Indoor News and Views

Because we’ve all been there

They say it takes a gallon of water to grow a single almond, and sometimes it feels like it takes a pound of rubber to cut a single motor to the right linear density. I think many indoor modelers know this plight, especially if you fly classes with a rubber restriction, or you as a modeler just like to maintain a fixed motor weight with any class you fly. So what do you do with all this left over rubber? Spaghetti? More new airplanes to use all that left over rubber? Preferably, you’d want to cut it right the first time, and this article details the methods I use to precisely cut rubber to the right density after many years of trial and error.

Before I dig into how to precisely cut rubber, I think it’s necessary to explain why. For decades and throughout many classes of indoor free flight models, it was, and still is, customary to compare motors to each other using a thickness measured from calipers to tell the modeler whether the rubber can deliver enough power and enough turns to the model to fly it as intended. This method has been deemed tried and true for many years by many indoor modelers. But then came the rubber restriction rules, and the need to squeeze every bit of performance out of the rubber motor became even more critical. As the rubber motors on a standard F1D got thinner and lighter, it became clear that the tried and true method of comparing rubber using thickness was starting to fall out of favor. Many flyers have since started to convert over to a linear density measurement, by which a set length of rubber is weighed, and an “average” weight per unit length is measured and used as a comparison. From one of my recent rubber cutting sessions, I plotted the strip number, which is just strips cut consecutively from the same bag/strand of my rubber batch, versus the actual cut rubber thickness for a consistent linear density. Notice that the thickness varies by almost 0.002″, or 0.051mm. Through tests I’ve found I can get just over 1322 turns in an F1D motor at 31.5 mg/in and we will then compare that target amount of turns with rubber cut using the thickness method. For this thought experiment, I’m choosing a target rubber thickness of 0.051″ to as closely as possible represent the 31.5mg/in rubber density. Using the variation in the chart below, and my handy-dandy turns versus rubber density table, I find that the lightest motor cut to 0.051″ (31.5mg/in X 0.051 / 0.052 = 30.9mg/in) will give me 1361 turns and the heaviest motor (31.5mg/in X 0.051 / 0.050 = 32.1mg/in) gives me 1291 turns. This is almost a 1:30 difference in potential flight time for an F1D! It’s clear we need a way to reliably and consistently cut the rubber to the right linear density. For competitive F1D, it is often required to be able to cut rubber down to a precision of about 0.3 mg/in (11.8mg/m).

Now to get onto how to cut rubber down to ±0.1 mg/in. Below follows a step-by-step guide for my process and some notes to keep in mind when setting up this process for yourself.

1. Calibrate your rubber stripper. For my cutting, I use a Johnson rubber stripper because the entire feed moves with one dial unlike a Harlan stripper that requires both dials to be moved to adjust the feed. While I do believe this stripping method can be setup for a Harlan-type rubber stripper, my article mainly focuses around the method itself, and a few things might need to be tailored to make this work with a Harlan stripper. When calibrating your rubber stripper, I take 4-5 consistent lengths of rubber of enough length to get an accurate mg/in measurement using a scale. For my purposes, I use 5 inch (127mm) long strips. DON’T SKIP THIS STEP! At this point, you may be thinking “Hey I’m wasting about 20 inches of rubber just for calibration?” Don’t let this thought fool you, because as long as you don’t adjust the feed width again, you likely only need to do this step once, and then recheck the calibration for the next time you need to strip rubber for a contest. You have to recalibrate any time you use a new batch of rubber that requires you to change the width of the feed on the Johnson stripper. Before I start stripping, I record each of the strips weights in a spreadsheet , number them, and use a pen to make an arrow on the strip to keep the feed direction constant in the rubber stripper. After initial recording, I cut the strips to several different dial settings that I believe will cover the range of rubber densities I want to strip from. Note: Backlash in the worm gear is very critical! When adjusting your rubber stripper, make sure you are adjusting the feed in one direction only. For example, I always adjust the dial towards smaller settings. If I need to adjust the dial to a larger setting, I make sure to back out the dial a few ticks more than required (say 0.005″), and then back it in to the dial setting you want. This will ensure the feed is sitting on a consistent side of the worm gear and minimize backlash associated error.

