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Author Topic: The bluefoam model, or how to build a stunt plane without a bit of balsa?  (Read 30982 times)

Offline Avaiojet

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #50 on: January 01, 2019, 01:16:10 PM »
Dear Friends & Visitors,
I wish you Happy New Year in 2019!
Istvan

Istvan!!

Hey! Hey!

Happy New Year!

I was just thinking about you reading this Thread.

Like "Back to the Future,"

"Roads? Who needs roads."

"Balsa? Who needs balsa."

With the right design, I might just do it.

Charles

Trump Derangement Syndrome. TDS. 
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If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #51 on: January 01, 2019, 01:55:32 PM »
Dear Charles,
Nice to see your lines and thoughts again!
Well, 2018 went by some extreme happenings to me.
I took part in World Championships (Landres, France), with miserable result in Aerobatics, however, I stood at the top of the podium, as team manager of Hungary: our speed team (F2A) won the Championship.
https://www.flickr.com/photos/fesselflug/42627934605/in/album-72157699277330325/
 
« Last Edit: January 01, 2019, 02:34:07 PM by Istvan Travnik »

Offline Target

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #52 on: January 01, 2019, 03:08:02 PM »
Congrats on the speed team win, Istvan!
Regards,
Chris
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Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #53 on: January 01, 2019, 04:23:41 PM »
Thanks,
But I was really only helper of our speed (and complete combat, F2D) team.
Technical "guru" of our boys was the old Jozsef Mult: in the '80s his team was absolutely winner, e.g. in 1984, Chicopee, they were No. 1-2-3 placed!
 

Offline Avaiojet

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #54 on: January 01, 2019, 04:39:25 PM »
Thanks,
But I was really only helper of our speed (and complete combat, F2D) team.
Technical "guru" of our boys was the old Jozsef Mult: in the '80s his team was absolutely winner, e.g. in 1984, Chicopee, they were No. 1-2-3 placed!

Istvan,

I have Windows 7 and cannot get into Flicker to view your photos.

Anyone have suggestions?

Charles
Trump Derangement Syndrome. TDS. 
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Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Target

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #55 on: January 01, 2019, 05:45:21 PM »
It works on Windows 10, just an FYI.
Regards,
Chris
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Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #56 on: January 01, 2019, 06:08:22 PM »
Dear Charles,
I work mostly with Win XP.
Here is start page of Claudia Kehnen:
https://www.flickr.com/photos/fesselflug/

Otherwise, try to google her, you will see her all best quality albums!

Offline Avaiojet

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #57 on: January 01, 2019, 06:34:26 PM »
It works on Windows 10, just an FYI.

No luck with that other link.

My wife has Windows 10.

Charles
Trump Derangement Syndrome. TDS. 
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Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Target

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #58 on: January 01, 2019, 09:26:01 PM »
Second link works on 10 also.
Regards,
Chris
AMA 5956

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #59 on: January 02, 2019, 04:46:25 AM »
Maybe,
https://www.flickr.com/
needs some sign up, I do not know.
IMHO Claudia Kehnen and Natasha Salomatina are the most active photographers of Control line events, with very good selection taste (at least in Europe).
Natasha & albums can be found on facebook...

Offline Brett Buck

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #60 on: January 10, 2019, 12:30:22 AM »
Istvan,

I have Windows 7 and cannot get into Flicker to view your photos.

Anyone have suggestions?

Charles

  It is not a problem with your operating system, maybe with your browser. Try Chrome or Firefox instead of IE.

    Brett

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #61 on: December 31, 2019, 06:12:31 PM »
Dear Friends,
I wish you Happy New Year in 2020!

In 2019 there were not too much happened technically with me, but, finally I had to abandone my model's  double fins with their strongly undercambered airfoil.
I can tell the story of "how and why", if interested. Maybe the conclusions can be useful to all of us...
Istvan

Offline Avaiojet

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #62 on: December 31, 2019, 06:42:43 PM »
Dear Friends,
I wish you Happy New Year in 2020!

In 2019 there were not too much happened technically with me, but, finally I had to abandone my model's  double fins with their strongly undercambered airfoil.
I can tell the story of "how and why", if interested. Maybe the conclusions can be useful to all of us...
Istvan

Agent 0077, Istvan!

