Wright Stuff C

[nobodynobody]

to add onto the first para, it also depends on winding technique

To wind, I typically stretch it to about 3 times its length, wind to about 75% of the full torque then walk into the length of the plane while winding. I finish up winding slowly and dewind ~ 100 turns. Stretching longer than 3x its length feels like it will snap (3g of .065"). Is there anything I could do to improve that? My rubber usually snaps every 7 flights or so, what about you guys?

Edit: how often do you switch out rubber? Will using old rubber change the results while testing? Will using used rubber during a competition screw up the plane?

we've been stretching to 4x length and winding up to our target torque and slowly walking in to keep the torque at that level. We haven't been dewinding because we don't know what the max torque is lol. how do you find that?

I've just been testing different maximum torques to find what works. How many winds do you get doing that and how often does it break?

[CrayolaCrayon]

To find the max torque, simply take a short loop of the said thickness/density, and wind it to breakage; if you don't break motors, you're not winding hard enough

[lechassin]

For an event where time is unlimited, I think risking breakage is mandatory. Luke knows he's sacrificing 5-10 seconds of flight time by winding conservatively, but he's understandably concerned about launching twice in the allowed time frame and having to deal with an unexpected motor failure.

He takes about 2 minutes to wind and launch, 2 minutes to fly and retrieve, 2 minutes for the second winding and launch, for a total of 6 minutes. He can theoretically break a motor, wind another, and launch flight #2 in time, but I understand his reluctance to take that risk, at least at the regional level. He hasn't tried anything like having another team member prepare a spare motor simultaneously, that would be a necessity if he advances to State and every second counts.

With all that being said, 2000 for 3 grams of 0.065 leaves a lot of room for practice/improvement. I know we've made significant gains just with the winding tips we've gotten here (Thank You!).

[nobodynobody]

For an event where time is unlimited, I think risking breakage is mandatory. Luke knows he's sacrificing 5-10 seconds of flight time by winding conservatively, but he's understandably concerned about launching twice in the allowed time frame and having to deal with an unexpected motor failure.

He takes about 2 minutes to wind and launch, 2 minutes to fly and retrieve, 2 minutes for the second winding and launch, for a total of 6 minutes. He can theoretically break a motor, wind another, and launch flight #2 in time, but I understand his reluctance to take that risk, at least at the regional level. He hasn't tried anything like having another team member prepare a spare motor simultaneously, that would be a necessity if he advances to State and every second counts.

With all that being said, 2000 for 3 grams of 0.065 leaves a lot of room for practice/improvement. I know we've made significant gains just with the winding tips we've gotten here (Thank You!).

So how much rubber do you go through in a week or through the season? How many flights do you practice with a single motor or use a new one? Also how do you fit the 4000 winds? Sorry for the barrage of questions but I'm stressed out about how much rubber I use and wanna see if its normal.

[bjt4888]

For an event where time is unlimited, I think risking breakage is mandatory. Luke knows he's sacrificing 5-10 seconds of flight time by winding conservatively, but he's understandably concerned about launching twice in the allowed time frame and having to deal with an unexpected motor failure.

He takes about 2 minutes to wind and launch, 2 minutes to fly and retrieve, 2 minutes for the second winding and launch, for a total of 6 minutes. He can theoretically break a motor, wind another, and launch flight #2 in time, but I understand his reluctance to take that risk, at least at the regional level. He hasn't tried anything like having another team member prepare a spare motor simultaneously, that would be a necessity if he advances to State and every second counts.

With all that being said, 2000 for 3 grams of 0.065 leaves a lot of room for practice/improvement. I know we've made significant gains just with the winding tips we've gotten here (Thank You!).

So how much rubber do you go through in a week or through the season? How many flights do you practice with a single motor or use a new one? Also how do you fit the 4000 winds? Sorry for the barrage of questions but I'm stressed out about how much rubber I use and wanna see if its normal.

We’ve gone through a one-pound box of 1/8” strip rubber so far this year.

Brian T

[bjt4888]

6-8 practice flights per motor if not pushing the winds too hard. Number of turns on a particular length and density rubber motor can be determined pretty accurately using the John Barker equation that I have previously published in the Scioly forum and that Eric has actually found and reposted most recently.