Now that I have my strips cut and weighed, I enter those numbers in my spreadsheet (I have my spreadsheet attached to this article), and then create a plot of Dial setting versus Actual (cut) thickness. This will then be used to preset the dial for each rubber strip individually based on their variance in weight. The blue equation shown to the right of the graph below is the calibration curve that can be used to calculate dial setting from actual thickness.

2. Precut all rubber to desired length. This process is fairly straight forward, just use the diagram in Figure 1 and cut all the rubber to the desired lengths in the same way that is done for the calibration. I use 14.00in (35.6cm) strips for F1D full motors, number them, draw an arrow to indicate feed direction, and weight them. I enter these numbers into the dark yellow boxes in my spreadsheet as seen below. The spreadsheet then calculates the dial setting in the light red box. The equations I use to calculate the dial setting can be seen below. The result is the dial setting needed to cut the rubber to the right density shown in light red in the figure below.

Raw Strip Density = Raw Strip Weight / Length

Target Strip Thickness = Target Density / Raw Strip Density * Raw Strip Thickness

Dial Setting = SLOPE * Target Strip Thickness + INTERCEPT

3. Strip the rubber and weigh the final cuts. I have a filtering tab on my spreadsheet that allows me to easily pick each strip from the largest dial setting to the smallest dial setting, set my dial appropriately, and then strip the rubber while only adjusting my dial in one direction. I weight the final result and calculate the final rubber density as seen in the green columns below. And behold! Eight strips of rubber within 0.1 mg/in of my target of 31.5 mg/in

If you have any questions, feel free to reach out to me at ameg3237@gmail.com.

~ Emily Guyett

Rubber Stripping Spreadsheet Tool (Compatible with Google Sheets)

West Baden, IN

March 26 and 27, 2022

The 3^rd annual (should be 5^th…thanks to the pandemic) is in the books.  You’ll find the results elsewhere and some of the highlights here.  This contest was well attended with 37 entries and many spectators.  There were at least 6 people entered that hadn’t been to this event before.

We knew ahead of time that there was going to be a movie premiere in the hotel atrium on Saturday night for a film shot almost entirely in West Baden.  We had agreed that the contest flying would end at 4pm on Saturday to allow the festivities to be set-up.  My wife and I walked into the hotel atrium on Friday night expecting to see our normal wide-open space, however the film company had already set-up for the premiere taking up about half of the atrium with seating, movie screen and props!  Dave Lindley (the ultimate organizer/negotiator) was on top of it and had worked out our flying area with the hotel staff.  We just had to put up with it on Saturday because it would all be gone by Sunday morning.  One benefit of the situation was that we were all invited to the premiere and could fully participate in all the activities!  All in all it didn’t turn out to be as big an issue as I thought it would.  We had a few planes land in the seating area or on props (a couple of golden devils!) but nothing we couldn’t handle.

Between the daily flying sessions we had our traditional social gathering at the German Café on Saturday night.  It was well attended with over 40 contestants and their spouses.  It’s one of the highlights of this event for me and allows for all of us to get to know each other a little better.  We thanked and toasted those who make this event possible and a couple of people who couldn’t make it this year but will always be there in spirit.

As for the flying conditions, it was the usual West Baden scenario.  Usually an inversion layer in the morning which is burned off by the sunshine in the afternoon. Even though the outside temperatures were in the 40’s the sun worked its magic each day with more sun on Sunday making for a fantastic finishing afternoon with a few new records and a couple of near records.  There were some very hotly contested events with only a few seconds separating the winners.

Alexander Welter set and reset (several times) the Sr A-6 record with a fantastic flying Gowen style A-6.  Ross Clements set a new Sr ROG Stick record with a really nice flight late on Sunday.  Nick Ray missed upping his F1R record by a mere 2 seconds!  In LPP Dave Lindley bested the field of 12 with a great flight and only 13 seconds separating 1^st and 3^rd with less than a minute between 1^st and 6^th!  The F1D event had really good scores with 4 flyers over 40 minutes.  Emily Guyett won with a great time of 49:59.  Other events that had a good number of flyers were Mini-Stick with 6 and A-6 with 12.

