ardrhi

Hello Everyone,

I have never used West Systems before. (Great at wetting out by the way....) Anyway, I ordered their 209 hardener, with the anticipation that it would give me plenty of working time. (I had no idea....) The problem is this: I am having some concern over a spar that I have laminated with 209 mixed West Systems Epoxy. The temperature in our house is around 68 degrees. The issue I am having, is that 72 hours later, the epoxy is still gummy. When I say gummy, I mean that it resembles gumdrop gummy to jolly rancher candy hard. Is this normal? I mixed the resin at a 3.5 to 1 WEIGHT ratio, using a gram scale. (I was VERY precise on my measurements.) Additionally, I have hit the spar several times with a heat gun. (Lightly enough to avoid foaming and bubbling the resin.)
Needless to say, I ordered the 206 hardener. However, the CF/aircraft ply spar has about 16 hours of work in it, and cost me some 200 dollars. I would rather not loose it.

Any help would be greatly appreciated. Am I worrying prematurely? Maybe this is normal for 209. Does this hardener really take this long to set up at 68 degrees?

Regards,

Chris Berrett

soarrich

My Feedback: (98)

No, you've got a problem.[:@]

KC36330

for 209, the cure time is 4-9 days.

EDIT: the MINIMUM temp is 70 degree as well. it's intended for use in high humidity and/or high temps, not in the house at 68

soarrich

My Feedback: (98)

Pot life 40-50 minuntes, thin flim working time 3-4 hours, cure 20-24 hours at 70*, 68* isn't going to slow it down much.

KC36330

Word for word from the West System User Manual:

a solid state is no longer in liquid, elsewhere in the manual it states gel is a solid state.
i've used it and it stays tacky for several days even at above room temps.

EDIT: 209 is also a 3-1 ratio, not 5-1..........

soarrich

My Feedback: (98)

I've used it too, it wasn't gummy after two days. I hope it cures, but I think there may be a problem. Maybe an electric blanket would help.

ardrhi

You know when you have that, "Oh....Duh" moment? (Be honest....we all have them....well ....most of us.....except my wife.....) Soarrich just made me have one of those. Here I am, placing the half cured spar in my hot car, hoping to elevate the temp. I will try your much easier (And intelligent) method.

Chris

soarrich

My Feedback: (98)

You mean one of these?[X(] I installed the engine upside down.

sunnybreeze-inactive

Chris,
I've been using West for 27 years and have made all the mistakes. It's one of two things. You did not mix the the two parts long enough or the resin or hardner has expired past it's shelf life. I would guess it's the first. The rule is mix until you are sure it's mixed and then mix for 2 minutes more. I have experanced the gummy thing in the past and it was simply inproper mixing. Scrape all the epoxy off and wipe with acetone. Then do it all over with a new batch. Good luck. If you can get off the cloth also go for it.
Steve

ardrhi

Soarrich: Yes sir! One of those......

Sunny: I believe you are right, I merely mixed for 2-3 minutes. (Not understanding how much time I had....) Right now I am trying two heating pads. I am hoping that this may cause the epoxy to set up after several days of treatment. Unfortunately, removing the laminated carbon fiber socking from the composite spar is not really an option. If the heat doesn't fully do it, I am going to try to paint on a VERY thin layer of the curing agent, then heat again. Do you see any risks with this?

Regards,

Chris

Ed Smith

That will do nothing for you. The hardener and resin have to be mixed at the same time.

Ed S

sunnybreeze-inactive

Chris,
Ed is right. It will not work. You need to get as much crap epoxy off and I would suggest to mix a new batch and go over it. It should make it kick off and your back in business.
Good luck

ardrhi

Ed and Sunny,

Gotcha. Good thing is, I didn't apply it in a very thick layer. It was just enough to wick in to the weave, and adhere it to the spar structure. (I wanted to leave plenty of porous surface area for the adhesive to lock the spar in to the foam wing core.) Hopefully I can thin a new batch by warming it with a hair dryer, (Don't want to use the heat gun, as I would like a more subtle warming of the mixture.) and apply a VERY thin layer. If all else fails, back to square one. I am NOT going to put a ultra heavy spar in that model. The whole purpose of this CF laminated spar, was to make something incredibly strong and _light_.
On the positive side, I _think_ I am getting a _very_ slow, yet steady hardening of the resin. (Using the heating pad method.) Time will tell. I will give it the weekend, and check back on it.


