Has anyone tried the following ratio mix?
When mixed 2A:1B by volume, EA-40 will achieve greater heat resistance and improved physical properties.
Binghams suggest a ratio of 1:1.
One question that comes to mind is the time frame required for the epoxy to cure at ambient or elevated temperatures.
http://www.smooth-on.com/Epoxy-Adhesive ... index.html
EA-40 Clear Epoxy is an unfilled low-viscosity epoxy adhesive that can be spread easily in thin films that are almost transparent after curing. Mix ratio is 1:1 by volume.
When mixed 2A:1B by volume, EA-40 will achieve greater heat resistance and improved physical properties.
EA-40 is versatile and can be used for many different assembly and repair applications ranging from electrical potting to jewellery assembly to repairing plumbing fixtures. Bow makers have come to know EA-40 as a tremendous laminating resin. EA-40 provides highly moisture resistant bonds meeting the performance requirements for Federal Specification MMM-A-188, Type III.
Daryl.
EA-40 Clear Epoxy Smooth-on
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EA-40 Clear Epoxy Smooth-on
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
Re: EA-40 Clear Epoxy Smooth-on
Hi Daryl
Reading the spec's it quotes the same cure and pot life time for a 1:1 and 2:1 ratio which does make sense to me. Part B appears to be the catalyst so I would expect everything to take longer.
More importantly for me is the photo of the comp' bow.
Reading the spec's it quotes the same cure and pot life time for a 1:1 and 2:1 ratio which does make sense to me. Part B appears to be the catalyst so I would expect everything to take longer.
More importantly for me is the photo of the comp' bow.
Grahame.
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Shoot a Selfbow, embrace Wood Arrows, discover Vintage, be a Trendsetter.
"Unfortunately, the equating of simplicity with truth doesn't often work in real life. It doesn't often work in science, either." Dr Len Fisher.
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Daryl,greybeard wrote: Has anyone tried the following ratio mix?
When mixed 2A:1B by volume, EA-40 will achieve greater heat resistance and improved physical properties.
I haven’t bothered trying it for a few of reasons; the first being I don’t know that it offers any advantages (see further comments later) for bow making.
Secondly, I corresponded with Smooth-On directly many years ago when I was selling my bows and using a lot of the product. I checked with them regarding the best way to use the EA-40 for bow making and told them my glue-up process (Mixing ratio by weight 100 Part A to 83 Part B and cured at 60 degrees celsius for eight hours). Their reply was that I would get excellent results using it in that manner.
I have been using this epoxy now for over twenty years and it has more then proven itself and in fact has astounded me with how good it really is. IMO it is exceptional for bow making and that is why I have no interest in changing to any other product.
Lastly, I have difficulty in understanding that the EA-40‘s better physical properties, when mixed 2A:1B, would really be of any benefit or even noticeable when used for bow making. I say this because these are figures given by Smooth-On in Spec Sheets I have. The figures in parentheses are those when the mix is 2A:1B. Perhaps our engineers on here can comment on these figures.
Tensile Strength, psi: 3,400 (1000)
Elongation @ Break: 1.0% (0.4%)
Modulus of Elasticity in Tension, psi: 190 M (160 M)
Modulus of Elasticity in Compression, psi: 140 M (180 M)
Compressive Yield Strength, psi: 8,100 (8,300)
Hardness: Barcol 935 Impressor, 66 (69)
The older spec sheets simply said the 2A:1B mix ratio was for better heat resistance.
I notice in their latest Tech specs, in the link you provided, it shows this: Mix Ratio: 1A : 1B by weight or volume. This is different to any previous specs I have seen. The mixing by weight (which I have always done) has been at a ratio of 100 of Part A to 83 of Part B because Part B is lighter by volume than Part A.greybeard wrote:Binghams suggest a ratio of 1:1.
I have always used the glueing process I mentioned above as I was told I would get a stronger bond than if I just let it cure at room temperature. Going by Smooth-on’s latest spec sheet they appear to be saying just that.greybeard wrote:One question that comes to mind is the time frame required for the epoxy to cure at ambient or elevated temperatures.
Anyway I hope you might get something useful from all my waffle.
Jeff
Re: EA-40 Clear Epoxy Smooth-on
Jeff,
Thank you for your reply.
I will try the ratio that you use on my next bow, hopefully in a week or two, finishing a recurve at the moment.
Daryl.
[Very happy with the heat strips and Smooth-on.]
Thank you for your reply.
I will try the ratio that you use on my next bow, hopefully in a week or two, finishing a recurve at the moment.
