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lechassin wrote: ↑September 16th, 2019, 8:05 pm

coachchuckaahs wrote: ↑September 16th, 2019, 4:49 pm One thing I notice on your prop is the blades are behind the spar. If you put them ahead of the spar, you will get some flaring, which will help control climb (though the effect may be limited this year). Also, we have used "beer cups" for props with success, and did not need any reinforcement, even at a larger size.

The prop on the first plane had the blades in front but with the high rpms, any impact contact broke them free. I decided to put the blades behind the spar and reinforced the glue joint with fiberglass cloth so we could fly more and not worry about repairs. Hopefully we can revisit the four blade flaring prop as we increase the plane's stability and master height control.

This will cause reverse flaring (lower pitch at higher torque), which will make your early climb worse.

If you are using plastic cups, rough up the cup surface with 220 grit sandpaper, then glue with thin CA to your spar. We have not had issues with blade separation doing this in the past.

Coach Chuck

Xiangu,

Make the cut for the blade tips using a drawing compass, or digital equivalent, to be sure that the propeller fits within an 8 cm diameter circle.
An 8cm dia hole in a piece of poster board will be the typical measuring device used by Event Supervisors. As Coach Chuck noted above the 15 cm dia Ikara trimmed to 8 cm is a good start.

As for blade shape for custom propellers, look at plans for AMA class "A-6" for ideas.

Brian T

K,

For motor stick length, keep in mind that a long tail moment allows reduced decalage angle which improves efficiency. Knowing this, and knowing that the nose will be quite long in order to create a workable CG (nose is long because of the tiny lightweight prop) gives clues to possible successful motor stick length and tailboom length.

I'm using 5% and 3% arcs in my prototype for wing and stabilizer airfoils. 5% is 5/32" arc height for 3.14" wing chord.

Brian T

K,

Sorry, didnt notice that Coach Chuck had already answered. Our recommendations are pretty similar.

BT

There are some excellent recommendations on this thread by some very knowledgeable indoor fliers. However, some teams may be obsessing over details rather than focusing on the big picture under the WS 2020 rules.

A near perfectly performing WS 2020 airplane that can only circle in one direction is probably not going to beat a rather ordinary performing WS 2020 airplane that can successfully orbit in both directions and achieve the two-flight total bonus at the competition.

Once you have a WS 2020 model that can reliably orbit in both directions with a predetermined quick adjustment between flights, you can start focusing on optimizing the prop design and/or the rubber motor sizing. Start with a monoplane and try to get it to circle left for 60+ seconds and then circle right for 60+ seconds. Only if you can accomplish this goal would I try adding a second wing to see if a bi-plane can: 1) reliably orbit in opposite directions; and 2) produce a significant advantage in flight time over a mono-plane. You should have little difficulty building a sturdy monoplane that meets the WS 2020 rules that weighs close to the 8-gram minimum weight. Don’t bother testing a bi-plane unless you can build one that also weighs near the 8-gram minimum weight.

I am impressed by the very early work on WS this season. Keep up the good work!

Where do you guys test your airplanes? I've tried a few different locations but can't seem to find a good fit. Thanks!

noelle.darcy wrote: ↑September 17th, 2019, 8:08 pm Where do you guys test your airplanes? I've tried a few different locations but can't seem to find a good fit. Thanks!

Do you have a gym that you can use? Basically I think anywhere indoors with a large empty space/reasonable height would work.

Welcome to the forums btw

Thanks! Sadly, we don't really have a gym because we're a small school. Two years ago I was able to test the heli in my friend's house since her ceilings were 30 feet and then last year, I tested in the library but it didn't work too well. I'll try to see if I can find a gymnasium that will allow me to do it!

You might find a church with a gym or hall-like space with a high enough ceiling, or maybe a theater. The theater would be far from ideal, because rows of seats probably means you'll destroy the plane on landing. But maybe you can snatch it out of the air first. What about an indoor soccer place or something?

I agree that this event is quite challenging for people without access to school gyms.

A diagram for Wright Stuff has been posted to the national website.