Ozbow

Hi all,

Looking to change adhesives for backing wood bows. I've had some great success with Gorilla Glue, but also has some disappointing failures as well. I need something more reliable. I also need something that will cure to full hardness in 12 hours or less, no negotiation. I already use Titebond III on some projects that are not time-critical.

I've heard many people say they've never had a problem with Techniglue CA delaminating. Even on handle risers on all wood bows.

So I think I'll give it a try.

Before I do, what've your experiences been with it? I'd be especially keen to hear about your experiences of putting the bow into a heat box, and how soon the epoxy gets to full hardness...enough to get into tillering.

I've scoured the fora and found there to be a soft spot among a few of us for Smooth-On. How does the cost compare? How much difference is there, really between the two?

Cheers,

Dave

yeoman wrote:.......... also need something that will cure to full hardness in 12 hours or less, no negotiation......

I would suggest that you download the manufactures specification sheets.

yeoman wrote:...... How does the cost compare? How much difference is there, really between the two?

In my opinion not enough to worry about and in your situation what ever it costs for the right epoxy to do the job.

Using heat strips and Smooth-on I can glue up a bow after breakfast and work on it after lunch.

Heat strips will set you back about $300.00 per set and you will also need a step down transformer.

Daryl.

My only experience with Techniglue is my first kit "went off" after 6 months on the shelf in the shed. Unfortunately I never got to build a bow in that time. However I concede it is a very hot shed when the doors are shut. Keep it cool and at your usage rates it should never get old enough to "go off".

I did look at the data sheets, and it said 'solid-state cured' in 8 hours at 25 C, but I don't know if the adhesive keeps getting harder/stronger after that point.

If Smooth-On was measurably better/more reliable/easier to use and cost more, I wouldn't mind forking out for it. But if Techniglue CA is sufficient++, then I'll go with that. Happy to be convinced otherwise. If you can think of a reason I should use Smooth-On instead, I'd be glad to hear it.

The heat strips seem to be a very efficient means of curing the epoxy, and the reports of your progress seem very encouraging. But at $300 a set, and I would probably need five sets, it will have to be a long-term goal, with a well built heat box an expedient make-do in the meantime.

Rod, when I was trawling past posts about Techniglue I read your initial report on that. Unfortunate to hear. I think I've read of some people keeping their epoxy in the fridge. Or at least, in the beer fridge in the shed.

Dave,

IMO you can't go past Smooth-On. I have been using it for well over twenty years and wouldn't consider using anything else as it has proven to be super reliable. It has a long pot life and is easy to work with. If you have a heating box to cure the epoxy it will be fully hardened in six to eight hours and be able to work on the bows once they have fully cooled (glue the bows in the afternoon and work on them the next morning).

I have heard of some odd failures with Techniglue but others seem happy with it.

Regardless of cost I would use Smooth-On over Techniglue any day. I believe John McDonald now keeps it in stock.

Jeff

Like I said, I'm happy to be swayed. What temperature do I need to get this excellent curing time?

Is it Smooth-On that's purple?

I cure at 60 degrees Celsius for eight hours but I know five hours is enough.

yeoman wrote:s it Smooth-On that's purple?

No mate. It looks similar to Araldite and cures clear.

Jeff

Evening Dave,

I have used Techniglue on all of my bows and never had a problem with it. The glue I have is close to 12 months old now and its holding a 115lb warbow hickory backing on at the moment and doing fine!!

I cure my bows out in the sun under black plastic to get a bit of heat into the glue to help it dry, but I always leave the bows a full 24 hrs to cure before any bending happens. I use it because its easy for me to get and for 50 bucks a pot it is doing me fine at the moment.

Colin

I'd be having a chat with these folks -

https://plus.google.com/112690251041197 ... l=au&hl=en - Canberra Local

http://www.fibreglass-resin-sales.com.a ... xy-resins/ - Nationwide shipping

The national shipping mob have Techniglue in stock while the Canberra locals should have an Aradur based resin + thickening agent/glue available that, with the right tweaking, will meet your requirements. Personally, I've found that speaking to composites professionals who deal in glues & resin 24/7 will give you an insight into cheaper, more flexible & more specific products. I'm sure Techniglue & Smooth-On are great products, but I'm sure you can get the same chemical products at a cheaper price without the brand name, and at quantities that are more suited to you.

Having said that, I've not had a successful bow build in a while, but I've never had a delamination failure ever - only my own honest mistakes!

Edit: Re:hotboxes, I've just finished my own and will be posting on it soon - I used a fancy digital temperature controller and it was pretty cheap...

As a matter of fact, I've been into the local fibreglass place, though for a different purpose. I do remember they had Techniglue in stock though.

I've asked John (jcm) about Smooth-On. It'll be a close call between the adhesives, I think. Either way I need a heat box so will be looking forward to seeing your post.

On the courses we gluing staves at about 8-8.30 pm, and we start tillering at about 9 am the next morning. Having Smooth-On (and Techniglue I'm sure) cure within this time will be a massive boon.

When gluing wood, to you rough it up with 36 grit? 120? Toothing plane? Planed smooth? Previously I've sanded to anywhere from 36 to 80 grit, light scrape to get surface detritus off then acetone, moisten (for Gorilla Glue) then glue up. I pass the moistening for TBIII.

I glue up my staves as a square section then mark out and rough out the bow when its dry (24hrs) so Techniglue will be good enough to rough out and start tillering in that curing time without a problem if your doing it in the same manner.

I always rough up both glue surfaces to 40 grit paper and then clean the dust off with a dry rag before gluing. Then when gluing I apply the glue and when the pieces are laid together I "set" the glue surfaces by wiggling them a bit to ensure good glue contact and some squeeze out.

If you leave the pieces over sized when gluing you always get nice even glue lines I've found.

