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Building Tips and technical articles. => Building techniques => Topic started by: Istvan Travnik on October 27, 2012, 05:06:03 PM
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Dear Friends,
Succesfully I found a new place for my photos.
Please, visit my album here:
https://www.flickr.com/photos/171504164@N04/page1
Only bluefoam (Roofmate), some plywood, glass, carbon and epoxy. No balsa.
No lyrics, but questions are welcome.
Regards: Istvan (Europe, Hungary) :!
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Video??
Marcus
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I looked at all the pictures, and found some very interesting details that could be easily adapted to more conventional models. I can't say I'm enamoured by blue foam construction, but somebody with balsa allergies might do well to consider it. H^^ Steve
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Hi Istvan,
That is a clever and well done airplane and photo presentation.
Questions:
what are the specifications ? - wing area , wing span, tail area and span, fuselage length and etc.
component weights - wing weight , fuselage weight, tail weight , hardware weight , total weight.
How does weight compare to a built up wing or white foam balsa sheeted wing.
How does your fuselage weight compare to a molded or standard balsa fuselage.
How does your tail components weigh compared to built-up or solid balsa
components.
Finishing Method - It is unclear what method you used to finish this plane. Did you use epoxy finishing resin , with or without lightweight fiberglass as a substrate for your finish? Blue foam can dent fairly easily so a hard substrate would seem to be useful. What kind of primer and paint did you use?
My questions are to give us all a frame of reference to evaluate how your clever ideas might apply to other people's building plans.
Finally, What were your reasons or objectives or rationale for adopting this method of construction?
Once again, This is a great photo presentation. Well Done!!
Pat Robinson
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Istvan, I have been building with white one pound foam for forty years. In the last few I have not used any balsa. I developed and published the methods in 1974 when I was doing FF. I have a table saw that lets me cut poplar to any size needed. Being careful to balance size with strength I come close to balsa construction at a fraction of the price. I use commonly available birch ply, .220" thickness for doublers, sometimes fuse sides, bell cranks and control horns. I find the white foam to be of sufficient strength once it is encapsulated with spars and the normal silk span covering. Silk span is applied with 50/50 white glue. It is then sealed using a hot mix of unflavored gelatin. Once sealed any paint or dope can be used. I do not sheet foam wings or foam stabs. A note here is that with my income being Social Security I must build cheap. An 800 + sq in area CL biplane only cost me less than $30.00 to completely build and finish. No mine are not front row planes but they will fly with similar designs.
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I hit the wrong key to post the plane with the above post.
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I'll try this again.
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<SNIP>
Finishing Method - It is unclear what method you used to finish this plane. Did you use epoxy finishing resin , with or without lightweight fiberglass as a substrate for your finish?
Finally, What were your reasons or objectives or raionale for adopting this method of construction?
Once again, This is a great photo presentation. Well Done!!
Pat Robinson
My questions also... Outstanding work!
I can take a guess in regards to the second question- Probably tired of the 60 yr. old construction methods on this forum. Z@@ZZZ
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Its very cool and my guess as to why is availability of balsa there.
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Dear Friends,
I try to answer in logical order:
Why this method?
Very simple: in the early '80s my conventional balsa built-up models suffered from strong resonance. I tried to detune them from the engine's useful RPM interval, but no success. Finally the long pushrod broke, killing the plane & engine.
That time the white foam+balsa (or Obechi, etc.) planking method was known already, but in lack of vacuum-technology, and self-expanding, light polyurethane glues, I did not consider to be reliable and light enough. (And technically "elegant", as well :)
So I developed my method on extruded Polystyrene foam. As I observed under microscope, the blue has approx. half a big elementary bubbles, than the pink brand. All other parameters are similar. (Material, density, strength).
I find good finishing/laminating epoxy resin (nowadays is Huntsman (CIBA) LY 5052 type), and the steps are as follows:
1. Making the foam by usual methods: hot wire (not too hot, to avoid grooves), sanding by sand-canvas (120 or 150 grade), and/or trimming by balsa-plane, using razor-blade (!!).
2. Stabilize the surface by resin: I thin the epoxy resin by methanol, adding 20-30%, plus some talc, to better sanding ability. And "paint" the surface by this mixture. Do not worry: a GOOD resin will be hardened for tomorrow, anyway...
3. Sand the surface by sandpaper, grade 280. Even by wet method: the Polystyrene foam is NOT sensitive of water: how a big advantage over any wood!
