New Baby Bee project - Fokker D.XXI

The engine you sent runs great, I'm sure it will power this model with ease.

Nice work on the wing

Based on the dihedral and shape, I am guessing Mitsubishi Zero

That would be too easy!
It's something much less common

Maybe a PZL.50 Jastrząb?

I like that guess, but that one had an elliptical wing But, you're close, as the PZL 50 and this plane had the exact same engine.
I'm gonna show the fuse in a few days to make the guessing a bit easier.

Fokker D XXI

Last guess until I see the fuse.

OK, that was faster than I thought it would be
You really do know your planes!

No, I don’t know my planes, but I do know how to navigate the internet pretty well.
Your clue about the engine was a big help. That’s going to be a really neat build. I sure hope you have fun with it.

pzl 53

Hey Dirk, now you REALLY got my attention!

The XXI was a crucial part of the Finnish Defence during the winter war in 1939-40, and was widely used in the Continuation War too, although it did get a bit outdated towards the end. A rare plane, and I think the Finnish Air Force was the only one to use them in larger quantities.

Everything is relative of course, Finland bought 36 of them and 93 more were built under a licence here in Finland. What would be a ”large quantity” for a small country like mine, would be peanuts for others.

So, it is a great project for a model plane, and along the Brewster Buffalo, one of my favourite ”underdogs”  

Finland utilised some of my favourite WWII planes, including the Fokker and the M.S. 406, of which I built an (electric) model a short while ago.

So far the uncovered wing comes in at 40g while all the hardware weight is 110g. This means I have 100g left for the fuse and empennage, covering, fuelproofing and engine cowling if I want to make it within 250g. I'm not sure if I should be optimistic about being able to achieve that goal or not.

I will be using 9g servos for the ailerons and the elevator, because I have plenty of them laying around, and I'm out of 5g servos, which would be my preference. I'm going to run the throttle with a 3.7g servo, as the throttle poses next to no resistance so the 400g*cm torque should be plenty. I'm planning on moving the rudder with the same servo as the ailerons and see where that gets me, but I will make a slot for a separate rudder servo so that I can install it if I need to.

Nice project , she should look good when completed

I too am very interested in your D.XXI project! I had considered a 1/2A C/L profile-scale version for one of the CEF speed contests a few years ago.

Here's an image and 3-view that I'd found back then on the internet.




It's a rugged-looking.. yet handsome airplane in my opinion. Its' nose and undercarriage sort-of resembles a Ryan ST-A..

Little by little, the fuselage is coming together. The weight is 34g, not counting the servo.

When I was starting with this model I promised myself I wouldn't do the green-and-grey paint scheme that I seem to be doing almost every time. And yet, here I am, doing the green-and-grey paint scheme. I wasn't able to find anything suitable other than camo  (I hate doing camo, probably because I'm doing it wrong) or a solid colour, which is bad for orientation while flying. I decided on a Republican paint scheme from the Spanish Civil War. At least it has some wide red stripes on the wings and fuse to make it a bit less boring.

Loving this build Dirk!

Look forward to the flight vid!

Beautiful paper work. Can you tell us how you did it? Nitrate on edges? Dry covered in pieces? Just fabulous. I love this stage of a build. And I've removed less than acceptable covering before. Yours is what I WISH mine look like when I'm through.
Bravo!

I'm using plain domestic tissue, 22g/m^2 which is available in many different colours. Most of the colours are "happy" colours, if you will, not really the dull and earthy colours you'd typically find on a military plane, so I just pick the closest one that I can find, it's not the exact colour of the full scale though.
I put the tissue on using UHU stick glue, I cover in sections and make sure the tissue is as tight and wrinkle-free at this stage as possible. The glue gives plenty of working time to stretch and smooth out the tissue with your fingers.  

Once UHU stick glue is dry and excess tissue is removed, I give it a once-over with a thin cut of nitrocellulose dope. This shrinks the tissue resulting in a drum-tight covering. Then I apply a second coat of somewhat thicker dope to make the covering strong and somewhat resistant to moisture.

Note, the photos were made in dispersed light, which means no wrinkles or imperfections actually show up. I am happy with how the fuselage covering came out, but it's by no means perfect. Having said that, I have some pretty good tips on how to make a nice and tidy covering job:

- sanding the model smooth with 240-grit sandpaper prior to covering is crucial for a nice finished look - the tissue will wrinkle around any imperfections in the model
- gussets must be placed in corners of structures (you can see them well on the wings here), otherwise wrinkles will form radially from the corner
- structure can't be too sparse. Shrinking tissue exerts a lot of force on the underlying longerons, and will try to bend them inwards as it tightens. If it succeeds, wrinkles will appear running parallel to the longeron. Make sure the longerons are well supported with formers, use pine instead of balsa if needed. To me, this often happens on front-top fuselage. See this photo of my M.S. 410 as an example:

You can tell the longerons gave in to the shrinking tissue, there is some starved-horse look there, and wrinkles are running along the fuselage as a result.
- avoid using dope in humid weather, this will cause white, chalky strips to appear on the finish, which look nasty and can't be removed other than by re-covering the model. This is what happened close to the wingtip of my PZL 50:

Just a small update - I put the plane together provisionally 'cause I really wanted to see how it's going to look standing on its own two wheels. I mocked up the engine to give me an idea of where the CG is going to be and where do I need to put the throttle servo. Next update will hopefully be the completed model. Wish me luck!

VERY NICE sir! I've been following this build.. and I really like where it's going!

It does look good, I hope those little sticks are up to the torque of that .049.!

Your thinner is responsible for the blushing you mention in humid weather. Finding a slower evaporation thinner is your best option if possible. While it's best to avoid using it in humid weather all together it can be somewhat resolved by just dusting the model with straight thinner in a spray gun. This will open the top coat and allow the blush to escape. You can also spray some clear on a better day or just use retarder with the dope when your using it. I prefer not to use retarder due to it doing other things such as loosening the covering due to the longer open time it offers.

Cribbs74 wrote:I hope those little sticks are up to the torque of that .049.!

The fuselage is torsionally extremely strong, at least as if it were made of sheet balsa, if not more.
The wings are my standard construction, so I'm not expecting any issues there.