PZL 62 + Baby Bee

dirk gently Wed Feb 15, 2012 7:59 am

OK,

I started drawing plans for a Polish PZL 62 that I'm intending to build. I am not an experienced model maker, so any feedback/constructive criticism is welcome and will be appreciated.

A little background story:
The PZL 62 was supposed to be a fighter airplane, powered by a Hispano-Suiza 12Z engine, (which was not existent yet at the point where the plane project was conceived). The engine was expected to develop as much as 1600hp, and the expected top speed was about 600-650km/h (about 400mph). It was supposed to be introduced in 1942, which of course never happened due to outbreak of the war and the fall of Poland. This project is intended to be a sort of continuation of this plane's story.

This is what the plane was supposed to look like: http://www.modelbud.pl/modelbud/kataloga/A55.jpg
Wikipedia article (in Polish): http://pl.wikipedia.org/wiki/PZL-62
A foam model built by one of Polish model makers (also in Polish, but the photos are kind of nice, electric powered): http://pfmrc.eu/viewtopic.php?t=25454&postdays=0&postorder=asc&start=0

Plans are available here: http://japim.acn.waw.pl/modelarstwo/plany/p62.zip but these are for 1m (3ft) wingspan, a 2.5cc engine and the construction method is balsa-foam sandwich. So I need to scale them down and convert to full balsa.

Main project assumptions are:
Wingspan: 65cm (25 1/2 inches)
Wing area: 8dm2 (125 sq. inches)
Expected mass: 200g (8 oz)
which includes: 90g (3 1/2 oz) for the hardware, the rest for the airframe
Wing loading: 25g/dm2 (~8 1/2 oz / sq. foot, if my calculations are correct)
Power: Cox Babe Bee .049 + 6x4 prop.

If this sounds unrealistic/absurd/ridiculous please feel free to rant Smile

I will post what I already drawn later today or tomorrow.
thanks.

nitroairplane Wed Feb 15, 2012 8:04 am

Before I answer anything we may know is it :RC,CL or FF?
Indra

dirk gently Wed Feb 15, 2012 8:17 am

Ah, right, forgot that one. It's supposed to be a 2ch RC (ailerons + elevator).
Maybe it's my imagination failing me, but I actually can't imagine that plane to be an FF. Before the fuel runs out, the model would probably be already on other side of the city Smile

nitroairplane Wed Feb 15, 2012 8:27 am

You trim an FF model to do circles and not fly straight.
But the engine and prop choice is a bit much especially as you say you are not try experienced.
For an 8oz intermediate plane you want a pee wee .020 or tee dee .020 or it will e on the other side of the city by the time your launch hand gets back the controller.
Indra

dirk gently Wed Feb 15, 2012 8:46 am

I realize it may be a bit difficult. I have an electric trainer to learn the basics. Sadly, I don't have a .020, I will probably need to work with what I have.

nitroairplane Wed Feb 15, 2012 8:49 am

Okay then maybe increase size and therefore weight.
Or you can mount the prop backward and run rich to reduce the efficiency therefore thrust.

dirk gently Wed Feb 15, 2012 9:14 am

I don't feel like spoiling the aircraft by running the prop backwards, it would be almost against my religion. I will consider making it a bit larger, also, do you think a smaller prop (like 5x3, which is also recommended for this engine) would help tone it down a bit?

Also, I found this video:
https://www.youtube.com/watch?v=oyK1QBtba-8
where the model seems to have a similar size and weight, so I guess it's doable? I mean, I can make it larger, but I know people who would fit a 2.5cc into a 80-90cm wingspan airframe, so my 0.8cc doesn't seem excessive at all. Perhaps they are better pilots than I am.

Anyway, I will have it maidened and trimmed by someone more skillful than myself.

