Glacier Girl

My Feedback: (4)

Ok I couldn't resist. I have the 52" version by NitroModels, and when I saw they were offering a 90" I just had to have one.
And I'll be the first to admit this size bird is a first for me. So any and all suggestions as to motors, packs, servos, etc will be gladly accepted.

Ok I also admit to not realizing how big a 90" twin would be. First indications should have hit me when the Post Office showed it as a 30 pound shipping weight.

Well big can be beautiful, I see it as a lot easier to fit my fingers into something this big. LOL

So, once I and the wifey got over the shock of how big it actually is(this one did impress her, she didn't call it a toy), I started digging up some info on birds this big.
Now then, closest to it is something like the VQModel's version, granted it's got a lot going for it, but this one is oh around $350.00 less. So for a little less realizim, and a big chunk of change in my pocket, I'm ok with that.

As for power I have a pair of 3250-7 Tower Pro motors. And according to the genius' over on RCU these will power it well. Again a savings as the Axi 4130-16's are around $120.00 more a piece. So another $240.00 not spent.
I plan on using 5 or 6S packs on each motor, roughly 50 amps and somewhere around 650+/- watts per motor max.

Most likely I'll stick with CC 60's for esc's. Unless someone comes up with a better proven choice.

As for servos, 8 are needed for the control surfaces, ailerons, elevator, rudders, and flaps.
My bud Terry pointed these out to me.
http://www.rc-monster.com/proddetail...MS660mg&cat=39
He swears by them, but again if someone has another offering I'll be glad to listen.

Landing gear. Well it comes with standard gear and a steerable nose unit but no retracts.
To me the nose gear in the stock position is to far forward and I want retracts.
So Spring Air makes a set of retracts with the proper forward rake on the nose gear, and offers 7/16" struts.
Again If someone knows something better speak up before I order them.

As for packs, well that's a big unknown right now. So all suggestions will be listened to.

Almost lastly got to have counter rotating props, somewhere in the 15" range and oh 8 to 10 pitch, and of course have to be 3 blades. MAS as a smattering of such offerings so they look good to me, as I used their 9x7's on my smaller version and I have no complaints with em.

So there I am. I added a couple of shots showing the 90 with the 52 for compairison.

Glacier Girl

My Feedback: (4)

Well to continue, I got everything on the scale tonight to get an empty weight starting point.
3020 gr or approx 6.66 pounds. That's the booms, wings, center pod, elevator,rudders, cowlings, intakes, superchargers, wing tubes, canopy, and the pack of control rods/clevis's etc.

Oh and if you don't like the green version they do offer a silver one too. Sorry no red Yippee one.

I looked over the girl tonight, trying to see what if anything can be done to lighten her up, and honestly I really don't see a lot. I can cut out the landing gear blocks and that's about it.
Formers are not that thick or over size so no go there, and the sheeting is basicly only where it needs to be for strength. Covering is a green version that's been given a coat of flat green paint. Oh and before I forget mine is going to be a semi copy of my name sake. Yeah I know the real one is an H model but hey it's what I have to work with.
I have to admit to being impressed with what I see so far. Who ever put this one together did a nice job. No missed glue spots that I could see, and no excess glue either. All looks straight and square, and the covering job is super. No wrinkles, bubbles, etc. And all the edges are down tight.
So that's where I'm at right now. Tomorrow I'll get a start on some of the basic items, like gluing in the hinges, and fitting the wing tubes, and such.
Oh and one last thing. If you have not built a bird before, this is not for you. The included instructions, are the worst "Engrish" translations I've seen, and a lot is left out of them.
So don't try this unless you want a lot of left over parts and a bird that will not last.

Oh something else I wish to ask. Give me ideas on making this a teardown version for hauling it around. I'm looking at probably removing the center pod and wing, and installing a brace across the booms to keep everything from twisting up the elevator.
So I'll probably look at a dual Rx set up to keep setting it up a little easier. Oh and plan on using the Hitec 6 channel dual range versions for that.

7th Rider

Since you almost have everything let me give you an economic battery option, you can use Himodel.com 6S or 5S 15C 4100mah Lipos.

How its going? Can you post some detail pics like; joints, landingear, etc.?

It will be easy to access batteries, or will need to open a hatch or something?



Greetings!

Glacier Girl

My Feedback: (4)

7th,
Have a link to the packs?

