10' Turbine Stator Cast - Now what?

[arwenvaughan]

Ok, guys I need a bit of advice here. I read most of the forum discussions about casting stators, but I am still not quite sure what to do in my particular case. Working on this 10 foot other power wind turbine is the first time I have worked with any type of resin.

Anyway, I cast the 2 rotors a couple of weeks ago and they turned out great (see picture), but it was a bit touch and go. After 3 or 4 hours the resin had not started to harden at all. So, perhaps I was being impatient or stupid but I ended up putting a space heater near them and they fired off really well. I measured the temperature near the rotors and it was about 100 degrees. So I took the heater off after a few hours that night and they were totally finished hardening in the morning.

Now I am wondering what to do about my stator. I just cast it a couple of hours ago and just like before, it has not started to "fire off" at all! Am I being impatient or do I need to apply some heat to the stator now as well? I am concerned that it will crack or shrink if I apply heat like before but worry it will never cure if I do nothing. What should I do?

I used...

• 1.5 Quarts Vinyl Ester Resin
  
• 0.5 Quarts ATH and Fiberglass as fill (mostly ATH with a touch of fiber)
  
• 0.25 ounce of Hardener
  
  

It was about 85 degrees when it was cast.

[Blutoy]

My bet is that with no heat, there will be a nice new ( hard ) stator waiting for you in the morning... and it's not even Christmas.

[Flux]

No problem with heating the stator to cure the resin. If you really got those magnet rotors to 100 deg I hope it was Fahrenheit. If it was C you were dangerously close to loosing magnetism.

Flux

[dlenox]

Slow cure is not a bad thing - keeps heat down!

If you want to speed it up put in more catalyst, should be around 2%, but this varies not only with heat but humidity as well.

Ultimately as long as it does finally 'go off' and cure - that's a good thing.

Dan Lenox

[arwenvaughan]

Flux,

Thanks for your replies guys. Flux, are you saying that it is fine to heat the stator a bit to cure the resin?

I checked the mold this morning and it is now a little tacky but still liquid...still runs. It has been roughly 14 hours since I poured it and just thought it would harden much more quickly than this. I guess the garage is going to get nice and hot today from the heat of the sun, so perhaps that will cause it to fire off.

And yes I was talking about 100 degrees fahrenheit on the rotors :0) That should be alright...right?!!??

[Blutoy]

How can it be a little tacky but still liquid. Hate hearing this because I just ordered this brand of material. I have always use vin. est. from Fibre Glast Developments Corp., payed twice as much, but love the product. Please let me know what happens with your stator.

[arwenvaughan]

Well the resin finally started to fire off today as the garage got hot from the heat of the day. It was 95 degrees this afternoon in the garage and the resin was definitely hardening up. The pools of resin that dripped to the floor where hard as rocks. I left a half inch or so of resin in the milk container that I used for pouring and it is quite a bit harder than jello, but still a bit runny in places. I am going to wait at least until this is totally hard before opening the mold. A day or two maybe.

For the record I used just a little over 1/2% of catalyst for this casting. I think it would be ok to add a bit more so it doesn't take quite so long. But, I guess this means there shouldn't be any cracking or shrinking.

Thanks for the advice you guys.

[arwenvaughan]

Is this a pretty typical scenario when pouring resin? Do most of you guys put in more catalyst than this? I need a couple data points guys. Would it ever have fired off if it did not get so hot in my garage? This resin crap is like some kind of black art...

[David HK]

This web site will offer you a table for catalyst to resin ratios.

http://www.cfsnet.co.uk/acatalog/methods_mixingcatalyst.html

Ambient heat does have a great effect on the curing process. The hotter the climate the quicker it sets especially if one has overdone the catalyst.

By a cheap hypordermic syringe and needle and you can be more precise in adding catalyst/

The next rule is be patient.

David HK

[arwenvaughan]

I just meant that it is more viscous but still runs slowly if you tilt it.  I am new to working with resin so I am over analyzing this whole process. I think this brand is probably great actually...I am just not very experienced and I am putting in half the recommended amount of resin so it fires off really really slowly I guess. I just didn't think it would harden this slowly. I guess patience is a virtue.

Also, it is weird how resin seems to harden on the inside first while the outside is still liquid. I popped a half inch thick block of resin out of the milk jug and it was totally hard except the top couple of millimeters was totally liquid. Anyway, it is looking good now. I'll let you know how it looks in a day or two.

Cheers!

[dlenox]

This does not sound 'normal', I would at least double (if not triple) the amount of catalyst that you use.

If mixed in the proper quantities the resin actually produces heat, the amount depends on the %.

To me a slow cure means 2-3 hrs before it can be handled.

Dan Lenox

[Airstream]

A slow cure keeps uneven shrinkage from cleaving canyon cracks in the resin and exposing your steel and magnets to moisture so if it takes days all the better for the long term life of the rotor. If you can stand a little dust, dirt and bugs on the surface place the rotors outdoors in direct sunshine and let the even heating and UV light energize the catalyst, something about the full spectrum of sunshine excites the right molecular processes in many many resins.

[arwenvaughan]

Thanks for the suggestion! The a couple hours in the sun and the mold (and my tester) was totally cured. I guess UV does work...well my temperature gauge registered 107  degrees on the mold too. Anyway, it cured up nicely even with so little hardener (about 1/2 %) but it did take some heat. I don't think it would have ever cured without it.

Unfortunately, there were a number of air bubbles but they all look like they are cosmetic and fixable. Any advice for fixing bubbles? I was going to use a bit of tape around the edges and pour more vinyl ester resin into the hollow spots...maybe put something flat on top to smooth it out.

The mold was destroyed as well. The bottom of the mold actually pulled up a bit of the plywood. I think making a plastic mold is a really good idea. I would not do wood again...the stator did not fall right out. And this was after 4 layers of linseed oil and 3 very thick layers of mold release wax.

Anyway, here are a few pictures...

 

[Captain]

Well the patience paid off. I have had similar problems.   Due to the mess and nasty smells I usually pour outside or in a well ventilated area that does not have a heat source.  Temperature has always been a large factor.  During the summer months stators were completely catalyzed within 2 hours.   Using the same quantity of hardener in the winter months when the temps are much colder the stator would often not be hard 16 hours later and if the mold does not completely seal more bubbles would be present.   By bringing the mold inside and setting it next to the wood stove was all that was necessary to have the vinyl-ester harden.  I often used tape and a bit more vin.est. to patch bubbles.  or if possible keep it in the mold and pour some vin. est. in the trouble bubble areas and replace the top.  If you are using tape on the edges just be sure to not increase the thickness of the stator where bubbles occur as having a nice flat surface for setting the air gap is important.