Trimming

torqueburner
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Re: Trimming

Post by torqueburner »

someusername wrote:I have been having issues with my rubber bands breaking very frequently. they will break after only 5 to 10 flights (about 1300 average winds per flight) and the rubber band is a .094 thickness.
Earlier this year, we wanted to establish the breaking point for a new batch of rubber we had received. We used a 2.01 gram loop, cut to "0.095" as marked on a Harlan stripper, which resulted in a loop length of about 15 inches. (we used this one, as it finished a bit over 2g)

This loop had been wound once to a torque of 1.0 in-oz to break it in, our usual procedure. On the second wind, it took 133 X 15 = 1995 turns, and reached a maximum torque of about 1.9 in-oz., at which point it broke. So 1300 turns seems a bit low, though perhaps the breaking point will drop if the loop has been wound hard a number of times.

One other factor that occurs to me is how much you stretch it out as you wind. If you don't stretch out far enough, the rubber will form knots that decrease its ability to maximize turns at a particular torque.
retired1
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Re: Trimming

Post by retired1 »

2 g of .094 should give a loop of 15 to 16 inches depending on orings used. That should give at least 1500 winds and not break.
Check your lube. Check the bands for nicks or scalloped edges. Pre stretch the rubber. Back up 6 or more feet to start winding.
someusername
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Re: Trimming

Post by someusername »

retired1 wrote:2 g of .094 should give a loop of 15 to 16 inches depending on orings used. That should give at least 1500 winds and not break.
Check your lube. Check the bands for nicks or scalloped edges. Pre stretch the rubber. Back up 6 or more feet to start winding.
I made the new rubber with no glue on it, so maybe that will fix the problem. On the issue of stretching rubber, I do stretch it about 3x its relaxed length, but I don't see how I would stretch it 6 feet. Wouldn't that damage the propeller?
simplicity is key...sometimes
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Re: Trimming

Post by Chris_L »

Is there any way you could wind off your plane and then attach the wound motor to both the propeller and the rear hook? This could be done on a torque meter or something else. This would make it a lot safer just in case something were to happen with your plane. And you could stretch the motor out as much as possible which would help to add winds to the motor.
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Re: Trimming

Post by torqueburner »

Chris_L wrote:Is there any way you could wind off your plane and then attach the wound motor to both the propeller and the rear hook? This could be done on a torque meter or something else.
You can make a winding stooge that mounts the torque meter at one end, and has a dock for the winder at the other. Clamp this down, and you can stretch the rubber way out, then bring it in towards the meter near the end of the wind. When nearly finished, you can dock the winder to put on the last few turns before backing off. The one shown has a nail that acts as a brake. Pull it out to hold the winder handle in place while you are transferring the motor to the plane. (Even if you had no torque meter, you can use this to wind off of the plane.)
Winding Stooge.pdf
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Re: Trimming

Post by JonB »

Anyone have advice for flying at Nationals in this huge room? If you have not seen the room: http://www.scienceolympiad2015.com/Docu ... Photos.pdf

We fly in a 24ft gym. We do not even completely know how to approach a ~60ft ceiling. Should we increase the torque with a thicker motor to get it up to the maximum height the room allows but then lose out on the winds a thinner motor would give us? This room is going to lead to some crazy times at nationals!
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Re: Trimming

Post by InfiniCuber »

JonB wrote:Anyone have advice for flying at Nationals in this huge room? If you have not seen the room: http://www.scienceolympiad2015.com/Docu ... Photos.pdf

We fly in a 24ft gym. We do not even completely know how to approach a ~60ft ceiling. Should we increase the torque with a thicker motor to get it up to the maximum height the room allows but then lose out on the winds a thinner motor would give us? This room is going to lead to some crazy times at nationals!
What I would recommend is to test different thicknesses and torques, and see how high you can get in your 24 ft gym, then try and see if you can get a similar time but having the plane fly slightly lower, this way you have data for how much (generally, this isn't linear though) torque increases your height. In my gym I can only go to about .6 in-oz of torque and then dewind to .46 in-oz in order to miss the ceiling, which is also low. But at my state, we were able to go to .9 and above, as it was a very high ceiling. This was all from data with testing rubber sizes and breaking points and heights in our ceiling.
Hope this helps!
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torqueburner
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Re: Trimming

Post by torqueburner »

JonB wrote:Anyone have advice for flying at Nationals in this huge room? If you have not seen the room: http://www.scienceolympiad2015.com/Docu ... Photos.pdf

We fly in a 24ft gym. We do not even completely know how to approach a ~60ft ceiling. Should we increase the torque with a thicker motor to get it up to the maximum height the room allows but then lose out on the winds a thinner motor would give us? This room is going to lead to some crazy times at nationals!
The best way to simulate a higher ceiling is to fly partial motors. There is a nice description of this on Ray Harlan's website: http://www.indoorspecialties.com/index1.html

You could use a half motor, as described in the article, to simulate 48 feet, or use a 40% motor to simulate 60. This would be 0.8 g of rubber with a dummy stick of 1.2 g that is 60% as long as your prop to rear hook distance. Tie up some partial loops of different rubber sizes, and optimize each for a no touch flight just up below the 24 ft. ceiling. Whichever gives you the longest flight is the size to use. As Ray says in his article, this will get you close, but the best launch torque may be a bit less or more than the partial loop suggests. And of course, there are the other factors such as temperature and loop to loop variations, etc.

In general, I think that you will want to fly slightly smaller rubber than you would use in a lower ceiling. Then, you increase the launch torque to get you to the top, and you still have lots of turns on which to cruise and descend. Another benefit of flying partial motors is that you get to see how your plane behaves when you launch it at a higher torque. Does the motorstick bend or twist, causing a problem? This would be difficult to check otherwise, unless you were willing to really bang around in the rafters. If you need to launch at a higher torque than your plane will tolerate, you might consider lowering the propeller pitch, as a lower pitch will often climb better. If you do this, of course, you will also want to downsize the rubber.

We have used this technique previously for simulating our State site, which is about 1 1/2 times the height of our gym. So we use 2/3 loops. It seems to work pretty well.
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Re: Trimming

Post by JonB »

I appreciate the replies! We will see how it goes.
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Re: Trimming

Post by DoctaDave »

When choosing rubber is it better to have the plane land with no turns remaining or have the plane land with the amount of turns remaining equal to the number of turns the rubber was dewinded. I've heard both when going through old forums flying newsletters.
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