Shop our Airplanes Products Shop our Surface Products
Thread Tools
Old May 19, 2015, 03:22 PM
James Brand is offline
Find More Posts by James Brand
Registered User
United Kingdom, Devon
Joined Nov 2014
262 Posts
Question
why glass foam veneer wings?

here i am merrily glassing away on a set of wings....then i move on to another set i allready laminated and started spraying the layers of primer ready for sanding then top coating .......then it all of a sudden dawned on me.................

why do we laminate? with todays paint technologies is there any need to glass? i mean i spray boats and bits for boats and you dont realy ever laminate under paint on wooden things like rubbing streaks so why on wings? you cant argue strength because there is no strength in iron on film.

and why 2k finish? most boat paints are now epoxy and would probaly offer similar strength propertys to a laminated wing..... so..enlighten me......
James Brand is offline Find More Posts by James Brand
Reply With Quote
Sign up now
to remove ads between posts
Old May 19, 2015, 11:43 PM
swarrans is offline
Find More Posts by swarrans
I'm a glider pilot really.....
United Kingdom, England, Kent
Joined Nov 2008
285 Posts
I am sure you are correct that you don't need to glass wings to get a good paint finish but the only reason for glassing IMHO is for strength. Clearly a film finish is going to add little or no strength so when you glass you do it because you want them to be stronger than that.
I'm a bit confused about your description of 2K and epoxy paints as they are both catalyst systems so presumably mean the same thing?

Simon
swarrans is offline Find More Posts by swarrans
Reply With Quote
Old May 20, 2015, 02:22 AM
James Brand is offline
Find More Posts by James Brand
Registered User
United Kingdom, Devon
Joined Nov 2014
262 Posts
yep sorry i was on about standard car 2k acrylic not urethanes surely boat paints are the way forward? i realy dont know if one layer of 50gsm glass is worth it. i mean i build surfboards for a living and when i laminate performace boards you are practicaly keeping the water out of the foam, there is not much structual use of the glass. all the strength is in the core material..

i was just wondering if its arbitrary?
James Brand is offline Find More Posts by James Brand
Reply With Quote
Old May 20, 2015, 03:10 AM
Larrikin is offline
Find More Posts by Larrikin
Everything's A Compromise
Larrikin's Avatar
Joined Jan 2005
2,060 Posts
It depends if the manufacturer has put glass under the veneer.
Without the glass, (inside or outside) the veneer just splits along the grain under load. Learned that one a long time ago.

As far as 50 gsm on the outside of the veneer, it makes for a uniform substrate. Well, that's what I use it for anyway. Fill the veneer grain with a light weight putty (usually a thick mix of talc and epoxy) sand it smooth, glass over the top, prepare and paint.
Ends up looking like a moulded part.

David.
Larrikin is offline Find More Posts by Larrikin
Last edited by Larrikin; May 20, 2015 at 08:21 AM. Reason: spelling
Reply With Quote
Old May 20, 2015, 08:16 AM
Asher Carmichael is online now
Find More Posts by Asher Carmichael
"Fly"Fisherman
Asher Carmichael's Avatar
Guntersville, AL
Joined Jun 2004
861 Posts
I use glass as larrikin has described, primarily as a substrate for subsequent finishing. It also helps tie disparate components together(such as between the solid leading edge and the veneer, even joints in the veneer itself)which may be more likely to telegraph over time without the "glass" enhancement. I do agree it really isn't necessary if there is glass between the core and the veneer.

The idea of a composite structure is that the core's job is to give shape and hold the skins at a distance, which gives the whole structure its strength/stiffness. Likewise, the added glass on top of the wing may add some strength, perhaps more than we think.
Asher Carmichael is online now Find More Posts by Asher Carmichael
Last edited by Asher Carmichael; May 20, 2015 at 02:49 PM.
Reply With Quote
Old May 20, 2015, 01:41 PM
Sailhigh is offline
Find More Posts by Sailhigh
High Lift Coefficient
Sailhigh's Avatar
SF Bay Area, USA
Joined Feb 2003
2,113 Posts
I have a few (non-scale) aircraft from Arthobby that have no film covering or glass on the veneer surface. Just a few coats of sealer. Granted they're not 4 meter plus ships, but they are exclusively flown on the slope and flow hard and take a lot of abuse without showing signs of wear.
Sailhigh is offline Find More Posts by Sailhigh
Reply With Quote
Old May 20, 2015, 07:36 PM
SteveR is offline
Find More Posts by SteveR
Registered User
New York
Joined Feb 2002
3,368 Posts
Asher et al, I recently acquired a 4.5 meter Fox with Hans Muller obeche over foam wings. I'm tempted to glass the wings for the reasons noted above. What weight glass cloth would you recommend?

