PDA

View Full Version : Anyone think about the GP Super Stearman?


Bigfoot21075
11-16-2005, 03:46 PM
Anyone think about converting the Great Planes Super Stearman bipe to Electric? This plane gets great write ups in glo form. It is a nice looking ARF

http://www.greatplanes.com/airplanes/gpma1350.html

71" Wingspan, weights 14-15 lbs. Would be expensive, but it looks awesome and is supposed to be a great flyer. I would think cooling is an issue with epower and that design.

rcers
11-16-2005, 04:14 PM
I think it would be fantastic. Get some deep pockets it will cost a bit to do right....

Mike

Twmaster
11-16-2005, 08:44 PM
That is a very sexy bird. I'd bet an Eflight 60 brushless outrunner would fly it. :D

On second thought no. However a big brushless inrunner on a Tom Hunt Modelairtech belt drive would!

jonnyjetprop
11-17-2005, 01:57 AM
A second crazy thought would be to use nimh batteries arranged in a circle around the motor so the weight could be concintrated in the nose.

John

ENUT
11-18-2005, 12:27 AM
I just read the gp page on this plane.Boy I think its pretty foolish:p First look at the web picture.Blow up the pic and you see its a 18/6/10 prop! Then I go to the page of items needed,There telling you a 13/8 prop or 14/8!! Next read the reveiw,they use a gas engine not no .91 4stroke and a 16/8 prop.The best killer is the e-power set up at the bottom of the tech page,There best set up will only yeild 638.4 watts:eek: which then you divid by 14lbs(if it comes out lite:rolleyes: ) you get 45.6 watts per pound.I wonder which einstein figured that one out:p :p :p :p Anyhow now for the REAL POWER I'd look at the AXI 4130/20 or maybe the smallest 53 series motor.Hey guys where talking about a bi plane with lots of drag.Also Twmaster exellent idea on the cowl batteries.A few years back a guy in N.Y. built John Tanzers Sopwith baby Bi plane and did just that to get a perfect balance.Have fun ...........ENUT

laxlife
11-18-2005, 05:24 AM
I picked up a great used GP Super Stearman and I'm going to convert it to electric. I've got a choice of Axi 4130 or 5330's or a Hacker geared C50-14XL. I've heard I'll need lots of weight in the nose to keep the CG correct so I don't know about long lipos like dual 6000 mAh 5s3p's. Wish me luck, I'm going in...

Bigfoot21075
11-18-2005, 10:40 AM
I picked up a great used GP Super Stearman and I'm going to convert it to electric. I've got a choice of Axi 4130 or 5330's or a Hacker geared C50-14XL. I've heard I'll need lots of weight in the nose to keep the CG correct so I don't know about long lipos like dual 6000 mAh 5s3p's. Wish me luck, I'm going in...

BEST of luck - Please keep us posted, I think you are onto an awesome project!

tahustvedt
11-18-2005, 04:47 PM
I wanted one of these earlier this year. I thought about powering it with an Axi 4130/20 on 8S with a 17x8 or 18x8 APCE propeller.

The reason I didn't get one was because of the huge one-piece wings and no hatch on top of the fuselage (as far as I could tell). Nice bird, I sorta regret not getting one. :)

Matt Kirsch
11-18-2005, 06:25 PM
I'm of the opinion that you're wasting your time if you shoot for less than 100 Watts per pound on nearly any glow conversion.

GP shows 14-15lbs for weight. 1500 Watts would be my target, which is a good bit more than a 4130/20 can take. That's 5320/28 territory. Besides, it probably needs the nose weight.

tahustvedt
11-18-2005, 07:15 PM
I agree, but I think the specified weight seems very high. I also think it depends on the application...

Calculating the approximate kit weight from this review:
http://greatplanes.com/reviews/gpma1350-rcm.html
AUW of plane in the review: 6861 g :eek:

Zenoa G-26 engine: 1484 g + muffler
24 oz fueltank: 672 g
5x Hitec 605BB Servos: 250 g
Standard receiver: ~45 g
Doesn't say what kind so I weighed my own stock futaba 1500 mAh Rx batt: 300 g
Mounting and control-hardware: 150 g
Total equipment weight: 2901 g

Kit weight=AUW minus equipment: 3960 g

Am I being too optimistic? How much does one of these mufflers weigh? Also, the prop and spinner weigh quite a bit and might add a little more to the hardware-weight I used.


