Heat curing epoxy...

[Mad Max]

Thanks Shredd

[Kirkll]

OK Mark..... If a microwave is just stimulating the molecules and thinning it down, why couldn't we use this to thin it down and just pour it into the caulking tubes ?   

I don't see why not. Warn is warm for the most part with epoxies, I have used a double boiler to heat epoxy that had sat too long and developed crystals in the liquid. Heating and letting it cool slowly redissolves the crystals back into solution.

So I weighted  up some epoxy, I used some restaurant cups like for extra  jalapeno peppers or extra salad dressing and filled them level to the top.
Part A = 71 grams
Part B = 59 grams
I think 71 grams A and 29.5 grams of B will do 1 Recurve with Veneers and lams.

Since we're on the subject of mixing ratios and the like, what do you guys find for pot life and room temp cure time when you reduce part B to 1/2 of A?


Mark

I haven't used a 2:1 volume ratio since i first started messing with this stuff  about 15 years ago, but i really cant remember the actual pot life being a problem. I do remember it being a pretty sticky booger compared to 5:4 i ended up going with.

I use 9 oz paper cups to mix in with no wax in the cups... I tried plastic cups once and they didn't like the microwave much at all.... What a mess that was.  

I don't really measure anything. I just take a big scoop of the resin with a 1.5" piece of glass , and a smaller scoop of the hardener. I usually mix about 4-5 ounces for a limb lay up which is about half of the 9 oz cup, and i mix it for a good minute or so using a paddle bit in a drill. I think mixing time is a big deal with epoxy... The stuff stays pretty smooth for about 10 minutes which is plenty of time for a limb.... after about 15 minutes it starts kicking off and gets harder to spread evenly. I've used left over stuff in the cup for other things.  Mostly filling cracks in my wood floor in the shop. After 20 minutes it's pretty much unusable.

When doing a one piece bow i mix a bit more in the cup. say 5-6 oz... then mix a second cup when it runs out. It's a lot more user friendly than west systems as far as kick off time goes. That west systems is a hot tamale! You gotta move quickly using that stuff.     Kirk

[EvilDogBeast]

I've only made a handful of bows but I have been using 2:1 (about to quit after seeing the wasted B and the fact smarter folks than I are using 5:4).  Pot life for me is about 2 hours in a shop that sits in the 68°F - 70°F range, BUT... that is because I don't heat it before mixing AND I transfer from the cup to a 2" paint roller tray.  I also use the 2" foam roller to spread the EA-40 on the lams which seriously reduces the amount of adhesive I use.  I have been mixing 2 oz A to 1 oz B (3 oz total) and ending with about .5 oz left over to re-butter anything I missed or messed up on a 60" one-piece longbow (glass, veneer, taper, taper, riser, parallel, veneer, glass).

I mix my parts in those graduated cups the epoxy river table nerds use, with a plastic tongue depressor.  The plastic sticks can be wiped off after use with denatured alcohol and reused.  West Systems makes some nice shaped ones and a pack of them will last you a long time if you don't abuse them (use something else to open your EA-40 cans).

[mmattockx]

Pot life for me is about 2 hours in a shop that sits in the 68°F - 70°F range

My workspace is in that same range, maybe even cooler, so I will have no issues at all with pot life.

I transfer from the cup to a 2" paint roller tray.  I also use the 2" foam roller to spread the EA-40 on the lams which seriously reduces the amount of adhesive I use.

Foam roller like this?

https://www.amazon.ca/Roller-Mister-Density-Perfect-Painting/dp/B09PTWLSX2/ref=sr_1_8?crid=ZMN8LN00GINH&keywords=2%22+paint+roller&qid=1654008691&sprefix=2+paint+rolle%2Caps%2C205&sr=8-8


Mark

[EvilDogBeast]

Yes that kind works well.  I use this specific, crappier version

https://www.lowes.com/pd/WHIZZ-2-in-Foam-Roller-3-Piece-Mini-Paint-Applicator-Kit/3013611

[Crooked Stic]

Those foam rollers work great. Used them myself for awhile. Seems I was all the time needing to go pick some up. That got old pretty quick. What I have now is two cheap metal putty knives one for A one for B. Mix with a stick (same stick) just wipe it off every time. Mix in a paper bowl dab it on the lam with mix stick and spread with one of the cheap putty knives.
Keep it simple 

[Kirkll]

Max..... Are you saying to stab the butt end of the caulking tube into the can?       Man you gotta take a video of that procedure. I got a feeling it's going to be entertaining.

You would have to cut a 1/4" off the tip to let the air out, STAB slowly

We guys.... I got my empty caulking tubes and they filled pretty easily after warming the epoxy in my spray booth for about 4 hours at 80-85 degrees. I just set the cans on the top shelf and turned up the heat this morning.   