Daryl.
[Very happy with the heat strips and Smooth-on.]
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Daryl,
I just reread my post and saw I doubled everything up - that's what happens when you are busy and don't check what ya post. I fixed it now.
In the older spec sheets Smooth-On always mentioned mixing by weight as the preferred method but of course did say you could also mix at a ratio of 1:1 by volume.
Yeah, I think the heat strips would be excellent but I have just never got around to getting any.
Jeff
I just reread my post and saw I doubled everything up - that's what happens when you are busy and don't check what ya post. I fixed it now.
In the older spec sheets Smooth-On always mentioned mixing by weight as the preferred method but of course did say you could also mix at a ratio of 1:1 by volume.
Yeah, I think the heat strips would be excellent but I have just never got around to getting any.
Jeff
Re: EA-40 Clear Epoxy Smooth-on
Gidday Daryl and Jeff,
It seems the epoxy is useful over a broad range of mix ratios and so it would seem accurate measuring is not necessary. If it is good at 1:1 by volume and better at 2:1 by volume then it is probably also OK at 0.8:1 by volume as well. This is why Smooth-On can safely recommend mixing 1:1 by weight or volume. They know it won't cause problems, and gives the user freedom to do either.
According the the MSDS, Part A has SG of 1.17 ( 1.17 g/cc = 0.855 cc/g) and Part B has SG of 1.02 ( 1.02 g/cc = 0.980 cc/g). Note the specific gravity values are at 4C. There are a lot of numbers below but I have attempted to make the different mixes comparable.
Using the above SGs;
Jeff's mixing ratio of 100:83 (1.20:1) by weight is equivalent to 100:95 (1.05:1) by volume.
The recommended 1:1 by volume mix is equivalent to 100:87 (1.15:1) by weight.
The recommended 1:1 by weight mix is equivalent to 100:115 (0.87:1) by volume
The recommended 2:1 by volume mix is equivalent to 100:43 (2.29:1) by weight.
The 1:1 by weight makes the most economical and environmental sense to me, because there is no waste of one part or the other, providing both cans have the same weight of material. In the kit I bought both cans have 0.51 kg on the label, I will check when I get a new kit. Only time will tell if this is durable, but the manufacturer implies it is OK.
Jeff, The material properties list is very useful, thank you.
The material properties difference when increasing the ratio from 1:1 to 2:1 by volume is interesting. The tensile strength, tensile modulus and elongation at break decrease while the compressive strength, compressive modulus and hardness increase. I believe this implies the epoxy is becoming more brittle. In particular I am not keen on the large decrease in tensile strength and elongation at break. For a rectangular section the stress on the back is equal to the stress on the belly. The tensile strength (back) is less than half of the compressive strength (belly) at 1:1 and at 2:1 the tensile strength (back) is less than one eighth of the compressive strength (belly) and so would be more prone to de-lamination at the back of the bow.
The "better physical properties" gained by increasing the mixing ratio to 2:1 are undoubtedly useful in some situations, however in my opinion I would not waste the materials on trialling it in a bow making situation. I don't think the improved temperature resistance would be worth the risk.
I hope the garble above makes sense
. If you would like any clarification, please ask 
.
Cheers........ Rod
It seems the epoxy is useful over a broad range of mix ratios and so it would seem accurate measuring is not necessary. If it is good at 1:1 by volume and better at 2:1 by volume then it is probably also OK at 0.8:1 by volume as well. This is why Smooth-On can safely recommend mixing 1:1 by weight or volume. They know it won't cause problems, and gives the user freedom to do either.
According the the MSDS, Part A has SG of 1.17 ( 1.17 g/cc = 0.855 cc/g) and Part B has SG of 1.02 ( 1.02 g/cc = 0.980 cc/g). Note the specific gravity values are at 4C. There are a lot of numbers below but I have attempted to make the different mixes comparable.
Using the above SGs;
Jeff's mixing ratio of 100:83 (1.20:1) by weight is equivalent to 100:95 (1.05:1) by volume.
The recommended 1:1 by volume mix is equivalent to 100:87 (1.15:1) by weight.
The recommended 1:1 by weight mix is equivalent to 100:115 (0.87:1) by volume
The recommended 2:1 by volume mix is equivalent to 100:43 (2.29:1) by weight.
The 1:1 by weight makes the most economical and environmental sense to me, because there is no waste of one part or the other, providing both cans have the same weight of material. In the kit I bought both cans have 0.51 kg on the label, I will check when I get a new kit. Only time will tell if this is durable, but the manufacturer implies it is OK.