4. Cover the surfaces by light glass (25-28 grams/sqm), or carbon tissue (9 grams/sqm), or light unidirectional carbon (where extreme strength is needed: in the central part of wing, horizontal stab.) The resin can be the same, as in point #2.
Inside parts (e.g. spar, etc.) must not impregnated by thinned epoxy.
5. Sand again, as written in #3. The surface is ready to paint. (I use to order nitro-based colors from auto-paint shop, covered by two-component acrylic hard lacquer.
Tomorrow I collect the measures and weights.
Regards: Istvan
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I tried the blue Styrofoam (genuine Dow from Midland Michigan) when I was building combat planes.
Genuine Dow is basically twice as heavy as generic white polystryene (which is often incorrectly called Styrofoam).
Dow is much stronger than white foam.
Some weight can be recovered with thinner sections.
Dow requires a lot more energy to cut.
Myh finished model went to 18 ounces vs 16 for white foam.
You have some very nice tools.
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I tried this years ago, when Hobby Poxy was the only "good" epoxy available. The main problem I had was that a layer of light glass and epoxy is as heavy as 1/16 in. balsa. I had problems with dings on the surface. any kind of thing that fell on it would shatter the finish.
I can get much the same effect using the white beadboard. Hollowed out sections need a little thicker walls, but still are lighter. Double covering with one of the light weight plastic films(including the SLC covering I have) weighs about the same as glass/epoxy and is very ding resistant. One coat of autobody primer(spray can or spray gun), sand most of it off, leaving a very mottled surface. Then go to whatever final finish you want.
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Dear Friends,
The static basement of bluefoam is very simple: (excuse me for using metric measures):
a light, good balsa makes approx. 110 grams per liter, while the middle density (e.g. ROOFMATE SL-E type) bluefoam makes 34 grams per liter. It means that a 2 millimeter thick balsa equals 6 (six) millimeter thick foam. There is no doubt, the balsa construction needs ribs, while foam construction does not. As you remember, the stiffness of some shell structure is commensurable to it's thickness up to cube...
Balsa's behaviour is similar to a sponge (since structurally it is some kind of "branch of tubes" since bluefoam is a mass of closed bubbles, no sponge. Paper or silk cover on balsa (well filled and prepared to paint) is not lighter than a light, glassfibre fabric with epoxy, but far less strong.
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I Like it! Very cool.
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Thats cool!!
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Wishing Happy New Year to every kind colleagues & visitors in 2013!
Istvan
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Truly amazing, fine work sir. Happy New year Ken
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The Wart Hog was my favorite airplane from the cold war. I was a young American soldier that called in air strikes and artillery in the 1980'. My father built a version of a previous stunt design we did together. I was surprised he did that because he never really liked twin rudder designs when I was a child. He was however, checked out in the Air Coupe in the 1950's. If you have been a PAMPA member since 1999 you may have seen his twin rudder Chevelle. We published a single rudder designed based on Fancher/ Rabe numbers in Flying Models in 1998. Very nice work my friend. Your pictures and workmanship are superb!
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Dear Friends,
Some added info's abut usability and repairability of this technology. This August, in Poland, was organized a training competition, named "Kujawia Cup", right before the World Championships. In the strong wind, by first corner of first inverted loop in the first flight, the model touched the ground: the complete split tail rolled after the slipping plane on the grass...
... and in the evening, right before midnight the model was reborn: some 5 minutes Epoxy to put together the foam parts plus glassfibered tape on the surface was enough, to fly again. So I did not lost the participation on the WCh's.
See photos from Claudia Kehnen's super album:
https://www.flickr.com/photos/fesselflug/14691155259/in/set-72157645923341020
https://www.flickr.com/photos/fesselflug/14875349204/in/set-72157645923341020
(Well, the WCh was organized so austerely, on rough grass for stunt)
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Istvan,
Nice, I like it. Outstanding modeling! We need more of this different kind of building.
There's this guy in Canada that builds that same way. Has been for years. He's on U-Tube. I've made graphics for him.
Only he builds large R/C models. I believe his TWA Constellation is 16' in span.
Keep up the good work.
Really nice model you have there!
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It was my pleasure to meet Istvan and see his plane in August. I showed pictures of it at the WC presentation at the Golden State contest last weekend. It also has an Expocrank mechanism, viewable through the canopy.
I think Istvan looks like a lightweight version of Bill Rich, a concept I had difficulty communicating with Istvan. Sorry, Istvan.
The second picture below shows the broken fuselage, which was easily repaired.