I spent most of the day online, rounding up stuff for her.
What you see is what I have so far. Other then the motors. Here's a pic of them next to a 480 motor for comparison.
The air retracts and struts are Spring Air units. Here http://www.vqwarbirds.com/products/access/sa100.html $205.00
And here. http://www.vqwarbirds.com/products/a...716sstrut.html $65.00

Wheels and brakes are probably going to be Robarts, waiting on reply for pricing, somewhere around $200.00 for the brakes.

Monster was out of the BMS660MG servos, but I tracked some down at Nitrohouse. $40.00 each
180 oz of pull at 4.8 volts. http://www.rc-monster.com/proddetail...MS660mg&cat=39

Spinners 2 1/2" 3 blades are Dubro #550 Somewhere around $9.00 each.

CC 60s were around $120.00 each
Hitec Rx's about $55.00 each.

I'm going to stop at the LHS and pick up some 3 blades to get real world specs on setups.
I have 9 3/4" from the center pod to the centerline on the boom, so I can swing up to an 18 or 19 inch blade.

Glacier Girl

My Feedback: (4)

Room is not going to be a problem from what I see.
There is a 5 1/2" long by 5" high and wide area from the firewall to the front of the cowling, on each boom.
There's another 3 1/2" long of additional area from the firewall to the wing.
There is 14 1/2" of area, 5" wide and running from 3 1/2" to 2 1/2" under the wing.
The center pod is 13 1/2" long from the wing LE. 5 1/2" wide and tall.

So since I'll need to remove the wing for transport, battery access will be easy.

Here's some pics. I used a 6" ruler for scale. #1 is the boom, #2 is the center pod.
#3 shows six 2S2200 20 C packs, so a 6S2P4400 20C for argument sake, snug as a bug, and will clear the wing no problem. That leaves 5 1/2" of open space in front of them and around 9" behind.

Glacier Girl

My Feedback: (4)

Ok for anyone who's keeping score.
Prices so far.
Bird - $250.00
Retracts/struts - $285.00, less then what I have in the 52" version. [:@]
Servos - $370.00
Spinners - $16.00
Esc's - $235.00
Rx/crystals - $135.00
Motors - $100.00
Rolls of battery wire - $65.00
That's oh somewhere around $1400.00 so far.

Still have to add wheels and possibly brakes. Somewhere around $350.00
Props, what maybe $40.00
Misc hardware/wires/wood/etc. - $150.00
Packs???? I'm guessing in the $600.00 range per side.
So I'm up to around $3200.00 ready to go. [X(][X(][X(]
Want to continue??????

7th Rider

This is the link to the 4100mah 5S (15C) packs:

They are like 15% heavier than prolites but, same discharge and +capacity, cost half

http://www.himodel.com/en/rc_hobby/electric_1292.php

I think the bird can go with one of this for each motor, this way you save $380 [8D] !!!


By the way they supposed to fit perfect with this new balancer ESC , cost half too :

http://www.himodel.com/en/rc_hobby/electric_1875.php



Do u have the link where u bought the motor?

So the batteries will be placed on the Fuse, are u planning one fly per day ??



Have a nice weekend!

Glacier Girl

My Feedback: (4)

7th,
Thanks for the lead on the packs.

Motors came from here. http://www.aarchobby.com/shop/index....roducts_id=716

I have quite a fleet of birds, I usually take at least 4 at a time. So, I can charge packs between flights. Or I guess I could always buy extra packs.

7th Rider

Hey!

The model really seems light, I was expecting +4000 grams empty weight...

I dont have to much experience with big retracts, why you choosed air instead mech?
I was thinking in Hyperion or axi motor mounts, which are the measures between screws for frontal mount ?

Glacier Girl

My Feedback: (4)

7th,
Air vs mechanical? 2 big reasons. Less weight and hassle , only need one servo to operate the whole system. And they are air up and spring down, if there was a leak in the system gear automaticly comes down. With mechanicals you would need 3 servos and the wiring to run them, have to set up travel on the servos to get them to work correctly, and if something fails there, you may only get a partial gear down or none at all.

As for the mount, I ended up converting the gas versions to work. Still have to add some cooling holes. But using an aluminum face plate has an added bonus. it acts as a heat sink.

As for the spacing, I'm not sure, what I did was pop off one of the ends of the motor and use it's holes as a template to mark the plates for drilling.

