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Old Jan 03, 2004, 02:40 PM
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Va.
Joined Mar 2003
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Help me design a fast Li-Po Projeti

Been flying a Mega-4 powered yellow Projeti with 10 HE 1100 cells & need more speed.

Over the past 2 yrs, I've tried many planes & a few of them exceeded my abilites. I find the flying characteristics of the Projeti fit me better than any hi-performance plane tried so far. Having never used Li-Po cells, I've decided to build the fastest Projeti I can using li-pos.

Only brushless I've used is the mega-4. What motor/li-po pack do
you think would take the Jeti to its limits & still give reasonable flt duration ? Anybody using li-pos with the Jeti ?
Will it balance w/o adding weight ? I know the motor mount will
need re-inforcement, never used fiberglass b-4 so thoughts re
this will be appreciated.

This will be a good winter-time project & I have a new Reno Pro
Jeti just waiting to go fast. Thanks for your thoughts.

Ed
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Old Jan 03, 2004, 03:51 PM
Master of Nothing!!!
ginsu1797's Avatar
Orange county
Joined Nov 2002
511 Posts
Looky here
BPP Projeti, onboard vid.

I used that as my inspiration for my Microjet.
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Old Jan 04, 2004, 05:55 PM
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Va.
Joined Mar 2003
333 Posts
Nice video Troy, pardon my ignorance but is the Kokam battery
a Li-Poly battery pack ? If so, what configuration is it ? ie is it
3s2p etc ? What Mega are you using -2, -3 or -4 ?
I'm thinking about a -3 with the best suited Li-Po pack. I've
heard of E-tec, Thunder-power etc. just need to know what
configuration li-po pack would be best. I'm not hung up on Mega
either, it theres a better brushless match for the pro-jeti, I'm
all ears.

I think I can handle the "worlds fastest PJ" I just need to know
what li-po/motor combo will do the trick.
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Old Jan 04, 2004, 06:41 PM
More Combat Please!
Wind_of_Change's Avatar
Utah
Joined Dec 2003
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Ed,

If you're using 10 cell Nimh HE cells, a pack probably weighs about 7.5 oz. If you get custom built Kokam 1500 3s1p's (www.edogfight.com for $44/ea) and make them parallel, you'll end up with the exact same weight. This site builds batteries with shorter wires, so it'll save you half an ounce over the normal Kokams, two of which will give you 8 oz. weight.

You can barely fit this 3s2p configuration in the plane, but it'll give you 24amps steady and 3000 mah. You may need to move your receiver to the front of the plane and push your batteries into the rear compartment to hit your CG though.

If you want a 3s1p configuration, the Kokam will work fine, but you'll get longer flights with a 3s1p Thunder Power. You can't fit two TP 3 cell packs in that plane, they're too long.

I had to do a lot of reinforcing of my motor housing and rear of the plane on my Projeti. Fiber tape, epoxied sig cloth, etc. I'm only using a 3s1p setup, because I have lights on my plane, which add a lot of weight, and mostly night fly with it. If you get 3s2p setup to work, I'd really like to hear about it!

Todd
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Old Jan 04, 2004, 07:13 PM
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Va.
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Thanks Todd, what motor are you using ? I think I saw a post
Re your illuminated PJ. Looks neat.
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Old Jan 05, 2004, 01:06 AM
More Combat Please!
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Ed,

I'm using a speed 480 7.2V currently. Gone brushless on two of my WWII planes, but not the Projeti yet. It's plenty fast for my tastes. Besides, I can't imagine my HS55's handling anything more. As is, they have a difficult time on high speed loops. Have you upgraded your servos to something more robust for the kind of speed you're trying to achieve?

Todd
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Old Jan 05, 2004, 07:29 AM
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Yes I'm using HS55s. Hummmmm maybe I'll just go with the Mega-4 & the 10 cells, I have plenty of the HE 1100s 7,8 & 10 cells. I
also have some long can 480s & a 480 7.2 v. The 480 7.2v has the built on esc & I think its only good for 8 cells.