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Dear Friends,
Visit my album:
https://plus.google.com/photos/117790355930193335731/albums/5715088163776972593
Only bluefoam (Roofmate), some plywood, glass, carbon and epoxy. No balsa.
No lyrics, but questions are welcome.
Regards: Istvan (Europe, Hungary) :!
You do very nice work!
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Dear Howard,
Thank you very-very much for the photo of broken fuselage!
I would like to add some informations what we can see: the pushrod is carbon tube, bondaged at the end with some Kevlar string, fixed with Epoxy glue, and it has 5 mmm (1/5") thread in it, for the adjustability, with the broken part of the homemade pushrod fork. Its material is "ZX-100":the plastic, what practically never wears out. I used this material for the bellcrank and the arm of the exponential mechanism, too.
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Here is the lowdown on ZX-100: http://www.zedex.de/ZX-100_Family.344.0.html?&L=2 .
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I don't think anyone has mentioned the use of blue styrofoam for making molds for balsa skins. Certainly easier to shape than pine, which I used to use! I have styro molds for wing leading edge sheeting, fuselage balsa turtledecks, fuselage tops and bottoms.
Still use balsa for planes, though. Wood is easy to repair (when necessary).
Floyd
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I remember, when I broke wooden airplanes, in most cases there were some elements or fragments to be replaced, since the broken surface was "bony", crushed, not plain.
A bluefoam structure is more "grateful": it is enough to put together the parts, and cover the line of braking by thin glass.
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Dear Friends,
I wish you a Happy New year in 2015!
(and nice models, hundreds of perfect flights, best results...) H^^
Istvan
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Hello Istvan:
Great work!
What engine was in the airplane?
How did you get your cat's eyes to glow so brightly? What food does the cat eat?
Stay well,
Frank McCune
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How did you get your cat's eyes to glow so brightly? What food does the cat eat?
Nitro. Light's 'em right up.
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Dear Frank,
The engine is MOKI-M10 type, named in export terminology to MOKI-51.
Built still in 1987, and I have some 5-6 pieces. I used the first one from 2000 to 2009 (ten years, approx. 2000 flights).
Chromed steel sleeve, ringed plain piston, 3-channel Schnuerle scaveging, two-part housing.
And many-many modifications by me. (outlet 130° to 140°, bypass 115° to 110°, cooling fins off from cylinderhead, steel deflector in combustion chamber, and the conventional venturi + spraybar combo changed to HP-40 -type (one side nozzle and needle for self-cleaning).
Own designed tangential inlet silencer, soldered by Technoweld.
Weight, power and behaviour is very similar to the old ST-60, however a bit less vibration.
The photo with the cat was made with flashlight in a dark room, and he looked direct on me :)
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Dear Friends,
I wish you a Happy New year in 2016!
Some news happened with the model in 2015: I tried two types of very good quality Czech 3-blade props, designed for electric motors. The bigger, 12.3" dia, well undercambered type made for the stronger MVVS motor, and I had to run it between slow and maximum RPM, in two-stroke style.
The smaller one 11,5" dia. made for AXI motor, not undercambered, and I could run it in 4-2-4 style, comfortably.
Undoubtedly, I liked the bigger more, (maybe the engine did not...:):) )
Istvan
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Istvan,
I just noticed your number on the wing. 0077.
Interesting and a great number!
Charles
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Dear Charles,
You can call me "Agent 0077", similarly to Mr. James Bond, if you want to :)
However, I got this number absolute at random, from the Hungarian Association of Modellers, when FAI ordered to use standardized form of listing of models, country by country, in the early '90s.
I am glad with it, because in the old pre-christian mythology of Hungarians (take 1100 years, or more), the "7" figure bears specially lucky meaning...
Istvan
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Istvan, I hope you use those full carbon props, not those for electric ... those light could be danger if used on piston engine.
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Dear Igor,
That bigger, light, undercambered prop was the best - for the model and me, but not for the engine...
Since my engine is a ringed piston type, not ABC, I did not presumed it to be dangerous.
Attila Morotz has seen it, many times, wished it and tried it - and gave it back immediately, since that prop generated 30% more electric energy consumption, and some 20 centigrades higher temperature for his ESC...
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I am not surprised, yes that prop needs more power than those others, they are in use with large MVVS 8 motors.
However, that hub is not prepared to withstand periodical compression/expansion of single piston IC engine, so it is not good choice, be carefull.
