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Old Apr 15, 2015, 01:05 AM
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Upgrading old Zagi 400 to brushless/lipo

I have an old Zagi 400 that hasn't been flown in years, but I want to get it flying again. Figured a worthwhile upgrade would be a brushless motor and lipo batteries (all my Nicads are dead for sure). Here are some specs I found for the original speed 400 motor:

8 cell 9.6v battery pack, 5X5 prop, 14000 rpm @ 14 amps (not sure if this is static or in flight). The speed 400 is 28mm in diameter and 36mm long.

I'm thinking a 2s setup (7.4v) with a 2700-2800kv inrunner with the same 5x5 prop would be a comparable setup. A couple of motors I found:

Great Plane Ammo 28-35-2700 ($60)
HobbyKing S2838-2800 ($20 - might as well go with this one since it is cheaper)

I'll just pick up a 40A esc ($15). For a battery I think something in the 2200mAh range will work.

Would love to hear some input on the motor/battery selection before I start ordering stuff. Should I go with a higher/lower kv? Should I consider 3s rather than 2s? I'd like to keep the Zagi as stock as possible so I can make the easy swap; however, I have seen people adding the carbon spars which might be a good idea. Also, if I need to open up the back end for a bigger prop that isn't too big of a deal.

Thanks!
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Old Apr 15, 2015, 09:00 PM
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I'd say you are on the right track with a S400 equivalent and 2 cell pack. I run mine this way and on a 2200 2 cell pack I get about 8 minutes of flying time which is enough for me. It flies close to the stock Z400 this way.
I would caution against making a speedster out of this airframe by putting on a hot motor and 3 cell packs. You should definitely think about adding some carbon spars, I used .125 carbon tube which seems to work pretty well. Otherwise, you will get the Zagi flapping wing which gets worse and worse.
I went to a 6 inch prop on mine partially because I often fly it in a park and the noise level is reduced with it. My favourite prop is a Cox 6x4 prop but apc's and others work well too.
I'm considering rehabbing my Zagi for FPV by adding a Vtx and camera with panning. I will peel off the covering tape and cover the airframe with 5 mil laminating film. If kept reasonably light, it should make a pretty good platform.
I also have an old Zagi EPP slope wing which I have rehabbed and a Zagi THL which still flies great in light winds.
Here's a photo of the Z400, you can see how I added a couple of spars on the top.
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Old Apr 16, 2015, 12:50 AM
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Quote:
Originally Posted by B.Welwood View Post
I'd say you are on the right track with a S400 equivalent and 2 cell pack. I run mine this way and on a 2200 2 cell pack I get about 8 minutes of flying time which is enough for me. It flies close to the stock Z400 this way.
I would caution against making a speedster out of this airframe by putting on a hot motor and 3 cell packs. You should definitely think about adding some carbon spars, I used .125 carbon tube which seems to work pretty well. Otherwise, you will get the Zagi flapping wing which gets worse and worse.
I went to a 6 inch prop on mine partially because I often fly it in a park and the noise level is reduced with it. My favourite prop is a Cox 6x4 prop but apc's and others work well too.
I'm considering rehabbing my Zagi for FPV by adding a Vtx and camera with panning. I will peel off the covering tape and cover the airframe with 5 mil laminating film. If kept reasonably light, it should make a pretty good platform.
I also have an old Zagi EPP slope wing which I have rehabbed and a Zagi THL which still flies great in light winds.
Here's a photo of the Z400, you can see how I added a couple of spars on the top.
Thanks for the reply. I think I'll go ahead and pull the trigger on that 2800kv I mentioned, along with a 30A esc and some 2200mAh lipos. You mentioned in a previous thread that you get about 25 minutes of flying time at 60-70% throttle...is the 8 minutes more normal? 8 minutes on a 2200mAh battery is an average of 16.5A which seems about right if you are zipping around pretty good rather than a more leisurely flight.

I'm with you on not making a speedster out of this Zagi; I was happy with the stock performance so that is all that I am after. That being said, I've never experienced the Zagi flap, but I guess it wouldn't hurt to add some spars. Would you recommend putting spars along the leading edge as well? Or do you think just one across the middle is adequate. The newest Zagi HP (similar size) has spars along the leading edge (top and bottom) as well as a single spar across the middle. I the middle spar is more necessary because of the large cutout for the electronics bay the Zagi HP has...however, the Zagi 400 is solid at the middle (well, besides the recess for the receiver).

