Wright Stuff C

[Chameleon02]

Just confused a little, is monoplane the way to go this year? Yesterday at Northview, almost every competitive team had a monoplane. The judge actually complimented us for having one of the few biplanes. Im still new so not sure if it has been discussed here or not but whats ur guys's thoughts.

[CrayolaCrayon]

Just confused a little, is monoplane the way to go this year? Yesterday at Northview, almost every competitive team had a monoplane. The judge actually complimented us for having one of the few biplanes. Im still new so not sure if it has been discussed here or not but whats ur guys's thoughts.

BJT has stated that having a biplane gives around 10% performance increase.

You can go down either road and be successful.

[coachchuckaahs]

Just confused a little, is monoplane the way to go this year? Yesterday at Northview, almost every competitive team had a monoplane. The judge actually complimented us for having one of the few biplanes. Im still new so not sure if it has been discussed here or not but whats ur guys's thoughts.

BJT has stated that having a biplane gives around 10% performance increase.

You can go down either road and be successful.

Keep in mind that a biplane has more things to line up and adjust. A poorly built/adjusted biplane will probably be worse than a monoplane due to additional drag as the surfaces fight each other. Brian's teams are excellent builders, and you can be sure they build straight. This early in the season, I am not surprised that many have monoplanes, as it is faster to get to acceptable flight. I suspect that as we get closer to Nats, the percentage of biplanes will go up.

Coach Chuck

[scioly2345]

So this weekend at LISO invy, plane went very bad for me. My plane ended up just diving to the floor immediately when I threw it
But I’m confused because in the gym at my school it flew for about 20 seconds, so I’m trying to figure out where I went wrong. I actually adjusted the rudder by a LOT to make my circle smaller (could’ve caused the dive?) and I also offset the stabilizer to the left a little bit (could’ve caused the dive?)
My theory is that these big angles in the rudder and stabilizer is what caused my plane to dive at LISO.
Any tips on how to fix at least just the stabilizer and rudder and if that could’ve caused the diving that happened.
I kept the rubber the same, the turns the same, the way I threw the same, etc etc.

[lechassin]

I suspect your plane is doing what our best flying plane does: its wings remain unwarped and centered for right and left flight, so the rudder deflection causes slight banking both ways (like any normal airplane). Increasing rudder deflection to accommodate a smaller space causes enough additional banking that we need to increase wing incidence or else we also launch into a dive. Try another 1mm decalage and see what happens. In our case we add even more incidence going to the left because of the additional banking that the prop's torque causes. Even with the additional drag this causes, that plane consistently does 1'45" to 1'50" (25' height) both ways:

https://www.youtube.com/watch?v=yju4a7rvPm8 and https://www.youtube.com/watch?v=rt8HQGQpgsQ You can easily discern the banking after launch, and increasing the rudder too much will cause a descent into the floor unless we add incidence.

In an effort to improve on these times, our test planes have offset/movable wings that keep the plane flat with the right and left circles; reasonable increases in rudder deflection no longer require an increase in incidence adjustments, but other problems have presented which have kept us from taking advantage of the increased efficiency.

I agree with the biplane risks/benefits. Ours have all been biplanes and the first one Luke built looked great but had warps in it that we couldn't resolve. He had to start over with me closely supervising the covering process and keeping everything flat/square during final assembly.

[vehicleguy]

So, what exactly are the benefits of flaring propellers? Should I focus on making one this year, considering I have a working plane and I understand all of the basics about the event?

[coachchuckaahs]

So, what exactly are the benefits of flaring propellers? Should I focus on making one this year, considering I have a working plane and I understand all of the basics about the event?

Please see (many) prior posts, some this year, lots last year.

The benefit, it made properly, is it puts a higher load on the prop at higher torque, to control the climb. The question is just how much can this little prop load before stalling?

The downside is it adds several more variables, the big one being the stiffness of the flare, then the location on the blade that you place the spar (percent flare).

But if you have a good plane already, the rest of your time, as noted many times, is spent optimizing prop/rubber combination. So you should consider flaring props as one option in your quiver as you explore these combinations.

The jury is not in yet on whether these will be a strong benefit this year. In part, that will depend on your competition facility height to obstacles.

Coach Chuck

[lechassin]

With the 3-bladed design in our DIY video, rigid 0.013"+ blades cut from Chobani yogurt pots fly 1'30" to 1'35". The same pIane with an identical prop but with 0.011" blades cut from a Propel water bottle allowed higher launch torque (less backing-off), and is the one in the videos above ,1'45" to 1'50" (our best setup so far). Yet another identical prop with 0.010" blades from a Pepsi bottle shook badly at launch torque and I thought the plane would come apart. We never flew it, and it established a lower limit for us to avoid. So we shoot for 0.011" blades, and we check each blade because the bottles can vary by 1-2 thousandths.

After we had a reliable plane, for us the flaring prop was the most satisfying single improvement. 17% increase with a single change .

[OpticsNerd]

I'm having an issue right now. So when I fly with right turns my plane stalls with high torque but then slowly transitions to a dive over about 30 seconds as the torque decreases. The strange part is that this only happens with right circles; it actually flies very nicely with left circles. I've tried adjusting the shim to change the twist of the wing and changing the angle of the rudder to change the circle radius but neither fixed the problem. I'm also 95% sure nothing is moving by a significant amount during the flight. If anyone has any ideas please tell me. I really can't afford to continue having the right turns hinder my performance at competitions.

[calgoddard]

In regard to choosing a biplane versus a monoplane under the WS 2020 rules, you may wish to consider the following comments in making your decision.

The wing loading of a biplane with two 30 cm x 8 cm wings will be significantly lower than a monoplane with only one 30 cm x 8 cm wing. The biplane should generate more lift. Therefore, assuming both airplanes weigh the same, in theory the biplane should be able to fly with a thinner, longer rubber motor and achieve higher flight times than the monoplane. However, there are a number of drawbacks to the biplane configuration.

First, the extra lift advantage of a biplane will only be fully realized if the wings are properly positioned. Normally this entails a difference in incidence between the two wings and potentially some longitudinal stagger of the lower wing. Also, the amount of vertical spacing between the two wings can be critical to achieving maximum lift. Therefore, determining the optimum positioning of the wings of a biplane will take extensive experimentation. Think about whether you will have enough gym time for such experimentation.

Second, the extra wing of a biplane and its wing posts generate extra drag. This diminishes the advantage of the extra lift generated by the second wing.

Third, the second wing of a biplane consumes part of the weight budget which might be better spent elsewhere. For example, the weight of a second wing might instead be used in a heavier motor stick that would be more resistant to bending under the load of a highly wound rubber motor. If you can’t build a biplane to near minimum weight, build a monoplane near minimum weight instead.

Fourth, a biplane is more susceptible to damage, both in flying and in transport.

Fifth, under the WS 2020 rules orbiting efficiently in opposite directions on consecutive flights will be necessary to win most competitions. Accurately changing incidence and/or wash-in between flights will be more difficult, and less reliable, on a biplane than a monoplane.

I coached students in the WS event in at least one previous season when biplanes were allowed. My team flew a monoplane and easily beat every biplane in each competition held under those rules. My team competed in one of the most competitive regional and state competitions nationwide in terms of all the flying events, and especially, the WS event.

In conclusion, like everything else in indoor duration rubber powered free flight, the choice of the configuration of the air frame, e.g. biplane versus monoplane, involves trade-offs.