Welcome! And where have you been?

You haven't missed a thing.  LL~

By all means, load the Forum up with interesting stories. Bring us up to date.

Charles

007

Trump Derangement Syndrome. TDS. 
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Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline John Hammonds

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #63 on: January 01, 2020, 07:47:54 AM »
Hi All,
Happy 2020 to everyone.

No intention to hijack this thread but I was digging through some old USB drives over Christmas looking for something completely unrelated but came across an old article by a local club member (Sadly no longer with us). :(

I remember Bill used a lot of Blue foam in his wings and also other parts. The construction was mixture of Blue foam and Balsa in a conventional rib style. I doubt the effort was less than a conventional balsa build but I do remember his wings were always light, straight and very stiff.

Anyway, Just thought the article might be of interest. It's too big to attach so I've uploaded it to Google drive. Hopefully the link will work.

https://drive.google.com/file/d/1cJ4XYb978E2BBThxA0K6U9odSIM4T1pH/view?usp=sharing

TTFN
John.
I started out with nothing and still have most of it left.....
Fast, Cheap, Reliable - Choose any 2!
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Offline phil c

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #64 on: January 03, 2020, 05:18:56 PM »
Dear Friends,
I wish you Happy New Year in 2020!

In 2019 there were not too much happened technically with me, but, finally I had to abandone my model's  double fins with their strongly undercambered airfoil.
I can tell the story of "how and why", if interested. Maybe the conclusions can be useful to all of us...
Istvan

Very nice work Istvan.  I don't know if you know this, but the blue foam technique first appeared in the 1960's, when Dupont started making the blue foam.  RC'ers first used it for wings, fuselages, often with fiberglass surfacing.  They discovered that 1/16in. thin balsa over blue foam is quite heavy, even for an RC model.  More recently a number of scale modelers have used similar techniques to make fuselages, especially.

Congrats on getting to the World Champs with it.  But it's nice to be  able to build new planes with new technology.

Phil C
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Online Dennis Toth

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #65 on: January 05, 2020, 07:04:05 AM »
Istvan,
Happy New Year to you. Hope the 2020 is a great year.

Looking at your model it is very nice job. I was wondering about the blue foam and how it compares to balsa. What is the density -lbs/ft3? Also what is the strength compared to 5 lbs/ft3 balsa. For example if you had a sheet of 1/8 balsa (5 lbs/ft3) how thick would a similar sheet of blue foam would you need to have similar say bend strength? Let say you took a sheet of the 1/8 x 3"x36" and clamped it at one end and put a one oz weight on the other end and did the same for the blue foam except added thickness to the blue foam to get the same deflection, how thick would the blue foam piece need to be?

Best,   DennisT

Online Brent Williams

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #66 on: January 05, 2020, 03:23:58 PM »
The 15PSI foams such as Owens-Corning Foamular 150 (pink) and its Dow (blue) ilk are about 1.3 Lb./Cu.Ft.

The 25PSI foams, Foamular 250 and Dow equivalent are 1.5 Lb./Cu.Ft.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #67 on: January 05, 2020, 06:25:20 PM »
Dear Dennis,
I have sometimes difficulties with the imperial measures, but I have found one very comfortable coincidence: speaking the density in ozs/cu.ft makes RIGHT THE SAME figure, as we speak in grams/liter.
So the middle density (ROOFMATE SL-E) named bluefoam is 34 ozs/cu.ft, right 1/3 of a very good, light balsa. (That's round 100-110 ozs/cu.ft. ), or 1/4 of a middle density balsa.
So I can substitute an usual, 1/16" sheet thin balsa plate by 2/9" thick foam. Or the other,  3/32" one, by 1/3" thick foam. This is -in the wing, e.g.-  is self-containing, does not need ribs. 
Covering is needed anyway, by me it is light glass mostly, with minimum, thinned epoxy.
Thick walls let use so-called "sculpturing" technique, not "build-up" technique. Some says it to be "primitive", some says "elegant" :) I'd like to consider to be elegant. One thing is sure: our thinking needs some "re-programming" anyway :)

