Wright Stuff C

[Rossyspsce]

Agree with everything noted by Coach Chuck.

In order to address the wing and stabilizer size and definition issues, my teams built a design with a 34.8 x 6.9 cm forward horizontal surface, with winglets and bonus markings, that is by definition the wing since the rear horizontal surface was built to 34.6 x 6.9 cm.

We were thinking that this would be the simplest configuration for the event supervisors to check in.

We technically didn’t think that we needed to build like this, just Wanted to avoid the possibility of students defending canard configuration with an ES that might not be knowledgeable of airplane design.

I posted a FAQ question related to this at the beginning of the season, as I’m sure others did also, so I’m glad a better clarification is on the official SO website finally. As an ES for our local invitational, I judged effectively the same as this clarification.

Brian T

I have a question regarding the measuring devices that comps have been using. The ones I have been to either use wood that's been laser cut or 3D printed devices, which naturally will have some margin of error. At golden gate they used a 3D printed device, that led them to state that my wing was 1mm over the 35cm, this led me to three things, 1. How was it possible for them to have measured such a small size without a micrometer or something similar? 2. What device will they use at nats? 3. What devices have others used?

[bjt4888]

Rossy,

Not sure what will be used at Nationals. When I ES, I use a poster board cut out that stands vertically a couple of inches tall (held vertical by a couple of balsa blocks). Board is stiffened and kept straight by some long pieces of 1/4” square balsa sticks bonded to each side. The cut out is 1 mm oversized (35.1cm) so that a student can reasonably put a 35 cm wing into it. I also have a 40 cm steel ruler with a small hardwood block taped in place as an endpoint. If a flying surface fits tight into the cutout, or doesn’t fit, I have the student hold the surface up to the steel ruler so that they get a second confirmation that is is oversized.

All this being said, for an invitational, I will not tier a student for 1 mm and I provide a precheck station, including sanding blocks, extra clay ballast and sharpies for labeling.

I’d definitely recommend 2 mm under span and 1 mm under chord (and stabilizer 2mm less in span than wing) to make check in smooth though. And remember that span is projected span, so, if the winglets angle out, they effectively increase span (this is tricky to measure).

My teams also setup airplanes over weight to 8.04 grams,or so.

Brian T

[jander14indoor]

I can't speak for others, but I used a 3D printed gage I modeled in CAD and posted the .stl files to thingiverse. I thought I posted about that.
Then I printed on my 3D printer and verified my intended dimensions with a set of 60cm calipers accurate to better than 0.1mm. Typically I carry said calipers to tournaments for those that don't believe my gage. And yes, printing without verifying is likely to lead to errors.

The same could be done with a CNC laser cutter. I know the owner of Retro RC uses one when he supervises a tournament. It is just not one of the toys I own...
...yet.

As an engineer on the tech committee that writes the rules, I've pushed them to be written wherever possible so simple go-nogo gages can be used. This speeds verification to the rules and improves accuracy if you build and use the gages right. Its also allowed us to eliminate impound in many events because you can check devices faster and without having to touch the device.

I mean, why do we as ES care if you build 34.9 cm or a 34.7 cm wing as long as it is 35.0 or under. (side note, this is why I hated the original 'smaller' FAQ) I can check compliance to the rules in seconds with a gage of 35.xx cm where xx is a small amount (xx to allow for measurement error and is classified so you don't try to take advantage of it, but it is small enough to make sure you don't gain an advantage). I guarantee you, if you don't fit my gage, you aren't under 35 cm.

And its worthwhile for students to make their own gages and check, one reason I posted the design. Students should do so for many reasons. To learn about gage design (a field of study in its own right). To learn how to measure precisely. And to make sure you don't challenge the ES to tier you at competition for something that could have been easily prevented!

At the national tournament expect some sort of gage (not my personal one unless you come to roller coaster), and be confident it WILL be measured carefully.

Jeff Anderson
Livonia, MI

[scilifeisgood]

For the flight log, what does flight surface adjustments mean ? It is one of the required parameters.

[Rossyspsce]

For the flight log, what does flight surface adjustments mean ? It is one of the required parameters.

The only required parameters are time, rubber size before wind up, number of turns or torque at launch. Then another 3, any of your choosing.

To address your question i think it is referring to whether the wing or stab positions were moved. Whether it be up-down, from-back, left-right or something like the angle of indicence

[Rossyspsce]

This may be kinda vague but what does a stalling plane, but still climbing plane tell me about the plane itself? By stalling plane I mean like it appears as if it might start to stall but continues to clim, then during letdown it stays in the same stalling-like angle

[coachchuckaahs]

Rossy:

That sounds like CG may be too far back. Our experience would indicate that this may be higher drag than optimal. These tandem planes don't exhibit a pulsating stall like last year's planes, but getting CG and decalage correct is clear in the times attained.

Coach Chuck

[Rossyspsce]

With state next Saturday and no time to buy parts and max a fix, how can I make a prop hangar?

[bjt4888]

Rossy,

If you order from Indoor Model Specialties (Ray Harlan) and send a follow up email right away asking for fast shipping, I’m thinking you would receive in a few days. You can also make from a stiff sheet of aluminum or cut a thin section from some good quality “channel aluminum”.

Brian T

[Rossyspsce]

Rossy,

If you order from Indoor Model Specialties (Ray Harlan) and send a follow up email right away asking for fast shipping, I’m thinking you would receive in a few days. You can also make from a stiff sheet of aluminum or cut a thin section from some good quality “channel aluminum”.

Brian T

Thank you for the suggestion, but by no time to make a fix, I will not have time this week to work on my builds, so I was hoping to finish it by tomorrow night at the latest. Would bending piano wire work?