In the end, it was a fantastic weekend.  It was made possible by the fantastic planning and organizing of Dave Lindley and the usual hospitality of the West Baden Springs Hotel and the German Café.

Rey Mazzocco, CD

Walkalong Challenge, Round 2

First of all, “Thank You!” to all who participated in the Walkalong challenge this February/March by posting videos, challenges accomplished, & sending notes.  And to Nick Ray (INAV), Alan Petersen & Dave Lindley (NFFS) and others who got the word out and provided a means for  participants to post their results and videos.
Second, since the plan for the Hallway Harrier has come out in the March/April 2021 NFFS Digest, how about a 2nd round?  Now through the end of July.  Let’s remove some restrictions, and add some new challenges:
– Fly anywhere, not just in your home.  Things are opening up, so if you can get into a gym or auditorium, use it.  Outdoors OK too.  If you fly at an Indoor meet,  please be considerate.  Walkalongs are great for engaging visitors, kids of all ages, and spectators; but this has to be balanced with minimizing the impact to the main event.  We recommend discussing with the Contest Director ahead of time about if, where, and when it might be OK to fly walkalong gliders.  Sometimes there are adjoining rooms or hallways where walkalong flying can be conducted without stirring up the air in the main venue.
– Expanded list of challenges:

• Basic Duration – 30 second flight
• Advanced Duration – 60 second flight
• NEW – Elite Duration – 2 minute flight
• NEW – Outdoor flight of at least 30 seconds
• Closed course, 3 laps.  (It gets hard when you start Lap 2 and encounter your own wake!)
• Inflight handoffs from one pilot to another.  Complete 3 handoffs in one flight.  There are many ways to do this.  Send the glider from one pilot to the other; or have one pilot come alongside and assume control.  They can hand off the board, or each pilot can use their own board.  It takes some practice!
• Fly 30 seconds without a board, using just your hands / head / body to generate slope lift.
• Design your own walkalong glider.  This is not a one-design event!  The Hallway Harrier is offered as a design to get you started.  There are no limits on design or construction.
• NEW – Obstacle Course.  Cover at least 3 obstacles in one flight.  Obstacles could include any of the following, or make up your own.  High bar (fly over), limbo bar (fly under), hula hoop (fly through), slalom (fly zig zag through at least 4 markers set in a straight line); precision landing (on a table or countertop, or a marked ‘runway’ on the floor).  There are no fixed parameters.  Size, height, and spacing of obstacles depends very much on the location where you are flying, so make it challenging but not impossible.  Be creative and have fun!

Submit results to Indoor News and Views 

Submission Form

Results Sheet/Competition Log

As before, videos of your accomplishments are recommended but not required.  You can upload it via the results form; or post it yourself and provide the URL on the form.  You can submit it to the NFFS YouTube channel if you want: https://www.youtube.com/channel/UCucmaPRq2ws6rRTMHX_38YA
There are no restrictions on design & construction of the gliders or the boards.  But if you want a starting point, the Hallway Harrier plan is in the March/April 2021 NFFS Digest and also on the Indoor News and Views website. Some other resources are listed below.

Slater Harrison’s walkalong glider site: https://sciencetoymaker.org/walkalong-glider-airsurf-air-surfing/ – patterns for paper and foam gliders, building and flying tips, foam sheets and pre-made gliders available to order (nonprofit and supports physics education!).

Phil Rossoni’s walkalong glider site:  https://sites.google.com/site/controllableslopesoaring/ – designs, building and flying instruction, science project ideas, contest / game ideas, and videos.  Patterns for foam, paper, and stick-and-tissue gliders.Happy landings!

Click here to download a PDF of the results

15th Pikes Peak Ceiling Climb – March 21, 2021

Manitou Springs High School – Category I – Manitou Springs, Colorado

Don DeLoach, CD

Thanks to the Manitou Springs School District for allowing use of their
large gym as our “lifeboat” site for the 15th PPCC. Next year we hope to
return to the 37′ Colorado Springs Auditorium. This year the Aud. was
being used as hospital for COVID-positive homeless.