Jeff, The material properties list is very useful, thank you.
The material properties difference when increasing the ratio from 1:1 to 2:1 by volume is interesting. The tensile strength, tensile modulus and elongation at break decrease while the compressive strength, compressive modulus and hardness increase. I believe this implies the epoxy is becoming more brittle. In particular I am not keen on the large decrease in tensile strength and elongation at break. For a rectangular section the stress on the back is equal to the stress on the belly. The tensile strength (back) is less than half of the compressive strength (belly) at 1:1 and at 2:1 the tensile strength (back) is less than one eighth of the compressive strength (belly) and so would be more prone to de-lamination at the back of the bow.
The "better physical properties" gained by increasing the mixing ratio to 2:1 are undoubtedly useful in some situations, however in my opinion I would not waste the materials on trialling it in a bow making situation. I don't think the improved temperature resistance would be worth the risk.
I hope the garble above makes sense
. If you would like any clarification, please ask .Cheers........ Rod
Re: EA-40 Clear Epoxy Smooth-on
Gee Rod that is great reading and defines ones 'modus operandi' one would think.Thanks.
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Thanks Rod, I was hoping you or some others might chime in about the mix ratios and the figures I gave. My concerns with the 2A:1B mix were that the tensile strength was a lot less and to me it seemed by that mix making the epoxy harder and the elongation at break less, it meant the epoxy was more brittle so not advantageous for bow making. From what you have said it seems my thoughts were on the right track.
As I mentioned above, in Smooth-On's old spec sheets, they just said to use the 2A:1B mix ratio for better heat resistance and no mention of improved physical properties. The better heat resistance I took to mean in applications such as electrical or similar where the epoxy could be exposed to high temperatures.
Thanks once again for your input.
Jeff
As I mentioned above, in Smooth-On's old spec sheets, they just said to use the 2A:1B mix ratio for better heat resistance and no mention of improved physical properties. The better heat resistance I took to mean in applications such as electrical or similar where the epoxy could be exposed to high temperatures.
Thanks once again for your input.
Jeff
Re: EA-40 Clear Epoxy Smooth-on
Thanks Bob, yeah..... us gingerbeers likes dem numbas hey...... 
You're right on the money there Jeff. In addition I would have thought temperature resistance would be a good advantage as leaving a bow in a locked vehicle is scary in hot weather. My first recurve suffered from this so I am very cautious (it was an aged third hand Hoyt when it happened 30 odd years ago). If they had better temperature resistance you could leave it behind the seat in the old Tojo, ready fore action. The high temperature resistance would certainly be an advantage for potting electrical/electronic gizmos.
While we are on the subject, could you fellas tell me how much smooth-on you mix up for a full 72" layup please. I mix 85 g of each component and I usually have very little to throw out. I started with this amount because it would yield 6 bows from a kit, however as soon as you start doing accents etc. you lose a fair bit. I reckon I'd get maybe 4 bows/kit.
Cheers......... Rod
You're right on the money there Jeff. In addition I would have thought temperature resistance would be a good advantage as leaving a bow in a locked vehicle is scary in hot weather. My first recurve suffered from this so I am very cautious (it was an aged third hand Hoyt when it happened 30 odd years ago). If they had better temperature resistance you could leave it behind the seat in the old Tojo, ready fore action. The high temperature resistance would certainly be an advantage for potting electrical/electronic gizmos.
While we are on the subject, could you fellas tell me how much smooth-on you mix up for a full 72" layup please. I mix 85 g of each component and I usually have very little to throw out. I started with this amount because it would yield 6 bows from a kit, however as soon as you start doing accents etc. you lose a fair bit. I reckon I'd get maybe 4 bows/kit.
Cheers......... Rod
Re: EA-40 Clear Epoxy Smooth-on
Hi Rod,
I use the little single serve jam containers that motels supply with breakfast.
For the typical longbow using three laminations in the core and mixing equal parts I use four measures in total. Usually there is a little bit left over which is better than having to mix up more if you run short.
Daryl.
I use the little single serve jam containers that motels supply with breakfast.
For the typical longbow using three laminations in the core and mixing equal parts I use four measures in total. Usually there is a little bit left over which is better than having to mix up more if you run short.
Daryl.
"And you must not stick for a groat or twelvepence more than another man would give, if it be a good bow.
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
For a good bow twice paid for, is better than an ill bow once broken. [Ascham]
“If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” [Einstein]
I am old enough to make my own decisions....Just not young enough to remember what I decided!....
