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General control line discussion => Open Forum => Topic started by: Robert McHam on July 06, 2008, 11:49:48 AM
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I was just reminded of a plane I started to build but never finished.
The first diamond shape airfoil I tried was a corrugated cardboard control line model. I don't remember Which magazine it was in but it just about had to been Flying Models. I only built the wing and mounted the bell crank in it which worked rather well and was well supported. I had planned on using my K and B Stallion .35 in it. Never found out how it flew.
Seemed pretty heavy at first but it was pretty large and had lots of wing area besides the diamond airfoil shape. A number of times i would take the partially built wing out for a spin, holding it in my right hand and turning counter clockwise as though I were flying it. As much as I was impressed with the wing as it were I never did get the thing finished.
This was about the mid seventies I think. I could not say the name of the plane to save my life. Almost certainly it had a full fuse and not profile. Very possibly had the word cardboard in the name.
Not to be confused with the Cardboard Cutie By AAM for half A. A really good looking model that was.
Any discussion or comment appreciated. Pictures would be a real plus. I took none of mine.
Rober
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Phil Brown probably knows. He's built several cardboard models (nowadays, the newer plastic corrogated board is a lot lighter, and more suitable for our use).
Go here, and ask him ("Garf"):
http://hangarflying.proboards18.com/index.cgi?board=wire
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I built one with a half diamond airfoil (1/2A). On the first flight, it was upside down before I realised what happened. I want to build a cardboard diamond airfoil profile plane about 42" span for a 35 and see what happens.
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Chuck Felton has had quite a few cardboard models published in Model Aviation over the years: PT-19 (July 1995), P-51B (Sept 1989), Heinkel 100, Mar 1988), Ki-61 Hien (Sept 1986), FW-190 (Oct 1982), Douglas M-2 Mailplane (Oct 1977), and a "Swiss World War 2 Fighter" (March 1976). All of them are fairly large, .40-.50 size models. If memory serves correct, the Mailplane has a diamond shaped airfoil. The later warbirds and PT-19 have a more conventional flat-bottom airfoil (with a fairly sharp leading edge). I think he also had some designs published in Flying Models.
cheers,
Ken
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Thanks Ken but MA is one I personally never really read. Never bought an issue.
Mr Felton indeed published several in FM. I found none before nov of 1987. Seems they were all scale type planes whereas the plane I had started was a simple sport type of plane. I suppose I should have mentioned this in my first post.
While I am not familiar with Chuck Felton's work It must be quite good to have had as many of his designs published as he has. Again, It seems most are scale types which I don't fiddle with much personally.
I don't remember the actual span of the ship I started but I am guessing at least 42 inches in span and a chord of at least 10 inches but I feel like it was closer to 12. The ribs were of diamond shape and the structure was really quite sturdy.
I did build and fly a model published in AAM called the milk carton special anyone remember that one? Thinking back I would like to have that article and plan again!!!
It used new, unused quart size cardboard milk cartons. Two of them and a Baby Bee supplied the power.
Robert
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If I were to build a diamond airfoil plane, how thick would the wing need to be to be able to turn well? I used to fly the Demon in combat with a diamond airfoil. It flew pretty well.
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This information is from memory and may not be entirely accurate. Please correct me where I'm wrong. It is intended to jog others' memories.
I have never built nor flown a diamond airfoil but I've seen several published. Seems to me the Combat boys were trying it in the early seventies (I think).
I believe diamond airfoils flew a bit squirrely with the quick lift transitions...something you could take advantage of in combat at the time. I believe the main saving grace was the ease of building on a flat surface, without using jigs.
As to cardboard models...IMHO, balsa ALWAYS flys better. I think most of these were novelties and experiments. I don't remember ever reading of anyone building lots of cardboard models...'cept the Osborne Platter which, apparently, performs exceptionally well for its intended purpose. 8)
George
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Hi Guys,
back in the 80's I was between jobs with no money for my hobby but I needed a plane so I decided to try a cardboard plane. The first thing I did was to treat the cardboard with a water based polycrylic that is thinned to 60-80%
with water. This adds almost no weight but it helps to seal the cardboard against humidity which can reduce the strength of the wing and the treated cardboard is easier to cut cleanly. I used a heat gun to dry the cardboard and then placed a board with weights on it overnight to prevent the cardboard from curling.