Thanks for the input! Those Zagi FPV setups are pretty sweet!
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Old Apr 16, 2015, 01:50 PM
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Sorry, meant to say 18 minutes of flight time, and that was with some tired battery packs.
Can't say whether adding spars to the leading edges would be better than mid chord, but adding them where I did seemed to do the job for me. I would recommend that you add spar reinforcement in any event.
One thing to keep in mind if you decide to remove the covering tape... Be very careful in doing so as the tape can easily pull up foam core chunks resulting in a real mess. Don't even try to remove the fiber tape as it will most certainly ruin the wing.
Good luck with your conversion, I am sure you will be pleased with the result.
Bob.
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Old Apr 16, 2015, 02:42 PM
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Originally Posted by B.Welwood View Post
Sorry, meant to say 18 minutes of flight time, and that was with some tired battery packs.
Can't say whether adding spars to the leading edges would be better than mid chord, but adding them where I did seemed to do the job for me. I would recommend that you add spar reinforcement in any event.
One thing to keep in mind if you decide to remove the covering tape... Be very careful in doing so as the tape can easily pull up foam core chunks resulting in a real mess. Don't even try to remove the fiber tape as it will most certainly ruin the wing.
Good luck with your conversion, I am sure you will be pleased with the result.
Bob.
I think I'll just mid chord like you did...one top and two on the bottom. I have to pull the electronics bay anyways to replace it with a new one (old one was cracked and I bought a replacement but never installed it). I wasn't even going to mess with the tape...just cut a groove and glue the spar in before taping back over it. I even still I have my leftover roll of tape...wonder if it is still good

I will be very happy with any flight time over 15 minutes. If I remember right, I was lucky to get 10-12 minutes with the old nicads and S400.
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Old Apr 21, 2015, 02:04 PM
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Did you pull the trigger on the upgrade? I just got my 400x out of storage and charged batteries and found one took a charge and the other two were dead. I wanted to upgrade to a brushless and lipos to a factory spec. Not looking for a speed demon just back to factory specs with a little extended flight time. Curious is you got it completed.
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Old Apr 21, 2015, 02:08 PM
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Originally Posted by csims723 View Post
Did you pull the trigger on the upgrade? I just got my 400x out of storage and charged batteries and found one took a charge and the other two were dead. I wanted to upgrade to a brushless and lipos to a factory spec. Not looking for a speed demon just back to factory specs with a little extended flight time. Curious is you got it completed.
Everything is on order! Should be here tomorrow and flying in a couple days! I'll let you know how it goes. I am kind of antsy to fly so I'll probably get a few flights in before I put in the carbon spars. Total upgrade for a motor, esc, two batteries, spars, props/prop adapter, and some connectors was about $75.
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Old Apr 25, 2015, 05:51 PM
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Consider covering your Zagi with New Stuff (available from Aloft Hobbies and Canuck Engineering). This will add strength and stiffness to your wing with little weight gain. It's also inexpensive. You can read a lot about new stuff in the slope soaring forum or in the threads about the Assassin, Grim Reaper et. al. Here's a good video on covering with laminate: http://www.rcgroups.com/forums/showt...e#post31233599. I just did my first covering job with New Stuff and I have to agree with what others say about it.

Take a look at how other designs use carbon spars in their wings. A flat strip of carbon oriented with the wide dimension vertically works well and all you need is to cut a slit of proper depth with your new (very sharp) xacto blade and some glue to get it done. I have built 7 flying wings.
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Old Apr 25, 2015, 11:33 PM
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Keep me posted

Quote:
Originally Posted by jstluise View Post
Everything is on order! Should be here tomorrow and flying in a couple days! I'll let you know how it goes. I am kind of antsy to fly so I'll probably get a few flights in before I put in the carbon spars. Total upgrade for a motor, esc, two batteries, spars, props/prop adapter, and some connectors was about $75.

Keep me posted. I also want to upgrade my 400X. Im not looking for a speed demon I want it to keep the same speed as the original but want it to preform just as good with less weight. I cant located any nicad battery packs for mine so Im looking to do the upgrade you did.
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Old Apr 26, 2015, 11:35 PM
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Originally Posted by Lost_Dawg View Post
Consider covering your Zagi with New Stuff (available from Aloft Hobbies and Canuck Engineering). This will add strength and stiffness to your wing with little weight gain. It's also inexpensive. You can read a lot about new stuff in the slope soaring forum or in the threads about the Assassin, Grim Reaper et. al. Here's a good video on covering with laminate: http://www.rcgroups.com/forums/showt...e#post31233599. I just did my first covering job with New Stuff and I have to agree with what others say about it.

Take a look at how other designs use carbon spars in their wings. A flat strip of carbon oriented with the wide dimension vertically works well and all you need is to cut a slit of proper depth with your new (very sharp) xacto blade and some glue to get it done. I have built 7 flying wings.
Very cool! Thanks for the info on the New Stuff. Looks pretty slick. How does it compare to Monokote? Similar but doesn't shrink? I remember years ago I had an electric foam fighter plane that I covered using monokote. I do remember it being kind of a pain because of the way it shrinks but it looks like the New Stuff doesn't have that issue. I almost have my friend talked into starting off with a flying wing (then we can have dogfights!), so I'll definitely let him know about New Stuff if he decides to get one.