I have a World Models Velox Rev II with an Axi 4130/20 and 8S PQ XP 2500 mAh battery. The empty kit weight was 2080 g. The AUW is 3590 g. That's 1510 g for a complete power and control system including mounting hardware, spinner+prop and all control hardware.


So: 3960+1510=5470 g (12.1 lbs) give or take.

It might be possible to balance by mounting the batteries all the way in the front of the cowling through a hatch on top and be intelligent about the servo installation to avoid putting weight in the rear. I'm confident it would fly well, but I don't have a big enough car for it. :o I already have a 4130/20 lying around so that's why I would try that. If I had to buy a new motor I would get the next step up.

Electrick
11-19-2005, 07:50 PM
I'm in the process of doing the GP PT-17 as an electric.

The dry weight of the airframe is around 11.25 lb. stock. That's calculated weight, not measured. I haven't got around to weighing it yet. I am deciding how and where to remove some weight from the fuselage, as I have stripped it to recover it in the proper color (yellow). I'm also investigating the feasibility of adapting a set of Robart oleo struts with balsa fairings to it, as the stock landing gear weigh a ton with the fiberglass fairings. Some weight could also probably be removed from the empennage structures, but I may just leave them alone. The cabanes and interplane struts may also get remade in balsa/ply, as they are very heavily constructed in fiberglass.

I have two power systems I plan to test. First is a 5.2:1 geared Feigao 5408412XL brushless motor. Motocalc says this motor will turn a 17-10 APC at a static pitch speed of 63 mph, pulling about 39 amps on a 8S2P LiPo pack.

The second is an AXI 4130/20. Motocalc says it will have slightly lesser performance at a current draw in the mid-30's on the same batteries and a 18-10 prop, but still should be acceptable for the aircraft type.

All the performance figures (79w/lb and 70w/lb for the Feigao and AXI respectively) I'm seeing in Motocalc are predicated on the use of 12.0 lb. as an empty airframe weight, so are expected to be a bit better in real life.

Once I get my Hacker 77 controller in hand, I will be posting some test results with each motor and various props. I was going to go with a CC HV85, but it seems they are still having some issues with them and you can't find one anyway, so I went to the 'other side'.

Rick

chute42
11-19-2005, 08:06 PM
Electrick, take a look at the Axi 4130/16 with 8s and a 14x10 prop I am getting 1300watts at 49amps so I am not realy pushing the battery or the motor. I am thinking about the Seawind for my next project. My concern is how to route the wires from the ESC and battery. Having owned the BD-5 that Hobby Lobby sold 3 years ago I can say that long runs on the battery or the ESC can open a whole new can of worms.
Chuck

Electrick
11-19-2005, 08:16 PM
I'm of the opinion that you're wasting your time if you shoot for less than 100 Watts per pound on nearly any glow conversion.

GP shows 14-15lbs for weight. 1500 Watts would be my target, which is a good bit more than a 4130/20 can take. That's 5320/28 territory. Besides, it probably needs the nose weight.

That depends on whether you want to do airshow-style aerobatics at 250 scale mph, or more scalelike flight with a few loops and rolls tossed in at 110 scale mph. Can you imagine a Cub with 100-120 w/lb on tap? :eek:

I'm shooting for no more than 80w/lb on my PT-17 conversion, and by all accounts it'll be plenty. After all, PT-17's were never known for their aerobatic ability. ;)

The Super Stearman is probably better suited to more power, since there is more than just a bit of difference between a 220 hp Continental and a 450 hp Pratt & Whitney engine. :D

Rick

Electrick
11-19-2005, 08:39 PM
Here's some real-world numbers from a fellow who converted a BUSA Nieuport 17 using an AXI 4130/20. Sounds promising, if the AUW can be managed.

http://www.rcgroups.com/forums/showthread.php?t=396446&highlight=+nieuport+17++

Rick

tahustvedt
11-19-2005, 10:38 PM
The second is an AXI 4130/20. Motocalc says it will have slightly lesser performance at a current draw in the mid-30's on the same batteries and a 18-10 prop, but still should be acceptable for the aircraft type.