I want to first thank my very helpful friends at the CD table, Mark
Covington and Sean McEntee. Neither of these guys were PPCC contestants,
yet they selflessly devoted most of their Sunday to helping out!
Amazing, and much appreciated.

We had a great contest with some very fun flying. With 20 paid flyers
there was often periods of 10 or more airplanes in the air at once. My
best LPP flight survived two midairs and multiple dicey steers.

Chuck Andraka brought a large group of Youth up from Albuquerque, and
they cleaned up against the “experts.” Congrats, folks! Notable
performances were put in by Quinn Sorbello in hotly-contested LPP and
Monet Ramacciotti who set a Sr. record in F1M.

Rob Romash won Grand Champ for about the tenth time with a perfect score
of five firsts. Congrats Rob!

Please consider attending next year. We are working hard to keep indoor
alive in the Mountain West, but we need your support.

–DD

HLG
Don DeLoach     25.2+24.5       49.7
Rob Romash      23.2+21.3       44.5

Towline Glider
Don DeLoach     33.6+29.6       63.2
Rick Pangell    17.5+15.7       33.2

SCLG/UCLG combined
Rob Romash      21.8+24.3       46.1
Quinn Sorbello  21.1+21.3       42.4
Don DeLoach     17.4+20.0       37.4
Rick Pangell    15.9+17.3       33.2
D. Aronstein    15.2+16.6       31.8
Jerry Murphy    17.2+13.1       30.4

Tiny Glider
D. Aronstein 2.375″  12.0+11.9  23.9
Rob Romash          14.1+6.8    20.9

FAC No-Cal Scale
David Aronstein 6:01
Rick Pangell            2:53
Don DeLoach             :58

FAC Peanut
Don DeLoach             Fike    114
Rick Pangell            Fike    63

FAC WWII No-Cal Combat
David Aronstein  Gloster        1st
Don DeLoach       Spitfire      2nd
Rick Pangell      P-40          3rd

Limited Pennyplane
Quinn Sorbello  (Sr)    6:55
Don DeLoach             6:36
Anjulie Sorbello (Sr)   5:46
Josiah Rose (Sr)        5:45
Pete Steinmeyer         5:25
Rob Romash              5:23
Hannah Rose  (Jr)       5:18
Chuck Andraka           5:11
Rick Pangell            3:41
Jerry Murphy            3:32
John McGrath            3:23
Elijah Rose  (Sr)       2:23
Monet Ramacciotti  (Sr) 1:15
Montana Ramacciotti (Jr)        :49

Scraps
Josiah Rose             4:34
Michael Rose            3:50
Chuck Andraka           3:39
Elijah Rose             3:34
Monet Ramacciotti       3:27
Montana Ramacciotti     3:09
John ?                  1:48

Easy B
Rob Romash              5:48
David Aronstein 5:12
Pete Steinmeyer         5:10

Ministick
Rob Romash              5:10

P-18
John McGrath            1:51
Skilly DeLoach          1:40
Chuck Etherington       1:28
Darold Jones            1:25

Phantom Flash
Don DeLoach             4:17
Chuck Etherington       3:28
Rick Pangell            2:40

Phantom Flash Mass Launch
Don DeLoach             1st
Chuck Etherington       2nd
Rick Pangell            3rd
Jerry Murphy
Rob Romash

A-6
Rob Romash              4:43
John McGrath            4:13

F1L
Rob Romash              5:34

F1M
Monet Ramacciotti (Sr)  3:48*
Rick Pangell            1:21
Chuck Andraka           :37
*pending AMA record

P-18 Mass Launch
Skilly DeLoach   1:40   1st
Darold Jones            2nd
John McGrath            3rd
Rick Pangell            4th
Chuck Etherington
Monet Ramacciotti (Sr)
Montana Ramacciotti  (Sr)       
Rob Romash

Grand Champ – Colorado Cup
Rob Romash              17 points (5 1sts)
Don DeLoach             16 (5 1sts, 1 2nd)
David Aronstein 12 (3 1sts, 1 2nd, 1 5th)

2021 NATs Schedule

The Detroit Balsa Bugs and the Cloudbusters Model Airplane Club are honored to host the 2021 Indoor Nats at The UWM Sports Complex in Pontiac, Michigan. The contest will run from Tuesday, July 20, to Friday, July 23, 2021.

