Free Flight Trimming Basics #4 - Flying A Low-Winger - Boeing Monomail

[@maxfliart]

I've updated the Rubber Turns Calculator for any newcomers to FF rubber. With the way rubber can change throughout the years, this chart will give you a good place to start. Use it only as a general guide. hallmanstudio.com/rubber_turns_calculator.pdf

[@dwahnaslowdown8887]

Lovely model as always, and I do enjoy your videos. The link to your rubber calc didn't want to open in my browser. The blue text is correct (....) but the link that actually loads when you click it starts with . The "s" generates a security warning (like a mismatch) and doesn't allow the page to open. Manually removing the "s" in my address bar worked.

[@maxfliart]

Thx for the info. I've not yet heard from anyone else with that issue. Fingers crossed.

[@aeromodeller1]

The link worked for me. There are problems with this chart, too. The lines should all converge to zero turns at zero length, but they don't. The turns coefficients are not consistent along the lines or between lines. I checked three lines in two places near their ends and got values from 7.53 to 9.37. We should expect values around 11. This chart will seriously underestimate maximum turns. This is very safe, but you are not going to get enough power to climb, or you will be using much heavier motors than you should.

[@dwahnaslowdown8887]

@@aeromodeller1 Cool. The PC I was on has higher security settings. I tried it on this, a different PC, and it opens but says "!Not Secure" in the address bar. Good 'nuff.

[@TheMendipman]

Great! That last flight with the swallows was beautiful. Noel

[@NateG3678]

The absolute most beautiful KZbin channel is right here.

[@michaelwhinnery164]

Wow... I think you've got something special there, Clearly you know what you're doing because every model you build not only looks great but also flies amazing. And the Swallows love her too.

[@jimgillen5134]

looking forward to the 2024 unveiling. Greatly appreciate your modeling skills and flight trimming assessments. Makes me want to get back to it after 40+ years. Thanks for sharing!

[@anthonyevans1891]

Only just recently stumbled across this channel, but it pretty much instantly became my favorite. What an amazing place to fly. And the videos you produce really knock it out of the park. Ive done diifferent types model planes my entire life, but nothing approaching the quality of those in your videos. Youre truly a master of your craft. (think i like the Martynside the best so far)

[@JefferyHall-ct2tr]

Hi Tom!: That Monomail is a honey! If Boeing had not built the Monomail and the P-26 (their first all-metal designs) we may never have had the B-17 and B-29 during WWII! Loved seeing your Monomail fly!! Can't wait to see what it does this year!

[@sylvainponchelet4188]

Thank you for all this sharing of knowledge which allows us to better understand all the subtleties and technicalities of free flight

[@williamrobinson7435]

This is a great Monomail you've done Tom. I can see, especially in flight that the planform is relatively flat, you can well understand this bird doing unexpected things directionally, if you get gusts and currents as the no. of winds goes up; as long as the dreaded torque spiral doesn't intervene, I think some wandering characteristic can be charming, increasing the sense of the model having a mind of its own.. I'm not surprised that you deploy the DT on every flight, the loss of the beautiful Ryan must've been a sore one, but this here's a fabulous replacement. Thanks again, these trim flight vids are building up into a really comprehensive set. ⭐👍

[@GrotrianSeiler]

So serene.

[@XXfea]

Again - Thank you so very very very MUCH!!

[@aeromodeller1]

