Resin to hardener - no sense

[Dave B]

 I used Bondo resin for my last stator and thought at the time the ratio of hardener to resin indicated on the gallon can was quite high. This casting took off very rapidly (no additives other than glass mat) almost before I could clamp it down. I saved it and it turned out fine but now that I am about to cast another stator I wish I could be reasonably confident of a ratio of hardener to resin that would still be certain to set up properly but not too fast.

 Here is what the gallon can indicates as a mix ratio : Mix 7 drops of hardener to 1 Tablespoon of resin or 14 drops of hardener to 1 ounce of resin. Here's where this makes no sense : there are 2 tubes of hardener included with 1 gallon of resin. The gallon can indicates this as a total of 1.48 fluid ounces of hardener or 44 ml of hardener. Each tube contains 22 ml of hardener. Well, doing the math comes up well short of including enough hardener for 1 gallon of resin. I honestly think they have the ratio printed incorrectly and that with the proper mix ratio there is enough hardener included for 1 gallon of resin.

 If any of you old school stator casters out there could help me with this mix ratio of (Bondo Resin and liquid hardener) I sure would appreciate it. (this is the liquid resin and liquid hardener not the body filler and paste type hardener) Thank you,  Dave B. 

[silentblue1987]

Sadly the mix ratio is correct... what you have my friend is what I like to call the "3 drop" resin cause each drop cuts your working time in half lol. Every hardware store I've gone to has this stuff, and its cheap, you can probably figure out why. Just reading the label before buying was enough to set it back on the shelf. The few videos I have seen using it they added about 3-5 drops for every cup or so and mixed in batches. The only protection you might be able to get from large batches is mix it in a cold room (40 degrees or less), then move it to regular temps after you seal the cast.. Just remember, the larger the batch the FASTER it cures.

I'm a cheater though and bought resin from a boat repair shop which had a large selection of catalysts to go with each resin. I got the super slow curing stuff which gives almost 2 hours of working time, maybe 1 hour if I mix the entire gallon.

It's not cheap though, the 1 gal kit with resin, catalyst, mixing cups, hand pumps that measure proportions for you, and full instructions on everything, cost 180$.
2 hours of room to mess up though, well worth it in my opinion.

[electrondady1]

i use a kitchen scale to weigh the amount of resin.
i use about one third the number of drops per ml. they call for .
stir stir stir.

[Dave B]

Just an update on the mix. I used approx. 1/3 the hardener indicated for several seperate pours of 24 oz. It worked out to be 5 drops hardener per ounce of resin. It still set up quite fast with a working time of maybe 20 minutes including mixing from when the hardener was added for each pour. This at approx 70 deg. and fairly high humidity. Thanks for the tip on the hardener mix. This stator will be flying very soon (tweaking the low - mid wind speed performance.)  Dave B.

i use a kitchen scale to weigh the amount of resin.
i use about one third the number of drops per ml. they call for .
stir stir stir.

[ChrisOlson]

If any of you old school stator casters out there could help me with this mix ratio of (Bondo Resin and liquid hardener) I sure would appreciate it. (this is the liquid resin and liquid hardener not the body filler and paste type hardener)

Dave,

Those cans are not one gallon.  It is 118 ounces.  I use that brand all the time and have no problems with it.  I use 3 ml / 10 ounces of resin during colder weather, and drop it back to 2 ml / 10 ounces during warmer weather.  20 drops is one ml.  So basically, in warm weather I am using 2 drops per ounce and in colder weather I use 3 drops per ounce.

Do not pay any attention to the instructions on the can.  Those are for quick layup of fiberglass repairs were the resin is used in very thin coats to saturate glass.  If you use that ratio you will have a runaway reaction.
--
Chris

[Dave B]

Chris,

  I read this as you using 6 drops per ounce in colder temps and 4 drops per ounce in warmer temps. Anyway, so I hit the middle at 5 dops per ounce. It worked well but there is not much working time, nothing like before though when it nearly set before I got the lid on. Just finished drilling it and will paint it tomorrow. Thanks again for the tip on casting bolt connectors like you do, this really looks professional.  Dave B.

If any of you old school stator casters out there could help me with this mix ratio of (Bondo Resin and liquid hardener) I sure would appreciate it. (this is the liquid resin and liquid hardener not the body filler and paste type hardener)

Dave,

Those cans are not one gallon.  It is 118 ounces.  I use that brand all the time and have no problems with it.  I use 3 ml / 10 ounces of resin during colder weather, and drop it back to 2 ml / 10 ounces during warmer weather.  20 drops is one ml.  So basically, in warm weather I am using 2 drops per ounce and in colder weather I use 3 drops per ounce.

Do not pay any attention to the instructions on the can.  Those are for quick layup of fiberglass repairs were the resin is used in very thin coats to saturate glass.  If you use that ratio you will have a runaway reaction.
--
Chris

[ChrisOlson]

  I read this as you using 6 drops per ounce in colder temps and 4 drops per ounce in warmer temps. Anyway, so I hit the middle at 5 dops per ounce.

Oops.  Yes, that was a brain fart.  I have never actually mixed it by the ounce.  I always do 10 ounces at a time.  I measure the resin out with a bottle that has graduations on it and dump it into a cut-off empty milk jug.  I use a little syringe to suck the hardener out of the tube and squirt it into the pot, then mix it up good.  I have never had it set up as fast as you describe - there is usually a good half hour before it starts to get a little thick.  That gives me all the time I need to cram all the glass into it that will fit.

I used to worry about getting "perfect" stators out of the mold and fill it up with liquid until it oozes all over.  But I no longer worry about that.  I worry about getting enough glass in them, and getting the cover on and smashed to the proper thickness before it starts to set up.  Getting the "perfect" stator does not do anything for it mechanically.  The glass is what will transfer heat in it to the outside.  The plastic is pretty much worthless.

When when it comes out I touch up any imperfections using regular old body filler to get the "perfect" stator.  But that's just cosmetic.

For a long time now I've had this idea of machining a ring made of UHMW that will hold the stator coils and leave them exposed to the air instead of sealing them in insulation.    1/2" UHMW is mechanically stronger than fiberglass and I believe it would make a better mount for the coils in the air gap.  Sometime this winter when have more time and do the bulk of my turbine building, I intend to try that.
--
Chris