I was supprised to hear the Li-po would be about same wt as the nimhs.
Was thinking several ozs of saved wt !! Maybe I'll wait for anouther plane to go li-po, maybe my simple 400. The PJ is
pretty fast with my current setup. The thing I have trouble with
on other hi-perf models is the landing. Landing the PJ is great
as it slows down fast.

Ed
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Old Jan 05, 2004, 01:08 PM
More Combat Please!
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Ed,

There will be a considerable weight improvement if you want to switch to lipos specifically for lighter weight. In that case you would just use a 3s1p or 2s2p solution, and get about the same amount of power as you're getting in a 10 cell.

But you requested a power boost, so I imagined you wanted to go with parallel Lipos so you could keep your weight about the same and have more power/life. Lipos will work well for you either way. They are lighter, and they pack a long life punch.

Todd
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Old Jan 05, 2004, 06:29 PM
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If can get same power with less wt, that should = more speed. Sounds like the 3s1p may be the way to go.
Thanks again........ Ed
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Old Jan 05, 2004, 06:42 PM
More Combat Please!
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Utah
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Ed,

NP. I just got a parallel lipo adapter, so next time I go up with my Projeti, I'll try a 2s2p configuration, see how that compares to the 3s1p. Let you know if it's better or worse.

Todd
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Old Jan 05, 2004, 08:33 PM
Life-abstract=conformity
S.F. Bay Area
Joined Aug 2002
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More power!

Zorro,
Quite an interesting project.
You started me thinking...how about a Mega 16/15/3 with a 4S1P LiPo pack? Use the higher voltage of the 4S pack (14.8V) to deliver the power instead of relying solely on the amperage.
A TP 2100, 2400 pack should deliver 30A safely.
Check it out and post some picts.
Jay.
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Old Jan 05, 2004, 09:34 PM
More Combat Please!
Wind_of_Change's Avatar
Utah
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Jay,

The primary concern with Zorro's Projeti is the battery space in the fuselage. The compartment barely fits three lipos side by side in a 3s1p pack. The Thunder Power batteries are too long to fit them 2 x 2 lengthwise, so getting a 4s1p with TP's in the Projeti would be really difficult and require changing the battery compartment.

If you didn't have to worry about a receiver, it might work. Getting a really small receiver and somehow embedding it under the batteries would be the first step. There is a little drop notch where the servo wires exit out the bottom of the plane to the wings. If you could fit the receiver down in that notch, remove the receiver firewall, and hollow out the nose an extra inch or so, you might could get a 2x2 configuration to fit.

I'd love to see that! Go for it Zorro, and if it works, others may follow suit, myself included.

AFTER I get my Unicorn combat wing up and running, that is.

Projeti's Beware!!!! The Unicorn Will Stomp!!!

Todd
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Old Jan 06, 2004, 11:12 AM
Life-abstract=conformity
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Packing a Lipo pack...

Wind...
I'll be getting a Projeti this week from HL and will be able to check this out.
Gotta admit though, a 4S Lipo pack is Exciting!
Skies.
Jay.
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Old Jan 06, 2004, 01:45 PM
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Va.
Joined Mar 2003
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Thanks for the info guys, for some reason I missed Jay's 1st post, but just caught up on all now. I been using the Berg 4, might be able to hide it down in that hole. I'm so busy now with business
stuff, I can't get to work on the PJ. Li-Po will be totally new to me, will need charger, pack & all.

Tnx
Ed
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Old Jan 06, 2004, 07:46 PM
More Combat Please!
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Utah
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I just got the new Hobbico MkII field charger (I think that's its name). It's awesome because it charges two lipos at a time. I can charge all six of my lipos in a couple of hours. Has separate plugs for each port so you can check your voltages mid-charge.

It can also charge Nimh's and Nicads. But I've stopped using those.

Todd
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