HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 16, 2013, 10:03 AM
Registered User
acesimmer's Avatar
United States, NV, Fernley
Joined Oct 2011
2,135 Posts
Discussion
Composite skinned wing structure

I have a T28 manufactured foam model to composite conversion build thread. I have completed the entire fuselage and tail molds and have two models in assemble readying for test flights using the original foam wing.

I know of several ways to make wings that are strong and relatively light. This model is highly detailed so I plan on making detailed epoxy glass wing skins from molds. I know that going composite will add weight so I'm looking for ideas and or previous designs that will be strong yet reasonably light weight that are skinned on the outer surface.

I plan on testing several concepts from foam board internal structure to 2k expanded foam. I think this would be a great thread for many of us to get involved with. So far most of the research that I have found is usually to do with gliders. I'm talking scale models from 50" wingspan and up.

I have refined my other layup techniques so that I have reduce weight and increased strength by laying up with strips instead of whole pieces of cloth. These strips have a small overlap that provides great rigidity with minimal weight buildup. So now it is time to tackle the wing. Following is my build thread.

The Challenge
- Simple approach with out using expensive vacuum bagging etc.
- Not using carbon fiber in the structure.
- New creative inexpensive techniques/ideas.



I look forward to having you all involved.....

http://www.rcgroups.com/forums/showthread.php?t=1767143
acesimmer is offline Find More Posts by acesimmer
Last edited by acesimmer; Jan 16, 2013 at 10:09 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 17, 2013, 08:51 AM
Registered User
Cleveland Cuyahoga, Ohio, United States
Joined Dec 2000
401 Posts
Your car can be your vacumm pump. 8 to 9 pounds of vac.
It will be a much lighter layup, try it.
JIM CALDWELL A is offline Find More Posts by JIM CALDWELL A
Reply With Quote
Old Jan 17, 2013, 12:10 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
3,376 Posts
The guy who got me started with glassing presses his wings between sections of kitchen countertop strengthened with steel channel.F clamps for pressure.His occupation- carbon composite parts for F1 cars.
Stupot46 is offline Find More Posts by Stupot46
Reply With Quote
Old Jan 17, 2013, 02:53 PM
Registered User
acesimmer's Avatar
United States, NV, Fernley
Joined Oct 2011
2,135 Posts
it seems we have a misunderstanding. I'm really trying to get ideas on the internal structure that will stiffen the wing yet be quite light weight. I've heard of people using foam core board and the like for ribs etc.
acesimmer is offline Find More Posts by acesimmer
Reply With Quote
Old Jan 17, 2013, 03:25 PM
2012 NZ Speedcup - 231 MPH
DownUnderPilot's Avatar
New Zealand, Tasman, Richmond
Joined Mar 2006
2,085 Posts
Are you talking about spar design specifically?
DownUnderPilot is online now Find More Posts by DownUnderPilot
Reply With Quote
Old Jan 17, 2013, 04:01 PM
Now fortified with carbon
DLGjunkyard's Avatar
Canada, ON, Cambridge
Joined Apr 2010
2,781 Posts
Forgive me if this comes off a bit bias but your OP nailed it. Glider guys know how to built light strong wings and for that reason use carbon fiber for both skins and spars. You could use vertical grain balsa with spruce spar caps but the lighter alternative is, you guessed it, Carbon.

OTOH , You could use a foam core, sparless wing by vacuum bagging balsa sheets as wing skins. AKA sloper design from yrs ago.
DLGjunkyard is offline Find More Posts by DLGjunkyard
Reply With Quote
Old Jan 17, 2013, 06:37 PM
Entropy is happening!
Jim.Thompson's Avatar
Australia, NSW, Bellingen
Joined Aug 2008
7,308 Posts
Carbon / Vacuum avoidance?

Quote:
Originally Posted by acesimmer View Post
I .................................................. ................... So far most of the research that I have found is usually to do with gliders. .......................
http://www.rcgroups.com/forums/showthread.php?t=1767143
What the problem with that?

There is an extensive thread exploring the use of 2 pack PU foams on these forums. Conclusions are mixed, at best.

If you want light and strong, methods have been developed to achieve that. Non more so than by the DLG fraternity! I don't build DLG's (yet), but much can be learned from them.
They almost always employ two things proscribed on your list:
1. Carbon
2. Vacuum bagging methods.

For what it's worth.

Jim.

We go forth on the shoulders of giants!
Jim.Thompson is offline Find More Posts by Jim.Thompson
RCG Plus Member
Last edited by Jim.Thompson; Jan 17, 2013 at 07:22 PM. Reason: Spelling correction
Reply With Quote
Old Jan 17, 2013, 06:55 PM
Now fortified with carbon
DLGjunkyard's Avatar
Canada, ON, Cambridge
Joined Apr 2010
2,781 Posts
Quote:
Originally Posted by Jim.Thompson View Post
What the problem with that?

There is an extensive thread exploring the use of 2 pack PU foams on these forums. Conclusions are mixed, at best.

If you want light and strong, methods have been developed to achieve that. Non more so than by the DLG fraternity! I don't build DLG's (yet), but much can be learned from them.
They almost always employ two things proscripted on your list:
1. Carbon
2. Vacuum bagging methods.

For what it's worth.

Jim.