It is hoped that holding it close in time to the Outdoor Free Flight Nats will encourage Free Flighters to take advantage of attending both contests, reminiscent of years passed.

The site is an outstanding venue for Indoor Free Flight. It has a 72 foot ceiling with 66 feet to the bottom of the girders. Floor area is an impressive 80 by 125 yards; a full sized regulation soccer field with a runoff.

Measures to secure the building from drafts will be in place.

There is a food court, conference rooms and lavatories all within this complex.

The complex is relatively new and is neat, clean and in a safe neighborhood. There is ample, lighted parking adjacent to the flying site, which is designated as “Building 3.”

This site has been the location of many “Indoor Fling” contests run by these two clubs with excellent results.

The Event will run through 2/28/21

The Hallway Harrier Lightweight Walkalong Glider

Introduction by David Aronstein

As we are now in our 2^nd Indoor season to be impacted by the coronavirus pandemic, here is another building project and flying challenge that you can accomplish in your home.  This one is a Walkalong Glider.

Walkalong gliding is slope soaring, over a moving slope.  The slope is typically a cardboard or foamcore board, held by the ‘pilot’ who is walking behind & keeping the slope under the glider.  Most of my walkalong gliders are semi-scale stick-and-tissue models, fun to fly in larger areas but too fast for a house.  This one is designed to fly easily in your house or apartment.

The Hallway Harrier is named for the bird, not for the VTOL jet fighter (which was named for the bird).  Harriers are efficient gliders, like hawks.  As they cruise low over the fields, hunting for prey, their flight is a little bit like the flight of walkalong gliders. (Although they manage to do it without the help of a board!)

Building the Hallway Harrier

Build the Hallway Harrier just like any small Indoor FF model – ministick, parlor mite, Scraps, etc.  Main construction material is 1/32” square.

Wing: I like to use fairly deep camber.  If you have your own favorite airfoil, you can use that instead.  The plans show spliced dihedral joints, but feel free to make them by whatever method works for you.

Tail: The vertical tail spars are 1/32” x 1/16” for added strength and stiffness, because of the T-tail configuration. The top rib of the vertical tail is exactly the same length as a horizontal tail rib, as you will mount the horizontal tail to it.  The lower vertical tail rib is a little shorter.  The vertical tail is a bit unique, in that you only cover part of its span.  The part below the lower rib is just there for height, and should not be covered.  Also, be sure to build in the full –8 deg tail incidence as shown on the plan!  Walkalong gliders need more incidence than regular free flight models.

Assembly: After all the flying surfaces are built and covered with your favorite film, assemble in the following sequence.  First mount the horizontal tail to the top of the vertical, gluing securely on all of the contacting surfaces.  Make sure it is square as viewed from the top, and from the front (or back).  Then mount the vertical tail to the side of the fuselage, making sure it is square as viewed from the side.  Finally glue the wing to the top of the fuselage, making sure it is level with the horizontal tail, when viewed from front or back. If you absolutely don’t feel right building an indoor model without wing posts, go ahead and mount the wing on posts.  But keep them short (1/2” or less).

Click here to download a PDF of the plan.

Flying the Hallway Harrier

Trim for a smooth glide.  Noseweight is the primary adjustment.  A very slight stall in the ‘free glide’ is OK, as the influence of the board may correct that.  The goal is a straight glide.  If your model has a strong natural turn in one direction, add a small rudder tab (~1.5” high x ¼” chord, 1/64” sheet) to correct it.  

Now for the board.  There are two primary ways to launch; experiment to see which works best for you.

Walking start: Hold the glider 6” to 12” above, and with the wing 6” ahead, of the top edge of the board.  The board angle must be steep, at least 45 degrees.  Now walk at approximately the same speed as the free gliding speed.  Point the glider’s nose slightly down, and release the glider.  If the speed and launch attitude are just right, you are flying!  If the glider immediately gets ahead of you, try it faster next time.  If the glider immediately falls back behind the board, try it slower, or point the nose down more.