Brian T

[jander14indoor]

<SNIP>The biggest issue I can see for Luke that will make or break him is little errors that end up being costly. <SNIP>

This is pretty common. One of the side benefits of science olympiad is the experience of dealing with pressure and developing strategies to manage it. One suggestion have Luke develop a checklist. Tape it to the lid of the flight box so it doesn't get lost. Then use it RIGOROUSLY. Professional pilots HAVE to use checklists because mistakes can be too critical.

<SNIP>
We’ve gone through a one-pound box of 1/8” strip rubber so far this year.

Brian T

That's probably on the high end, but you will want enough rubber so that you NEVER worry about breaking your last rubber band in a competition. 1/4 lb isn't unreasonable and will make 30 to 40 motors. At 3-4 flights, that's a fair number of flights.

Jeff Anderson
Livonia, MI

[bjt4888]

Yes, agree with Jeff. Going through a pound already this year was just an exasperated remark on my part. Sorry, not very helpful. Motors are longer this year than in the past and lots of combinations to test with the challenging little propeller and two-direction flying. As difficult as the event is this year, I do think that my teams are enjoying the challenge.

And agree with Jeff that 1/4 lb of 1/16” will make about 40 motors and get you 200+ test flights. This should be plenty for most teams for a year. Or, better yet, custom strip your own rubber from 1/8” strip stock.

A pound of 1/8” strip is about 450 ft of rubber, which is only about 70 motors and this is for all four teams that I am coaching. So, about 300+ test flights so far this year.

Brian T

[coachchuckaahs]

The flaring prop increases pitch at higher torque (launch). Higher pitch increases the speed of the air mass but moves that air less efficiently (more turbulence?). That lowers thrust and controls power stalling. As the motor runs out, the pitch decreases, so what little power remains can still move the air mass efficiently (albeit slower).

My clarification on the flaring prop. It is NOT that you want an inefficient prop! Torque does not cause a plane to climb, POWER does. In a rotational system, power equals torque times RPM. The INTENT of flaring is to present a higher load to the rubber, and slow the RPM's. The torque is the same regardless of the prop pitch, but the RPM is slowed. This reduces the power, and saves winds for a longer flight. If you flare too much, the prop will stall, beat the air, and be highly inefficient. While this will reduce climb, it wastes winds through highly inefficient propulsion, if it even flies at all.

This year the props have little load at all, and so flaring does not increase the load a lot before the prop stalls. The flaring design will allow you to improve your wind utilization somewhat, but not like other years with larger props. As you have noted, allowing more roll decreases the climb, and can help control altitude (but does not control use of winds in early flight).

More variables to try! Expand that log book!

Coach Chuck

[coachchuckaahs]

To wind, I typically stretch it to about 3 times its length, wind to about 75% of the full torque then walk into the length of the plane while winding. I finish up winding slowly and dewind ~ 100 turns. Stretching longer than 3x its length feels like it will snap (3g of .065"). Is there anything I could do to improve that? My rubber usually snaps every 7 flights or so, what about you guys?

Edit: how often do you switch out rubber? Will using old rubber change the results while testing? Will using used rubber during a competition screw up the plane?

I have seen in various forums on winding technique stretching as much as 8X original length. I have certainly seen that failure to put enough winds in at high stretch cannot be made up with winds closer to the hook, and will lead to breakage. Bill Gowen (if I recall) said once to "wind it until it screams" at full stretch, before walking in.

With this year's thin rubber, a very good "feel" of the rubber will allow you to increase winds. You will not get a good feel without breaking a LOT of rubber. You also will not develop a feel for optimal winding without changing up what you do. You may need a log book just on winding, tracking things like stretch length, torque at various points of winding, stretch at various points, etc., until you find what CONSISTENTLY gets you the most winds. Also track how many times the rubber has been used, as you will see the winds count goes up with usage, until ultimate failure.

Coach Chuck

PS: We always use new rubber for the contest, broken in with 1-2 wind/unwind cycles. We do most of our testing with partial rubber to conserve, and also because we have a lot of rubber of the appropriate thickness ranges at shorter lengths from prior years and from LPP testing.