Tomorrow I collect my story with that double well undercambered airfoiled fins. It won't be too short...
Istvan
 

« Last Edit: December 31, 2021, 05:05:31 PM by Istvan Travnik »

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #68 on: January 06, 2020, 07:30:12 PM »
Dear Friends,
Here is the story of double fins, from the first idea, up till the cutting them off 7 years later.
Original airfoil and outfit looked so:
https://www.flickr.com/photos/171504164@N04/48094363741/

https://www.flickr.com/photos/171504164@N04/48094466242/

https://www.flickr.com/photos/171504164@N04/48094399613/

As a "wooden handed" pilot, I always tried to plan and build more and more comfortable charactered models.
It was so thrilling for me the big acceleration and speed at the end of vertical diving, (mostly in strong wind) and I wanted to build some aerodynamical braking equipment.  (That time my engines ran perfectly, already).
I remembered, the strongly undercambered airfoils produce significantly big drag, in negative AoA  situation, and that the first 30% of chord is more important, than rear 70%.
At conventional arrangement (single finned model) practically the rear 50% is available, the "front part of chord" is the fuselage itself.
Using double fins at the tips of horizontal stab, there is no "shadowing" by the fuselage, I could exploite this effect fully: by upwind (positive AoA of vertical stabs) -> small drag; by downwind (negative AoA ) -> strongly increased drag.
I can say that my model suffered minimally of acceleration at the end of diving, beginning  the first corner of square loop, etc. It was really very comfortable.
But...
In some critical positions (e.g. beginning the triangular loop, etc.) the model sometimes left the stability, and made some strange movements, around the longitudional axle. Nobody wants to read the letters and figures at the wing, during pattern flight!
I never could find out why this happened.
I try to diminished the vertical stabs in two steps: a little bit getting better, but not perfect.
Maybe the fins had to be adjustable, or simply changed to other (e.g. plain-convex) airfoiled, I had not more patience, and last summer I cut them, and changed to a simple single plain-convex airfoiled vertical stab.
The plane flies not so comfortably now, but the behaviour became normal...
Should I make far more practicing flights?

Istvan.


« Last Edit: January 07, 2020, 02:42:49 PM by Istvan Travnik »

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #69 on: January 01, 2021, 12:42:56 PM »
Dear Friends,
I wish you Happy New Year in 2021!
... without Covid at least in the competition season, and as many flights and contests, as we can do!
Istvan

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #70 on: December 31, 2021, 04:42:42 PM »
Dear Friends,
Now we are in 2022 in Mid-Europe,
so I am wishing all of you Covid-free Happy new year to 2022.
This photo made at an emblematic site, where World Championships were organized in 1960 and 1964.
We lost it in 1993, and re-conquered and rehabilited in 2021.
B. U. É. K.  = Wishing Happy New Year!
« Last Edit: December 31, 2021, 05:00:05 PM by Istvan Travnik »

Offline Avaiojet

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #71 on: December 31, 2021, 05:33:47 PM »
Istvan,

Thank you for that.

Happy New Year back to you!!

Please stay safe and well.

Charles
Trump Derangement Syndrome. TDS. 
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Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline Mark wood

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #72 on: December 31, 2021, 06:06:48 PM »
Dear Friends,
Now we are in 2022 in Mid-Europe,
so I am wishing all of you Covid-free Happy new year to 2022.
This photo made at an emblematic site, where World Championships were organized in 1960 and 1964.
We lost it in 1993, and re-conquered and rehabilited in 2021.
B. U. É. K.  = Wishing Happy New Year!

Happy New Year Istvan. Here's a good flying year in 2022.
Life is good AMA 1488
Why do we fly? We are practicing, you might say, what it means to be alive...  -Richard Bach
“Physics is like sex: sure, it may give some practical results, but that’s not why we do it.” – Richard P. Feynman

Offline Dave Hull

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #73 on: January 01, 2022, 12:24:28 AM »
Budaors Model Field Control Line Circle

