Wright Stuff C

[knightmoves]

Thanks for the response. I will look for the official FAQ and ask there.

I have no problem with whichever way it goes, I just want it to be clear.

Just be aware that you might not get a reply at all. As it happens, among the people I know who have submitted what I'd call reasonable questions, their success rate at getting any kind of response is 0%. In this case, I'd go with the people who are saying that calling a tandem a biplane would be twisting the language a bit far.

[retired1]

Call it a "stagger wing" like the ancient beach aircraft by that name.

[jander14indoor]

The Beechcraft Staggerwing still had vertical overlap, only thing unusual was top wing was behind the bottom (the technical term is negative stagger). Another example of negative stagger is the Sopwith Dolphin. I've never heard them called anything but a biplane.
Most tandem wing definitions talk about the two wings being FORE and AFT of each other.
Most biplane definitions talk about one wing OVER the other.

Take that as you will, again, not official.

Jeff Anderson
Livonia, MI

[lechassin]

Odd to have a questions section without answers

We Wiki'd "biplane" and indeed the definition specifically rules out tandem wing designs, so stacked wings and a stab it will be.

We've made a four-bladed prop hub with large cord press-in blades that allows easy pitch adjustments and slows down the unwinding on such a teeny diameter compared to a small chord two blade prop.

[jander14indoor]

Don't worry, if you ask technical questions about how to build and airplane and make it fly a long time you'll get LOTS of help.

The weasel wording is ONLY about rules interpretations. Some of us are regional, state and/or national event supervisors so we have to be particularly careful about sounding as if we are interpreting rules that have a much more complicated process than one person's opinions! Others have no standing other than experience and don't want to mislead you into doing something that harms the students.

Now, that's not to say you can't gain insight from the discussion that helps inform your decisions. Thing like pointing to definitions of possibly key words. Just can't be definitive, cause it would hold any water if it got to an appeal for example.

Jeff Anderson
Livonia, MI

[Airco2020]

We've made a four-bladed prop hub with large cord press-in blades that allows easy pitch adjustments and slows down the unwinding on such a teeny diameter compared to a small chord two blade prop.

I'm wondering if this becomes the key experimental area for this years design. Has anyone made, or seen, a prop/motor test jig of some sort? Seems like there should be a faster way to narrow down the prop shape, size, pitch and motor size combo than just going to the gym and trying every combination. I was thinking of a wingless motor stick that would be attached to something that goes in circles. Measure time or distance or thrust....Not really sure what I'm talking about but there has to be some way to narrow options before going to the gym.

[coachchuckaahs]

Airco:

You are correct in asserting the prop must be moving, as these planes will not be slow. We did this for Heli a few years ago, where stationary testing was OK because most of the flight the heli was at the ceiling. However, for props you need something to incorporate forward motion.

A circular stand that allows the MS to move forward at representative speeds would be good. You may need some means to adjust the load (perhaps sails), plus some means to measure thrust, I would think.

It may be easier to get in the gym! But, certainly advantageous to be able to screen props at home.

Coach Chuck

[lechassin]

Well, we have a flyer, a balsa biplane with max wings and stab sizes, a rudder than can be locked right or left, flat wings braced at the tips with fins to act as dihedral, 8 grams exactly. The plane is symmetrical except for right thrust.

The tail section is noticably more frail than usual for lightness, tweaked waaaay aft while maintaining CG by adding nose weight to stay right at 8 grams. Nose weight was then removed in favor of a longer motor stick that will take more winds. The plane is much longer than the span and looks unusual. We tweaked the rear hook position to keep the CG at half the motor length so that different motors won't matter.

Climbs to the left are great but in spite of the long tail and conservative CG, climbs to the right are erratic and are obviously forced in spite of right thrust. The wide, high pitched 4 bladed prop, which we need to keep rpms down, is overpowering the plane. If anyone has any insights they're willing to share in the context of a contest, we'd appreciate it. Obviously we're trying to avoid compromises like a gentler prop or lower launch torque, and the tail moment is as long as it can be using the usual materials.

Predictably, the rubber we used last year is too powerful, so we ordered some 1/16" on line. We don't know yet how much rubber the plane can carry, but hopefully the motor stick isn't too long, and we hope the thinner rubber will solve the erratic flight path right after launch.

We really don't want to go the route of stripping our own rubber, so is there a source for odd sizes we could try?

[CrayolaCrayon]

Well, we have a flyer, a balsa biplane with max wings and stab sizes, a rudder than can be locked right or left, flat wings braced at the tips with fins to act as dihedral, 8 grams exactly. The plane is symmetrical except for right thrust.

The tail section is noticably more frail than usual for lightness, tweaked waaaay aft while maintaining CG by adding nose weight to stay right at 8 grams. Nose weight was then removed in favor of a longer motor stick that will take more winds. The plane is much longer than the span and looks unusual. We tweaked the rear hook position to keep the CG at half the motor length so that different motors won't matter.

Climbs to the left are great but in spite of the long tail and conservative CG, climbs to the right are erratic and are obviously forced in spite of right thrust. The wide, high pitched 4 bladed prop, which we need to keep rpms down, is overpowering the plane. If anyone has any insights they're willing to share in the context of a contest, we'd appreciate it. Obviously we're trying to avoid compromises like a gentler prop or lower launch torque, and the tail moment is as long as it can be using the usual materials.

Predictably, the rubber we used last year is too powerful, so we ordered some 1/16" on line. We don't know yet how much rubber the plane can carry, but hopefully the motor stick isn't too long, and we hope the thinner rubber will solve the erratic flight path right after launch.

We really don't want to go the route of stripping our own rubber, so is there a source for odd sizes we could try?

You're testing earlier than most; that's for sure. This will give you an advantage over competitors in your region/state.

Zeigler sells his own custom stripped rubber on Freedom Flight, and I think there is one other source, but I can't remember currently.

I'd highly recommend the purchase of a stripper; you're essentially paying someone to cut the rubber for you + shipping. If you do order custom cut rubber, I'd recommend buying a large variety to cover the shipping.

The price of the stripper and 1/8" rubber you strip could very well be cheaper than going down the custom cut rubber path (from personal experience).

[lechassin]

Thanks for the response. I thought strippers were really expensive *cough* so I searched "Ziegler rubber stripper", and predictably the first "hit" was not family friendly... Do you have a link?

We have the plane climbing and turning both ways smoothly now but the tail is so long that a clumsy move is likely to snap it off. Total length 60cm! At least we know a nice right turn is possible. Our first stabilizer had an airfoil to maximize aft CG but a flat stabilizer is easier to trim over the wide range of speeds we're encountering. The tail moment is now so long that the rudder needs to be tiny or it is hard to trim. Having the rudder under the plane seems to help roll it to the right against prop torque.

As of now the plane is exactly 8 grams with no lead, CG seems as aft as possible, and the CG is at 50% of the motor stick, so hopefully we can keep this design and spend our [limited] time on props and motors.

For those of you that might build a lot and don't want to spend a fortune on that clear covering, the [hopefully standard] clear bags for wet bathing suits at our gym are so thin that they do not cause any weight penalty, and they're HMPE so they're strong and stick very well to a misting of 3M77 spray on the framed pieces. We found that grocery bags were a bit thicker, ergo heavier and they didn't pre-crinkle as well. Here's where we're at if anyone is interested:



We're now waiting for the thinner rubber so we can try longer motors with more winds.