I did try Max's  "Stab" method on the new can after cutting a 1/4" off the tip of the tube First....It did work, but it was kinda of a mess to clean off the tube. The rest of them i clipped the tube tip too, but just used a fiberglass scrap to put it into the tube. After warming it, it was easily pushed into the tube without a lot of mess.  Whole thing probably took 15 minutes to fill 4 tubes....

I'll let you know how i like using the caulking gun when mixing. I'm going to go try it out now.    Kirk

[Mad Max]

Nice job

[Shredd]

  Shweeeet...  Hope it works well for yah...

[Crooked Stic]

Hmmm maybe send this idea to Smooth on 

[Kirkll]

I had already opened these cans of EA 40 that I used to fill the tubes, but hadn’t used too much from them. They say these tubes take 11 ounces. But I think they actually take more than that if you fill them to the brim like I did.

I ended up scraping the cans clean to do my last limb lay up yesterday. So I didn’t use the tubes yet. I’m going to try it this morning after the shop temp has cooled down. This will be a good test to see how well it works in 50 degree temp. They didn’t send any caps for the tip on these tubes I bought, so I just used masking tape to seal the tip much like I do on silicone caulking.

I’ll let ya know what I think about it.     Kirk

[Kirkll]

OK....Here ya go.... This works pretty slick with the caulking guns....

I just uploaded this video from my phone. So it may take a minute to load up.   Kirk

https://photos.app.goo.gl/GRDTUCXRQ7exFuxG9

[mmattockx]

Thanks for the video, that looked very slick. How warm is your shop?


Mark

[Mad Max]

That's slick Kirk 

[Mark R]

I've got to ask Kirk, in the video what kind of bow are you making.

[Mad Max]

I've got to ask Kirk, in the video what kind of bow are you making.

Look on his website at the Bigfoot "Bare" Hybird limbs

[Kirkll]

The shop was running about 60-65 degrees when I laid the limbs up. Overnight low temp was about 55 degrees and both A & B parts flowed pretty easily in the caulking gun. 

We have had an unusually cool Spring  going this year. A lot of rain too.
I think we have only had one day reach 80 degrees so far, and very few over 70 in the last couple months. It’s just now starting to get in the low 70’s a bit, but still getting hammered by one rain storm after another…. Very wet year… we just got our vegetable garden planted last week, and typically have everything planted In April.

The limb I laid up in the video was a Bare SS recurve limb. Here are some that I finished last week on an “A” mag riser. Look at the string angle on this 60” bow. I’ve had a request to do a DFC chart on this bow, so I may or may not have some data available in the near future.

I do not have time to do a lot of testing anymore.
There is no need to anyway. My limb designs have proven to be high in performance. But I do offer a service to do the DFC chart and run a bow through the chronograph, and record all the data for $100.   Kirk

https://photos.app.goo.gl/5BwFBH4ZfVi91n8J9

[Buggs]

Those caulking tubes look like they work well. Looks like they saved you a few seconds over scooping it out of the can

[Kirkll]

It’s not the few seconds savings scooping out of the can that I’m interested in. It’s the fact that my epoxy isn’t exposed to the air until it goes in the cup that I like the most. That , and I can control the amount I’m mixing using the pump handle and not just eye balling it, or measuring by weight, or measuring cups. I like it!

With the amount I used in the video, it was perfect for a limb lay up. I’ll bet I didn’t have much more than a table spoon left in the cup. That was only a 5 piece lay up. (Light draw weight) When doing veneers (7 lam) , or a heavier draw weight using 6 lams I’d be scraping the cup clean. Probably use a bit more on veneers.

For the little cost for the tubes, and easy filling. I strongly recommend this application. Especially for guys not building a lot of bows. I think keeping it in these caulking tubes will extend the shelf life considerably , vs a half can sitting for months on end.    I go through about 3- 4.5 gallons a year myself depending on how busy I am.    .02 cents worth.     Kirk

[mmattockx]

The shop was running about 60-65 degrees when I laid the limbs up. Overnight low temp was about 55 degrees and both A & B parts flowed pretty easily in the caulking gun. 

That is good news as my glue up space is generally pretty cool. It looked like you had no trouble getting it to flow easily out of the tubes. I appreciate the tip on the colour changing when mixed enough, I've not used EA-40 before and that is a good thing to know ahead of time.

The limb I laid up in the video was a Bare SS recurve limb. Here are some that I finished last week on an “A” mag riser. Look at the string angle on this 60” bow.

That is a sweet bend and amazing string angle. 28" draw? What does that look like unstrung?

Those caulking tubes look like they work well. Looks like they saved you a few seconds over scooping it out of the can

For me it's not the time. It looks like a much neater, less messy way to handle the epoxy and not ever get the two parts accidentally mixed where you don't want them. Minimizing the exposure to air is a bonus, as I don't make many bows and shelf life can be an issue.


Mark