HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 27, 2011, 06:36 AM
yes, its a flying lamb :)
draganbt's Avatar
Bitola, Republic of Macedonia
Joined Apr 2009
532 Posts
I noticed the wing is positioned differently on the two pictures. Do you trim the cg with moving the wing position? It's actually quite a nice way to trim a model, no additional weight needed. You might wanna increase the dihedral if it's an option.

Nice work knlever
draganbt is offline Find More Posts by draganbt
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 27, 2011, 09:53 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
The wing is mounted on a pylon which is why it looks different in each picture. I wanted the wing height to approximately match the wing height of the Cessna 172.

Moving the wing is a good way to change the CG, however in a scale model this is not an option. Thanks for the compliment I am working towards scale appearance and finish.
knlever is offline Find More Posts by knlever
Reply With Quote
Old Sep 15, 2012, 08:24 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
Building a few more models, and a few years on, especially with my paper and cardboard P-40 that flies for 5 seconds, I understand rubber powered flight much better now.

The P-40 flies nice and straight for 5 seconds, then falls from the sky. The critical factor is motor running time. Thinking back to the rubber powered models I have seen flying both on video and real life, I realize that essentially at the heart of these models is a low - rpm, long running rubber motor with a large prop. That seems to be the key. Winding up a Guillows type stick model with a larger prop got me 15 seconds of running time, which is a big increase.

So the plan is to build the motor first, run the prop and see if I get 20 seconds of running time. Then build a model with the wing loading that will fly, I think I can do this by using more paper than cardboard, paper is very strong, and I have tested a paper - spar wing that stands up well to wear and tear.
knlever is offline Find More Posts by knlever
Reply With Quote
Old Sep 16, 2012, 05:32 AM
Registered User
John Moore's Avatar
Southern Spain
Joined Nov 2003
231 Posts
Waste of time posting!
John Moore is offline Find More Posts by John Moore
Last edited by John Moore; Sep 17, 2012 at 07:48 AM. Reason: Posted in error
Reply With Quote
Old Jan 11, 2013, 06:25 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
Re-Launching the Cessna 180

Hope this is not a waste of time posting but here goes:

I must say I was very impressed by the kind helpful remarks of everyone who has contributed so far. I downloaded these pages and read them offline slowly - what a difference it makes - and so much information in these pages .

I am attempting again to build a cardboard / paper 180. This time with more knowledge and a few more experiences in building. My latest glider is 40 cm and weighs about 14g which is a huge improvement.

I will build each component and test for weight so the total comes to 20g or less.

Other changes:
  • Build own prop
  • Build as to avoid nose weight
  • Build a glider first and sort out trimming/durability/crash resistance issues
  • Neater building
  • Use thinner material than bamboo - coconut leaf spines are good
  • Use copper wire where needed to stiffen the wing for example
  • Do a lot of testing indoors - model should be light enough and durable enough for that

Also hope to post videos this time

First step - refining and calibrating my weighing scale
knlever is offline Find More Posts by knlever
Last edited by knlever; Jan 11, 2013 at 06:40 PM.
Reply With Quote
Old Jan 11, 2013, 09:53 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,290 Posts
Forget about the copper wire. It's far too heavy and simply not springy enough for the amount it weighs. If you need to stiffen something find other options.

A hint for if you need wire then get some unwound guitar strings and straighten them. You can straighten them by holding one end in a vise or other securing setup and the other end in an electric hand drill. Then while holding a LOT of tension run the drill for about 15 to 25 turns. This will straighten the wire nicely and from there you can use it for landing gears and other uses. This trick should work for wire up to around .030 thick. Beyond that I doubt if you can pull hard enough while running the hand drill.
BMatthews is offline Find More Posts by BMatthews
Reply With Quote
Old Jan 24, 2013, 11:40 AM
Registered User
John Moore's Avatar
Southern Spain
Joined Nov 2003
231 Posts
Use copper wire where needed to stiffen the wing for example

Copper wire is made to be flexible. How will that stiffen a cardboard wing?
Bamboo can be sliced to 0.5mm or less quite easily and weighs nothing in comparison to copper wire and you can sand it to a smooth surface.
John Moore is offline Find More Posts by John Moore
Reply With Quote
Old Jan 26, 2013, 11:16 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
Will try both and see how much each weighs. Actually the load will be carried by a main spar of cardboard or paper. Cardboard or paper does not have good impact resistance, that is where the copper wire will come in, bending, absorbing the strength and either springing back or be bent back. Bamboo is good, too, same thing here, impact strength.
knlever is offline Find More Posts by knlever
Reply With Quote
Old Apr 02, 2013, 05:16 PM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
2,845 Posts
In larger scale, conditions for good flyability are much better, as wing loading control gets less critical....