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Dear Igor,
I think I shall ask Mr. Sandor Havran, to make me some copies of maple. I hope, the the shape, airfoil etc. is not copyrighted by nobody :)
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no, it is not copyrighted, but I am not sure if Sandor can make so thin blade, may be better solution will be full carbon version, it is heavier, but safer
or what about classic underchambered prop for IC engines? may you can find some props from guys converted to electric
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Good idea, Igor!
I will ask them, to bring that props to Hradec Králové, in this May...
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I sent some questions to Istvan regarding his use of carbon and fiberglass on this airplane. He requested that I post my questions and his responses so that others can learn from his alternative material use and building methods.
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Q: What weight of fiberglass cloth did you use for that?
A: The fibergalass is very light: around 23 grams / sqm that means approx. 2/3 ounces / sq yd. It is essential that warp/weft is approx 2:1, so we can play with the strength, by proper positioning.
Q: Did you use the same variety of fiberglass on the flaps?
A: Yes, the wing body & flaps got the same cloth on. Only the centerwing front wears some 9 grams/sqm carbon tissue to reinforce, under the glass, where we take the wing by hand, and the landing gear needs it. The "spar" is double unidirectional carbon, covered by japanese paper by the phase of laminating. (uni. carbon has almost no weft and very easy to destroy it with the brush. Afterwards I sand the paper off.)
Q:Did you use fiberglass over or under the carbon fiber on the stabilizer/elevator?
A: Stabilizer got unidirectional carbon, with the same technology: it is extremely stiff and strong: the model has fallen 2 or 3 times onto concrete surface, onto back, and got no damage. Elevator covered only by glass.
Q: What type of glue or resin did you use with the fiberglass?
A: I used professional brand of aerospace industry: Huntsman (CIBA) LY 5052 resin and its hardener. It is very thin itself and and for the outside surfaces I thinned it by 20-30% Methanol. It was essential for the easy work and weight. I know, most of the epoxies won't get hardened properly in such a thin coat, or thinned by methanol. (maybe it is an effect of water vapour from the air)
Q: What types of glues and resins did you use throughout the entire build?
A: Glue for most tasks: simple 5-minute transparent epoxy. You can put together the sections of fuselage in hand.
Serious places: engine bed and section, bellcrank support, and fuselage pockets: 24 hours transparent epoxy and heatgun.
Q: What type of paint did you use on the plane?
A: I ordered the colors in Nitro from an autopaint shop, and for covering cote, some 2-component Acrylic lacquer.
Maybe I will return to Polyurethane -based paints, that is more durable, and resistant of Methanol.
(https://lh3.googleusercontent.com/osKYCI3FadxhxyNnufqPh-xkNVJ1Snd_cmrRH8jd6kQCFBvzA1GaWjKlyMbJMR1NoQ6hzynPww=w1440-h900-rw-no)
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Dear Friends,
First of all I wish you Happy New Year in 2017!
With new models and best results, without cracking.
:! I found a special sanding tool, which can be very-very useful, in this bluefoam-technology.
If we have no computerized hotwire cutting equipment, we need to use significantly low temperature hotwire, not to melt some grooves into the surface. A "cold" wire (I use standard .35mm dia FAI teamracing steel wires) needs significant longitudinal push and pull "sawing" movement for the good quality surface. This leaves many "hairy" residue on the surface. To sand it off needs very-very skillful hand, to avoid possible damage of the surface.
But, if yo use not some sanding canvas, but the good old Sandplate, it will easily "harvest" all the hairs.
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Here is some photo of original Swedish Sandplate: it is very thin, pliable steel plate, even for concave surfaces (e.g. at flaps)
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...and two more photos:
I am sure, this is available in the States still, maybe under other brandname and different vendor.
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Sometimes I've used white foam (2 lb density) to remove the hot wire hairs. It works ok. I sand all edges of my white foam block with a small bevel first.
I love the work you are doing with the foam!
Happy New Year,
Chris
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Dear Charles,
You can call me "Agent 0077", similarly to Mr. James Bond, if you want to :)
However, I got this number absolute at random, from the Hungarian Association of Modellers, when FAI ordered to use standardized form of listing of models, country by country, in the early '90s.
I am glad with it, because in the old pre-christian mythology of Hungarians (take 1100 years, or more), the "7" figure bears specially lucky meaning...
Istvan
Istvan,
Nice to see you back in the Forum.
Blue foam. What is the weight for one cubic foot?
I'm thinking of using pink foam for a project but not sure of the weight. I can find out.