I saw that flat strip of carbon when I was looking around. They also have those on the newer Zagis, along with the carbon tube spars. A single flat spar on the bottom of my Zagi would definitely stiffen it up and it would be less invasive since I wouldn't have to remove the electronics tray. I'll look into it.

Quote:
Originally Posted by csims723
Keep me posted. I also want to upgrade my 400X. Im not looking for a speed demon I want it to keep the same speed as the original but want it to preform just as good with less weight. I cant located any nicad battery packs for mine so Im looking to do the upgrade you did.
I got all my parts but got preoccupied this weekend with some other projects. I hope to have the first flight tomorrow after I make the swap. I couldn't track down the canopy kit I ordered years ago, so I think I'll just fly it as it. I see you can still buy a replacement canopy kit for the 400, so I might do that and then install some carbon spars later. Or just do the flat spar like I mentioned above.

I don't think there will be any weight savings from going with the brushless/lipo setup. I'll have to weigh everything and compare. I know the 30A ESC that I bought will be a tad heavier than the current ESC just based on how big it is. Everything else I imagine will be about the same.

I'll post an update hopefully tomorrow!
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Old Apr 27, 2015, 07:36 PM
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New Stuff doesn't shrink much so you need to get it on nicely in the first place. It's better to use an iron that is just hot enough to stick it and then go over it all a second time with just a little bit more heat after you've got the part all done. I found the video I linked to be pretty much spot on.
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Old Apr 28, 2015, 01:22 AM
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The Zagi is back! I got all my new components installed and got one flight in today. Felt like the Zagi I remember, except with a noticeable increase in torque which gave me better climbing performance. The flight was going great and it was hard to keep off the throttle. I was about 16 minutes in (mostly 75%+ throttle) when I noticed a decrease in power...and it came at the worst time. On a turn back up field, into a good breeze, I stalled it out when I tried grabbing more throttle and didn't get much in return. My recovery efforts failed and I ended up about 25' up in a tree! Fortunately I had an extension ladder (and long pole) on hand because I was flying at my work. What a way to welcome the Zagi back. Funny story, the first time I ever flew the Zagi (had to be almost 15 years ago) I crashed it into a power pole! This Zagi is tough!

Anyways, about the upgrades. Everything swapped pretty easily...no major issues that I can think of. Here are a couple pics of the old and new setup:




Overall, the new components added some mass, but not much. Here is a breakdown of the old and new components:

Component, New Mass, Old Mass, Difference

Motor, 100 g, 73 g, +27 g
ESC, 32 g, 16 g, +16 g
Batt, 131 g, 152 g, -21 g
Total, 263 g, 241 g, +22 g

I also forgot to measure the new prop adapter, so that added a few grams as well. So, not too bad. The heavier motor and lighter battery did shift my CG back a bit, so I do need to add some counterbalance even with the battery pushed as far forward as possible. It flew okay, but could tell it was a tad tail heavy...should get better performance once I shift it forward back to normal.

After the flight I did notice the higher torque actually turned the motor underneath the zip tie mount. I think I'll add some double-sided tape to hold the motor in addition to the zip tie. Right now I'm using an APC 5x5 prop. I tried putting on the original white Gunther prop (after I opened the hole up a bit) but I ended up cracking it when I snugged down the prop adapter...pretty brittle after all these years.

I plan on shortening up the battery leads a bit (probably half) to make things a little bit neater inside the tray...right now they are just a bit too long to get everything to fold nicely. Also, the exit of the battery leads out the side of the battery makes it a little tight in the battery tray but I can still get the canopy on, so no big deal.

I forgot about the balsa spacer in front of the old S400 motor, so really you could get away with a longer motor (50+), but that would add some unneeded weight. Here is my parts list that I ordered from Hobby King:

S2838-2800 Brushless Inrunner (2800kv) PRODUCT ID: S2838-2800
Hobby King 30A ESC 3A UBEC PRODUCT ID: F-30A
Turnigy 2200mAh 2S 25C Lipo Pack PRODUCT ID: T2200.2S.25
Short Prop adapter w/ Alu Cone 3mm shaft (Grub Screw Type) PRODUCT ID: PA-3MM-5MM-D ***
APC Style Propeller 5x5 PRODUCT ID: 074000060

***I goofed and ordered the wrong adapter. The motor is actually .125" (3.18mm), so you'll need to make sure you order the correct one unless you have a way to enlarge the hole like I did.

I also ordered the carbon spars and some XT60 connectors.

Overall I am happy with the upgrades. I'll most likely just fly it as is and make some other upgrades in the future like the carbon spars. I've been looking at getting a 2.4GHz Tx (still running 72MHz), so if/when I do I'll probably make the other changes while I am at it.

Thanks everyone for the help!
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