I have always glued them dry with Techni-glue...

I grind my gluing surfaces with 40 grit belts. I replaced Acetone with Methylated Spirits many years ago.

If it was me I would give your wood a little time in your hot box before glue up to remove and surface moisture, then wipe it down with either Acetone or Methylated Spirits and then do your glue up.

Jeff

Yeoman,

I've uploaded a post on my recently built hotbox - it's rough around the edges, much as with anything I do, but it works.

I've attached the spec sheets for the resin & hardener I use, if you are interested in investigating that avenue. To turn into a thick glue with gap-filling properties I mix with silica dust to achieve the desired thickness, or occasionally saw dust if I want a specific colouring. As I said before, I've no idea how this matches up with Smooth On or Techniglue, but it's used in aeronautics, boat building & motorsport, so I'd hesitantly say this is perhaps one of the strongest compounds commercially available. With proper curing (50-60 deg. C) it only takes a few hours to harden.

I would have to endorse all that Jeff has said about Smooth on. I must admit I have never used any alternative but when one has a 100% success rate with one product then obviously there is no need to change.

Alright. So I've asked John (jcm) for a quote. Where else can I get it reasonably quickly in Oz?

yeoman wrote:Alright. So I've asked John (jcm) for a quote. Where else can I get it reasonably quickly in Oz?

I don't think it is available anywhere else in Oz.

Jeff

Nezwin wrote:.....To turn into a thick glue with gap-filling properties I mix with silica dust to achieve the desired thickness......

"1. What exactly is silica?
Silica is another name for silicon oxides - the most prevalent type being SiO2. It can be found in nature in crystalline form (as quartz sand), and it is the most abundant component of the earth's crust. Amorphous silica, on the other hand, is industrially manufactured in a variety of forms - including silica gels, precipitated silica, fumed silica, and colloidal silica.

2. What exactly does "colloidal" mean, anyway?
A colloid is a stable dispersion of particles - particles that are small enough that gravity doesn't cause them to settle, but large enough not to pass through a membrane and allow other molecules and ions to pass freely. Particle sizes range from about 1 to 100 nm."

Dave, If you prepare your gluing surfaces correctly you will not require gap filling properties in your epoxy. Besides, how do various mix ratios affect the strength of the bond.

Daryl.

Evening All.

greybeard wrote:... Dave, If you prepare your gluing surfaces correctly you will not require gap filling properties in your epoxy. Besides, how do various mix ratios affect the strength of the bond.

With respect to Techniglue.

Techniglue is an ATL product - the same people who make WEST System products.

If you are considering using additives like Micro-Balloons, etc. it would be in the users best interest to read the large amount of material/guidelines available on use and application of the product.

http://www.atlcomposites.com.au/atl_composites2/

greybeard wrote:

Nezwin wrote:.....To turn into a thick glue with gap-filling properties I mix with silica dust to achieve the desired thickness......

"1. What exactly is silica?
Silica is another name for silicon oxides - the most prevalent type being SiO2. It can be found in nature in crystalline form (as quartz sand), and it is the most abundant component of the earth's crust. Amorphous silica, on the other hand, is industrially manufactured in a variety of forms - including silica gels, precipitated silica, fumed silica, and colloidal silica.

2. What exactly does "colloidal" mean, anyway?
A colloid is a stable dispersion of particles - particles that are small enough that gravity doesn't cause them to settle, but large enough not to pass through a membrane and allow other molecules and ions to pass freely. Particle sizes range from about 1 to 100 nm."

Dave, If you prepare your gluing surfaces correctly you will not require gap filling properties in your epoxy. Besides, how do various mix ratios affect the strength of the bond.

Daryl.

The resin without silica, or something similar, in it is like water & flows out from the gluing surfaces. For these particular compounds, a thickening agent is certainly needed, regardless of properly prepared surfaces. I'm not sure how Techniglue or Smooth On are thickened, but there would be an agent within them that gives them gap filling properties, whether at a micro level or higher, it's just a requirement. The silica is basically finely ground fibreglass dust - nasty to breath in, but it just acts as a thickening agent.

Re: glue to hardener ratios, this has a huge impact on the outcome of the glue strength. It's like making concrete with an abundance of water or with a dry mix, they'll have different properties in the final product. As I understand it, the more hardener that is used, the more brittle a bond becomes (for the compounds I'm using) but the faster it sets (nominally, temp. dependent) while less hardener creates a more flexible bond that takes longer to set. The same might hold true for most other epoxies, I'd imagine.

greybeard wrote:........require gap filling properties in your epoxy. Besides, how do various mix ratios affect the strength of the bond....

Nezwin wrote:....Re: glue to hardener ratios, this has a huge impact on the outcome of the glue strength.....

I was referring to the ratio of the silica/fibreglass dust to the resin and hardener.

Daryl.

greybeard wrote:

greybeard wrote:........require gap filling properties in your epoxy. Besides, how do various mix ratios affect the strength of the bond....

Nezwin wrote:....Re: glue to hardener ratios, this has a huge impact on the outcome of the glue strength.....

I was referring to the ratio of the silica/fibreglass dust to the resin and hardener.

Daryl.

I see! Apologies for the mix up. I'd hesitantly say that mixing silica dust would have little impact, of any at all. It's a very common practice in aeronautics where strength & testing is paramount. Mixing wood dust in would have an impact to a degree, but I'd never do this for a structural bond, only where I've made a mistake & have to bog it up (for instance, I can't quite get my splices at the riser quite right, so I find myself filling gaps most times). Best not to make the mistake in the first place, ofcourse, but it's all part of the learning curve!

Neil

So after having investigated Techniglue and looking into its availability, today I ordered a 1 pint kit of Smooth On. I should get it next week. Next weekend I'll try and pull a great box together and start experimenting.