Free Glide start:  Alternatively, launch the glider from as high as you can reach into a free glide, then come up under it with the board.  This may be easier if you are having a hard time finding the correct speed for the first method.  As with the first method, the board must be steep.  Do not approach the glider from behind; this will only push it into a dive.  You have to come up from below the glider.

Once you get it flying, work on maintaining altitude and making smooth corrections from any disturbances.  Then work on turning, and climbing.  You turn by sliding the board to the side you want the glider to turn away from; possibly yawing and/or rolling the board as well.

My prototype initially had a taller vertical tail, fully covered.  It was very tricky to steer because once you got it turning, it would turn too much, often flying right back into the pilot or the board.  After modifying to the configuration shown on the plan, steering is much better.  Nevertheless, it is good practice to plan ahead:  as soon as you start a turn, start planning how and when you will come out of it.

Avoid the following common mistakes:

• When launching, always hold the glider from behind and below.  A common mistake is to try to launch it with one’s hand above or in front of the glider, which often results from picking up the glider after a landing.  The pilot’s hand will disturb the airflow and prevent a successful launch. 
• Keep the board steep.  Learn to recognize and avoid the common tendency to flatten the board.  You get no lift with a flat board.

Finally, since many of us Indoor modelers are fairly ‘mature’… take it easy!  This is great exercise – walking, coordination, balance, mental focus – but don’t overdo it initially.

Challenges

A straight duration contest does not really work, since walkalong gliders can theoretically stay aloft indefinitely.  So here are a few challenges to work on:

• 30 second flight
• 60 second flight
• Closed course, 3 laps.  (It gets hard when you start Lap 2 and encounter your own wake!)
• Inflight handoffs from one pilot to another
• Flying without a board, using just your hands / head / body to generate slope lift.
• Design & build your own walkalong glider.  This is not a one-design contest!  The Hallway Harrier is offered as a design to get you started.  There are no limits on design or construction.

Complete as many of the challenges as you can.  NFFS and/or INAV will host some kind of scorekeeping.  Details are TBD but should be released with this article.  If there is enough interest, we may follow up with more advanced competitions.

Designing Your Own

Short-coupled, high-tail models, and tailless models, are easiest to trim ‘on the board’.  Traditional FF configurations with long tail arms usually experience too much nose-down trim change because the tail, being closer to the board, gets more updraft than the wing.  Also walkalong gliders need more decalage than regular FF models, typically 6 to 10 degrees.  Besides basic longitudinal trim, you want the model to be easily steerable, which depends on the balance of vertical tail area and dihedral.

If you have a spare Scraps wing & tail – turn it into a walkalong glider!  You might be able to fly one on a large board as-is, just swapping out the prop for some noseweight.  But it will be easier to fly if you turn it into a T-tail configuration, bring the wing down closer to the fuselage, and of course take out all the turn adjustment. Be the first to send in a video?

Additional References and Resources

You can find a lot by searching for “Walkalong Glider” in Google or YouTube, but here are a couple of the most useful sites:

Slater Harrison’s walkalong glider site: https://sciencetoymaker.org/walkalong-glider-airsurf-air-surfing/ – patterns for paper and foam gliders, building and flying tips, foam sheets and pre-made gliders available to order (nonprofit and supports physics education!).

Phil Rossoni’s walkalong glider site:  https://sites.google.com/site/controllableslopesoaring/ – designs, building and flying instruction, science project ideas, contest / game ideas, and videos.  Several of my plans are on Phil’s site in the “stick and tissue” section.

David Aronstein, “Walkalong Gliders,” in the 53^rd Annual Report of the National Free Flight Society, Symposium 2020, pp. 101-116. (Copies available from NFFS Publications Services; email nffspubs@yahoo.com).

National Free Flight Society (NFFS) YouTube channel: https://www.youtube.com/channel/UCucmaPRq2ws6rRTMHX_38YA

Indoor News and Views (INAV): https://indoornewsandviews.com/