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #74 on: January 01, 2022, 08:58:01 AM »
Dear Dave,
Thank you very much for inserting the Google maps space photo on Budaörs / Budapest airfield, and in the corner several modelling circles.
I can tell you the brief story, if interested.
The grass airfield was considered to be relatively modern, in 1937, and the main building is under monument protection, as a noticed exemplar of "Bauhaus Style". Thanks this, it is still working, as the biggest sporting airfield of Hungary.
For upcoming World Championships, to 1960 they built one speed / teamracing circle, one for aerobatics, and later a concrete circle for tethered cars. All with standard fences, which were demolited after 1993, when we were banned out from there. (Ministry of Defense got all the airfield, buildings, hangars, great workshops, everything.)
After several years, they realized, they cannot do anything without concrete runways, and the Russians left more-than-enough military airfields in Hungary, when they returned home.
Sporting fliers got back the airfield. (Paying nice moneys, for everything...)
So in spring of 2021. we allowed to hire our aerobatic ring, and started a lot of working to rehabilitation. There is still a small house, with electricity, and place to store our models, fuel, basic garden tools, etc.
Long and winding story, but we enjoy a happy ending now...
Istvan

Offline Dave Hull

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #75 on: January 02, 2022, 03:07:05 AM »
Sounds like a success story to me, Istvan.  Maybe some difficulties along the way, but having a field with some nice facilities is a great situation to be in!

Personally, I'd love to see a picture of the bauhaus style building. Especially since it is representative enough to rate as a historical building.

Thanks for sharing the background on this historic flying field!

Dave

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #76 on: January 02, 2022, 01:56:47 PM »
Dear Dave,
Here is an article, with a rich gallery, made at 2017, when Budaörs Airport celebrated its 80th birthday. Do not care the text in Hungarian, the pictures speak for theirself.

https://index.hu/tech/2017/06/21/nyolcvan_eve_van_hazanknak_nemzetkozi_reptere/

The "Bauhaus style" born in 1920 and '30s years, in Germany, and when Nazis got in power, very soon disappeared from Germany, and main leaders emigrated, (most of them to the States, with many Hungarians amongst them).
Funny, but it's true, russian Stalinists hated this style too.
Istvan

Offline Dave Hull

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #77 on: January 02, 2022, 11:16:57 PM »
Istvan,

Thank you. There was a pretty good language translator for the article, and it was worth reading.

A few interesting points:

--I now begin to understand the Bauhaus style which you were talking about. Extreme functionality, and minimal decorations that do not contribute functionality. The pictures tell this story

--A picture of a nice stunt plane from 1967. Reminiscent of a Cobra nose and cowl, a Palmer wing, a.... and rigged to fly clockwise.

--What made it an Liszunov LI-2 instead of a DC-3? A license built copy? Different engines?

--I've never seen a parachute packed on the ground. Always on a long table. Often outside. Presumably so the rigger can slide it around easily and fold it. Kind of like at the laundromat

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #78 on: January 03, 2022, 05:02:40 AM »
Hallo Dave,
Yes, Bauhaus was modern, functional, but -in my taste- not ugly.
The picture of 1967 model of Mr. Tibor Vellai is unfortunately reversed by right-left sides. I noticed it that to the giant gallery "Fortepan", hope they turn it into the right position.
There is another, famous, very nice "I-beam" design of Tibor, named "VUM-18". I found it somewhere here, in Stunthanger, too. A masterpiece for exclusively well-skilled builders. 
Yes, Lisunov Li-2 "Camel" was the licenced copy of C-47 (DC-3 "Dakota").  This restored, working exemplar, named "Theodore Kármán" is the very only working piece all over the world. In nice weather serves 30 minutes sightseeing tours over Budapest, at weekends.
« Last Edit: January 04, 2022, 02:51:45 PM by Istvan Travnik »

Offline Dave Hull

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #79 on: January 03, 2022, 09:05:49 PM »
Istvan,

Thanks for the additional info, especially about the nice looking stunt model. I wondered about the picture being flipped, but couldn't see the lettering well enough to know.

No doubt, the namesake of the Li-2 was Doctor von Karman of Budapest?  I also noticed a modern Robinson helicopter in the pictures as well as the Li-2. The coincidence here is that I live about halfway between the two locations where the DC-3 and the R-22 were designed built. Both less than 15 miles away....

Whenever I see a picture of the Antonov An-2 it reminds me of the Joe Wagner Dakota of free flight fame. So much dihedral in a biplane is really unusual.