I have real-world data of that motor/prop combo. Motocalc is way off with the stock numbers.

My setup:
AXI 4130/20
PolyQuest 8S 4000 mAh
Hacker Master 77 Opto

APCE 18x10
6390 rpm
~1440 W
26.6 V
54 A

APCE 17x8
6960 rpm
~1066 W
26.8 V
39.79 A


If you want the 4130/20 to behave closer to reality in Motocalc use these numbers that I have come up with by comparing with actual tests:

Motor constant: 285 rpm/V
No-load current: 1,6 A
Resistance: 0,045 Ω


This works well in most combos. The option "Account for heating in motor performance calculations" is enabled. For APCE props with that motor I use the following numbers based on thrust and rpm measurement:

18x8:
P const: 1,11
T const: 0,895

17x8:
P const: 1,11
T const: 0,887


I have rewound a 4130/20 to 26 turns and will test it with a 20x10 tomorrow or monday. If my calculations are right it will be successful, and maybe a suitable motor for 18x10 on 10S. I believe 18" is the scale size for the GP Stearman.

Electrick
11-19-2005, 10:48 PM
Thanks, those numbers look like they'd work better than what I was seeing. Your setup is the same as mine. The 17-8 prop looks like what I need. :cool:

Fortunately, I'm not looking for 3D performance (nor should I be), so I have a lot more leeway and options. 1066 watts into a 15 lb. AUW airframe should put me right around 70w/lb. Good enough for a plane designed in the 1930's. :D

Rick

tahustvedt
11-19-2005, 10:53 PM
I have a Seagull Edge 540 that I used to fly with that setup and that's where I got those measurements. The plane weighted a tad over 4 kg (8.8 lbs). The 17x8 was the best prop for that plane and motor. It had close to unlimited vertical.

mmmdowning
11-20-2005, 01:40 AM
This thread has alot of good info. Thanks guys, I have a funaero Albatros DIII that I would like to go electric. The numbers seem to be good for my AXI 4130/20.

laxlife
11-20-2005, 06:16 AM
Yes, lots of good info. I had never thought the Axi 4130 would be enough moto for this plane but all this data is making me a believer. I'd much prefer a 17" prop to a 19 or 21" that the 5330 wants to swing. Keep the data stream coming I'm taking notes as fast as I can write.

Electrick
11-20-2005, 07:51 PM
Interestingly, I wrote Hobby Lobby back in the spring and asked what they recommended for a motor for the GP PT-17. They went straight to the AXI 5320. I was a little disappointed by that, since I felt the 4130 could do the job, and bought one (on sale) anyway.

The more I read about the 4130's capabilities, the more I'm convinced HL was simply overkilling their recommendation. Maybe they are also caught up in the popular paradigm of 'it has to have enough power to hover or it won't fly at all'.

Some folks just seem to have lost sight of the differences between a scale biplane and a YAK 55 3D model. ;)

Rick

chute42
11-20-2005, 08:19 PM
[quote=Electrick;23669]Interestingly, I wrote Hobby Lobby back in the spring and asked what they recommended for a motor for the GP PT-17. They went straight to the AXI 5320. I was a little disappointed by that, since I felt the 4130 could do the job, and bought one (on sale) anyway.

This is so true, and the 4130 flys it much more scale but at least Hobby Lobby isn't under powering it to save cost.
I just got back from maiden flight on Lancair #2 (Look here for Lancair# 1 http://www.dogon101.rchomepage.com/images/orca1105/lancairs_last_flight.MOV)
#2 is Axie 4130/16 8s 3700 lipo 14x10 MA prop it is pulling 49amps static. In the air it hauls a**:) I think it will be my new best friend. I feel confidant the 4130 will handle the Stearman very scale like with a little left over to get you out of trouble.
Chuck

rcers
11-20-2005, 08:57 PM
Chuck what happened???? Looked good till the last few seconds!

Mike

chute42
11-20-2005, 09:59 PM
Chuck what happened???? Looked good till the last few seconds!