Glacier Girl

My Feedback: (4)

Oh something else on the mounts. I made them each to have down and right thrust, as it looks like I'll end up with both props spinning the same direction. Bummer really wanted C/R versions.
But if I do find C/R props I can easily change the motor angles back.

I have 13 sets of props on the way, only 2 of the sets offer C/R versions.
I'll see which ones work out the best and go from there.

thunder21

My Feedback: (2)

Have you run any tests on the motor yet? I'd be interested to see how the mounting system you're using is going to work. You've just threaded a pair of screws into the front of the glow mounts?

I looked up the specs on the motors you have. They have a really high Kv, 670. They are very close to the AXI 4120/14 motor, not the 4130/16. The 4120/14 is really intended for up to 5s lipo configuration. If you go higher than that you're going to have to use a small (like 12" ) prop. And the RPMs will be way up there so watch out for thrown magnets.

Glacier Girl

My Feedback: (4)

thunder21,
Hey, like I said in the beginning this is my first big one. Any tips you can come up with I'll gladly listen to. Have another suggestion for mounts?
The CC 60's should be here this week so I'll run up the motors and see what happens.
If it looks like they are not going to work out, I do have the bigger 3520-7's on hand.

Glacier Girl

My Feedback: (4)

Ok thunder21 had me doubting myself, so last night I cobbled together what I had handy to do a run up on one of the motors. I used a China esc with a 3s pack to power the rx, and a CC35 with the bec disconnected to run the motor. Used three 2S2500 20C packs wired in series for a 6S 2500 configuration. Used an Astro meter in line. Biggest prop I had on hand was an APC 11x9 4 blade. And just to see how the mount would hold up I engaged the brake function on the esc. First run up was a quick one to see how far the CC esc would go on a burst. Well right around 40 and it kicked off. So I started a slow run up, got it to 38 amps draw, and held it there. Motor was as quite as a church mouse, prop was throwing some serious thrust. Slammed the stick to off, and felt the brakes apply as the boom twisted back to the rest position from where it had torqued to.
I ran it up 3 more times and held it at 38 amps, showed 585 watts. I tried hammering the throttle and using the brake to see if the mount moved. I can't say that I saw any flexing or twisting in it. And the motor after the 5 run ups was barely even warm.
Don't really know if this proved anything but in my thinking a bigger 3 blade shouldn't pull a lot more then the 4 BLADE.

7th Rider

GG,

Smart layout on the motor mounting, thanks for the explain on the retracts!


585 watts, making a gross calculation, thats mean a lil bit more than 500 effective watts on the prop, about 1000 watts with the whole power train. Following the thumb rule: with this configuration you can fly a 10 pounds model in a strong aerobatics fashion. This one should weight about 12 - 14 pounds, right ?? If this is the case it should have a nice aerobatic performance for a scale flight.

Did you ordered the batteries already, what was your choice?

I was thinking in a sound device to make some real sound on this project, any one have experience with this kind of devices?

Glacier Girl

My Feedback: (4)

No serious decision on packs yet, though my LHS is closing up it's doors, and I've been invited to a 50% off sale on Thur. So I'll look to see if they have anything I can use to make up packs.

As for sounds, check out this forum.
http://www.wattflyer.com/forums/showthread.php?t=573
The guru's there have it down to a science, tied to throttle position and all. Way over my head but if I remember right, you can have one of them build a set up for you.

I spent all of last night building a template for the plank that will hold the nose gear and steering. 4 1/2 hrs of cutting, gluing, measuring. But I now have a template that will slide in and connect to the 3 main formers and the front firewall of the center section. I'll pick up some 1/4" liteply today, to cut out the real one, then figure out the retract and steering install.
Will be another first for me, instead of a tiller arm it uses a dual setup, will have to use flexible metal wire to connect it up vs a rod. Wire has to be able to bend as the retract comes up.

thunder21

My Feedback: (2)

GG, I'm a little confused at your numbers. First off, was the prop an 11x6 four blader? 11x9 seems like a lot of pitch for a four blade prop. I know that APC made an 11x6x4 prop. Maybe that's what you used?

Second, if your setup was drawing 38 amps and 585 watts, then volts must have been 15.4. If you're pulling a 6s lipo down to 15.4 volts, you're going to kill them quick. The lowest you should be pulling them down is 18 volts 3volts/cell ESC cutoff)

If you use a 15" 3 blade prop your amps are going to be WAY up from what you're getting now. A 4 blade 11 inch prop is like a 11.75" three blade prop.

