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New Baby Bee project - Fokker D.XXI - Page 3 Empty

New Baby Bee project - Fokker D.XXI

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Post  dirk gently on Sun Sep 15, 2019 8:00 am

1/2A Nut wrote:
Shame you don't have a good bit of clean pavement to use.

I do actually. I thought the rubber lanes would be better, but I was clearly mistaken.
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Post  getback on Sun Sep 15, 2019 9:13 am

Hopefully next time , am sure you were on edge from flipping flipping flipping Sad Popcorn
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Post  dirk gently on Wed Oct 02, 2019 5:29 am

The thing kind of flew, but it wasn't great. I gave up on ROGs and just tossed it. It sort of hung in there, with minimal aileron and elevator authority. Once the engine ran out of fuel, it basically turned into a lawn dart and crashed into the ground at a 30 degree down angle (elevator full up). The wing needs a major repair, bordering on a total rebuild. Didn't manage to catch any of that on video, which would help me find the root cause of the issue.

Action plan is: increase the throws on the ailerons and elevator. Check CoG in a calculator (although the CoG definitely isn't forward enough to explain the dive after power cutoff). It may need a slighly bigger horizontal stab. Sigh.  Sad
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Post  getback on Wed Oct 02, 2019 10:49 am

Hi Dirk , sorry to hear it did not go as planned . Is the Incidence set right to give it more lift??
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Post  dirk gently on Wed Oct 02, 2019 11:56 am

I built in my usual incidence of maybe 2 degrees on wing and 0 on the elevator, but I will double-check the angles before attempting to fly it again.
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Post  dirk gently on Sun Nov 10, 2019 10:13 am

It's alive!
I was on the airfield today and flew the Fokker with success. The engine runs great and the model flies terrific. The wing rebuild wasn't as problematic as I thought it would be, the worst part was having to remove and rebuild the entire landing gear. I couldn't be bothered to make new spats, but now that the plane has proved it flies, it will get some silhouette-style spat imitations. I don't have it in me to build proper 3d spats again.
The movable rudder wasn't terribly useful and I may get rid of it. The throttle works fine, but the model just about hangs in there on idle, so I can't actually land it by throttling down. I may need to reuse the throttle for a bigger or heavier model.
I only got one flight out it - due to all the excitement I thoroughly flooded it on the second try and couldn't star it is again. It was too cold to keep trying.
Here is the Fokker surrounded by its squadron on what is probably the last flying day of the season. I was flying alone, so sadly there's no video:
New Baby Bee project - Fokker D.XXI - Page 3 Img_2012

Summary of the flying day:
1. The Dewoitine got a new engine, same problem - wouldn't maintain RPM in the air, crashed the model.
2. Curtiss' Baby Bee is not running all that great, barely reaches 13kRPM (used to do 15k), but I registered a few flights, broke off the rudder on the last landing, no biggie.
3. The Morane and the Martin-Baker didn't get to fly, it was too cold and I decided to call it a day.
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Post  dirk gently on Fri Apr 24, 2020 2:44 pm

Finally, the Fokker got a flying day it deserved. I think I made about 4 flights with it. It's a good, steady flyer, and the glide rate is also great, considering the drag from the undercarriage.

Forgive me the poor video quality.

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Post  rsv1cox on Fri Apr 24, 2020 2:53 pm

Amazing the strength that you build into your stick and tissue models.
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Post  dirk gently on Fri Apr 24, 2020 3:07 pm

lol! Thanks! Those are probably the nicest words anyone has used to tell me my flying skills are rubbish. Don't worry, I know I suck at flying. Or maybe I don't suck at flying, just at landing - at least that's what my father-in-law, and actual fighter pilot once told me Very Happy

In my view, the key to survivability is not to build them strong, on the contrary: it's to build them light. Then when I inevitably smack them into the ground, they don't hit too hard!
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Post  rsv1cox on Fri Apr 24, 2020 3:29 pm

Or maybe I don't suck at flying, just at landing

Say that again. Your first video "landing" was a tumble. But at the speeds that you were flying at, landing is the world biggest chance for these little and very light models. .

Well done.