Happy New year to you also.
007. ;) ;)
Charles
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Dear Charles,
The blue and the pink brand is chemically the same: extruded Polystyrene foam. Blue's brandname is Roofmate, Floormate, Styrofoam. Original producer is DOW Chemical, and it is licenced worldwide. (E. g. by us, Hungary, in Europe.)
Pink is from Corning Glass originally, and that is licenced woldwide,too. (e.g. In Austria, near us, and named Austrotherm.)
There are different density and different compression strength variations.
e.g., a middle, universal variant, Roofmate SL-E has 34 grams per litre density. (It takes right 34ozs / cu.ft)
The pink brand is the same, however I found approx half a big elementary bubbles under microscope, by blue brand. It can come from technology, the expanding gas, etc. Maybe the blue one takes up a little bit less resin, when we build up the surface.
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Dear Friends,
I wish you Happy New Year in 2018!
Somewhere I found some characteristic photos on this model, from previous years, see below.
Istvan.
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Dear Friends,
I wish you Happy New Year in 2018!
Somewhere I found some characteristic photos on this model, from previous years, see below.
Istvan.
Istvan!
Hey! Agent 0077.
Been a while.
You won't believe this. Just a while back I thought of you and your foam constructed models.
I designed this biplane pusher and gave great consideration to your foam technique.
I didn't have the courage to tackle it. Not just yet. Balsa and ply. Boring.
Bring the Forum up to date.
Any new models or Builds in the works?
Charles
007
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Dear Charles,
We are in 2018 now, in Europe. (it's round 03 a.m.)
You can find me under "Steve Grassfield" nickname at facebook. (I have bad feelings about that kind of media, but it was a must, so I did that).
2017 mostly spent with building works of a new grass circle for our club, and no serious model building works. However new mechanism and main lines of a new model are on paper. This year I shall meet and compete with your national trio in Landres, France, at WChs :)
I would like to encourage you and all comrades to start a nice friendship with blue/pink foam, with this "sculpture-like" technology; I think, when some Sandplate and good Epoxy got in hand, there won't be serious problem.
All questions will be answered here, if raise any.
Happy new year, again!
Istvan
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Dear Friends & Visitors,
I wish you Happy New Year in 2019!
Istvan
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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
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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/
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Congrats on the speed team win, Istvan!
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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!
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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
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It works on Windows 10, just an FYI.
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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!
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It works on Windows 10, just an FYI.
No luck with that other link.
My wife has Windows 10.
Charles
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Second link works on 10 also.
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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...
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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
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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
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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
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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.
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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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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
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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.
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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
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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.
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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
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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!
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Istvan,
Thank you for that.
Happy New Year back to you!!
Please stay safe and well.
Charles
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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.
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Budaors Model Field Control Line Circle
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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
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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
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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
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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
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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.
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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
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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
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Dear Friends,
Wishing you (and for all of us, in Mid-Europe), happy and peaceful New Year in 2023!
Istvan
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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?
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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.
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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? :)
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Nice to see the history. Did the construction method evolve much from the earlier model to the twin tail version?
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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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What epoxy will you employ on your new plane?
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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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What epoxy will you employ on your new plane?
I bought right this, from right here:
https://www.amazon.de/-/en/Hardener-Certificate-Aviation-Tested-110149-0/dp/B07Z9K2JL1
Istvan
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I believe that is MGS L385. Nice product.
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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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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~
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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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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
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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.
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.
https://www.r-g.de/en/art/110150
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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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Good to know the MGS resin is going to be effective for you. I picked up some excellent low viscosity, room temperature cure resins from Resin Services for various upcoming projects. I'm going to use either the HTR250 /106-3 or the WB400/386.
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Dear Ken,
Your mechanism ( regarding to a canard, as an extra ) is very impressively complex and professional.
It is very good example how many ways are given to solve similar tasks.
I prefer minimal amount of bolts, and do not trust factory made parts (balljoint, etc.).
The good old "hook-and-lever" , or "tongue-and-hook" type junction satisfy me. Locking: a "@" -formed 1 mm dia tiny musicwire, snapped into the hole, bored into the end of 2,6 mm steel (spoke) hook.
Looks primitive, but absolute safe and vibrationproof.
I dis-assembled one "tongue-and-hook" junction, look photos.
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Dear Friends,
Wishing you Peaceful and Happy New Year for all of you, to 2024!
Istvan H^^ https://stunthanger.com/smf/Smileys/classic/hatsoff.gif