Any interest in a "Jupiter Giant"? - Page 4 - RC Groups
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Aug 23, 2017, 02:59 PM
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Quote:
Originally Posted by dz1sfb
Watching with interest.

Ken
So you enjoy watching train wrecks?
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Aug 23, 2017, 04:39 PM
Ken's CAD Models
dz1sfb's Avatar
Quote:
Originally Posted by Scott in NH
So you enjoy watching train wrecks?
These make great slow and fun flying models. That has been my experience with the Giant Lazy Cub.

You'll have fun not only with the aircraft, but with figuring out the design details that make things come together.

Ken
Latest blog entry: Mini H Quad Project
Aug 23, 2017, 10:24 PM
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Given the speed it'll fly at it should bounce rather than wreck, eh? (:

I mainly wanted to contrast $20 *more* to go up a few amps rating with getting a fairly reputable brand 80A esc for $25! Margins are nice, right?

With the 8" pitch prop I'd worry a bit about pitch speed, but propping up after trying it would be easy enough if needed.
Aug 24, 2017, 08:15 AM
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Quote:
Originally Posted by IridiA
Given the speed it'll fly at it should bounce rather than wreck, eh? (:

I mainly wanted to contrast $20 *more* to go up a few amps rating with getting a fairly reputable brand 80A esc for $25! Margins are nice, right?

With the 8" pitch prop I'd worry a bit about pitch speed, but propping up after trying it would be easy enough if needed.
I don't know if you fly any seaplanes/floatplanes, but there is good and bad to hitting the water!

It is generally more forgiving, but also rips things off that might have just scraped along the ground!

I like that price on the ESC, just can't handle the month long delivery, but I'll take a look and see if they have it in their US location.

I understand what you are saying about pitch speed, but Louis who is helping me on my motor thread is warning against amp draw.

He is saying 55-56A with the 23 x 8 and judicious throttle management is required with the 24 x 10 to not overload the motor.

https://www.rcgroups.com/forums/show...a-giant-foamie

Sure I could always get another prop, but at ~$40/prop I'd like to get it right the first time!

At least I believe I can now order a motor so I can locate the firewall and build the fuse....
Aug 24, 2017, 09:06 AM
I Look, Listen, and Learn
Timbo383's Avatar
Whew, $40 just for a prop, I think I'll take up wood carving.
Aug 24, 2017, 09:16 AM
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and the motor isn't in stock in the US
Aug 24, 2017, 09:17 AM
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Quote:
Originally Posted by Timbo383
Whew, $40 just for a prop, I think I'll take up wood carving.
50% off if I buy 2?
Aug 24, 2017, 02:07 PM
I Look, Listen, and Learn
Timbo383's Avatar
Quote:
Originally Posted by Scott in NH
50% off if I buy 2?
Sorry, buy 1, get 1 half off. I'm greedy.
You get the other half of the prop when I get my money.
Last edited by Timbo383; Aug 24, 2017 at 02:15 PM.
Aug 25, 2017, 11:41 AM
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Close to pulling the trigger on a G46 420kV motor, 70A ESC and 3s 8000 mah 30C battery...
Aug 25, 2017, 03:18 PM
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Didn't happen, I think I wore out the only guy who was helping on the motor thread lol!

kinda surprised me, they seem like a fiesty bunch that likes to argue, but he was the only one helping (or trying too)

Anyway during my endless questioning, I learned just enough to be dangerous and downloaded the Scorpion calc.

I figured out how to change the motor spec and how to put in my prop dimensions and I don't think the above motor has enough watts.

What do you think about going up to a 50mm motor?

http://www.headsuphobby.com/Power-Up...or_p_1537.html

it seems to solve the amperage and wattage, but does weight more than where we started by about 142 g (408 g)
Aug 25, 2017, 06:34 PM
I Look, Listen, and Learn
Timbo383's Avatar
With the size you're working with I don't think the extra grams are going to make much of a difference. Plus the extra weight might be needed up front anyways.
Aug 25, 2017, 09:43 PM
Laughs at un-boxing videos...
basicguy's Avatar
You might be surprised at the thrust with even 2s. Also the speed control will be way over what you are planning, a 20-30 amp would be enough to get the thrust you want. keep the voltage low.

As an example: I have a 400kv 200gram motor that runs a 17x8 at 16 amps on 4s. And a 95 gram 580kv that will pull a 14x8 at 10 amps on 2s.
Aug 26, 2017, 01:54 AM
Registered User
Propdrive v2 5060 380kv is in stock in US warehouse, might be an option @ $50.

(and swinging that 24x10 of course )

I see people recommending way less power than I (and I am NOT a power freak), so have I been using the right number in my calcs I wonder? I've been using an empty weight (no motor, battery or ESC) of 3200g and estimated wing area to 2.5m^2 which gives a stall speed in the ballpark of 20km/h.
Last edited by IridiA; Aug 26, 2017 at 01:57 AM. Reason: faulty statement removed
Aug 26, 2017, 09:45 AM
Registered User
I came up with about the same numbers, but used an estimated all up weight.

The stall speed is higher than I expected - safe to assume that is the power off stall speed?

I looked at that Propdrive but originally dismissed it because it was 50mm.

Once I realized that was all there was that had the power headroom (and would swing the 24 x 10 which I really want), I never circled back.

Makes sense since I need a new motor for my JJ (don't ask lol) and hate to pay $10 shipping on a $15 part
Aug 26, 2017, 09:58 AM
Registered User
Did I do this right?


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