TIA,

Steve
SteveR is offline Find More Posts by SteveR
Reply With Quote
Old May 20, 2015, 07:49 PM
Larrikin is offline
Find More Posts by Larrikin
Everything's A Compromise
Larrikin's Avatar
Joined Jan 2005
2,060 Posts
Quote:
Originally Posted by SteveR View Post
What weight glass cloth would you recommend?

TIA,

Steve
Any plain weave glass in the 25-50 gsm would be fine IMO. Particularly on a model that size.

D.
Larrikin is offline Find More Posts by Larrikin
Reply With Quote
Old May 20, 2015, 09:36 PM
Asher Carmichael is online now
Find More Posts by Asher Carmichael
"Fly"Fisherman
Asher Carmichael's Avatar
Guntersville, AL
Joined Jun 2004
861 Posts
Quote:
Originally Posted by SteveR View Post
Asher et al, I recently acquired a 4.5 meter Fox with Hans Muller obeche over foam wings. I'm tempted to glass the wings for the reasons noted above. What weight glass cloth would you recommend?

TIA,

Steve

Steve,
If you're glassing for paint then .5oz -.75oz sq yd is fine. If covering with film, don't bother. The glass under paint is to help preserve the "effort" of painting.
Asher Carmichael is online now Find More Posts by Asher Carmichael
Reply With Quote
Old May 21, 2015, 01:01 AM
blanik213 is offline
Find More Posts by blanik213
BLANIK213
blanik213's Avatar
United States, NY, Phoenicia
Joined Feb 2008
678 Posts
Hi steve glassing the wings of your Fox is the way to go it will add strength by improving the wings rigidity .It acts like a exoskeleton helping to distribute stress loads on the entire wing structure (it's much more than a smoth paint surface).
Woody
blanik213 is offline Find More Posts by blanik213
Reply With Quote
Old May 21, 2015, 02:05 AM
James Brand is offline
Find More Posts by James Brand
Registered User
United Kingdom, Devon
Joined Nov 2014
262 Posts
the laminate needs to be drum tight, no pools or dry patches think of pre tentioned concrete, work the squeegee from the middle out it probablt takes me 20-40 miniuits to glass a 4m wingset.
James Brand is offline Find More Posts by James Brand
Reply With Quote
Old May 21, 2015, 08:09 AM
SteveR is offline
Find More Posts by SteveR
Registered User
New York
Joined Feb 2002
3,368 Posts
Thanks guys, greatly appreciate the info.

Steve
SteveR is offline Find More Posts by SteveR
Reply With Quote
Old May 21, 2015, 01:06 PM
MooSey-UK is offline
Find More Posts by MooSey-UK
Born Again Idiot
MooSey-UK's Avatar
United Kingdom, Wiltshire
Joined Jul 2007
453 Posts
For me a light layer of glass cloth offers nothing more than a more 'ding' proof wing or a base to spray. The strength imparted to a foam veneer wing is not much but it does improve the torsional rigidity a bit.
Ref your comment on film not giving any strength....... I think you would be surprised how much it actually does.
MooSey-UK is offline Find More Posts by MooSey-UK
Reply With Quote
Old May 22, 2015, 02:19 AM
James Brand is offline
Find More Posts by James Brand
Registered User
United Kingdom, Devon
Joined Nov 2014
262 Posts
it probaby does give strength along the length by miniscule amounts. glass is definately stronger but comes at a big weight penalty.

so why veneer? you may aswell just glass the foam cores, 3/ 4layers of 25gsm plain weave would be fine.
James Brand is offline Find More Posts by James Brand
Reply With Quote
Old May 22, 2015, 03:21 AM
DrFragnasty is offline
Find More Posts by DrFragnasty
Thermal Wrangler
DrFragnasty's Avatar
Launceston Tasmania
Joined Mar 2004
2,457 Posts
I suggest apply 'glass on a bias of 30-45 deg for added torsional strength AND it makes going around the curvy bits easier.
DrFragnasty is offline Find More Posts by DrFragnasty
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Veneered foam wings Daniel tandy Balsa Builders 6 Mar 26, 2014 11:59 AM
A little research, do you want Obechi veneer foam wings? graham_mca Product Announcements 4 Mar 20, 2014 05:05 PM
Veneered foam wing repair leccyflyer The Builders Workshop 3 Nov 19, 2004 02:09 PM
custom made foam/obechi veneer wings graham_mca The Builders Workshop 0 Aug 17, 2004 11:38 PM
How to stiffen up veneer foam wings... Vic Peh Electric Sailplanes 3 Sep 22, 2003 08:04 PM