Stay warm,

Dave

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #80 on: January 04, 2022, 04:38:13 PM »
Hallo, Dave,
I am afraid of that our friends are bored on reading too much history here, and for their sake I attach here that sophisticated "VUM-18" plane from Mr. Vellai.
Well, that LI-2 plane named after professor Theodore Kármán (Tódor in Hungarian), who was deeply involved in the DC-3 project, however he was a theoretic professor of aerodynamics. He was Hungarian (with Jewish roots) emigrant to the States, just like Eugene Wigner, Leo Szilárd (atomic bomb, Manhattan project), Edward Teller (Hydrogene bomb) and John von Neumann (basements for programmable computers).
It is interesting, not their graduation universities, but their highschools were so inspirating in Budapest, in the '30s.
Istvan

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #81 on: January 01, 2023, 06:55:14 PM »
Dear Friends,
Wishing you (and for all of us, in Mid-Europe), happy and peaceful New Year in 2023!
Istvan
« Last Edit: January 02, 2023, 05:52:05 PM by Istvan Travnik »

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #82 on: January 02, 2023, 02:14:57 AM »
Peace and happiness to you also, Istvan--And a better new year for all of us.

Dave

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HI Istvan, I have been considering building a model using blue foam, similar to yours.

I have a question about hinging, how are hinging your model now?
Greg Kowalski
AUS 36694

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Quote
Well, that LI-2 plane named after professor Theodore Kármán (Tódor in Hungarian), who was deeply involved in the DC-3 project, however he was a theoretic professor of aerodynamics. He was Hungarian (with Jewish roots) emigrant to the States, just like Eugene Wigner, Leo Szilárd (atomic bomb, Manhattan project), Edward Teller (Hydrogene bomb) and John von Neumann (basements for programmable computers).

I think eveyone would be a lot happier if theyed just stuck to model aeroplanes .  S?P

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Dear Air Ministry,
I am not a professional in history science.
I can only say that about physics professors "exported" to the States, Mr. Leo Szilárd was not one of starters of Manhattan Project, but he (together with others, e.g. Mr. Albert Einstein) wrote and undersigned a letter to Mr. F. D. Roosewelt, not to use the atomic bomb in the ww. II.
I never will be able to judge, the two bombs finished sooner the war, saving millions' lives of Americans and Japoneses (at the price of several hundreds of thousands of japonese civilians), or not.
Let us stuck ourselves by aeromodelling... :)
Istvan

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Dear Greg (Curare),
The hinging of this bluefoam model is a little bit long and winding story - sorry...
Previous model, (made in 2000.) got homemade hinges: one half is normal, plain, nylon half-hinge, the other side is a piece of 1mm thick plywood, with a 1 mm steel wire glued in, in   " [ " shape. (the root of flaps and elevators are more than 10 mm thick, so I felt to keep the geometrical axle inside ).
Present model has got "worm"* shaped hinges, since I was lazy, and I believed opinion of my dear comrades: "will those be good enough for you."  The "drilling" the holes was simple: a very slim soldering iron, at proper, melting temperature for the bluefoam. (Many case melting a hole/bore, or slot is far better in bluefoam, than drilling, since the melted part remains inside, and reinforces the material. )
Well, the "dry side" (inner halfwing) hinges worn out more than a millimeter after some years: the hinge's material was glassfibre filled nylon, the pin was soft aluminum. Typical pair for abrasion!! Silly me.
I had to change all the 10 hinges, it was a shameful torture, really. 
New "worm hinges" are so simple: a piece ("tongue") of 2 mm thick textile bakelite + big RC clevis (for 3mm dia Bowden).
Works super!!
Istvan 

*I do not know brandname of this good-for-nothing crap product.
« Last Edit: July 13, 2023, 09:18:37 AM by Istvan Travnik »

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #87 on: December 18, 2023, 05:14:30 PM »
Some nostalgia:
The predecessor (built in 2000) has flown this September, at a show: (Sporting day for Budapest's  mayor's administrators, co-workers)
Who have flown in a nice round, kept by eight beautiful pom-pom girls? :)
« Last Edit: January 23, 2024, 06:37:53 PM by Istvan Travnik »

