Best Times

[wx4caster]

We are having issues getting anything over about 50 Secs. (raw time) with our FF Chinook. We have been having some issues with weight, which we know is one of our issues, as we had to add some reinforcement to the sides to keep them from bending/breaking. Even with the carbon fiber. I was wondering what rubber band width was yielding the best results? We are using 0.109 cm rubber, but wonder if going with a thinner or thicker rubber would work better. We do not really wanna go thicker, as we are afraid that will break/bend the wide motors again. We have 10 days before state, and need to get over 65 sec to be in the conversation to win state. We took 2nd at regional, and we were beaten by a FF Chinook that stayed up 65 secs (raw time). Please help.

[Blonded]

We are having issues getting anything over about 50 Secs. (raw time) with our FF Chinook. We have been having some issues with weight, which we know is one of our issues, as we had to add some reinforcement to the sides to keep them from bending/breaking. Even with the carbon fiber. I was wondering what rubber band width was yielding the best results? We are using 0.109 cm rubber, but wonder if going with a thinner or thicker rubber would work better. We do not really wanna go thicker, as we are afraid that will break/bend the wide motors again. We have 10 days before state, and need to get over 65 sec to be in the conversation to win state. We took 2nd at regional, and we were beaten by a FF Chinook that stayed up 65 secs (raw time). Please help.

Hey! If you are using the FF Chinook kit then you should be able to hit 100 sec pretty easily. However, there are several things that will make that near impossible if you aren't aware of them. It sounds like you are not winding you rubber to full potential. I understand why you might not, it's quite scary if you are afraid of the motor supports breaking. If you use the 0.094 rubber that is tied to be a little longer (1-0.5 cm) than the length between the two places you connect them and wind it just under its breaking point, you should be able to hit 2 min raw time. If you don't have a 1:15 winder, get one. You have to wind each rubber about 600 times (40 with the 1:15 winder). You can go up to about 45-50 winds of the winder if you are careful and understand the rubber.

Also, you do not need to add more CF Tow to the Chinook, stay with the recommended amount. In addition, don't put the CF Tow on the horizontal beams, it adds too much weight and offers essentially nothing in return. Use the thread provided in the kit to support the motor sticks by making two flat x's on both side (top/bottom) of the Chinook. This will add basically no weight (0.01 ish grams if I remember correctly, it really is insignificant efficiency wise). This will bring you Chinook weight down.

You can also, for the rotors, shave the ribs down A LOT. They are adding very little weight and only need to frame the rotors. Also, Shave the edges of the plastic pieces a little, they add a lot of weight (about 1 grams, IIRC). These things will get your weight down to 3.0-3.1 grams if you're smart about it. With this reduction in weight and maximization of rubber, you can easily approach the top times of 3 minutes. It will just take time.

If you have any questions or concerns feel free to messages me and ask!

Best,
Blonded

[SluffAndRuff]

Use the thread provided in the kit to support the motor sticks by making two flat x's on both side (top/bottom) of the Chinook.

Can you clarify what you mean by this? I'm a bit confused by where the x's should go.

[Blonded]

Use the thread provided in the kit to support the motor sticks by making two flat x's on both side (top/bottom) of the Chinook.

Can you clarify what you mean by this? I'm a bit confused by where the x's should go.

Yes! You start off by looking at the motor stick below the middle (Doesn't matter how you orientate as long as you are consistent). You make a dot with a sharpie 1.5 cm down from the horizontal wood piece on both sides of the motor sticks that is below. Then, make one dot about 3-3.5 cm above the very bottom of the Chinook on both sides. There will now be four dots, use the same method used for the other pieces of thread to attach 2 more pieces of thread in this long flat x (make sure you are not warping the frame of the Chinook when you attach these pieces). This long flat x will be on the side that won't have mylar. Then, do this for the side that will have the mylar in it too. The lengths I used (1.5 cm and 3.5 cm) were based on feel, there are likely better ways of doing it. Make sure to think about where strain is the most (usually the middle of each half of the motor stick).

Also, remember that optimization of the rubber bands is the most important thing. You must practice and use flight logs of some sort! (The more you practice the less likely you are to break the Chinook).

Sorry if this was still a bit unclear. I did terribly in WIDI! Lmk if you have any questions or concerns and feel free to message me about how you have been improving! I'd love to know that I helped or not.

[SluffAndRuff]

Use the thread provided in the kit to support the motor sticks by making two flat x's on both side (top/bottom) of the Chinook.

Can you clarify what you mean by this? I'm a bit confused by where the x's should go.

Yes! You start off by looking at the motor stick below the middle (Doesn't matter how you orientate as long as you are consistent). You make a dot with a sharpie 1.5 cm down from the horizontal wood piece on both sides of the motor sticks that is below. Then, make one dot about 3-3.5 cm above the very bottom of the Chinook on both sides. There will now be four dots, use the same method used for the other pieces of thread to attach 2 more pieces of thread in this long flat x (make sure you are not warping the frame of the Chinook when you attach these pieces). This long flat x will be on the side that won't have mylar. Then, do this for the side that will have the mylar in it too. The lengths I used (1.5 cm and 3.5 cm) were based on feel, there are likely better ways of doing it. Make sure to think about where strain is the most (usually the middle of each half of the motor stick).

Also, remember that optimization of the rubber bands is the most important thing. You must practice and use flight logs of some sort! (The more you practice the less likely you are to break the Chinook).

