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40% 260 on a Diet

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Old 12-29-2006, 10:48 PM
  #51
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Default RE: 40% 260 on a Diet

A few more photos.............

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Old 12-29-2006, 11:25 PM
  #52
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Bottom Section

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Old 12-29-2006, 11:41 PM
  #53
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Default RE: 40% 260 on a Diet

Looks great!

Almost as a Composite aircraft, probably not as strong......
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Old 12-29-2006, 11:53 PM
  #54
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Default RE: 40% 260 on a Diet

Canopy Section
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Old 12-30-2006, 10:19 AM
  #55
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Default RE: 40% 260 on a Diet

260man,

I have no doubt that you will have an extremely light 260 but don't you think that by removing the side sheeting and all of the diagonal braces that you will have an airplane that will twist like a pretzel every time you touch the aileron stick. One of the things that make a carden fly so well is that extremely rigid fuse that doesn't twist.

Albert
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Old 12-30-2006, 08:17 PM
  #56
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Quote:
ORIGINAL: as722

260man,

I have no doubt that you will have an extremely light 260 but don't you think that by removing the side sheeting and all of the diagonal braces that you will have an airplane that will twist like a pretzel every time you touch the aileron stick. One of the things that make a carden fly so well is that extremely rigid fuse that doesn't twist.

Albert
Albert,

What makes you think it will twist. I have checked it over and over as I am building and there is NO twist... NONE...........

The span of the verticals are reduced from the plan (I added more vertical balsa sticks). I did install the cross braces per the plan along the top of the aircraft. In the canopy area, I will add some diagonals because there is no top support, such as the tail and bottom. The turtle deck and the bottom decking ads strength reducing twist. One other thing that most people will not think about is that the covering has a 25,000 PSI tensile strength. Look at this web site http://gaboats.com/tutorials/monokote.html

The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. The definition of failure can vary according to material type and design methodology. This is an important concept in engineering, especially in the fields of material science, mechanical engineering and structural engineering.
There are three typical definitions of tensile strength:
• Yield strength - The stress a material can withstand without permanent deformation. This is not a sharply defined point. Yield strength is the stress which will cause a permanent deformation of 0.2% of the original dimension.
• Ultimate strength - The maximum stress a material can withstand.
• Breaking strength - The stress coordinate on the stress-strain curve at the point of rupture.
I hope this helps………

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Old 12-30-2006, 08:43 PM
  #57
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Default RE: 40% 260 on a Diet

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Old 12-30-2006, 08:46 PM
  #58
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Default RE: 40% 260 on a Diet

Why double the verticals and take out the cross bracing that makes no sense from a structural standpoint. If you really wanted to reduce weight you could have added distance between the verticals and kept the diagonals - there's a reason we use triangles to strenghten stuff lol. Added more verticals doesn't help at all. In the vertical plane a few verticals would have been enough. It's the other planes that needed the help. You added strenth you didn't need and took away what you did need.
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Old 12-30-2006, 09:02 PM
  #59
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Quote:
ORIGINAL: Bob101

Why double the verticals and take out the cross bracing that makes no sense from a structural standpoint. If you really wanted to reduce weight you could have added distance between the verticals and kept the diagonals - there's a reason we use triangles to strenghten stuff lol. Added more verticals doesn't help at all. In the vertical plane a few verticals would have been enough. It's the other planes that needed the help. You added strenth you didn't need and took away what you did need.

LOL as you say Bob, there is a reason I chose to build MY aircraft the way I want to.

But thanks for adding your opinion. [sm=tongue_smile.gif]











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Old 12-30-2006, 09:19 PM
  #60
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Default RE: 40% 260 on a Diet

I dont know much about Tensile strength but are are you saying that the covering will help hold this plane together?
I've seen covering (Monokote, Ultracote) split because of loads on a twisting airframe.
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Old 12-30-2006, 10:18 PM
  #61
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Default RE: 40% 260 on a Diet

I love this thread!!!

I have not seen this much B!tC&ing in one place in a long time!!!
Keep the good work guys!!!

And keep up the good building 260 man! Good luck on your 28lbs, I can't wait to see it fly!
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Old 12-31-2006, 01:13 AM
  #62
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Default RE: 40% 260 on a Diet

I fear for the poeple who show up to watch this banana of a plane fly. Like I said I know someone who built a 35% and didn't get near as radical as you and the sheeting rippled to the point they quit flying it after a few flights...I could literally see you doing a wall/snap or whatever and the tail just ripping off the plane. Oh yeah I don't know much about structures - I'm just an structural engineer by trade.
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Old 12-31-2006, 08:12 AM
  #63
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Default RE: 40% 260 on a Diet

260man,

A 25,000 psi tensile strenght on monokote only applies when it is pulled on, it will not prevent your fuse from twisting. It sounds like you have it all figured out and I'm sure you'll get thousands of flights on it without twisting. Good luck with your project.

Albert
Quote:
ORIGINAL: 260 Man


Quote:
ORIGINAL: as722

260man,

I have no doubt that you will have an extremely light 260 but don't you think that by removing the side sheeting and all of the diagonal braces that you will have an airplane that will twist like a pretzel every time you touch the aileron stick. One of the things that make a carden fly so well is that extremely rigid fuse that doesn't twist.

Albert
Albert,

What makes you think it will twist. I have checked it over and over as I am building and there is NO twist... NONE...........

