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Fokker V.23 + MARZ 2.5D Empty

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Fokker V.23 + MARZ 2.5D Empty Fokker V.23 + MARZ 2.5D

Post  dirk gently Wed Feb 24, 2021 1:21 pm

Hello,

I hope this is the correct place for this topic.
I'm in the process of making a 1m (40'') Fokker v.23 (or maybe v.25 - we'll see, they both have the exact same wing, so I still have time to decide) powered by a MARZ 2.5 Diesel I bought factory new and manage to get running.
Fokker V.23 + MARZ 2.5D 892c5f17123717.562ecf7003c9b

Here's the progress so far:
Fokker V.23 + MARZ 2.5D Img_2053
Fokker V.23 + MARZ 2.5D Img_2055
Fokker V.23 + MARZ 2.5D Img_2054


Last edited by dirk gently on Fri Apr 02, 2021 8:21 am; edited 1 time in total
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Post  Ken Cook Wed Feb 24, 2021 3:24 pm

I've always wondered how the Marz runs. I had a Meteor ( Glow version ) which I enjoyed a lot. I sold the engine and regret it. The Meteor was also made in a diesel version. It's to my understanding that many of these engines were used for teaching machine skills. Even my Chinese Silver Swallow does quite well once it was broken in. It seems to take a eternity.
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Post  dirk gently Thu Feb 25, 2021 12:58 am

The engines were made because modelling was a strategic activity in the USSR, being seen as a way to attract kids to engineering and military careers. There is a magnificent article by Adrian Duncan on this engine, giving a detailed historical perspective and many technical details: http://www.modelenginenews.org/ad/marz.html


As with many soviet artifacts, the design is pretty clever, but the manufacturing quality varies wildly. I hear these can go up to about 0.33hp swinging a 8x4 at 14000rpm, but I've also seen reports of much poorer performance. Mine seems to be somewhere in the middle, doing about 0.25hp at 12500rpm. This gives over 0.8kg of thrust, which should be ideal for this application. Weight, thrust and power- wise it's about equivalent to three Baby Bees, and perhaps I can squeeze a couple hundred rpms more from it.
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Post  dirk gently Thu Feb 25, 2021 10:22 am

Guys,

looking at the first image at the top of the thread,
does it look to you like on the picture the top aft fuselage behind the cockpit is flat with a tall headrest fairing, whereas on the drawing the fuselage cross-section is curved there, with a much shallower fairing?
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Post  Oldenginerod Thu Feb 25, 2021 3:05 pm

@dirk gently wrote:Guys,

looking at the first image at the top of the thread,
does it look to you like on the picture the top aft fuselage behind the cockpit is flat with a tall headrest fairing, whereas on the drawing the fuselage cross-section is curved there, with a much shallower fairing?

Looks that way. I like the curved upper decking better as it matches the upper fuselage in front of the cockpit.
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Post  gkamysz Thu Feb 25, 2021 3:28 pm

The cockpit opening is creating the illusion the rear decking is flat. It looks like the fuselage has constant cross section to the front of the cockpit.

If you saw my comment before, disregard it. Seems like it's virtually identical to the DVIII.

Fokker V.23 + MARZ 2.5D Primed
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Post  getback Fri Feb 26, 2021 8:41 am

This should bee good looks like an interesting model of the error . Popcorn
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Post  dirk gently Sun Mar 07, 2021 1:58 pm

Here's the progress report.
The gear will be just short of 300g. If I can keep the airframe within the same limits, I can have 550-600g of AUW, which should give me great flying performance.

Fokker V.23 + MARZ 2.5D Img_2056
Fokker V.23 + MARZ 2.5D Img_2057
Fokker V.23 + MARZ 2.5D Img_2058
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Post  getback Mon Mar 08, 2021 8:38 am

Looking good !! That stick airframe sure looks delicate , but i am sure it will stiffen up after covered , what is the engine on the front ? Very Happy
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Post  dirk gently Sat Mar 13, 2021 3:12 pm

@getback wrote:That stick airframe sure looks delicate , but i am sure it will stiffen up after covered

Actually, the airframe is extremely rigid, both laterally and torsionally. I have added all the cross- and diagonal pieces and the fuselage is completely stiff, would probably break before flexing, and believe it would take a considerable force to break it. I originally planned on making the longerons out of 4mm square pine, but I'm happy I went with 3mm in the end. The fuse is much stronger than my typical balsa slab-sided fuses, and very light too.