Sorry if this was still a bit unclear. I did terribly in WIDI! Lmk if you have any questions or concerns and feel free to message me about how you have been improving! I'd love to know that I helped or not.

This was super helpful, thank you! I'm not the same as the original asker but I, too, have struggled to make the jump to 3 minutes, and this will be really useful.

[Rêveur]

Use the thread provided in the kit to support the motor sticks by making two flat x's on both side (top/bottom) of the Chinook.

Can you clarify what you mean by this? I'm a bit confused by where the x's should go.

Yes! You start off by looking at the motor stick below the middle (Doesn't matter how you orientate as long as you are consistent). You make a dot with a sharpie 1.5 cm down from the horizontal wood piece on both sides of the motor sticks that is below. Then, make one dot about 3-3.5 cm above the very bottom of the Chinook on both sides. There will now be four dots, use the same method used for the other pieces of thread to attach 2 more pieces of thread in this long flat x (make sure you are not warping the frame of the Chinook when you attach these pieces). This long flat x will be on the side that won't have mylar. Then, do this for the side that will have the mylar in it too. The lengths I used (1.5 cm and 3.5 cm) were based on feel, there are likely better ways of doing it. Make sure to think about where strain is the most (usually the middle of each half of the motor stick).

Also, remember that optimization of the rubber bands is the most important thing. You must practice and use flight logs of some sort! (The more you practice the less likely you are to break the Chinook).

Sorry if this was still a bit unclear. I did terribly in WIDI! Lmk if you have any questions or concerns and feel free to message me about how you have been improving! I'd love to know that I helped or not.

As to rubber optimization are people trying different widths not included in the FFM kits? I don't own a rubber stripper and I don't think our school can afford one, can someone give me pointers on what size rubber to buy?

[coachchuckaahs]

The width (and length) of rubber REALLY depends on your particular rotors. Small variations in pitch from one build to another greatly impact the optimal rubber width. A stripper really helps. But, to some extent, if your rubber is a bit wide, you can go to a longer piece (carry more weight, but more energy), so there is a lot you can do with a fixed rubber width. You may be able to tweak the tip pitch a bit, but you can easily ruin a rotor trying to do this. I wish there was an easily adjustable pitch on these things, rather than rebuilding or attempted tweeks. Because of the interaction between pitch and rubber width, it is hard to specify a "best" width for you to try.

For a given rubber width, find the optimal length in terms of the stopwatch. Then try a step change in width from your selection of stock widths. A stripper helps fine tune, but you can accomplish most of it by varying length within stock widths.

We are on our 4th fuselage and our 7th set of rotors. I expect we will build another set of rotors each weekend from now to Nationals, trying new ideas as we learn. We are not using the kit, so we have some flexibility in what we decide to build. One set of rotors used the full 1/8" rubber, or even slightly wider. Some have been under 3/32" rubber. Really depends on the rotors.

Coach Chuck

[Blonded]

Can you clarify what you mean by this? I'm a bit confused by where the x's should go.

Yes! You start off by looking at the motor stick below the middle (Doesn't matter how you orientate as long as you are consistent). You make a dot with a sharpie 1.5 cm down from the horizontal wood piece on both sides of the motor sticks that is below. Then, make one dot about 3-3.5 cm above the very bottom of the Chinook on both sides. There will now be four dots, use the same method used for the other pieces of thread to attach 2 more pieces of thread in this long flat x (make sure you are not warping the frame of the Chinook when you attach these pieces). This long flat x will be on the side that won't have mylar. Then, do this for the side that will have the mylar in it too. The lengths I used (1.5 cm and 3.5 cm) were based on feel, there are likely better ways of doing it. Make sure to think about where strain is the most (usually the middle of each half of the motor stick).

Also, remember that optimization of the rubber bands is the most important thing. You must practice and use flight logs of some sort! (The more you practice the less likely you are to break the Chinook).

Sorry if this was still a bit unclear. I did terribly in WIDI! Lmk if you have any questions or concerns and feel free to message me about how you have been improving! I'd love to know that I helped or not.

As to rubber optimization are people trying different widths not included in the FFM kits? I don't own a rubber stripper and I don't think our school can afford one, can someone give me pointers on what size rubber to buy?

The most simple way to get about optimizing the rubber is to try different lengths of each thickness of rubber provided in the kit. For each length find max turns till breakage then stay under (preferably very close to) that for testing. For instance, you would have a rubber piece (three, really. 1 for testing, 2 for flying) with a thickness of 0.094 cm and a length of x. Once you have this you would make 2 more sets testing out lengths a couple cm above and below what you just tested. You would do the same thing for both thicknesses. You keep testing with different lengths and widths and there, hopefully, will be a trend of higher times as you approach the optimized rubber.

I found making the rubber very frustrating because the length has to be very close to the same length (it seems). And if the lengths are off by a bit, I believe, the torques will be off (if you are doing it by winds).

If you do not feel like testing then use the 0.094 rubber with a length 2-3 cm longer than double the distance between the contact points of the rubber (very weird way to say that, sorry). And wind it 5 turns (with 1:15 winder) under max turning point (which should be about 53 with 1:15 winder).

Hope I was helpful.

Best,
Blonded

[sciencegirl03]

Any updates on best times at regionals/states?

[DHess]

Any updates on best times at regionals/states?

In Illinois, it looks like the best raw chinook times are around 1:40 but that is before state so who knows what could wind up being the top time.