bit more, anticipating the reaction of more torque, and more depth to the plug.

Dumb boo-boo...

Finally had some REALLY decent weather yesterday with a very comfortable 72° with light and variable "breeze" (< 2ms). Just a few days earlier and lasting over two weeks, the weather had played nasty with the temps not getting over 65 :? . Got about 6 flights in, still using two strands of 1/8th SS @12.5 inches.

Started with 500 turns again. I had added a downthrust shim of 0.5mm and the flight was decent with only a slight porpoising, with the power phase still to the left. Swapping the shim to a full millimeter, the next two flights on 700 turns were as near perfect as one could hope for with good height and a right power phase, transitioning very nicely into a flat left glide - kicking myself for not videoing this one.

Turning up the to 750 brought back the porpoising, but the glide was still great. The videos are really lousy as I had to do the work myself (tho there were a lot of of club "colleagues" present) but the gist is evident, both with 750 turns.

In this vid (https://youtu.be/KB26Zy0_QWg), one can just make out the transition into glide - view both in full screen.

This one (https://youtu.be/TkkAoQaS_p0), I think I botched the launch and the model "landed" while still under power. This was after adding another small shim...

About 45 minutes later, some curious new spectators wanted to see it fly so I started to wind... noticing the the motor was badly nicked at the knot. Against my better judgement, I continued winding but stopped at 700. Launching into a dead calm, I got another picture perfect flight of about 40 seconds with the model greasing in only 3 meters away. As usual, everything is perfect when no-one is looking or taking video :| .

Looking nice so far. :)

Yesterday was finally a decent day, after 5 PM (87°F) - not beastly hot like it's been the last week, or too windy (<2ms) - so I took this puppy out for some real flight testing.

There was an impromptu "party" at the field with about 15 flyers with their better parts, and I seemed to have caused somewhat of an uproar :) , as many were not aware of my FF activities :lol: . Lots of photos were taken, delaying my getting any "work" done - but I couldn't convince any of those present to video my test flights :( .

I had re-armed the plane with 2 strands of 1/8th x 13" (3/32nd was only for the back-yard hops) starting with 150 turns. NOT enough, but did show that a bit more weight needed in the nose. Next was 200 turns with a bit of porpoising - again too short to determine if more nose weight or "down" thrust was needed, but did expose a rather tight left turn with very little altitude gain.

Upped the turns to 400. LOTS of porpoising but got some height - maybe 30 feet - and a tight left turn! As the turns ran out, it settled into a decent glide, but the remaining height was insufficient to determine HOW good.

Next was with 500 turns, a bit of weight on the right wing tip. I moved onto the main field as many were not aware that I had been flying and wanted to be able to observe. I was already fairly confident that not much could go really haywire so I obliged. The porpoising was MUCH worse (the tight turn of the earlier flights dampened the oscillations) but the plane got up a lot higher and as the turns ran out the glide looked really nice - left under power transitioning to right in the glide.

Changing to a fresh motor, I went for (almost) broke cranking in 750 turns. I had added a small shim to the prop block to reduce/cure(?) the porpoising - wasn't quite enough, but the puppy climbed up to about 100 feet - the left turn still a tiny bit too tight - where she cruised for a bit and then went into a nice glide to the right. Touched down about 50 feet from the launch with a nice greased landing. Flight was timed by one of the women at nearly 40 seconds. We were well into dusk, so I called it quits. I hope to break in my West Wings Spitfire this weekend, but temps are expected to get up to 100°F thru Monday :shock: ! I usually don't even leave the apartment when it gets over 90!

Now to paint and add the permanent greenhouse - and possibly up the motor to 4 strands of 3/32nds. AUW of the model as tested: 22.07gm. Motor weight: 2.27gm.

Me happy!

Pete,
Any further work done on the SAAB...looking forward to more post!!! Wishing you a Happy and Healthy New Year!
Sky9pilot

Very nice work, staubkorb. The prop is exceptionally well carved. Beyond my capabilities.

Cheers,
Drachen

Mounted the prop and fed a 10'" loop of 3/32nd Tan SS (hook to peg = 9 inches) and re-balanced for a midnight test at the Dustbin Industries Proving Grounds (back yard) this last Tuesday. The rubber motor is one of the ones from my peanut Mew Gull, chosen only to give the SAAB enough oompf to determine what, if anything, needed to be corrected (thrust line), and to see if the prop worked at all.

One-hundred hand turns and an already damp saggy airplane showed that the prop definitely works and that more "down" thrust needs to be worked in. Side (right) thrust is also needed - difficult due to the prop-to-boom clearance. The model climbed at a rather alarming rate and did a near "wing-over" into a dive, landing on the stone walkway. No damage other than a bruised nose plug. The model does seem to be stable, tho, and the prop will be relieved at the hub and thinned a bit more (weight reduction).

WA really surprised that the tiny motor was able to make the model climb at approx 30° angle to about 15 feet before the turns ran out :shock: :o !

Made up a pusher prop (fan method) for the SAAB and will try it out before fully finishing (relieving the hub). P/D about 1.4:1 using the article by Fred Hall and made it fairly wide-bladed to help compensate for the small diameter. Diameter is 5.8 inches, giving me about 3mm to boom contact - may have to shorten it a bit more. I thought I had a number of 1mm reverse "S" hooks but only one was found so I'll do the initial OtM prop testing with a '"diamond" version - to see if the prop works at all.

Will use a 4-strand 3/32nd inch motor for starters.