Thanks for the feedback Smile

nitroairplane Wed Feb 15, 2012 9:33 am

Yes it can be done but you said you are not very experienced.
I have had a babe bee on a 20" but very quick!
Just look what happened to Jareds .051 powered stik Smile

Indra

dirk gently Wed Feb 15, 2012 9:52 am

Yep, I read that thread.
OK, so I will keep the size as it is, fit a smaller prop. I have a good chance of getting my hands on a .020 before the ARF is finished.
I promise not to fly it until I'm skillful enough for it to have a decent chance of survival.
Thanks for all the input!

nitroairplane Wed Feb 15, 2012 9:57 am

Good luck with it ad I would love to see pics!

John Goddard Wed Feb 15, 2012 10:02 am

dirk gently wrote:I don't feel like spoiling the aircraft by running the prop backwards, it would be almost against my religion. I will consider making it a bit larger, also, do you think a smaller prop (like 5x3, which is also recommended for this engine) would help tone it down a bit?

Also, I found this video:
https://www.youtube.com/watch?v=oyK1QBtba-8
where the model seems to have a similar size and weight, so I guess it's doable? I mean, I can make it larger, but I know people who would fit a 2.5cc into a 80-90cm wingspan airframe, so my 0.8cc doesn't seem excessive at all. Perhaps they are better pilots than I am.

Anyway, I will have it maidened and trimmed by someone more skillful than myself.

Thanks for the feedback

Not sure if you understood Nitro's backwards prop comment Dirk.
He means to turn the prop around to face backwards on the prop driver.
This makes the prop much less efficient therefore tones the power
down a bit. I think you'd need VERY good eyesight to spot that
just looking at the plane.
Very Happy

dirk gently Wed Feb 15, 2012 10:18 am

As I said, it's not about appearance, it's about religion Smile

I'm an engineer and I am a strong believer in using the right tools for the job, not using hacks (the reverse propeller would obviously be a hack) etc.
I will simply mount a smaller prop.

**Cribbs74** Wed Feb 15, 2012 10:30 am

dirk gently wrote:As I said, it's not about appearance, it's about religion
I'm an engineer and I am a strong believer in using the right tools for the job, not using hacks (the reverse propeller would obviously be a hack) etc.
I will simply mount a smaller prop.

Wouldn't a smaller prop increase RPM's thereby increase thrust? I thought that's how it worked....maybe just playing around with pitches would work?

microflitedude Wed Feb 15, 2012 10:36 am

cribbs74 wrote:
dirk gently wrote:As I said, it's not about appearance, it's about religion
I'm an engineer and I am a strong believer in using the right tools for the job, not using hacks (the reverse propeller would obviously be a hack) etc.
I will simply mount a smaller prop.

Wouldn't a smaller prop increase RPM's thereby increase thrust? I thought that's how it worked....maybe just playing around with pitches would work?

You'll get more speed, less torque with a small prop. If you want to slow the plane down, put a bigger prop on it with more pitch.

dirk gently Wed Feb 15, 2012 12:42 pm

Ok, bigger prop it is Smile

Mark Boesen Wed Feb 15, 2012 6:32 pm

dirk gently wrote:As I said, it's not about appearance, it's about religion
I'm an engineer and I am a strong believer in using the right tools for the job, not using hacks (the reverse propeller would obviously be a hack) etc.
I will simply mount a smaller prop.

...so your gonna use a .049 because you have it, when you really should be using a .020 for your specs?

For a .049 2 channel R/C you should be looking 230-250 sq. in. wing, unless you want to go racing.

I watched the video you linked, if the guy flying knew how to set the needle, the guy filming wouldn't be able to track it.

REMEMBER: As a rule of thumb: Pitch for Speed, Diameter for RPM

A smaller prop same pitch, will give you more RPM and likely more speed. If you want to slow it down, go larger diameter, smaller pitch.

Mark Boesen Wed Feb 15, 2012 6:35 pm

microflitedude wrote:
cribbs74 wrote:
dirk gently wrote:As I said, it's not about appearance, it's about religion
I'm an engineer and I am a strong believer in using the right tools for the job, not using hacks (the reverse propeller would obviously be a hack) etc.
I will simply mount a smaller prop.

Wouldn't a smaller prop increase RPM's thereby increase thrust? I thought that's how it worked....maybe just playing around with pitches would work?

