Falcate Bracing - Glues/Resin clarification

[colin north]

Thought it better to start another thread for clarity.

Trevor, I'm a bit mixed up.
On going back to your books, you seem to use the words resin and glue interchangeably, but talk mostly about resin.
To me glue is Araldite (for example) and Resin is used for making composites, ie bonding CF/glassfibre.
(Glue - thick, Resin - a bit runny, better wetting/ penetration, but basically the same stuff, I think)

This may be due to my unfamiliarity with West Systems products in Australia (Techniglue for example seeming to be being specific to there) and their use generally, for guitar construction at least.

Sorry to seem a bit "thixotropic", but just to be clear, I thought glue was talked about for the headblock area, and resin used for bracing and CF layup (brace laminations, rovings under and over braces, plus braceplate/bridge laminating cloth)

Is this the case, or do you use the Techniglue for everything?
If not, which/where?

If this is the case, one product I found was this http://www.easycomposites.co.uk/product ... esive.aspx
Seems a good system - no manual mixing so fast to start application, was just a bit hesitant to click the "buy" button because of the quote "slight amount of flexibility making it ideally suited to applications where the bond will be subjected to vibration or shock" part of the blurb - although it also says "is still very much a rigid adhesive, albeit with a high flexural strength and a small amount flex"

[colin north]

Won't let me edit my own post now! time out.

To continue,
I realise you cannot recommend something you have no experience of, but should I be concerned this small amount of flexibility (in the aforementioned glue) may significantly affect vibration transfer/increase damping effect, or on balance be glad that it will stand up better to vibration and shock considering the dharma of guitars?

[colin north]

Apologies - ended up 2 questions in same thread!!

[Trevor Gore]

Hi Colin,

I guess when I use resin as a glue it could get confusing.....

First, a couple of definitions just to get everyone on the same page: resin is the clear liquid that gets mixed with a liquid hardener, usually an amber colour, and typically is used for laminating or surface coating. When surface coating (i.e. "painting") typically a different hardener is used.

Glue is the resin with additives, typically thickeners/extenders of various types, so that it works better as a glue and will gap-fill without running out of the joint. That's what makes the thixotropic properties of Techniglue so handy. These are basically the same meanings as your "runny" vs. "thick" definition

BTW Techniglue is sold as a "structural epoxy adhesive" so a search on that might yield an equivalent product. Hard to believe that something similar is not available in the UK. Maybe try Gurit.com (they took over SP Resins, the UK equivalent of WEST and started originally by a Uni mate of mine).

I use Techniglue installing the head and tail blocks and laminating the braces and that's about it. I have used it installing laminated linings, just to get the longer open joint time whilst I get everything lined up and clamped. When it's 35C here, Titebond is a bit fast!

All the CF work on the soundboard is done with resin (and I might have used the term "glued down" rather than "resined down"). If you use "glue", with its extra viscosity, it will carry out the CF with the squeeze-out as you clamp. So again, pretty much as you said.

I've tended to avoid fast epoxies like the plague as the ones I've tried have been very low strength/adhesion. There's a vast number of epoxies out there and some of them (casting resins, potting resins) are useless as glues. Some are so brittle they fail at the first knock, others have zero stick. When in the UK I used SP Resins, here in Aus. I use WEST and Techniglue. I don't trust anything else. So your 15min epoxy gets a tick for being "flexible" but a cross for being fast.

The SP (Gurit) stuff is available from here (I hope it's the same as it used to be!):

http://marinestore.co.uk/sp-systems-epoxy.html

The thixotropic properties might (repeat might!) be due to adding colloidal silica. If you talk with the tech. people at Gurit they might be able to point you in the right direction. If they are good enough to tell you how to make a thixotropic mix, be sure to let us all know!

[colin north]

Thanks Trevor, that makes things clear.

I've looked at structural epoxy adhesives already, but was really looking for a West Systems because of your recommendation.

Not contacted Gurit.com (yet), probably a trade secret, but---

From an initial look, http://marinestore.co.uk/MI655-K.html seems like it may be similar to Techniglue from West Sytems stuff?
Seems like it's a thickened version of their 650-8 G/flex adhesive http://marinestore.co.uk/MI650-8.html (which itself may be useable for laminating bracing, etc) - 45 minutes open time according to the West website information.

[colin north]

Thanks for the link by the way - their prices seems good compared to other places.

[Trevor Gore]

After my last post I found this:

http://marinestore.co.uk/HA1487.html

I might have been on to something regarding thixotropic properties...

Also available from WEST:

http://www.westsystem.com/ss/406-colloidal-silica/

If I didn't have Techniglue, I'd be inclined to go with the 105 system and the colloidal silica. We all know it sticks, so its just about getting the viscosity/thixotropy right.

[colin north]

Thanks for taking the time and trouble Trevor.
From the West website's guide to choosing the right filler for the application it seems Colloidal Silica ticks most of the boxes best.
I've already got a West 105 pack to play with so 406 Colloidal Silica would seem the way to go to ensure keeping things compatible.
No worries, I've just got to chose a "flavour" - katsup, mayonnaise or peanut butter!! http://www.westsystem.com/ss/filler-buying-guide/

[Trevor Gore]

Techniglue would be between mayonnaise and peanut butter! Hmmm, now there's an idea for lunch. Should go well on top of the thinly sliced Mars bar....