Glacier Girl

My Feedback: (4)

Thunder,
Just went out and rechecked 11x9 and 279x229 are cast into the blades, and APC-3 is pressed into the hub. And it is a 4 blade.

Glacier Girl

My Feedback: (4)

Thunder, you have me on the specs, I didn't look at voltage, and 38 amps was all the CC35 would handle with out kicking out.

Ok Look at these 2 versions and give me your opinion.
TP 3520-7 720kv, 5.5 Amp no load, .027 Ohms
TP 3520-7 590kv, 2.19 Amp no load, .035 Ohms

Any better?

thunder21

My Feedback: (2)

I'd be surprised if the ESC was shutting off due to overcurrent at only 38 amps. The few CC Phx 35s I've tested will take over 50 amps before shutting down due to overcurrent. An 11x9 four bladed prop would draw a lot of amps on a 670Kv motor at 6s voltage. Probably over 70 at full bore. It would also have a pitch speed of like 90 MPH. The thing to remember is that the ESC doesn't regulate current. It only regulates the time the battery is connected to the motor. So if you have propped for a max current of 70 amps, the battery is having to put out little 70 amp spikes. If it can't do that, the voltage will drop and you'll get the exact symptom you describe. Most current meters don't measure instantaneous peak current, only average current.

If you want to use a 6s setup, you'll want to use the lowest Kv motor so you can swing as large a prop as possible.

7th Rider

GG

How its going, any progress on the conversion? Just in case you are not set with the batteries yet, another battery option for you :

http://www.aero-nuts.com/product_inf...roducts_id=312

I am still imaging the hard that will be the transportation of this guy, if you remove the wing, the 2 fuses are only holded together with the elevator stab, it could easily break...

Glacier Girl

My Feedback: (4)

Thunder, and 7th
After a little further diagonsis, found the packs I was using were not fully charged, esc was cutting out at low voltage. My bad.
Anyhow just to be safe I installed the 3520-7 motors, so should be good there.
And as for packs I settled on 8 3S3700 20C Lipos. Four per boom. wired in series and parallel on both sides, and with a cross connection between the packs. I used parallel and serial connectors from Hobby Lobby,# FMAC03P/ FMAC03s to make the connections with very little extra wire needed. Packs just plug into the series connector, which in turn is soldered to the parallel connector. The parallel connectors have 2 output tabs, so one will run to the esc, and the other will tie to the other side's packs.

EDIT: 7th, yea, I thought about that too. I figure on using a simple cross brace installed between the booms, when the wing is not installed, just bolt it to the wing retainer nuts, and it will lock the front half of the booms together too. So no extra stress on the elevator, during transportation.

7th Rider

I am happy to hear that was just uncharged batteries...

Wow, 8 X 3S 3700, you will have long flight times and good power! A lil bit heavy for my taste but this one of the lowest wing loading P-38 out there, it should be ok.
Are they Polyquest 3S 3700mah 16C ?


How many screws we will have to remove to dismantle for transportation?

I am guessing :

The center fuse: 4 screws in the canopy and then 2 bolts attaches the wing.
In each side fuse: 4 screws holds the motor "super charge area" and then 2 bolts in the wing.


That will be 12 screws, 6 bolts I am correct? [X(]


Any new photos??
Good luck!!

Glacier Girl

My Feedback: (4)

No they are the Hyperion 20c versions

Mounting bolts/screws.... Should be 8 screws for the s/c covers and 4 bolts for the wing.
I plan on leaving the gondola attached to the main wing. I went with 2 rx's so all I'll have to disconnect are the 3 servo leads, one air line, and one battery connection on each boom to disconnect main wing/gondola.

Wing loading will work out to less then 28 oz per sq foot, from what I've caculated, so she should be a floater.

One thing I did do in reference to disassembly, I will install a R/E magnet under each s/c cover. Those tiny screws tend to walk off. With the magnet they stay at home when I pull them out. It's what I did on the 52" one, on the canopy to keep track of the screws, and it works well.

I'll try and gather up some shots soon, it's been high 90's and 70+% humidity here. Was just to hot to get much done. I finally broke down and installed A/C in my shop, finished it up last night so should be nice and cool in there tonight.

mpope1

Hey Glacier girl, just received the 90" p-38. Was interested on how you plan on mounting the retracts. Looks kind of tight in the booms. This is one sweet plane.....