I've watched this video several times and made notes on each flight. I will put only the significant ones here. Low wing models need more dihedral for lateral balance. Swept wings contribute to lateral balance. The wheel fairings shown in the photo are not present on the plan or model. The glide looks good, going straight, we are close, but it is too short to properly judge balance. It is still recovering from the launch when it hits the ground. Launching from a higher place is better, if possible. Another approach is to trim it as a hand launched glider, with a wee bit of left rudder and launch with a right bank, high angle and fairly fast. If done properly, the plane will recover into a left circling glide from far up enough to judge a steady glide. Left pattern is preferred at low torque or under a low ceiling. But you can't fly left on high torque without eventually getting a left spiral dive. You can't get altitude outdoors on low torque. You can't use all the energy of the motor on low torque. Trim for right circle starts with trim for a large right circle in descent. Again, glide testing from shoulder height is of limited value. But that's where you must start. Then you start putting turns into the motor. The model may start going left because of the motor torque rolling the plane left, left wing down. When the wing is banked left, the aerodynamic force is tilted left and it has a left component. The combination of that force with the weight will pull the plane into a sideslip. The sideslip acting on the dihedral produces a balancing right roll, but the effect on the fin produces a left yaw. That brings the nose down. In the extreme case, the plane will not climb and may sideslip into the ground. You use these low power flights to check longitudinal balance, adding clay as necessary. You want to get the plane high enough to see how it handles in descent. Use these tests flights to set the rudder for the largest right circle you are comfortable on your field. One danger in these flights is the transition from left turn to right turn. The plane may stall in straight ahead flight. It takes more power to turn, that same power in straight flight may produce a stall. Now is time to add right thrust, gradually adding right thrust as you increase the number of turns. The idea is to have the same turning radius under power as in the glide. You have to be aggressive with the right thrust or the plane will start left under power and the risk of a power stall in transition is even worse. Left #1 2:28 It is on the edge of a stall. It climbs slightly, noses up slightly, slows, dihedral loses effectiveness, motor torque drops left wing, sideslips, nose down, gains speed and continues, repeating this action. It is very slight here, but this demands immediate action. It needs clay on the nose and that should be fixed before continuing. L#2 Plane is climbing with 30% turns, indicating that the motor is way too thick. Level flight should be at 60%-70% of maximum turns, depending on the shape of the torque curve. L#3 Still seeing that wobbly flight due to marginal stall. L#4 Still slight stall and left wing drop. Transitions to steep right descent. Something wrong here, should be fixed before proceeding. This will only get worse with more power, especially since more power will likely require more right thrust. L#5 Here we see the limit of flying left. At 43% turns. Motor torque keeps the left wing low, preventing a climb. It actually begins to climb as the power goes down. Still exhibits slight stall and left wing drop. At 8:00 we see a turn right that stalls, left wing drops, pulls out circling left, only to transition into right dive at the end. R#1 Quick right turn into the ground. R#2 Flight cut short by DT, beginning to go tightening right. Note the right spin after DT. Something is out of line. R#3 Started left, good flight. R#4 Circling left, needs more right thrust, transitions to tightening right. That must be fixed before proceeding. R#5 Similar, needs more right thrust. L#6, 7 and 8. Similar to earlier left flights, same problems. Started left, briefly transitioned right, back to left, then right again. The stall-dip and right spiral should be fixed before continuing. Looking forward to the 2024 update.

[@larstolkstam6486]

That big 8" prop cause quite a lot of torque =left turn and the more power the tigther turn = dig in to the left. I was glad you mentioned 14 min that you would try more right thrust. That is the right medicine! Then, balance with more left rudder, and fine tuning with wing warps/guerny flaps. Look into all CZ low wing scale models drawings from Lubomir Koutny and Antonin Alfery, always left turn for low wingers( more safe to fly with torquethan against), right thrust, left rudder and more negative in right wing tip than in left. For high wingers and low wingers with more dihedral right turn is correct = more heigt for given amount of power. Especially outdoors where we do not have any roof we can hit!

[@maxfliart]

Thx for sharing your experiences. BTW, the last time out in 2019, I did in fact remove 1/2" from each prop tip, so she's flying with a 7". Could also lead to using slightly thinner rubber. I'll be looking forward to having her at the field again this Spring.

[@zacharyschnepp4860]

Beautiful

[@MarkRobinson555]

Thank you for the amazing videos, fantastic planes that fly beautifully. Love the quality of the filming as well, do you use a filter on the camera lens to get that striking balance?

[@maxfliart]

Thx, Mark. No filters on this old cam...which comes from 2010 or so. It's not always spot on, especially when it goes from a bright sky, across a darker horizon, where it'll then brighten excessively for a moment or two. So I do clean things up where needed in post. Nothing too fancy, but enough to make it a bit more seamless. Thx for asking.

[@MarkRobinson555]

@@maxfliart thank you for the reply, always love the quality of your videos, as well of the models of course 😀

[@daviddavids2884]

is it possible to regulate torque (p-factor) by limiting prop rpms, via the use of a 'brake' on the prop shaft.?

[@aeromodeller1]

Torque and P-factor are not the same thing. Torque is the rotational force of the motor acting on the rear peg and propeller shaft. P-factor comes into play when the prop is not advancing along its axis, but at an angle to its axis, causing the attack angle of the blades to differ around the circumference. It is most pronounced on takeoff when the prop shaft is pointed upward, before the plane comes up to flying speed, tail dragging. No, you would never put a brake on the prop shaft. You have a limited amount of energy to fly, determined by the weight of the rubber. You do not want to waste any of that energy. There are better ways to deal with torque effects. Torque may be immediately reduced by using a motor of thinner cross section. However, this may also limit climb. Another way of dealing with torque is to add weight to one wing. This is not good because 1 it adds weight and 2 it produces a constant torque which will go the other way when motor torque goes down. Wing warp, ailerons, washin/washout produce a roll that tracks torque; as torque goes down, they go down to match. Everything in aeronautics is about balance.

