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Re: Helicopters C

Posted: April 10th, 2018, 3:07 am
by vjindal

Very very impressive. Did you guys find any modifications to the FFM kit to be helpful, or were you able to get a 3 minute time without modding the original plans?
Here are a few:
1. Don't put any CF Tow on the horizontal spreaders.
2. Sand down ribs as much as possible.
3. Sand down the edges on the plastic pieces (they weigh a lot more than you might expect).

This very quickly gets you closer to 3.0-3.1 grams.
Thanks for all the help you guys!
Is not putting CF on the horizontal spreaders safe? Really don't want a near 3.0g helicopter that you spend so much time and effort into to snap right as you're trying to transfer the rubber from the winder to the helicopter

We were able to get to 3.0g using 1k tow on the spreader bars. I can't speak to whether it was necessary (I never tried without), however I will say that our helicopter still was bending considerably even with the tow due to the torque of the rubber band.

A couple other things about weight: we realized there was quite a bit of variation in the weight of Ziggy's parts. I'd recommend weighing all the parts and picking the lightest. Some parts varied by almost .1g

We also cut the tips of the triangles that hold the carbon fiber together on the blades. This cuts about .06g

Re: Helicopters C

Posted: April 10th, 2018, 11:46 am
by sciencegirl03

Here are a few:
1. Don't put any CF Tow on the horizontal spreaders.
2. Sand down ribs as much as possible.
3. Sand down the edges on the plastic pieces (they weigh a lot more than you might expect).

This very quickly gets you closer to 3.0-3.1 grams.
Thanks for all the help you guys!
Is not putting CF on the horizontal spreaders safe? Really don't want a near 3.0g helicopter that you spend so much time and effort into to snap right as you're trying to transfer the rubber from the winder to the helicopter

We were able to get to 3.0g using 1k tow on the spreader bars. I can't speak to whether it was necessary (I never tried without), however I will say that our helicopter still was bending considerably even with the tow due to the torque of the rubber band.

A couple other things about weight: we realized there was quite a bit of variation in the weight of Ziggy's parts. I'd recommend weighing all the parts and picking the lightest. Some parts varied by almost .1g

We also cut the tips of the triangles that hold the carbon fiber together on the blades. This cuts about .06g
We tried with and without the tow on the spreader bars and it is definitely a gamble. They do bow and can break without the tow. Shaving off the plastic pieces is a good idea, just don't shave too much.

Re: Helicopters C

Posted: April 10th, 2018, 11:50 am
by sciencegirl03
https://youtu.be/nn-x44gB0oA

This is our helicopters journey this year.

Let me know if you have any questions!

Nice!!! You didn't make it to Nats?

Re: Helicopters C

Posted: April 10th, 2018, 12:18 pm
by Blonded
https://youtu.be/nn-x44gB0oA

This is our helicopters journey this year.

Let me know if you have any questions!

Nice!!! You didn't make it to Nats?
Ward Meville came in 3rd. It was very close.
https://www.ezratech.us/competition/new ... es/results

Re: Helicopters C

Posted: April 11th, 2018, 6:55 am
by sciencegirl03
Has anyone noticed sag in kevlar thread? For us, it is tight on the helicopter where we build/practice, but sags at different locations- like at different schools/invitationals. I'm guessing it is not the Balsa contracting, but the kevlar sagging. Any thoughts?

Re: Helicopters C

Posted: April 11th, 2018, 9:17 am
by bjt4888
sciencegirl03,

This is usually due to difference in humidity between the location where the heli was constructed and the competition location. It is better, usually, to build in low humidity and accept sagging when competing in higher humidity locations than to build in high humidity and have materials over-tighten when competing in low humidity locations.

A practice followed in the past, for certain indoor airplane classes, to ensure this "build low humidity/fly high humidity" was to build in a "hot box" (ex. a big lightbulb heated "box building environment").

All of our helis have relatively loose Kevlar and it doesn't really hurt performance.

Good observation and question.

Brian T.

Re: Helicopters C

Posted: April 11th, 2018, 7:22 pm
by sciencegirl03
sciencegirl03,

This is usually due to difference in humidity between the location where the heli was constructed and the competition location. It is better, usually, to build in low humidity and accept sagging when competing in higher humidity locations than to build in high humidity and have materials over-tighten when competing in low humidity locations.

A practice followed in the past, for certain indoor airplane classes, to ensure this "build low humidity/fly high humidity" was to build in a "hot box" (ex. a big lightbulb heated "box building environment").

All of our helis have relatively loose Kevlar and it doesn't really hurt performance.

Good observation and question.

Brian T.
Ok, thanks! That confirms what we have been thinking too.

Re: Helicopters C

Posted: April 14th, 2018, 6:19 am
by Eureka314
My team is going to nationals, and we'll be flying there so I was wondering what's the best way to transport the helicopters to make sure they don't get damaged?

Re: Helicopters C

Posted: April 14th, 2018, 11:39 am
by glouthan
My team is going to nationals, and we'll be flying there so I was wondering what's the best way to transport the helicopters to make sure they don't get damaged?
I currently have a transport case in the works, I will post a photo of it once I finish it and I can give you the plans for how to make it... We have our state competition coming up next week and our devices will need to survive a 2-3 hr bus ride so I will let you know how it goes.

Re: Helicopters C

Posted: April 14th, 2018, 12:46 pm
by Raleway
My team is going to nationals, and we'll be flying there so I was wondering what's the best way to transport the helicopters to make sure they don't get damaged?
Secure the helicopters to a box with a packaging supporter of your choice (preferably bubble wrap). Then package all of that into a carry on and hold it for the whole ride. No other way that is as secure as that, unfortunately.