.40 size Ziroli P47 build thread. - RC Groups
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Sep 26, 2004, 05:59 PM
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RyanPSU21's Avatar

.40 size Ziroli P47 build thread.

I'm going to do this build along thread for my winter project. This is from March 1969 Flying Models designed by Nick Ziroli.

The plane stats are:
.40 size P47 Thunderbolt "near scale"
53" Span
520 Square inch wingspan.
The prototype was powered by a Merco .49 and weighed 5lbs 2 oz.

Mine is going to be powered by:
Mega 22/20/2
MEC 4:1 gearbox
APC 12x7e prop
14 GP3300
Castle Creations Phoenix 45
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Sep 26, 2004, 06:04 PM
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I am assuming the final weight to be 5 lbs 4oz. I plan on removing most of the plywood and downguaging a lot of the structure, plus no balsa blocks or hollowed out if I do go that route.

Below is my motocalc output for this. This is my first time trying to use motocalc so please point out if it appears I have done something wrong or have an unreasonable coefficient somewhere.

MotOpinion - Ziroli .40 P47
600ft above Sea Level, 29.92inHg, 57F

Motor: Mega AC 22/20/2; 2875rpm/V; 3.37A no-load; 0.012 Ohms.
Battery: Gold Peak GP3300; 14 cells; 3300mAh @ 1.2V; 0.005 Ohms/cell.
Speed Control: Castle Creations Phoenix 45; 0.0026 Ohms; High rate.
Drive System: MEC 4:1 + APC 12x7e; 12x7 (Pconst=1.08; Tconst=1) geared 4:1 (Eff=95%).
Airframe: Ziroli .40 P47; 520sq.in; 84.4oz; 23.4oz/sq.ft; Cd=0.044; Cl=0.4; Clopt=0.53; Clmax=0.99.
Stats: 112 W/lb in; 94 W/lb out; 25mph stall; 34mph opt @ 61% (32:32, 93F); 39mph level @ 69% (26:48, 99F); 1761ft/min @ 35.9; -303ft/min @ -5.8.

Possible Power System Problems:

The full-throttle motor current at the best lift-to-drag ratio airspeed (39.1A) is lower than the motor's maximum efficiency current (58.5A). A higher current level would improve system efficiency.
Current can be increased by using more cells, a larger diameter or higher pitched propeller, a lower gear ratio, or some combination of these methods.

Power System Notes:

The voltage (13.7V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (62mph) is within the range of approximately 2.5 to 3 times the model's stall speed (25mph), which is considered ideal for good performance.
With a wing loading of 23.4oz/sq.ft, a model of this size will have flying characteristics suited to the intermediate pilot, for use in calm to moderate wind conditions.
The static thrust (84.8oz) to weight (84.4oz) ratio is 1.01:1, which will result in very short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and steep climb-outs.
At the best lift-to-drag ratio airspeed, the excess-thrust (47.9oz) to weight (84.4oz) ratio is 0.57:1, which will give steep climbs and excellent acceleration. This model should be able to do consecutive loops, and has sufficient in-flight thrust for almost any aerobatic maneuver.

General Notes:

This analysis is based on calculations that take motor heating effects into account.
Sep 26, 2004, 06:06 PM
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Here are the actual plans layed out on my recently cleared off work table. They are actual blue-print instead of zerox or computer printout.

Sep 26, 2004, 06:09 PM
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Today I traced out all the wing parts except for the ailerons onto Reynolds Freezer Wrap which is paper with one waxy side. The traced parts will be next ironed onto the wood with the waxy side, cut out, then the leftover paper is pulled off.

Sep 26, 2004, 10:46 PM
Involuntary Beta Tester
I'm not sure this is the right Mega motor. The 22/20/2 is used in a lot of 400 watt applications and I'm not sure about a 640 watt application. A 22/30/2 might be worth running the numbers. A little heavier but it can handle the heat although you'll have excellent cooling with the big open cowl. Are you planning retracts?

I'm not sure 5lbs 4oz is reasonable. Even a lightweight kit such a Seduction freestyle which is a little bigger came in at 90ozs with 16 cells. 6lbs may be a more realistic weight. Once you start building it and can weigh the major components you'll have a better idea.

