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Old Jul 24, 2010, 11:36 AM
Just shut up and build!
Sri Lanka
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Cessna 180 from Paul Bradleys Model Airplane Plans Page

Found these plans for sheet balsa - they seem the ideal starting kit. The Cessna 180 looks particularly good

http://www.parmodels.com/Plans/index.htm

Look under the link
" Reproductions of the old 1950's Top Flite Jigtime Models, Carl Goldberg and Keil Kraft EeZeBilt sheet balsa rubber powered Free Flight models"

Downloaded plans
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Old Jul 24, 2010, 02:13 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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Yep, some nice plans there.

Do a search back a few years in this free flight section and you'll find some threads about guys that built some of these jigtime models from the plans when Paul first put them up on his site.
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Old Jul 25, 2010, 12:45 AM
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Sri Lanka
Joined Mar 2010
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Great idea- I was looking for these . for reference I post these links here:

http://www.rcgroups.com/forums/showt...hlight=jigtime

http://www.rcgroups.com/forums/showt...hlight=jigtime

Other links to vintage rubber scale : I really should start an info thread:

http://www.cahood.com/webcat8c.htm

Found a video as well. That plane is really light

Indoor Freeflight Cessna 180 (0 min 43 sec)
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Last edited by knlever; Jul 25, 2010 at 10:13 AM. Reason: found a vid
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Old Jul 25, 2010, 10:18 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
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Downloaded the plans

Downloaded the PDF - it is a small model about 40 cm span - smaller that I thought, I will have to enlarge it to a 1:20 which means a 55cm model
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Old Jul 25, 2010, 01:29 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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I assume you'll then be working to make it using card stock and other materials?
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Old Jul 25, 2010, 03:54 PM
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Beaumont tx
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How many turns for that flight? Where'd you get the helium?

Lovely!

howell
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Old Jul 25, 2010, 10:10 PM
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Independence, KY and Brandon, MS
Joined Jun 2000
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Howell - When built with decent 1/32" balsa they all fly like the model in the video. When it comes to Free Flight, light is might. All of the prototype models I built from the plan packages fly like the Cessna 180 in the video. My models use a single loop of 1/8" rubber that is about 1.5 times the length between the prop hook and rear anchor. I typically get 1100 to 1200 turns on a lubed motor. That translates into flights in the 40 second range indoors.

The orignal kits used 1/16" balsa that was quite heavy. As a result their flying performace suffered greatly. When built light they really show what good designs these models were.

Paul Bradley
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Old Jul 26, 2010, 10:21 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
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Well I will be using cereal box cardboard, whatever that is called, bamboo and recycled 80 gsm paper or so.

That, plus several problem solving methods will be reviewed and a few chosen. I have made such a lot of progress using problem solving methods, for some people it is built in to their thinking, some people try trial and error or maybe engineering practices they are used to

To recap:

Abstraction: solving the problem in a model of the system before applying it to the real system
###
The model follows the standard flight model - lift, drag, weight, thrust
The model should have enough wing area to support its weight. This should happen at its 'cruising speed', that is the speed that the motor is able to sustain through the prop. Weights should be kept at less that 40 g, the wing will sustain the weight, as verified by testing. The power of the prop against drag is not verifiable through this model
###

Analogy: using a solution that solved an analogous problem
###
Looking at similar models - 40 g weight and the 50 cm span, together with the prop and rubber used should sustain the model.
###

Brainstorming: (especially among groups of people) suggesting a large number of solutions or ideas and combining and developing them until an optimum is found
###
Not tried
###

Divide and conquer: breaking down a large, complex problem into smaller, solvable problems
###
An obvious physical approach would be to break the model down into wings, tail, fuselage and rubber power. Building a wing is basically OK, I can do that, and the tail surfaces pose no problem. The rubber motor has been tested. The only problems not solved are :

- ensuring a strong wing/fuselage attachment,
- a light fuselage
- a fuselage that will resist the pull of the rubber.