Chris

soarrich

My Feedback: (98)

sunnybreeze may have hit it on the head.

It may be time to cut you losses and start over. If you're using CF looking for super-strong, super-light spar, you're probably looking to to put it in something of value. Ask yourself this, if it fails would you rather have spent $200 more and got a first class spar, or are you happy you saved $200 on the plane that crashed?

EHFAI

A good epoxy mixing trick is to hold the container while mixing - as the components reach a good mix they will endotherm (absorb heat), the container will cool to the touch. Mix a bit longer and you've got it.

ardrhi

EHFAI: I wasn't aware of that. I will have to pay attention next time around. [8D]

Sunny: I agree. However, being as it is such a thin layer, West Systems believes that it may just take a longer period to cure. (As well as needing elevated heat) If this is the case, I am ok with using the spar. As you said though, I think should this not occur, I will just scrap the spar and start over. No sense in laminating good resin on top of bad.

Chris

sunnybreeze-inactive

Chris,
I went back to your first post and it said you mixed 3.5 to 1. That is the wrong mix ratio. 5 to 1 is the proper ratio. That is you problem
steve

soarrich

My Feedback: (98)

209 Extra Slow Hardener

209 Extra Slow Hardener is formulated for use with WEST SYSTEM Brand 105 Resin for general coating and bonding applications in extremely warm and/or humid conditions or when extended working time is desired at room temperature. Provides approximately twice the working time of 206 Slow Hardener. Forms a clear, amber-colored solid with good physical properties and moisture resistance for bonding and coating applications. Not intended for clear coating.

Mix Ratio, Resin:Hardener
Pot life at 72°F (22°C)
at 95°F (35°C)
Cure to a solid state at 72°F (22°C)
at 95°F (35°C)
Cure to maximum strength at 72°F
Minimum recommended temperature
Pumps 3:1 by volume (3.5:1 by weight)*
40 to 50 minutes
15 to 20 minutes
20 to 24 hours
6 to 8 hours
4 to 9 days
70°F (21°C)
300, 306-23 or 309-3

* Mix Ratios

The mix ratios above refer to the ratio of resin to hardener if you are metering by weight or volume. When using 300 Mini Pumps, pump one stroke of resin for every one stroke of hardener. Refer to the instructions included with the 300 Mini Pumps before using.

ardrhi

Hi Sunny,

I believe 206 and 205 are 5:1 by weight and volume. Where as 209 is 3:1 by volume, and 3.5 by weight as indicated above. However, I have good news. After one week with the heat pad, the spar is _almost_ hard as a rock. I am going to keep at it for another week. I think I may have gotten somewhat lucky, in my first negative encounter with the ever fickel resin known as ......"epoxy".



Chris

jim52519

My Feedback: (3)

Chris,
I have been using West System epoxy for about 20 years. I use it on my model airplanes and also built a 17' cedar strip canoe , which was covered inside and out with 6 OZ glass cloth and West system epoxy. I think you should set aside the 209 hardner and get some 205 hardner. In our model building we use small batches. Small batches have a longer pot life. At 68 degrees 205 will cure reliably over night and you will have plenty of working time.
Ditch the 209 and get some 205. The 205 works great and gives you all the working time you need.

Jim

dsquire

Hi Chris

I am new on the forum here and just read this thread. You indicated in your last post that you thought it was finally going to cure. Now that it is a month later can you confirm that it has finally cured. Just info that I would like to have in case I ever find myself in a similar situation.

Thanks

Don