Sep 27, 2004, 05:28 AM
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According to Mega's website, it is good for 14 cells to 70 amps.

14 Cells Maximum, 70 Amps Maximum Standard 5mm shaft. Designed for 6 - 8 cells Direct Drive or Geared and EDF to 600 Watts A hot rod for low cell count

There shouldn't be any problems with cooling it with the cowl configuration.

I am going to build it first with fixed gear to make sure it flies okay. Then I will build a second wing with retracts. Retracts are going to require some considerable rework of the wing structure as the distance from the spar to leading edge is not great enough to put any kind of decent diameter wheel. I will have to offset the spar for part of the wing similar to what is done on the plans I have for a Ziroli 72" P47.
Oct 02, 2004, 07:47 PM
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Got some time to work on it again.

The wing is now in "kit" form with all the parts cut out.

Oct 02, 2004, 07:54 PM
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Plans layed out on the workbench and ribs layed out. Plywood doublers glued to the landing gear support ribs.

Ribs glued to the lower spar and to the wing joiner. The design of the joiner is such that is is slotted into the ribs and difficult to add post construction so I am going to build one wing half. Then I will prop it up on the workbench and build the other half onto it.

The original design does not use shearwebs. I'm debating if they are necesary or not. The plywood joiner extends 2 ribs bays. The wing will be sheeted but I am only going to use 1/16" instead of 3/32" and the ribs are only 1/16" instead of 3/32". Wood is medium to soft but definetely not contest weight. Ordered from Balsausa.
Oct 02, 2004, 07:56 PM
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What would people recommend for an AXI power system for this plane? I am debating on updating to an AXI so I can leave my Mega 22/20/2 in my LT-25.

What would people recommend for Lipo's for this? I am still planning on nimh cells but am considering buying Lipo which I have never used before. In which case the Mega 22/20/2 will definetely stay in because I can't afford a new motor and lipo for this project.
Oct 02, 2004, 08:16 PM
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I think it would be better for you to use a 30-2 or 30-3 mega.

I had a 6+ lb plane that I flew with a belt-drive and 15 cells. The extra weght of the larger (longer rotor) is insignificant and will be better than a smallermotor pushed too hard. Why such a high gear ratio? Why not a 3 wind and 2-1 like I ran? I was swinging a 13-10 with the Jeti 30-3 which is lower KV

You can get a horsepower out of the 30-3 mega on 14 cells. I would be lookinng at a separate battery and a optocoupled ESC so you can add cells if you need to get more power. And at least a 40 amp esc.

The LIPO's will be ridiculously expensive. I would just use a c cell NIMHG like the GP3300, which will work to fly the plane for 8 to 10 minutes if I had to guess.

You will need a big AXI. The 2820-10 won't fly a plane this big well. Maybe a 6 lb trainer.
Oct 02, 2004, 10:42 PM
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This looks like the P47 I have. It was a Ziroli designed kit from the early '70's I think. It was manufacturered by a company that picked up the rights to Nick's published plan. I flew it on an OS .50 and had a bad crash (real goofy incident). It sat on the shelf for about 2 years. I then pulled it off the shelf, did some major lightening and made a new nose and cowl. It flies very well on a Mega 22/20/2 geared at 3.8:1 or 4:1 (I can't remember the ratio) on 10 cells. (I'm planning on flying tomorrow as a matter of fact).
The highlight of its career was at last year's NEAT when I flew in front of Nick Ziroli. Needless to say there were smiles all around.
Here a link with some more details-
It has markings and some panel line details since the pic in this thread was taken.
Oct 02, 2004, 11:39 PM
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I'm using the motor 22/20/2 and 4:1 ratio because it's what I currently am using in my LT-25 so I have it available. This plane doesn't really appear to be a true .40 size by today's standards. It is more like a .30 size plane. It is 38" long by 52" span by 520inch^2. By comparison Great Planes P51 is 50" long and 57" span and 580inch^2. I did play with altering the gear ratio on motocalc and went to a higher ratio and bigger prop but started giving me statements about unfavorable flight characteristics. I'm currently running 10 cells and the motor is rated to 14. I would go to 16 which is then the limit of the ESC I have (CC Phoenix 45) and I'll be adding a reciever battery since it is only good with BEC to 10 cells. I could try to fly it with 10 cells but I was thinking of bumping up to 14 and getting a little more oomph. I know Lipo will probably be somewhere around $200 from my guesses at what to use which would be something like a 2000mah 5S2P or 4S2P (I may be way off with this guess, I've never used Lipo and am still somewhat unsure about how to pick cells) but if I do it, I want to do it to save weight, not gain duration. Since I'm not sure how the weight of those compare to GP3300's I'm not sure if there is benefit or not. My reason for getting an AXI would be so I can leave the motor and gearbox I currently have in my other plane and only have to keep the ESC portable. I figure to go AXI I would want something like the 412014. I'm also considering an MEC motor B36-40-2670 or B36-50-2900. I already have a 10cell GP3300 pack with 30 or so flights on it so to go more cells I am going to get a 4-6cell pack to add to it. But I need to decide before I start building the fuselage in a few weeks so I can design in a battery compartment/hatch and cooling air duct.