The span of the verticals are reduced from the plan (I added more vertical balsa sticks). I did install the cross braces per the plan along the top of the aircraft. In the canopy area, I will add some diagonals because there is no top support, such as the tail and bottom. The turtle deck and the bottom decking ads strength reducing twist. One other thing that most people will not think about is that the covering has a 25,000 PSI tensile strength. Look at this web site http://gaboats.com/tutorials/monokote.html

The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. The definition of failure can vary according to material type and design methodology. This is an important concept in engineering, especially in the fields of material science, mechanical engineering and structural engineering.
There are three typical definitions of tensile strength:
• Yield strength - The stress a material can withstand without permanent deformation. This is not a sharply defined point. Yield strength is the stress which will cause a permanent deformation of 0.2% of the original dimension.
• Ultimate strength - The maximum stress a material can withstand.
• Breaking strength - The stress coordinate on the stress-strain curve at the point of rupture.
I hope this helps………

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Old 12-31-2006, 09:01 AM
  #64
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Default RE: 40% 260 on a Diet

OMG lol now tell me what the compression strength of monokote is compared to it's tensile strength.
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Old 12-31-2006, 09:31 AM
  #65
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Default RE: 40% 260 on a Diet


Quote:
ORIGINAL: wgeffon

I dont know much about Tensile strength but are are you saying that the covering will help hold this plane together?
I've seen covering (Monokote, Ultracote) split because of loads on a twisting airframe.
Yes, the covering really adds quite a bit of strength and stiffness to any model. It is the stressed-skin concept of engineering. Stresses are highest in bending at the surface of a beam (or wing for example). The covering is weak in compression, but if one side is in compression the other side is under tension. Competition fun fly airplanes have used this concept for many years. Ultrakote is much better than monokote (for strength and stiffness of the plane) because it doesn't tear (not as brittle) as easily. However, there is no easy way to predict if the total airframe is strong and stiff enough for the flight loads. Proof comes when it flys.
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Old 12-31-2006, 09:54 AM
  #66
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Default RE: 40% 260 on a Diet

Ted,

Covering will not hold a 40% plane together.
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Old 12-31-2006, 10:44 AM
  #67
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Default RE: 40% 260 on a Diet


Quote:
ORIGINAL: wgeffon

Ted,

Covering will not hold a 40% plane together.
How about foam, balsa, plywood, glue, and covering?
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Old 12-31-2006, 10:58 AM
  #68
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Quote:
ORIGINAL: Bob101

OMG lol now tell me what the compression strength of monokote is compared to it's tensile strength.
How about this, you sit back and watch the thread or NOT. Keep your negative opinions to yourself and I promise not to ever fly in, around, or near your part of TX. Nor will I ever question you or your methods of doing things, not even your "I'm just an structural engineer by trade" comment. You have no clue what I do for a living nor is it your business, but I have been doing it long enough to know that there is always more than one way to do anything. Now getty up cowboy.

Respectfully,

ME 260 Man
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Old 12-31-2006, 11:07 AM
  #69
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Quote:
ORIGINAL: Diablo-RCU



How about foam, balsa, plywood, glue, and covering?

IMO. No.
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Old 12-31-2006, 11:25 AM
  #70
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Default RE: 40% 260 on a Diet

Here's some data to ponder. Putting down monokote on top of a piece of 1/16 inch balsa sheeting (light to medium density) increases the strength by 28-73%. Balsa has a tensile strength of 1.1-2.9 ksi, and monokote is 25 ksi.

And now back to the build.....
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Old 12-31-2006, 11:58 AM
  #71
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Default RE: 40% 260 on a Diet


Quote:
ORIGINAL: Diablo-RCU


Quote:
ORIGINAL: wgeffon

I dont know much about Tensile strength but are are you saying that the covering will help hold this plane together?
I've seen covering (Monokote, Ultracote) split because of loads on a twisting airframe.
Yes, the covering really adds quite a bit of strength and stiffness to any model. It is the stressed-skin concept of engineering. Stresses are highest in bending at the surface of a beam (or wing for example). The covering is weak in compression, but if one side is in compression the other side is under tension. Competition fun fly airplanes have used this concept for many years. Ultrakote is much better than monokote (for strength and stiffness of the plane) because it doesn't tear (not as brittle) as easily. However, there is no easy way to predict if the total airframe is strong and stiff enough for the flight loads. Proof comes when it flys.
I was wondering how long it would take
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Old 12-31-2006, 12:42 PM
  #72
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Quote:
ORIGINAL: wgeffon

I say go for it.

This is a Carden 300 that is being built for me right now. Mods are being done to it but nothing more than the typical modded Carden now a days.
Here are some shots of the fuse as it sits right now. What do people think it weighs as it looks in these pics?(Its a little further along than the one this thread is about. It has the tank tray, cannister mount, Tunnel top and the motor mount installed.)

Care to guess?

I was going to guess it weighs about $1600 as shown?
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Old 12-31-2006, 01:39 PM
  #73
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Default RE: 40% 260 on a Diet

Quote:
ORIGINAL: Diablo-RCU

Here's some data to ponder. Putting down monokote on top of a piece of 1/16 inch balsa sheeting (light to medium density) increases the strength by 28-73%. Balsa has a tensile strength of 1.1-2.9 ksi, and monokote is 25 ksi.
Data???

I had always geard that Putting down monokote on top of a piece of 1/16 inch balsa sheeting (light to medium density) increases the strength by 28-73%.

Ted, Everyone knows that the actual figures are 29.34 and 71.9886%



Monokote will not hold an improperly built plane together.
You can throw data around all you want but comon sense has to come into play at some point..

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Old 12-31-2006, 02:03 PM
  #74
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Default RE: 40% 260 on a Diet

If your relying on the covering keeping the plane together you got problems.
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Old 12-31-2006, 05:36 PM
  #75
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Default RE: 40% 260 on a Diet

More work today.......

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