Mike
Mike, the motor fried and caused a dead short across the batery this fried the ESC and the BEC the rest is history. #2 has an independant power system for the rx and with the Axie 4130 I am not pushing anything very hard. The 4120 was pushing 65amps and it burned out 3 windings.
All of this testing is where I got most of my info on what will work.
Chuck

Electrick
11-20-2005, 11:04 PM
Sorry to see that you found the AXI's current limit the hard way, Chuck.:o

That is certainly pushing the 4120 to the max. On any plane I build that's over about 5 to 6 lb. AUW, I use a separate receiver battery pack instead of any type of BEC, especially if I'm pulling anything over 40 amps static. The little bit of extra weight isn't a factor at or above this size, but the added safety factor and peace of mind if a motor or ESC meltdown occurs inflight certainly is.:D

Rick

chute42
11-21-2005, 12:36 AM
Yep! that was an expensive lesson. I have leared a lot.
Chuck

Electrick
11-22-2005, 10:58 PM
I just got a back issue of the July 2005 R/C Report magazine in the mail. I ordered it for the Great Planes PT-17 report in it.

The report says the review model came out to 220 oz. (13 lb, 12 oz.) AUW. The AUW figure includes 7.8 oz. of lead in the nose. They used a OS 120P 4 stroke for power, which weighs 33.6 oz.

Doing the math, that comes to 186.4 oz sans the slime factory in the nose.
Subtracting the lead, that brings us to 178.6 oz. That's just a little over 11 lb. bare firewall, but with radio, which is slightly better than my earlier calculations. The bare airframe minus radio and fuel tank should weigh in at well under 11 lb. :cool:

The article has some very good information about the ARF as a whole, and about the build sequence and manual. It isn't just simply a schmoozefest with Great Planes, as most other magazines' writeups on the PT-17 have been--this one has several criticisms of the plane. All are relatively minor and easily corrected, however.

Two other things that I plan to do to get weight out of the tail are to not use the steel wire joiner for the elevators, and substitute carbon fiber pushrods in the plastic sheaths instead of the steel wire ones. Rudder will be pull-pull cables, to save the weight of a third steel pushrod. I also plan to mount the radio much further forward in the fuselage, as the GP manual inexplicably shows it and the receiver battery mounted all the way aft in the fuselage compartment, when there's enough space to throw a block party in up forward. My 5-cell 1800 mah receiver battery/ballast will probably be riding up front in the ballast box on the firewall.

I want to investigate if there's a way of mounting the motor packs (two 4S2P LiPos) on the firewall somehow. I haven't thought this idea completely through yet. Needless to say, that would necessitate a removable cowl, which complicates things.

I would recommend getting this back issue if anyone is contemplating trying the GP Stearman/PT-17. It has some useful information.

Rick

rcers
11-23-2005, 02:36 PM
I want to investigate if there's a way of mounting the motor packs (two 4S2P LiPos) on the firewall somehow. I haven't thought this idea completely through yet. Needless to say, that would necessitate a removable cowl, which complicates things.

I bet you can, or at least get them hanging out at least partially. I depending on cowl size you may be able to build a shelf to get the whole pack out there (If necessary).

Mike

chute42
11-23-2005, 02:48 PM
I bet you can, or at least get them hanging out at least partially. I depending on cowl size you may be able to build a shelf to get the whole pack out there (If necessary).

Mike
That is pretty much how I installed the batteries in my Kyosho Super Stearman(PQ 3700 4s). I just plug it in to the esc or charger from the front of the cowling. It is kinda cool that the electric power system has cg issues because it is too light.
Chuck

Electrick
11-24-2005, 05:03 AM
I'm less concerned about how or whether I can mount the packs on the firewall, than how to create easy access to them once they are there. The necessity of being able to remove the packs for charging is what complicates things.

I've seen too many pictures and read/heard too many stories about LiPo fires burning up airplanes during charging. I would never build a LiPo powered airplane that I couldn't pull the battery from for charging--especially one with a high capacity 8S2P like this one will be.

But that's just me. :)

I'm sure I can come up with something. I was thinking of either clamshell hinging the cowl piece in halves, or making the cowl bottom removable, split horizontally, and retained by magnets. It may be that mounting them just behind the firewall will be adequate for balancing, allowing me to just cut a hatch on top of the fuse. This problem will have to be solved early on by experimenting.

