Thanks: 0
Likes: 0
Needs Pictures: 0
Picture(s) thanks: 0
Results 1 to 6 of 6
Thread: Glass strength
-
15th January 2012, 09:55 AM #1SENIOR MEMBER
- Join Date
- Aug 2008
- Location
- Birkdale
- Age
- 51
- Posts
- 279
Glass strength
Once glass has been wet out and allowed to cure, is there any further strength gained from the subsequent coats of epoxy, or is it simply making the surface smoother?
Thanks,
Chris
-
15th January 2012 09:55 AM # ADSGoogle Adsense Advertisement
- Join Date
- Always
- Location
- Advertising world
- Age
- 2010
- Posts
- Many
-
15th January 2012, 12:55 PM #2Senior Member
- Join Date
- Jun 2011
- Location
- Melbourne
- Posts
- 107
Assuming a good wet-out (which often takes at least two coats laid on hot), then fill-coats are cosmetic, from what I'm aware. Neat epoxy doesn't add much in strength in this application, it's really there to bond the glass.
That said, a decent thickness of epoxy helps to form a moisture barrier, and a smooth glass surface is less likely to trap dirt. Up to you.
I know of a few people who recommend letting the cloth weave stand proud, and paint it as a form of non-skid on decks, so it can't be too bad of a thing to leave the weave open!
-
15th January 2012, 10:01 PM #3
The glass gives the mechanical strength and the epoxy the chemical bonding, more resin will not add any strength , unless more glass is added at the same time.
Jeff
-
16th January 2012, 10:45 PM #4
G'day Chris
Might be a bit late for you if it has already cured...
The tensile strength in glass is unbroken strands. Sanding through the outer pox
into the actual glass cuts those strands, weakening it, and admitting water into
the glass matrix.
If you want a glossy smooth paintable surface, you add extra layers of pox
before it fully cures to build safe sanding thickness above the glass.
On the other hand, if all you are after is abrasion resistance, cut strands only
reduces the thickness of glass working for you. Well sanded & another 2-3
layers of pox applied over it to re-seal it will retain much of that property.
Remind us again - what's the boat?
regards
Alan
-
17th January 2012, 06:49 AM #5SENIOR MEMBER
- Join Date
- Aug 2008
- Location
- Birkdale
- Age
- 51
- Posts
- 279
Alan,
It's never too late. It's a SOT kayak. Jem Watercraft Sabalo. I'm in a constant weight versus strength argument. I want to keep the weight down as I will be transporting it on top of the 4x4, but I want to make sure it is strong enough to use in the surf. My gut feel is to put the extra epoxy on just to be confident that I've made it as strong as I can. I guess I have to weigh up the extra effort in man handling it, or the extra effort of taking it apart to fix something.
Cheers,
Chris
-
17th January 2012, 09:28 AM #6
Epoxy = weight rather than strength.
MIK has done the numbers &, from memory, thicker plywood comes out better in
strength vs. weight, rather than adding glass. Glass = strength on the outside
of the ply where it is needed, but more glass requires more epoxy = more weight.
I think he put the data up in his web-site.
If the boat was designed for flat water, & will cop a caning in surf, maybe
need to be thinking in terms of internal girder/s to maintain overall shape &
rigidity? If top & bottom can be crushed together, the boat will tear apart at
that point, glass or no glass.
cheers
AJ
Similar Threads
-
Techniques with glass/glass work etc.
By Ziapurple in forum Links to: INSPIRATIONAL WEB SITESReplies: 1Last Post: 30th March 2012, 04:25 AM -
Bar Strength
By rm5d in forum METALWORK FORUMReplies: 11Last Post: 22nd August 2011, 02:31 AM -
Attn MIK and PAR: Lightweight 'glass vs. heavier glass
By Rick_Tatum in forum BOAT BUILDING / REPAIRINGReplies: 17Last Post: 1st July 2009, 11:52 PM -
Lid Strength
By LineLefty in forum WOODWORK - GENERALReplies: 5Last Post: 22nd April 2005, 05:00 PM