Watch THIS video.....the model is built entirely of cardboard and paper.....
This is a design degree project by Anna Poijo......impressive, and fun....
Gluehand is online now Find More Posts by Gluehand
Last edited by Gluehand; Apr 02, 2013 at 05:34 PM.
Reply With Quote
Old Apr 19, 2013, 06:45 PM
Registered User
carbondale il
Joined Jan 2007
2,557 Posts
knlever, Maybe you can succeed using the model in the video as a guide for construction. The thing I'm thinking of now to solve the rubber stress problem is with a tube. You could make experiments and go with the least possible weight for a tube inside the fuselage from prop shaft to rear motor mount, but no more, if you can calculate what size rubber motor would be needed and go with the least as possible. With a fuselage tube you wouldn't need to make the fuse form all that strong. It would only need to be shaped. The wing could be supported with rolled paper tubes, also, as main spars. And paper is paper, so if condenser paper is readily available you could cover with that. I wouldn't try to use water shrunken tissue after covering as that would most likely pull the frames way out of shape unless you pre shrink first and leave it at that.

Kev
kevin matthews is offline Find More Posts by kevin matthews
Reply With Quote
Old May 19, 2013, 06:03 AM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
Hi

Surprised to see people are still posting to this thread.

Very interesting video, thanks. I see they are using corrugated card for the construction, and there is an excellent site, as well as a recent model magazine article that I was lucky enough to purchase, that outlines how to build models out of corrugated cardboard.

I plan to yet again try to build a Cessna 180, I feel I have the right knowledge now, however as always, the problem is durability and crash resistance: I do not have the flying sites to fly these, any more. This means making short flights into trees or brick walls.

I will be looking into some sort of RTP model flying. I will probably build the Cessna as a proof of concept but that is it.

Actually I want to use a stick plane like I tested in this thread at the top of the page, and add a card fuselage and bigger, lighter wing. That should do the trick.

The Cessna 180 is a nice, stable model that will mean the difference between success and failure.
knlever is offline Find More Posts by knlever
Reply With Quote
Old May 19, 2013, 02:31 PM
Registered User
carbondale il
Joined Jan 2007
2,557 Posts
Don't worry about building for crash resistance, build it to fly.

Kev
kevin matthews is offline Find More Posts by kevin matthews
Reply With Quote
Old May 19, 2013, 02:47 PM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
2,845 Posts
Quote:
Originally Posted by kevin matthews View Post
Don't worry about building for crash resistance, build it to fly.
Well said..!

The more "crash resistant" you build, the more severe crashes you'll get..!
Thinking the opposite way is the way to go..

Gluehand is online now Find More Posts by Gluehand
Last edited by Gluehand; May 19, 2013 at 02:52 PM.
Reply With Quote
Old Jul 14, 2013, 07:01 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
Still working on it guys, thanks for the advice: crash resistance is low priority: after all most balsa models wont survive falling from a shelf!
knlever is offline Find More Posts by knlever
Last edited by knlever; Mar 25, 2014 at 07:11 PM. Reason: removed named site
Reply With Quote
Old Mar 25, 2014, 07:12 PM
Just shut up and build!
Sri Lanka
Joined Mar 2010
646 Posts
http://www.hippocketaeronautics.com/...topic=15896.25

excellent example to follow.
knlever is offline Find More Posts by knlever
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log CC Lee Rubber Powered Cessna 128 RC Convertion richos Scratchbuilt Indoor and Micro Models 10 Dec 26, 2010 05:31 AM
Discussion Calculating Energy requirement for Rubber Powered, Spring powered and electric flight knlever Modeling Science 66 Sep 13, 2010 09:36 AM
Link paper, rubber powered... FREE PLANS bazookie Free Flight 8 Jan 08, 2007 12:48 PM
Mountain Models Cessna 180 - construction pics! Martin Hunter Parkflyers 139 Aug 17, 2005 11:46 AM
A few MM Cessna 180 construction ideas Martin Hunter Parkflyers 22 Oct 21, 2002 02:13 AM