These may be tested separately
###

Hypothesis testing: assuming a possible explanation to the problem and trying to prove (or, in some contexts, disprove) the assumption
###
This has been looked at : high weight, low power not enough rigidity, these will be addressed
###

Lateral thinking: approaching solutions indirectly and creatively
###
Not tried
###

Means-ends analysis: choosing an action at each step to move closer to the goal
###
This is not tried as it will involve several models with each one improving on the other - will use up a lot of time and materials
###

Method of focal objects: synthesizing seemingly non-matching characteristics of different objects into something new
###
not tried
###

Morphological analysis: assessing the output and interactions of an entire system

###
Not Tried
###

Reduction: transforming the problem into another problem for which solutions exist
###
Not tried, redundant in the light of the above
###

Research: employing existing ideas or adapting existing solutions to similar problems
###
Not tried, lack the instrumentation to carry out research with measurements
However adapting existing solutions is part of the plan
###

Root cause analysis: eliminating the cause of the problem
###
Applies to an existing trial model that was built
Root cause related to construction methods
###

Trial-and-error: testing possible solutions until the right one is found
###
I hope I do not have to do this - this is too wide open, actually it leads to too many branches to follow, and I have been trying this so far which is very time consuming
###


PCDA
###
Plan-Do-Check-Act
###

http://en.wikipedia.org/wiki/PDCA

Appeciation
What good things need to be improved?

So what is the final yield - applying all these approaches?


- Aim for a weight of 40g or less
- Wingspan of 50cm
- Build tail surfaces and a test fuselage, test strength of attachment points and brace as necessary
- build a model of the model on a smaller scale, study it and correct any problems


This may seem 'trivial' , however I know that I have looked at the problem from many angles, and have obtained some useful information. I have a specific method now for trying out, and know what to do after that.

I will print out the existing plan in its 1:32 size, cut and paste on a cereal box and test for strength, weight, attachment points etc. Then I have to act.

Should be fun
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Old Jul 26, 2010, 10:28 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
652 Posts
Paul

Excellent plans and these kits have a charm of their own. How much do the originals weigh and how much did the 1/32 models weight - all up with rubber?

Could you tell me what sort of rubber and prop you are using? The models shown here give specs - 30-40 g and 25" or 50 cm or so wingspan. http://darehobby.com/ see under Airplanes > rubber 1
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Old Jul 26, 2010, 02:42 PM
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Beaumont tx
Joined Oct 2004
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Well, I see at least two differences between my old ones and yours -- wood thickness and number of turns.

Aside from THAT.....

thanks, as always

howell
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Old Jul 26, 2010, 02:42 PM
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PS. When do you live in Brandon? I grew up in Starkville.

howell
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Old Jul 26, 2010, 06:33 PM
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Sri Lanka
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With the original plan and its standard the wood thickness, the instructions in the manual state that 75 to 1000 turns will get you 20 to 30 seconds of flight.

Advertising?.
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Old Jul 26, 2010, 11:30 PM
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Independence, KY and Brandon, MS
Joined Jun 2000
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knlever - For my Jigtime reproductions I use a single loop of 1/8" rubber that is 1.5 times the length between the prop hook and rear motor anchor peg. With rubber the models weight in the 15 gram range. Some slightly lighter and some just a bit heavier. I am using a 5.5" plastic prop of the style sold by Sig for models like the AMA Cub. My stated flight times are indoors. Outdoors times go up due to passing lift. The original kits could fly for the stated advertised times if you got one made from decent balsa, you replaced the prop with one of larger diameter, replaced the supplied rubber band with proper lubed rubber, and you used a winder. Not likely though with the supplied prop and rubber band.

The original models were generally in excess of 30 grams. They were guaranteed to fly and fly they did. Just not very long. Back in the day there used to be contests for the Jigtime models. The rules allowed you to replace the tiny kit prop and you could sand the wood to thin it out. All of the kit printing still had to be present so the builders would sand the back side of the die cut sheets before removing the parts. They would sand the sheet to nearly paper thin. The dense balsa allowed a lot of sanding without dramatic loss of strength. Competitive times, indoors, were well in excess of a minute.

Howell - my house in Brandon, MS is near the big Ross Barnett reservoir.
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Old Jul 27, 2010, 09:20 AM
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Beaumont tx
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Lovely country; I remember when the RB was built and they had to reroute the Natchez Trace -- through some residential districts as I recall.

howell
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Old Jul 29, 2010, 07:15 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
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Just in case : there is a thread about conversion to RC of a similar plan:

http://www.rcgroups.com/forums/showthread.php?t=657479

For free flight electric what sort of motor/batt/prop will work, I wonder...
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