[Dominic]

Hi trevor, not a glue question but it has to do with Falcate bracing so I thought I would put it in here.

I have not seen anywhere in the books where you mention shaping the bottom of falcate braces to match to radius of the dish. But I assume you do this. I can envisage a holding jig to make it easier to sand in the profile onto the bent braces. Do you shape them or are they just pressed into the dish?

Cheers
Dom

[Trevor Gore]

I just press the curved braces into the dish.

The problem I found with trying to sand in a profile onto curved braces is that a) it is difficult to get a good profile and b) it is easy to get the bottom of the brace out of square, so when you go-bar down the braces they have a tendency to roll. All-in-all, I was getting a better glue line by leaving them flat.

Straight braces I profile.

I radius all the back braces, though. They're a much higher curvature.

[colin north]

That saved me asking the same question, thank you gentlemen!

[ozwood]

Hi Trevor,

This

All the CF work on the soundboard is done with resin (and I might have used the term "glued down" rather than "resined down"). If you use "glue", with its extra viscosity, it will carry out the CF with the squeeze-out as you clamp. So again, pretty much as you said.

brings up a Point that has often concerned me when Glueing down the Falcate braces with just resin , I'm Worried that the spruce/ KB braces are thirsty for resin , the CF towe is thirsty for resin I worry that the Joint will become dry and that a Brace may become loose, on the last few builds I have used a Mixture of techniglue and West Sytem resin to avoid too dryer a joint , what are your thoughts and experiance ? is my concern misplaced ?

Cheers,

[Trevor Gore]

If you make a joint with resin as I suggest in the book (say spruce to spruce or spruce to king billy) then take the joint apart before it sets up, the joint always looks amazingly dry. But if you use Titebond on a spruce to spruce joint, clamp it up, then dismantle it (you have to be quick!!) you also see an amazingly dry joint. So far, I've never had a failure with either glue when used properly. The Titebond people reckon it's impossible to get a starved joint with Titebond. I can't say I can verify that or not. I have had starved joints with Techniglue caused by gluing up, clamping, loosening to adjust and re-clamping. If you have close fitting joints then have to adjust the positioning after clamping I would recommend re-doing the joint. Takes another 30 seconds to save hours of potential trouble down the track.

So when gluing down falcates, make sure all contacting surfaces look wet (but not running) when you put the surfaces together, clamp once and you should be right. I'd be saying you're better off without the Techniglue. I'd be hoping your joints are close fitting enough not to have to use Techniglue to fill the gaps!

[MBP]

Hi all,

I have used quite a bit of epoxy for gluing and finishing wood before.

You should never mix two different brands together, add thinners or change the mix rate.

Too much clamping pressure is an issue as well. An even clamp is best.

Before adding fillers mix the epoxy up completely. I wouldnt be adding much fillers for this. Your not supposed to mix like mad so bubbles form.- In saying that I have never had an issue with bubbles affecting the bond.

206 gives more working time and is stronger than 205. 207 is used for finishing.
105 is the resin.

What type of carbon fibre are you's using?

[Trevor Gore]

Ro,

viewtopic.php?f=33&t=3624#p43715

[MBP]

Thanks.

FGI make (or distribute not sure) resin as well. I cant remember exactly what it is called but I have found it to be better than Wests.
I will check the drums tomorrow.

[ozwood]

Thanks for the Clarification Trevor,

It was more of a perceived issue on my part than a problem that had occurred , So I'll take that onboard for my next build.

Cheers,

Paul.

[Kerplunk]

FGI make (or distribute not sure) resin as well. I cant remember exactly what it is called but I have found it to be better than Wests.

Interesting.....

I've used an epoxy (R180 with the H180 hardener) from the "ES 180 System" that I bought from FGI.....

.... and it failed (delaminated) after only 5 minutes of use (after having had over 2 weeks to reach it's fully cured state).

Mind you, it may have been my own fault; this was my first time laminating (I was laminating together 6 layers of thin plywood) and it took a lot longer to do than I'd expected. As a result I was really rushing towards the end to finish up before the mix I'd made "went off"/gelled and I'm not sure I succeeded in that; it was hard to "wet-out" the final couple of plywood layers with the last bit of that mix, and I reckon the mix may have gelled a bit too much to really seep into/attach to the wood.

End result: delam.

Had a look at the FGI site: the epoxies seem to have disappeared from being listed under the Products tab - are they not selling it anymore?

Under the "Literature" tab, "FGI Product Catalogue" link I did find a link to "FGI Epoxy Resins" though, and the "ES 180 System" is listed in there: http://www.fgi.com.au/files/images/stor ... Resins.pdf

So maybe they still sell it?

From memory I think the FGI stuff was cheaper than the West Systems stuff I've since bought, and I know someone else who used the same FGI epoxy I did for the same purpose, and has never had it fail on them (only heard this after I'd splurged on the West Systems stuff - D'OH!).

So perhaps the FGI stuff is a better (i.e. in terms of same bang for less bucks) option after all?

Cheers,
Al.