Cardboard comes in different strength grades so use the lightest you can find.
Make a pattern of the wing skin using taped together poster paper and transfer
it to the cardboard and cut it out. Then you use a roller tool that is blunt and has a roller wheel about a 1/16" thick. I think I used a screen door a spline tool. starting a the center of the leading edge, use a straight edge and roll a crease on the back side of the cardboard.
repeat the crease in 1/4" increments till you reach the spar at the thickest point of the wing. Then,gently bend the cardboard on the leading edge section into a mostly smooth curve. The creases you rolled on the backside of the cardboard makes this possible. So no diamond airfoil is required.
My plane was around 625 sq" and I can't remember if I used 6 or 8 ribs per panel. Anyway, go to your plans and copy 6 or 8 equally spaced ribs for each panel and then, change the airfoil to be flat behind the thick point of the wing. Then, reduce the rib outline by the thickness of the cardboard wing skin. Glue copy of rib pattern to cardboard and cut out with the flutes running vertically.
The spar is cardboard with the flutes running vertically topped with a 1/4" sq. balsa sticks on the top and bottom and re-enforced with plywood an fiberglass in the center.
The ribs and spar are slotted "eggcrate style" so they just slip together and are the topped with with the 1/4" balsa. I cut lightening holes in the ribs just like a balsa rib. Brush a small amount of titebond (or etc.) glue onto the rib edges and let dry. This re-enforces the edges to give a firm bond of the rib to the wing skin.
To assemble: join ribs to spar and add the 1/4" strips top and bottom. Apply plywood joiner in the center and re-enforce with fiberglass. I then installed some recycled controls.
Shim the front of the wing skin to keep the wing warp free with the trailing held flat on the on the bench. glue the wing skins together on the flat rib section. Then CA glue the balsa trailing edge to the skin. Next, CA glue in the rib/spar assembly to the flat section making sure that the controls still move freely. I used A-grain 1/16" x 1" by 3+" scraps CA glued on the inside of one panels leading edge area. This helps keep both panels even as the panels are joined. I then CA glued the bottom of the leading edge section of each rib to the curved cardboard skin.Next, Glue down the top skin. Finally, glue an 1/8" balsa cap onto the trailing edge which seals off the raw cardboard edge. Then, cut a few round lightening holes in the wing between the ribs and you are done building.
I used Monokote to finish the wing which was the most expensive item on the plane. I bought the roll for about 9 bucks so I guess I had a total cost of about 5 bucks for the wing. The flaps and tail were built up from my scrap balsa pile and monokoted. The price of "moneytcote" has gone up sine back then.
For the fuselage,I prebuilt the entire motor crutch assembly including slide in tank compartment with all formers and plywood doublers. fuel proofed and painted. Cut the fuselage sides with the flutes running vertically. Line the inside edges on each cardboard side with 3/16" sq. balsa longerons except of course where the crutch assembly glues in. Glue the sides to the crutch assembly and clamp the join the tail with a balsa tailpost just like a balsa fuselage. Add cross pieces of 3/16" sq balsa sticks to the top and bottom of the fuselage.
Cut the top and bottom cardboard pieces. Glue paper to cover the flutes on each side of the top and bottom and let dry.Glue on the cardboard top and bottom to make a simple square box assembly. Then re-enforce each corner with epoxy and fiberglass tape. I used a leftover spraycan of white primer to paint the fuselage and rudder and a leftover spraycan of white epoxy refrigerator paint for a fuelproof coat.
So, I ended up with a full size stunt plane for under $10.00. I used a strong .40 engine I already owned to power it. The plane did the whole pattern and I probably put 800+ flights on it over 4-5 years. I smacked it hard enough a couple of times that it would have shattered balsa plane but the cardboard plane just dented. Yes, that plane was square and butt-ugly and built out of a scrapbox, but it gave me many hours of pleasure and kept me flying when money was short.
PS.A cardboard plane would make an ideal trainer. it's cheap and durable.
Guys, I'm sorry to run long but I just had not thought about that plane for a long time and it brought memories.