I found the plans for these after seeing your thread before. It's my winter project but at the rate I'm going it will probably by my until Christmas time project. Do you know how much your's weights?
Oct 03, 2004, 03:42 PM
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My comes in at 5lbs with 10 cells. Now I can't remember if that's with the CP1700 pack or the GP 3300 pack. What ever you make sure you lighten things up. As I said mine was originally on wet power and I built it early in my RC career, so it was heavy. When I electrocuted it I lightened the ribs by cutting out some of the center material, I put lightening holes in the wing sheeting and in the sheeting on the rear fuse. I don't know what your plans call for but my plane was planked with some pretty thick stuff (I think it might have been 3/32 strips). I had to sand the heck out of it to loose weight. I would recommend on 1/16 planking. That would impart alot of strength and not too much weight.
I flew it today. Unfortunately the grass at our field was really thick (not long ) and wet so it nosed over on landing and I broke the PVC tubing motor mount I had made. I have to make a new one now.
I'm going back to check on the gear ratio (heck the motor is out of the plane now) to see what I was using. I'm thinking about going to 12 cells to give it some more zip. I haven't used LiPos yet either so I'm still worried about weight when I add cells. I'd be really interested in hearing about the MEC motor if you use it. I've been eyeing them but not many people are using them. I'm getting my first AXI shortly and I've seen them work and know they're good. I've also seen one of the Kontroniks motor that Tower sells and was pretty impressed with it.
The plane really flies well you ought to enjoy it.
Oct 03, 2004, 04:21 PM
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The fuselage sides are 3/23" or 1/8" per the plans and so is the planking. I'm not planning on using anything greater then 1/16". I also reduced all the wing sheeting to 1/16" instead of 3/32".

Per the plans the wingtops are cut from 1" soft balsa. I am going to laminate some 1/16" x 1/4" strips, 3 or 4 layers to make the outline and then cut a few support strips. I'm going to laminate and do builtup tailfeathers as well since they are also 1/4" sheet per the plans. There are also some large carved balsa chunks in the fuselage, mainly the nose in front of the wing. There is lots of easy to remove weight. I don't trim wing ribs since I did it before and the weight saved across all the ribs was very minimal for the effort it takes. I want to build the fuselage with a top hatch and sort of an airduct built into the structure and battery tray similar to what is in the Fusion fuselage.

I think I will try the MEC motor and see how it goes. There combo with the superbox is not to expensive. That is where I have gotten the 2 Mega brushless motors I currently have. Their gearbox is excellent so hopefully their motors will hold up good as well.
Oct 23, 2004, 06:16 PM
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I finally got some more time to work on this. The left half wing top sheeting and cap strips are applied. I am now starting to build the right half onto it. The lower spar is glued to the joiner and I'm waiting for the ribs with plywood doublers for the landing gear to dry. I have switched from CA to using woodglue now based on a lot of posts on here and realizing that I am getting a runny nose every time I work on this thing and my workroom does not have the greatest of ventilation.

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