[@harryspeakup8452]

If you want less torque then it's better to use less rubber cross-section (fewer strands and/or thinner rubber)

[@KlausEgge-c4s]

Thank you for sharing your knowledge and experience with us. I was wondering; the gurney flap, as it is a temporary feature, what kind of glue do you use to attach it?

[@maxfliart]

Thx, Klaus. They're easily attached with a glue stick, then can be cleanly removed to repositioned by floating a bit of rubbing alcohol on the joint. It's an easy field fix that can be used on the wing or stab & rudder. You can play with length and thickness as you dial it in.

[@KlausEgge-c4s]

Thank you.

[@brjimbo1]

Where can I find your neat background soundtracts?

[@maxfliart]

artlist.io

[@juliuscannon8911]

There was a article in the early 90 about rubber that u stretched wind at 60%then u hold a minute release 70%then 80% don't have all the info now just wanted to share

[@payres48]

Excuse my ignorance, but each time you retrieve the plane after it lands, it appears as though the tail plane has separated from the fuselage. I've noticed similar on other models of yours. Am I correct or just seeing things?

[@maxfliart]

Hi Paul. What ur seeing is a mechanism on the model called a DT or dethermalizer. The stab or tail is connected to a thin line and a timer, which allows the stab to pivot at a 45º angle at a given time...usually two minutes into the flight. This breaks the model free of a thermal, and saves the model from going out of sight. Here's an article I wrote about the DTs, which will be more clear in the explanation. www.hallmanstudio.com/DT.pdf

[@ericgillis1658]

Awesome, as always. Sorry if I missed this answer, but how do you determine max winds on the prop?

[@maxfliart]

Thx, Eric. I've included a generic rubber calculator in the description above, one that has been circulating for a number of years. I don't really know the original source...but it seems to be in the ball park for turns. Batches of rubber change from year to year, so only use the chart as a guide. The chart gives numbers that are 80% of max winds...which is the safe number to use if you fear breaking the motor at 100%. Regardless, I always use a blast tube after going past 60%. Lastly, if a motor feels right for a given model, as it did for the Monomail, I'll then take a spare motor and wind it until it breaks, outside of the model of course. This will be your 100% winds max...which only the brave go after. Surely, it could lead to a serious torque bump, and a few surprises, so proceed cautiously. Here's the link: hallmanstudio.com/rubber_turns_calculator.pdf

[@aeromodeller1]

@@maxfliartThat turns table shows about the same values for 1/8" rubber and 3/16" rubber. Note in particular at 20 strands both show 26 turns per inch. Obviously something wrong here. The numbers in the 1/8" table are consistent with my measurements for a pretty good batch of Tan II. The values for 3/16" rubber should be about 82% of those for 1/8" rubber. It is best to test your rubber, get a turns coefficient and use the turns formula to calculate turns for each motor. This number is a GUIDE that tells you when to start checking the rubber for hardening. As rubber approaches maximum stress, the polymer chains are pulled into alignment and the rubber crystallizes. You can get a feel for this by giving gentle tugs on the motor as you wind. It gets noticeably stiffer as you go up on the torque spike, just before it blows.

[@maxfliart]

@@aeromodeller1 Yeah, it does appear to be a bit off. Thx for the heads up. A flying buddy sent it my way awhile back, but I should've taken a closer look. I'll have to update it for sure. But yes, I merely wanted a general 'guide' of sorts to at least put the newbies in the ballpark. Once they start winding, they'll get a better sense of the true potential turns. I've been stopping and tugging for years, so it's good to hear that I'm not the only one. It gives u a lot of info, without going as far as using a torque meter. Surprisingly, I've seen more motors broken with torque meters than w/o...go figure...

[@aeromodeller1]

@@maxfliart Lot of things are involved. Ambient temperature, rate of winding, lube, stretch, dirt, prior use. Rubber is almost a living thing. It is a random tangle of polymer chains. It is made from tree sap.

[@collinmccallum]

thumbs up!

[@Thomas_J_Giraffamann]

👍🏼

[@brjimbo1]

Going to need some air traffic control out there.

[@mjkluck]

Goof stuff.