You'll get more speed, less torque with a small prop. If you want to slow the plane down, put a bigger prop on it with more pitch.

less pitch

dirk gently Thu Feb 16, 2012 1:11 am

You convinced me.
I have three choices now:
1. make the plane larger. for 250sq inches it would have to have a wingspan of approx. 3ft Sad

2. find a .020
3. get a .049 with RC throttle.
I kind of like the last idea, what do you think?

nitroairplane Thu Feb 16, 2012 3:31 am

dirk gently wrote:You convinced me.
I have three choices now:
1. make the plane larger. for 250sq inches it would have to have a wingspan of approx. 3ft
2. find a .020
3. get a .049 with RC throttle.
I kind of like the last idea, what do you think?

I think yes and get one from Bernie with a type B conversion head.

dirk gently Thu Feb 16, 2012 3:58 am

Cox Bombers (Sure Start with RC throttle) are readily available in Poland, and quite a bit cheaper than Babe Bees as well Smile

dirk gently Thu Feb 16, 2012 4:23 am

Here's the wing I drawn:
https://rapidshare.com/files/3788012236/PZL62-Wing.PDF
Sorry about the quality of the scan, I only have access to an A4 format scanner at the moment. I don't know how to attach files directly to the forum, so I used rapidshare instead.

Construction:
- a double 3x3mm (1/8in.) pine spar. Isn't that sort of thickness a bit over the top?
- 1.5mm (1/16in.) balsa ribs. There are six ribs and two half-ribs per wing.
- 2mm (~3/32in.) thick balsa trailing edge
- 2x4mm (~3/32x3/16in.) balsa leading edge
- 5 degrees dihedral
- spar join reinforced with 1.5mm (1/16in.) plywood.
I think I will cover it with Oracover film.

EDIT:
and here's a crude drawing of the fuselage (I wouldn't call it a plan):
https://rapidshare.com/files/2336556892/PZL62-Fuse.PDF
Construction:
- sides and bottom out of 1.5mm (1/16in.) thick balsa sheet
- top formed of 2x2mm (3/32in.) stringers
- firewall (and all the other *walls - forgot the English name for it) 1.5mm (1/16in.) plywood.

EDIT2:
Is the forum doing something weird to rapidshare links? In the post source the link is correct, but when I click it in the post, I get redirected to a suspiciously looking page...

Mark Boesen Thu Feb 16, 2012 9:47 am

Hi Dirk,
Another, old saying: Elbows and opinions, everybody’s got a couple. …so here’s mine.

Putting a ‘large’ .049 in that small of plane is going to create more problems than solve, higher wing loading, additional structure, poor glide, etc. If you’re fairly new at this hobby, I’d think you’d be better off with a gentler flyer, not a rocket, something that would give you time to respond.
If you enlarged your plans to say, a 32-34” wing it would be a lot easier to fly (remember little planes get little, really quick) and it would handle the wind better then a smaller ship.
I just build a small electric from free flight rubber band design (see model section) it’s a neat little plane, but in hindsight I wish I built it larger.

Good luck!

John Goddard Thu Feb 16, 2012 10:01 am

Mark Boesen wrote:Hi Dirk,
Another, old saying: Elbows and opinions, everybody’s got a couple. …so here’s mine.

Putting a ‘large’ .049 in that small of plane is going to create more problems than solve, higher wing loading, additional structure, poor glide, etc. If you’re fairly new at this hobby, I’d think you’d be better off with a gentler flyer, not a rocket, something that would give you time to respond.
If you enlarged your plans to say, a 32-34” wing it would be a lot easier to fly (remember little planes get little, really quick) and it would handle the wind better then a smaller ship.
I just build a small electric from free flight rubber band design (see model section) it’s a neat little plane, but in hindsight I wish I built it larger.

Good luck!

Sage advice Mark
Very Happy

dirk gently Thu Feb 16, 2012 11:39 am

Can't really argue with what you all say. So I sat down and redrawn the plans to about 33in. wingspan. If I don't come across a .020 really soon, i'm going to build a larger version.
Thanks.

nitroairplane Thu Feb 16, 2012 11:45 am

Cool!
You are more likely to be successful now.

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