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #88 on: December 18, 2023, 07:42:07 PM »
Nice to see the history.  Did the construction method evolve much from the earlier model to the twin tail version?
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Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #89 on: December 19, 2023, 10:06:57 AM »
Nice to see the history.  Did the construction method evolve much from the earlier model to the twin tail version?
Looking to the construction method itself, there is not too much evolution.
Many minor changes used; some of them approved, some will be abandoned. In details:
2000 year model was esthetically inspired by Yak-9 fighter, the 2012 year model was inspired by Swiss Air Force C-3603-1, and the wing of Caudron-Renault CR-714.
The 2000 model's central wing & fuselage part was integrated (made of one piece of foam: the two half-sections contained a big, 1,5mm thick plywood rib, what is holding the mount of the bellcrank.) It was too much "sculpturing" work to make.
The 2012 model has a conventional "plug thru" wing (see the photoalbum), built more simple, and the plywood template set can be used again.
The 2000 model's complete nose mounted to rear parts like a torpedo-junction (6 pcs of M3 metric bolts, in 20° sloped position, and the primitive " A " shaped 3 mm dia musicwire landing gear holt  by the double plywood full ribs. (I have 2: one shorter for asphalt, one longer, with larger dia wheels for lawn. )
The 2012 model has wing-mounted landing gear (see pictures in album). The plywood "pockets" worked well for round ten years.
 I will keep this arrangement in the future, the reason is simply that in the '60s, in my childhood, the "Big Boys" used that, and the fuselage mounted "trestle" shape  considered naff.
As a "wooden handed" pilot, I use exponential control mechanism, since 1987.
In 2000 model the expo-crank is integrated into the bellcrank, and works well, but practically not adjustable. (Just the pushrod's length is adjustable, thru a small hole, below the horizontal stab. )
The 2012 model has far freely adjustable, both by opening the canopy, and by the (short) fuselage's  end. (Some say it is 'not elegant', but, when Wilga, or Foka Standard satisfied this, me too... :)
One is certain: my next model will enjoy all-parameters-adjustable control system: I have no time in this life to try/taste all my inventions... :)
Sorry for Lev Tolstoy -long answer
Istvan
PS. one good news: I found two proper epoxies for work, in small outfit, which ones can substitute the too professional LY-5052...
 

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #90 on: December 19, 2023, 10:09:04 AM »
What epoxy will you employ on your new plane?
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Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #91 on: December 19, 2023, 10:16:55 AM »
What epoxy will you employ on your new plane?
Give me one hour, I do not kow it's name/code by heart, but I plan to go down to my workshop, and I will notice/write you.
Istvan

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #93 on: December 19, 2023, 01:14:17 PM »
I believe that is MGS L385.  Nice product.
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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #94 on: December 19, 2023, 02:53:25 PM »
I believe that is MGS L385.  Nice product.
Looks to be the same.
As I learned in European pages (Spanish, German and British), there was some hystery about the first type of hardener, and some countries literally BANNED to sell it to non-professional consumers...
Well, in good ancient times I have had simple action about the LY-5052 : that time still lived between us some really great faces, who made professionally a lot of very big RC sailplanes and top racing boats. They bought the 2x25 kg resin plus the 19kg hardener, collectively. All I needed to call+pay for half a kilogram resin.
All they are building their models in Heaven now.
What a drag it is gettin' old...

