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May 20, 2020, 09:03 AM
Registered User
Rx antenna is taped onto the top of the wing, see picture in previous post.

As for the foam absorbing water, yes it’s true that blue and pink foams are not completely impermeable, in 35+ years of construction I’ve seen that. But that happens very slowly. The plane is only on the water for seconds at a time, and only about half an inch is actually immersed, so I don’t think it’s much of a factor.

YMMV.

Cheers,
Dave
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May 20, 2020, 11:07 AM
Registered User
dbacon's Avatar
You totally tricked me on the antenna, I have to learn to be more observant.

Nice to hear the water absorption is much slower than I expected. My experiments were on small pieces of foam, so the small amount they initially absorbed might explain why I thought something that went against popular opinion. Thanks for clearing that up!

I once came across an article where they built houses on foam blocks, and pushed them around to make whole neighborhoods, and I had no faith in them, so maybe it just requires a little replacement now and then...
May 31, 2020, 11:21 PM
Registered User

A new Snowball almost flies


Thanks to this thread and all the great posts, I've built a 14" Snowball. It is made out of a 3mm foam board with paper removed that I found on AliExpress. With a 3S 500mAh battery and a A2208/17t 1100KV motor from AliExpress I'm reading 97 watts. With the battery, my Snowball weighs 224 grams or almost 8 ounces, giving me nearly 200 watts per pound with a 7x5 prop.

I had tried flying with a less powerful motor and couldn't get it off the ground. With this power system maybe it is overpowered really because my highspeed taxi tests are pretty crazy. Sorry I don't have video, but even being careful on the throttle it seems to want to spin out and the two times I tried to lift off resulted in quick crashes.

Maybe it's too heavy? The motor area is a hollowed-out pool noodle. The pontoons are built from foam board and are hollow. WIth the battery sitting right in front of the tail, it balances at the CG mark.

I see a lot of crazy looking take offs in the videos so maybe I just need to gun it and pull it into the air? I've got a fair amount of experience flying smaller and much larger planes.

Any thoughts? I plan to try again in a few days when the wind dies down. This foam is more brittle than DTF so another crash probably breaks it. Thanks!
May 31, 2020, 11:39 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by tgold
Thanks to this thread and all the great posts, I've built a 14" Snowball. It is made out of a 3mm foam board with paper removed that I found on AliExpress. With a 3S 500mAh battery and a A2208/17t 1100KV motor from AliExpress I'm reading 97 watts. With the battery, my Snowball weighs 224 grams or almost 8 ounces, giving me nearly 200 watts per pound with a 7x5 prop.

I had tried flying with a less powerful motor and couldn't get it off the ground. With this power system maybe it is overpowered really because my highspeed taxi tests are pretty crazy. Sorry I don't have video, but even being careful on the throttle it seems to want to spin out and the two times I tried to lift off resulted in quick crashes.

Maybe it's too heavy? The motor area is a hollowed-out pool noodle. The pontoons are built from foam board and are hollow. WIth the battery sitting right in front of the tail, it balances at the CG mark.

I see a lot of crazy looking take offs in the videos so maybe I just need to gun it and pull it into the air? I've got a fair amount of experience flying smaller and much larger planes.

Any thoughts? I plan to try again in a few days when the wind dies down. This foam is more brittle than DTF so another crash probably breaks it. Thanks!
I would start over and do the following :

1) Maximize the wing area .

2) Minimize the weight .

3) Leave off everything that it doesn't need to fly , such as that massive motor mount .



Here is my SnowBall(ish) RC plane :




SnowBall RC plane (2 min 56 sec)
Jun 01, 2020, 12:00 AM
Registered User
dbacon's Avatar
Have you tested the actual thrust? Best way is to suspend it by the tail, from a fish scale some other strings to keep it from twisting. Then advance the throttle, the weight should increase by about 20 - 30 ounces.

Easyist way is to hold it pointed up while someone advances the throttle - carefully - see if it becomes weightless. The prop could get you, be very careful.
Jun 01, 2020, 03:20 AM
Learning to make
Quote:
Originally Posted by tgold
Thanks to this thread and all the great posts, I've built a 14" Snowball. It is made out of a 3mm foam board with paper removed that I found on AliExpress. With a 3S 500mAh battery and a A2208/17t 1100KV motor from AliExpress I'm reading 97 watts. With the battery, my Snowball weighs 224 grams or almost 8 ounces, giving me nearly 200 watts per pound with a 7x5 prop.

I had tried flying with a less powerful motor and couldn't get it off the ground. With this power system maybe it is overpowered really because my highspeed taxi tests are pretty crazy. Sorry I don't have video, but even being careful on the throttle it seems to want to spin out and the two times I tried to lift off resulted in quick crashes.

Maybe it's too heavy? The motor area is a hollowed-out pool noodle. The pontoons are built from foam board and are hollow. WIth the battery sitting right in front of the tail, it balances at the CG mark.

I see a lot of crazy looking take offs in the videos so maybe I just need to gun it and pull it into the air? I've got a fair amount of experience flying smaller and much larger planes.

Any thoughts? I plan to try again in a few days when the wind dies down. This foam is more brittle than DTF so another crash probably breaks it. Thanks!
Your only problem is the weight.
A 14" snowball has 153 square inches of wing area ( area = π rē ).
Allowing for a cubic wing loading of around 2 ( http://www.flyrc.com/wing-load-calculator/ ), that means a 14" Snowball should have a flying weight around 2 oz (60g), give or take a few dozen grams/ half an ounce.

My 24" Snowball weighs 320g after its refurbishment/diet, which gives a cubic wing loading of exactly 2. And it's a blast to fly!

Easiest way to proceed from here is to make a larger snowball, as light as you can, and use the same gear. Your Snowball should be 20" with that weight.
If you only have that kind of 3mm foam and it's too floppy for anything bigger, I'd make another snowball, slightly bigger than 14", as light as humanly possible, with a smaller motor and battery, etc.
I should mention, a lighter snowball should be less fragile in practice. Less kinetic energy in a crash relative to foam strength.
Last edited by fossil1999; Jun 01, 2020 at 03:29 AM.
Yesterday, 10:08 PM
Registered User
Thank you all for your thoughts on my heavy little snowball. I will begin looking for more suitable foam to build a larger version, and I won't be discouraged. Thanks for the tips on checking power and for the link to the wing load calculator. That's something I was aware of but hadn't studied, and I'm enjoying calculating the wing cube loading on all of my planes. Balsa or Carbon, your videos have helped to inspire me to build slow fliers and I'm having great fun with it. Thank you!

I'll be back with the next version!

Terry
Yesterday, 10:24 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by tgold
Thank you all for your thoughts on my heavy little snowball. I will begin looking for more suitable foam to build a larger version, and I won't be discouraged. Thanks for the tips on checking power and for the link to the wing load calculator. That's something I was aware of but hadn't studied, and I'm enjoying calculating the wing cube loading on all of my planes. Balsa or Carbon, your videos have helped to inspire me to build slow fliers and I'm having great fun with it. Thank you!

I'll be back with the next version!

Terry
Looking forward to seeing your next version fly !
Today, 05:02 AM
Registered User
Thanks! I just found a couple of sheets of DTF that I had stashed in a closet and it looks like I have enough to do a 24" version if I'm careful. More to come . . .


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