Bob
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Post  Champdriver on Fri Apr 24, 2020 6:49 pm

That's a great looking model of what I think is a fine example of a pre-war era fighter.
It's pretty hard to get good takeoffs and landings on such small wheels unless the pavement is super smooth, or you just land in tall grass to avoid damage.
Love the late 30's fighters like the Curtiss Hawk 36 and the Seversky P-35.
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Post  MauricioB on Fri Apr 24, 2020 10:22 pm

I congratulate you, I like your work. Its flight is also very good, I see on this landing that the model is very itchy, picking up speed and having a rigid runway, the model bounces without absorbing as if it were dirt or grass.
According to this trajectory, I ask you ?, what happens if you slow down the CG a little, that is, I see that it is very choppy, perhaps you can have a slower approach speed and be smoother when it comes to land.
New Baby Bee project - Fokker D.XXI - Page 3 Cg10
Huh...
New Baby Bee project - Fokker D.XXI - Page 3 Cg110
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Post  balogh on Sat Apr 25, 2020 12:50 am

Thank you for posting the video Dirk. Very nice plane and do not worry about landing. With planes of medium weight to surface ratio I always add some up elevator while landing. Allow me just one comment on the engine that as I heard may have run a bit lean..check if the needle valve stem seals well, and pull a silicone tube over the threaded spraybar end and the needle valve if the engine runs erratically and finding the sweet spot of the needle valve setting is difficult.

Way to go, happy flying!

Andras.
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Post  dirk gently on Sat Apr 25, 2020 1:47 am

MauricioB wrote:I congratulate you, I like your work. Its flight is also very good, I see on this landing that the model is very itchy, picking up speed and having a rigid runway, the model bounces without absorbing as if it were dirt or grass.
According to this trajectory, I ask you ?, what happens if you slow down the CG a little, that is, I see that it is very choppy, perhaps you can have a slower approach speed and be smoother when it comes to land.

Thank you for the advice. I don't think the landing was rough because of the CG, or anything about the flying characteristics of the model. I just really wanted to make it to the rubber lane part of the runway, rather then hitting the concrete next to it. To that end, I made a rather violent manouver in the last phase of the landing, and failed to level the flight in time. As a result, I did make it to the place I wanted to, but hit the ground while descending fast. The model has a nice glide rate and is predictable and smooth on a deadstick landing provided that it is kept level at all times.
I would be very concerned that moving the CG rearwards or indeed putting in up elevator while powered off would cause it to be prone to dropping a wing and entering a corkscrew. These low wings tend to track really well in powered flight, but need caution when landing powered off. In fact, I can land it pretty well each time, provided I don't try to land in any particular place, or turn close to the ground. Wherever the engine quits, I just level off, point the nose into the wind and go straight from there without any antics Smile
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Post  MauricioB on Sat Apr 25, 2020 2:13 am

dirk gently wrote:
MauricioB wrote:I congratulate you, I like your work. Its flight is also very good, I see on this landing that the model is very itchy, picking up speed and having a rigid runway, the model bounces without absorbing as if it were dirt or grass.
According to this trajectory, I ask you ?, what happens if you slow down the CG a little, that is, I see that it is very choppy, perhaps you can have a slower approach speed and be smoother when it comes to land.

Thank you for the advice. I don't think the landing was rough because of the CG, or anything about the flying characteristics of the model. I just really wanted to make it to the rubber lane part of the runway, rather then hitting the concrete next to it. To that end, I made a rather violent manouver in the last phase of the landing, and failed to level the flight in time. As a result, I did make it to the place I wanted to, but hit the ground while descending fast. The model has a nice glide rate and is predictable and smooth on a deadstick landing provided that it is kept level at all times.
I would be very concerned that moving the CG rearwards or indeed putting in up elevator while powered off would cause it to be prone to dropping a wing and entering a corkscrew. These low wings tend to track really well in powered flight, but need caution when landing powered off. In fact, I can land it pretty well each time, provided I don't try to land in any particular place, or turn close to the ground. Wherever the engine quits, I just level off, point the nose into the wind and go straight from there without any antics Smile

First of all, thank you for taking my comment for good!
Ahhh, I understand !!, the track was too small and he wanted to avoid the blow at the end of it. I fully understand your attitude.
So, ignore me, keep flying your model in this way with your CG so that you already have it controlled, which really will not have problems.
I understand the type of fine wing in the direction of the marginal edge, a gyro correction without motor, may make the model a stall.
I really enjoy their work, they really are beautiful and very good performance, that's why I wanted to collaborate with a positive opinion. Thanks again for your time and I will continue to enjoy your work and flights! ...
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