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #95 on: December 19, 2023, 03:00:40 PM »
One is certain: my next model will enjoy all-parameters-adjustable control system.
I am building what will probably be the 4th version of my last PA right now and I am trying to make everything adjustable, including the logarithmic flap horn.  Where I am running into trouble is making things both adjustable and accessible.  Any pictures you could share of what you are doing would be nice.  I have a severe case of 'tinkering disease" and I do think it is incurable.  :X LL~
AMA 15382
If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #96 on: December 19, 2023, 04:55:18 PM »
I am building what will probably be the 4th version of my last PA right now and I am trying to make everything adjustable, including the logarithmic flap horn.  Where I am running into trouble is making things both adjustable and accessible.  Any pictures you could share of what you are doing would be nice.  I have a severe case of 'tinkering disease" and I do think it is incurable.  :X LL~
Dear Ken,
All details still in my mind, not on the paper, or on the building bench. (The best solutions I got laying on the massage bench (traditional Swedish healthcare massage, near in alpha-state mentally))
So pictures will be published in the spring, but a schematic will be drawn after Christmas.
For the sake of accessibility, the expo-crank won't be integrated into the bellcrank.
The stations will be as follows:
[conventional bellcrank] - [adjustable short pushrod] - [vertical lever (one-arm lever with one input and several output holes, axle beneath the top of canopy) ] - [ double, adjustable very short pushrods] - [ double, adjustable flaphorn arms] This means that flaps travels can be independently adjustable from  0° to 45° plus-minus. Flap movements are approximately linear. 
The elevator control system starts from bottom end of [vertical arm] - [medium long, adjustable pushrod] -
 [long arm of expo mechanism, what drives the ] - [expo crank with multiple output holes] - [ long, adjustable pushrod ] - [ elevator arm with multiple holes, aft to the "short and ugly" fuselage] .
Every junctions are accessible and visible thru the canopy or outside the fuselage Every pushrods are precisely horizontal, eliminating geometrical distortions. The only new element for me the "vertical arm", it helps to modify the flaps' travel, and puts the "driver" pushrod of expo mechanism beneath the wing.
All junctions are steel (2,6 mm spoke) and plastic (ZX-100) pairs. Slippery even when dry, wearing- and vibration resistant.
   

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #97 on: December 19, 2023, 09:09:27 PM »
Dear Ken,
All details
So pictures will be published in the spring, but a schematic will be drawn after Christmas.
I hope you post some here.  I have never seen an exponential system up close but I have heard good things about them.  What I am building on is a split horn logarithmic system that has a logistical problem.  It reverses the movement of the elevator pushrod forcing the horn to be on top of the elevator.  I have considered putting a third crank just behind the box to reverse the direction of the pushrod allowing it to be on the bottom of the stab.  This was at the request of my pilot figure who does not like the pushrod running between his legs, and it would give me horizontal alignment.  I would be able to make all of the flap/elevator ratio adjustments at the front and eliminate the need for a rear hatch.  My designs are all electric and I make the bottom of the plane removable to just after the flaps.  Everything is accessible including the bellcrank.

What you don't see in the picture is the bellcrank.  I use a thick printed 4 1/2" diamond shaped bellcrank that allows me to tap mounting holes for the pushrods and mount them both on the bottom.   The diamond shape is because I need to drive the canard from the side opposite of the flaps.  The bolts do not loosen in the printed bellcrank and can be moved through the hatch. Too many pushrods, too little space and putting them on opposite sides defeats my 100% accessibility rule.

So, that is where I am.  What is so much fun is that none of this is anything but play time.  If I had my sights on a high-level championship my plane would so simple a cave man could fly it.

Ken
AMA 15382
If it is not broke you are not trying hard enough.
USAF 1968-1974 TAC

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #98 on: December 20, 2023, 11:53:54 AM »
Istvan, do you plan to heat cure the MGS 385/386 epoxy?  Looking at the specs for that resin system, it looks like heat cure is necessary for optimal results.

Quote
Curing time: 24 hours at 20 °C + heat curing 10–15 h at 50–80 °C (at least 40 °C is necessary to get out of the brittle phase)

Hardener 386 should be heat cured in every case.
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Offline Istvan Travnik

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Re: The bluefoam model, or how to build a stunt plane without a bit of balsa?
« Reply #99 on: December 20, 2023, 01:00:34 PM »
Istvan, do you plan to heat cure the MGS 385/386 epoxy?  Looking at the specs for that resin system, it looks like heat cure is necessary for optimal results.
No, it is absolutely excluded by two reasons:
-the dimensions of the model ( my wife killed me, if I tried to buy/build such a big autoclave/oven to heat)
-the model itself made of Styrofoam (or some other brand of extruded Polystyrene), and this material does not like 100 centigrades, or above. First experiments resulted this resin to be satisfactionally hard and strong in very thin coat, and normal humidity. (My workshop has tempered all year long between 22-24 centigrades. I keep the humidity below 60%. )


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