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Rod,
For a four lamination longbow (4 wood lams and two strips of glass) I use 70 grams of Part A and 58 grams of Part B. I always have some left over glue as I don't like to be scraping out the container at all.
I will caution to mix the glue in a container - I use round butter containers. I had a mate once (I won't give his username ) that I gave more than enough Smooth-On to glue up a bow and he ran out with the belly lam and glass still to go. He mixed up some 24hr Araldite to finish the job. 
Anyway he didn't believe I gave him enough glue for the job and I said there was plenty. It turns out he just mixed the glue up on a piece of cardboard and it spread out or soaked into the cardboard or whatever and he ran out. He later used the same amount of glue mixed in a butter container and he had some left over. I have never let him forget about that either.
Jeff
For a four lamination longbow (4 wood lams and two strips of glass) I use 70 grams of Part A and 58 grams of Part B. I always have some left over glue as I don't like to be scraping out the container at all.
I will caution to mix the glue in a container - I use round butter containers. I had a mate once (I won't give his username
) that I gave more than enough Smooth-On to glue up a bow and he ran out with the belly lam and glass still to go. He mixed up some 24hr Araldite to finish the job. Anyway he didn't believe I gave him enough glue for the job and I said there was plenty. It turns out he just mixed the glue up on a piece of cardboard and it spread out or soaked into the cardboard or whatever and he ran out. He later used the same amount of glue mixed in a butter container and he had some left over. I have never let him forget about that either. Jeff
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Re: EA-40 Clear Epoxy Smooth-on
and dont forget to stir it for 3 minutes hey Jeff 
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Oh yeah, I forgot that bit but you know what; in their latest tech sheet in the link Daryl posted up, I found this little gem:LB rod 55 wrote:and dont forget to stir it for 3 minutes hey Jeff
After dispensing required amount of Parts A and B into mixing container, mix thoroughly for 3 minutes making sure that you scrape the sides and bottom of the mixing container several times.
Well Grasshopper what can I say?
Jeff
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Re: EA-40 Clear Epoxy Smooth-on
Looks like Rod has reached the plain of enlightenment the apprentice chipping the master eh............
I would surely run out of glue and have to mix up a second batch if I used Jeff's measurements. Daryl, I would be very nervous starting with that much. To be honest I was worried I may be too lousy in places, but I do get a lot squeezing out. I came across some plastic picnic plates that don't have a groove or step in the bottom to deal with. A few bucks for a pack of 20 seemed good to me. I mix and spread using an old bank keycard and I reckon I probably get more over the edges than goes on the gluing face. With more care and practice I am sure I can reduce the amount required. At this stage I would much prefer to get to the end of the glue up without having to mix a second batch.
Thanks for the advice fellas. Cheers...... Rod
the apprentice chipping the master eh............ I would surely run out of glue and have to mix up a second batch if I used Jeff's measurements. Daryl, I would be very nervous starting with that much. To be honest I was worried I may be too lousy in places, but I do get a lot squeezing out. I came across some plastic picnic plates that don't have a groove or step in the bottom to deal with. A few bucks for a pack of 20 seemed good to me. I mix and spread using an old bank keycard and I reckon I probably get more over the edges than goes on the gluing face. With more care and practice I am sure I can reduce the amount required. At this stage I would much prefer to get to the end of the glue up without having to mix a second batch.
Thanks for the advice fellas. Cheers...... Rod
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Well not really Rod; it's a bit of an in house joke between LB and I with LB really laughing at my working methods but that quote from the Smooth-On tech sheet just showed how how smart I was.rodlonq wrote:Looks like Rod has reached the plain of enlightenment the apprentice chipping the master eh............
I just use a piece of bow glass about 200mm long and about 12mm wide as a spatular. When applying the glue I angle it one way and then the other like a grader blade so more glue stays on the gluing surfaces.rodlonq wrote:I mix and spread using an old bank keycard and I reckon I probably get more over the edges than goes on the gluing face.
I use 1.5" wide lams and glass by the way.
Jeff
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Jayson Inglis
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Re: EA-40 Clear Epoxy Smooth-on
Gents,
Is there anywhere you can buy it in Australia/Queensland.
Cheers.
Is there anywhere you can buy it in Australia/Queensland.
Cheers.
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Stickbow Hunter
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Re: EA-40 Clear Epoxy Smooth-on
Not that I know of but John (jcm) can get it for you when he is doing an order from overseas. So, if you aren't in a hurry send him a PM.Jayson Inglis wrote:Is there anywhere you can buy it in Australia/Queensland.
Jeff