Pat Robinson
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Pat, I have often thought of a corrogated paper plane myself, but, have always been put down that it would be too heavy. You don't say how much your plane weighed, but, it must not have been too heavy if it did the full pattern. Later, DOC Holliday
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Hi Doc,
Sorry for my oversight on posting the weight. it was standard swept leading edge planform wing of 625 sq." and I believe it weighed 55 oz with a 9.2 oz K&B 40, 1 oz. muffler, aluminum fuselage landing gear & wheels weighing in about 3 oz. and a 5 oz. homemade tank that was about 1.5 oz. for a hardware total of 14.7 oz. So the airframe weight was 40.3 oz. including the controls.
I would like to repeat my advice that corrogated cardboard come in different grades of strength which directly determines it's weight. A label on the bottom flap of most boxes tells you it's rating. Hey, the stuff is free so you can afford to be as picky about cardboard as you would about the balsa that you buy. It just takes a little more time searching to find the "good stuff".
The lighter grades held up just fine on my plane so I don't see a need for heavier board. Most of the lighter cardboard that has a nominal thickness of 1/8" but much of the heavier rated cardboard is somtimes thicker than an 1/8"but checking out the box label is the only way to be sure about it's weight.
I did cut 4" round lightening holes spaced in the wing skin between ribs. I did not want to create a stress riser that might tear the cardboard so I made the holes round and I also treated the edges of the hole with titebond glue to add strength.
One thing I didn't mention is how fast it goes together. I spent way more time figuring out how to do it than in actually building it. I treated cardboard on Tuesday night, cut it out parts on Wed. & Thurs. night and I built it on Friday night & Saturday. I installed the engine, tank and L.G. on Sunday. I am a slow builder so I was suprised how fast it came together. Of course, there is a low parts count which helps to speed things up. I trimmed it out & began flying it the next week.
Doc, I hope this answers your question. This plane was kind of like a balsa plane with a really bad finish that flies really great. You end up liking the ugly beast even if it wasn't pretty, in spite of yourself.
Pat Robinson
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I built 4 cardboard 1/2a models several years ago as a "diversion" from .40 size stunters. All were profiles with flat wings. I sold 3 to local club members and have one left. They do loops, lazy eights and go inverted, but won't do the more complex stunts. I can't post pictures here but will email some to anyone who asks: stuntcl@alltel.net
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I seem to remember a company called US AirCore was selling RC planes made from corrigated plastic( the stuff US Mail handler boxes used on their mail trucks) I never owned one, but I read that they were/are virtually indestructable. Its already fuelproof and their designs are just fold and glue. In fact, I dont even think there are any ribs, just a main spar. I'm not sure where to buy the stuff..but may be worth looking at to fabricate some super trainers!
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The Jan.1960 issue of Model Airplane News on page 22 has an article called "Bamboozle". It's a half A, .15 and a .35 size planes with a bamboo fuse. and flat cardboard flying surfaces. Written by George Xenakis. It says the .35 size has 420 sq in at 26 oz. the .15 has188 sq. at 18 oz. and the .049 has 105 sq. and 7 oz. Full size plans available. See page 58.
I built a cardboard free flight that looked like a J3 back in the 50s. When I got it balanced and trimmed it took 3 days to find it.
Perry Rose
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Hi Guys,
Chuck Felton here. You were talking about my favorite model subject, cardboard planes. I just wanted to show you what can be accomplished using corrugated cardboard as a building material. The first photo is a 65" wingspan WW2 Douglas Destroyer powered by a 60 engine. It weighs 7 pounds fueled with a wing loading of 20 oz/sq ft. It makes a fun sport flying model, especially with throttle control. The second photo is a 72" wingspan Junkers W33 transport. The unusual wing shape is easy to cut out of one large piece of cardboard folded at the leading edge and along the top curved surface.
Obviously, I enjoy building scale models. But I would love to see one of you guys build a typical symmetrical wing stunt model out of corrugated cardboard to see how well it could fly the pattern. To see more cardboard models and building techniques, go to my website at
http://home.earthlink.net/~charlesfelton
Regards, Chuck
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Chuck, just came from your site and it is fantastic. I have read your articles in the past and have often thought of using one of your designs. As soon as I am done with current project I may take you up on your challenge of a card board(corogated paper) for a aerobatic design. Have fun, DOC Holliday