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Main Boards => The Bowyer's Bench => Topic started by: Lee Lobbestael on July 19, 2017, 05:11:00 AM

Title: Smooth on ratios
Post by: Lee Lobbestael on July 19, 2017, 05:11:00 AM
There seems to be a discrepancy concerning the ratio of part A to part B with smooth on. The cans I have had all say to mix at a ratio of 70:30 A to B by volume I believe. Most people I have talked to mix it 50:50 by volume but some said they mix it by weight and some said they use a different ratio. Whats the deal with this?
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 19, 2017, 05:27:00 AM
This is right out of the horses mouth
  web page (https://www.smooth-on.com/tb/files/EA40.pdf)
Title: Re: Smooth on ratios
Post by: macbow on July 19, 2017, 08:55:00 AM
Mix ratio is 1:1 by volume. When mixed 2A:1B by volume, EA-40® will achieve greater heat resistance and improved physical properties.. "from web page"
So does anyone use the 2A : 1B  I use the equal by volume on my wood laminate bows.
Title: Re: Smooth on ratios
Post by: Al Dean on July 19, 2017, 09:36:00 AM
I mix 1-1, but am not critical about it.  Close is completely good enough.
Title: Re: Smooth on ratios
Post by: Shredd on July 19, 2017, 02:20:00 PM
As a rule of thumb I always use a little more A than B...  If I use 40 grams of A I will use 35 grams of B...  That way I am always on the good side of things and there is less waste in the end...
   In your standard epoxies if you don't mix them exact it could have problems reaching it's full potential...  It's kinda like having more bolts than there are nuts for a project... If you have 10 holes, 10 bolts and only 7 nuts only 7 bolts will do the holding... Only the bolts with nuts will hold...
   So that is why I err to the good side...
Title: Re: Smooth on ratios
Post by: bigbob2 on July 19, 2017, 09:13:00 PM
for a 4 lam longbow, and I know this weight is in grams, not ounces but I use 72 g of A to 58 G of B. Works very well.
Title: Re: Smooth on ratios
Post by: jsweka on July 19, 2017, 09:44:00 PM
Quote
Originally posted by Al Dean:
I mix 1-1, but am not critical about it.  Close is completely good enough.
Yup!  One dixie cup of each part is how I do it and never had a problem.
Title: Re: Smooth on ratios
Post by: bamboo on July 20, 2017, 06:13:00 AM
2a--1b here---clearly harder--more peel resistance
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 20, 2017, 10:08:00 AM
I would tend to agree with you. Do we know anyone who sells it for the 2 to 1 mix?
Title: Re: Smooth on ratios
Post by: monterey on July 20, 2017, 10:52:00 AM
I do 1:1 by volume and it seems to work fine.

Which one is A and which B?
Title: Re: Smooth on ratios
Post by: JamesV on July 20, 2017, 11:06:00 AM
where can I buy half a can of B??????????
Title: Re: Smooth on ratios
Post by: kennym on July 20, 2017, 12:43:00 PM
I can get quarts of  A only if you guys want it , then with a  quart kit and the extra quart  of A you are good to go .

Sorry , can't get pints of A only.
Title: Re: Smooth on ratios
Post by: Robertfishes on July 20, 2017, 12:47:00 PM
Monterey, the cans are marked A or B. I mix 1:1 but I usually add a little extra part A. I always have about 8 oz in the B (blue quart) can when the A (yellow quart) can is empty.
Title: Re: Smooth on ratios
Post by: kennym on July 20, 2017, 12:52:00 PM
Part A is yellow can.

If you use too much hardener, it won't set up properly.

 So said a fellow who did to set it faster and called Smooth-on to ask. (not me this time but a customer who thought he got some bad glue.)
Title: Re: Smooth on ratios
Post by: kennym on July 20, 2017, 04:55:00 PM
Oops , dbl post
Title: Re: Smooth on ratios
Post by: Crittergetter on July 20, 2017, 05:30:00 PM
I've often wondered exactly what physical properties are supposed to be improved by mixing 2a to 1b. If it sits up harder is that necessarily a good thing for how a limb bends?
Title: Re: Smooth on ratios
Post by: mwosborn on July 20, 2017, 06:16:00 PM
Quote
Originally posted by Crittergetter:
I've often wondered exactly what physical properties are supposed to be improved by mixing 2a to 1b. If it sits up harder is that necessarily a good thing for how a limb bends?
This is from their literature:

Heat Distortion Temperature:
At 1A:1B Mix Ratio*: 163°F (73°C)
At 2A:1B Mix Ratio*: 217° F (103 °C)
Title: Re: Smooth on ratios
Post by: Crittergetter on July 20, 2017, 06:50:00 PM
Yes sir, I've read that before. I am just wondering if any other properties are affected. Flexibility, longevity, ect.....
Title: Re: Smooth on ratios
Post by: monterey on July 20, 2017, 07:01:00 PM
Is there any difference in the pot life with the various ratios?
Title: Re: Smooth on ratios
Post by: bamboo on July 20, 2017, 07:02:00 PM
one I found is peel resistance---

you would be amazed how easily you can peel the glass from a limb
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 20, 2017, 07:51:00 PM
There are a few bowyers that have done test strips with both mixes just to see
. the 2-1 mix showed tearing of wood and not peeling was much better. I think another key thing is letting the glue cure at room temp or at least not putting it in the hotbox too quick. So all the air has a chance to work out before curing starts.
Title: Re: Smooth on ratios
Post by: kennym on July 20, 2017, 08:01:00 PM
One of the walk the talk bowyers told me he quit having problems with air bubbles when he went to the 2/1 mix. I haven't tried that mix but I may soon .
Title: Re: Smooth on ratios
Post by: Bvas on July 21, 2017, 07:37:00 AM
If all the properties are better at 2:1...........then why do they even sell it at 1:1? Is the A side the more expensive part?
Title: Re: Smooth on ratios
Post by: Crittergetter on July 21, 2017, 08:13:00 AM
Hummm... I like the sound of better peel resistance!! I'll give this a try on the next set of limbs I make for myself!!
Title: Re: Smooth on ratios
Post by: kennym on July 21, 2017, 12:34:00 PM
The A costs a bit more, I'd have to check but seems like about 3 bucks a quart. I've wondered why 1/1 is sold if 2/1 works better also Brad..  maybe bow application isn't the big useage of it ?

Also wonder why not sold separate in pints , only think I can figure is most guys that build lots of bows buy quarts or bigger.?
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 21, 2017, 01:17:00 PM
Ok I always use a bit more resin just because. Had very few problems. Those that did I have to say peeled pretty easy. I know a lot of the high end guys that go 1-1 and are happy with it. So I guess it is what you want to do. Piece of mind type of thing.
Title: Re: Smooth on ratios
Post by: bamboo on July 21, 2017, 08:00:00 PM
54* MORE temp protection is enough of a reason for me--the peel resistance is frosting on the cake

 its not any different that 1:1 in the handling dept--I just order 2 A's and mix accordingly---

I use a 24grit belt to clean up a blank--the hardened snots are noticeably tougher--

if its harder for me to peel using a putty knife--its harder for it to delaminate on its own
Title: Re: Smooth on ratios
Post by: kennym on July 22, 2017, 04:25:00 PM
I just glued up a limb for a TD, and went with 2/1.

See my gloom thread.....  :saywhat:
Title: Re: Smooth on ratios
Post by: bamboo on July 23, 2017, 08:03:00 AM
2-1 blew up --or the replacements are 2-1 ?
Title: Re: Smooth on ratios
Post by: kennym on July 23, 2017, 10:28:00 AM
1/1 blew up but I think I skimped too much on glue....
Title: Re: Smooth on ratios
Post by: bamboo on July 23, 2017, 05:14:00 PM
I glued one today--after your post--I poured the 2-1 right to it!
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 24, 2017, 10:07:00 AM
There is a suggestion section on the EA 40 web page that shows using a three step cure 2hrs. at 120-150-185. Then if you go 2-1 mix cure at room temp overnite the heat to 217 still under pressure. for those who use 2-1 mix do you do it that way?
Title: Re: Smooth on ratios
Post by: bamboo on July 25, 2017, 06:23:00 AM
my box ramps up very close to that schedule--

IMO 217* seems high for riser woods [very near boiling!]--- beneficial for the epoxy -but.......

that process might be good w/TD limbs --not as much wood to worry about---then use a gentler bake on riser wood
Title: Re: Smooth on ratios
Post by: T Folts on July 25, 2017, 07:23:00 AM
I do the 2:1 ratio and still heat it. I heat to 165 +- for 4 hrs.
Title: Re: Smooth on ratios
Post by: Crooked Stic on July 25, 2017, 08:31:00 AM
Ok Kenny here is you some glue squeeze out.    :D
   (http://i.imgur.com/kLQ5L1L.jpg)
Title: Re: Smooth on ratios
Post by: kennym on July 25, 2017, 12:42:00 PM
Waaay better'n this!!