I don't really like relying on covering to stiffen up the structure, as I believe that can be deceiving. The fuse or whatever seems fine on the bench, then you take it flying, the weather is a bit damp, the tissue slackens off and you know longer have the strength benefit of the covering. In my opinion, the airframe needs to be built in such a way that it's strong enough without the covering.

The name of the engine is in the title of the thread Wink
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Post  getback Sun Mar 14, 2021 8:23 am

Cool , i feel the same way about the frame and Not relying on the covering to strengthen it up >> This is funny >>
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Post  dirk gently Tue Mar 16, 2021 5:17 am

It's funny when it happens to other people Wink
BTW, the sound on the video is very poor, but as far as I can tell the engine is hitting 14.5k RPM just before taking off, which is impressive.
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Post  dirk gently Tue Mar 23, 2021 5:26 am

I'm making steady but slow progress. I'm still on course to not exceeding 600g AUW (not by much, anyway).

Fokker V.23 + MARZ 2.5D Img_2059
Fokker V.23 + MARZ 2.5D Img_2060
Fokker V.23 + MARZ 2.5D Img_2061
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Post  getback Tue Mar 23, 2021 5:52 am

The Fokker is looking really good , has nice curves to it and you have brought them out ! So it will bee a mid wing ? Doing a good job with the weight also . Very Happy
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Post  dirk gently Fri Apr 02, 2021 4:16 am

Hello,

this is probably the penultimate update before the model is completed:
Fokker V.23 + MARZ 2.5D Img_2065
Fokker V.23 + MARZ 2.5D Img_2064
Fokker V.23 + MARZ 2.5D Img_2066

Current weight is 580g, including all the gear.
I may need new wheels, the ones I have are 60mm, scale would be 80mm, but I can't find any that are light enough and the correct shape. I may need to manufacture a pair out of foam and some plywood.
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Post  OVERLORD Fri Apr 02, 2021 6:13 am

Great job Dirk. and colourful!
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Post  OVERLORD Fri Apr 02, 2021 6:19 am

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Post  dirk gently Fri Apr 02, 2021 6:23 am

yeah, these would be perfect, but they're not available, and would be more expensive than the engine.
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Post  getback Fri Apr 02, 2021 6:42 am

You did another fantastic job on the covering , i think ur the one and only on the forum that does pretty much all your models in stick and tissue . Look forward to the maiden flight ! RC Plane This Site Rocks!
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Post  dirk gently Fri Apr 02, 2021 7:18 am

@getback wrote:i think ur the one and only on the forum that does pretty much all your models in stick and tissue

That's because I really suck at using film covering.
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Post  dirk gently Sat May 01, 2021 2:03 pm

And it's done!
Well, sort of. It will receive a pilot, scale-sized wheels and perhaps even machine guns and an instrument panel when/if it proves it can fly well. Feast your eyes, one way or the other, it's never gonna look as good as it does now:

Fokker V.23 + MARZ 2.5D Img_2069
Fokker V.23 + MARZ 2.5D Img_2067

And this is how it compares against the original:
Fokker V.23 + MARZ 2.5D 892c5f17123717.562ecf7003c9b
Fokker V.23 + MARZ 2.5D Img_2068

BTW, the weight is bang on 600g
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Post  dckrsn Sat May 01, 2021 6:34 pm

cheers Gorgeous, Dirk!!
She'll be a beauty in a blue sky.
If you cluck on some of the images here, you might
find a useful link.
https://images.search.yahoo.com/search/images;_ylt=A0geKLsu5o1gPd0AcWdXNyoA;_ylu=Y29sbwNiZjEEcG9zAzEEdnRpZAMEc2VjA3Nj?p=williams+bros+model+wheels&fr=mcafee
Bob
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Post  getback Tue May 04, 2021 8:24 am

Sweet !! I think you pined it looks Great hope the maiden goes well ! RC Plane Weight came out really good too .
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