We go forth on the shoulders of giants!
Bingo And to add to that DLG wings are much higher aspect ratios rendering the task much harder opposed to warbird wings which are much thicker and shorter spans
DLGjunkyard is offline Find More Posts by DLGjunkyard
Reply With Quote
Old Jan 17, 2013, 07:19 PM
Registered User
acesimmer's Avatar
United States, NV, Fernley
Joined Oct 2011
2,135 Posts
Yes I guess the glider guys know best. I'm intending to bag the wings and was just hoping for a less expensive alternative than Carbon. My problem is a lack of suppliers for the sandwich foam in the local area. I'll just have to hunt for a deal. Thanks for the info to date.
acesimmer is offline Find More Posts by acesimmer
Reply With Quote
Old Jan 17, 2013, 07:28 PM
Now fortified with carbon
DLGjunkyard's Avatar
Canada, ON, Cambridge
Joined Apr 2010
2,781 Posts
Fair enough. Dont assume though that all carbon built wings are expensive. You could easily use glass skins with unicarbon spars. You could also use carbon rods embedded into the foam with a dremal.
The foam can be simple Dow blue foam at about 35 per 4x8 2 inch sheets.
Another cheaper variety of carbon is known as 80/20 which is S glass with carbon running the warp direction.The treat about using foam cores is the foam acts as the shear webbing and unicarbon acts as the spar caps.
DLGjunkyard is offline Find More Posts by DLGjunkyard
Reply With Quote
Old Jan 17, 2013, 07:30 PM
Entropy is happening!
Jim.Thompson's Avatar
Australia, NSW, Bellingen
Joined Aug 2008
7,308 Posts
Quote:
Originally Posted by acesimmer View Post
............. I'm intending to bag the wings and was just hoping for a less expensive alternative than Carbon. ...........
This is at variance with your opening post!
Are you going to vacuum bag or not vacuum bag?

As for less expensive, full carbon skins are not absolutely necessary to achieve the strength you probably require, especially given you can afford to sacrifice some strength weight ratio in a powered plane. Carbon spar caps are almost mandatory in my estimation. The cost/strength ratio of carbon tow spar caps will blow any other material away. It's inexpensive compared to carbon cloths etc.

Please note my spelling correction in my previous post.

Jim.
Jim.Thompson is offline Find More Posts by Jim.Thompson
RCG Plus Member
Latest blog entry: Gravity hot wire foam cutter.
Reply With Quote
Old Jan 17, 2013, 08:11 PM
R.I.P
josh18's Avatar
Australia, QLD, Toowoomba
Joined Jan 2010
3,560 Posts
Hey Ace, I was told not to re-invent the wheel when I started building planes, I think this was some sage advice. If you are going for moulded, which is really the only way, if you want the detail imprinted into the wing, you need to bag it to get what you want. Use balsa as a sandwich medium and carbon is definitely not necessary for the skins, but uni carbon or tow is needed for the spar caps- dont worry, its pretty cheap. The reason you need to bag is because to make a light hollow moulded skin it needs a core and I cant see how you could do this with out bagging it, especially if your tips have compound curves. Also when bagging a lot of excess resin/ weight is sucked out of the layup- so you end upwith a much lighter and stronger skin. A good layup for cheap/lightish/strong is, from the outside in, 4 or 6oz glass/ 1.5mm balsa/ 2oz glass. Some will say this is too heavy, maybe it is, but I have forund it a good compromise between stiffness, dent resistance and light weight. Also, bagging equipment doesn't have to be expensive, get hold of an old fridge pump and some PVC drain pipe and you can start from there. There are many threads on how to build your vacuum set up.
Another advantage you will have with a PSS scaley is that the wing will have a pretty fat section, giving you lots of stiffness- Us glider guys have to put lots of carbon into the spar trying to make really thin arifoils stiff enough!
Good luck with it mate!
Josh
josh18 is online now Find More Posts by josh18
Reply With Quote
Old Jan 17, 2013, 09:56 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
If light weight is your objective then some type of sandwich constructed skin with internal shear webs would be the way to go.
wyowindworks is offline Find More Posts by wyowindworks
Reply With Quote
Old Jan 25, 2013, 05:58 AM
Entropy is happening!
Jim.Thompson's Avatar
Australia, NSW, Bellingen
Joined Aug 2008
7,308 Posts
Where did you go Ace?
Jim.Thompson is offline Find More Posts by Jim.Thompson
RCG Plus Member
Latest blog entry: Gravity hot wire foam cutter.
Reply With Quote
Old Jan 25, 2013, 08:43 AM
Registered User
acesimmer's Avatar
United States, NV, Fernley
Joined Oct 2011
2,135 Posts
Quote:
Originally Posted by Jim.Thompson View Post
Where did you go Ace?
Sorry..... I've been testing a new fast curing plastic for pressure casting engines. Also, been looking out for a vacuum bagging system as it seems its the only way to go. Also, been gathering supplies for the wing.
acesimmer is offline Find More Posts by acesimmer
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
For Sale Rohacell structural foam! Wing skins, Tail cores FairlyFaded Aircraft - Sailplanes (FS/W) 7 Jun 25, 2014 11:43 AM
Question Wing Structure Question payne9999 Giant Electric Planes 8 Feb 29, 2012 11:34 PM
Idea Another ridiculous idea? Glass skinning a built up structure... MCarlton The Builders Workshop 11 Sep 18, 2011 05:07 AM
Discussion pre-fab composite wing skins luger007 Composites Fabrication 23 Jan 30, 2010 11:48 PM