 (http://i.imgur.com/xTDRTCV.jpg)
Title: Re: Smooth on ratios
Post by: T Folts on July 26, 2017, 07:27:00 AM
I started with the 1:1 ratio and never had a failure. I always use extra with plenty of squeeze out. I have had a few limbs show spots of starvation but I believe it is related to dry spots so I am more careful now to get enough on and even spread. I have read a lot on the 1:1 ratio and 2:1 ratio and with suggestion from a (pro) after some proto type work of the two ratio's I was convinced the 2:1 is far superior for laminated bow limbs. The bow limbs were heated and pulled hot without failure, where the 1:1 ratio failed. Enough for me to be convinced. I work in a R&D environment and use a scale for everything, no guessing. I suggest you invest in a gram scale and measure for accuracy.
My .02
T
Title: Re: Smooth on ratios
Post by: bigbob2 on July 27, 2017, 09:21:00 PM
I use the ratio as stated before for 4 lam longbow = 72 g Part A to 58 G part B, and have in hot bow at 160 C for 8 hours, then left to cool overnight. Works for me
Title: Re: Smooth on ratios
Post by: kennym on July 27, 2017, 09:24:00 PM
Quote
Originally posted by bigbob2:
I use the ratio as stated before for 4 lam longbow = 72 g Part A to 58 G part B, and have in hot bow at 160 C for 8 hours, then left to cool overnight. Works for me
Bob, that is 320F that's hot!!
Title: Re: Smooth on ratios
Post by: Roy from Pa on July 28, 2017, 04:37:00 PM
Ya maken charcoal Bobby boy?   :)
Title: Re: Smooth on ratios
Post by: green valley gobbler on March 06, 2019, 07:15:23 AM
Just wondering if any one has any updates on smooth on ratios? Anyone using the 2 to 1 ratio and feel it provides a better bond?
Title: Re: Smooth on ratios
Post by: Roy from Pa on March 06, 2019, 07:30:55 AM
Mix ratio is 1:1 by volume. When mixed 2A:1B by volume, EA-40® will achieve greater heat resistance and improved physical properties..

I've used the 1 to 1 for years and never had any problems.

The 2 to 1 is just to improve heat resistance and strength.

Either one works fine.
Title: Re: Smooth on ratios
Post by: skeaterbait on March 06, 2019, 08:38:09 AM
2:1 will attain a higher heat distortion but realistically how many bows are going to get over 163° (after the build) let alone make it to 217°. And on top of that, how many home built easy bake ovens will reach a cook temp of 250°?


Title: Re: Smooth on ratios
Post by: Flem on March 06, 2019, 10:08:53 AM
I use EA-40 as a gel coat, 2-1. In theory it should be harder at that ratio. Cant prove it, though.
Title: Re: Smooth on ratios
Post by: kennym on March 06, 2019, 05:10:03 PM
2:1 will attain a higher heat distortion but realistically how many bows are going to get over 163° (after the build) let alone make it to 217°. And on top of that, how many home built easy bake ovens will reach a cook temp of 250°?



You can if you cover the thermostat with foil.... Don't even ask!!
Title: Re: Smooth on ratios
Post by: Roy from Pa on March 06, 2019, 05:13:41 PM
OMG, I gotta ask.

Come on dude, what happened then?

LOL

Did something smoke?

 :campfire: :campfire: :campfire: :campfire: :campfire: :campfire:
Title: Re: Smooth on ratios
Post by: kennym on March 06, 2019, 05:35:31 PM
Hot nuff the glass turned white .... junk bow

I don’t even know why we did that either but never again!! Long time ago ...

Before internet when you hadda try something cause you couldn’t google it...
Title: Re: Smooth on ratios
Post by: Crittergetter on March 06, 2019, 09:09:10 PM
Hey guys, I did a couple of bows last summer and tested the peel resistance. It did seem to have a better bond than 1-1. I also noticed that for me it seems that uls bonds better than ul. Not sure why but it does seem to bond slightly better.  :dunno:
Anyways, I have adopted this as standard procedure simply because of the increased peel and heat resistance. I’ve done approximately 20 Bows this way and have no complaints, although I didn’t have any complaints before either.
A little more glue is worth a little more piece of mind I guess. Lol