Rick

Kamikazi
02-22-2006, 05:25 PM
Bought a GP Super Stearman about a year ago - been sitting on the shelf and I am finally getting around to it. Was gonna go gas, but then got the bright idea ;) So, I checked, and sure'nuff you guys are already doing it.

Here's my plan.

Hyperion Z4045-10 spinning APC 18x10

Castle HV-85

Power: 14 cells (7S2P) Molicel 3000 - weight ~1400 grams total

These are the new high power Milwaukee V28 Li-Ions used in power tools.
Some of the E-Heli guys are having great success (http://www.rcgroups.com/forums/showthread.php?t=456011) with packs built from these cells. The can be bought for around $95 per pack of 7.


Ran the numbers through Motocalc - 1800watts /265oz static. 67mph pitch speed. These round cells ought to fit nicely around the inside of the cowling.

Son of Paleface
02-24-2006, 06:34 AM
Rick , The split cowl with locating dowels and magnets works very well , but U must use neodinium super mag's

Electrick
02-24-2006, 04:08 PM
I wouldn't think of using anything but. :)

I am at that point right now where I have to decide where and how I want to do the batteries. I'm not a big fan of splitting the cowl, but it's an option. What I am looking into is perhaps a hole through the bottom of the firewall, and a hatch on the bottom of the fuse just behind it. What would be ideal is to not have to mount them forward of the firewall, but there's not much chance of this plane balancing without doing it that way.

I am doing some things to lighten the tail. I popped off the solid balsa tail block at the bottom and hollowed it out. I cut out and moved the servo tray forward, to just behind the fuel tank compartment. I am substituting CF pushrods for the steel ones, and using Kevlar pull-pull on the rudder (if I can get the routing right). I have considered cutting out some of the overkill ply substructure out of the aft fuselage as well, but haven't been able to bring myself to pick up the saw yet.

To be fair, I did add a tiny bit of weight to the stab, by adding some balsa airfoil-shaped capstrips to the top of it, so it looks less like a flat plate assembly. Really dresses up the looks a lot.

Darn batteries and motor are too light.:o

Rick

Hernthehunter
12-15-2009, 03:52 AM
Has anyone continued working on their Super Stearman's? I have one I would like to make electric. Needs total recover. Please let me know how your's turned out.

GOOD FLYING!!

av8djc
12-16-2009, 01:34 PM
Interesting thread because I'm thinking of resurrecting my 1/4 scale Dave Platt Bucker Jungmeister. I was going to go gas but it now occurs to me that Kamikazi has a great idea if I understand it right. With a round cowl built a bit sturdy from fiberglass and very solid cowl mounts one could mount the A123 batteries more or less permanently inside the cowl for ballast if that much weight is needed. They could be left in the airframe for safe charging. In the case of the Bucker I have a fuel tank box built in opening through the firewall that with luck could hold enough batteries.

I believe the A123's are safe to charge in the airframe right? They also respond well to a very fast charge so you wouldn't necessarily only get one flight per day because they are permanently mounted.

"What say you?"

Gwest
12-19-2009, 06:04 PM
Dave

I agree, putting them in the cowl is a good idea. Their weight and safer chemistry make A123 a winner. If the weight is not enough, consider using NiXX. These short-nosed planes that had radial engines are sometimes a pain to balance, even in slimers.

laxlife
12-20-2009, 04:04 PM
I converted a GP Super Stearman several years ago. I've tried a number of props and I have settled on a Mejzlik 22x12e which produces a top 2100 watts at 53 amps using this setup:
2, TP 5000 mAh 5s 18.5v lipos in series (10s)
AUW 17 lbs.
motor: Axi 5330-24
ESC: Phoenix 110HV
It is one of my favorite planes because it looks great, has gobs of power--NOT scale like, and is pretty easy to fly. I remove the wing to place the lipo bricks and its a pain but I love flying it so much that I have no problem de-rigging, removing the wings, changing to fresh packs and re-rigging. Probably 15 minutes roundtrip if I stay focused. Its a head turner too.
http://www.wattflyer.com/photopost/data/500/medium/GP_Super_Stearman.JPG